FRACTURE TOUGHNESS

AND RELATED CHARACTERISTICS

OF THE CRYOGENIC NICKEL STEELS

A PRACTICAL GUIDE TO THE USE OF NICKEL-CONTAINING ALLOYS

NO 1232

Distributed byNICKEL

INSTITUTEProduced byINCO

FRACTURE TOUGHNESS AND RELATED CHARACTERISTICS OF THE CRYOGENIC NICKEL STEELS

A PRACTICAL GUIDE TO THE USE OF NICKEL-CONTAINING ALLOYSNO 1232

Originally, this handbook was published in 1983 by INCO, The International Nickel Company Inc. Today this company is part of Vale S.A.The Nickel Institute republished the handbook in 2021. Despite the age of this publication the information herein is considered to be generally valid.Material presented in the handbook has been prepared for the general information of the reader and should not be used or relied on for specific applications without first securing competent advice.The Nickel Institute, INCO, their members, staff and consultants do not represent or warrant its suitability for any general or specific use and assume no liability or responsibility of any kind in connection with the information herein.

Nickel Institute

communications@nickelinstitute.orgwww.nickelinstitute.org

Fracture Toughness and Related Characteristics of the Cryogenic Nickel Steels

by A. W. Pense and R. D. Stout

CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Historical Development . . . . . . . . . . . . . . . . . . . . . . 2 Effects of Nickel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Recent Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . 2

Metallurgical Characteristics . . . . . . . . . . . . . . 3 Transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Practical Heat Treatments. . . . . . . . . . . . . . . . . . . . 5 Effects of Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Evaluation Methods and Criteria . . . . . . . . . . . 6 Properties of Interest . . . . . . . . . . . . . . . . . . . . . . . . 6 Static Tension Tests . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Fracture Toughness Tests . . . . . . . . . . . . . . . . . . . . 6 The Charpy Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 The Drop-Weight Test........................ 7 Linear Elastic Fracture Toughness Tests . . . . . . 7 Crack-Opening Displacement Tests . . . . . . . . . . . 9 R-Curve Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 J Integral Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 The Dynamic Tear Test. . . . . . . . . . . . . . . . . . . . . . . 10 Fatigue Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Significant Criteria for Cryogenic Materials Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

The Low-Nickel Steels . . . . . . . . . . . . . . . . . . . . 12

Specifications .............. , . . . . . . . . . . . . . . . . 12 Tensile Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Effect of Temperature . . . . . . . . . . . . . . . . . . 12 Effect of Heat Treatment and Plate Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Effect of Cold Deformation and Aging.. . . . 14 Effect of Welding . . . . . . . . . . . . . . . . . . . . . . 15

Notch Toughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Charpy Test Results . . . . . . . . . . . . . . . . . . . . 15 Drop-Weight Test Results . . . . . . . . . . . . . . . 15 Fracture Toughness Test Results . . . . . . . . . 17 Effect of Strain Aging . . . . . . . . . . . . . . . . . . . 17 Effect of Welding . . . . . . . . . . . . . . . . . . . . . . 18

Fatigue Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Summary .................................... 19

The Higher Nickel Steels . . . . . . . . . . . . . . . . . . 19 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Tensile Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Effect of Heat Treatment and Thickness. . . 20 Effect of Temperature . . . . . . . . . . . . . . . . . . 23 Effect of Cold Deformation and Aging . . . . . 24 Effect of Welding . . . . . . . . . . . . . . . . . . . . . . 24

Notch and Fracture Toughness ........ ·........ 25 Charpy Test Results . . . . . . . . . . . . . . . . . . . . 25 Drop-Weight and Dynamic Tear Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Fracture Toughness Test Results . . . . . . . . . 27 Dynamic Fracture Toughness . . . . . . . . . . . . 31 Effect of Strain Aging . . . . . . . . . . . . . . . . . . . 32 Effect of Welding . . . . . . . . . . . . . . . . . . . . . . 32

Fatigue Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Summary .................................... 34

Assessment of the Cryogenic Nickel Steels . . 35 Rationale of the Assessment. . . . . . . . . . . . . . . . . . . 35

Tensile Properties . . . . . . . . . . . . . . . . . . . . . . 35 Fatigue Properties . . . . . . . . . . . . . . . . . . . . . . 35 Notch Toughness . . . . . . . . . . . . . . . . . . . . . . 35 Fracture Toughness . . . . . . . . . . . . . . . . . . . . 35

Survey of the Fracture Toughness Data . . . . . . . . 35 Flaw Size-Allowable Stress Relations. . . . . . . . . 37

The 9% Nickel Steels .................. . A645 Steel ........................... . A203 Steels ........................... .

37 37 37

Summary .................................... 38

Suggested Research .... ' .................. . 38

Acknowledgments . . . . . . . . . . . . • . . . . . . . . . . . 39

References . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . 39

Table A-Conversion Factors for Property Values . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Cryogenic Nickel Steels 1

Abstract. A large volume of data concerning the 2¼, 31h, 5 and 9% nickel steels, corresponding to ASTM specifications A203 Grades A and D, A353, A553 Type I, and A645, has been collected from the open literature and private sources. The mechanical-property data collected include tensile­test properties at ambient and cryogenic temperatures, notch toughness, fracture toughness and fatigue strength. A brief description of each of the testing methods used and their significance to cryogenic service are included. Tables and figures summarizing the data are presented. The strengths and toughnesses required by the respective ASTM steel specifications and ASTM specification A593 are normally met or exceeded by the steels. For the lower nickel steels, gains in toughness can be obtained by quenching and tempering rather than normalizing.

The effects of fabrication operations such as cold work, heat treatment and welding on the mechanical properties are considered. In general the effects of cold work and welding on the tensile properties of the cryogenic nickel steels are small. In the case of 21h and 31h nickel steels, the notch toughness is adversely affected by cold forming and aging but little influenced by welding operations. Subse­quent thermal stress-relief treatments will restore the orig­inal toughness. Conversely, the notch and fracture tough­ness of the higher nickel steels are relatively insensitive to cold forming, but are reduced in weld heat-affected zones produced by high heat inputs. The fatigue properties of the cryogenic steels appear to fit the typical scatter band ob­tained for structural steels, and cryogenic crack-growth rates are not significantly different from those at room temperature.

An attempt has been made to evaluate the critical flaw sizes at design-stress levels for the steels as a function of temperature and stress concentration. For the lower nickel steels, it was concluded that A203 Grade A steel should be limited to service temperatures above -75° F (-59° C) and A203 Grade D should be limited to service temperatures above - 110° F (-73° C). When quenched and tempered, the service temperature for these steels can be reduced by about 25° F (14° C). For the higher nickel steels, leak-be­fore-break behavior may be predicted for most expected cryogenic applications. For example, the A353 and A553 Type I steels will meet this criterion at -320° F in 1.5 in. (38 mm) plate for a design stress of 25 ksi (172 MPa) and a stress concentration of K 1 = 2. The A645 steel will meet these same requirements at a service temperature of -275° F (-170° C).

Introduction

Historical Development

The benefits of nickel as an alloying element in low-carbon steel to enhance low-temperature notch toughness have been recognized since the turn of the century. 1 The use of low temperatures for processing and handling materials such as petroleum products and liquified gases has increased markedly in the past 25 y~ars, and the cryogenic field (generally de­fined as temperature below -150° F or -100° C) has spurred interest in the capabilities of the nickel steels.

An early systematic study was conducted by Serge­son2 on the low-temperature properties of 2, 3½, and 5% nickel steels. By 1936, the 2¼% Ni steel was standardized by ASTM as A203 Grade A for use as a

A. W. Pense is Professor of Metallurgy and R. D. Stout is Dean of the Graduate School, Lehigh University, Bethlehem. Pa.

Publication of this paper was sponsonod hy the Pressure Vessel Re­se&rch Committee of the Welding Research Council.

constructional steel in applications to -50° F (-45° C). The 31h% Ni steel was adopted later as A203 Grade D for temperatures down to -150° F (- 100° C).In 1942 the International Nickel Company devel­oped a 9% Ni steel3 with useful notch toughness down to liquid-nitrogen temperatures, and in 1960 "Opera­tion Cryogenics" 4 · served as a public demonstration that this steel provided a tough welded pressure ves­sel at -320° F (-196° C) without the need for post­weld heat treatment. Since then, investigations of cryogenic nickel steels have been intensified, most re­cently in connection with the storage and transport­ing of liquified natural gas.

Effects of Nickel The ability of nickel to improve the low-tempera­

ture properties of low-carbon steels has been associ­ated with several observed effects. Essentially these effects involve the ferrite grain size, carbide distribu­tion, generation of dislocations, and with higher Ni content, the retention of austenite.

Since ferrite is the predominant phase in low-car­bon steel, its grain size has an important effect on the notch toughness of the steel. Nickel has been found 5

to exert a refining effect on the ferrite grain size. By its hardenability effect, nickel suppresses proeutec­toid ferrite and favors bainitic and mattensitic struc­tures of higher notch toughness. Also in solid solu­tion, nickel is reported 6 to facilitate dislocation gen­eration at low temperatures and thus lower flow stresses relative to the cohesive strength level with resultant gain in toughness. At higher nickel levels, the transformation temperature range is lowered and considerable retained austenite may be present to en­hance notch toughness.

Recent Trends Design requirements of recent applications impose

more rigorous levels of performance of cryogenic steels both in fracture toughness and in fatigue resis­tance. These are being met by improved impurity control, fabrication procedures and inspection, and techniques of heat treatment. In addition, modifica­tions of the basic nickel-steel compositions have been proposed, such as the addition of manganese, rare earths, and microalloys.

Purpose and Scope

Purpose

This report is intended to summarize the available information published in the last 15 years about the mechanical properties of steels containing 2¼ to 9% Ni designed for low-temperature and cryogenic appli­cations. Further, this information is evaluated criti­cally to put a current view of the range of usefulness of these steels at the disposal of practitioners in the field.

The mechanical properties considered in this re­port include static strength, notch toughness, frac­ture toughness, and fatigue strength as affected by

2 WRC Bul/Ptin 205

composition, thickness, heat treatment, and fabrica­tion operations such as cold forming and welding. Special emphasis is put upon the fracture toughness characteristics of the steels, since it is this property that determines the limitations of design stresses and of temperatures of service more than any other. Reli­able information is essential for the safe application of the steels at cryogenic temperatures.

Scope The succeeding sections of the report encompass

the following material: 1. The nickel steels considered: ASTM, A202

Grade A (2¼% Ni),. A203 Grade D (31h% Ni), A645 (5.5% Ni, 0.25 Mo), A353, and A553 Grades A and B (9%Ni).

2. The physical metallurgy of the nickel steels rel­ative to their microstructures and resulting low-tem­perature properties. The effects of composition and heat treatments on microstructure.

3. The effects of processing, including melting practice, cold forming, and welding on microstructure and properties. ·

4. The testing methods and performanc;e criteria used to evaluate the nickel steels, weld metals, and welded joints.

5. Presentation and critical analysis of the me­chanical property data in tables and charts. Relation of test properties to service limitations. Suggested re­search.

Metallurgical Characteristics

Transformations The effects of nickel as an alloying element in low­

carbon steels are more readily understood by exami­nation of the Fe-Ni binary equilibrium diagram. 7

Figure 1 shows the relevant portion of the diagram, from which it is evident that additions of nickel to iron progressively lower the transformation tempera­ture of gamma to alpha iron until it eventually is sup­pressed completely. The A-J temperature widens to a range of temperatures as nickel is increased, so that above 7% Ni the alloys do not become completely fer­ritic at any temperature. The presence of 0.10-0.15% carbon alters phase relationships primarily by the formation of carbides in those temperature-composi­tion domains where ferrite is a component phase. It is important to realize that the phase transformations become extremely sluggish at lower temperatures and thus equilibrium conditions are not ordinarily at­tained.

A more specific method of describing the behavior of the series of nickel steels is by way of isothermal (IT) or continuous cooling (CCT) transformation di­agrams. Representative diagrams for 2¼, 3½, 5, and 9% Ni steels are shown in Figs. 2 to 5. It is evident that the 2¼% Ni steel (A203A) behaves much as a low-carbon steel except for a moderate slowing of transformation reactions, i.e., some increase in har-

Fe-Ni Iron-Nickel Atomic Percentage Nickel

40 50 60 70 80 90

Nt-o.,------+--+--+--- L ---+---+---+--+----i

I

14001--,3-94-.--+---+--+--+--+--+--+---f-------ll----i

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Fe 10 20 30 40 50 60 70 80 90 Ni J. I. Goldstein Weight Percentage Nickel

Fig. 1- The iron-nickel equilibrium diagram

denability. The 3½% Ni steel (A203D) exhibits a low­ering of transformation temperatures and further slowing of reaction· rates. Neither of these low-Ni steels can be fully hardened in plate-gage thickness­es, as will be shown later. At 5% Ni plus ¼% Mo the transformations are noticeably altered. Martensite is formed at relatively slow cooling rates and complete ferrite-carbide formation needs extended exposure to 800-900° F (425-475° C). The 9% Ni steel falls into a separate category because of its tendency to retain some austenite at room temperature following the cooling in air from heat treatment temperatures of even thick plate sections.

The IT or CCT diagrams may be used to obtain a general picture of the metallurgical structures pro­duced by normalizing or quenching plates of various thicknesses in each of the grades of nickel steel. The cooling rates to be expected at the mid-thicknesses of various plate thicknesses have previously been deter­mined8 for both normalizing and spray-quenching treatments. Table 1 lists the rates for 1h, 1, 2, and 4-in. (13, 25, 51, and 102-mm) plates. When these rates are fitted to the diagrams, the microstructures that should form for each combination of steel composi­tion, plate thickness, and cooling method may be ap­proximated. Table 1 also contains the results of this analysis. The constituents are listed in each case in the order of predominance to be expected. Naturally, heat variations may cause considerable departures from the structures projected in Table 1.

It is evident from the table that A203 Grade A steel consists of ferrite-pearlite aggregates except for regions near the surface of quenched plates. The

Cryogenic Nickel Steels 3

IOO

700

100

l&J !so ffi 400

~ l&J I- :SOO

•Fr-r-r-r,..,,..--ri,.,,;...--"T'T'Tm11r-,r-r""..-,-,....,rnr--.-,.,,ma 111111 11111,.11111 111111 1111111 11111 - A ■ ,,., -

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-200 4001-1-1- ______ --<l-l-<,---I---I---I--I--I--I-I

-100 IOOl-l-l-_-+-_-l--l--l---<l-l-<,---l---l---l--1--1--I-I

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I

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I u

I

0.5 I 2 5 10 102 103 104 U 1 J 5 ■ 11• 11• -- •• 11• •• Time in Seconds

Fig. 2-The isothermal transformation diagram for 21/4 % nickel steel (estimated)

Fig. 3-The isothermal transformation diagram for 3 ½ % nickel steel

4

'"' 11 Ill 11 1111 11 1111 11 1111 11 11111

-IGO A

... - ... -- - - --- -- --- ·- -- --· ---llO

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1200 /

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-

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41

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U 1 2 I 1D •• •• -- •• •• •• U 1 2 5 ID 11• Tlll'll,SIC_,.

10• 10• ,..

Fig. 4-The isothermal transformation diagram for A645 steel Fig. 5- The isothermal transformation diagram for 9 % nickel steel

Table 1-Cooling Rates and Microstructures at Plate Midthickness of Normalized and Spray-Quenched Nickel Steels

ooling Rates for Normalized or Quenched Thickness, ° F/se Thickness ½in. (13mm) 1 in. (25 mm) 2 in. (51 mm) 4 in. (102 mm) Spray quench 60 (33° C) 20 (11 ° C) 7WC) 2.5(1.4°C) Normalize 2 (1 ° C) l(0.5°C) 0.5 (0.3° C) 0.25 (0.14° C)

Microstructures Produced in Ni-Steel Plates at Midthickness Steel Plate Treatment A203A A203D A645 A353-553 ½in. Norm. F&P F&P F,P,M M&B

S.Q. M,F,P M,F,P M (& F?) M (&A) 1 in. Norm. F&P F&P F&P M&B

S.Q. F, P, (M?) F,M,P M,F,P M (&A) 2 in. Norm. F&P F&P F&P M&B

S.Q. F&P F&P F,M,P M (&A) 4 in. Norm. F&P F&P F&P M&B

S.Q. F&P F&P F,P,M M&B

Note: F proeutectoid ferrite, P pearlite, M = martensite, B = bainite, A retained austenite.

WRC Bulletin 205

A203 Grade D steel behaves similarly except that a hardening effect is exerted slightly deeper into the plate. For practical purposes, both steels· can be con­sidered non-hardening and derive their properties from the characteristics of the ferrite-carbide micro­constituents. If the A645 Grade were used in the nor­malized condition, it too would consist essentially of ferrite and carbide aggregates. However, a special se­quence of heat treatments has been developed to pro­duce microstructures more effective in attaining de­sirable cryogenic properties, as will be described later. The 9% nickel grades develop martensite over the full range of cooling rates with at least traces of retained austenite and with bainite volumes increas­ing as the cooling rate is reduced. These microstruc­tures are modified by further heat treatment for ser­vice applications.

Practical Heat Treatments The specified heat treatment for the A203 grades is

normalizing, usually from 1650° F (900° C) for the 2¼% Ni steels and from 1600° F (870° C) for the 3½% Ni grade. Stress relieving is optional. It follows that the properties of these steels are' congruent with the properties of a fine-grained ferrite + pearlite aggre­gate. Nickel improves the notch toughness largely by its influence on the ferrite phase (fine grain size and dislocation generation). Quenching and tempering has been applied to these steels to produce finer ag­gregates of ferrite and carbide and raise both the strength and notch toughness.

A multiple-step heat treatment procedure has been developed 9 to optimize the low-temperature proper­ties of A645 steel. The steel is first water-quenched from 1600° F (870° C) to obtain martensite ( + ferrite in thicker plates). The steel is then "temperized" by heating to 1325-1400° F (720-760° C), resulting in partial reaustenitizing and, upon quenching, a char­acteristic interleaved pattern of acicular martensite and ferrite. Finally a "reversion anneal" at 1150-12250 F (620-665° C) produces 5-10% austenite, tempers the remaining martensite, and upon water quenching develops a ferrite-carbide-austenite struc­ture of maximum toughness. The small volume of au­stenite is thought to assist in raising notch toughness by acting as a sink for carbon and nitrogen that oth­erwise would be distributed in the ferrite as carbides and nitrides.

As A353 grade, the 9% Ni steel is given a double normalizing treatment and tempered. The first nor­malizing at 1650° F (900° C) produces martensite and bainite. The second normalizing at 1450° F (790° C) produces a fine-grained austenite that transforms to martensite and bainite. Tempering at 1050-1125° F (565-610° C) causes reversion to 10-15% austenite which is retained upon air or water cooling. It is this retained austenite which has been shown10 to bees­sential for high-notch toughness down to liquid-nitro­gen temperatures. Under the A553 specification, the 9% Ni steel is water-quenched from 1475° F (800° C)

and tempered at 1050-1125° F (565-610° C). A high­er yield strength results (85 ksi vs. 75 ksi) and Charpy-test impact values at -310° F (-196° C) are also greater than those of double_-normalized steel.

All these nickel steels are subject to a form of tem­per embrittlement if exposed · to temperatures be­tween 700 and 1000° F (370 and 540° C) for extended periods. 11 Excessive holding times during tempering of 9% Ni steel are also undesirable because of an un­stabilizing effect on the austenite that induces de­composition to fresh martensite upon cooling and lowers notch toughness.

Effects of Welding In the fabrication of structures for cryogenic appli­

cations by welding, a number of difficulties may be encountered. Stress-raisers may be introduced by im­proper design or by low-quality execution of the welding, producing undercut, lack of fusion, lack of penetration, porosity, or trapped inclusions. Cracking of the weld metal or of the base-metal heat-affected zone (HAZ) may be induced by hydrogen, sulfur, or other impurities or by excessive constraint upon the joint during welding. The mechanical properties of the weld metal or of the HAZ may not match those of the base metal. Any of these shortcomings may result in a product that does not meet the service require­ments.

The metallurgical aspects of welding the nickel cryogenic steels are primarily concerned with the avoidance of cracking in the welded joint and with the maintenance of acceptable properties in the weld metal and HAZ. In the past, hot cracking of nickel­containing weld metals was a recurring problem; now it is well understood that restriction of impurities, such as sulfur and phosphorous, to low levels (<0.01%) is essential to sound welds. Since the nickel steels have enough carbon and hardenability to be susceptible to hydrogen-induced cracking, they must be welded with low-hydrogen-potential processes. Preheating to 200-300° F (100-150° C) is helpful in avoiding hydrogen or restraint cracking.

The thermal cycle imposed on the base metal vici­nal to the weld disturbs the heat-treated microstruc­ture and raises a question whether the mechanical properties are locally impaired. Next to the fusion line, the metal is heated to peak temperatures caus­ing grain growth, and the cooling that follows, slow or fast depending on the heat input and the section thickness, induces transformation products that may differ from the 01;-iginal condition. Fortunately, in the nickel steels these changes are not generally serious when recommended welding procedures are followed. In particular, good practice calls for limiting the level of heat input and the use of multiple-pass weldil!g. At moderate heat inputs, dwell time at peak temper­atures is short, so that grain growth is restricted both in degree and in the volume of metal affected. The cooling rate is rapid enough to produce fine ferrite­carbide structures or martensite, depending on the

Cryogenic Nickel Steels 5

steel composition. The reheating cycles accompa­nying multiple-pass deposits partially refine the coarsened structure and temper hardened regions. Thus the properties of the HAZ may not be altered significantly by welding.

In the low-nickel steels (A203 grades), the HAZ will contain appreciable proeutectoid ferrite and· lit­tle or no martensite. If the carbon content is on the high side of the specificatio~, high hardness areas may be produced, however. In this case postweld heat treatment at 1100-1150° F (590-625° C) may be de­sirable to obtain a tempering effect.

In the 5% and 9% Ni steels, the HAZ will become essentially mattensitic, tempered in some parts by the multiple passes. At the low carbon level charac­teristic of these steels, the martensite retains a high degree of toughness and postweld heat treatment is not necessary.

Evaluation Methods and Criteria

Properties of Interest A perennial problem not yet entirely resolved is

that of deciding what mechanical properties are sig­nificant to the service conditions to be imposed on the steel, and at what level they should be specified in order to assure satisfactory service performance. For service below room temperatures, tests are com­monly specified to measure static tensile properties, notch toughness or fracture toughness, and fatigue resistance if cyclic loading is involved. If the test is to be informative, test conditions must be representa­tive of the anticipated service temperatures, stress pattern, loading rates and of the material section size, metallurgical condition, and variabiliti Some of these requirements are met by the specimen design and testing technique; others are met by multiple specimens subjected to controlled variations of tem­perature, loading, pretreatment, or sampling loca­tion.

In this section the intention is to describe briefly the testing methods used to measure the mechanical properties of interest in cryogenic steels, their capa­bilities and limitations, and the approaches that have been used to interpret test results.

