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D oc:MTD 4 ( 5053 )For Comments On ly

Draft Standard

COATED STEEL SHEETS FOR AUTOMOTI VE APPLI CATI ONS

I CS 77.14 0.50

No t t o be rep roduced w i t hou t t he pe rm i ssi on o f Last da t e f o r r ece ip t o f

BI S or used as STANDARD comm ents i s 20 Feb. 2011

FOREWORD(Formal clauses will be added later)

In response to the greater stringent and varied requirements for steel sheets and strip forautomobiles, a large number of specifications have been made in this field. For theconvenience of all interested parties, activities to summarize these specifications and todevelop unified standards were carried out by the BIS. An attempt has been to cover all therequirements of Automobile industry under a single standard.

For the purpose of deciding whether a particular requirement of this standard is complied with

the final value, observed or calculated, expressing the result of a test or analysis shall berounded off in accordance with IS 2:1960. The number of significant places retained in therounded off value should be the same as that of the specified value in this standard.

1. SCOPE

This draft standard covers the requirements of zinc or Zn-alloy coated sheets and coils,produced by hot dip galvanizing, galvannealing or electrolytic process. These sheets areintended for use in automotive application requiring excellent corrosion resistance. Thesematerials / components shall be suitable for alkaline degreasing, welding, electro coating andfinish painting.

2. REFERENCES

The following Indian Standards contain provisions which through reference in this text,constitute provision of this standard. At the time of publication, the editions indicated werevalid. All standards are subject to revisions, and parties to agreements based on thesestandards are encouraged to investigate the possibility of applying the most recent editions ofthe standards indicated below:

I S No. Title

209 :1992 Zinc ingots Specification (fourth revision)513:2008 Cold reduced low carbon steel sheets and strips (fifth revision)1079 :2009 Hot rolled carbon steel sheets and strips- Specification (sixth revision)1956 (Part 4):1975 Glossary of terms relating to iron and steel Part 4 Steel sheet and

Strip2062: 2006 Hot rolled low medium and high tensile structural steel (sixth revision)2629 : 1985 Recommended practice for hot-dip galvanizing of iron and steel

(first revision)6745 : 1972 Method for determination of mass of zinc coating on zinc coated iron

and steel articles8910 : 2010/ General technical delivery requirements for steel and steel productsISO 404 (first revision)13229: 1991 Zinc for galvanizing


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3. TERMI NOLOGY

For the purpose of this standard, the definitions given in IS 1956 (Part 4), and the followingdefinition shall apply.

3.2 HR Sheet / Co i l Hot rolled sheets and coils prior to pickling operation.

3.3 Co ld Ro l led Sheet / Co i l Cold rolled sheets and coils prior to galvanizing process.

3.4 Th ickness o f Sheet / Co i l Thickness of hot rolled and cold rolled sheets in cut length orcoil form.

3.5 BH A steel grade that shows a controlled aging behaviour during the paint bakingtreatment, thereby increasing the dent resistance.

3.6 DP s tee l A steel grade with a microstructure of ferrite and martensite, created bysuitable heat treatment.

3.7 GA (galvannealing) A coating formed of zinc and iron alloy throughout the layer,consisting mainly of d1 phase with iron content varying from 8-14%

4. SUPPLY OF MATERI AL

The general requirements relating to the supply of galvanised sheets and strips shall conformto IS 8910.

5. MANUFACTURE

5 .1 Coating shall be carried out by first pickling the HR sheets or by alkaline and/orelectrolytic cleaning of the cold rolled coils and then dipping them in a bath of molten zinc at atemperature suitable to produce a complete and uniformly adherent zinc-based coating (seeIS 2629). The zinc and zinc alloy ingots used for the galvanising shall conform to any of thegrades specified in IS 209 (appendix) or IS 13229.

5 .2 The manufacturing process shall be agreed between the customer and the manufacturer.

6. CLASSI FI CATI ON OF GRADES

6 .1 The steel sheets and strip shall consist of eight types of hot rolled substrate and fifteentypes with cold rolled substrate. The designations shall be as given in Table 1 A for hot rolledsubstrate and table 1B for cold rolled substrate

Tab le 1A Hot Ro l led Sheets and Co i l s

Sl No. Type and Des ignat ion Speci f iedTh ickness

(1) (2) (3)

ZH C

ZH D

i) Mild steel

ZH E

ZH 310 C Mn

ZH 370 C Mn

ZH 400 C Mn

ii) C, Mn type steelsheet

ZH 440 C Mn

iii) Micro-alloyed Steelsheet

ZH 440 MA

1.0 6 mm


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Table 1B Cold Rol led Sheets and Coi ls

