the influence of foundry variables on nodule count … · higher recovery with the plunge...

RESEARCH PROJECT No. 12

THE INFLUENCE OF FOUNDRY VARIABLES ON NODULE COUNT IN DUCTILE IRON

BY

J.F. WALLACE, PIXI DU, HUA-QIN SU

/ DUCTILE IRON SOCl ETY

Issued by the Ductile Iron Society for the use of its Member Companies - Not for General Distribution

DUCTILE IRON SOCIETY Box 1105 - Mountainside, N.J. 07092

APRIL 1984

RESEARCH PROJECT No. 12

THE INFLUENCE OF FOUNDRY VARIABLES ON NODULE COUNT IN DUCTILE IRON

BY

J.F. WALLACE, PIXI DU, HUA-QIN SU

/ DUCTILE IRON SOCIETY

Issued by the Ductile Iron Society for the use of its Member Companies - Not for General Distribution

DUCTILE IRON SOCIETY Box 1105 - Mountainside, N.J. 07092

APRIL 1984

DUCTILE IRON SOCIETY RESEARCH PROJECT THE INFLUENCE OF FOUNDRY VARIABLES ON NODULE COUNT IN DUCTILE IRON

FOREWORD

The hardness, mechanical strength, and machinability of ductile iron are affected by the pearlite and carbide contents of the matrix. The volume, number, and distribution of graphite nodules influence the quantity of pearlite and carbide.

The Ductile Iron Research Committee considered it necessary to obtain a better quantitative understan- ding of all the factors which influence nodule count. It was recognized that various section thickness can produce different nodule counts and corresponging varia- tions in hardness in the same casting. Foundry process variables can effect nodule count and may increase or decrease the nodule count variation for section size, resulting in differences in hardness. Other variables which affect nodule counts are the chemical analyses of the alloys used in treating and post inoculating.

Purpose This project was designed to study the influence of foundry variables including: - Section thicknesses - solidification rate - Three treatment methods - Post inoculant quantities - Ladle and sprue inoculation - Pouring Temperature and fading time - Type molds - green sand vs. no bake - Base sulfur levels - Magnesium content - Carbon equivalent level

Experimental Approach: Separate concurrent projects were planned pursuing a controlled pattern of variables casting step specimens with six thickness levels from I / , to 2 inches.

Project No. 13 reports on the influence of alloy variables.

Summary of Conclusions: SECTION THICKNESS, through its effect on solidification rate, showed the most positive influence by increasing nodule count with decreasing thickness; 1 l/2 inch sections showed approximately 100 nodules per mm2 '/, inch sections showed approximately 200 nodules per m m2 '/, inch sections showed approximately 300 nodules per m m2 '/, inch sections showed approximately 400-1000 nodules per mm2

Carbides were frequently found in the '/, inch sections. End effects increased the cooling of the 1/, and 2 inch sections so that I/, to 1 I/, inch sections were considered more accurate.

Treatment Methods The lnmold magnesium treatment provide higher nodule counts than plunging or sandwich treatments. The method used in sandwich treatment was non- conventional and the results could be questionable.

POST INOCULANT AMOUNT showed positive effect. Increasing the amount of 75% FeSi post inoculant from .25% Si to .75% Si increased nodule count roughly 150 noduleslmm2 in all sections from 1/2 to 2 inches. The inch section increased 400 noduleslmmZ and the I/, inch section increased 300 noduleslmm2.

Ladle and Sprue Inoculation Sprue inoculation produced higher nodule counts than ladle inoculation. The use of a special ladle inoculant (VP216) and downsprue post inoculant (Germalloy) resulted in the highest nodule count. Titanium contents should be viewed with caution due to cell boundry nitrides and carbo-nitrides effect on machinability as well as potential loss of properties when nodularity decreases.

(The technique used in ladle inoculation influences the effects such as thorough mixing and hot iron.)

Pouring Temperature and Fading Time Under foundry conditions, time after inoculation as well as iron temperature can be major factors in the decrease in nodule count and tendency to form carbides. The effect of inoculation fades with time and nodule count decreases. Low pouring temperatures promote carbides even with high nodule counts. Low temperature during inoculation does not permit the inoculant to dissolve clean and uniform. The nodule count for high temperature (2600 F) was lower than low temperature (2400 F), but both high and low were not as high as 2500 F.

Type Molds - Green Sand vs No Bake The no-bake bonded molds provide a somewhat slower rate of solidification than green sand molds in the same plate thickness, however the difference in nodule count is very small. The green sand is higher in each section.

Base Sulfur Levels The nodule count in the inmold process appeared higher for higher base sulfurs, however the quantity of treatment alloy was increased which could increase the nodule count. The nodule count for plunging treatment increased slightly for higher base sulfurs. The use of higher sulfur contents to increase nodule count may not be advisable due to larger amounts of treatment alloy required and potential increase of dross. Fade

times may become variable as well. Higher sulfur may reduce the active magnesium and increase nodule count. Production experience indicates that as magnesium content goes down, nodule count goes up. Very low sulfur contents can result in excessive magnesium with corresponding carbide tendencies.

Magnesium Content Magnesium analysis of treated irons does not indicate active or inactive magnesium compounds, therefore residual magnesium may be either form. The lower nodule count occurred with lower magnesium content, however the nodularity was also low. Larger amounts of alloy in the inmold process produced higher nodule counts especially with increased sulfur. These results should be evaluated with caution.

Carbon Equivalent Level The quantity of nodular graphite increases with carbon level. Caution must be used when selecting carbon level. A minimum carbon is required to avoid micro- shrink and a maximum must be recognized to obtain desired properties. Carbon equivalence can be mis- leading as to the effect on properties.

Lyle R. Jenkins Technical Director Ductile Iron Society

TABLE OF CONTENTS

FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

MATERIALS AND PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MOLDSCAST 4

METALTREATMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 HEATS CAST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 METALLOGRAPHIC EXAMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

RESULTSAND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 CHEMICAL ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 MICROSTRUCTURAL EXAM INATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 MAGNESIUM TREATMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 COOLING RATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 POSTINOCULATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 CARBON EQUIVALENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 RATIO OF RARE EARTHS IN INMOLD ALLOY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BASESULFURCONTENT 7 RESIDUALMAGNESIUM CONTENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 CARBIDEFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

INFLUENCE OF PROCESSING FACTORS AND COMPOSITION ON THE NODULE COUNT OF DUCTILE IRON

JOHN F. WALLACE, PIXI DU, HUA-QIN SU CASE WESTERN RESERVE UNIVERSITY

MATERIALS AND PROCEDURES A total of three heats were melted in either a 1500

pound or 500 pound basic lined induction furnace from charges of ductile iron scrap, low impurity pig iron, steel and ferroalloys. The iron was melted, brought to a suitable superheat of about 2800° F in the induction furnace and tapped sequentially into a small preheated clay-graphite ladle. When three castings were poured from the ladle, about 100 pounds was tapped into the furnace. This weight was reduced proportionately when two and one casting were poured from the ladle. The plunging treatments with magnesium were conducted in the ladle into which the furnace was tapped. The sandwich treatment required pouring into a second preheated ladle to obtain the desired speed of filling the ladle.

Molds Cast The molten iron from the ladle was poured into sand

molds to produce an unrisered step block casting that weighed 27 pounds each including the gating system. This casting contained six different section thicknesses that varied from to two inches in thickness, as illustrated in Figure 1. The different section thickness provided a considerable variation in cooling rates for all of the irons studied. The location of the three ingates into the mold cavity is indicated. The molds were usually rammed with a green sand facing, although a few molds were produced from a no-bake binder. Both types of molds used an AFS 38 fineness New Jersey silica sand. The green sand facing contained 3% seacoal, 3.5% water and 5% western bentonite. The no-bake molds were bonded with 2% phenolic resin set with a 0.6% acid catalyzer.

Metal Treatment The magnesium treating processes included; plung-

ing, sandwich treatment and lnmold treatment with a variety of postinoculation treatments. The plunging was into the ladle tapped from the furnace but the sandwich required reladling. A magnesium alloy addition of 2.2% was employed with the sandwich treatment compared to a2.6% magnesium alloy addition for plunging. The larger alloy addition was used because of reports of a somewhat higher recovery with sandwich treatments. The results, however, showed a somewhat higher recovery with the plunge treatment, so this treatment produced a higher final magnesium content. The lnmold reaction chamber was placed in the runner, two inches from the downsprue and was designed with an

efficiency factor of 0.032 for both lnmold alloys tested (9). The details of the lnmold gating, chamber size, inlet and outlet are shown in Figure 2. The ingates were the same design shown in Figure 1 for all castings. The plunge and sandwich treatments were performed with a nominal 5% Mg-FeSi, 0.57% cerium-containing alloy. Two different lnmold alloys were used with different ratios of cerium and lanthanum. The composition of these alloys are listed in Table 1.

