ASTM A247-17 Standard Test Method for Evaluating the Microstructure of Graphite in Iron Castings.pdf

1、Designation: A247 17Standard Test Method forEvaluating the Microstructure of Graphite in Iron Castings1This standard is issued under the fixed designation A247; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis

2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method covers the classification

3、 of graphite incast irons in terms of type, distribution, and size by visualcomparison to reference photomicrographs. This test method isintended to be applicable for all iron-carbon alloys containinggraphite particles, and may be applied to gray irons, malleableirons, compacted graphite irons, and

4、the ductile (nodular)irons.1.2 The reference photomicrographs included in this testmethod are in no way to be construed as specifications. In anappropriate specification for a specific material where graphitemicrostructure is an important consideration, this test methodmay be used as a reference to

5、concisely define the graphitemicrostructure required.1.3 These reference photomicrographs are offered primarilyto permit accurate reporting of microstructures of cast ironsand to facilitate the comparison of reports by different labora-tories or investigators.1.4 The values stated in SI units are to

6、 be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and

7、 determine the applica-bility of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-m

8、endations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic Specimens2.2 ASTM Adjuncts:Iron Casting Graphite Microstructure Rating Chart (WallChart)33. Summary of Test Method3.1 The

9、reference micrographs included in this standardform the basis for classification. Characteristic features ofgraphite particle shape and distribution are designated bynumerals and letters. Type, distribution, and size of observedgraphite are compared with the idealized microstructures in thestandard

10、charts and rated accordingly as closely as possible tothe equal or similar microstructures in the charts.4. Significance and Use4.1 The comparison of observed graphite particles with thestructures shown in the charts give only purely descriptiveinformation on the type, distribution, and size of the

11、graphite inthe sample being evaluated. It does not indicate, except in avery broad way, the origin of the graphite or the suitability ofthe iron-carbon alloy for a particular service.5. Test Specimens or Samples5.1 The preferred sample is a section cut from an actualcasting that is being evaluated a

12、t a location agreed uponbetween the manufacturer and purchaser. When this isimpractical, a test lug or projection often can be appended tothe casting and sawed or broken off to be used as the testsample. If neither of these methods is convenient, microstruc-tural test coupons, such as those recommen

13、ded by the Cast Iron1This test method is under the jurisdiction of ASTM Committee A04 on IronCastings and is the direct responsibility of Subcommittee A04.21 on Testing.Current edition approved July 1, 2017. Published July 2017. Originally approvedin 1941. Last previous edition approved in 2016 as A

14、247 16a. DOI: 10.1520/A0247-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from ASTM Internati

15、onal Headquarters. Order Adjunct No.ADJA0247A. Original adjunct produced in 2010.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on stan

16、dardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1Research Committee (5R) of the American Foundry Society4shall be cast from metal represe

17、ntative of the castings poured.6. Polishing6.1 Grinding and polishing may follow the usual acceptedmetallographic procedures as covered in Guide E3, except thatcare must be taken that the graphite is retained at the polishedsurface and not torn or dragged out. Use of diamond powderpolishing compound

18、 in one of the final stages of polishing isvery effective in retaining the graphite at the polished surface.7. Classification of Graphite Form Using Chart7.1 The graphite form type chart (Fig. 1) is used as areference standard by scanning the polished specimen underthe microscope and noting the grap

19、hite forms in the micro-structure that more nearly correspond to type designations onthe chart. The percentages of each graphite type are estimatedby observation, or better, by counting the particles of each type.Types present in a sample are to be reported in percentages tototal 100.Any convenient

20、magnification that clearly reveals thegraphite form may be used.7.2 Type I graphite is nodular in shape and is the normal andusually desirable graphite form in ductile iron.7.3 Type II graphite consists of slightly irregular nodulesand has little or no adverse effect on properties of ductile iron.7.

21、4 Type III is the graphite form most often seen inmalleable iron castings after annealing. Some malleable ironsmay also contain Type I or II graphite particles.7.5 Type IV is the predominant graphite form in compacted(vermicular) graphite iron. However, the microstructure istypically evaluated by th

22、e percentage of Types I and II that arecommonly observed.7.6 Type V is the spiky graphite form occasionally seen inductile iron in conjunction with Types I and II.7.7 Type VI is the exploded nodule graphite form occasion-ally seen in ductile iron in conjunction with Types I and II.7.8 Type VII is th

23、e flake graphite form usually seen in grayiron.8. Classification of Graphite Distribution Using Chart8.1 The graphite distribution chart (Fig. 2) is useful princi-pally in rating flake graphite, Type VII, distributions in graycast iron. Graphite in malleable iron may occur in a nonrandomdistribution

24、 pattern which the distributions B to E may be usedto describe.9. Classification of Graphite Size by Chart9.1 This method categorizes the graphite particles by sizeinto eight classes. Figs. 3-5 show size classes for flake graphiteand nodular graphite to facilitate comparisons. The maximumdimension o

25、f the graphite particles for the various size classesare listed in Table 1.9.2 For direct comparison with the size classes in Figs. 3-5,the specimen to be evaluated shall be captured at the magni-fication of exactly 100. Usually visual comparison with thechart is adequate to define the size class. W