Static Tension Tests The testing procedures and specimen dimensions

for static tension testing are so long established and clearly defined by specifications such as ASTM ES and A370 that they need not be reproduced here. For cryogenic steels it is relevant to obtain information on the tensile properties at temperatures expected in service. The yield and tensile strengths are used to limit design stresses if brittle fracture is not a con­trolling factor, while elongation and reduction of area are specified primarily to assure uniform steel quali­ty.

As will be evident in a following section, knowledge of the yield strength as a function of temperature and

of strain rate is helpful in the analysis of relations among toughness, critical flaw size, and stress limits. Strain measurements during testing _require more elaborate techniques if they are to be accurate under conditions of very low temperatures or of high strain rates. Useful techniques have been described else­where.12

Fracture Toughness Tests The problems associated with brittle fracture have

received massive attention with the result that the mechanisms and controlling factors have been expli­cated satisfactorily in general terms. What is still lacking is the ability to translate test results quanti­tatively to the prediction of the service performance of a particular structure subjected to particular ser­vice conditions. This situation applies especially to materials that behave in an elastic-plastic mode at locations in the structure involving stress concentra­tions (flaws, fillets, connections, etc.). The nickel cryogenic steels fall into this category. Since the goal of test specimen design is to approximate the most severe stress pattern and loading conditions that are anticipated in the service structure, the trend has been toward full-section specimens containing flaws with fatigue-sharpened roots and dynamic loading. For the low-nickel steels, at least, the determination of quantitative fracture-toughness values is probably less significant than the temperature range in which transition from high to low values takes place be­cause of the abruptness of the transition.

The Charpy Test (ASTM E23 and A370)

Despite the objections that have been leveled at the Charpy test because of its small size and inade­quate notch severity, it has persisted as the most commonly used test for notch toughness, mainly be­cause it is economical, convenient, and familiar to en­gineers.

The limitation of the standard V-notch Charpy test lies in the failure of the Charpy transition tem­perature range of a given steel to correlate exactly with the temperature below which a service structure of the same steel becomes unreliable in resisting brit­tle fracture. This shortcoming is shared more or less, however, by other notch-toughness tests. It can be used to estimate fracture toughness parameters of limited shear-energy absorption. Consequently the Charpy test is often used as a check of material quali­ty and uniformity after the toughness requirements of the application and the suitability of the type of steel have been established by other testing methods.

Attempts have been made to extend the utility of the Charpy test by enhancing the acuity of the notch, 13 by constraining plasticity at the specimen sides 14 and by instrumenting the machine 15 to pro­duce load-deflection data from the test. Both cold pressing and fatigue cracking have been investigated for sharpening the notch, with mixed success depend­ing on what was being sought. The effect of notch

6 WRC Bulletin 205

sharpening is most noticeable on the Charpy curve at the low end of the transition range, thus tending to produce a steeper transition curve and higher transi­tion temperatures as indexed by energy levels below one-half of the values on the shear plateau. Fracture toughness values have been estimated on the basis of energy or load-deflection curves obtained from fa­tigue-cracked instrumented Charpy tests.

At this stage in the development of fracture me­chanics based design, sole reliance is no longer placed on conventional Charpy values for assessing the suit­ability of materials for critical applications. The cryogenic nickel steels must therefore meet require­ments that are defined by more sophisticated tests, but it cannot be assumed that procedures are so firm­ly established that all uncertainties have been re­moved. The Charpy test is by no means defunct, and it will be used in conventional or modified form for some time to come especially for quality control.

The Drop-Weight Test (ASTM E208) If the Charpy test can be considered a crack-initia­

tion test since most of the energy absorption occurs up to the crack-growth stage, the drop-weight test is essentially a crack-propagation test in which a run­ning crack is imposed on the steel by the brittle hard­facing weld bead and the resistance of the steel to the propagation of the crack determines the go-no go result. With this basic difference in test conditions recognized, it should not be surprising that the two tests do not exhibit a 1 to 1 correlation of transition temperatures. Approximate relationships can be es­tablished between the two tests for clearly defined grades of steel.

In the drop-weight test, a standard specimen of the material is subjected to dynamic loading with crack­ing emanating from a flaw (hard-facing bead) roughly ¼-in. (6-mm) deep and ½-in. (13-mm) wide at a stress level above yield strength. The loading is abruptly ended by a stop after about 2% deformation in the outer fibers. If the notch ductility of the steel is sufficient to restrict crack growth from reaching the specimen edges during the loading period, the test temperature is above the NDT (Nil Ductility Transition).

Although nil ductility behavior is described as a material parameter, it has been shown16 to be sensi­tive to specimen dimensions. Specimen thickness, width, and span length all exert an influence on NDT. An interesting relation has been demonstrated between NDT and section thickness: a linear varia­tion of NDT with the reciprocal of the square root of thickness. Parallel behavior has been shown by other transition temperature tests such as Charpy, van der Veen, Kinzel, compact tension, and wide-plate tests. Thus it is clear that greater inherent toughness is re­quired of the material if it is to exhibit sufficiently low transition temperatures as the section thickness is increased whether in test or in service. An analo­gous principle will be shown to operate in fracture

toughness tests in the following sections.

Linear Elastic Fracture Toughness Tests The linear-elastic fracture mechanics approach to

the design against fracture is basically one in which a critical "stress intensity" is determined that will cause fracture instability due to the presence of a crack. The elastic stress field in the vicinity of a crack tip can be described by a single term parameter des­ignated as the "stress intensity factor." It is a func­tion of the flaw geometry and the nominal stress act­ing in the region in which the flaw resides. Therefore, if the relationship between the stress intensity factor and the pertinent external variables (applied stress and flaw size) are known for a given structural geom­etry containing a particular defect, the stress intensi­ty in the region of the crack-tip can be established from knowledge of the applied stress and flaw size alone.

A critical value of the stress intensity factor, con­ventionally designated Kc, can be used to define the critical crack-tip stress condition for failure. For the opening mode of loading (tension stresses perpendic­ular to the major plane of the flaw) under plane­strain conditions (strain under constraint that pre­vents any strain in the direction parallel to the crack front) the critical stress intensity factor for fracture instability is designated as Kie-

For steels that can develop a region of plastic de­formation at the crack tip, the instability event is ba­sically related to a plastic strain limit (ductility) of the metal crystals located in the plastic zone when stored energy is present. Unstable crack movement occurs when the plastic zone reaches a critical size; the larger the plastic zone size attained ahead of the fracture, the more energy is consumed in propagating the fracture and the tougher the material. If speci­men dimensions are such that the plastic zone size is very small compared to the flaw size, the fracture toughness measured is the lowest possible value, K1c, that will be exhibited by the metal. It is on this basis that K1c is considered a fundamental material pa­rameter.

Analysis by linear elastic fracture mechanics is ac­curate provided that the plastic zone at the tip of the crack is small compared with the general specimen dimensions. As the ratio of plastic zone size to speci­men size increases, linear elastic fracture mechanics methods become inapplicable. For constructional steels of heavy section thickness, plastic constraint due to thickness may produce plane-strain conditions even in normally high plasticity materials. Measure­ments of K1c in these materials would then be a po­tentially useful tool in fracture control, since it is a minimum level of toughness that could be expected under the most adverse stress states.

Linear elastic fracture toughness tests have been designed to restrict the plasticity allowed during the test. A typical specimen, normally fatigue-cracked and loaded in tension to failure, is seen in Fig. 6. This

Cryogenic Nickel Steels 7

R=0.25W

Electrical Resistance

Clip in Displacement

Gage --0

1--s--l

Kc " s"~G2 x Y y = 29.6(0/xt2 - 185.S(a/w).,2 + 655.7(°tw>"2

1011.0< Yw>'2 + 638.s<'¼'w>'tit

W = Specimen Width Pc = Load at Fracture a = Crack Length B = Specimen Thickness

0.45(W-a) [ Y6"ysW]Plastic 0.45W + 0.55a + L X Ve - E Range

Only

Sc = COD at Max Load E = Young's Modulus Ve = Max Load Gage Opening Displacement '-ys = Yield Strength Y = Const., about 2.34 for a,W = 0.5

Fig. 6-Compact tension specimen and displacement gage

specimen, called the Compact Tension sp~cimen, is accepted under the ASTM designation E399 17 and is normally used to measure fracture toughness of steel when limited plastic straining occurs prior to frac­ture.

An alternate specimen under the same specifica­tion, the bend specimen, is seen in Fig. 7. In some re­spects, particularly when dynamic rather than static tests are to be undertaken, the bend specimen is somewhat easier to test (dynamic test results-Kw­are relatively scant).

The Kie derived from the test is calculated as indi­cated in Figs. 6 and 7. The crack length, a, is pro­duced by mechanically notching the specimen and then extending the notch by fatigue loading to the specified limit. The load conditions under which the notch is extended are strictly controlled. Tests are normally run at the temperature of service, but may be run over a range of temperatures. The derived Kie value is then used in analytical expressions relating service flaws and geometries to the allowable stresses.

The validity requirements applicable to the linear elastic fracture mechanics test data as established by ASTM standard E399 are as follows:*

· a ~ 2.5(K1c/<Tys)2 . z

B ~ 2h(K1c/<Tys)

a = (0.45 to 0.55) W

(1).

(2)

(3)

* Other criteria are also usually applied to the shape of the load-displace­ment curve and the specimen crack configuration.

=-------~L 4W ~~ '

Kc ,.

y =

Electrical Resistance Clip in Displacement Gage

...e&xy ew-a.2 2.9 ca1w)~2 - 4.6 ca1w>"2 + 37.6 ·ca1wi12 + 3s_1 C°lwl'l2

Pc = Load at Fracture a = Crack Length

W = Specimen Width

S = Spon

0. 45(W-a) 0.45W + 0.55a

B = Specimen Thickness

[ y oys w] PI as tic x Ve - E Range

Only

Sc = COD at Max Load E = Young's Modulus Ve = Max Load Gage Opening Displacement Sys= Yield Strength Y = Const., about 1.54 for a;W = 0.5

Fig. 7-Bend specimen and displacement gage

Here, a is crack length, B, specimen thickness, W, specimen depth, and <Tys the 0.2% offset yield strength of the steel.

As may be seen from the above, the specimen thickness required for a valid Kie test result is related to the actual value of fracture toughness measured. Thus, if for a given test a high value of Kie in relation to the <Tys is achieved, it may mean that the test can­not be considered valid. It is therefore quite possible to run a series of fracture toughness tests and on evaluating the data discover that none of the tests is valid by linear elastic standards. The results of these tests measure Kc rather than Kie- If service imposes conditions of higher restraint, a lower value, perhaps approaching a valid K1c, may hold, and calculations based on the erroneously high Kc value might not avoid fracture failures.

On the other hand, there are some materials, cer­tain cryogenic steels being good examples, for which either toughness is so high or section sizes normally sufficiently thin that Kie values will never be ob­tained. The fact that full plane strain conditions can­not be achieved does not, in practice, have to elimi­nate the results of such tests from consideration. Pro­vided the application of such steels is known and de­sign considerations taken into account, Kc values ob­tained on the heaviest thickness of the material to be used can serve, with appropriate safeguards, as a use­ful fracture criteria. The only real requirement is that the Kc value obtained realistically reflects the thick­ness and stress state to be expected in service, and that the plasticity produced in the failure not be such that excessive yielding of the specimen violates the basis for the linear elastic characterization. Exactly when this point is reached is still a matter of some debate.

p WRC Bulletin 205

+ Valid Ve 0 Kie (Maximum

COD <( Test 0 Test Load) _J

a:

V, CLIP GAGE DISPLACEMENT ....

Fig. 8-Typical fracture toughness test curves

Crack Opening Displacement Tests (COD) One of the tests which has been developed to mea­

sure toughness under conditions of high plasticity is the Crack Opening Displacement Test. In this test, specimens which do not meet the requirements for linear elastic fracture toughness can still be used to measure crack toughness under conditions which may be more characteristic of many structural appli­cations. The specimen used for these tests need not be different in configuration or size from that seen in Figs. 6 and 7 but may merely utilize different tough­ness criteria than those normally applied to the test data. For example, when making tests of fracture toughness using the Kie approach, the load on the specimen is plotted against the specimen clip-gage opening displacement as seen in Fig. 8. Under condi­tions of little plastic deformation the specimen pro­duces a brittle fracture and the maximum load is used with the crack length for determination of frac­ture toughness. The clip gage opening displacement information is used only to determine that plastic yielding has not occurred in the specimen prior to fracture. In COD tests, the clip gage opening at onset of fracture is measured and used to calculate the crack opening displacement at the crack tip, 8. The critical value of r, at fracture, known as 8c, is a critical strain parameter analogous to the critical stress in­tensity parameter, Kie- It should be noted that in both these types of tests the fracture toughness spec­imen has a fatigue-crack sharpened notch to serve as the sharp-ended flaw required by the analysis.

The value of 8c is a calculated one. The most accu­rate formula to make such a calculation, derived from the work of Wells, is listed in Figs. 6 and 7. The crack opening displacement concept supposes that prior to fracture, the material at the crack tip plastically strains to a very blunt crack, with almost a vertical wall at its tip. In reality, not all materials will behave this way, although many do. Thus the 8c is a measure of crack toughness in terms of the amount of plastic strain that a material will tolerate at a crack tip be­fore failure. Like Kc, the 8c can be related to stress

and flaw size, and thus provide a quantitative mea­sure of allowable stress for each flaw size. The details of this test are found in B.S.I. DD19:1972.18

R-Curve Tests As a result of the rieed to develop tests for thin­

section ductile materials, additional techniques mea­suring the resistance of a material to continued crack growth while the crack is slowly extending under stress have also been developed. Usually referred to as "R-curve" or crack-growth resistance curves, they are intended to take into account the fact that, as a cracked thin-section plate is loaded, a plastic zone develops in front of the crack that is proportional to the crack length. Thus, as a specimen is loaded, slow crack growth produces an increasing plastic zone size and greater and greater resistance to fracture. The growth of the plastic zone, and hence crack growth resistance is dependent on specimen geometry. The resistance of the specimen to further crack growth is expressed as KR (or in terms of fracture mechanics stress intensity calculated as in Figs. 6 and 7) for each crack length produced by slow growth during the test. The data are expressed not by a single pa­rameter Kie (for a thick section) or Kc (for a thin sec­tion) but by a curve of KR vs. ~a, i.e., the resistance of a crack to further growth at each crack extension. The instrumentation for the test is somewhat differ­ent than used for normal Kie testing, in that a stiff loading system (i.e., loading by wedging) is employed and testing is generally restricted to compact tension (Fig. 1) type specimens. Portions of the R-curve may be obtained in normal Kie tests if the test material is thin and ductile enough. Applications of R-curve tests are limited at the present time. The details of testing procedures and examples of R-curve applica­tion techniques are found in ASTM STP 527.19

J Integral Tests The "J Integral" approach to fracture toughness

testing is a third method of determining information about the fracture behavior of materials without going to the (sometimes) large size specimens re­quired to measure valid Kie data by the methods of ASTM specification E399. In order to make such a determination, a new analytical procedure to de­scribe the crack tip region has been developed. This procedure results in a parameter, J, which has been described as the potential energy difference between two identically loaded bodies having similar but not identical crack sizes. This difference may therefore be interpreted as the energy available for crack ex­tension. J integral tests are generally made on speci­mens similar or identical to those seen in Figs. 6 and 7, although in this case small specimens may be used (i.e., the size of a Charpy impact specimen).

The value of the J integral lies in the fact that it is believed to be directly relatable to Kie- Thus, all of the information normally obtained from Kie tests could be obtained from small specimens. Although

Cryogenic Nickel Steels 9

SPECIMEN DIMENSIONS

B AO Oo s A0/9

3 5 3 26 1.67

I 3 1.75 16 3

.625 1.125 .5 6.5 1.8

Fig. 9- The dynamic tear specimen

the original method of J integral determination re­quired several specimens and sophisticated test methods, approximation methods to measure J using a single specimen (as in Fig. 7) have been developed. J may be estimated as follows:

2A J=BxL

where J is as defined above, A is the are.! under the load-deflection curve (Fig. 8) to maximum load, B is the specimen thickness and L is the remaining un­cracked specimen ligament. The measured value of J may then be used to calculate Kie by the relationship:

Here Kie is the "fracture toughness" as defined ear­lier, E is Young's modulus, and v is Poisson's ratio. Once again, there has not been extended application of the J integral as yet in the cryogenic field. Further details on the analytical aspects of the test and on test methods are found in ASTM STP 514 Part II.20

The Dynamic Tear Test The Dynamic Tear or DT test is one that has

evolved from a series of tests developed at the Naval Research Laboratory in Washington, D. C. The pur­pose of this test is to develop a transition in fracture behavior between brittle and ductile over a range of temperatures. In this sense, the test is not unlike the Charpy impact test, but is different in that the speci­men is larger (usually % in. thick); the crack run is longer (usually 11/s in.) and the specimen has a sharp­er notch (fatigue or weld cracked, or pressed). The specimens used in this test are seen in Fig. 9. This test differs from previous ones in that, whereas they are usually static, this test is always dynamic. Details of the test are given in NRL Report No. 7159, "Stan-

6000

5000

ai ..J

,:. 4000 != >-ffi 3000 z "' i.; 2000 ;;i I

1000

-60 -40 -20

1.0 IN. (25 MM l O"ys = 37 ksl

(26 kg/mm 2 )

0

NOT

j Fr'l:~E­

/L- 60°

N

20 40 60 <"Cl

0 '----1~00,,...-~so--so--~40=--~2"'"0...,oc--2='=0~40,-.,,so~s='=o~10-=-o..,.,12~0...,1~40::-'::"c•""'Fl~

TEMPERATURE

Fig. 10-A typical D-T curve

dard Method for the %-inch Dynamic Tear Test." 21

The transition in behavior can be characterized by fracture appearance or by impact energy; in recent work impact energy has been the preferred criterion. Using impact energy has the advantage that the re­sults of the test can then be directly correlated to fracture toughness concepts. This is done through a series of semi-empirical relationships developed from data or plates for which Km, DT impact energy, and Kie data were available. The procedure, although complicated, can be simply stated. The basic premise is that the test data, an example of which is seen in Fig. 10, takes the form of a sigmoidal energy vs tem­perature curve much like Charpy test data. The mid­point in energy of this curve occurs at a condition where a through-thickness crack in the section size tested would have to reach dynamic yield point stresses to propagate. This is interpreted to mean that the following condition is fulfilled.

B = 1.o(Krn)2 <J"yD

where Bis the section thickness and Km and UyD are the dynamic fracture toughness and dynamic yield point, respectively. The dynamic yield point is esti­mated by adding 30 ksi to the static yield point. The energy mid-point provides a temperature, Ye, at which Km may be estimated. The procedures devel­oped with the test also permit several other methods for determining (K1c!Y J from either DT specimen fracture appearance or dynamic load-time measure­ments made during the test. Recent publications suggest that a dynamic R-curve can be developed by using this test with specimens of different crack length, 22 and that Kc may be estimated from DT en­ergy/specimen area.

A similar but less widely used dynamic behavior evaluation test is the Battelle Drop Weight Tear Test. This test uses a full thickness specimen that is

10 WRC Bulletin 205

similar to the dynamic tear except that it has fixed dimensions 3 X 12 in. (76 X 305 mm) and employs a pressed notch as a crack starter. The specimen per­formance is judged on the basis of the fracture ap­pearance(% shear) and tear energy.

Fatigue Tests Fatigue tests of the classical rotated smooth bar

type are not covered in any ASTM specification. The commonly used specimen of this type, however, is a 3½ in. (88 mm) long cylindrical bar with a diameter tapered from about 0.5 in. (12 mm) at the ends to a test section of about 0.3 in. (8 mm) at the bar center. This specimen is normally tested in a rotating test machine held between two flexible chucks so that a load may be applied to cause specimen deflection during the test. When the specimen is deflected any point on the specimen surface is brought first into tension and then into compression as the specimen is rotated. Because the fatigue behavior of steels is quite dependent on the geometry of the specimen and, in practice, the stress system, the fabrication de­tails and the surface finish of the engineering compo­nent the specimen is to represent, a great number of fatigue tests are also run on specimens representing specific types of engineering applications.

The cyclic life of cryogenic steels, like other mate­rials, increases as the cyclic stress decreases until a stress is reached where the cyclic life becomes indefi­nitely large. This level is the "fatigue limit." In typi­cal cryogenic fatigue design, the expected cyclic expe­rience of the engineering component is ascertained and the cyclic stress level set on the basis of the an­ticipated fatigue life requirement. When the cyclic stress history is uncertain, the stresses must be set at or below the fatigue limit. Because cryogenic temper­atures change fatigue behavior it is usually desirable to perform tests in the service temperature range. Since room temperature tests usually produce endur­ance limits that are lower rather than higher than those obtained at cryogenic temperatures, room tem­perature fatigue tests give conservative values.

With the increasing interest in characterizing steels by fracture mechanics concepts, emphasis in fatigue testing of cryogenic steels has shifted to crack growth behavior. The reasoning behind this shift is two-fold. First, since most engineering components contain some kind of flaw or discontinuity it is the crack growth, not the crack initiation, portion of the fatigue life that is of interest. Endurance limit tests summate both. Secondly, a fracture mechanics analy­sis of a component requires a knowledge of flaw sizes at all points in the service life of the material. Since initial flaws grow by fatigue during this life, the rate of flaw growth, or crack propagation rate, must be known to assess the flaw size at the end of life and ensure that it does not exceed the critical fast-frac­ture flaw size for the material.

Fatigue crack growth rate tests usually are made using the fracture mechanics parameter, K, as the

means of characterizing growth rate behavior. The variations in K, the M, caused by variations in stress acting upon the flaw size, are correlated to the rate of crack growth by an expression of the type:

da dN = A(AK)m

where a is crack length, N is the number of cycles, M is the stress intensity factor range, and A and m are constants reflecting such variables as mean stress, material properties, and environment. Test speci­mens used in studies of this type can be similar to the one shown in Fig. 6, or can be center-notched or cen­ter-cracked panels wide enough for a fatigue crack to grow through the specimen thickness and then later­ally toward the specimen edges. In the case of speci­mens like those of Fig. 6, growth rates over a wide range of M can be determined. The total life of the component is determined by knowing or assuming an initial flaw size and, using the measured growth rate, integrating to find the total life. The center-cracked wide-plate specimen has an added advantage in that an initial flaw of the size typical of fabrication defects can be placed in the specimen and the growth of the flaw to a critical size producing fast fracture can be observed. In this way not only crack growth informa­tion but also crack shape and final fast fracture infor­mation may be obtained on the same specimen.