The postinoculation included both ladle and sprue or runner additions. Ladle additions involved various amounts of foundry grade 75% ferrosilicon and a special proprietary inoculant (VP 216). These additions were made to the ladle together with the magnesium treating alloy as a one step treatment (10). Postinocula- tion was also conducted in the downsprue and runner. Germalloy and lnotab pellets were inserted in the downsprue, as shown in Figures 3A and 38. Standard 75% foundry grade ferrosilicon was placed in the runner, as illustrated in Figure 3C. The composition of the postinoculants is shown in Table 1. The amount of silicon added by the sprue and runner inoculants was 0.1 1 % from the six Inotabs, 0.14% from the 23 gram Germalloy pellet and 0.1 O/O Si from the 75% FeSi in the runner. The wide variety of magnesium and postinoculation treatments resulted in silicon varia- tions that were compensated for by 75% Si, FeSi additions as needed.

Heats Cast Three heats weighing 1100 pounds, 400 pounds and 650 pounds were cast in this investigation. The details of each heat showing the pouring sequence, pouring temperature, magnesium treatment and postinoculation are listed in Tables 2-4 for heats A-C respectively. The pouring temperature of the molds was monitored by immersion thermocouples in the ladle before pouring the castings. Heat A primarily studied different methods of magnesium treatment and postinoculation. It included plunge, sandwich and In- mold treatment with ladle and sprue postinoculation. Heat B was designed to study the effect of carbon equivalent on the nodule count. A low carbon equivalent (4.08% CE) iron was melted and cast in the first part of the heat and carbon added to the furnace to increase the carbon content of the latter part (4.60%) of the heat. The plunge and lnmold treatment with various postinoculation were used. Heat C. was conducted to determine the influence of base sulfur and final magnesium contents on the nodule count. The first group of castings were poured at the standard sulfur

level (.015-.02O0/0). Then, the heat was desulfurized at 2850° F for ten minutes in the furnace with calcium carbide and a lime and fluorspar slag. The sulfur content for the second group of castings was 0.007% S. Finally sufficient FeS was added to the furnace to raise the base sulfur level to 0.037% and the last group of castings were poured. Plunge and lnmold magnesium treatments with different postinoculations were employed. The amounts of magnesium treatments were varied at the standard sulfur level to obtain different final magnesium contents to assess the effect of this element on nodule count. Suitable ferrosilicon and carbon additions were made during the three heats to compensate for the loss of silicon and carbon because of oxidation of the molten iron in the induction furnace and silicon additions were made to keep the silicon level fairly constant.

Metallographic Examination After the castings had cooled overnight in the mold,

they were shaken out and sectioned to determine the metallographic structure in the as-cast condition. Six specimens were removed from the step block casting located in the center of each step, as shown in Figure 4. The microstructure of graphite was examined in the unetched condition; the matrix structure and amount of carbide were determined after etching with 4% nital. The graphite structure, amount of pearlite, ferrite and carbide in the matrix was assessed visually using standard charts (3,11-13) for comparison. When both feathery carbides and ledeburite were present, the sum of these was reported as percent carbide.

Graphite size and nodularity were evaluated visually by comparison with the reference pictures shown in Figures 5 and 6 (14). Graphite size was designated by a number of 1 through 6 of decreasing size (Figure 5). When more than one size was present, this was indicated as two numbers with the more prevalent size listed first. Nodule size and nodule count were measured with the structure projected on a ground glass screen at 100X. The nodule count was determined by counting all nodules that were larger than I/,, inch in diameter on the enlargement within the area of 100 x 100 mm. Therefore, all nodules greater than 7.8 microns in diameter were counted. Four readings were taken for each specimen and averaged to report the nodule count.

RESULTS AND DISCUSSION Chemical Analysis

The results of the chemical analysis are listed in Tables 5A, B and C for Heats A-C respectively. The samples of base iron were taken from the furnace and poured into a chill mold. Sampling was made after each compensation for carbon and silicon losses. The samples of treated iron were taken both from the ladles and from the lnmold castings. The carbon content of Heat A was somewhat lower than the desired level of 353.6%. The remaining compositions are close to the desired levels.

The variation in carbon equivalent obtained on Heat B varied from 4.04 to 4.11% on the low side to 4.57-4.68% on the high side. The silicon levels were 2.30-2.50% and the magnesium contents varied from 0.03 to 0.045%. In Heat C, the range of residual magnesium levels was 0.030 to 0.068. The base sulfur levels varied from 0.007 to 0.038%. The carbon equivalent in Heat C was about 4.4%.

Microstructural Examination The results of the graphite structure, matrix and car-

bide examination are listed in Tables 6A-6C for Heats A-C respectively. The nodularity on Heat A and B is usually over 90% Type I or about 100% except in a few cases where it decreased to 85% Type I with 15% Type 11. Since Type I and II nodules are generally added in considering nodularity, the irons in Heat A and B have essentially 100% nodularity. In Heat C, some of the heavier sections at the lower magnesium contents did contain considerable amounts of compacted graphite. In these cases the nodularity decreased to 50-55% for the one and two inch thick sections at the lowest magnesium level.

The results clearly show the effect of the significant variables on the nodule count. With the generally high nodularity of these castings, the differences in nodule count could be clearly established. The influence of these variables is listed separately in the following sections.

Magnesium Treatment The relative effect of plunging, sandwich treatment

and the lnmold process on the nodule count was studied in Heat A. The plunge and sandwich treatments were employed with four different postinoculations. These included the addition of 0.45 and 0.75% Si as 75% foundry grade ferrosilicon and sprue inoculation with Germalloy and Inotabs. A higher nodule count was obtained with the plunge than with sandwich treatment in all cases. However, the final magnesium content of the ductile iron averaged 0.068% with a 49% recovery for the plunging treatment compared to an average of only 0.05% final magnesium and a 43% recovery for the sandwich treatment. This higher nodule count occured at all section sizes for all treatments, as illustrated in Figure 7A and B and 8A and B. It has been pointed out in the literature(l5) that plunging is the preferable method of magnesium treatments.

When the nodule count obtained from lnmold magnesium treatments is compared to ladle treatments, a consistently higher nodule count is attained with the lnmold treatment. The data for nodule counts in Table 6A and the bar graph drawn in Figure 9 illustrate this effect. The results show that lnmold magnesium treatment provides a finer nodule count than plunging or sandwich treatments even though only 1.4% magnesium alloy was used compared to 2.2 and 2.6% and even though no postinoculation was employed for lnmold treatments. The average nodule

counffbi the 1/4, 1/2, 1 and 11/2 inch sections shown by when the pouring temperature is increased from about the bar graphs in Figure 9 demonstrate the highest 2500 to 2600° F. nodule count for lnmold treatments over all ladle H ~ ~ ~ ~ ~ ~ , the average nodule count at a pouring treatments, even when effective sprue inoculation was temperature of 24000 F (217 noduleslmm2) is slightly used for the irons treated with magnesium in the ladle. lower than at 25000 F (231 nodules/sq. mm at 24000 F). The 2 and '18 inch thick plates were in This behavior is attributed to the fading effect that ocur- calculating the average nodule count in Figure 9 red when the castings were produced rather than the in- because these have the nodule fluence of pouring temperature. The procedure in Heat increased from the heat loss through the ends of the A was to treat the metal by plunge or sandwich at high step plate casting. This effect of increasing the mdule temperature and then to pour the three molds in turn as count on these end plates is shown in Figures and 8. 2600, 2500 and 24000 F successively. It was necessary

The higher nodule count attained with lnmold to hold the metal in the ladle until the desired pouring magnesium treatments compared to ladle magnesium temperatures were reached. This produced more of a treatments in ductile iron has been demonstrated in the fading effect on the last metal to be poured at 2400° F. literature (9,16). The very late magnesium treatment of This fading effect decreases the nodule count and off- this process apparently produces sulfide substrates for sets the influence of the lower pouring temperature. graphite nucleation that do not have sufficient time to The no-bake bonded molds provide a somewhat fade in the melt, so that high nodule counts are obtain- slower rate of solidification than green sand molds in ed without postinoculation. the same plate thicknesses. The no-bake molds con- Cooling Rate tained very little water in its binder compared to the

