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IS 7754 (1975): Method for designation of microstructure ofgraphite in cast iron [MTD 22: Metallography and HeatTreatment]

Is 5 7754 - 1975

Indian Standard

METHOD FOR DESIGNATION OF THE MICROSTRUCTURYiZ

OF GRAPHITE IN-CAST IRON ’

Metallography and Heat Treatment Sectional Committee, SMDC 27

Chairman SHRI K.V.CHINNAPPA

Members SHRl M. ANJANEYULU

SHRIN. V.RAQHWAN (Alkmak) SI~RI N. C. BACCHI SHRI S. N.B~ERJEE SHRI S. S.BHATNAQAR DRS. K. CHA~TERJEE

SHRI S.K.Bmu (Altiak) SHRIDASARATHA

SHRIB.HARIDASACHAR (Alkrnuk) SHRID.M.DAVAR DEPIITY DIRECTOR (MET)-3 RDSO, LUCKNCW

CHEMIST & METALLURGIST ~Alkmatci SHRI A. K. GUHA

SHRI P. C. MUSTAPI (Afkrnak) SHRI H. A. JAISINCHANI

SHRIA.R.RANADIVE (Alternate) SHRI M.L.KATYAL DR D.M.LAKHIANI

SHRI D. R. DASQWTA (Altcrnufe) SHRI N. MAJUMDAR

SHRI S. N. BOSE (A&mate) DR G. MUKHERJEE

SHRI D. K. BA~CHI (Alkrnate) SHRI A. PADMANABHAN SHRI B. M. PAI

SHRI S. A. MALW~E (Alkrnak) DR P. S. PATTIHAL

SHRI J. C. KAPOOR (Alkrmk) SHRI N. M. RAJ~ SHRI B. RAMA &ISHNA

SHRI J. NA~ESH BHAT (Alkrnak) SIiRI V.RAMA SWAMY

SHRIR.H.G. RAU SHRI G. G. SAHA SHRI H.N.S:NGH DR L. R. VAIDYANATH

SHRI V. S. BHANDARY (dltcnaak) SHRI V. V. VIRBHADRAYYA

SHRI K. L. CH.4TTERJEE (.~&?7Zf?tC) SHRI SUBHASH WADHAVAN SHRI C.R.RAMARAO,

Director (Strut & Met)

. 8-f“

Representing International Nickel (India) Pvt Ltd, Bombay

Mmi;~rg3&pu~llied Machinery Corporation Limited,

National Test House, Calcutta Indian Institute of Metals, Calcutta National Metallurgical Laboratory (CSIR), Jamshedpur Guest, Keen, Williams Ltd, Howrah

Mysore Iron & Steel Ltd, Bhadravati

Premier Automobiles Ltd, Bombay Ministry of Railways

Directorate General of Supplies & Disposals (Inspection Wing), New Delhi

Mahmdra & Mahindra Ltd, Bombay

Bajaj Auto Ltd, Poona Indian Iron & Steel Co Ltd, Bumpur

Indiio Aluminium Co Ltd, Calcutta

Hmdustan Steel Ltd, Ranchi

Ashok Leyland Ltd, Madras The Alloy Steel Producers’ Association of India, Bombay

Tata Engineering & Locomotive Co Ltd, Jamshedpur

Hindustan Motors Ltd, Uttarpara Indian Telephone Industries Ltd, Bangalore

Ministry of D’eGnoe-(DGI), Department of Defence Production ’

Mukand Iron & Steel Works Ltd, Bombay Ministry of Defence (R & D) Textile Machinery Corporation Ltd, Belgharia Indian Copper Information Centre, Calcutta

Direcge;;e General of Technical Development, New

Murarka Engineering Works, New Delhi Director General, IS1 (E.wq@io Member)

Secretary SHRIB.MUKHERJI

$eputy Director (Met), IS1

Q Copyright 1976

INDIAN STANDARDS INSTITUTION

This publication is protected under the Indiun Copyright Act (XIV of 1957) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an

infringement of copyright under the said Act.

IS t 7754 - 1975

Indian Standard

METHOD FOR DESIGNATION OF THE MICROSTRUCTURE

OF GRAPHITE IN CAST IRON 0. FOREWORD

0.1 This Indian Standard was adopted by the Indian Standards Institution on 31 July 1975, after the draft finalized by the Metallography and Heat Treatment Sectional Committee had been approved by the Structural and Metals Division Council.

0.2 This standard has been prepared in order to establish a uniform practice for evaluation and classification of graphite in cast iron.