26、here a mixture ofone or more sizes occurs in the same sample, the sizes may bereported as percentages of the total graphite area representedby the sizes involved. It is a common practice in malleableirons to use nodule count per unit area instead of a comparisonchart as given here. Nodule count, wit

27、h known free carboncontent, is a measure of calculated average nodule area.10. Nodularity10.1 Nodularity (Fig. 6 and Fig. 7) is expressed by countingthe nodular particles and reporting the results as a percentageof the total amount of graphite present in the microstructure.Ductile irons typically ex

28、hibit a nodularity between 80 to100 %, gray irons a nodularity of 0 %, and compacted graphiteirons a nodularity of 0 to 20 %. Nodularity should be assessedby evaluating more than one field of view. The final reportshould state the number of fields of view or area of the sampleevaluated. The location

29、 of the measurement should be agreedupon between the manufacturer and purchaser.11. Nodule Count11.1 Nodule count is expressed as the number of graphitenodules/mm2and is performed at a magnification of 100.Generally, high nodule count indicates good metallurgicalquality, but there is an optimum rang

30、e of nodule count for eachsection size of casting, and nodule counts in excess of thisrange may result in a degradation of properties. Nodule countshould be established between the manufacturer and thepurchaser. Figs. 8-10 compare the nodule counts of ductile ironat 100 % nodularity, 90 % nodularity

31、, and 80 % nodularity,respectively.4Transactions, American Foundrymens Society, 1960, p. 655.TABLE 1 Graphite SizeSize Class Actual Dimension (m)A1 $ 6402 320 to 6403 160 to 3204 80to1605 40to806 20to407 10to208AThe gradation of sizes shown in each size class from the maximum dimensionwere computer

32、calculated at the National Bureau of Standards using data obtainedfrom actual micrographs (Wyman, L. L., and Moore, G. A., “Quantitative Metallo-graphic Evaluations of Graphite Microstructures,” Modern Castings, Vol 43, No. 1,Jan. 1963, p. 7).A247 172FIG. 1 Graphite Types Found in Iron CastingsA247

33、173FIG. 2 Graphite Distribution Typically Used to Rate Type VII Flake Graphite in Gray Iron (100)A247 17412. Report of Graphite Microstructure12.1 To report the microstructure of graphite in cast iron theheadings to be used are as follows: Sample identification;graphite form type or types; graphite

34、distribution; graphite sizeclass.12.2 Graphite type, or types, is designated by a Romannumeral I through VII. Graphite distribution is designated by acapital letter A through E. Graphite size is designated by anArabic numeral 1 through 8.12.3 Graphite distribution is always designated for flakegraph

35、ite irons, but may be omitted for malleable and ductileiron.12.3.1 For example, a typical gray iron of normal graphitestructure might be designated VIIA4. If eutectiform graphite ispresent, the rating might be VII D7. Mixtures of these two maybe described by giving both ratings with appropriateperce

36、ntages, 70 % VII A4, 30 % VII D7.FIG. 3 Size Class 1 Through 4 Flake Graphite (100)A247 17512.3.2 A high-quality ductile iron could be designated I6. Aslightly inferior ductile iron, with somewhat insufficient nodu-lizing alloy, might be 70 % I6, 30 % IV5.12.3.3 Graphite in malleable irons may be si

37、milarly desig-nated as Type III, II, or I and the size from the nodular sizechart.12.4 Nodularity should be reported as a percentage of thetotal amount of graphite present in the microstructure. Themagnification and number of fields of view shall be reported.12.5 Nodule count shall be reported as th

38、e number ofgraphite nodules/mm2.FIG. 4 Size Class 5 Through 8 Flake Graphite (100)A247 176FIG. 5 Size Class 4 Through 7 Nodular Graphite (100)A247 177FIG. 6 Nodularity Examples (100)NOTE 1Compacted Graphite Iron Nodularity Rating Chart (Wall Chart). Available from SinterCast, .A247 178FIG. 7 Nodular

39、ity Examples (100)NOTE 1Compacted Graphite Iron Nodularity Rating Chart (Wall Chart). Available from SinterCast, .A247 179FIG. 8 Nodule Count of 100 % Nodularity Ductile Iron (100)NOTE 1Graphite Rating in Ductile Iron (Wall Chart). Available from the Ductile Iron Society, www.ductile.org.A247 1710FI

40、G. 9 Nodule Count of 90 % Nodularity Ductile Iron (100)NOTE 1Graphite Rating in Ductile Iron (Wall Chart). Available from the Ductile Iron Society, www.ductile.org.A247 1711FIG. 10 Nodule Count of 80 % Nodularity Ductile Iron (100)NOTE 1Graphite Rating in Ductile Iron (Wall Chart). Available from th

41、e Ductile Iron Society, www.ductile.org.A247 1712APPENDIX(Nonmandatory Information)X1.1 ADDITIONAL MICROSTRUCTURESX1.1.1 Fig. X1.1 is a microstructure that may be observed incast irons and is shown for informational purposes only.ASTM International takes no position respecting the validity of any pa

42、tent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revisio

43、n at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your com

44、ments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyright

45、ed by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-

46、mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ X1.1 Widmansttten Graphite is shown magnified at 400 on the left and 1000 on the right.A247 1713