The primary means of varying the cooling rate in this 3.5% water in the green sand molds (17). This results in study was the different section sizes of the step plate a lower thermal conductivity for the no-bake mold. In casting (Figure 1). In all cases, as shown by the data in addition, no-bake binders have a small exothermic ef- Table6, Figures7,8 and subsequent figures, the nodule fect when filled with molten iron. For this reason, it count increased with decreasing section thicknesses. would be expected that the no-bake molds employed in Some inf!uence on the cooling rate was also exerted by Heat B would provide a somewhat lower nodule count the pouring temperature and type of mold. The I/, inch than the green sand molds poured under equivalent thick sections have extremely high nodule counts of conditions. This effect of mold type on the nodule 500-700 nodules per mm2 and even attain values as high count is demonstrated by the data plotted in Figure 10. as 1172 nodules per mm2. The nodule count changes Postinoculation only moderately for a section thickness of over '/2 inch. Ladle Postinoculation It has been shown previously that the nodule count increases with small diameter cast rounds and on other It be expected and has been rep0rted step block castings (3-5). A larger amount of under- elsewhere (5918) that the nodule count is increased by

cooling occurs in the lighter sections. This activates using larger amounts of silicon added as 75% foundry

more substrates for graphite nucleation and increases grade ferrosilicon as a ~os t i~ocu lan t . The steadily

the nodule count. The higher nodule count of the 2 inch higher nodule number obtained on the various section

compared to the 11/2 inch thick section observed for sizes as the amount of silicon as 75% foundry grade

numerous irons is attributed to the heat loss through ferrosilicon as a postinoculant is increased is il-

the end of the inch section. In fact, the shrinkage cavi- lustrated in Figure 11. As the amount of silicon is in-

ty obtained on the top surface of this step block mold creased from 0.25 to .45 to .6 to .75%, the number of

occurred on the 1 l/z inch thick section. nodules becomes steadily greater. It is pointed out that some other differences also exist in the processing of

The higher pouring temperatures also act to reduce the castings whose nodule count is plotted in Figure the solidification times. The influence of this ll. F~~ example, the magnesium alloy addition for the temperature could be determined from the data plotted plunge was higher for the .45OIO silicon postinoculation in Table 6A since the pouring temperature was than for the 0.25, 0.60 or 0.75% silicon postinoculation. deliberately varied from 2400-2450, to 2475-2550, and to ~~~~i~~ this fact, the nodule count increased steadily 2550-2680° F throughout the series of castings ~ roduc - for larger amounts of postinoculant. At a section size of ed on this heat. The average nodule count obtained in one inch, an increase in 0.101~ silicon post~nocu~at~on l/4 to 1 l/2 inch thick plates on these different castings as 75% foundry grade ferrosilicon increases the nodule has been calculated from this data and is shown in count about 40 noduleslsq. mm. Table 7. It would be expected that higher pouring temperature would have the effect of a thicker cast sec- and Runner

tion. Accordingly, the average nodule count would be Inoculation in the Wrue and runner is to be expected to decrease with higher pouring considerable more effective than ladle postinoc~lation temperatures. This decrease does occur from 231 to (5,181. It was shown in Heat A from the data in Table 6~ 204 average number of nodules per square millimeter and the bar graphs of Figure 9 that sprue inoculation

provides a higher nodule count after either plunging or sandwich magnesium treatments c~mpared to ladle inoculation of up to 0.75% silicon as 75% foundry grade FeSi. It was also observed that the sprue postinoculation with Germalloy that added 0.14% Si was more effective than the 0.11 O/O Si from the 6 lnotabs in Heat A. This difference may well be more attributable to the aluminum and magnesium content of these additions rather than their silicon content. The highest values of nodule count were obtained in casting 307 from Heat C when 0.25 Si. as VP 216 as a ladle postinoculant plus 0.14% silicon as Germalloy sprue inoculant were employed together. In this case, the average of the nodule count on section sizes l/4 through ll/z inches was 331 for a plunging magnesium treatment. This nodule count is well above thevalues reported in Figure 9. The use of 0.75% Si as 75% ferrosilicon in the ladle plus 0.1 % Si as 75% FeSi in the runner also produced a high nodule count in Heat B. When castings No. 204 and 205 are compared in this heat, both irons were sub- jected to similar plunge treatments and both had 0.75% Si as 75% FeSi added to the ladle. The additional runner postinoculation of casting 204 increased the average nodule count for Ih to 1 '/2 thick sections from 140 to 191 nodules per sq. mm.

Carbon Equivalent The different carbon equivalent values of the iron

poured in Heat B can be compared to assess the effect of this variable on nodule count. The results of this comparison for two castings (205 and 208) are shown for the I/, through 2 inch thick sections in Figure 12. Both of these castings were produced by a plunging magnesium treatment with 2.6% magnesium alloy and a ladle postinoculation of 0.75% Si as 75% FeSi. The higher carbon equivalent iron has a higher nodule count at all thicknesses although the difference is small except for the 1/, thickness. The difference in carbon equivalent between these two irons is considerable or 4.08 to 4.63% to produce the higher nodule count. In fact 4.63% is high enough so that difficulty with carbon floatation in heavier sections would be expected. It is apparent from this that the carbon equivalent is not as significant a factor in influencing nodule count as other variables such as cooling rate, magnesium treatment and postinoculation except for the thinnest or 1/, plate.

Ratio of Rare Earths in lnmold Alloy Magnesium treatment with #3 lnmold alloy that con-

tained . lo% Ce and 0.70% La provided a consistently higher nodule count at sections over I/' inch thick compared to the standard #O lnmold alloy. The amount of this effect is shown in Table 6B (Heat B) and Figure 13. The standard alloy contains 0.30% Ce and 0.14% La, so the La:Ce ratio between the two varies from 7 for the #3 alloy to .47 on the standard alloy. These results are

generally similar to other published work (8,22). This difference is apparently associated with the potency of the rare earth sulfide substrates for graphite nucleation.

Base Sulfur Content The nodule count increases somewhat with the base

sulfur content of the molten iron. This effect appears to be greater with lnmold magnesium treatment than plunging treatment. However, some variation in the magnesium treatment also occurred because the higher sulfur contents require a higher magnesium treatment. The extent of this variation is indicated by the data in Table 6C (Heat C) and Figure 14A and B. It had been shown elsewhere (5) that low sulfur contents before treatment can increase the carbide forming tendency and reduce the nodule count. Since the substrates for graphite nucleation are sulfides, the need for a minimum sulfur content is apparent.

Residual Magnesium Content The amount of magnesium employed in the

magnesium treatment depends on the efficiency of the treatment, the base sulfur content and the desired final magnesium content. In situations where fading is a possibility, a higher final magnesium may be required. The data from Heat C shown in Table 6C and plotted in Figures 15A and B illustrate the effect of the final magnesium content on the nodule count for the lnmold and plunging magnesium treatment. The increased nodule count for all section sizes with the highest residual magnesium content of 0.065% and the lower nodule count for 0.04 and 0.03% magnesium is readily apparent for the lnmold treatment in Figure 15A. A similar effect of residual magnesium content on the nodule count is indicated for the plunging treatment in Figure 158. In this latter case, the postinoculation does vary somewhat, as shown in Table 6C and Figure 15B. However, the lowest nodule count occurred with the lowest final magnesium content and the highest amount of silicon (0.75O/0 Si) added as 75% ferrosilicon for postinoculation. This latter fact demonstrates that high final magnesium contents have a considerable effect on the nodule count. It has been shown in other work (5) that increasing the residual magnesium content from 0.02 to 0.05% increased the nodule count and decreased carbide formation in light sections. However, this earlier study (5) also indicated that magnesium contents higher than 0.05% reduced the nodule count and increased carbide formation (5). In the present investigation, the higher magnesium contents up to 0.065% for lnmold and 0.067% for plunging with 0.6% Si ladle postinoculation increased the nodule count compared to lower levels. It was observed, however, in Table 6C that the carbides increased in the lightest or I/, inch thick section with the higher magnesium contents of the castings made with the In- mold treatment (#301 and 302).

magnesium contents of the castings made with the In- mold treatment (#301 and 302).

Carbide Formation In Heats B and C, as shown by the data in Tables 6B

and C, the occurrence of carbides is mostly restricted to the thinnest or '1, inch section. A maximum of 5% carbides was measured in the l/4 inch thick plate. The occurrence of carbides in this thinnest section does not always follow the nodule count. In other words, higher nodule counts may not result in fewer carbides. The carbide percent is higher for the higher magnesium residuals after the lnmold treatment in Heat C(castings 301-303) even though the nodule count decreases with lower residual magnesium. However, for the lowest base sulfur iron, the carbide content is the highest for the lowest nodule count and 70% carbides were obtained with a low magnesium lnmold treatment of this lowest sulfur iron. The lower pouring temperature used for the highest sulfur iron (castings 313-315) produced the highest amount of carbides with the greatest nodule count. The small number of carbides in Heat B (except for casting 205), shows little correlation with nodule count. The 100% carbides in the '/, inch thick section of casting 205 occur with a fairly high nodule count of 432. It may have been the combination of the plunge treatment, low carbon equivalent and ladle rather than runner postinoculation that produced this latter result.

The carbides obtained in the castings in Heat A are mostly confined to the '/, inch thick section, although 20% carbides occurred in the inch thick section and 5% carbides in the l/2 inch section in casting 130. These carbides occurred more frequently with the lowest pouring temperature and show little correlation with nodule count.