S l No. Type and Des ignat ion App l i cab le

Speci f ied

Th ickness

(1) (2) (3)

ZC C

ZC D

ZC E

0.4 to 3.2

ZC F

i) Mild Steel Sheet

ZC G

ZC 270BHii) Bake-hardeningsteel sheet ZC 340BH

0.4 to 2.3

ZC 340CMn

ZC 390 CMn

iii) Carbon Mn steelsheet

ZC 440 CMn

0.4 to 3.2

ZC 440

MA

0.4 to 2.3iv) Micro alloyed steel

sheetZC 590

MA0.6 to 2.0

ZC 340IFHS

ZC 390IFHS

v) IF high strengthsteel sheet

ZC 440IFHS

0.4 to 2.3

Any other grade apart from the grades mentioned above may be manufactured and suppliedunder the mutual agreement between manufacturer and customer.

7. TECHNI CAL REQUI REMENTS

7.1 Chem ica l Com pos i t ion s

The chemical composition shall be as per the agreement between the supplier and customer.On request, the report of one heat analysis shall be made available to the purchaser.

7.2 Mechan ica l Proper t ies

Requirements for the mechanical properties of steel sheets and strip shall apply to the valuesobtained from the tests carried out by the manufacturer after manufacturing.

7 . 2 .1 T ens i l e s t reng t h , y i e l d po i n t o r p r oo f s t ress, el onga t i on , mean p l as t i c s t ra i n

ra t i o , and amoun t o f bake -ha rden ing

Steel sheets and strip shall be tested for resultant tensile strength, yield point or proof stress,

elongation, mean plastic strain ratio (only in the case of cold rolled substrate), and amount ofbake-hardening(1) (only in the case of cold rolled substrate), shall conform to Table 2A, 2B or2C

7.2 .2 Order ing Cond i t ion : Zinc coated sheets of above designations are supplied under thefollowing two conditions of ordering:

a) Steel when ordered to mechanical properties shall, at the time the steel ismade available for shipment, satisfy the applicable requirements of Table 3.


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b) Additional requirements related to performance of a product may be mutuallyagreed upon between the supplier and the customer.

NOTE: Prolonged storage of the steel can cause a change in the mechanical properties likeincrease in hardness, decrease in elongation resulting to a decrease in drawability. To minimizeall these effects quality grades GPDD, GPEDD and GPIF should be specified.


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Tab le 2A Tens i le St r engt h , Y ie ld Po in t o r P roof S t ress and E longat ion( fo r H o t R o l l ed S ubst r a t e )

Yield point or proof stress N/mm2 Elongation %

Specified thickness e mm Specified thickness e mm

Type and designation Tensilestrengthmin,N/mm2

1.4e


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Tab le 2C Tens i le St rengt h , Yie ld Po in t o r Proo f St r ess , Am ount o f Bake

Harden in g and Mean Plast i c

St ra in Rat io ( Co ld Ro l led Subst r a te )

Yield Point or proof massN/mm2

Elongation % Mean plasticstrain ratio

min.Specified Thickness e mm Specified Thickness e mm Specified

thickness e mm

e and designation TensileStrength

min.N/mm2

0.4e


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Fig .1 Schem at ic Representa t ion o f The

De t e rm ina t i on o f Bake Ha rden ing Magn i t ude

7.2 .3 The tensile test shall be carried out in accordance with IS 1608 as applicable.

7.2 .4 Average plastic strain ratio (r-bar value) shall be determined as per IS 11999.

7.2 .5 Sur face Roughness- For aesthetic quality of sheet metal panels, and for specificapplications, the value of average roughness (Ra) shall be 0.80 to 1.20 or, as per theagreement between the customer and the manufacturer.

7.3 Coat ing

7.3 .1 Coating Mass- The steel sheets and strip shall include both those where the mass ofhot-dip coating is equal on both sides. There would be primarily 2 types of hot dip coatings,zero spangled Galvanized, hereafter referred as ZI and Galvannealed, hereafter referred as ZFDesignations of hot-dip coating mass and the minimum and maximum of coating mass on one

side shall be as given in Table 3A for galvannealed (ZF) and Table 3B for Galvanized (ZI)

7.3 .2 Mass and composition of upper coating layer - The mass and composition of the uppercoating layer shall be subject to the agreement between the supplier and the purchaser.

