1、Designation: A247 10A247 16Standard 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 las
2、t 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 U.S. Department of Defense.1. Scope1.1 This test method covers the classif
3、ication of graphite in cast irons in terms of type, distribution, and size. size by visualcomparison to reference photomicrographs. This test method is intended to be applicable for all iron-carbon alloys containinggraphite particles, and may be applied to gray irons, malleable irons, compacted grap
4、hite irons, and the ductile (nodular) irons.1.2 The reference standardsphotomicrographs included in this test method are in no way to be construed as specifications. Inan appropriate specification for a specific material where graphite microstructure is an important consideration, this test methodma
5、y be used as a reference to define concisely the graphite microstructure required.1.3 These standards reference photomicrographs are offered primarily to permit accurate reporting of microstructures of castirons and to facilitate the comparison of reports by different laboratories or investigators.1
6、.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish ap
7、propriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic Specimens2.2 ASTM Adjuncts:Graphite Microstructure in Gray Iron (3 Plates)3Iron Casting Graphite Microstru
8、cture Rating Chart (Wall Chart)33. Summary of Test Method3.1 The reference diagramsmicrographs included in this standard form the basis for classification. Characteristic features ofgraphite particles particle shape and distribution are designated by numerals and letters. Type, distribution, and siz
9、e of observedgraphite are compared with the idealized microstructures in the standard charts and rated accordingly as closely as possible to theequal or similar microstructures in the charts.4. Significance and Use4.1 The comparison of observed graphite particles with the structures shown in the cha
10、rts give only purely descriptiveinformation on the type, distribution, and size of the graphite in the sample being evaluated. It does not indicate, except in a verybroad way, the origin of the graphite,graphite or the suitability of the iron-carbon alloy for a particular service.5. Test Specimens o
11、r Samples5.1 The preferred sample is a section cut from an actual casting that is being evaluated. evaluated at a location agreed uponbetween the manufacturer and purchaser. When this is impractical, a test lug or projection often can be cast attached appended to1 This test method is under the juris
12、diction of ASTM Committee A04 on Iron Castings and is the direct responsibility of Subcommittee A04.21 on Testing.Current edition approved March 1, 2010.15, 2016. Published April 2016April 2010. . Originally approved in 1941. Last previous edition approved in 20092010 asA247 06A247 10.1. DOI: 10.152
13、0/A0247-10.10.1520/A0247-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from ASTM Internation
14、al Headquarters. Order Adjunct No. ADJA0247ADJA0247A. Original adjunct produced in 19772010. .4 Available from ASTM International Headquarters. Order Adjunct No. ADJA0247A. Original adjunct produced in 2010.This document is not an ASTM standard and is intended only to provide the user of an ASTM sta
15、ndard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by AS
16、TM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1the casting and sawed or broken off to be used as the test sample. If neither of these methods is convenient, microscopicalmi-crostructural t
17、est coupons, such as that recommended by the DuctileCast Iron Research Committee (12K)(5R) of the AmericanFoundrymensFoundry Society4 shouldshall be cast from metal representative of the castings poured.6. Polishing6.1 Grinding and polishing may follow the usual accepted metallographic procedures as
18、 covered in MethodsGuide E3, exceptthat care must be taken that the graphite is retained at the polished surface and not torn or dragged out. Use of diamond powderpolishing compound in one of the final stages of polishing is very effective in retaining the graphite at the polished surface.7. Classif
19、ication of Graphite Form withUsing Chart7.1 The graphite form type chart (Plate I)6 is used as a reference standard by scanning the polished specimen under themicroscope and noting the graphite forms in the microstructure that more nearly correspond to type designations on the chart.7.1 Type I is th
20、e normal and usually desirable graphite form in ductile iron,The graphite form type chart (Fig. 1 although thepresence of Type II graphite forms has little or no adverse effect on properties. Graphite forms represented by Types IV throughVI often occur in ductile iron in conjunction withTypes I and
21、II. ) is used as a reference standard by scanning the polished specimenunder the microscope and noting the graphite forms in the microstructure that more nearly correspond to type designations on thechart. The percentages of each graphite type are estimated by observation, or better, by counting the
22、 particles of each type. Typespresent in a sample are to be reported in percentages to total 100. Any convenient magnification that clearly reveals the graphiteform may be used.7.2 Type I graphite is nodular in shape and is the normal and usually desirable graphite form in ductile iron.7.3 Type II g
23、raphite consists of slightly irregular nodules and has little or no adverse effect on properties of ductile iron.7.4 Type III is the graphite form most often seen in malleable iron castings after annealing. Some malleable irons may alsocontain Types I or II graphite particles also. particles.7.5 Typ
24、e IV is the predominant graphite form in compacted (vermicular) graphite iron. However, the microstructure is typicallyevaluated by the percentage of Types I and II that are commonly observed.7.6 Type V is the spiky graphite form occasionally seen in ductile iron in conjunction with Types I and II.7