This lack of correlation of nodule count with carbides has to be considered in the light of the thin section involved. Undercooling is to be expected during solidification in this '/, inch thick section. This undercooling produces more effective substrates for graphite nucleation but it also can become severe enough, particularly at low pouring temperatures, so that some of the liquid iron is cooled below the autenite-carbide metastable eutectic temperature. When this happens, carbide formation will occur.

CONCLUSIONS This systematic study of the influence of processing

factors, section size and composition on the nodule count in ductile iron permits the following conclusions.

1. The section size of the casting with a range of '/, to 2 inch plate thickness had a marked effect on the nodule count. The faster solidification rates obtained in the lighter sections produced a much higher nodule count in the range of 1/, to l/2 inch thick sections. The effect of section size was considerably reduced above a l/2 inch thickness.

2. The faster solidification times in green sand molds compared to no-bake bonded core molds increased the nodule count in the green sand molds slightly. The more rapid cooling with lower pouring temperatures increased the nodule count except when the waiting period to reach the lower pouring temperature increased the fading of the magnesium content.

3. The lnmold magnesium treatment provided higher nodule counts than plunging or sandwich treatments. The increased nodule counts attained with the plunging treatment compared to the sandwich treatment are attributed to the greater magnesium content of the treatment and higher efficiency of magnesium recovery.

4. Postinoculation increased the nodule count considerably. Sprue or runner postinoculation was more effective than ladle postinoculation. The nodule count increased considerably with larger amount of silicon (from 0.25 to 0.75% Si) as 75% ferrosilicon added to the ladle as a postinoculant. Increasing postinoculation from 0.25 to 0.75 raises the nodule count 2% times. The use of a special ladle (VP 216) and runner postinoculant (Germalloy) resulted in the highest nodule count.

5. The nodule count increased with higher base sulfur in the iron, higher residual magnesium contents and a higher La:Ce ratio in the lnmold treatment alloy.

6. The carbides were mostly confined to the thinnest of 7, inch thick section cast. The occurrence of carbides and the nodule count were not closely related in this thinnest section. Undercooling of this thin section during solidification acts to increase the nodule count but sufficient undercooling can result in carbide formation.

ACKNOWLEDGEMENT This research was made possible by a grant from the

Ductile Iron Society.

REFERENCES 1. R.K. Nanstad, F.J. Worzala and C.R. Loper, Jr.,

"Fracture Toughness Testing of Nodular Cast Irons", AFS Transactions, Vol. 82,1974, pp. 473-486.

2. C.R. Loper, Jr., "Processing and Control of Ductile Cast Iron", AFS Transactions, Vol. 77, 1969, pp. 1-7.

3. J.H. Doubrava, S.F. Carter and J.F. Wallace, "The Influence of Processing Variables on the Matrix Structure and Nodularity of Ductile Iron", AFS Transactions, Vol 89, 1981, pp. 229-250.

4. D.R. Askeland and S.S. Gupta, "Effect of Nodule Count and Cooling Rate on the Matrix of Nodular Cast Iron", AFS Transactions, Vol. 83, 1975, pp. 31 3-320.

5. W.J. Evans, J.F. Carter, Jr. and J.F. Wallace, "Factors Influencing the Occurrence of Carbides in Thin Sections of Ductile Iron", AFS Transactions, Vol. 89, 1981, pp. 293-322.

6. P.K. Busultkar, C.R. Loper Jr. and C.L. Baku, "Solidification of Heavy Section Ductile lron Castings", AFS Transactions, Vol. 78, 1970, pp. 429-434.

7. Private Communication 1978. 8. M.J. Lalich, "Effective Use of Rare Earths in

Magnesium Treated Ductile Cast Irons", AFS Transactions, Vol. 82, 1974, pp. 441-448.

9. W.W. Holden, C.M. Dunk, "The Practical Application and Economic Aspects of the lnmold Process in the United States", Transactions of European lnmold Process in the United States", Transactions of European lnmold Conference, 1981, pp. 256-274.

10. E. Campomanes and R. Goller, "One Step Treatment for Ductile Iron", AFS Transactions, Vol. 81, 1973, pp. 428-432.

11. ASTM Part 2, "Evaluating the Microstructure of Graphite in lron Casting", 1982, A 247-67.

12. Quality Control Committee 12-E Ductile lron Division, "Reference Microstructures for Measurement of Pearlite and Ferrite Content in Ductile lron Microstructures", AFS Transactions, Vol. 82, 1974, pp. 545-550.

13. E.F. Ryntz for Ductile lron Quality Control Committee 12-E, "Reference Microstructures for Visual Estimation of lron Carbide Content in Nodular Iron", AFS Transactions, Vol 82, 1974, pp. 551-554.

14. Metallgesellschaft AG Technische Verfahren MetallurgielGiebereitechnik.

15. R. Carlson, "Experiences with Plunging Open Ladle and Sandwich Methods", AFS Transactions, Vol71, 1963, pp. 638-640.

16. R. Sillen, "lnmold Nodularization with Delayed Pouring in Vertically Parted Molds", AFS Transactions, Vol. 87, 1979, pp. 191-194.

17. Y.D. Kim, "Phenolic Nobake Binders for Core and Mold Production", AFS Transactions, Vol. 84, 1976, pp. 287-294.

18. R. Helmick and J.F. Wallace, "Heavy Section Ductile lron Castings", Ductile lron Society, Report No. 8.

19. R.L. Mickelson and T.W. Merrill, "Experiments in Making Cerium Ductile Iron;;, AFS Transactions, Vol. 76, 1968, pp. 289-296.

20. 1. Karsay and R.D. Schelleng, "Heavy Ductile lron Casting Composition Effect on Graphite Structure", AFS Transactions, Vol. 69, 1961, pp. 672-679.

21. T.W. Parks Jr., N.G. Berry and C.R. Loper, Jr., "The Effect of Solidification Time and Section Size on the Mechanical Properties and Microstructure of High Carbon Ferrous Alloys", AFS Transactions, Vol. 76, 1968, pp. 565-572.

22. A.P. Alexander, A.F. Spengler, U.S. Patent No. 2,970,902.

23. M.J. Lalich and J.R. Hitchings, "Characterization of inclusions as Nuclei for Spheroidal Graphite in Ductile Cast Irons", AFS Transactions, Vol. 84, 1976, pp. 653-664.

TABLE 1: CHEMICAL COMPOSITION OF NODULARIZERS AND POSTINOCULANTS

NAME CHEMICAL COMPOSITIONS, % Si Ca Al Mg Eff. Mg Ce La+Other

Nod. Alloy for Sandwich and Plunge Process 45.4 1.20 1.07 5.26

Nodularizer O# lnmold Alloy 44.8 0.58 0.77 5.95 5.52 0.30 0.14La

3# lnmold Alloy 45.0 0.32 0.62 5.26 4.84 0.10 0.7La

Standard Foundry Grade 79.75 0.78 0.87 75% Fe-Si

Post- Foseco's lnotab 2 57.75 0.38 0.94 inoculant

Germalloy 76.0 0.60 3.50 0.75

TABLE 2: CASTING PROCEDURE ON HEAT A - 1100 POUND CHARGE

Pouring Ladle Casting Temp. No. N 0. OF

Sandwich Processing Plunge Processing lnmold Processing

M g- Post- Mg- Post- lnmold Post- Alloy lnoculation Alloy Inoculation Alloy Inoculation

O# Alloy 1.4%

3# Alloy 1.4%

3 2.2% 0.45% Si in Ladle

2.2% 0.75% Si in Ladle

1 Germalloy 2.2% in

Downsprue

6 lnotabs 2.2% in

Downsprue



1 Germalloy 2.6% in

Downsprue

6 lnotabs 2.6% in

Downsprue

TABLE 3: CASTING PROCEDURE ON HEAT B - 400 POUND CHARGE

Plunge Process lnmold Processing Pouring

Ladle Casting Temp. Mg- Post- lnmold Post- C.E. N o. N o. OF Alloy Inoculation Alloy Inoculation Remarks

Low 1 201 2640 3# 1.4% C.E. 202 2630 3# 1.4% 0.1 O/O Si in 4.08 Runner

(Average) 2 203 2600 3# 1.4O/0 No-bake Sand

0.75%Si in Ladle 3 204 2560 2.6% O.l0/0Si in Runner No-bake Sand

205 2540 0.75%Si in Ladle

High 4 206 2600 O# 1.4% C.E. 207 2590 3# 1.4% 4.60

(Average) 5 208 2550 2.6% 0.75%Si in Ladle

209 2550 0.25% VP 216 in Ladle and

1 Germalloy in Downsprue

TABLE 4: CASTING PROCEDURE ON HEAT C (AVERAGE C.E. =4.4) - 650 POUND CHARGE

Pouring Plunge Processing lnmold Processing

Ladle Casting Temp. Mg- Post- lnmold Post- N o. N o. OF Alloy Inoculation Alloy Inoculation Remarks

1 30 1 2600 3# 1.9% 302 2600 3# 1.3%

0.45%Si in Ladle 0.6%Si in Ladle

0.75%Si in Ladle 0.25% VP 216 in Ladle and 1 Germalloy in Downsprue




For Low Sulfur Content

As above As above

For High Sulfur Content

As above As above

TABLE 5A: CHEMICAL ANALYSIS OF HEAT A

Ladle No. 1 2 3 4 5 6 7 8 9 10

Ladle N 0.