Significant Criteria for Cryogenic Materials Evaluation

Of the many design criteria and parameters that have been discussed in this report, not all are equally applicable to establishing the fracture behavior of cryogenic nickel steels. While the static mechanical properties such as tensile strength, or in some cases yield strength, are the conventional parameters used to determine what the maximum· allowable stresses may be, fracture toughness is the additional limiting factor that now becomes most critical. Strength and toughness requirements are interdependent·· since higher allowable stress levels in these steels, achieved, for example, by increasing the static tensile strength, produce greater amounts of stored energy in the fabricated structure. This energy represents a greater potential driving force for fracture, and thus must be accompanied by increased fracture resis­tance. The static strength of steels increases as the temperature of service decreases. If these higher strength levels are employed to increase allowable stress levels in the cryogenic service temperature range, the specified toughness levels must be compat­ible with the higher stresses.

Relating notch toughness to the expectable service performance of a material is a most difficult engi­neering task. Classical transition temperature behav­ior, in terms of Charpy V-notch or Drop-weight NDT values, is a suitable guide to determine if a given heat of material is tougher or more frangible compared to other heats of the same material. While these tests,

Cryogenic Nickel Steels 11

Table 2-Compositional Requirements and Heat Treatment of ASTM AZ03 Steels

A203 Chemical requirements• (ladle analysis) Grade Thickness C Mn p s Si Ni

A up to 2 in. (51 mm) 0.17 0.70 0.035 0.04 0.15-0.30 2.10-2.50 over 2-4 in. (51-102 mm) 0.20 0.80 0.035 0.04 0.15-0.30 2.10-2.50 over 4-6 in. (102-152 mm) 0.23 0.80 0.035 0.04 0.15-0.30 2.10-2.50

B up to 2 in. (51 mm) 0.21 0.70 0.035 0.04 0.15-0.30 2.10-2.50 over 2-4 in. (51-102 mm) 0.24 0.80 0.035 0.04 0.15-0.30 2.10-2.50 over 4-6 in. (102-152 mm) 0.25 0.80 0.035 0.04 0.15-0.30 2.10-2.50

D up to 2 in. (51 mm) 0.17 0.70 0.035 0.04 0.15-0.30 3.25-3.75 over 2-4 in. (51-102 mm) 0.20 0.80 0.035 0.04 0.15-0.30 3.25-3.75

E up to 2 in. (51 mm) 0.20 0.70 0.035 0.04 0.15-0.30 3.25-3.75 over 2-4 in. (51-102 mm) 0.23 0.80 0.035 0.04 0.15-0.30 3.25-3.75

• All compositions are maximum unless range is stated. Heat Treatment: All plates are to be treated to produce grain refinement by normalizing or heating uniformly for hot form­

ing. Temperature for hot forming shall be equivalent to and not significantly in excess of normalizing temperature. Suitable normalizing temperature: A203 Grades A and B: 1650° F (900° C); A203 Grades D and E: 1600° F (870° C).

usually fixed by a ductility criterion (i.e., Charpy lat­eral expansion or drop-weight nil ductility transi­tions) may assist in avoiding brittle behavior, t~ey cannot predict quantitatively the behavior of a mate­rial in a service structure under conditions of measur­able but restricted ductility.

Both laboratory testing and service fracture analy­sis have made it clear that design criteria must be employed that set allowable stress levels on the basis of appropriate fracture toughness test results. The fracture toughness tests described previously have been devised to enable the selection of safe design stresses and simultaneously provide a means by which fatigue behavior can be evaluated. Having fo­cussed attention on these tests, however, it is also im­portant to note that Krc tests do not seem wholly ap­propriate. These are predicated on linear elastic be­havior (at least in theory) and thus do not accurately characterize the available toughness in materials at elastic-plastic range service temperatures. In most cases, the nickel steels are sufficiently tough to ren­der measurements of Krc values impossible except indirectly. Consequently tests measuring COD, K, J, or R-curve behavior should be the most fruitful for these steels. However, not all of these tests are well developed at this time, nor are they correlated closely with service behavior. The dynamic tear test could also be used, but this provides fracture toughness in­formation only indirectly when compared to the frac­ture mechanics tests. The few data available from these tests for the nickel steels are gathered in this report.

As will be shown later in this report, Kc or COD values curves will not, in themselves, be the end re­sult of our analysis. That end result must be the specification either of maximum allowable crack or flaw sizes at a given design stress level or of a maxi­mum allowable stress level for a known flaw size. If this flaw size is based on an elastic-plastic criterion such as one of those mentioned above, critical flaw sizes or stress levels will be established on realistic material behavior.

The Low-Nickel Steels

Specifications The 2¼ and 3½% nickel steels are covered by the

ASTM A203 grades. In Table 2 are listed the compo­sition limits, thickness range and recommended heat treatments specified. Table 3 contains a summary of the mechanical properties required by the specifica­tions, and, for comparison, typical ranges of proper­ties23 to be expected in these steels. Notch-toughness supplementary requirements for these steels are set forth in ASTM Specification A593.

Tensile Properties Since the room temperature tensile properties of

the 2¼ and 3½% Ni steels are prescribed by specifica­tions, the items of interest in this survey are the changes in properties induced by test (service) tem­peratures. heat treatments, section size, cold defor­!tlation, and welding. Statistical data are unavailable for any of these factors, so that· trends must be in­ferred from tests on a limited number of heats. Data are more plentiful for the 3½% Ni grade than for the 2¼% Ni grade.

Effect of Temperature. In a study 24 of the frac­ture toughness of the A203 grades, the tensile proper­ties of 1.65-in. (42-mm) A203 Grade A and 2-in. (51-mm) Grade Din the normalized and in the quenched and tempered conditions were determined over the temperature range from 75° F (25° C) to -250° F (-156° C). The results are shown in Figs. 11 and 12. The increase in yield and tensile strengths is consis­tently about 30 ksi (205 MPa) as temperature is low­ered from ambient to -250° F (-150° C), most of the rise occurring below -150° F (-100° C). The investi­gators found that the elongation rose about 15% and the reduction of area decreased about 10% with re­duced temperature.

Effect of Heat Treatment and Plate Thickness. Although the A203 grades are specified to be heat treated by normalizing, considerable attention has been devoted to the properties that can be obtained by use of water quenching and tempering, especially

12 WRC Bulletin 205

Tensile strength Yield point, min Elongation in 8 in., min Elongation in 2 in., min

Table 3-Mechanical Property Requirements of ASTM A203 Steels

~---------Tensile requirements---------~ Grades A and D

65 to 77 ksi (450-530 MPa) 37 ksi (255 MPa)

19% 23%

Grades B and E 70 to 85 ksi (480-585 MPa)

40 ksi (273 MPa) 17% 21%

Notch toughness requirements (A593) ~-------------V-Notch Charpy Test Performanc,e-------------~ ~Energy Requirement~ Test Temperatures for Plate'-------~

Steel Grade Grade A Grade B Grade D Grade E

Avg. 3 spec. Minimum 1 in. max (25 mm) 2 in. max (51 mm) 13 ft-lbf (17 .5 J) 10 ft-lbf (13 .6 J) -90° F ( -70° C) -90° F (-70° C) 15 ft-lbf (20 .3 J) 12 ft-lbf (16 .2 J) -90° F (-70° C) -90° F ( -70° C) 13 ft-lbf (17 .5 J) 10 ft-lbf (13 .6 J) -150° F ( -100° C) -150° F ( -100° C) 15 ft-lbf (20 .3 J) 12 ft-lbf (16 .2 J) -150° F (-100° C) -150° F (-100° C)

Over 2 in. (51 mm) -75° F (-60° C) -75° F (-60° C)

-125° F ( -85° C) -125° F (-85° C)

~---------------Typical ranges of mechanical propertie's---------------~ Normalized ½-2 in. plates

(13-102 mm) Tensile strength Yield point Elongation in 2 in.

A203A and B 70-76 ksi (480-520 MPa) 47-55 ksi (320-370 MPa)

30-37%

A203D and E 72-80 ksi (495-550 MPa) 50-68 ksi (345-990 MPa)

28-36% V-Notch Charpy test values 18-35 ft-lb at -75° F (25-48 J at -60° C) 22-40 ft-lb at -150° F (30-54 J at -100° C)

NORMALIZED A203 GR.A

OTS. eYs.

45 LONGITUDINAL TO RD. -250 -200 -150 -100 -50 0 50 100

TEMPERATURE - °F

Fig. 11A-Effect of temperature on tensile data of normalized A203 Grade A material

<Ii ><'.

1/1 1/1

110

li! 70 1-1/1

60

NORMALIZED A203 GR.D

OTS. eYS.

--------~ TRANSVERSE TO R.D.

-250 -200 -150 -100 -50 0 50 100 TEMPERATURE - °F

Fig. 12A-Effect of temperature on tensile data of normalized A203 Grade D material

1/1 1/1 w Cl:'.

tii

QUENCHED & TEMPERED - A 203 GR A

55 LONGITUDINAL TO R.D.

OT.S. eY.s.

-250 -200 -150 -100 -50 0 TEMPERATURE - °F

50 100

Fig. 11B-Effect of temperature on tensile data of quenched and tempered A203 Grade A material

120 QUENCHED & TEMPERED - A 203 GR. D

TRANSVERSE TO RD.

OTS. e YS.

-250 -200 -150 -100 -50 0 TEMPERATURE - °F

Fig. 12B-Effect of temperature on tensile data of que~c~ad and tempered A203 Grade D material

Cryogenic Nickel Steels 13

Table 4-Typical Room-Temperature Tensile Properties of the Low-Nickel Steels in a Range of Thicknesses and Heat Treatments

% Refer- Gage, Yield str., Tensile str., Red.

ence %C in. (mm) Heat treatment ksi (MPa) ksi (MPa) % Elong. area 21/.% Ni Steel

24 0.14 1.65 (42) Norm. 1650° F(900° C) 48 (330) 70.6 (485) 36 in 1 in. (25 mm) 65 WQ1650(900)

26 0.14 1.65 (42) Temp. 1150(620) 61.3 (420) 80 (550) 33 in 1 in. (25) 77 0.15 1 (25) Norm. 1550(840) 58 (400) 74 (510) 28 in 8 in. (203)

3½% Ni Steel 26 0.15 4 (102) N1650° F(900)T1150° F(620) 62.4 (430) 78.5 (540) 32 in 1 in. (25 mm) 70.5

0.15 4 (102) WQ1650(900)Tl150(620) 68.4 (470) 84.6 (580) 30 in 1 in. (25) 74 52 0.12 ½ (13) WQ1660(905)Tll 75(635) 84 (580) 92 (635) 14 in 8 in. (204) 69

0.12 ½ (13) WQ1600(870)T1175(635) 83 (575) 94 (650) 15 in 8 in. (204) 69 0.12 1¼ (32) WQ1600 (870) T1150 (620) 76 (525) 88 (610) 23 in 8 in. (204) 68

53 0.15 •;. (16) N1700(925) 57 (395) 80 (550) 36 in 1 in. (25) 70 0.15 • I B (16) WQ1650(900)Tll50(620) 73 (505) 86 (600) 29 in 1 in. (25) 74

52 0.14 7/s (22) N1650(900)Tll50(620) 68 (470) 80 (550) 31 in 2 in. (51) 68 0.14 7/s (22) WQ1650(900)T1150(620) 89 (615) 96 (665) 27 in 2 in. (51) 70 0.12 1 (25) N1650(900)Tl150(620) 64 (445) 75 (520) 34 in 2 in. (51) 72 0.12 1 (25) WQ1650 (900)T1150 (620) 80 (550) 89 (615) 28 in 2 in. (51) 73 0.10 1 (25) N1650(900)Tl150(620) 59 (410) 71 (490) 35 in 2 in. (51) 73 0.10 1 (25) WQ1650 (900) T1150 (620) 66 (460) 79 (545) 34 in 2 in. (51) 78 0.10 ¼ (19) WQ1600(870)T1150(620) 72 (500) 82 (570) 35 in 2 in. (51) 79 0.18 1 (25) WQ1600(870)T1150(620) 78 (540) 92 (635) 30 in 2 in. (51) 73

38 0.11 2 (51) N1650(900) 53 (370) 73 (505) 39 in 1 in. (25) 67 0.11 2 (51) WQ1650(900)T1150(620) 63 (435) 80 (550) 34 in 1 in. (25) 78 0.15 1 (25) N1650(900) 57 (395) 77 (540) 52 in 2 in. (51) 0.12 1 (25) WQ1650(900)T1150(620) 65 (450) 82 (570) 29 in 2 in. (51) 74 0.12 1 (25) N1650(900) 52 (360) 71 (490) 23 in 8 in. (204)

52 0.13 1 (25) WQ1550(840)T1250(680) 55 (380) 90 (620) 26 in 2 in. (51) 69 0.13 P/16 (37) WQ1550(840)T1250(680) 53 (365) 87 (605) 28 in 2 in. (51) 69 0.13 1¼ (45) WQ1550(840)T1250(680) 53 (365) 88 (610) 27 in 2 in. (51) 68 0.13 2 1/16 (52) WQ1550(840)T1250(680) 54 (370) 89 (615) 28 in 2 in. (51) 68 0.13 2"/16 (68) WQ1550(840)Tl250(680) 52 (360) 84 (580) 29 in 2 in. (51) 70 0.15 •;. (16) WQ1650(900) WQ1310 (710) 69 (475) 88 (610) 33 in 2 in. (51)

WQ1110(600) 0.11 2 (51) WQ1110(600) 63 (435) 80 (550) 36 in 2 in. (51) 0.11 2 (51) WQ1650(900)T1150(620) 65 (450) 82 (570) 32 in 2 in. (51)

Table 5-Effect of Cold Deformation and Aging on Room Temperature Tensile Properties of 3½% Nickel Steel

% Elong. %

Refer- Gage, % Yield str., Tensile str., in 1 in. Red. ence %C in. (mm) Heat treatment Strain Postheat ksi (MPa) ksi (MPa) (25) area

26 0.15 4 (102) Nl650 (900) T1150 (620) 0 62 (430) 79 (545) 32 71 Nl650 (900) T1150 (620) 5 R.T. 77 (540) 85 (595) 27 70 N1650 (900) T1150 (620) 5 500 (260) 83 (570) 87 (605) 26 69 N1650 (990) T1150 (620) 5 1150 (620) 67 (460) 82 (570) 29 71

26 0.15 4 (102) WQ1650 (900) T1150 (620) 0 75 (510) 91 (625) 28 75 WQ1650 (900) Tl150 (620) 5 R.T. 94 (650) 99 (680) 24 73 WQ1650 (900) Tl150 (620) 5 500 (260) 103 (710) 103 (710) 20 71 WQ1650 (900) Tl150 (620) 5 1150 (620) 77 (530) 92 (635) 29 74

Notes: 1. Behavior of 4-in. plate near surface simulated by cooling ½-in. (13-mm) sections in still oil or in Al foil lined box. See reference.

2. N = normalized, T = tempered.

for thicker plates. Table 4 lists the tensile property data that are available for the low-nickel steels. Those for the 2¼% Ni grades are notably scant. It is evident from a scan of the data that a significant gain in strength ensures from quenching and tempering without impairment of ductility. This gain is illus­trated in Fig. 13 for the yield strength of 3½% nickel steel.

Figure 13 also indicates that the effect of plate thicknesses between ½ and 2 in. (13 to 51 mm) on

yield strength is not great. As one would expect, the effect is more evident for quenched and tempered steel than for normalized steel. The thermal stress re­lief or temper treatment after normalizing seems to produce a useful rise in the yield strength.

Effect of Cold Deformation and Aging. Table 5 contains some data on the changes in tensile proper­ties produced in 3½% Ni steel by cold straining and by subsequent aging. Although the information is scant, it is consonant with observations of the behav-

14 WRC Bulletin 2(li:;;

Table &-Room-Temperature Tensile Properties of Welded 31/,% Nickel Steel

Transverse weld tests Yield Tensile str., str., %

Refer- Gage, Weld ksi ksi Red. ence in. (mm) Heat treatment metal Passes Postheat (MPa) (MPa) % Elong. area

38 1 (25) Nl650(900) 3½Ni-SAW 2 no 52 (360) 71 (490) 22 in 8 in. (204) 63 1 (25) N1650(900) 3½Ni-SAW 2 1150 (620) 50 (345) 63 (435) 27 68 1 (25) N1650(900) 3½Ni-SAW 10 no 52 (360) 71 (490) 23 63 1 (25) N1650(900) 3½Ni-SAW 10 1150 (620) 49 (340) 68 (470) 24 67

54 1 (25) WQ1650(900)Tl100(595) E-NiCrFe-2 20 no 61 (420) 81 (560) 43 in 2 in. (51) 1 (25) WQ1650(900)Tl100(595) E-NiCrFe-2 20 1100 (595) 64 (440) 79 (545) 41 1 (25) WQ1650(900)Tll00(595) E-NiCrFe-2 10 no 61 (420) 81 (560) 39 1 (25) WQ1650(900)Tl100(595) E-NiCrFe-2 10 1100 (595) 62 (430) 79 (545) 44

Note: All failures were in base metal.

Weld metal tests

Refer- Gage, Filler erice in. (mm) Passes Process metal

AWSPad SMA 3½% Ni AWSPad SMA 3½% Ni

38 1 (25) 2 SAW 3½% Ni 1 (25) 2 SAW 3½% Ni 1 (25) 10 SAW 3½% Ni 1 (25) 10 SAW 3½% Ni

53 6/s (16) 9 GMA 0/s (16) SMA E-NiCrFe-2

ior of other low-alloy steels similarly processed. The 5% prestrain raises the yield strength markedly but the tensile strength less than half as much. Elonga­tion is lowered about equal to the amount of pres­train. Aging at 500° F (260° C) further increases the yield strength and to a lesser degree the tensile strength. Treatment at 1150° F (620° C) restores al­most completely the properties to those of unstrained material.

Effect of Welding. The limited information about the tensile properties of the welded low-nickel steels suggests that 100% joint efficiency is readily attained, as shown in Table 6 for the 31h% Ni grade. All failures in transverse weld joint tests were located in the un­affected base metal. The reason for this behavior is easily found in the all-weld metal tensile test results. The weld metals tend to overmatch the base plate and frequently exceed the specification limits for the A203 grades. High heat-input submerged-arc depos­its may not quite match quenched and tempered base plates in strength if the 2-pass welds in 1-in. (25-mm) plates are representative.

Notch Toughness Prior to 1955, the evaluation of the notch tough­

ness of low-nickel steels for low-temperature service was c;onducted mostly with the keyhole-notch Char­PY specimen. While the V-notch has been adopted, the Charpy test is still the principal means of mea­suring toughness and, of course, is specified in A593. While interest in various fracture- toughness tests has recently increased, their use is largely confined to laboratory studies and has not been extended to quality control or material specifications for the A203 steels.

% Yield str., Tensile str., Red.

Postheat ksi (MPa) ksi (MPa) % Elong. area no 75 (520) 86 (595) 30 in 2 in. (51) 71 no 75 (520) 82 (570) 30 in 2 in. (51) 71 no 64 (440) 76 (525) 6 in 2 in. (51) 14

1100 (595) 57 (395) 70 (485) 9. 19 no 75 (520) 92 (635) 12 22

1100 (595) 66 (455) 84 (580) 19 37 no 66 (455) 87 (600) 27 in 1 in. (25) 73

1100 (595) 65 (450) 86 (595) 37 in 1 in. (25) 75

Charpy Test Results. The Charpy V-notch test data tabulated in Table 7 were obtained generally from the same sources providing the tensile data of Table 4. With one exception, a 7k-in. (22-mm) nor­malized 3½% Ni plate, all of the heats reported meet A593 requirements. The performance of the steels ac­cording to more rigorous criteria (higher energy re­quirement or fracture appearance) is also indicated in Table 7.

The consequence of quenching and tempering in place of normalizing is clearly evident from the test results. The advantage is shown graphically in Fig. 14, which also suggests the extent of the thickness ef­fect. It may be noted that the quenched and tem­pered steels meet the temperature requirements of A593 at a 30 ft-lb (40 J) level as well.

Drop-Weight Test Results. For some of the steels

25 mm 50 600

500

o ~ (Norm.) 400

----0---- _ Q_ I

0.5 1.0 1.5 2.0 Plate Thickness in inches

Fig. 13-Effect of heat treatment and section thickness on the yield strength of 3½% nickel steel

Cryogenic Nickel Steels 15

1--' a)

§ ~ tx:, E. ~ ..... s· l'I:)

~

Table 7-Typical Notch-Toughness Data for Low-Nickel Steels in a Range of Thicknesses and Heat Treatments

Refer- Gage, harpy trans temperatures, ° F (° C) ence in. (mm) Heat treatment 15 ft-lb (20 J) 30 ft-lb (41 J) 15 mil (0.04 mm) 50% Shear

21/4% Nickel Steel 24 1.65 (42) N1650(900) -115 (-80) -80 (-60) -145 (-100) -50 (-45)

1.65 (42) WQ1650(900)Tll50(620) -155 (-105) -120 (-85) -160 (-105) -75 (-60) 38 ¼ (13) N1600(870) -130 (-90) -80 (-60) -140 (-95) -80 ,(-60)

¼ (13) Nl600(870)Tl100(595) -100 (-75) -40 (-40) -120 (-85) -80 (-60) 8 1 (25) N1600(870) -100 (-75) -40 (-40) -120 (-85) -60 (-50)

1 (25) N1600(870)Tl100(595) -105 ( -75) -50 (-45) -120 (-85) -55 ( -50) 1 (25) N1550(845) -110 (-80) -70 (-60) -110 (-80) -50 (-45)

3¼% Nickel Steel 52 ¼ (13) WQ1660(905)Tll 75(635) -200 ( -130) -175 (-115)

¼ (13) WQ1600(870)Tll 75 (635) -180 (-120) -165 (-110) 11/4 (32) WQ1600(870)Tl150(620) -200 (-130) -165 (-110) -190 (-125) -140 (-95) 11/4 (32) WQ1600(870)Tl150(620) -180 (-120) -200 (-130) -150 (-100)

53 1 (25) WQ1550(845)T1250(725) -225(-145) -180 (-120) -210 (-135) -115 (-80) l7/16 (37) WQ1550(845)Tl250(725) -200 (-130) -170 (-115) -205 (-130) -100 ( -75) 13/. (45) WQ1550(845)Tl250(725) -190(-125) -150 (-100) -185 (-120) -80 (-60) 21/u (52) WQ1550(845)Tl250(725) -160(-105) -130 ( -90) -150 (-100) -70 (-55) 211/16 (68) WQ1550(845)T1250(725) -170 (-115) -135 (-95) -170 (-115) -70 (-55) "/s (16) N1700(925) -200 (-130) -125 (-85) -175 (-115) -50 (-45) "/s (16) WQ1650(900)Tl150(620) -250 ( -155) -185 (-120) -200 ( -130) -90 (-70)

WQ1650(900)WQ1310(710) "/s (16) WQ1110(600) -265 ( -165) 2 (51) N1650(900) -160 (-105) -125 (-85) -160 (-105) -80 (-60) 2 (51) WQ1650(900)Tll50(620) -225 (-145) -190 -(125)

WQ1650 (900) WQ1310 (710) 2 (51) WQ1110(600) -225 ( -145) 2. (51) N1650(900) -170 (-115) -130 (-90) -175 (-115) -75 (-60) 2 (51) WQ1650(900)Tll50(620) -220 (-140) -190(-125) -230(-145) -125 (-85)

52 7/s (22) N1650(900)Tl150(620) -135 (-95) -115 (-80) -135 (-95) -60 (-50) 7 / 8 (22) WQ1650(900)Tll50(620) -190 (-125) -155 (-105) -175 (-115) -140 (-95) 1 (25) N1650(900)Tl150(620) -175 (-115) -125 (-85) -170 (-115) -75 (-60) 1 (25) WQ1650(900)Tl150(620) -220 ( -140) -170 (-115) -210 (-135) -80 (-60) 1 (25) N1650(900)Tl150(620) -170 (-115) -140 (-95) -190(-125) -90 (-70) 1 (25) WQ1650(900)T1150(620) -200 ( -130) -230(-145) -160 (-105) ¼ (19) WQ1600(870)Tl150(620) -225 (-145) -200 ( -130) -130 (-90) 1 (25) WQ1600(870)Tl150(620) -225 (-145) -80 (-60)

Note: N = normalized, WQ = water quenched, T = tempered.

