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ASTM A247 - 10.pdf

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ASTM A247 - 10.pdf

Designation A247 − 10Standard 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 revision. 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 Department of Defense.1. Scope1.1 This test method covers the classification of graphite incast irons in terms of type, distribution, and size. This testmethod is intended to be applicable for all iron-carbon alloyscontaining graphite particles, and may be applied to gray irons,malleable irons, and the ductile nodular irons.1.2 The reference standards included in this test method arein no way to be construed as specifications. In an appropriatespecification for a specific material where graphite microstruc-ture is an important consideration this test method may be usedas a reference to define concisely the graphite microstructurerequired.1.3 These standards are offered primarily to permit accuratereporting of microstructures of cast irons and to facilitate thecomparison of reports by different laboratories or investigators.1.4 The values stated in SI units are to 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 determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards2E3 Guide for Preparation of Metallographic Specimens2.2 ASTM AdjunctsGraphite Microstructure in Gray Iron 3 Plates3Iron Casting Graphite Microstructure Rating Chart WallChart43. Summary of Test Method3.1 The reference diagrams included in this standard formthe basis for classification. Characteristic features of graphiteparticles are designated by numerals and letters. Type, distri-bution, and size of observed graphite are compared with theidealized microstructures in the standard charts and ratedaccordingly as closely as possible to the equal or similarmicrostructures 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 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. When this is impractical, a testlug or projection often can be cast attached to the casting andsawed or broken off to be used as the sample. If neither of thesemethods is convenient, microscopical test coupons, such as thatrecommended by the Ductile Iron Research Committee 12Kof the American Foundrymen’s Society5should be cast frommetal representative of the castings poured.6. Polishing6.1 Grinding and polishing may follow the usual acceptedmetallographic procedures as covered in Methods E3, except1This 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 March 1, 2010. Published April 2010. Originallyapproved in 1941. Last previous edition approved in 2009 as A247 – 061. DOI10.1520/A0247-10.2For 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 standard’s Document Summary page onthe ASTM website.3Available from ASTM International Headquarters. Order Adjunct No.ADJA0247. Original adjunct produced in 1977 .4Available from ASTM International Headquarters. Order Adjunct No.ADJA0247A. Original adjunct produced in 2010.5Transactions, American Foundrymen’s Society, 1960, p. 655.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1that care must be taken that the graphite is retained at thepolished surface and not torn or dragged out. Use of diamondpowder polishing compound in one of the final stages ofpolishing is very effective in retaining the graphite at thepolished surface.7. Classification of Graphite Form with Chart7.1 The graphite form type chart Plate I6is used as areference standard by scanning the polished specimen underthe microscope and noting the graphite forms in the micro-structure that more nearly correspond to type designations onthe chart.7.2 Type I is the normal and usually desirable graphite formin ductile iron, although the presence of Type II graphite formshas little or no adverse effect on properties. Graphite formsrepresented by Types IV through VI often occur in ductile ironin conjunction with Types I and II. The percentages of eachgraphite type are estimated by observation, or better, bycounting the particles of each type. Types present in a sampleare to be reported in percentages to total 100. Any convenientmagnification that clearly reveals the graphite form may beused.7.3 Type III is the graphite form most often seen inmalleable iron castings after annealing. Some malleable ironsmay contain Types I or II graphite particles also.7.4 Type IV is the predominant graphite form in compactedvermicular graphite iron. However, the microstructure istypically evaluated by the percentage of Types I and II that arecommonly observed.7.5 Type VII is the flake graphite form usually seen in grayiron.8. Classification of Graphite Distribution with Chart8.1 The graphite distribution chart Plate II6is usefulprincipally in rating flake graphite, Type VII, distributions ingray cast iron. Occasionally, however, graphite in malleable orductile iron may occur in a nonrandom distribution patternwhich the distributions B to E may be used to describe.9. Classification of Graphite Size by Chart9.1 Two series of size charts, one for flake graphite, and onefor nodules, are shown in Plate III6to facilitate comparisons.At exactly 100 diameters magnification the maximum dimen-sion of the graphite particles for the various size classes areshown in Table 1.9.2 For direct comparison with the size classes in Plate III,the specimen to be evaluated should be projected on the groundglass screen, or photographed, at a magnification of exactly100 diameters. Usually visual comparison with the chart isadequate to define the size class. If carefully calibrated, ocularscales may be used to measure the serpentine length dimensionof flakes or the diameter of nodules. Where a mixture of one ormore 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 malleable ironto use nodule count per unit area instead of a comparison chartas given here. Nodule count, with known free carbon content,is a measure of calculated average nodule area.10. Report of Graphite Microstructure10.1 To report the microstructure of graphite in cast iron theheadings to be used are as follows Sample identification;graphite form type or types; graphite distribution; graphite sizeclass.10.2 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 8.10.3 Graphite distribution is always designated for flakegraphite irons, but may be omitted for malleable and ductileiron.10.3.1 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 appropriate percent-ages, 70 VII A4, 30 VII D7.10.3.2 A high-quality ductile iron could be designated I6. Aslightly inferior ductile iron, with somewhat insufficient nodu-lizing alloy, might be 70 I6, 30 IV5.10.3.3 Graphite in malleable irons may be similarly desig-nated as Types III, II, or I and the size from the nodular sizechart.6Plates I, II, and III may be obtained from ASTM Headquarters. OrderADJA0247.TABLE 1 Graphite SizeSize Class Maximum Dimension at 100, mmA1 12826433241658647281AThe gradation of sizes shown in each size class from the maximum dimensionwere computer 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 − 102ASTM International takes no position respecting the validity of any patent 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 revision 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 comments 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 copyrighted 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-mail; or through the ASTM websitewww.astm.org. Permission rights to photocopy the standard may also be secured from the ASTM website www.astm.org/COPYRIGHT/.A247 − 103

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