25、.7 Type VI is the exploded nodule graphite form occasionally seen in ductile iron in conjunction with Types I and II.7.8 Type VII is the flake graphite form usually seen in gray iron.8. Classification of Graphite Distribution withUsing Chart8.1 The graphite distribution chart (Plate(Fig. 2 II) is us
26、eful principally in rating flake graphite, Type VII, distributions in graycast iron. Occasionally, however, graphite Graphite in malleable or ductile iron may occur in a nonrandom distribution patternwhich the distributions B to E may be used to describe.4 Transactions, American Foundrymens Society,
27、 1960, p. 655.TABLE 1 Graphite SizeSize Class Maximum Dimension at 100,mmActual Dimension (m)A1 1281 12802 642 6403 323 3204 164 1605 85 806 46 407 27 208 18 10AThe gradation of sizes shown in each size class from the maximum dimensionwere computer calculated at the National Bureau of Standards usin
28、g 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 162FIG. 1 Graphite Types Found in Iron CastingsA247 163FIG. 2 Graphite Distribution Typically Used to R
29、ate Type VII Flake Graphite in Gray Iron (100)A247 1649. Classification of Graphite Size by Chart9.1 Two series of size charts, one This method categorizes the graphite particles by size into eight classes. Figs. 3-5 show sizeclasses for flake graphite, and one for nodules, are shown in Plate IIIgra
30、phite and nodular graphite to facilitate comparisons. Atexactly 100 diameters magnification the The maximum dimension of the graphite particles for the various size classes areshownlisted in Table 1.9.2 For direct comparison with the size classes in Figs. 3-5Plate III, , the specimen to be evaluated
31、 should be projected on theground glass screen, or photographed, at ashall be captured at the magnification of exactly 100 diameters. 100. Usually visualcomparison with the chart is adequate to define the size class. If carefully calibrated, ocular scales may be used to measure theserpentine length
32、dimension of flakes or the diameter of nodules. Where a mixture of one or more sizes occurs in the same sample,the sizes may be reported as percentages of the total graphite area represented by the sizes involved. It is a common practice inFIG. 3 Size Class 1 Through 4 Flake Graphite (100)A247 165ma
33、lleable ironirons to use nodule count per unit area instead of a comparison chart as given here. Nodule count, with known freecarbon content, is a measure of calculated average nodule area.10. Nodularity10.1 Nodularity (Fig. 6 and Fig. 7) is expressed by counting the nodular particles and reporting
34、the results as a percentage ofthe total amount of graphite present in the microstructure. Ductile irons typically exhibit a nodularity between 80 to 100 %, grayirons a nodularity of 0 %, and compacted graphite irons a nodularity of 0 to 20 %. Nodularity should be assessed by evaluatingmore than one
35、field of view. The final report should state the number of fields of view or area of the sample evaluated. The locationof the measurement should be agreed upon between the manufacturer and purchaser.FIG. 4 Size Class 5 Through 8 Flake Graphite (100)A247 16611. Nodule Count11.1 Nodule count is expres
36、sed as the number of graphite nodules/mm2 and is performed at a magnification of 100. Generally,high nodule count indicates good metallurgical quality, but there is an optimum range of nodule count for each section size ofcasting, and nodule counts in excess of this range may result in a degradation
37、 of properties. Nodule count should be establishedbetween the manufacturer and the purchaser. Figs. 8-10 compare the nodule counts of ductile iron at 100 % nodularity, 90 %nodularity, and 80 % nodularity, respectively.FIG. 5 Size Class 4 Through 7 Nodular Graphite (100)A247 167FIG. 6 Nodularity Exam
38、ples (100)NOTE 1Compacted Graphite Iron Nodularity Rating Chart (Wall Chart). Available from SinterCast, .A247 168FIG. 7 Nodularity Examples (100)NOTE 1Compacted Graphite Iron Nodularity Rating Chart (Wall Chart). Available from SinterCast, .A247 169FIG. 8 Nodule Count of 100 % Nodularity Ductile Ir
39、on (100)NOTE 1Graphite Rating in Ductile Iron (Wall Chart). Available from the Ductile Iron Society, www.ductile.org.A247 1610FIG. 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 161
40、1FIG. 10 Nodule Count of 80 % Nodularity Ductile Iron (100)NOTE 1Graphite Rating in Ductile Iron (Wall Chart). Available from the Ductile Iron Society, www.ductile.org.A247 161212. Report of Graphite Microstructure12.1 To report the microstructure of graphite in cast iron the headings to be used are
41、 as follows: Sample identification; graphiteform type or types; graphite distribution; graphite size class.12.2 Graphite type, or types, is designated by a Roman numeral I through VII. Graphite distribution is designated by a capitalletter A through E. Graphite size is designated by an Arabic numera
42、l 1 through 8.12.3 Graphite distribution is always designated for flake graphite irons, but may be omitted for malleable and ductile iron.12.3.1 For example, a typical gray iron of normal graphite structure might be designated VII A4. If eutectiform graphite ispresent, the rating might be VII D7. Mi
43、xtures of these two may be described by giving both ratings with appropriate percentages,70 % VII A4, 30 % VII D7.12.3.2 Ahigh-quality ductile iron could be designated I6.Aslightly inferior ductile iron, with somewhat insufficient nodulizingalloy, might be 70 % I6, 30 % IV5.12.3.3 Graphite in mallea
44、ble irons may be similarly designated as Types III, II, or I and the size from the nodular size chart.12.4 Nodularity should be reported as a percentage of the total amount of graphite present in the microstructure. Themagnification and number of fields of view shall be reported.12.5 Nodule count sh
45、all be reported as the number of graphite nodules / mm2.APPENDIX(Nonmandatory Information)X1.1 ADDITIONAL MICROSTRUCTURESX1.1.1 Fig. X1.1 is a microstructure that may be observed in cast irons and is shown for informational purposes only.ASTM International takes no position respecting the validity o
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