Drop weight NDT, OF(° C)

-75 (-60) -110 (-80) -110 (-80)

-90 (-70)

-70 (-55)

-140 (-95) -185 (-120)

-210 (-135) -120 ( -85) -160(-105)

-170 (-110) -110 (-80) -130 ( -90) -100 (-75) -130 (-90) -120 ( -85) -170 (-115) -110 (-80) -160(-105) -200 ( -130) -150 (-100)

0 50 fflf'!'I IOO I I I I • •

ci j -150 - -100 F: 00. Ill C

;g • 0 6 - • ~ D~ 6 6 u

- -1250 :9-200- 0 66

d: !Q

6 6 6WQ6 Temp. ~ - 66 6 o Normalized ... • Nonn.aTemp . 0 ~ -~150 u

-2500 6 I I I I

1.0 20 3.0 4.0 Plate Thickness in inches

Fig. 14-Charpy test notch-toughness of 3½% nickel steels

of Tables 4 and 7, drop-weight test data were also available. The NDT temperatures average some 60° F (33° C) higher than the 15 ft-lb Charpy tempera­tures for 3½% Ni steels and about 30° F (17° C) high­er for the 2¼% Ni steels. The implications of these differences to service applications will be considered later.

Fracture Toughness Test Results. A single re­port24 was available containing information on the fracture-toughness of the low-nickel steels, as deter­mined by compact tension and notched slow-bend specimens. Both static and dynamic strain rates were incorporated in the tests, and several methods of an­alyzing the test data were used to calculate the values of fracture toughness. Tests were conducted on 1.65-in. (42-mm) thick A203 Grade A steel and 2-in. (51-mm) thick A203 Grade D steel each in the normal­ized or in the quenched and tempered condition. Stress intensity factors, (Kq) were calculated and an­alyzed according to ASTM specification E-399 rec­ommendations to determine whether each Kq was a valid plane-strain fracture toughness number, Kie•

The results are displayed in Figs. 15 to 18. The figures indicate that both steels exceeded the

fracture toughness level below which plane-strain fracture can occur under static loading at their re­spective temperatures specified in A593. This was true for both normalized and quenched-and-tem­pered plates; it did not prove to be so, however, for the dynamic loading of A203 Grade D steel. These re­sults are corroborated by the NDT temperatures ob­tained, inasmuch as the drop-weight test is also a dy­namic loading test with a sharp flaw provided by brittle hard-facing weld metal.

Effect of Strain Aging. Very few data were dis­covered regarding the effect of strain aging on the notch toughness of low-nickel steels. As Table 8 indi­cates, strain aging raises the Charpy transition tem­perature of the steels significantly, to a considerably greater degree in the case of A203 Grade A than for A203 Grade D. Restoration of toughness is gained by

A203 GRADE A NORMALIZED 1.645 INCH PLATE

~160 uj150 :S:::140 ;;?"130 ;;120 ~110 U100 i£ 90 >- 80 t: 70 ~ 60 ~ 50

RW SPECIMEN

• VALID Kie TEST

-•----------•

o/ ~-()

/.STATIC

DATA

0

NDT ~ 40 1/l 30 ~ _'=30..J,...,,.o----2.,.J50'==----_=200-!,.,,,..--...,_1.,!,5""0 ____ 1'""00'=---'--,_50-

~ TEMPERATURE - °F

Fig. 15- The effect of temperature on the static fracture toughness of normalized A203 Grade A material

A203GRADE A QUENCHED& TEMPERED l645INCH PLATE

~160 <ii 150 :,:::140 ,2·130 ~120 ~110

RW SPECIMEN

0100 Li: 90 5cJ.tlf ,'O

80 ,,o-' ~ 70 / ~ 60 •/

w 50 ------· ~ 40 -•

0

0

0

• VALID Kie TEST

1/l 30 NDT ~ -""300~--...,_2~s=o,----_=200"'=---_-=,~so=--~_,,..,obo,------._5=-o-' Cl:'. TEMPERATURE - °F ti Fig. 16-The effect of temperature on the static fracture toughness of quenched and tempered A203 Grade A material

~160 ~150 ~-140

A203 GRADE D NORMALIZED 2 INCH PLATE

~130 ~120

. WR SPECIMEN

.t. lRWIN'S CRITERION for Kid at the NDT

\::i110 O,' i£100 ,

0 0

0

0

• VALID Kie or Kid TEST

~ ~g STATIC /' <ii 70 ~DATA e .ii.,,.,,, Q 60 ..,./_"' !z 50 -• 1_____...,. DYNAMIC - 40 - DATA

~ 30 NDT w L_3c!o~o---_-='25'=0~---~200~--...,_1..!5=0---'-_=,oo"=---...,_5""0""

~ TEMPERATURE - °F

Fig. 17- The effect of temperature on the static and dynamic frac­ture toughness of normalized A203 Grade D materials

le A203GRADE D QUENCHED& TEMPERED 2INCH PLATE

> 160 WR SPECIMEN B f2150 o ~·140 .t.lRWIN'S CRITERION ~ 130 for Kid at the NDT 0 Cl:'.120 ~110

~1~ o ____ /o ~ 80 • <ii 70 ,0

STATIC DATA

• VALID Kie or Ktd TEST

0

r5 60 / !z 50 / - 40-• -•-·

o ~YNAMIC /e DATA /.

~ 30 NDT ~ '-_3~00~---""2'=50=----""2""0=0--...,_1.1as=oc--'---_7,,o"'o-----50~ ti TEMPERATURE - °F

Fig. 18-The effect of temperature on the static and dynamic frac­ture toughness of quenched and tempered A203 Grade D material

Cryogenic Nickel Steels 17

Table 8-Effect of Cold Deformation and Aging on the Notch Toughness of Low-Nickel Steels

Refer- Gage, Heat % ence in. (mm) treatment Strain Postheat

2¼% Nickel steel 8 1 (25) N1550 (845) 0 no

1 (25) N1550 (845) 5 no 1 (25) Nl550 (845) 5 1150 (620)

3½% Nickel steel 8 4 (102) N1650 (900), 0

T1150 (620) 4 (102) N1650 (900), 5 R.T.

T1150 (620) 4 (102) N1650 (900), 5 500 (260)

Tll50 (620) 4 (102) N1650 (900), 5 1150 (620)

Tl150 (620) 4 (102) WQ1650 (900), 0

Tl150 (620) 4 (102) WQ1650 (900), 5 R.T.

Tl150 (620) 4 (102) WQ1650 (900), 5 500 (260)

T1150 (620) 4 (102) WQ1650 (900), 5 1150 (620)

T1150 (620)

subsequent thermal stress relief at 1150° F (620° C). The data are too scant to do more than indicate a trend.

Effect of Welding. The presence of welded joints in steel structures is relevant to the notch toughness of the structure because of possible stress-raising flaws, inadequate weld metal properties, or distur­bances of the original characteristics of the steel in the HAZ produced by welding. If as often is the prac­tice, it is assumed that all welded joints contain flaws, it is the task of the fabricator to keep the flaw size small enough to assure safe performance by suit­able inspection and quality control methods.

The problem of matching the strength and notch toughness of weld metals to that of the low-nickel base plates has been satisfactorily met for the pro­duction welding processes. The 2¼% Ni steels are welded with 2½-3 1h% Ni electrodes under moderate heat inputs, e.g., E8016-C2 or E8018-C2. The 3½% Ni steels are welded variously with nickel-base Cr-Fe al­loys, austenitic Cr-Ni steels, and Mn-Mo-Al-modi­fied 3½% Ni steel. 23

Despite many efforts, the evaluation of the notch toughness of the weld heat-affected zone has not been reduced to a standard procedure. The difficulty is that the HAZ is narrow, irregular in shape,. and non-uniform in microstructure because of the sharp temperature gradient across it and the partial reheat­ing effects in multiple-pass welds. Tests on entire weld joints are logical, but they become expensive and require high loads or special equipment. Most commonly, Charpy tests with the notch located in the zone of interest, explosion bulge tests, or wide plate tests have been applied to the evaluation.

Table 9 is a compilation of the notch toughness data available for welded low nickel steels. With one

Charpy Transition Temperatures, ° F (° C) 15 ft-lb 30 ft-lb 15 mil 50% (20 J) (41 J) (0.04 mm) Shear

-110 (-80) -70 (-60) -110 (-80) -50 (-45) -75 (-60) -25 (-30) -75 ( -60) -25 (-30) -40 (-40) +10 (-10) -45 ( -45) +15 (-10)

-130 (--90) -130 (-90)

-105(-75) -100(-75)

-105 (-75) -95 (-70)

-120 (-85) -130 (-90)

-205 (-130) -180 ( -120)

-200 (-130) -170 (-115)

-185 (-120) -165 (-110)

-200 (-130) -190(-125)

exception, Charpy tests taken from the HAZ showed toughness equal or superior to that of the unwelded 2¼% Ni plate. Similarly, drop-weight tests conducted on welded joints of 3½% Ni steel plates with the crack starter bead along the weld edge or transverse to the weld joint displayed NDT temperatures the same as in unwelded plates. Kinzel tests produced transition temperatures in the same range as those to be expect­ed from drop-weight tests.

Generally, the low-nickel steels show a low sensi­tivity to welding in notch-toughness tests. This be­havior is probably due to a combination of the low carbon content of these steels and the ability of nick­el to confer toughness on the mixed microstructures formed in the weld heat-affected zone.

Fatigue Strength A search of the literature did not yield any data on

the fatigue properties of the low-nickel cryogenic steels. Investigations on other steels have shown that the fatigue limit tends to rise as the testing tempera­ture is lowered below room temperature. This is in keeping with the facts that tensile strength increases at lower temperatures and high-cycle fatigue strength varies in concert with tensile strength in the absence of sharp stress raisers.

In an investigation 25 of a nickel-containing pres­sure vessel steel, A533, it was reported that the fa­tigue crack-growth rate was slightly lower at 0° F (-18° C) than at 75° F (23° C). See Fig. 19. It is in­teresting to note that the Charpy test notch tough­ness was much lower at 0° F (-18° C) than at room temperature (15 ft-lb vs. 50 ft-lb, or 20 J vs. 68 J). From these data it can be inferred that fatigue crack growth rates are not adversely affected by low tem­peratures and concomitant low notch toughness. If

18 WRC Bulletin 205

Table 9-Notch Toughness of Welded Low-Nickel Steels

Charpy test results Trans. temp,

Refer- Gage, Weld Notch o F (o C) ence Steel in. (mm) process Postheat location 15 ft-lb (20 J) Notes 38 2¼% Ni ½ (13) None Base metal -130 (-90) N1600 (870)

SMAW No Fusion line -135 ( -95) SMAW No HAZ-:fine gr. -140 (-95) SMAW No HAZ-outer edge -130 ( -90)

38 2¼% Ni 1 (25) None Base metal -100(-75) N1600 (870), Tll50 (620) 1 (25) SMAW No Fusion line -130 ( -90) 1 (25) SMAW No HAZ-:fine gr. -120 (-85) 1 (25) SMAW No HAZ-outer edge -50 (-45)

Dropweight test results NDT, ° F (° C)

38 3½%Ni ½ (13) None Base metal -140 (-95) N1650 (900), Tl050 (565) ½ (13) SAW No Fusion line -130 (-90) Longit. to weld ½ (13) SAW 1050 (565) Fusion line -160 (-105) Longit. to weld ½ (13) SAW No B.P. fracture -150 (-100) Transv. to weld ½ (13) SAW 1050 (565) B.P. fracture -140 ( -95) Transv. to weld l9116 (40) None Base metal -140 (-95) N1650 (900), T1050 (565) l9116 (40) SAW 1050 (565) Fusion line -130 (-90) Longit. to weld l9l1s (40) SAW 1050 (565) W.M. fracture -130 (-90) Transv. to weld

Kinzel test results

38 3½% Ni 'Is (22) E8016-C2 No 'Is (22) E8016-C2 1100 (595) 'Is (22) E8016-C2 1100 (595) 'Is (22) E8016-C2 1100 (595)

the designer is aware that low fracture toughness in­dicates a small critical flaw size for unstable fracture, he must also have some information on the fatigue crack growth rates at low service temperatures, since they determine how fast a subcritical-size flaw will grow to the critical size.

Summary The low-nickel steels covered by the ASTM speci­

fication A203 can meet the notch toughness require­ments of A593 in the prescribed normalized condi­tion. Proper notice should be taken that valuable gains in toughness can be obtained by quenching and tempering rather than normalizing. Since there is some doubt that the 15 ft-lb (21 J) specification pro­vides assurance of safe service performance, the extra margin of toughness available by heat treatment may extend the usefulness of these steels.

Cold forming may raise the Charpy test transition temperature above that permitted, but thermal stress relief restores most of the toughness. Available data gave no indication that welding induces a serious loss of notch toughness in the region of the weld.

The Higher Nickel Steels

Specifications The higher nickel steels include grades that range

between 5 and 9% and which do not contain major amounts of such alloy elements as Cr, V, Mo, etc. (i.e., not over about 0.5%). These grades are covered by ASTM Specifications A353, A553, and A645. The

1 % Lat. contr., o F (o C)

Transv. to weld -120 ( -85) N1650 (900) Transv. to weld -150 (-100) N1650 (900) Transv. to weld -160 (-105) WQ1650 (900), T1150 (620) Transv. to weld -165 (-110) WQ1650 (900), T1150 (620)

composition limits, thickness range and recommend­ed heat treatments for thee{e grades are listed in Table 10. The mechanical properties expected of these grades are listed in Table 11. The toughness re­quirements listed in this table are found both in the respective ASTM grade specification and also in ASTM Specification A593.

It should be noted here that the A353 specification has the same chemical analysis as the A553 Type I,

1111----- ........................... --.---------, ., 60

z

A533-8 SINI Spee Type "3l'' WOI. long. Orientation Test Frequency 6111 CPM Cyclic load Range &-30.11111 a

ll~O---::..,!:--'--i=-...._,':-'-:!:-'::".!::----::!..,..::--------'10◄ ,., 40 60 801111 _,

Stress Intensity Factor Range, 6K, kSI 'llii:

Fig. 19-lnfluence of temperature on the daldN vs. t..K relationship (3T WOL specimens)

Cryogenic Nirkel Steels 19

Table 10-ASTM Specifications Applicable to the Higher Nickel Steels

A. Composition Requirements Specifica- hemical composition

tion C Mn p s Si Ni Mo Al N A353 0.13 0.90 0.035 0.040 0.15-0.30 8'.5-9 .5 A553

Type I 0.13 0.90 0.035 0.040 0.15-0.30 8.5-9.5 Type II 0.13 0.90 0.035- 0.040 0.15-0.30 7.5-8.5

A645 0.13 0.30-0.60 0.025 0.025 0.20-0.35 4.75-5.25 0.20-0.35 0.05-0.12 0.020

B. Heat Treatment and Thickness Requirements Specification A353

Thickness 2 in.b Double normalized and tempered: 1) 1650 ± 25° F 1 h/in. thickness, air cool;

· 2) 1450 ± 25° F 1 h/in. thickness, air cool; 3) 1050-1125 1 h/in. thickness, air cool or water quench at rate not less than 300° F /h.

A553 Type I or II

2 . b m. Quenched and tempered: 1) 1475 ± 25° F 1 h/in. thickness, water quench; 2) 1050-1125° F 1 h/in. thickness, air cool or water quench at rate not less than 300° F /h.

A645 Hardened, temperized and reversion annealed: 1) 1575-1675° F, 1 h/in. thick­ness, water quench to below 300° F; 2) 1275 to 1400° F, 1 h/in. thickness, water quench to below 300° F; 3) 1150-1225° F 1 h/in. thickness, water quench or air cool to below 300° F.

" Heat analysis, check analysis has broader limits. Max. except where range is indicated. b Normal limit due to processing facilities required. There is no maximum thickness limit if property specifications can

be met.

Table 11-Mechanical Property Requirements for the Higher Nickel Steels•

Yield strength, Tensile strength, Specification ksi ksi A353 75 100-120 A553

Type I 85 100-120 Type II 85 100-120

A645 65 95-115

<> Minimum requirement unless range is indicated.

but the A553 specification also contains a lower nick­el (nominal 8%) Type II analysis. In addition to the grades listed here, there are some other proprietary materials, not under current ASTM specifications, which would fall into this category on the basis of their general chemistry and intended service applica­tions. These grades are not considered in this general discussion of the ASTM grade materials.

Tensile Properties The mechanical properties listed for these grades

in Table 11 show them to be substantially stronger than the lower nickel grades and without loss of ten­sile ductility. This increased strength makes them more attractive than the A203 grades, and leads to their application in some structures where other grades would provide adequate toughness but at sub­stantially increased section thicknesses because of the lower strength of the steel. It should be noted in this regard that A645 is nominally lower in yield strength than the other grades, although not substan­tially so (10 ksi lower than A353 and 20 ksi less than A553). As with the lower nickel steels, the effect on specific types of service and fabrication conditions on

Transverse specimen lateral Elong. in 2 in., expansion (mils)

% at -275° F at -320° F 20.0 15

20.0 15 20.0 15 20.0 15

properties will be considered. Included in these are the effects of heat treatment and thickness, service temperature and fabrication operations, such as cold forming and welding.

Effect of Heat Treatment and Thickness. Of the four grades considered in this section, A353 (double normalized and tempered 9% Ni steel) was historical­ly the earliest to be developed, and is still used today, although more so in Europe than on the American continent. The mechanical properties will normally exceed the specification, with yield points in the range of 90 ksi (620 MPa) and tensile strengths in the range of 110 ksi (760 Mpa). The normal variations in yield and tensile strength around these values does not appear to be due to section size effects. The spread in yield and tensile strengths at room temper­ature for this grade are also seen in Fig. 20.

The 9% nickel steel is more commonly used quenched and tempered to the A553 Type I specifica­tion which has a yield strength about 10 ksi (69 MPa) higher than A353 but much the same tensile strength. This can be seen both in the data of Table 12 and for the selected heats reported in Table 13. These heats were given heat treatment to either A353

20 WRC Bulletin 205

OF -200 -100 0 100

180 A353

160

i. 2

I I

140

0

0 0 120;;

ll 0

• ► 700 100

600 0..

80

!SOO -200 -150 -100 -50 0 50

Testing Temperature - °C

Fig. 20-Range of yield strengths and tensile strengths reported for double normalized and tempered 9 % Ni steel (A353)

or A553 Type I specifications and the properties in the two conditions determined for comparison. In every case but one, the yield strengths of the A353 double normalized and tempered specimens are at least 10 ksi (69 MPa) less than the A553 Type I quenched and tempered specimens. The tensile strengths of the two grades are almost identical.

The normal spread of tensile properties for A553 Type I steel is seen in Fig. 21 and in Table 12. The expected yield point will be a little over 100 ksi (690 MPa) and the expected tensile strength is somewhat over 110 ksi (760 MPa) (essentially the same as A353). The properties of the A553 Type II (8% Ni steel) are not nearly so well established. The two heats reported here (Table 12) appear to have yield strengths slightly less than the other two grades. The A645 material (5% Ni + ¼% Mo steel) does not have quite so high yield strength as the other steels, nor­mally around 85 ksi (585 MPa), while the tensile strength is around 105 ksi (720 MPa). Comparison of the data for A645 in Table 12 with the specifications in Table 11 shows that they are above the required strength level by a good margin. The expected spread in the room temperature tensile properties for A645 is also shown in Fig. 22. As was true for the A353, nei­ther of these two steels seems to be sensitive to sec­tion sizes as far as strength is concerned.

Comparison of the heat treatments for the three grades considered here, i.e., A353, A553, and A645, reveals that the heat treatments applied are increas­ingly more complex. While this may result in some

•F -300 -200 -100 0 100 h 180

1200 \, A553TypeI

1100' 160

i. o c. a ~, A

E 0 14'0 0 C CD c. .. D'S 900

8 8 .!! ·;;;

0 C

120~ ~ 800

~o

"Cl C 0

"Cl 'ii

0 ~8 ► 700 100

600 ':o~

80

500 -200 -150 -100 -50 0 50

Testing Temperature -•c

Fig. 21-Range of yield strengths and tensile strengths reported for quenched and tempered 9 % Ni steel (A553 Type I) •

i. :E I

s::: '6,

! Di CD

~ C

~ "Cl C 0

"Cl "ii ~

-300· -200 OF

-100 0 100

1200 A645

1100

800 0 ilnlile

0 i 0

700 0 ....