0.3 In the preparation of this standard assistance has been derived from the following:

ISO/R 945-1969 Designation of the microstruc-

ture of graphite in cast iron. International Organization for Standardization.

ASTM A 247-67 Evaluating the microstructure of graphite in iron, castings. for Testing and Materials,

American Society

0.4 In reporting the result of a test or analysis made in accordance with this standard, if the final value, observed or calculated, is to be rounded off, it shall be done in accordance with IS : 2-1960*.

*Rules for rounding off numerical values (revised).

1. SCOPE

1.1 This standard covers the evaluation and classi- fication of graphite in cast iron in terms of its form, distribution and size. This standard is applicable for all iron-carbon alloys containing graphite particles, and may be applied to grey iron, malle- able iron and spheroidal graphite or ductile iron.

2. CLASSIFICATION

2.1 When examining iron-carbon alloys under a microscope, the graphite occurring in these alloys can be classified by:

a) its form (designated by Ron& numerals, se6 Fig. 1),

b) its distribution (designated by capital letters, see Fig. 2), and

c) its size (designated by Hindu-Arabic nume- rals, see Fig. 3 to 6).

2.2 The three series of reference diagrams includ- ed in this standard for evaluating the type of graphite form the basis for such a classification. The characteristic features of the graphite which occur are designated by letters and numerals. For this purpose, microstructures of graphite are arranged side by side in the series. Form, dis- tribution and size of the graphite observed are determined by comparison wi& the diagrams and the allocation of the same ‘classification as the diagrams that resemble them most closely.

2.3 The comparison of the graphite observed with the three series of reference diagrams in Fig, 1 to 6 does not give any information on the suitability of the iron-carbon alloys for any particular service.

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3. SAMPLING AND PREPARATION OF SPECIMENS

3.1 While taking specimens from the casting, attention shall be paid to the location, to the wall thickness, to the distance from the surface and to the presence of chills and the like. The location of the surface examined shall be mutually agreed upon between the purchaser and the manufacturer.

3.2 The area of polished surface should be suffi- cient to give a true representation of the graphite distribution. The area of the specimen shall not be less than 100 nuns. Attention should be paid to the careful grinding and polishing of the speci- mens in order that the graphite particles appear in tbelptcue form and size. The examination of the

graphite under the microscope is normally carried out on the unetched polished section, though final etching is recommended in the case of some special alloy cast irons, for example, those containing high silicon.

NOTE -An Indian Standard code of practice for pre- paration of metallographic specimens of cast iron is under preparation. Until this code is published the method of preparation of samples may be as agreed to between the contracting parties.

4. MICROSCOPIC EXAMINATION

4.1 The polished specimens shall be viewed under a microscope at any convenient magnification below 100 x to facilitate examination of the entire polished area. A comparison shall lirst be made with the reference diagrams to determine the percentage of graphite both formwise and distributionwise

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IS : 7754 - 1975

particle size which is half that of the larger size range.

6. DESIGNATION OF GRAPHITE BY FORM, DISTRIBUTION AND SIZE

6.1 To characterize the graphite observed, indi- cations are generally necessary on the form, distri- bution and size of the graphite particles. To this purpose, the Roman numerals of Fig. 1 are used for the form, the capital letters of Fig. 2 for the distribution and the Hindu-Arabic numerals of Fig. 3 and Table 1 for the size, in that order. Thus, for example, Type I A4 denotes graphite particles, Form 1 (Fig. I), Distribution A (Fig. 2), having linear dimensions in the range of 12 to 25 mm at 100 x magnification (Fig. 3 to 6 and Table 1).

6.2 Jf the graphite observed lies between two sizes, reference to both is possible (for example, 3/4). In a given case the predominating size may be em- phasized by underlining (for example, 3/4). This method can be extended to cover struc&es where more than two sizes are present.

6.3 Mixed structures with different types of gra- phite may be defined by estimating the percentage proportion of the different types of graphite. For example:

60 percent I A4+40 percent I D7 means 60 percent graphite of the Form I, Distribu- tion A and size 4, and 40 percent graphite of the Form I, Distribution D and size 7.

(see Fig. 1 and 2). Following this, the size of the graphite particles is det.ermined at a magnification of 100 x , by reference to Fig. 3 to 6 inclusive and Table 1.

4.2 Examination under the microscope can be carried out by direct observation or by projection on the ground glass of the microscope. A field of view approximately of the same size as the reference diagrams (about 80 mm diameter) facilitates comparison.