Tab le 3A Coat ing Mass ( gsm ) on Each S ide fo r Ga lvannea led ( ZF)( Average Mass by One Side T r ip le -Spot Test )

Average Mass by One Side

Tr ip le Spot Test

S l No. Hot -d ip Coat ing Mass

Des ignat ion

Min Max

(1) (2) (3) (4)

i) ZF 25 25 45

ii) ZF 30 30 50

iii) ZF 35 35 55


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iv) ZF 40 40 60

v) ZF 45 45 65

vi) ZF 50 50 70

vii) ZF 55 55 75

Tab le 3B Coa t i ng Mass (gsm ) on Each S ide fo r Zero Spang led Ga lvan ized ( Z I )( Average Mass by One Side T r ip le -Spot Test )

Average Mass by One Side

Tr ip le Spot Test

S l No. Hot -d ip Coat ing Mass

Des ignat ion

Min Max

(1) (2) (3) (4)

i) ZI 30 30 50

ii) ZI 50 50 70

iii) ZI 60 60 90

iv) ZI 70 70 100

v) ZI 90 90 120

vi) ZI 100 100 130

vii) ZI 140 140 170

7.3 .3 Coating Thickness -To estimate the thickness of coating from the coating weightfollowing factors (per side) shall be used,

a) Plain Zinc coating (Hot Dip/Electro galvanized/ Galvanealed) @ 7.16 gsm = 1 mb) Zinc/Iron (Electro galvanized) @ 7.25 gsm = 1 m

7.3 .4 Coating Composition -For Zn-Iron coating, bulk iron content of the coating shall be 7 to15 percent. Within the coating, iron shall be evenly dispersed and not contain planes or areaof widely varying concentration. Point to point Scanning Electron Micrograph energydispersion, X-ray analysis of coating cross section shall not show iron to vary by more than 5percent of the actual bulk iron content.

For hot dipped galvannealed bulk iron content of the coating shall be 7 to 15 percent.

7.3 .5 Coat in g Adhes ion Test o r Bend Test

7.3 .5 .1 Bend test shall be carried out on two samples for every 1 000 plain sheets.

7.3 .5 .2 One bend test shall be conducted for every coil.

7.3 .5 .3 For the bend test the test piece shall be 230 mm long and 75 to 100 mm wide and cutacross the direction of rolling.

7.3 .5 .4 Specimens for bend test shall be free from burrs. Filing and machining of the sheetsto remove the burrs is permitted. Cracks of the base metal developing at the edge of thespecimen or the coarse grain developing at the line of bend shall be disregarded.

7.3 .5 .5 Samples selected shall withstand bending through 180o around a mandrel having

diameter specified in Table 6 without peeling or flaking of the coating. Crack or fracture ofbase metal except those specified in 8.3.4.4 shall not be permitted.

7 . 4 We ldab i l i t y - The product shall be suitable for welding if appropriate welding methods andprocedures are used with special care for heavier coatings. The product shall be suitable forarc welding, CO2 welding or resistance welding.

7 . 5 Pa in t i ng - Hot dip zinc coated steel sheet is suitable for painting, but the first treatmentmay be different from that used for mild steel. Pre-treatment primers, chemical conversioncoatings or some special paints suitable for direct application on the coated surface, are all


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appropriate first treatment for hot dip zinc coated sheets. In deciding a painting schedule,consideration shall be given for whether the coated sheets have been ordered in passivated ornon-passivated condition.

7 . 6 Su r f ace Trea t m en t

7 .6 .1 Mill Passivation - A chemical treatment is normally applied to the zinc coating to

minimize the hazard of exposure leading to white rust or wet-storage stains during shipmentand storage. However the inhibiting characteristics of the treatment are limited and if ashipment is received wet, the material would have to be dried and/or used immediately afterevaluating the degree of degradation.

7.6 .2 Mill Phosphating-Zinc coated steel sheets may be processed chemically (phosphated) atthe manufacturers works to prepare the coated surface for painting without further treatment,except normal cleaning.

7.6 .3 O i l i ng

The zinc coated sheets as produced may be oiled to prevent damage to the soft surface duringhandling and shipping and to minimize the wet storage stains. After the zinc coated sheetsreceive a passivating treatment, oiling would further minimize the hazard of wet storage

stains.

7.7 Jo in ts in Coated Co i l s - Continuous coil coating lines use various methods to join the coilends. These methods include tag welding, butt welding or stitching operation. The shipment ofcoils containing the joined coil ends shall be permitted if agreed upon between themanufacturer and the customer.

7.8 D im ens iona l and To le rances o f P la in Sheets and Co i ls

7 . 8 .1 Rep resen t a t i on o f d im ens ions

Dimensions of steel sheets and strip shall be represented as follows:

a)

Dimensions of steel sheet shall be represented by the thickness, width andlength in millimeters.b) Dimensions of steel strip shall be represented by the thickness and width in

millimeters. When strip mass is specified by calculated mass, the length forcalculation shall be given in meters.

c) Specified thickness refers to the substrate thickness before coating.7.8 .3 To lerances

7.8 .3 .1 Length : Length tolerance of steel sheets shall be as follows:

a) Length tolerance shall apply to specified length.b) Length tolerances for steel sheets shall be Tolerance A and Tolerance B, as

given in Table 4 and Table 5 respectively.