0

600 Yield I~ Slr .. Qth I,

~o 500 0~ ~

0-

-200 -150 -100 -50 0 50 Testing Temperature - 'C

180

160

140

100

80

Fig. 22-Range of yield strengths and tensile strengths reported for 5% Ni-¼% Mosteel(A645)

Cryogenic Nickel Steels 21

Table 12-Typical Room Temperature Tensile Properties of the Higher Nickel Steels

Refer- Gage, Yield strength, Tensile strength, Elong. in 2 in., Red. of ence Grade in. (mm) ksi (MPa) ksi (MPa) % area,% 39 A353 1.0 (26) 72.2 (498) 103 (712)

1.2 (30) 106 (734) 115 (793) 1.2 (30) 103 (707) 122 (840)

30 A353 0.63 (16) 90. 7 (625) 111 (765) 28 69.9 0 .63 (16) 94 .2 (649) 115 (792) 27 69.4 0.75 (19) 83 .2 (573) 113 (778) 26 68.6

34 A353 1.3 (33) 88 .1 (607) 98 .9 (681) 23.7 63.7 2.6 (65) 99.6 (686) 108 (744) 20.0 63.0

40 A353 · 0.38 (10) 89 .5 (617) 109 (751) 1.0 (25) 89.0 (613) 112 (772)

92 .0 (634) 107 (737) 41 A353 0 .31 (8) 94 .4 (650) 105 (723) 35.8

0 .59 (15) 88.7 (611) 107 (737) 44.0 42 A353 0 .95 (24) 91 (627) 111 (765) 42.0 43 A353 0. 75 (19) 95 (655) 121 (835) 27 64 44 A353 0. 75 (19) 104 (717) 116 (799) 32

40 A553I 0 .38 (10) 105 (723) 111 (765) 0.75 (19) 86 .1 (593) 110 (758) 1.0 (25) 104 (717) 111 (765) 3 .0 (76) 92.3 (636) 104 (717)

43 A553I 0.75 (19) 98 (675) 107 (735) 22 75 44 A553I 0.75 (19) 115 (792) 119 (820) 28 42 A553I 0 .50 (13) 110 (755) 116 (800) 31

0 .63 (16) 102 (700) 109 (750) 43 0 .90 (23) 105 (720) 112 (770) 29 0 .90 (23) 105 (720) 111 (765) 26 0 .90 (23) 101 (695) 109 (750) 28 0.95 (24) 99 (685) 105 (725) 31 1.0 (25) 107 (735) 114 (788) 26 1.19 (30) 103 (710) 112 (770) 24 1.38 (38) 100 (690) 111 (765) 22 1.38 (35) 113 (780) 109 (750) 28 2 .75 (70) 94 (650) 118 (810) 33 3 .0 (75) 91 (630) 114 (785) 35

27 A553I 0 .80 (20) 110 (760) 117 (805) 24 69 0 .90 (23) 106 (730) 111 (765) 25 69 0 .90 (23) 111 (770) 117 (810) 22 0 .90 (23) 103 (710) 112 (775) 25 0 .90 (23) 104 (720) 111 (770) 27 0 .90 (23) 105 (725) 114 (790) 25 0 .90 (23) 104 (715) 111 (765) 26 75 0 .90 (23) 102 (705) 110 (760) 27 75 0 .90 (23) 99 (680) 106 (735) 26 72 0 .95 (24) 99 (680) 105 (725) 31 1.0 (25) 103 (710) 112 (775) 28 1.0 (25) 102 (705) 114 (785) 26 1.0 (25) 104 (715) 115 (790) 27 1.0 (25) 102 (705) 110 (760) 26 1.19 (30) 104 (715) 110 (760) 25 1.19 (30) 102 (705) 109 (755) 26 75 1.19 (30) 104 (715) 112 (775) 22 1.19 (30) 96 (660) 106 (735) 28 1.38 (35) 107 (740) 115 (795) 24 1.38 (35) 102 (700) 111 (765) 29 1.57 (40) 104 (715) 112 (770) 28

30 A553I 0 .63 (16) 103 (710) 112 (770) 26 0 .63 (16) 110 (758) 117 (806) 24 0 .75 (19) 94 (648) 111 (765) 28

45 A553I 0.25 (6) 107 (737) 114 (785) 21 39 A553I 1.0 (26) 94 .4 (651) 103 (707)

1.0 (26) 97 (669) 104 (720) 1.19 (30) 109 (749) 115 (794) 1.19 (30) 114 (785) 120 (830)

46 A553I 1.0 (25) 107 (737) 115 (795) 29 1.0 (25) 104 (715) 119 (820) 20

35 A553I 2.0 (51) 97 (670) 109 (750) 29 72 3.0 (76) 87 (600) 110 (755) 27 66

40 A553II 0.38 (10) 97 .2 (670) 107 (737) 24 66.8 0. 75 (19) 99 .3 (684) 106 (730) 22.5 68.2

31 A553I 0 .50 (13) 94.8 (654) 110 (760) 25 72 0 .50 (13) 107 (740) 113 (780) 34 58 0 .50 (13) 108 (747) 119 (820) 33 49 0 .50 (13) 110 (760) 118 (815) 34 56 0. 75 (19) 102 (700) 111 (765) 42 64

22 WRC Bulletin 205

Table 12 (continued)

Refer- Gage, Yield strength, Tensile strength, Elong. in 2 in., Red. of ence Grade in. (mm) ksi (MPa) ksi (MPa) % area, % 28 A645 0 .19 (5) 89 (610) 101 (695) 23

0 .25 (6) 69 (475) 104 (715) 28 0 .25 (6) 95 (655) 105 (725) 24 0 .38 (10) 87 (595) 101 (695) 36 0 .50 (13) 90 (620) 105 (725) 36 0 .63 (16) 90 (620) 106 (730) 74 0 .63 (16) 86 (590) 102 (700) 0.63 (16) 90 (620) 105 (725) 29 72 0 .63 (16) 83 (570) 104 (715) 30 69 0.75 (19) 72 (495) 110 (760) 36 72 0.75 (19) 75 (515) 103 (710) 29 71 1.0 (25) 87 (595) 110 (760) 31 75 1.0 (25) 84 (580) 106 (730) 28 1.0 (25) 81 (555) 102 (700) 30 71 1.0 (25) 85 (585) 108 (740) 30 73 1.0 (25) 84 (575) 103 (710) 32 74 2 .0 (51) 75 (515) 110 (760) 29 69

35 A645 1.0 (25) 71 (490) 100 (690) 32a 77 1.5 (38) 70 (485) 101 (695) 35 71

a 1 in. gage length.

Table 13-Strength and Toughness of 9% Nickel Steel Treated to both A353 and A553 Type I Specificationsa

Steel and gage, Heat in. (mm) treatment

1) 1.0 (26) NNT QT

2) 1.2 (30)b NNT QT

3) 1.2 (30)b NNT QT

4) 0 .63 (16) NNT QT

5) 0.63 (16) NNT QT

6) 0. 75 (19) NNT QT

7) 0.38 (10) NNT QT

8) 0.75 (19) NNT QT

a Data from Refs. 30, 40, and 44. b Longitudinal properties.

Yield strength, ksi (MPa) 72 .2 (498) 94.4 (651)

106 (734) 108 (744) 103 (707) 114 (785) 90.7 (625)

103 (710) 94.2 (649)

110 (758) 83 .4 (575) 94 (648) 89 .5 (617)

105 (723) 104 (717) 115 (792)

increase in strength properties, for example, A553 Type I compared. to A353, the primary purpose of the complex heat treatments is not related to strength but rather to toughness. As described earlier in this report, such treatments develop the austenite-ferrite­carbide structures that are optimum from the tough­ness viewpoint.

Effect of Temperature. Although these steels may be widely applied, it is evident from the temper­atures at which toughness tests are specified for the steels that intended service is down to as low as -320° F (-196° C). While this is a convenient test temperature because liquid nitrogen can be used as a test medium, in fact the majority of the present ap­plications appear to be in the LNG storage and trans­port fields, where temperatures do not reach much below -270° F (-168° C). The fracture toughness

Drop-weight C. energy tear test energy

Tensile strength, Elong. in at -196° C, at -196° C, ksi (MPa) 2 in.,% ft-lb (J) ft-lb (J) 103 (712) 27 (37) 103 (707) 72 (97) 115 (793) 50 (67) 115 (794) 38 (52) 122 (840) 45 (61) 120 (830) 36 (49) 111 (765) 28 36 (49) 1379 (1875) 112 (772) 26 50 (68) 2094 (2848) 115 (792) 27 39 (53) 800 (1088) 117 (806) 24 29 (39) 991 (1348) 113 (779) 26 33 (45) 649 (883) 111 (765) 28 54 (73) 2334 (3174) 109 (751) 111 (765) 118 (813) 32 27 (37) 800 (1088) 119 (820) 28 35 (48) 2534 (3446)

test temperature of -275° F (-170° C) for A645 and A553 Type II is therefore appropriate to service. As with the lower nickel materials, the strengths of the steels increase with decreasing temperature. The cryogenic temperature properties of the steels are shown in Table 14 and changes in mechanical proper­ties of A353, A553 Type I, and A645 with decreasing temperature are shown on_Figs. 20-22. As can be seen from these figures, both the yield and tensile strengths of the steels increase modestly down to -100° F (-73° C) and then more rapidly down to -320° F (-196° C). In general, the yield strength at -320° F is about 40% greater than that at room tem-perature for A353 and A553 Type I, while the tensile strength is 50% greater. The increase in yield and tensile strength for A645 is about 50% and 60% re­spectively. The total elongation and reduction of area

Cryogenic Nickel Steels 23

Table 14-Typical Cryogenic-Temperature Tensile Properties of the Higher Nickel Steels

Refer- Gage, Temperature, ence Grade in. (mm) o F (o C)

40 A353 0 .38 (10) -320 ( -196) 0 .50 (13) -320 (-196) 1.0 (25) -320 ( -196)

39 A353 1.0 (26) -320 ( -196) 1.0 (25) -320 (-196) 1.19 (30) -320 (-196) 1.19 (30) -320 (-196)

30 A353a 0 .63 (16) -320 (-196) 0 .63 (16) -320 ( -196) 0 .75 (19) -320 (-196)

40 A5531 0.38 (10) -320 (-196) 0.75 (19) -320 ( -196) 1.0 (25) -320 ( -196)

-300 ( -184) 3.0 (76) -320 ( -196)

35 A5531 2.0 (51) -320 (-196) 3.0 (76) -320 ( -196)

39 A5531 1.0 (25) -320 ( -196) 1.0 (25) -320 (-196) 1.2 (30) -320 (-196) 1.2 (30) -320 (-196)

30 A5531 0 .63 (16) -320 (-196) 0.63 (16) -320 (-196) 0 .63 (16) -275 (-170) 0.75 (19) -320 ( -196)

27 A5531 3.0 (75) -320 (-196)

40 A55311 0 .38 (10) -320 (-196) 0. 75 (19) -320 ( -196)

28 A645 0.63 (16) -320 ( -196) 0 .75 (19) -320 (-196)

-275 (-170) 0. 75 (19) -320 (-196)

-275 (-170) 1 .') (25) -320 (-196)

35 A645 1.0 (25) -320 (-196) 1.5 (38) -320 ( -196)

a Longitudinal properties.

are little changed as temperature decreases. In most materials, even cryogenic materials, the

cryogenic temperature tensile properties have not been until recently of particular interest as the em­phasis has been on impact toughness at low tempera­tures and design from the strength viewpoint has been based on ambient properties. With this class of steels, however, the cryogenic strength levels are sig­nificant. First, the steels are substantially stronger at low temperatures without loss of ductility, and for LNG service at least, are not loaded to any extent until they are at the service temperature. A proposed ASME Code Case recognizes the increased cryogenic strength of A353, A553, and A645 in terms of higher allowable stresses. Secondly, in order to characterize their toughness, fracture mechanics parameters rath­er than simple impact tests are increasingly em­ployed. In application of these parameters, the cryo­genic yield strength must often be known in order to assess allowable and critical flaw sizes.

Effect of Cold Deformation and Aging. Data on the effect of straining or aging at subcritical tempera­tures on the tensile properties of the steels are mea­ger. Although some surveys of strain aging have been

Yield strength, Tensile strength, Elong. in C. Energy, ksi (MPa) ksi (MPa) 2 in.,% ft-lb (J) 123 (847) 169 (1164) 125 (861) 170 (1171) 133 (916) 169 (1164) 115 (795) 158 (1087) 27 (37) 148 (1022) 180 (1239) 40 (54) 141 (972) 170 (1170) 50 (67) 143 (989) 177 (1220) 45 (61) 141 (971) 171 (1178) 29 42 (57) 141 (971) 175 (1206) 28 39 (53) 136 (937) 172 (1185) 28 33 (45)

141 (971) 168 (1157) 124 (854) 168 (1157) 153 (1054) 163 (1123) 125 (861) 135 (930) 125 (861) 166 (1144) 134 (923) 169 (1164) 26 49 (67) 122 t841) 164 (1130) 31 81 (110) 137 (947) 154 (1060) 141 (970) 155 (1067) 152 (1050) 167 (1150) 160 (1100) 170 (1170) 139 (958) 174 (1199) 29 50 (68) 158 (1089) 171 (1178) 28 29 (39) 140 (965) 150 (1033) 25 43 (58) 129 (889) 175 (1206) 26 54 (74) 130 (896) 178 (1226) 29 86 (117)

138 (951) 161 (1109) 149 (1027) 159 (1096)

132 (909) 164 (1130) 33 44 (60) 114 (785) 166 (1144) 29 37 (50) 93 (641) 148 (1020) 26 48 (65)

106 (730) 160 (1102) 31 43 (58) 99 (682) 141 (971) 28 57 (78)

126 (868) 163 (1123) 31 36 (49) 108 (744) 163 (1123) 31 64 (87) 106 (730) 165 (1137) 30 21 (29)

undertaken, 27,28 the emphasis has been on toughness rather than strength. One study of A35329 has shown that extended aging in the 700-1000° F (371-538° C) range may produce some increases in yield and ten­sile strength, but the aging times involved are beyond those normally employed in treatment of the steel. The A353 and A553 specifications require that mate­rial heated for forming be heat treated after forming, thus eliminating the concern about strain aging.

A study of the A645 material 28 has shown that aging for as long as 8 hr at 550-1100° F (288-538° C) produces no strength changes. A strain of 5% will in­crease the yield point of this material 35% and the tensile strength 7%, with a modest decrease in tensile elongation (to 25%). Stress relief at 1100° F recovers original properties.

Effect of Welding. The more important concern from the fabrication viewpoint is the behavior of weldments. In terms of strength, the weld consum­ables normally employed tend to undermatch the base metal, producing weld metal failures in weld­ment tensile tests. The welding processes and con­sumables are generally selected to provide good weld metal and heat-affected zone toughness, and thus the

24 WRC Bulletin 205

weld metals are usually austenitic instead of ferritic. The yield and tensile strengths of these deposits are usually less than A353 or A553 and may be less than A645. Typical weld metal and process combinations for the steels are gas metal-arc welds made with Inco­nel 82, 92, 182, or 625 and shielded metal-arc welds made with Inco-weld A and B or lnconel 112. There are a number of other proprietary electrodes of simi­lar composition which may also be used. On a much more limited scale, submerged arc welds or welds made with ferritic electrodes have been employed.

A survey of the properties of these weldments is found in Table 15. As may be readily seen, the A645 weldments fail in the base metal a fair proportion of the time, indicating that the weld metal sometimes overmatches the plate. On the other hand, the A553 Type I weldments almost never fail in the base plate, indicating that the weld metal undermatches the plate. In spite of this undermatch, however, only on rare occasions does the tensile strength of the weld­ment fall below the minimum specified for the plate (95 ksi for A645 and 100 ksi for A353 or A553 Type I).

Notch and Fracture Toughness The higher nickel steels, like the lower nickel

steels, have been evaluated by Charpy impact tests for many years, and impact specifications for these steels are covered both in their own specifications and, as indicated in Table 11, in ASTM specification A593. In addition to this test, a number of different types of fracture mechanics tests have also been ap­plied to these steels. Current design procedures favor the use of these more sophisticated tests, but Charpy impact tests are still the basis for material purchase.

Charpy Test Results. The Charpy impact tough­ness of these steels is normally quite good, and the criteria applied to them are relatively severe. Where­as the A203 Grade D is required to produce a Charpy impact toughness of 13 ft-lb (17 .6 J) at the lowest service temperature, -150° F (-101 ° C), the higher nickel steels must provide 15 roils (0.38 mm) lateral expansion at either -275 or -320° F (-170 or -196° C), about equivalent to 25 ft-lb (33.9 J) impact ener­gy.27,28 The specification of lateral expansion as a toughness criterion for the steels rather than impact energy reflects a concern for notch ductility as well as notch strength, and is set at a severe level for this material because the yield strengths, tensile strengths, and thus allowable stress levels employed are higher than those used for the lower nickel steels. In spite of the severity of the requirement, however, almost all of the A553 Type I and A645 used today will show toughnesses well above this level. Normal lateral expansions at -320° F (-196° C) for A553 Type I range from 25 mils (0.64 mm) to 80 roils (2.03 mm) or an equivalent of about 50 ft-lbs (67.8 J) to 140 ft-lb (190 J). Toughnesses for A645 at -275° F (-170° C) will normally be between 20 mils (0.51 mm) and 40 mils (1.02 mm) which is approximately

equivalent to a range between 30 ft-lb (40.6 J) and 60 ft-lb (81.3 J). In general neither A553 Type I nor A645 shows much sensitivity to section size as far as Charpy impact toughness is concerned; however, when A553 Type I sections exceed 2 in. (51 mm) and A645 sections exceed 1.5 in. {12. 7 mm), toughnesses tend to approach the specification limit. The impact toughness distribution for a number of heats of A353 and A553 Type I at -320° F (-196° C) is shown in Fig. 23 and for A645 at -275° F (-170° C) and -320° F (-196° C) in Fig. 24. It should be noted that A645 specifications establish -275° F (-170° C) to be the appropriate test temperature for this steel. Because it competes with A353 or A553 Type I in some applications, however, tests are sometimes also run at -320° F (- 196° C). At this temperature, nor­mal lateral expansions range between 10 and 30 roils (0.25 and 0.76 mm), equivalent to 15-45 ft-lb (20-61 J). Thus many heats of A645 also meet the Charpy impact specification for A353 and A553 Type I.

An interesting aspect of the Charpy impact tough­ness behavior of A353 and A553 Type I material is seen in Fig. 25 which includes data for three of the steels in Table 13. In this study, 30 the impact tough­ness at -320° F (- 196° C) was found to be related to the amount of retained austenite present in the steel, illustrating a point mentioned earlier in this report. Moreover, the Charpy toughness differences between heats and heat treatment appear to be related to the retained austenite content more than to any other single factor. Thus both the toughest and least tough materials were A553 Type I, and for the least tough heat of A553 Type I (No. 5 on Table 13), the A353

· heat treatment produced better toughness apparent­ly because it produced an increased amount of re­tained austenite. The dynamic tear toughness data seen here follow the same trend, and are discussed in the next section.

Drop-Weight and Dynamic Tear Test Results. Drop-weight test data for A353, A553 Type I, and A645 are more limited than for the lower nickel steels because NDT temperatures are normally below the minimum specified service temperature. In practice the test becomes a confirmation that no-break per­formance occurs at -320° F (-196° C) for A353 and A553 Type I, and at -275° F (-170° C) for A645. Test data for a number of heats have not only estab­lished this to be generally true, 27,28 but explosion bulge tests on three heats of A55331 have also estab­lished that the FTE temperature is at or below -320° F (-196° C).Welded plates generally show an FTE temperature at or below -320° F (-196° C) as well. Tests on A645 show that NDT is below -275° F (-170° C).

Tear behavior in the drop weight tear test has been obtained 30 to a limited extent for both A353, A553 Type I, and A645 steels. The data for A353 and A553 Type I are seen in Table 13 and Fig. 25. In general, tear energies for the A553 Type I are somewhat above those for A353, but there are other factors, such as

Cryogenic Nickel Steels 25

Table 15-Typical Room-Temperature Transverse Tensile Properties of the Higher Nickel Weldments

Reference Gage, Heat input, Welding Failure Tensile strength and grade in. (mm) Electrode and process kJ/cm position location ksi (MPa)

34 1.6 (33) Inconel 82, GMA 100 (689) 2.6 (65) Inconel 112, GMA 101 (696)

40 0.38 (10) Inco-Weld A, SMA 104 (717) 0 .38 (10) Inconel 92, G MA 101 (696)

40 0.38 (10) Inco-Weld A, SMA 106-(730) 0. 75 (19) Inco-Weld A, SMA 108 (744) 0 .38 (10) Inconel 92, GMA 106 (730) 0. 75 (19) Inconel 92, GMA 108 (744) 0.25 (6) Inconel 112, SMA 108 (744)

Inconel 112 119 (820) 0.38 (10) Inconel 112 108 (744) 0.5 (13) Inconel 112 115 (792)

Inconel 112 115 (792) 1.0 (28) Inconel 112 115 (792)

27 0.9 (23) Inco-Weld A, SMA 10-12 Flat WM ~01 (700) Y-Weld B, SMA 9-19 Flat WM 110 (760) Y-Weld B, SMA 17-36 Vert. WM 109 (750) Y-Weld B (M), SMA 9-19 Flat WM 114 (785) Y-Weld B (M), SMA 17-36 Vert. WM 112 (775) Nic-70, SMA 9-19 Flat WM 111 (765) Nic-70, SMA 17-36 Vert. WM 107 (735) Nic-50, SMA 9-19 Flat WM 108 (745) Nic-50, SMA 17-36 Vert. WM 108 (745) Nia-37, SMA 14-17 Flat WM 106 (730) Nia-37, SMA 30--39 Vert. WM 102 (705) 12 Ni-15 Cr, SMA 9-19 Flat WM 108 (745) 12 Ni-15 Cr, SMA 17-36 Vert. WM 103 (710)

27 0.9 (23) Yawata 92, GMA 13-18 Flat WM 99 (685) Y awata 92, GMA 12-16 Horiz. WM 105 (725) Yawata 82, GMA 13-18 Flat WM 108 (745) Yawata 82, GMA 11-14 Horiz. WM 102 (705)

0.9 (23) Inconel 025, GMA 13-18 Flat WM 116 (800) Inconel 025, GMA 11-15 Horiz. BM 115 (795) MGS-70NCb, GMA 13-18 Flat WM 99 (685) MGS-70NCb, GMA 32-37 Vert. WM 98 (670)

0.95 (24) NIA-37, GMA 14 Flat WM 99 (680) NIA-37, GMA 8 Horiz. WM 103 (710)

0.78 (20) Avtrod 37, GMA 11-16 Flat WM 103 (710) Avtrod 37, GMA 59-63 Horiz. WM 109 (750)

0. 75 (19) Nittetsu Filler 196, Flux 40 Flat WM 109 (750) 10, SA

Nittetsu Filler 196, Flux 11-13 Horiz. WM 112 (770) 10,SA

45 0.25 (6) Inconel 92, GMA Flat WM 104 (720) Inco-Weld B, SMA Vert. WM 104 (720)

47 0 .63 (16) Ni-20 Cr-4 Mn-C, GMA (dip) Flat WM 104 (720) Ni-20 Cr-4 Mn-C, GMA (globular) Flat WM 119 (820) Ni-20 Cr-4 Mn-C, GMA (spray) Flat WM 110 (760) Ni-20 Cr-4 Mn-C, GMA (pulsed) Flat WM 102 (705)

35 2 (51) Inco-weld B, SMA 30 Flat WM 107 (735) Inco 82, GMA 51 Flat WM 80 (555)

28 0.25 (6) Inconel 92, GMA Vert. WM 109 (750) Inconel 92, GMA 6.7 Vert. Flaw 96 (660) Inconel 92, GMA 16 Vert. WM 97 (670) Inconel 92, GMA 9.5 Horiz. BM 110 (760)

0 .63 (16) Inconel 92, GMA 15 .4 Horiz. WM 102 (700) Inconel 92, GMA 15.7 Vert. WM 100 (690) Inconel 92, GMA 51 Vert. WM 106 (730)

0.75 (19) lnconel 92, GMA 19.7 Vert. BM 104 (715) Inconel 92, GMA 31.2 Vert. BM 101 (695) Inconel 92, GMA 68 Vert. WM 101 (695)

1 (25) Inconel 92, GMA 11 Horiz. WM 100 (690) Inconel 92, GMA 22.8 Vert. WM 98 (675) Inconel 92, GMA 31.4 Vert. BM 104 (715)

1.5 (38) Inconel 92, GMA 19 Vert .. BM 101 (695) 0.25 (6) Inconel 625, GMA 11.4 Horiz. BM 113 (780) 1 (25) Inconel 625, GMA 12.6 Horiz. BM 107 (740)

Inconel 625, GMA 35.4 Vert. BM 104 (715) 0.25 (6) Inco-Weld A, SMA 9.8 Vert. WM 92 (635) 0.63 (16) Inco-Weld A, SMA 9.8 Vert. WM 98 (675) 0. 75 (19) lnconel 35 Vert. WM 85 (585)

182, SMA 92 (635)

26 WRC Bulletin 205

Table 15 (continued)

Reference and grade

Gage, in. (mm) 0 .63 (16) 0 .25 (6) 0 .63 (16) 0 .63 (16) 1 (25) 0 .25 (6) 0 .63 (16) 0.63 (16) 1 (25)

"Preheat to 100° F (40° C).