1 1A 2 3 3A 4 4A 5 5A

Base lron Tests from Furnace O/O C O/O S i O/O M n O/O S O/O P 3.43 .916 .411 .017 .026 3.34 1.03 .439 .017 .025 3.38 .968 .430 .020 .027

TABLE 58: CHEMICAL ANALYSIS OF HEAT B

Base lron Tests from Furnace O/O C %Si O/O M n O/O S O/O P 3.22 .63 .52 .012 .023 3.22 .67 .53 .012 .022

Ladle N 0.

1 1A 2 3 3A 4 4A 5 5A 6 7 7A 8 9 9A

TABLE 5C: CHEMICAL ANALYSIS OF HEAT C

Base Iron Tests from Furnace O/O C %Si O/O M n O/O S O/O P 3.61 -64 .50 .014 .022 3.58 .65 .51 .015 .025 3.54 .63 .52 .007 .024 3.56 .65 .53 .038 .025

TABLE 6A: MICROSTRUCTURE EXAMINATION FROM TEST CASTINGS OF HEAT A

-

GRAPHITE MATRIX

Pouring No. of Nodule Treatment No. of Temp. Specimen Nodu- Count Ferrite Pearlite Ledeburite Procedure Casting OF C.E. (Thickness) Type Size larity % Nod.lmm2 % % +Carbide%

lnmold 101 2680 4.26 101-1 1,Il 2,3 85-90 196 90 10 0 O# Alloy (2")

1.4% 101-2 1,11 3 85-90 188 90 10 0 (1 '12 ") 101-3 I 2,s >90 240 85 15 0 (1")

101-4 I 3 >90 280 85 15 0 ( l/2 ") 101-5 I 334 >90 376 70 30 0 ('/4 ") 101-6 I 495 >90 640 30 70 0

lnmold 102 2550 4.26 102-1 I 2,3 >90 220 90 10 0 O# Alloy (2")

1.4% 102-2 l,II 3 2 4 85 208 90 10 0 (1 % ") 103-3 I 4,3,2 >90 258 90 10 0 (1 "1

102-4 I 4 3 2 >90 350 90 10 0 (l/2 ") 102-5 I 5 >90 532 85 15 0 (l/4 ") 102-6 I 6 >90 632 10 75 15

lnmold 103 2450 4.26 103-1 I,II 3,4,2 90 264 90 10 0 O# Alloy (2")

1.4% 103-2 1,Il 2 3 1 85 158 75 25 0 (1 % ") 103-3 1,Il 3/42 85 208 75 25 0 (1 "1

103-4 I 3,4 >90 310 75 25 0 ('/2 ") 103-5 I 5 >90 504 70 25 5 (lh") 103-6 I 6 >90 624 10 50 40 (78")

lnmold 104 2650 4.28 104-1 I 2,3 >90 164 90 10 0 3# Alloy (2")

1.4% 104-2 1,11 1 2 >90 110 75 25 0 (1 '12 ") 104-3 I 2,3 >90 168 70 30 0 (1")

104-4 I 334 >90 258 60 40 0 ( '/z ") 104-5 I 394 >90 312 50 50 0 ( '/4 ") 104-6 I 5,6 >90 614 30 70 0

('18'')

lnmold 105 2560 4.28 105-1 I 2 >90 208 75 25 0 3# Alloy (2")

1.446 105-2 1,Il 2,4 85 190 60 40 0 (1 l/2 ") 105-3 1,Il 4 2 85 240 50 50 0 (1 ")

105-4 I 4 5 2 >90 272 45 55 0 (l/2 ") 105-5 I 3 >90 488 30 70 0 ('h ") 105-6 I 4 >90 650 10 85 5 (l18")

Pouring No. of Nodule Treatment No. of Temo. Soecimen Nodu- Count Ferrite Pearlite Led

I

lnmold 106 2450 4.28 106-1 I 2,1 >90 188 75 25 3# Alloy (2")

1.4% 106-2 I >90 172 60 40 0 (1 l/2 ") 106-3 I 3,2,1 >90 216 50 50 0 (1 ")

106-4 I 3 >90 301 45 55 0 ( % ") 106-5 I 4 >90 394 30 70 0

Sandwich 107 2600 4.25 2.2% Alloy

Ladle Inocula-

tion 0.45% Si

Sandwich 108 2500 4.25 2.2% Alloy

Ladle Inocula.

tion

Sandwich 109 2400 4.25 109-1 I 2 >90 100 70 30 0 2.2% Alloy (2")

109-2 I 1.2 >90 71 50 50 0

Ladle Inocula-

tion 0.45% Si

Sandwich 110 2600 4.18 110-1 I >90 80 85 15 0

Ladle Inocula-

TABLE 6A: MICROSTRUCTURE EXAMINATION FROM TEST CASTll

Pouring No. of Treatment No. of T e m ~ . S~ec imen

Nodule Nodu- Count Ferrite Pearlite Ledeburite I

Sandwich 111 2500 4.18 111-1 I 2 >90 92 85 15 0 2.2% Alloy (2")

11 1-2 I 2,1 >90 82 65 35 0 (1 '12 ") 11 1-3 I 2 >90 106 60 40 0

Ladle (1") Inocula- 111-4 I 2 >90 136 60 40 0

tion ( I12 ") 0.75% Si 111-5 I 4 >90 330 55 45 0

Sandwich 112 2400 4.18 112-1 I >90 64 70 30 0 I

Ladle Inocula-

Sandwich 113 2600 4.23 113-1 I 3 2 >90 177 95 5 0 2.2% Alloy (2")

113-2 I 3 2 >90 138 80 20 0 Postinocu- (1 % ")

lation 113-3 I 3 2 >90 148 80 20 0 1 Germalloy (1 "1

K20 in 1 13-4 I 3 >90 226 80 20 0 Downsprue (I12 ")

113-5 I 4 >90 380 70 30 0

Sandwich 114 2475 4.23 114-1 I 2 >90 162 95 5 0

Postinocu- lation

1 Germalloy K2O in

Sandwich 115 2400 4.23 115-1 I 2 >90 136 90 10 0

Postinocu- lation

1 Germalloy K20 in

TABLE 6A: MICROSTRUCTURE EXAM!NATION FROM TEST CASTINGS OF HEAT A (Continued)

GRAPHITE MATRIX Pouring No. of Nodule

Treatment No. of Temp. Specimen Nodu- Count Ferrite Pearlite Ledeburite Procedure Casting OF C.E. (Thickness) Type Size larity % Nod.lmm2 % % +Carbide% Sandwich 116 2600 4.16 116-1 I 1 2 >90 104 75 25 0

2.2% Alloy (2") 116-2 I 1 2 >90 90 65 35 0

Postinocu- (1 '/z ") lation 116-3 I 1 2 >90 82 55 45 0

Six lnotabs (1 ") in 116-4 I 2,3 >90 173 60 40 0

Downsprue ('/2 ") 116-5 I 4 >90 396 50 50 0 ('h ") 1 16-6 I 6 >90 432 10 80 10 (%"I

Sandwich 117 2500 4.16 117-1 I 2 >90 85 70 30 0 2.2% Alloy (2")

117-2 1,ll 1 2 90 59 45 55 0 Postinocu- (1 '/z ")

lation 1 17-3 I 2,3,1 >90 85 45 55 0 Six lnotabs (1 ")

in 1 17-4 I 3 >90 250 70 30 0 Downsprue (% ' I )

117-5 I 5 >90 332 40 60 0 ('h ") 1 17-6 I 6 >90 580 5 65 30

1 " 8

Sandwich 118 2400 4.16 118-1 I 1,2 >90 80 60 40 0 . 2.2% Alloy (2")

118-2 1,Il 1 2 90 57 45 55 0 (1 %")

Postinocu- 118-3 I 2 >90 101 45 55 0 lation (1 ")

Six lnotabs 118-4 I 3 >90 168 70 30 0 in (% ")

Downsprue 118-5 I 5 >90 388 40 59 1 ('h ") 118-6 I 5 >90 424 5 90 5 (%")

Sandwich 119 2550 4.16 119-1 I 2 >90 82 60 40 0 2.6% Alloy (2")