Tab le 4 Stee l Sheets w i th Length To le rance ASl No. Spec i f ied Length l

( m m )To le r anc e ( m m)

(1) (2) (3)

i) 1 < 2000 + 10 / - 0

ii) 2000 1 < 3000 + 15 / - 0

iii) 3000 1 < 4000 + 15 / - 0

iv) 4000 1 < 6000 + 20 / - 0


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Tab le 5 Stee l Sheets w i th Length To le rance B

Sl

No

Speci f ied length l

( m m )

T o le rance (mm)

(1) (2) (3)

i) 1 < 2000 + 4 / - 0

ii) 2000 1 < 3000 + 6 / - 0

iii) 3000 1 < 4000 + 8 / - 0

iv) 4000 1 < 6000 + 10 / - 0

7.8 .3 .2 The diagonal distance between opposite corners of any sheet shall not differ by morethan 20 mm.

7 . 8 .3 . 3 W id t h : Width tolerance shall be as follows:

a) Width tolerance shall apply to specified width.b ) Width tolerances shall be Tolerance A and Tolerance B, as given in Table 6 and Table 7

respectively.

Tab le 6 Wid th To le rance A

Sl

No.

Spec i f ied Wid th b (mm) To lerance

(mm)

(1) (2) (3)

b < 600 0.5

600 b < 1250 + 70

i) Cold rolledsubstrate

B 1250 +10

0

Mill edge +25

0

b < 600 0.5600 b


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7.8 .3 .4 Th ickness - Thickness tolerance for cold rolled substrate shall apply to the sum ofthe specified thickness of the respective surface in Table 8.

Tab le 8 Th ickn ess To le rance fo r Co ld Ro l led Stee l Sheets

W i d t h ( mm) S l No Thickn ess

( mm) U p t o 1 2 5 0 B et w e en 1 2 5 0

a n d 1 6 0 0

A bov e 1600

(1) (2) (3) (4) (5)

i) Up to 0.60 +/-0.05 +/-0.06 -

ii) 0.60-0.80 +/-0.06 +/-0.07 +/-0.08

iii) 0.80-1.00 +/-0.06 +/-0.08 +/-0.10

iv) 1.00-1.25 +/-0.09 +/-0.10 +/-0.12

v) 1.25-1.60 +/-0.11 +/-0.12 +/-0.14

8. COATI NG TEST

8.1 Test Sam ple

One set of three samples each of area 50 mm square (50 x 50) shall be selected at randomfrom one sheet for every 1000 coated sheets or components thereof. The three samples shall

be taken: one from the middle of the width of the sheet and one from each side of the sheet.The samples for the extremities, diagonals or from the side of the sheet shall not be closerthan 75 mm from the edge of the sheet. In case of coils, one set of three samples each of 50mm square shall be selected from one end of each coil along the length, across the width.

8.2 Determ ina t ion o f Mass o f Z inc Coat ing

The average mass of zinc coating of samples as selected under 8 .1 and determined by themethod given in IS 6745 or by any other established instrumental or chemical method shallconform to both the values specified in Table 5.

9 RETESTS

9 .1 If any test sample fails to meet test requirements given in 8 and 9 , two more set of test

samples shall be taken for the specific test requirements from the same list.

9 .2 If any of the retest samples fails to meet the requirements of this standard, the entirebatch of sheets represented by the sample shall be deemed as not confirming to the standard.

10 MARKI NG

Unless otherwise specified, the following information shall be legibly displayed on top of eachpacket of sheets or on a tag attached to each coil,

a) manufacturers name;b) number of this standard;c) quality designation;d) coating designation;e)

order number;f) product dimension;

g) lot number; andh) the mass.

11 COATI NG DESI GNATI ON

The coating designation shall be as per the following procedure


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1st and 2nd character: To represent coating weight designation usually heavier coated side.

3rd character: To represent type of coating composition where

G = Plain zincA = Zinc-iron

4th and 5th character: To represent type of coating process adopted

GE = ElectrogalvanisedGI = Hot dip galvanizedGA = Galvannealed

6th character: To represent surface protection after coating

C = Chromated and oiledO = Only oiledU = As coated (i.e. untreated)

An example:

40 G GA CI II III IV

I Coating weight on the top sideII Type of coating compositionIII Type of coating processIV Surface protection after coating

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