Ekctrode and process McKay 9 Ni, SMA Cryo-Therm," SMA Cryo-Therm,• SMA Cryo-Therm," SMA Cryo-Therm," SMA Yawata,• B-SMA Yawata,• B-SMA Inconel 82, SA Inconel 82, SA

retained austenite content, that may be more signifi­cant. If these specimens can be considered roughly equivalent to a % in. (19. mm) thick dynamic tear specimen, comparison with a ratio analysis diagram would place these plates in the elastic-plastic or plas­tic fracture region in every case but one. On the basis of these tests, the Ye point for the plates tested should be about -200° F (-129° C) for A353, and about -300° F ( -184 ° C) for A553 Type 1.

The drop weight tear test data for A645 transverse specimens show full shear fractures for thin, 0.19 in. (4.9 mm) and 0.25 in. (6 mm), specimens and 50% shear for heavier, 0.62 in. (16 mm) and 0.75 in (19 mm) specimens at -250° F (-157° C). In the dynam­ic tear test, the Ye point for 0'.62m (16 mm) and 0. 75

ft-lb 0 20 40 60 80 100 120 140 160

2.0

1.8 E 0 0

~ 1.6 0

0

C oo ocfe.,0•3 60 0 0 0 0000 ·;;; oo oo oo ~o 8. 1.4 i io~'a Cb

~ oooo 0 0

50 0

0 1.2 0 0 .!!! ... 0 0 ·e ~

.9 1.0 40 >, a. ... _g 0.8

30 l.)

0.6 A553 Type! 0 -196•c

0 20 0.4

02 10

o.__ ....... _ .......... _._ .......... _.__....,_--'._ ......... _.__.....,__o 0 20 40 ED W 100 la::> 140 ta:> IW 200

Chorpy Impact Energy- J

Fig. 23-Relation between Charpy V-notch test energy absorption and lateral expansion in A553 Type I steel tested at -320° F (-196° C)

Heat input, kJ/cm

27.5

59 51

11 19.2

Welding position Vert. Vert. Horiz. Vert. Vert. Vert. Vert. Flat Flat

Failure location

BM WM BM WM WM WM WM WM

BM,WM

Tensile strength, ksi (MPa) 110 (760)

96 (660) 107 (740) 98 (675)

100 (690) 103 (710) 108 (745) 99 (680)

107 (740)

in. (19 mm) specimens was below -250° F and shelf energies were equivalent to 8000-12000 ft-lb (10,800-16320 J) in 1.0 in. (25 mm) specimens.

Fracture Toughness Test Results. As a result of the widespread use of the higher nickel steels in cryo­genic service, an increasing amount of fracture tough­ness data have been produced on these grades over the past five years or so. Most of the data fall into two categories, the Kc or Kie data produced by com­pact tension or bend specimens made to satisfy the requirements of ASTM E399-72, or COD specimens made to meet the requirements of BSI DD19-72. In addition, a number of specimens not specifically de­signed to meet these standards but producing Kc or COD data, have also ·been tested. A compilation of

ft-lb 0 20 40 60 80 100 120 140 160

2.0

1.8

0.6

0.4

0.2

C

C

A645 o-196 •c C-170 •c

80

70

-60

50

40

30

20

10

o._ ....... _ ......... --''- ......... ____,'-_.__..,___.__.___.____,o

0 20 40 ED 80 100 120 140 IED 180 200 Chorpy Impact Energy - J

en

·e

Fig. 24-Relation between Charpy V-notch test energy absorption and lateral expansion in A645 steel tested at -275 apd -~20° F (-170 and -196° C)

Cryogenic Nickel Steels 27

Table 16-Fracture Toughness Properties of the Higher Nickel Steels

K values Mean Min.

Refer- Gage, Test Test temp., ksiv'in. ksiy'in. ence Steel in. (mm) method o F (o C) Criterion (MPay'm) (MPavm) 34 A353 1.3 (33) Bend -312(-191) K. 124 (136) 122 (134)

-280 (-175) K. 168 (185) 168 (185) -260 (-162) K. 160 (176) 154 (170)

1.6 (41) Wide -260 ( -162) K.• 300 (330) 274 (301) plate

2.6 (65) Bend -305 ( -187) K, 194 (213) -260 ( -162) K, 200 (220) 199 (219)

43 A353 1.0 (25) Bend -320 (-196) K, 114 (125) -280 (-175) K, 163 (179) -238 (-150) K, 179 (197)

1.2 (30) Bend -320 (-196) K, 162 (178) -260 (-162) K, 169 (186)

43 A553 1.0 (26) Bend -320 (-196) K, 169 (186) -280 (-175) K, 157 (173) -260 (-162) K, 154 (169)

1.0 (26) Bend -320 (-196) K, 169 (186) 162 (178) -280 (-175) K, 160 (176) 158 (174) -260 (-162) K, 160 (176) -238 (-150) K, 128 (141)

1.2 (30) Bend -320 (-196) K, 140 (154) -260 ( -162) K, 175 (193) -238 (-150) K, 170 (187)

27 A553l 1.0 (25) CT -320 (-196) K, 168 (185) -238(-150) K, 182 (200)

1.6 (40) CT -320 ( -196) K, 206 (227) -238 (-150) K, 216 (238)

3 .0 (75) Bend -320 (-196) K, 207 (228) 194 (213) 32 A553I 0 .63 (16) CN -320 ( -196) K, 279 (307) 276 (304)

-256 ( -160) K, 271 (298) LO (25) CN -320 (-196) K, 206 (227)

-256 ( -160) K, 230 (253) 226 (249) 0 .63 (16) CN -320 (-196) K, 237 (261) 229 (252)

-301(-185) K, 257 (283) 229 (253) -256 (-160) K, 268 (295) 265 (292)

1.0 (25) CN -320 (-196) K, 235 (258) 189 (208) -305 (-187) K, 255 (281) 249 (274) -292 ( -180) K, 244 (268) 223 (245) -280 (-175) K, 277 (305) 229 (252) -256 (-160) K, 264 (290) 244 (268)

1.4 (35) CN -320 ( -196) K, 227 (250) 191 (210) -292(-180) K, 220 (242) 205 (226) -256 ( -160) K, 273 (300) 245 (270)

2.8 (70) CN -320 (-196) K, 246 (271) 213 (234) -256(-160) K, 254 (279)

49 A553l 3.0 (76) CT -320 ( -196) K,• 107 (118) 101 (111) 46 A553l 1.0 (25) CT -320(-196) K, 166 (183) 136 (150)

-260 (-162) K, 190 (209) 185 (204) 48 A553l 0.25 (6) CLWL -270(-168) K, 490 (539) 35 A553l 2.0 (51) CTb -320 (-196) K, 150 (165) 142 (156)

3.0 (76) CTb -320 (-196) K, 145 (159) 127 (140) 2.0 (51) CT -320 ( -196) K, 176 (193) 168 (185)

-275 ( -170) K, 207 (228) 206 (227) 3.0 (76) Bend -320 (-196) K, 158(174) 153 (168)

48 A645 0.25 (6) CLWL -275 (-170) K, 385 (424) 355 (391) 0 .63 (16) CLWL -275 (-170) K, 304 (334) 300 (330) 1.25(32) CLWL -275 (-170) K, 206 (227) 206 (227) 1.5 (38) CLNL -275 ( -170) K, 197 (217) 171 (188)

46 A645 1.0 (25) CT -320 (-196) K, 78 (86) 78 (86) -260 (-162) K, 120 (132) 80 (88)

1.0 (25) Bend -260(-162) K, 73 (80) 65 (72) 35 A645 1.0 (25) CT - 320 ( - ,196) K, 105 (116) 95 (105)

Bend -275 (-170) K, 145 (160) 134 (147) 1.5 (38) CT -320 (-196) K, 96 (105) 86 (94)

Bend -275 ( -170) K, 122 (134) 121 (132)

• Ko used, not Kmax-

b Specimen thickness 1 in. (25 mm). • Not production material, pilot heats only.

28 WRC Bulletin 205

Table 17-COD Toughness Values for the Higher Nickel Steels

COD valu Refer- Gage, Test Test temp., Mean Min. ence Steel in. (mm) method o F (o C) Criterion Mils (mm) Mils (mm) 34 A353 1.4 (35) Bend -312 (-191) Max. load 7 .5 (0.19)

-283(-175) Max. load 9 .8 (0.25) -260 ( -162). Max. load 10 .2 (0 .26)

A353 2.6 (65) Bend -304 ( -187) Max. load 17.3(0.44) -260 (-162) Max. load 41.3 (1.05)

43 A353 0.8 (20) Bend -263 (-164) Max. load 12.2 (0.31) 12.0 (0.31) 39 A353 1.0 (26) Bend -320 ( -196) Max. load 3.9 (0 .10)

-292 ( -180) Max. load 3.9 (0.10) -275(-170) Max. load 6.7 (0.17)

A353 1.0 (25) Bend -320 (-196) Max. load 5.1 (0.13) -283 (-175) Max. load 9 .4 (0.24) -260 (-162) Max. load 15.3 (0.39) 14.9 (0.38)

A353 1.2 (30) Bend -320 ( -196) Max. load 9.0 (0.23) A353 1.2 (30) Bend -320 (-196) Max. load 8.6 (0.22)

-260 (-162) Max. load 13.0 (0.33)

43 A553l 0.7 (19) Bend -263 (-164) Max. load 11.8 (0 .30) 11.1 (0.28) 50 A553l 0.7 (18) Bend -320 (-196) Max. load 22 .0 (0 .56) 21.2 (0 .54) 27 A553l 1.0 (23) Tension -283(-175) Max. load 47 .2 (1.20)

(side -220 ( -140) Max. load 61.3 (1.56) 36.1 (0.92) notch)

A553l 1.0 (23) Tension -320 (-196) Max. load 44.4 (1.13) 42.1 (1.07) (center -283(-175) Max. load 59 .7 (1.52) 59. 7 (1.52) notch) -260 (-162) Max. load 63.7 (1.62) 61.3 (1.56)

-220 (-140) Max. load 74.7 (1.90) 70. 7 (1.80) A553l 3.0 (75) Bend -320 (-196) Max. load 24 .0 (0 .61) 20.4 (0.52)

-260 ( -162) Max. load 55 .4 (1 .41) 47 .2 (1.20) 39 A553I 1.0 (26) Bend -320 (-196) Max. load 11.0 (0 .28)

-275(-170) Max. load 14.5 (0.37) -260 (-162) Max. load 14.9 (0.38)

A553l 1.0 (26) Bend -320 (-196) Max. load 9 .0 (0 .23) 8.3 (0.21) -283 ( -175) Max. load 11.0 (0.28) 10.6 (0.27) -260 (-162) Max. load 11.0 (0.28) 10.6 (0.27)

A553l 1.2 (30) Bend -320 (-196) Max. load 5.5(0.14) -260 (-162) Max. load 11.0 (0.28)

A553I 1.2 (30) Bend -320 ( -196) Max. load 7 .1 (0 .18) -260 (-162) Max. load 12.2 (0.31)

35 A553l 1.0 (25) Bend -320 (-196) Max. load 7 .5 (0 .19) 7 .1 (0 .18) 1.0 (25) Bend -320 (-196) Max. load 8 .3 (0 .21) 5.5 (0.14) 2.0 (51) CT -320 (-196) Max. load 6.4 (0.16) 3 .7 (0.09)

Bend -275(-170) Max. load 18.1 (0.46) 15 .8 (0 .40) 3.0 (76) Bend -320 ( -196) Max. load 7 .8 (0.20) 6.9 (0.17)

28 A645 0.75 (19) Bend -270 (-168) Max. load 6.7 (0.17) A645 0 .63 (16) Bend -270 ( -168) Max. load 5.6 (0.14)

35 A645 1.0 (25) CT -320 (-196) Max. load 3.1 (0.08) 1.8 (0 .05) ·Bend -275 ( -170) Max. load 21.8 (0 .55)

A645 1.5 (38) CT -320 (-196) Max. load 2 .6 (0.07) 1.4 (0 .04) Bend -275 (-170) Max. load 13 .2 (0 .34) 12.5 (0.32)

• Not production materiai, pilot heats only.

test results are found in Tables 16 and 17 and are summarized in Figs. 26-28.

It may be seen that data which have been ob­tained, include both Kc and COD values for A353, A553 Type I, and A645 and that they cover a wide range of product thicknesses; from thin section, 0.25 in. (6 mm), up to as thick as 2.6 in. (65 mm) for A353, 3 in. (76 mm) for A553 Type I, and 1.5 in. (38 mm) for A645. Some of the heavier section data, namely the 2.6 in. (65 mm) for A353 are for forging material, as is some of the KMN Commission data 1 but the rest of the data are· from plates. The toughness prop­erties of the steels given in Table 16 are in terms of the fracture toughness based on maximum load, and thus could be classified as Kc data. Because of the

wide variety of data sources, it is not possible to as­sess in every case which data might be actual Kie

values, i.e., fully plane strain toughness. Although some of the data may fall in that category, the steels generally do not display the classical linear elastic load-deflection trace in a fracture toughness test even when specimen thicknesses are great enough to meet ASTM E399-72 specifications for plane strain behav­ior. Thus the data are not valid plane strain values in most cases. On the other hand, the range of thick­nesses shown on Table 16 do span those used in most applications, and are thus useful in assessing the available fracture toughness.

One of the most difficult factors to assess is the in­fluence of the loading system applied in service on

Cryogenic Nickel Steels 29

80 60

t /

70 Charpy Impact Energy 06

..., ,c A353-• 04 50 '..., A553I-o I

~(.) 60 Drop Weight Tear Energy

"' ~o A353- c. ' -~ A553I- 6 •s 40 Q ', 50 l.~4.,

JC

co C,~($ •4 .fa >, >, •6 ~ e'e- 40 ., .,

.,,P5 30 a C: C:

IJJIJJ uo 66 ~ &i!! 30 '

c.4 .:: E- 20 - .c "'"c§ >,..Q'

~~ 20 ~ .c a.

~e,,c;, •5

(.) ~ (j~ ·~4

10 10 l Numbers Correspond to

Heats on Table 13

0 0 0 2 4 6 8 10

Retained Austenite - %

Fig. 25-Relation of retained austenite in 9 % Ni steels to their notch toughness at -320° F (-196° C)

OF

0.8 -300 -250 -300 -250

30 0.7 A553TypeI A553Typel

HAZ 0.6 o Average

i • Minimn

0.5 20 E / E 0.4 ~· . ..

·e 0.3 V ~/

0 Q 10 (.) 0.2

.

0.1 • 0

1 ~ 0

i__---r- • 300 300 C:'. 0

~ ~

i •- • 200 200 :E

·---0 • ~ I §

u • ·--------i i.: i 100 100

0 ,__ __ ..__ __ _,__ __ __._ __ _.__ __ _.__ __ -J 0

-200 -180 -160 -200 -180 -160 -140 Testing Tempera lure - "C

Fig. 27-Minimum and average values of fracture toughness mea­sured by Kc and COD for A553 Type I steel plates and weld heat-af­fected zones

-300 -250 0.8 I

• ~353 0.7 - OAverooe • Minimum

0.6 -

0.5-. E •

7 0.4 - ' ~0.3-__/.-

0 o.2..::1 • I./ ..!---------0. f I -

OF -300 -250

I

0

30

25

20

-15!!!

E 10

5

0 r------------t-------------1,0

0_200 I I

-180 -160 -200 -180 Testing Temperature-'\'.:

•

I

-160

300

200

~ ~

100

Fig. 26-Minimum and average values of fracture toughness mea­sured by Kc and COD for A353 steel plates and weld heat-affected zones

OF 0.8

-300 -250 -300 -250 30

0.7 A645 A645 0

HAZ 0.6 OAverooe

•Minimum E • E 0.5 20 I !!! c:i 0.4

/ ·e

0 0 0.3

, 10 0.2 /

/

0.1 0 / ,,. 0 0

ij IC

D) 3(X)

~ ~ 200 0 20'.) •/ a.

__>~ ~ :E /

/ ~ u i.: ICO

/ 100 a----

o~--_._ __ _.__ __ ___. __ _,'- __ ..,_ __ ~o -200 -180 -160 -200 -180 -160 -140

Testing Temperature - "C

Fig. 28-Minimum and average values of fracture toughness mea­sured by Kc and COD for A645 steel plates and weld heat-affected zones

30 WRC Bulletin 205

the apparent Kc of the material. That is, will a speci­men that displays pop-in (small sudden crack ad­vance followed by arrest) behavior in a small speci­men test, with a subsequent load increase to a maxi­mum load, actually fully fracture at the pop-in load in service. At the present time the only way in which such a question can be approached is through wide plate tests, few of which have been run. In those cases where the tests have been run, for· A353 and A553 Type I for example, the Kc values produced are not lower than those produced in other tests. Another form of data that can be obtained from these tests but are not listed in the tables (except in a few cases) are Kq or conditional Krc values based on the inter­section of the 5% secant modulus line on the experi­mental load-deflection trace. In less ductile materi­als, this represents the initiation of slow crack growth prior to fracture, and thus is a significant point in the test. In these materials, it does not represent crack initiation and therefore does not have the same frac­ture significance. For this reason, a Kc based on max­imum load is favored by most investigators rather than Kq. Again, the Kc calculated from the tests could be modified to include the effect of the plastic zone at the crack tip as well as the actual physical crack. This is theoretically more accurate, perhaps, but from the practical standpoint is less helpful be­cause it would give a Kc that ovel'.estimates the allow­able physical (measurable) crack size in the structure unless it can be calculated and added to the physical crack. This is often hard to do, and therefore Kc based on the physical crack size in the specimen should be a suitable parameter for comparison with crack sizes found in structures by nondestructive ex­amination techniques. The data in Table 16 are ap­parently derived without plastic zone size correc­tions.

An examination of Figs. 26-28 establishes the spread of the data for the three steels in the cryogen­ic temperature range. At -320° F (-196° C) the frac­ture toughness at A353 varies from a minimum of about 115 ksi vin. (127 MPa vm) for Kc to an upper level of about 160 ksi vin. (176 MPa vm). The cor­responding COD range is about 4 mils (0.10 mm) to nearly 10 mils (0.25 mm). It should be noted that the minimum toughness is not necessarily related to sec­tion size, in that the thickest material, a 2.6 in. (65 mm) forging had a higher toughness than some of the thinner plates.

It would normally be expected that the heavier plates would have lower toughness for several rea­sons. First because of hardenability considerations, the heavier plate should have less tough microstruc­ture, and secondly because larger scale specimens could be tested and thus lower Kc values measured because of specimen thickness effects. For the A353 and A553 Type I materials, however, their hardena­bility is quite adequat~ for the sections involved and, as has been demonstrated, factors such as retained austenite content may be more important than sim-

ple hardenability considerations. Again, work32 on the influence of section size on measured Kc, illus­trated in Fig. 29, shows that Kc is not very sensitive to specimen thickness either. Thus Kc toughness varies from heat-to-heat and heat treatment to heat treatment more than it does because of section size or even specimen size.

The limited effect of heat treatment on the 9% nickel composition is illustrated by the fact that the Kc data scatter band from Fig. 26 (A353) can be su­perimposed on that on Fig. 27 (A553 Type I) with lit­tle adjustment of the bounding lines for either heat treatment or specimen size.

While the fracture toughness data for A645 is more limited in scope than for the other two steels, it ap­pears to have about the same toughness at -275° F (-170° C) as A553 has at 320° F (-196° C), having a Kc range from about 120 ksi vm. (133 MPa viii) to about 350 ksi vm. (385 MPa vm). The COD values range from about 12 mils (0.30 mm) to about 25 mils (0.63 mm) at -275° F (-170° C), higher than A553. At -320° F, A645 toughness is lower than A553, hav­ing a K range of 85 ksi vin. to 110 ksi vm.

Dynamic Fracture Toughness. The higher nickel steels differ from most other structural steels in that dynamic fracture toughness values equal or exceed the static values. This is true partially because almost all of the toughness tests reported here are on or near the upper shelf in toughness. One evidence of this is the fact that in the Kc, COD and dynamic tear tests little toughness change is seen for most heats down to the testing temperature limit, -320° F (-196° C). As was demonstrated for a number of steels 33 when test­ed on their upper shelf (i.e., at elevated temperatures for normal structural steels) dynamic toughness is

in 0 1.0 2.0 3.0

A553TypeI 340 -196°C

• • 300 • •• • • • •

~ • • 250 • 28') ~

::::e ~ u ~ 220 200

Plate Thickne■s•70mm

180 150

140 0 10 20 30 40 50 60 70 80 90

Specimen Thickness - mm

Fig. 29-Effect of specimen thickness on the observed Kc tough-ness values of A553 Type I steel at -320° F (-196° C)

Cryogenic Nickel Steels 31

t e. :i:

u ll::

450

350

300

250

200

150

in 0 0.1 0.2 0.3

A553Typel

\c9\· 35mm, -162°C 14KJ cm

\ •­v--·/ . G)

25mm -196°C • ISKJ cm ~.--·

100 -----~-~-__. __ _.___.......___, Weld Metal

Average

0 2 4 6 Bose Plate

Distance From Fusion Line Averoqe mm

400

200

100

Fig. 30-Fracture toughness Kc valoes in A553 Type I steel as a function of location at a welded joint and the welding heat input used

frequently better than the static, and that is the case for these steels. Direct confirmation of this behavior was obtained in tests A353,34 A553,35 and A645.35

Thus the static fracture toughness tests are adequate for design purposes.