1 19-2 I 271 >90 68 45 55 0 (1 % ") 119-3 I 3 >90 85 30 70 0

Ladle (1") Inocula- 119-4 I 3 >90 162 30 70 0

tion (% ' I )

0.45% Si 1 19-5 I 5 >90 468 20 78 2 ('h ") 1 19-6 I 6 >90 572 5 65 30 (%")

Plunge 120 2500 4.16 120-1 I 2,1 >90 75 45 55 0 2.6% Alloy

! (2") 120-2 I 2,1 >90 58 40 60 0 (1 '/2 ") 120-3 I 3 2 >90 102 30 70 0

Ladle (1 ") Inocula- 120-4 I 3 >90 253 40 60 0

tion ( % ' I )

0.45% Si 120-5 I 4 >90 267 75 25 0 (%I1)

120-6 I 5.6 >90 412 30 68 2 (%"I

TABLE 6A: MICROSTRUCTURE EXAMINATION FROM TEST CASTINGS OF HEAT A (Continued)

GRAPHITE MATRIX


Plunge 121 2400 4.16 121-1 I 1 2 >90 65 45 55 0 2.6% Alloy (2")

121-2 I 1 2 >90 48 40 60 0 (1 % ") 121-3 I 2 >90 65 35 65 0

Ladle (1 ") Inocula- 121-4 I 3 >90 151 30 70 0

tion ('/z ") 0.45% Si 121-5 I 4 >90 380 30 70 0

( l/4 ") 121-6 I 5 >90 586 5 85 10 ('h")

Plunge 122 2575 4.18 122-1 I 1 2 >90 67 40 60 0 2.6% Alloy (2")

122-2 I 132 >90 64 40 60 0 (1 % ") 122-3 I 291 >90 123 30 70 0

Ladle (1") Inocula- 122-4 I 2 >90 152 30 70 0 0.75% Si ('12 ")

122-5 I 3,4 >90 272 60 40 0 ('/4 ") 122-6 I 5 >90 428 10 90 0

Plunge 123 2510 4.18 123-1 I 1 2 >90 126 45 55 0 2.6% Alloy (2")

123-2 I 1 2 >90 118 40 60 0 (1 '/2 ") 123-3 I 1 2 >90 160 30 70 0

Ladle (1 ") Inocula- 123-4 I 3 >90 292 30 70 0

tion ('/2 ") 0.75% Si 123-5 I 4 >90 348 40 60 0

( lh ") 123-6 I 5,6 >90 432 5 80 15 (%")

Plunge 124 2400 4.18 124-1 1,11 1 2 90 85 50 50 0 2.6% Alloy

Ladle Inocula-

tion 0.75% Si

('18'')

Plunge 125 2600 4.15 125-1 I 2,3 >90 196 90 10 0 2.6% Alloy

Postinocu- lation

1 Germalloy K20 in

Downsprue

TABLE 6A: MICROSTRUCTURE EXAMINATION FROM TEST CASTING OF HEAT A (Continued)

GRAPHITE MATRIX


Plunge 126 2500 4.15 126-1 I 3 2 >90 166 90 10 0 2.6% Alloy (2")

126-2 1,Il 2 85 122 60 40 0 (1 % ")

Postinocu- 126-3 I 2,3 >90 192 60 40 0 lation (1 ")

1 Germalloy 126-4 I 3 >90 296 45 55 0 K20 in (% ")

Downsprue 126-5 I 5 >90 570 30 70 0 ( '/4 ") 126-6 I 6 >90 644 5 50 45

Plunge 127 2400 4.15 127-1 I 2,3 >90 152 90 10 0 2.6% Alloy (2")

127-2 I 2,3 >90 120 70 30 0 (1 % ")

Postinocu- 127-3 I 3 2 >90 228 60 40 0 lation (1 "1

1 Germalloy 127-4 I 3,4 >90 340 60 40 0 K20 in ('/2 ")

Downsprue 127-5 I 5 >90 576 30 70 0 ('/I ") 127-6 I 6 >90 720 5 55 40 (Y8")

Plunge 128 2600 4.18 128-1 /,I1 1 2 85-90 66 40 60 0 2.6% Alloy (2")

128-2 I,II 1 90 4 1 40 60 0 (1 % ")


Six lnotabs 128-4 I 3 >90 240 30 70 0 in (% ' I )

Downsprue 128-5 I 4 >90 500 10 75 15 ( l/4 ' I )

128-6 I 5 >90 600 5 50 45 (1/8")

Plunge 129 2590 4.18 129-1 1,ll 1 2 85-90 112 60 40 0 2.6% Alloy (2")

129-2 1,11 1 85-90 88 45 55 0 (1 l/2 ")

Postinocu- 129-3 I 2,3 >90 128 30 70 0 lation (1 ")

Six lnotabs 129-4 I 2 >90 268 30 70 0 in (% ")

Downsprue 129-5 I 3,4 >90 448 20 77 3 ('/4 ") 129-6 I 5 >90 600 3 52 45 (%"I

Plunge 130 2400 4.18 130-1 I,II 1 2 90 72 40 60 0 2.6% Alloy (2")

130-2 1,Il 1 2 90 69 40 60 0 (1 % ")


Six lnotabs 130-4 I 2,3 >90 224 40 55 5 in ( % ")

Downsprue 130-5 I 3,4 >90 252 10 70 20 ('h") 130-6 I 4 >90 332 0 70 30 (Ye")

TABLE 6B: MICROSTRUCTURE EXAMINATION FROM TEST CASTINGS OF HEAT B

- GRAPHITE MATRIX Pouring No. of

Treatment No. of Temp. Specimen Procedure Casting OF C.E. (Thickness)

lnmold 20 1 2640 4.09 201-1 3# Alloy (2") 1.4% 201-2

(1 '12 ") 201 -3 (1") 201-4 ('12 ' I )

201-5 (%") 201-6

Nodule Nodu- Count

TY pe Size larity % Nod.lmm2 1,ll 2,3,4 85 128

Ferrite Yo

70

Pearlite Ledeburite % +Carbide%

30 0

lnmold 202 2630 4.10 202-1 I 2,3,4 >90 216 90 10 0 3# Alloy (2") 1.4% 202-2 I 2,1,3

(1 '12 ") 203-3 I 2,3,4

Runner (1 "1 Inoculation 202-4 I 3,4 0.1% Si ('12 ") (75 Fe-Si) 202-5 I 4,5

( '/4 ") 202-6 I 6 5 a")

lnmold 203 2600 4.1 1 203-1 I 2,1,3 3# Alloy (2") 1.4% 203-2 1,Il 2,1,3

(1 % ") 203-3 I 2

No-Bake (1 ") Sand 203-4 I 2,3

( '/2 ") 203-5 I 3 ('A ") 203-6 I 4

Plunge 204 2560 4.04 2.6% Alloy

Ladle lnoculation 0.75% Si (75 Fe-Si) + Runner

lnoculation 0.1% Si (75 Fe-Si) No-Bake

Sand ('18")

Plunge 205 2540 4.08 205-1 I 2 >90 76 45 55 0 2.6% Alloy (2")

205-2 I &I >90 60 30 70 0 (1 '/2 ") 205-3 I 271 >90 72 20 80 0 (1 "1 205-4 I 3 >90 152 20 80 0 ('12 ") 205-5 I 4 >90 276 15 80 5 ('h ")

Ladle lnoculation 0.75% Si

TABLE 6B: MICROSTRUCTURE EXAMINATION FROM TEST CASTINGS OF HEAT B (Continued)

GRAPHITE MATRIX


lnmold 206 2600 4.68 206-1 1,11 2,3,4 85 180 90 10 0 O# Alloy (2")

1.4% 206-2 I 2,3 >90 168 70 30 0 (1 '12 ") 206-3 I 2,4,5 >90 220 60 40 0 (1 ")

206-4 I 394 >90 316 60 40 0 ('12 ") 206-5 I 4 >90 384 50 50 0 ( '14 ' I )

206-6 I 5 >90 600 15 85 0 (78")

lnmold 207 2590 4.65 207-1 I 3 2 >90 244 90 10 0 3# Alloy (2")

1.4% 207-2 I 2 >90 216 70 30 0 (1 $12 ") 207-3 I 3 >90 256 60 40 0 (1 ")

207-4 I 3,2 >90 376 60 40 0 ('/2 ") 207-5 I 4,3 >90 400 50 50 0 (% ") 207-6 I 5,4 >90 620 15 85 0

Plunge 208 2550 4.63 208-1 I 2,1 >90 104 45 55 0 2.6% Alloy (2")

208-2 I 1 2 >90 68 45 55 0 (1%")

Ladle 208-3 I,II 2 3 90 116 40 60 0 Inoculation (1 "1 0.75% Si 208-4 I 3 2 >90 160 40 60 0 (75 Fe-Si) ( % ")