4.3 The measurement of the size of graphite particles is also facilitated by the use of suitably calibrated eye-pieces.

4.4 It is a common practice in malleable iron to use nodule count per unit area instead of a comparison chart. Nodule count with known free carbon content is a measure of calculated nodule area.

4.5 The measurement of size of Form II graphite shall be as agreed to between the contracting parties.

5. REFERENCE DIAGRAMS

5.0 A series ‘of reference diagrams is provided for form, distribution and size of graphite. The reference diagrams show micrcstructures of an ideal character instead of actual photomicro- graphs.

5.1 Reference Diagrams for Graphite Form - The reference diagrams for graphite form (Fig. 1) show six characteristic forms which are designated by the Roman numerals I to VI. These re- present the principal types of graphite found in cast iron. However, other forms are also known to occur occasionally.

5.2 Reference Diagrams for Graphite Distri- bution - The reference diagrams for graphite distribution (Fig. 2) show five examples designat@ by the letters A to E. The diagrams in Fig. 2 apply to Form I graphite. The other forms generally occur in Distribution A, but other distributions may sometimes be found.

5.3 Reference Diagrams for Graphite Size - Figures 3 to 6 and Table 1 serve to determine the graphite size. For the ‘100 x ’ magnification re- production scale, sizes are indicated ranging from a maximum dimension of the particle of over 100 mm (size 1) down to less than I.5 mm (size 8). The size ranges covered by the size reference numbers 3 to 7 inclusive are based on an average

TABLE 1 DIMENSIONS OF THE GRAPHITE PARTICLES - FORMS I TO VI

(Clauser 4.1, 5.1 and 6.1)

KEF No.

(1)

DIMENSION OF THE PARTICLES OBSERVED AT 100 x MAGNI-

FlOATION

(2)

.,’ 50 to 100

25 ,, 50

12 ,, 25

6 J, 12

3 6 ,)

1.5 3 ,J

Less than 1.5

TRUE DIMENSION

(3) mm

Over 1

0.5 to 1

O-25 ,I 0.5

0.12 ,, 0.25

0.06 ,) 0.12

0.03 ,, 0.06

0.015 ), 0.03

Less than 0.015

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Form I Flake

Form III Worm

Form V Amoeba Form VI Round

FIG, 1 REFERENCE DIAGRAM* FOR THE GRAPHITE FORM ( DISTRIBUTION A )

*The diagrams show only the outline and not the structure of the graphite.

Form II Star

Form IV Chinese Script

.’ -G-*.

_’

/ 4

Distribution A Uniformly Distributed Random Flakes

Distribution C Superimposed Flakes, Randordbrientation

Distribution B Rosset Grouping, Random Orient&ion

Distribution D lnterdendritic Segregation, Random Orientation

Distribution E lnterdandritic Segregation, Preferred Orientation

FIG. 2 REFERENCE DIAGRAM* FOR THE DISTRIBUTION OF GRAPHITE (FORM 1)

*The diagrama s* only the outline and not the rtructurc OF the graphite.

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IS : 7754 - 1975

I’

I S‘! 2

FIG. 3 REFERENCE DIAGRAM* FOR THE DIMENSION OF GRAPHITE FORM I AND DISTRIBUTION A (100 x MAOMFICATION) +RW%ICENCE No. 1 AND 2 ,’

*The d&rams show only the outline and not the structure of the graphite.

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IS : 7754 - 1975

FIG. 4 REFERENCE DIAGRAM* FOR THE DIMENSION OF GRAPHITE FORMS I AND VI AND DISTRIBUTION A .(\OO x MAGNIFICATION) - REFERENCE No. 3 AND 4

*The diagrams show only the outline and not the structure of the graphite.

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J

Is : 7754 - 1975

6

FIG. 5 REFERENCE DIAGRAM* FOR THE DIMENSION OF GRAPHITE FORMS I AND VI AND

DISTRIBUTION A (100 x ?@AGNIFICATION) - REFERENCE No. 5 AND 6 t

*The diagrams show only the outline and not the structure of the graphite.

8

J

/

IS : 7754 - 1975

8

‘0 l . :;. * . l . *:-.

FIG. 6 REFERENCE DIAGRAM* FOR THE DIMENSION OF GRAPHITE FORMS I AND VI AND DISTRIBUTION A (100 x MAGNIFICATION) -REFERENCE No. 7 AND 8

*The diagrams show only the outline and not the structure of the graphite.

9