Effect of Strain Aging. Both A553 Type I and A645 show moderate sensitivity to mechanical strain­ing in terms of impact toughness. Specimens of A553 Type I that were strained in tension at room temper­ature 3% or 5% decreased in toughness at -320° F (-196° C) from 144 ft-lb (196 J) to 119 and 50 ft-lb (162 and 68 J), respectively, as a result of the strain. For A645 the same strain levels caused a reduction in toughness at -275° F (-170° C) from 76 ft-lb to 61 and 50 ft-lb (83 and 68 J), respectively. Stress reliev­ing of the A645 restored essentially the original toughness properties. The as-strained properties are still quite good, well above -the specification mini­mum for the steel. Moreover, cold forming strains may not exceed 3% without subsequent stress reliev­ing operations if practice is based on Section VIII; Division 1 of the ASME Boiler and Pressure Vessel Code. Tests on A353 and A553 Type 1 have shown 29,10 that they can be somewhat sensitive to holding in the 600-1000° F (315-538° C) tempera­ture range. Such heat treatments should be avoided as they can result in a substantial toughness loss, par­ticularly for aging times beyond 1 hr. Reheating to

400

ll::u

u

,§200 "2 ~ <[

olOO u :t:

-1-\ -'-.-'---'-t-"'-------t-::---SA Heat Input

IP, tp '3P ~O KJ/qn SMA J +--+--'-~I ->--=➔i--GMA 25nmPlate

A553I o 23-35mm • 12-17mm • 6mm

I • • •

•

400

300

0 0L--10.____2Lo--3~0--~L--50L--roL---'1~0-o

Cooling lime from 8J0-500"C,sec

Fig. 31-Effect of cooling rate in the HAZ on fracture toughness Kc values measured at -260° F (-162° C) in the HAZ of 9% Ni steel

above 1050° F (566° C) for 1 hr restores the initial toughness of the steel.

Effeot of Welding. The notch toughness of weld­ed joints of the higher nickel steels in terms of Char­PY impact energy and fracture toughness parameters are found in Tables 18-20 and on Figs. 26-28. In gen­eral, it may be stated that these steels have a tenden­cy for reduced toughness in the weld heat-affected zone, especially at high heat inputs. In some cases this appears to occur close to or at the fusion line and sometimes several millimeters from it. This sensitivi­ty can best be seen in terms of Charpy impact tough­ness in Table 18 for A645, for which extensive data have been developed. In terms of Kc values, this point is illustrated for A553 Type I in Fig. 30 where two investigations 32,35 of HAZ toughness in this steel are summarized. In spite of this tendency for reduced toughness, however, minimum Kc values listed for welded joints in Tables 19 and 20 and on Figs. 26-28 are not significantly lower than minimum Kc values for the plates themselves. Moreover, this toughness can be controlled by careful selection of welding pa­rameters as Fig. 31 shows. These data 32 permit the selection of appropriate welding combinations to control the toughness of the heat-affected zone in these welds. Weld metal properties, listed on Tables 1.9 and 20, are generally good when austenitic weld metals are employed. Minimum Kc values for these materials, as seen on Table 19, are often misleading, however, because the maximum loads recorded in the test are low due to the lower yield strength of the weld metal. In order to get a clearer picture of their

32 WRC Bulletin 205

Table 18-Charpy V-Notch Impact Test Results on Welded Higher Nickel Steels at -196° C

-Impact energy at position indicated ft-lb (J) Refer- Gage, Process and Heat input, Fusion ASME ence Steel in. (mm) position kJ/cm Electrode line 1 mm 2mm 3mm 5mm test 43 A353 ¼ (20) SMA (V) NiCrFe 65 (88)

27 A553I 1 (25) SMA (V) 17-36 Y Weld B 62 (84) SMA (V) 17-36 Y Weld B (M) 49 (66) SMA (V) 17-36 Nic-70 85 (115) SMA (V) 17-36 Nic-50 52 (70) SMA (V) 30-39 NiA-37 74 (100)

¼ (20) GMA (F) 11-16 Autrod 37 34 (46) ¼ (20) GMA (V) 59-63 Autrod 37 30 (41) ¼ (19) SA (F) 40 Nittetsu Filter 81 (109) 57 (77)

196, Flux 10 ¼ (19) SA (H) 11-13 Nittetsu Filter 61 (83) 75 (101)

196, Flux 10 l3/u (30) SA (H) 13 Nittetsu Filter 74 (100) 94 (127)

196, Flux 10 2½ (65) SA (F) 13 Y Weld B 48 (65) 68 (92) (transverse) 2½ (65) SA (F) 13 Y Weld B 56 (76) 100 (135) (longit.)

43 A553I SMA (V) NiCrFe 59 (82)

("':) 35 A553I 2 (5) SMA (F) 30 lnco-Weld B 42 (57)

<.';! GMA (F) 51 Inco 82 72 (97)

~ 28 A645 5/. (16) GMA (V) 15.7 Inconel 92 89 (120) 78 (105) 122 (165) 114 (155) 95 (128)

~ (V) 51 lnconel 92 13 (18) ;:s (H) 15.4 lnconel 92 35 (48) .... '"' ¼ (19) (V) Inconel 92 61 (82)

-~ (H) Inconel 92 51 (69)

'"' (V) 68 Inconel 92 39 (53) ~

~ (V) 31 lnconel 92 57 (77) CJ., (V) 19.7 Inconel 92 50 (68) ..... (F) 18.4 Inconel 92 43 (58) ~ ~ 1 (25) (V) 31 lnconel 92 57 (77) 1i;"'

(V) 23 lnconel 92 52 (70) 46 (62) 46 (02) 51 (69) 36 (49) (V) 28 Inconel 92 42 (57) (H) 11 Inconel 92 47 (64) (V) 31 Inconel 92 46 (62) (V) 35 lnconel 625 22 (30) (H) 12.5 Inconel 625 88 (119) 64 (87) 81 (110) 77 (104) 39 (53)

5/s (16) SMA (V) Inco-Weld A 53 (72) ¼ (19) (V) 26 Inco-Weld A 37 (50)

(V) 35 Inconel 182 49 (66) 5/s (16) (V) 28 McKay 9 Ni 9 (12) ¼ (16) (V) 24 McKay 9 Ni 28 (38) 5 ;. (16) (V) 59 Cryo-Therm 60 29 (39) 16 (22) 19 (26) 40 (54) 41 (56)

(H) Cryo-Therm 60 49 (66) 1 (25) (V) 51 Cryo-Therm 60 36 (49) 20 (27) 33 (45) 45 (61) 33 (45) 5/s (16) (H) Yawata B 57 (77) 5/s (16) SA (F) 11 Lincoln 880 54 (73) 63 (86) 98 (133) 90 (121) 100 (136)

Inconel 82 1 (25) SA (F) 19 lncoflux 4 41 (56) 63 (85) 55 (75) 29 (39) 56 (76)

lnconel 82 48 1½ (38)

~ GMA (H) 18.6 lnconel 92 103 (140) 89 (120) 70 (95) 59 (80)

~

Table 19-Fracture Toughness Properties of Higher Nickel Steel Weldments

K value Mean Min.

Refer- Gage, Test Test temp., ksivin. ksivin. ence Steel in. (mm) method o F (o C) Criterion (MPavm) (MPavm)

HAZ properties 34 A353I 1.3 (33) Bend -301 (-185) Kc 96 (106)

-280 (-175) Kc 122 (134) -260 (-162) Kc 133 (146) 114 (125)

A353l 2.5 (65) Bend -308 (-189) Kc 104 (114) -260 (-162) Kc 190 (209) 185 (204)

A353I 1.6 (41) Wide plate -260 (-162) Kc 144 (158) 143 (157) 1.0 (25) Wide plate -260 ( -162) Kc 144 (158)

27 A553I 1.0 (25) CT -320 (-196) Kc 188 (207) -220 ( -140) Kc 226 (249)

2.0 (51) CT -320 ( -196) Kc 153 (168) 131 (144) -238 ( -150) Kc 172 (190)

32 A553l 0 .67 (17) CT -260 (-162) Kc 172 (190) 125 (138) 1.0 (25) CT -260 (-162) Kc 255 (280) 125 (138)

45 A553l 0.25 (6) CLWL -270 (-168) Kc 309 (340) 0 .25 (16) CLWL -270 (-168) Kc 402 (442)

35 A553l 2 .0 (51) CT -320 ( -196) Kc 159 (175) 153 (168) A553l 2 .0 (51) CT -320 ( -196) Kc 109 (150) 106 (143)

48 A645 0.25 (6) CLWL -275 (-170) Kc 463 (510) 465 (512) 0 .63 (16) CLWL -275 (-170) Kc 410 (451) 1.5 (38) CLWL -275 (-170) Kc 196 (216)

A645 0.25 (6) CLWL -275 (-170) Kc 325 (358) 325 (358) 35 A645 1 (25) CT -320 (-196) Kc 87 (96) 82 (90)

Weld metal properties 34 Inconel 82 1.3 (33) Bend

Inconel 112 1.3 (33) Bend

Inconel 625 1.6 (41) Wide plate 27 Yawata B 2.0 (51) CT

Yawata B 1.0 (25) CT

45 Inconel 92 0.25 (6) CLWL Inco-weld B 0.25 (6) CLWL

35 Inco-weld B 2.0 (51) CT Inconel 82 2.0 (51) CT Inco-weld B 1.0 (25) CT

45 Inconel 92 0.25 (6) CLWL Inco-weld B ' 0.25 (6) CLWL

generally ductile behavior, the COD toughness data of Table 20 need to be examined. Toughnesses of weld metal as measured in this test are well above the minima for the base plates or heat-affected zones.

Fatigue Strength The available fatigue data on the higher nickel

steels, both in terms of full life tests and crack growth rate tests are listed in Table 21. This table covers a wide variety of tests, both notched and unnotched, welded and unwelded, ambient and cryogenic. In summary, it must be said that the higher nickel steels do not show any particularly unique aspects in their behavior. The fatigue lives for the plain plate, notched plate, and welded plate specimens appear to be about normal for a structural steel. Typical stress levels for 107 cycle life are about one-half of the ten­sile strength or a little above, and welding reduces this to about one-quarter of the tensile strength due to its geometry. Grinding of the weld toe in such a

-305 (-187) Kc 139 (153) 131 (144) -260 ( -162) Kc 136 (150) 129 (142) -306 ( -188) Kc 158 (174) -260 (-162) Kc 172 (189) 164 (180) -260 (-162) Kc 705 (776) -320 (-196) Kc 230 (253) -220 (-140) Kc 210 (231) -320 ( -196) Kc 158 (174) -238 (-150) Kc 150 (165) -270 (-168) Kc 375 (413) -270 (-168) Kc 414 (455) -320 (-196) Kc 137 (151) 136 (150) -320 (-196) Kc 120 (132) 117 (129) -320 ( -196) Kc 142 (156) 130 (143) -275 (-170) Kc 375 (412) 375 (412) -275 ( -170) Kc 414 (455) 414 (455)

specimen restores much of its fatigue resistance. Testing at cryogenic temperatures serves to raise the fatigue level. The da/dN vs. M curves also appear to fit the typical scatter band for structural steels, and cryogenic crack growth rates are not significantly dif­ferent from ambient ones.

Summary The higher nickel steels meeting ASTM specifica­

tions A353, A553 Types I and II, and A645 readily meet and exceed the Charpy toughness levels set in ASTM specification A593 and exhibit good Kc and COD toughness in the cryogenic range. Welding does not significantly limit their usefulness, nor does any other potential cause for concern, such as cryogenic fatigue resistance, or dynamic fracture toughness be­havior. Their application in the cryogenic range will depend primarily on their fracture toughness and tensile properties at service temperatures.

34 WRC Bulletin 205

Table 20-COD Toughness Values for Higher Nickel Steel Weldments

OD values Refer- Gage, Test Test temp., Mean Min. ence Steel in. (mm) method o F (o C) Criterion Mils (mm) Mils (mm)

Heat-affected zone properties 34 A3531 1.4 (35) Bend -301 ( -185) Max. load >8.3 (>0.21)

-280 (-175) Max. load 14.1 (0 .36) -260 (-162) Max. load 25.2 (0.64)

A3531 2.6 (65) Bend -308 (-189) Max. load 5.9 (0 .15) -260 (-162) Max. load >33.8 (>0.86)

43 A3531 (20) Bend -264(-164) Max. load 17.9 (0 .43) 11.8(0.30) 43 A5531 (19) Bend -264(-164) Max. load 11.8 (0 .30) 11.0 (0.28) 50 A5531 0.7 (18) Bend -320 ( -196) Max. load 11.8 (0.30) 4:7 (0.12) 35 A5531 2.0 (51) CT -320 (-196) Max. load 5.2 (0 .13) 3.3 (0.08)

A5531 2.0 (51) CT -320 (-196) Max. load 4.2 (0 .10) 3 .6 (0 .09) 35 A645 1.0 (25) CT -320 ( -196) Max. load 2.0 (0 .05) 1. 7 (0 .04)

Weld metal properties 34 Inconel 82 1.6 (35) Bend -304 (-187) Max. load >33 .0 (>0 .84)

-260 ( -162) Max. load >34.2 (>0.87) Inconel 112 2.6 (65) Bend -306 (-188) Max. load 12.6 (0 .32)

-260 (-162) Max. load 18.5 (0 .47) 43 Electrode A 0 .63 (20) Bend -264 (-164) Max. load 9.1 (0 .23) 6. 7 (0 .17)

Electrode B 0 .63 (19) Bend -264 ( -164) Max. load 10.6 (0 .27} 9.9 (0.25) Electrode A 0 .63 (20) Wide plate -264 (-164) Max. load 46.5 (1.18) 13.3 (0.34) Electrode B (19) Wide plate -"264 ( -164) Max. load 86 .6 (2 .2)

35 Inconel 82 2.0 (51) CT -320 (-196) Max. load 7.6 (0 .19) 7.5 (0.19) Inco-weld B 2.0 (51) CT -320 (-196) Max. load 14.8 (0.38) 11.4 (0 .29) Inco-weld B 1.0 (25) CT -320 ( -196) Max. load 16.5 (0 .42) 9.8 (0.25)

Assessment of the Cryogenic Nickel Steels

Rationale of the Assessment

Tensile Properties. The extensive data accumu­lated for the nickel steels (Tables 4-6, 12, and 13 and Figs. 11..:..13, 20-22) show that each of the steels readi­ly meets the tensile property requirements of the ASTM specification. Also it appears that with appro­priate welding procedures, welded joints of these steels exhibit transverse tensile strengths that exceed the minima specified for the base metal. Thus the tensile properties of the steels are suitable for the in­tended purposes.

Fatigue Properties. Examination of the fatigue data reveals that (1) smooth specimen tests produce fatigue limits roughly 50% of the tensile strengths, (2) the reductions in fatigue strength induced by notch­es, weld reinforcements, or structural details are di­rectly comparable to those observed in other struc­tural steels, and (3) the crack-growth rates vs. !:iK relations reported for these steels fall squarely in the scatter band that has been found to be characteristic of carbon and low alloy steels as a group. 36 Conse­quently, no anomalies have been observed in the fa­tigue performance of the nickel steels to prevent rea­sonable prediction of service behavior by the accept­ed methods of analysis.

Notch Toughness. While the V-notch Charpy test is a useful indicator of material uniformity for quality control purposes, Charpy test results cannot serve as a basis for estimating the suitability of the steels for particular applications with defined parameters of stress level, flaw sizes, structural constraints, and op-

erating temperature. This is not to say that specifica­tion such as ASTM A593 have no value, it means rather· that more elaborate mechanical testing meth­ods are required to evaluate such suitability, and even these methods have recognized limitations that should not be minimized. The drop-weight test is in much the same category as the Charpy test, in that it measures a transition temperature under prescribed conditions that is not easily translatable to the ser­vice performance of specific structures. One approach is to add a chosen temperature differential to the NDT or Charpy transition temperature to arrive at a lower limit of safe operating temperature, but this procedure may be over conservative or risky depend-ing on the differential selected. ··

Fracture Toughness. The upshot of this discus­sion is that the range of usefulness of the nickel steels for cryogenic applications must be gaged by fracture toughness analyses. An attempt will therefore be made to set the combinations of stress level, flaw size, and operating temperature that are permissible in the design of a safe cryogenic structure. For the high­er nickel steels, the static and dynamic fracture toughness values are essentially the same, and there­fore no adjustment in calculation is necessary for strain rate effects. The low Ni steels are strain-rate sensitive and must be treated accordingly.

Survey of the Fracture Toughness Data

The accumulated data on fracture toughness of the nickel steels were presented in Tables 16-20 and Figs. 26-28. For the purpose of deriving allowable stress-flaw size combinations, the lower-bound values (95% confidence limit) of Kc and COD were extracted

Cryogenic Nickel Steels 35

Table 21-Summary of Fatigue Measurements on the Higher Nickel Steels

Lower bound t,.K for da/dN

c,.; Refer- Gage, Temperature, -Stress level, ksi (MPa)-~ in in./cycl ~

ence Steel in. (mm) Test method o F (o C) N = J05 N = 101 10-• 10-• Notes

34 A353 1.2 (35) Tension R.T. 10. 7 (11.8)

R = 0. ---

A353 Tension R.T. 58 (64)

Tension-notched, R.T. 24 (26) K, = 3

Tension notched, -260 (-162) 25 (28)

K, = 3 Tension weld R.T. 26 (29)

-260 (-162) 33 (36)

47 A553I 1.3 (33) Center slot plate R.T. 87 (96) 11.7 (13)

(R = 0)

45 A553I (6) Moore R.T. 100 (690) 72 (500)

Moore, K, = 2.5 R.T. 52 (360) 27 (185)

Moore -270 (-170) 125 (860) 98 (675)

Moore, K, = 2.5 -270 (-170) 62 (430) 39 (270)

0.25 (6) Surface-notch -270 (-170) 90 (100) 19 (21)

tension test Surface-notch -270 (-170) 95 (105) 38 (42) HAZ

~ tension test 100 (111) 32 (35 .4) HAZ

46 A553I 1.0 (25) Compact tension -260(-160) 80 (89) 13 (14 .3)

("°'.) Compact tension -320 (-196) 61 (67 .5) 16 (17. 7)

tc:, R = 0

£. R = 0 N = 106

~ 42 A553I 0.5 (13) Strip tension R.T. 77 (533) 44 (304) ..... s· 0.5-1.5 (13-35) Strip tension R.T. 175 (255) 17 (117) Transverse butt weld

l:\J with reinforcement

~ 0 .5-1.5 (25-35) Strip tension R.T. 51 (353) 29 (201) Same, ground at toe

R = 0 R = 0 N = 106

42 A553I 1 (25) Strip tension R.T. 71 (490) 18 (264) Same, ground flush

0 .87 (23) Strip tension R.T. 60 (416) 16 .5 (238) Longit. butt weld with reinforcement

0.5 (13) Center-notch R.T. (57) 17 (19)

tension test 43 0. 75 (19) Center-notch R.T. 57 (63) 13 .6 (15)

tension plate N = 107

R = -1 R = -1

51 0 .03 (0 .7) Flexure, K, = R.T. 60 (415) 28 (195)

3.1 -320 (-196) 65 (450) 25 (175)

0.04 (1) K, = 1 R.T. 53 (365) 37 (255) -320 (-196) 66 (455) 52 (360)

R = 0 N = 107

45 A645 0. 75 (19) Moore R.T. 58.5 (403)

Moore, K, = 2 .5 R.T. 27 (186) Through thickness crack.

0 .65 (16) Moore -275 (-170) 88 (607) 14 (15 .5) Thickness range 0 . 25-

Moore, K, = 2 .5 -275 (-170) 35 (241) 1.5 in for t,.K data

0.25 (6) Moore,K, = 2.7 -320 (-320) 33 (228)

45 0 .63 (16) Center-notch R.T. R = 0.7 11 (12)

tension R.T. R = 0.4 13.5 (15) Part through crack

R.T. R = ~0 20 (22)

-270 (-168) R = 0.4 16(17.6)

Table 22-Lower-Bound Fracture Toughness Values 95% Confidence Level, Obtained from Reported Data

Steel Location Temp. A353 Base metal -196° C

-170° C -196° C -170° C

HAZ -190° C -170° C -190° C -170° C

A553 Base metal. -196° C -170° C -196° C -'170° C

HAZ -196° C -170° C -196° C

A645 Base metal -170° C and HAZ

A203 Normalized -75 ( -60) ·base metal -75 ( -60)

Q&Tbase -110 (-80) metal -110(-80)

A203A Norm. base -90 (-70) metal

Q&Tbase -90 (-70) metal

A203D N & SR base -110(-80) metal -150 (-100)

-100(-75) Q&Tbase -130 ( -90)

metal -150 (-100) -100(-75)

a K. in ksivin. (MPavm 1' 2), COD in inches (mm). b Km calculated from drop-weight NDT, where (K,d/ <Ty)2 is estimated as 0.5. • Km calculated from Charpy V-notch value by relation, K,d = 13(C,) 112•

Criterion Valuea K. 112 (125)

150 (165) COD 0.004 (0.1)

0.007 (0.17) K. 95 (105)

104 (115) COD 0 .005 (0 .13)

0.010 (0.25) K, 126 (140)

146 (160) COD 0.004 + (0.11)

0 .010 (0 .25) K, 117 (130)

121 (135) COD 0.004 (0.10) K. 120 (132) COD 0.010 (0.25) NDT Km (calc.)b 60 (66) NDT Km (calc.)b 71 (78) Km (calc.)• 60 (66)

Km (calc.)• 72 (79)

NDT Km 45 (50) Km 65 (72) NDT Km 60 (66) Km 100 (110)

from the scattergrams and are listed in Table 22. For the low Ni steels, NDT and Km values (the latter calculated for A203A from Charpy or drop-weight tests) are listed.

perature of interest. The tmax values obtained corre­spond closely to the critical flaw depths obtained for the K = 3 condition.

Flaw Size-Allowable Stress Relations The 9% Nickel Steels. For these steels the pa­

rameters of interest are: temperatures of -196 and -170° C, nominal stress level of 25 ksi (173 MPa) [¼ T.S.], thicknesses of 112, 1, and 1 ½ in. (13, 25, and 51 mm), and stress concentration factors of K = 1, K = 2, and K = 3. The nominal stress with K = 3 also ap­proaches the yield point stresses that are produced in welded joints.

Calculations by means of the simple relation Kc = u-v'ia were made to evaluate surface flaw sizes and the allowable membrane stresses for through-thick­ness flaw size equal to 2T and K = 2 in each of the thickn~sses. The results listed in Table 23 may be re­garded as conservative, since they encompass the most unfavorable set of conditions to be anticipated. It is important to note that these steels are insensi­tive to strain rates and thus will resist propagating cracks as effectively as they will initiating cracks. The maximum thicknesses capable of through-thick­ness plastic strain were also evaluated from the rela­tion suggested by Hahn and Rosenfield, 37 tmax = (Kc/uy) 2, where Kc and try are measured at the tem-

The calculated values may be interpreted in vari­ous ways. If the critical flaw sizes at design stress lev­els are regarded as significant, they are encouragingly large. Defects occur in welded joints, openings, and attachments, however, where stress concentrations are present. In these locations the critical flaw size is considerably smaller and the leak-before-break re­quirement may not be possible. The heat-affected zone properties are somewhat lower than those of the base metal, but their importance may be limited by the irregular shape, small volume, and non-uniformi­ty of microstructure of HAZ's produced by multipass welding. The base metals of½ and 1-in. thicknesses exhibit leak-before-break capabilities even at K = 2 stress concentrations. As thickness increases above 1 in. (25 mm), attention to flaw size control becomes correspondingly more demanding.