208-5 I 3,4 >90 316 35 65 0 ('A ") 208-6 I 5 >90 704 10 90 0

Plunge 209 2.6% Alloy

Ladle Inoculation VP216-025% Downsprue Inoculation 1 Germalloy

K20

TABLE 6C: MICROSTRUCTURE EXAMINATION FROM TEST CASTINGS OF HEAT C

GRAPHITE MATRIX

Pouring No. of Nodule Treatment No. of Temp. Specimen Nodu- Count Ferrite Pearlite Ledeburite Procedure Casting OF C.E. (Thickness) Type Size larity % Nod.lmmz % % +Carbide%

lnmold 301 2600 4.38 301-1 I,lI 3 2 90 220 80 20 0 3# Alloy (2") 1.9% 301-2 I 2 >90 156 70 30 0

(1 I12 ") Mgr= 301-3 I 3 2 >90 248 60 40 0 0.06S0/o (1 ")

301-4 I 334 >90 256 60 40 0 (% ") 301-5 1,11 3,4 90 284 30 70 0 ( '/4 ") 301 -6 I 5 >90 680 15 75 10 (%")

lnmold 302 2600 4.37 302-1 I,II 2,3 85 148 85 15 0 3# Alloy (2") 1.3% 302-2 1,11 3 85 140 85 15 0

(1 % ") Mgr= 302-3 1,Il 2,3 80 180 70 30 0 0.04% (1 ")

302-4 l,11 3 80 208 60 40 0 ( % ") 302-5 I,II 473 85 248 60 40 0 ( '/4 ") 302-6 I 5 >90 564 15 82 3

lnmold 303 2600 4.38 303-1 I ( + I ) 3,2 55 144 75 25 0 3# Alloy (2") 0.8% 303-2 I ( + I ) 3,l 50 112 60 40 0

Mgr= (1%") 0.030% 303-3 l , l l ,(+ll l) 2,3 50 160 50 50 0

(1") 303-4 1,11 3 2 85 180 60 40 0 ( '/z ") 303-5 1,11 394 85 220 50 50 0 ( '/4 ") 303-6 I 4,3 >90 496 30 70 0

Plunge 304 2490 4.39 3.8% Alloy

Mgr = 0.059%

Ladle Inocula-

tion 0.45%

(75 Fe-Si)

(79'')

Plunge 305 2470 4.46 305-1 I 2,3 >90 160 90 10 0 3.8% Alloy (2")

305-2 I 3 2 >90 148 90 10 0 Mgr= (ll/z") 0.067% 305-3 I 3 2 >90 196 80 20 0

Ladle (1") Inocula- 305-4 I 3 >90 248 65 35 0

tion ( % ") 0.6% Si 305-5 I 4 >90 496 60 40 0 (75 Fe-Si) ('h ")

305-6 I 5,6 >90 784 15 85 0 (%"I

TABLE 6C: MICROSTRUCTURE EXAMINATION FROM TEST CASTINGS OF HEAT C (Continued)

GRAPHITE MATRIX

Pouring No. of Nodule Treatment No. of Temp. Specimen Nodu- Count Ferrite Pearlite Ledeburite Procedure Casting F C.E. (Thickness) Type Size larity % Nod.lmm2 % % +Carbide%

Plunge 306 2540 4.39 306-1 I 2 >90 96 75 25 0 1.70% Alloy (2")

306-2 I 2 >90 80 75 25 0 (1 l/2 ")

Ladle Mgr= 306-3 I 2 >90 112 60 40 0 Inocula- 0.036% (1")

tion 306-4 I 3 >90 196 60 40 0 0.75% Si ( ?I2 ") (75 Fe-Si) 306-5 I 4 >90 352 60 40 5

( '/4 ") 306-6 I 6 >90 747 75 25 0 ( X " )

Plunge 307 2530 4.37 307-1 I 4,3,2 >90 412 95 5 0 1.7% Alloy (2")

Mgr= 307-2 I 2,s >90 21 2 90 10 0 Ladle 0.034% (1 % ")

Inoculation 307-3 I 2 3 >90 268 60 40 0 VP216-0.25% (1 ")

307-4 I 2 >90 296 70 30 0 Downsprue (?/z ") Inoculation 307-5 I 4 >90 548 75 25 0 1 Germalloy (I/.")

K20 307-6 I 6 >90 1172 70 30 0

(%") Plunge 308 2540 4.41 308-1 I 1 2 >90 64 75 25 0

2.6% Alloy (2") 308-2 I 1 2 >90 52 75 25 0 (1 l/2 ")

Ladle 308-3 I 2,1 >90 80 75 25 0 Inoculation (1 ") 0.25% Si 308-4 I 3 2 >90 100 60 40 0 (75 Fe-Si) (% ")

308-5 I 3,4 >90 240 85 15 0 (lh ") 308-6 I 5 >90 604 75 25 0 (lh")

Plunge 309 2530 4.49 309-1 I 3 2 >90 164 95 5 0 2.6% Alloy (2")

Ladle lnoculation

0.6% Si (75 Fe-Si)

(%"I lnmold 310 2600 4.37 310-1 I 2 >90 120 60 40 0

#3 Alloy (2")

TABLE 6C: MICROSTRUCTURE EXAMINATION FROM TEST CASTINGS OF HEAT C (Continued)

GRAPHITE MATRIX


Plunge 311 2480 4.42 311-1 I 2,s >90 88 75 25 0 2.4% Alloy (2")

311-2 I 2 >90 72 75 25 0 Ladle S = (1 % ")

Inoculation 0.007% 311-3 I 3 2 >90 104 75 25 0 0.45% Si (1 "1 (75 Fe-Si) 31 1-4 I 3 >90 160 60 40 0

(% ") 31 1-5 I 4,5 >90 300 80 20 0 (% ") 311-6 I 5 >90 588 30 55 15

- (1/8") Plunge 312 2470 4.43 312-1 I 3 2 >90 188 98 2 0

2.4% Alloy (2") 31 2-2 I 2,3 >90 132 95 5 0 (1 -12 ")

Ladle S = 3 12-3 I 3,4 >90 236 95 5 0 Inoculation 0.007% (1") 0.75% Si 31 2-4 I 3,4 >90 260 90 10 0 (75 Fe-Si) (% ")

312-5 I 5 >90 632 90 10 0 ('h ") 312-6 I 6 >90 908 75 25 0

lnmold 313 2600 4.30 313-1 I 2 >90 220 75 25 0 3# Alloy (2")

1.6% 31 3-2 I 291 >90 188 70 30 0 S = (1 '12 ")

0.037% 313-3 I 2,3 >90 236 60 40 0 (1")

313-4 I 3 2 >90 312 50 50 0 (% ") 313-5 I 473 >90 384 60 40 0 ('/4 ") 313-6 I 5 >90 776 60 40 0

Plunge 314 2470 4.40 314-1 I 2 >90 124 75 25 0 2.8% Alloy (2")

314-2 I 2,1 >90 104 50 50 0 (1 l/2 ")

Ladle S = 314-3 I 3 >90 160 70 30 0 Inoculation 0.038% (1") 0.45% Si 314-4 I 3 >90 196 60 40 0 (75 Fe-Si) ( % ")

31 4-5 I 4 >90 488 55 45 0 ( '/4 ") 314-6 I 5 >90 772 10 75 15

('18")

Plunge 315 2450 4.46 315-1 I 2 >90 160 95 5 0 2.8% Alloy (2")

31 5-2 I 231 >90 132 95 5 0 (1 l/2 ")

Ladle S = 31 5-3 I 2 3 >90 212 90 10 0 Inoculation 0.036% (1") 0.75% Si 31 5-4 I 3 >90 272 90 10 0 (75 Fe-Si) ('12 ")

315-5 I 5 >90 460 75 25 0 ('/4 ") 31 5-6 I 5 6 >90 1096 0 25 75 (%")

TABLE 7: EFFECT OF POURING TEMPERATURE ON NODULE COUNT

Pouring Average Nodule Count, Average Nodule Count at Same Pouring Temperature, OF No. of Casting Noduleslmm2 Temp., Noduleslmm2 (1 l/2, 1, l/z, lh")

2400 103 295 159-31 6 (or 2450) 106 271

109 159 2170 - 10 = 217 112 173 115 274 118 179 121 161 124 182 127 31 6 130 160

2500 -

102 337 153-337 (or 2475-2550) 105 298

108 153 2309 - 10 = 231 11 1 164 114 247 117 182 120 170 123 230 126 295 129 233

2600 101 271 148-271 (or 2550-2680) 104 212

107 148 2040 - 10 = 204 110 192 113 223 116 185 119 196 122 153 125 246

128 214

r \ CHEMICAL ANALYSIS SAMPLE

THREE INGATES

FlGURE1: DIMENSIONS OF STEP-PLATE CASTING.