A645 Steel. The fracture toughness of this steel nearly matches that of the 9% nickel steels at -275° F (-170° C) although it is lower at -320° F (-196° C). Because of the sloping characteristics of Charpy and dynamic tear test curves in this temperature range, it is probable that the steel will exhibit high fracture toughness above -275° F (-170° C).

· A203 Steels. From the Charpy and drop-weight

Cryogenic Nickel Steels 37

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= N in I ii: CD :a j 1 N CD :a ~

38

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0000 LOO LOO ................ I I I I

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test results on A203 Grade A steel, the steel is shown to meet A593 requirements at -90° F (-70° C) but its usefulness may be limited to somewhat higher temperatures, certainly above the NDT, -75° F (-60° C). Similarly, the A203 Grade D may be limit­ed to -100° F (-75° C). These conservative esti­mates are based on the demonstrated strong effect of strain rate on notch toughness of the A203 grades (e.g., Fig. 17). A gain of some 25° F (15° C) seems available by quenching and tempering instead of nor­malizing these compositions.

Summary Sufficient data are at hand to characterize the ten­

sile strength, fatigue resistance, and fracture tough­ness of the cryogenic nickel steels. The critical prob­lem is to arrive at an engineering decision about the conditions that must be specified and attained in practice to assure satisfactory service in particular applications. Since the nickel steels exhibit no pecu­liarities or anomalies unfavorable to their reliability in service, the techniques developed to use other alloy structural steels satisfactorily in engineering structures are equally applicable to the nickel steels.

Suggested Research

There are a number of research peeds that have become evident as the data presented in this report were summarized. Some of these needs are included in the numerous current research programs in this area which are listed in Table 24.55 In general, how­ever, there is still a great deal of pertinent research to be undertaken. This research may be catagorized into three areas.

First, there is a need to develop more data of the type summarized here, and especially fracture tough­ness data on the higher nickel steels. For the lower nickel steels, transition temperature concepts may be effectively employed to define service. For the higher nickel steels, however, fracture mechanics design seems to be appropriate for service and little data are now available. There is a need to develop a substan­tial body of data on both the A553 Type I and A645 steels, particularly for the A645, so that normal trend lines and reasonable confidence limit values can be obtained and utilized.

Secondly, there is a need for more wide plate and large specimen data. Although some programs involv­ing these tests are currently active, the question of the significance of crack arrest on pop-in can only be determined in well planned large scale tests. More work on specimen thickness effects, both from the metallurgical and mechanics viewpoint, is necessary. The effect of thickness on COD is but one facet of this complex problem deserving attention.

Finally, the question of the effects of welding, par­ticularly on the properties of thin section higher nickel steels should be studied. Current data suggests that there is a moderate loss of toughness in weld

WRC Bulletin 205

· heat-affected zones when low and medium weld heat inputs are used. A thorough investigation of the ef­fect of both welding process and process parameters (particularly high heat inputs) is in order. Explora­tion of this fabrication variable would be most help­ful to designers and engineers who need to assess the effective toughness of a weldment in cryogenic ser­vice.

Acknowledgments

The authors acknowledge the assistance of many members of the Pressure Vessel Research Committee in the Materials and Fabrication Divisions who con:~.,, tributed data for their use. The International Nickel Company provided extensive and invaluable aid in obtaining pertinent information from their own sources and from the open literature. The encourage­ment and support of both PVRC and The Interna­tional Nickel Company is greatly appreciated.

References 1. Yeo, R. B. G. and Miller, 0. 0., "A History of Nickel Steels from

Meteorites to Maraging," Sorby Centennial Symposium on History of Me­tallurgy, ASM, Cleveland, Ohio, Oct. 21-23, 1963.

2. Bergeson, R., "Behavior of Some Irons and Steels Under Impact and Low Temperature," Trans. Amer. Soc. Steel Treating, pp. 19, 368, 1932:

3. Brophy, G. R. and Miller, A. J., "The Metallography and Heat Treat­ment of 8 to 10 Percent Nickel Steel," Trans. ASM, 41, 1185 (1949).

4. "Operations Cryogenics," The International Nickel Co., Chicago Bridge and Iron Co., and United States Steel Corp., 1961.

5. Kottcamp, E. H., Jr. and Stout, R. D., "Effect of Microstructure on Notch Toughness--Part IV,'' Weld Jnl., 38 (11), 435s-440s (1959).

6. Ronald, T. M. F., "The Influence of Nickel on the Strength, Tough­ness and Structure of Low Carbon Steels," Technical Report, AFML-TR-67-434, May 1968.

7. "Metallography, Structures, and Phase Diagrams,'' Metals Hand­book, Vol. 8, American Society for Metals, Metals Park, Ohio, 1973.

8. Stout, R. D., "Higher Strength Steels for Welded Structures," Weld. Jnl., 39 (7), 273s-283s (1960).

9. Sarno, D. A., Havens, F. E., and Bowley, D. L., "Transformations In­volved in Developing Notch Toughness in a New 5% Nickel Steel for Cryo­genic Purposes," Tech. Report No. C70-39,2, (Pamphlet), American Society for Metals, 1970.

10. Marschall, C. W., Hehemann, R. F., and Troiano, A. R., "The Charac­teristics of 9% Nickel Low Carbon Steel," Trans. ASM, 55 (1), 135-148 (1962).

11. Pense, A. W., Kottcamp, E. H., and Stout, R. D., "A Study of Subcri­tical Embrittlement in Pressure Vessel Steels," Weld. Jnl., 42 (12), 541s-546s (1963).

12. "Impact Testing of Metals," ASTM, STP 466, June 1969, 315 p. 13. Omer, G. M. and Hartbower, C. E., "Transition Temperature Corre­

lation in Constructional Alloy Steels," Weld. Jnl., 40 (10), 459s-467s (1961). 14. Kanazawa, T., et al., "An Improved Charpy Test-The Pressed­

Notch-Boundary Charpy Test," Report SR 6108, University of Tokyo, 1961. 15. Wullaert, R. A., "Applications of the Instrumented Charpy Impact

Test," Impact Testing of Metals, ASTM, STP-466, p. 148, 1970. 16. Roper, C. R., Koschnitzke, K. A., and Stout, R. D., "Quantitative Ef­

fect of Section Size on Transition Temperature," Weld. Jnl., 46 (6), 254s-258s (1967).

17. --, "Tentative Method of Test for Plane Strain Fracture Tough­ness of Metallic Materials,'' (ASTM Designation E399-70T) American Soci­ety for Testing and Materials, Philadelphia, Pa.

18. --·, "Methods for Crack Opening Displacement (COD) Testing," British Standards Institution DD19:1972.

19. McCabe, D. E., "Fracture Toughness Evaluation by R-Curve Meth­ods," ASTM STP 527, 112, 1973.

20. Corten, H. T., "Fracture Toughness--Proceedings of the 1971 Na­tional Symposium on Fracture Mechanics,'' Part II, ASTM STP 514, 19lp, 1972.

21. Lange, E. A., Puzak, P. P., and Cooley, L. A., "Standard Method for the \-inch Dynamic Tear Test," NRL Report 7159, Aug. 27, 1970.

22. Judy, R. W., Jr. and Goode, R. J., "Ductile Fracture Equation for High-Strength Structural Metals," Naval Research Laboratory Report 7557, April 3, 1973.

23. "Nickel Alloy Steel Plates,'' Nickel Alloy Steels Data Book, Section 3, Bulletin B, The International Nickel Co., 1972.

24. Huettich, N. J., Pense, A. W., and Stout, R. D., "The Toughness of 2¼% and 3½'11, Nickel Steels at Cryogenic Temperatures," WRC Bull. 165, Weldin.& Research Council, Sept. 1971.

25. Clark, W. G., Jr., "Effect of Temperature and Section Size on Fatigue Crack Growth in Pressure Vessel Steel," Jnl. Materials, 6 (1), 134-149 (March 1971).

26. Gross, J. H., Kottcamp, E. H., and Stout, R. D., "Effect of Heat Treatment on the Microstructure and Low Temperature Properties of Pres­sure Vessel Steels,'' Weld. Jnl., 37 (4), 160s-168s (April 1958).

2'1. KMN Commission, "Studies on 9-Percent Nickel Steel for MOSS­Type Liquified Natural Gas Carriers,'' Nippon Steel Corporation, March 1973.

28. "Metallurgical Properties of Armco Cryonic 5 Steel,'' Armco Steel Corporation, 1971.

29. Pense, A. W., "Aging Behavior of 9% Nickel Steel,'' Unpublished Re­search, Lehigh University, 1960.

30. Sarno, D. A., Private Communication. 31. Bentner, W. P., Jr. and Murphy, W. J., "Explosion Bulge and D_rop

Weight Tests of Quenched and Tempered 9-Percent Nickel Steel," ASME Paper 67-Pet-38.

32. Sakai, et al., "Studies on 9% Ni Steel for LNG Carriers,'' presented at the ASTM Symposium on Properties of Materials for LNG Tankage, Bos­ton, Mass., 21-22 May 1974.

33. Barsom, J. M. and Rolfe, S. T., "Correlations Between K1. and Char­PI V-Notch Test Results in the Transition Temperature Range," ASTM STP 466, p. 281-302. .

34. Tenge, P. and Solli, 0, "9 Percent Nickel Steel in Large Spherical Tanks for Moss-Rosenberg 87600 M3 LNG Carrier," Eur. Shipbuilding, XXI (1), 9-25 (1972). .

35. Murayama, N., "Fracture Toughness of Cryogenic Steels," M.S. The­sis, Lehigh University, 197 4.

36. Barsom, J.M., Imhof, E. J., and Rolfe, S. T., "Fatigue Crack Propaga­tion in High Yield-Strength Steels," Eng. Fracture Mech., 2 (1971).

37. Hahn, G. T. and Rosenfield, A. R., "Plastic Flow in the Locale of Notches and Cracks in Fe-3 Si Steel Under Conditions Approaching Plane Strain," Ship Structure Committee Report SSC-191, Nov. 1968.

38. Stout, R. D. and Gross, J. H., Private communications to Internation­al Nickel Co., 1954-1959.

39. Haynes, A. G., Firth, K., Hollox, G. E., and Buchan, J., "Strength and Fracture Toughness of Nickel-Containing Steels,'' ASTM Symposium on Properties of Materials for Liquid Natural Gas Tankage, Boston, May 1974.

40. Doty, W. D., Private communication to PVRC Subcommittees of data submitted to ASME.

41. --, Technical Data of 9% Ni (Supplement), The Nippon Steel Cor­poration, April 1973.

42. Takashima, H., Yoshimura, H., and Tanaka, K., "Fatigue and Frac­ture Toughness of 9% and 5½% Nickel Steel," Paper No. 30 Welding Low Temperature Containment Plant Conference, The British Welding Insti­tute, London, Nov. 1973.

43. Carter, W. P. and Harrison, J. D., "The Use of 9% Nickel Steel for LNG Application,'' Paper No. 9 Welding Low Temperature Containment Plant Conference, The British Welding Institute, London, Nov. 1973.

44. Bunk, A. P., Private communication. 45. Sarno, D. A., McCabe, D. E., and Heberling, T. G., "Fatigue and Frac­

ture Toughness Properties of 9% Nickel Steel at LNG Temperatures,'' ASME Petroleum Engineering Conference, Los Angeles, Sept. 1973.

46. Bucci, R. J., Green, B. N., and Paris, P. C., "Fatigue Crack Propaga­tion and Fracture Toughness of 5 Ni and 9 Ni Steels at Cryogenic Tempera­tures,'' Progress in Flaw Growth and Fracture Toughness Testing, ASTM STP 536, pp. 206-228, 1973.

47. Morgan, W. E. and Norman, P. L., "A High Strength Nickel-Based Welding Consumable Development for 9% Nickel Steel," Paper No. 3, Weld­ing Low Temperature Containment Plant Conference. The British Welding Institute, London, Nov. 1973.

48. Sarno, D. A., Bruner, J. P., and Kampschaefer, G. E., "Fracture Toughness of Armco Cryonic 5 Steel Weldments" Paper No. 7. Welding Low Temperature Containment Plant Conference. The British Welding Insti­tute, London, Nov. 1973.

49. Vishnevsky, C. and Steigerwald, E. A., "Plane Strain Fracture Tough­ness of Some Cryogenic Materials at Room and Subzero Temperatures," Fracture Toughness Testing af Cryogenic Temperatures, ASTM STP 496, Aug.1971.

50. Omen, A., Matyja, H., and Buoien, T., "Structural Changes and Me­chanical Properties of Simulated lfeat-Affected Zones in 9% Ni Steel," Welding Low Temperature Containment Plant Conference, The British Welding Institute, London, Nov. 1973.

51. Gideon, D. N., Favor, R. J., Koppenhafer, A., Groner, H. J., and McClure, G. M., "Investigation of Notch Fatigue Behavior of Certain Alloys in the Temperature Range of Room Temperature to -423F," Tech. Doc. Rpt. No. ASD-TDR-62-351, Wright Patterson Air Force Base, Ohio, Aug. 1962.

52. --, Letters to ASTM Committee Al, Subcommittee XI, by inter­ested parties, 1967-68.

53. Kampschaefer, G. E., Private communication to PVRC Pressure Ves­sel Steels Subcommittee Project Director, 1970.

54. --, "Properties of Weldments in Quenched and Tempered 3½ Nickel Steel," The International Nickel Co., July 1969. ·

55. Ward, William V., Private communication, The International Nickel Company, Inc.

Cryogenic Nickel Steels 39

Program "The Static and Dynamic Toughness of 5% and 9% Nickel Steels"

"Fracture Toughness Characterization of Cryogenic Steel Welds"

"Test Program for Candidate LNG Materials"

"The Welding of Cryogenic Steels for Liquid Gas Storage Vessels"

"Design Allowables of Pressure Vessel Materials Based on Cryogenic Proper-ties"

"Interpretive Report on the Characteris-ties of Cryogenic Nickel Steels"

"Evaluation of 5% Nickel Steel (A-645)"

40

~------Participanis------~ Sponsorship

Pressure Vessel Steels Subcommittee, Ma­rials Div., Pressure Vessel Research Committee

Fabrication Division, Pressure Vessel Re­search Committee

Metal Properties Council with co­operation from In­dustry and Agencies

Sponsor group formed by about 20 industry members of The Welding Institute

ASME Boiler and Pressure Vessel Code

Pressure Vessel Re-search Committee

Granges/ Armco

Execution Lehigh University, Department of Materials Science, Bethlehem, Pa.

A. W. Pense

Lehigh University, A. W. Pense

Martin-Marietta Corp., Denver Div.

The Welding Insti­tute, Cambridge, England

Special Task Group on Low Tempera-ture Design Allow-ables

Lehigh University, R. D. Stout A. W. Pense

Det Norske Veritas, Oslo, Norway /Royal Institute of Stockholm

WRC Bulletin 205

Table 24-A Summary of Current Research and Data

Work start date

Fall 1971

Fall 1972

Not yet estab­lished

December 1973

Fall 1973

Jan. 1974

Spring 1974

~--Synopsis of program---

Objectives To determine strain rate sensitivity by establishing both static and dynamic fracture toughness data

To document the frac­ture toughness of weld­ments of the same steels as in above pro­gram

To determine the fatigue cracking char­acteristics of candi­date LNG alloys, in base plate and welded panels

To compare the prop­erties of four cyrogenic steels (weldments); to assess various high deposition welding processes; to develop data on which higher design strengths may be based

To develop procedures under which the Code can establish and ap-prove increased design allowable stresses of certain cryogenic ma-terials at low tern-peratures

To summarize and evaluate characteris-ties of ferritic, nickel containing, cryogenic steels

To determine the suit-ability of 5% Ni steel for free standing LNG tank design

Alloys 9% Ni Steel (A-553) 5% Ni Steel (A-645)

Same as above

9% Ni Steel Quench and Temper Al Alloy 5083-0

9% Ni Steel Quench and Temper 9% Ni Steel Double Normalize 5% Ni Steel (A-645) 5¼% Ni Steel (N-TUF­CR196)

9% Ni Steel 8% Ni Steel 5% Ni Steel 5083 Al Alloy

9% Ni 8% Ni 5% Ni 3¼% Ni 2¼% Ni Related fer-ritic grades

5% Ni Steel (A-645)

Gathering Programs for LNG and Related Applications

Product forms

Plate: 1½ in. 2 in. 3 in.

Same as above

1 in. Plate 2 in. Plate 2 in. Plate 4 in. Plate

12mm Plate (~0 .5 in.) 26mm Plate (~1.0 in.)

Plate Pipe Tubing Forgings

To include data on all product forms, as available

Plate to 2 in. thick

Synopsis of program

Welding None

Gas-Metal-Arc Inconel 82 Wire Shielded 'Metal Arc Inco Weld B Electrode

Gas-Metal-Arc Butt Welds Inconel 92 Filler Gas Metal Arc Butt Welds 5183 Filler

Manual Metal Arc Mechanized Metal Arc Submerged Arc Electro-Gas Various con-sumables, posi-tions, deposi-tion rates, edge preparation, gas mixtures, etc. Examination of ferrite filler Stress values to be established for both welded and non-welded structures

Properties of weldments to be included

Welded wide­plate

Test temps.

-150° F to -320° F

Same as above

R.T.to -270° F

RT -162° C (-260° F)

-196° C (-320° F)

RT to -320° F

All temps. below RT as data are available

RT to -320° F

Type of data to be developed

Static Tensile Cbarpy V Notch Drop Weight Static K.-Compact

Tension Dynamic K.-3 point

load-instrumented J-integral COD Resistance Curve Static Tensile Static K.-Compact

Tension Dynamic K.-3 point

load-instrumented COD J-Integral Resistance Curve For weldment and coarse grained HAZ Static Tensile Stress-strain Fatigue crack growth rates-different bend/ tensile ratios- different aspect ratios of surface flaw.cracks

cycles to penetration crack shape at pene-tration crack extension rates after penetration

Static Tensile Cbarpy V Notch COD Critical Defect Size Fatigue Crack Propaga-

tion

Static Tensile properties as a function of test temperature

Yield and tensile strength trend curves

Metiµlurgy Tensile Properties Fracture Toughness Fatigue Welding Service Applications

Static Tensile Nil Ductility Transition Fatigue Crack Growth

Rates Crack Geometry Critical Crack Size COD

Final report PVRC Report

Data to be combined in above report

MPC Report

Welding Institute Report to Sponsor Group

Design allowables based on increased strength at cryogenic temperatures will be included in ap-propriate tables of Sec-tion VIII, Pressure Ves-sels, ASME Boiler and Pressure Vessel Code

PVRC Interpretive Report

To be made public. Details not available

Cryogenic Nickel Steels 41

Program "Fatigue Crack Growth Characteris­tics of 5% Ni Steel (A-645)

"The Mechanical Properties of Struc-tural LNG Alloys"

"Elastic Modulus Measurements of Structural LNG Alloys"

"Evaluation of Frac-ture Toughness Characteristics of a New Cryogenic Steel"

42

Table 24 (continued)

Work start date

~--,Synopsis of program.---~-----Participants-----~

Sponsorship Armco Steel Corp.

The Maritime Administration (MARAD)

National Bureau of Standards

Nippon Steel, Japan

Execution Battelle Memorial Institute, Columbus, Ohio

National Bureau of Standards, Boulder, Colo.

R. Reed

National Bureau of Standards,

Ledbetter Maimon Weston

Lehigh University, A. W. Pense N. Murayama

Dec. 1973

Fall 1973

Fall 1973

Jan. 1974

Objectives To determine rates of sub-critical fatigue crack growth rates in candidate LNG alloy

To conduct fracture toughness screening tests on candidate LN G materials

To make accurate measurements of elas-tic moduli over a range of cryogenic tempera-tures

To determine static and dynamic fracture toughness data, base plate and weldments

Table A-Conversion Factors for Property Values Used in Report

~--------S.tatic Strength--------~ From ksi kg/mm 2

N/mm 2

MPa

To: ksi kg/mm• 1 0.703 1.42 1 0.145 0.102 0.145 0.102

N/mm• 6.89 9.8 1 1

MPa 6.89 9.8 1 1

~------Notch Toughness Energy'------~ From ft-lb kg-m Joules

To: ft-lb kg-m 1 0.139 7.2 1 0.74 0.102

Joules 1.36 9.8 1

~----Fracture Toughness and Fatigue t:,.K----~ From ksi-in. 112

N/mm 312

kg/mm 312

MPa-m 112

To: ksi-in." 2 N/mm 312 kg/mm 312

1 34.7 3.54 0.0288 1· 0.102 0.282 9.8 1 0.91 31.6 3.2

WRC Bulletin 205

MPa-m 112

1.10 0.0316 0.31 1

Alloys

5% Ni Steel (A-645)

Al Alloy 5083 9% Ni Steel 5% Ni Steel (A-645) 5.5% Ni Steel (N-TUF CR196) 3.5% Ni Steel Al alloy 5083 9% Ni Steel 5% Ni Steel (A-645) 5.5% Ni Steel (N-TUF CR196) 3.5% Ni Steel

N-TUF-CR196 (5.5% Ni Steel)

Table 24 (continued)

Synopsis of program Product Test Type of data

forms Welding temps. to be developed Final report Base Plate GMAW with RT and Static Tensile Presented as corn-¼in.thick Inconel 92 -275° F da/dn at constant am- bined Armco-Battelle ¼in. Electrode plitude fatigue load- Paper at Symposium on 1 in. Vertical ing Structural Materials for

da/dn under spectrum Liquefied Natural Gas fatigue loading Application, sponsored

Characterization of flaw by Low Temperature shape changes in Panel of the Joint Com-fatigue mittee on Effect of

Surface flaw fatigue Temperature on Prop-crack growth charac- erties of Metals, ASTM teristics Committee Week,

Boston, Mass., May 19-24, 1974

Plate Welded and RT to Static Tensile NBS Report to nonwelded -320° F Kie MARAD. Probably specimens to J-Integral restricted distribu-be tested. Fatigue Crack tion One weld pro- Propagation cedure for each alloy to be chosen

Plate RT to Youngs Modulus Presented at Sym-Bar 4° K Shear Modulus posium on' Structural

Bulk Modulus Materials for Liquefied Natural Gas Applica-tions, sponsored by Low Temperature Panel of the Joint Committee of Effect of Temperature on the Properties of Metals, ASTM Com-mittee Week, Boston, Mass., May 19-24, 1974

Plate Shielded RT to Static Tensile Tentatively scheduled 1 in. thick Metal Arc -320° F Static Kc-Compact as supplement to the

Inco Weld Tension Lehigh PVRC Report B Electrode Dynamic Kc-3 point on Testing of 9% and

load-instrumented 5% Nickel Steels COD J-lntegral

Cryogenic Nickel Steels 43