OUTLET

FIGURE 2:

REACTION CHAMBER

.- , REACTION CHAM

0.9" 2.3" 2.3" 1"

3x0.3in2 = 0.9in2 l.0in2 1 .O1 in2 1 .2in2 1 .2in2

2.3 x 2.3"

J ' DOWNSPRUE

GATING SYSTEM DESIGN FOR INMOLD TREATMENT.

OUTLET 1.12A

INGATES (A)

l N LET 1.3A

RUNNER 1 . l A

TAPERED DOWNSPRUE

13A

K20 GERMALLOY Av. wt = 239

A. ONE GERMALLOY DOWNSPRUE INOCULATION

C. FERRO-SILICON RUNNER INOCULATION

4- 0.5' -1

FOSECO INOTAB wt. = 49

B. SIX INOTABS DOWNSPRUE INOCULATION

FIGURE 3: GATING SYSTEM DESIGN FOR SPRUE AND RUNNER POSTINOCULATION.

*

0 ) El, m J .

Microstructure face

FIGURE 4: LOCATION OF METALLOGRAPHIC TESTS IN STEP BLOCK.

(a) Graphite Size 1 100 pm average diameter

(c) Graphite Size 3 35pm average diameter

(b) Graphite Size 2 55pm average diameter

(d) Graphite Size 4 25 pm average diameter

(e) Graphite Size 5 18 pm average diameter

(f) Graphite Size 6 10 pm average diameter

FIGURE 5: PHOTOMICROCRAPHS SHOWING SIX SELECTED LEVELS OF GRAPHITE SIZE, UNETCHED 100 x. (14)

(a) >90% Nodularity (b) 85% Nodularity

(c) 75% Nodularity (d) 55% Nodularity

FIGURE 6: PHOTOMICROGRAPHS SHOWING FOUR SELECTED LEVELS OF NODULARITY, UNETCHED 100X. (14)

LADLE INOCULATION loor O i - F O U N D R Y G R i i D E F e S i

0 SANDWICll 2 5 0 0 ~ 1 : ( 1 0 8 )

600 t A PLUNGE 25000F ( 1 2 0 )

A THICKNESS OF SECTIONS, IKCHES B THICKNESS OF SECTIONS, INCHES

700- LADLE INOCULATION

FIGURE 7: NODULE COUNT IN DIFFERENT SECTION THICKNESS WlTH A, 0.45O/oSi AND B, 0.75%Si AS LADLE POSTINOCULANT

0 . 7 5 % S i - FOUNDRY GRADE F e S i

0 SANDWIClI 25000F (111) 4 PLUNGE 2510oF ( 1 2 3 ) 6 0 0 -

5 0 0 -

1 / 8 b % 1 1 ?j 2

A THICKNESS OF SECTION, INCHES

PROCESS

(

7 0 0 r

600

500

h N

g 4 0 0 - VI Q, rl 1 5

3 0 0 - V

+ Z 3 0

2 0 0 - W el 3 n 0 z

1 0 0

DOWNSPRUE INOCULATION INOTAB

0 SANDWICH 2 5 0 0 ' ~ (117)

1 b A PLUNGE 2 5 0 0 ~ ~ ( 129 ) 600

DOWNSPRUE INOCULATION GERMALLOY

A 0 SANDWICH 2 4 7 5 ' ~ ( 1 1 4 )

1 / 8 L 1 1% 2

B THICKNESS OF SECTIONS, INCHES

-

-

FIGURE 8: NODULE COUNT IN DIFFERENT SECTION THICKNESS WlTH A, GERMALLOY AND B, INOTAB l NOTAB SPRUE POSTINOCULATION.

A PLUNGE 2 5 0 0 ' ~ ( 1 2 6 )

A

PLUNGE PROCESS

SANDWICH PROCESS

A -

AVERAGE NODULE COUNT (noduleslmm2) 1 l/2,1,l/2 ,l/4 (INCH)

I I I

N IN MOLD (0# ALLOY OR 3# ALLOY) 00 2

N PLUNGE OR SANDWICH + GERMALLOY INOCULATION 2

PLUNGE OR SANDWICH 2

+ INOTAB INOCULATION CO IU

PLUNGE + 0.75% Si AS 75% FeSi 2

00 LADLE INOCULATION 00

2 PLUNGE+O.45%SiAS75%FeSi LADLE INOCULATION CT,

SANDWICH + 0.75% Si AS 75% FeSi LADLE INOCULATION CT,

1

2 SANDWICH + 0.45% Si AS 75% U.I FeSi LADLE INOCULATION o -

INMOLD 38 ALLOY 1.4% 0 NO-BAKE SAND 2600'~ (203) C.E. 4.11 A GREEN SAND 2640'~ (201) C.E. 4.09

01 1 I I I I I

1/8 t 4 1 14 2

THICKNESS OF SECTIONS, INCHES

FIGURE 10: INFLUENCE OF TYPE OF MOLD ON NODULE COUNT (HEAT B).

PLUNGE PROCESSING (312)n LADLE INOCULATION 0.75%Si 2470'~ (309)O LADLE INOCULATION 0.60%Si 2530'~ (30418 LADLE INOCULATION 0.450Si 2490'~

LADLE INOCULATION

FIGURE 11: EFFECT OF AMOUNT OF LADLE POSTINOCULANT AS 75% FeSi ON NODULE COUNT.

0

PLUNGE TREATMENT

0 C.E.=4.63 2550°F (208)

A C.E.=4.08 2540'~ (205)

1 1 I 1 I I

C.E. 4.63

C.E. 4.08

1 8 k 4 1 1% 2 THICKNESS OF SECTIONS, INCHES


INhICLD 1.4% ALLOY

0 OX ALLOY 26000F (206) C.E. 4.68

A 3U ALLOY 2590°F (207) C.E. 4.65

OU ALLOY


FIGURE 12: EFFECT OF CARBON EQUIVALENT ON FIGURE 13: INFLUENCE OF La:Ce RATIO IN INMOLD NODULE COUNT OF CASTINGS WITH MAGNESIUM ALLOY ON NODULE PLUNGING MAGNESIUM TREATMENT COUNT. AND 0.75% Si LADLE POSTINOCULATION.

1NMOI.D 31 ALLOY

0 S-0.037: ( 3 1 3 ) 1 . 6 % Al.l.OY C.E. 4 . 5 0

A S = 0 . 0 1 4 % ( 3 0 2 ) 1.3: ALLOY C.F. 4 . 3 7

s = o . o n 7 r ( 3 1 n ) 1 . 2 s ALLOY C . E . 4 . 3 7

I I 1

1 k 'r 1 1'2 2

A TllICKNESS OF SI CTIONS, INCllES

PI.UN(;E I.AD1.E INOCULATION 0 . 4 5 % S i

A s = n . n 3 s p ( 3 1 4 ) 2 . 8 % ALLOY C . E . 4 . 4 0

s = n . n 1 4 ; ( 3 n 4 ) 3 . 8 % ALLOY C . E . 4 . 3 9

0 S = 0 . 0 0 7 % ( 3 1 1 ) 2.4: ALLOY C.E. 4 .42

BASE SUI.FUR 0 . 0 3 8 %

RASE SULFUR

1 I I 1 / 8 : ', 1 1 4 2

1% THITKNCSS OF SCCTIONS, INCIICS

FIGURE 14: EFFECT OF BASE SULFUR CONTENT ON NODULE COUNT FOR VARIOUS SECTION THICKNESS WlTH A, INMOLD AND B, PLUNGE MAGNESIUM TREATMENT.

INMOLI) n3 ALLOY

0 blgRe=0.0b5% (301) C.E. 4 . 3 8

A MgRc=0.04 % ( 3 0 2 ) C.E. 4 . 3 7

0 Mgk,=0.03 % ( 3 0 3 ) C.E. 4 . 3 8

0-L 1 / 8 !4 'i 1 1 ', 2

A 'I'IIICKNESS OF SECTIONS. IN(:III S

1'I.IINC.L

0 blgRc=0.067% ( 3 0 5 ) C.E. 4 . 4 6 . 6 % S i o r 7 5 t F c S i P . I .

F l g ~ ~ = 0 . 0 5 9 % ( 3 0 4 ) C.E. 4 .39 . 4 5 % S i o r 758l:eSi P . I .

AblgRe=0.036% ( 3 0 6 ) C.E. 4 . 3 9 . 7 5 % S i o r 7 5 % F c S i P . I .

FIGURE 15: EFFECT OF RESIDUAL MAGNESIUM CONTENT ON THE NODULE COUNT IN VARIOUS SECTION THlCKN ESSES WlTH A, INMOLD AND B, PLUNGE MAGNESIUM TREATMENTS.

the influence of foundry variables on nodule count … · higher recovery with the plunge...

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