1、Designation: A247 16A247 16aStandard 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 la
2、st 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 classi
3、fication of graphite in cast irons in terms of type, distribution, and 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 graphite
4、irons, and the ductile (nodular) irons.1.2 The reference photomicrographs included in this test method are in no way to be construed as specifications. In anappropriate specification for a specific material where graphite microstructure is an important consideration, this test method maybe used as a
5、 reference to define concisely the graphite microstructure required.1.3 These reference photomicrographs are offered primarily to permit accurate reporting of microstructures of cast irons and tofacilitate the comparison of reports by different laboratories or investigators.1.4 The values stated in
6、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 appropriate safety and hea
7、lth 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:Iron Casting Graphite Microstructure Rating Chart (Wall Chart)33. Summary of Test Method3.1 The referen
8、ce micrographs included in this standard form the basis for classification. Characteristic features of graphiteparticle shape and distribution are designated by numerals and letters. Type, distribution, and size of observed graphite arecompared with the idealized microstructures in the standard char
9、ts and rated accordingly as closely as possible to the equal orsimilar microstructures in the charts.4. Significance and Use4.1 The comparison of observed graphite particles with the structures shown in the charts give only purely descriptiveinformation on the type, distribution, and size of the gra
10、phite in the sample being evaluated. It does not indicate, except in a verybroad way, the origin of the graphite or the suitability of the iron-carbon alloy for a particular service.5. Test Specimens or Samples5.1 The preferred sample is a section cut from an actual casting that is being evaluated a
11、t a location agreed upon between themanufacturer and purchaser. When this is impractical, a test lug or projection often can be appended to the casting and sawed or1 This test method is under the jurisdiction of ASTM Committee A04 on Iron Castings and is the direct responsibility of Subcommittee A04
12、.21 on Testing.Current edition approved March 15,April 1, 2016. Published April 2016. Originally approved in 1941. Last previous edition approved in 20102016 asA247 10.A247 16. DOI: 10.1520/A0247-16.10.1520/A0247-16A.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM
13、 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 International Headquarters. Order Adjunct No. ADJA0247A. Original adjunct produced in 2010.This document is not an ASTM st
14、andard and is intended only to provide the user of an ASTM standard 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 ca
15、ses only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1broken off to be used as the test sample. If neither of these methods is conven
16、ient, microstructural test coupons, such as thatrecommended by the Cast Iron Research Committee (5R) of theAmerican Foundry Society4 shall be cast from metal representativeof the castings poured.6. Polishing6.1 Grinding and polishing may follow the usual accepted metallographic procedures as covered
17、 in Guide E3, except that caremust be taken that the graphite is retained at the polished surface and not torn or dragged out. Use of diamond powder polishingcompound in one of the final stages of polishing is very effective in retaining the graphite at the polished surface.7. Classification of Grap
18、hite Form Using Chart7.1 The graphite form type chart (Fig. 1) 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. Thepercentages of each graphite type
19、 are estimated by observation, or better, by counting the particles of each type. Types present ina sample are to be reported in percentages to total 100. Any convenient magnification that clearly reveals the graphite form maybe used.7.2 Type I graphite is nodular in shape and is the normal and usua
20、lly desirable graphite form in ductile iron.7.3 Type II graphite 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
21、 Types I or II graphite particles.7.5 Type 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
22、iron in conjunction with Types I and II.7.7 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 Using Chart8.1 The graphite distr
23、ibution chart (Fig. 2) is useful principally in rating flake graphite, Type VII, distributions in gray cast iron.Graphite in malleable iron may occur in a nonrandom distribution pattern which the distributions B to E may be used to describe.9. Classification of Graphite Size by Chart9.1 This method
24、categorizes the graphite particles by size into eight classes. Figs. 3-5 show size classes for flake graphite andnodular graphite to facilitate comparisons. The maximum dimension of the graphite particles for the various size classes are listedin Table 1.9.2 For direct comparison with the size class
25、es in Figs. 3-5, the specimen to be evaluated shall be captured at the magnificationof exactly 100. Usually visual comparison with the chart is adequate to define the size class. Where a mixture of one or moresizes occurs in the same sample, the sizes may be reported as percentages of the total grap
26、hite area represented by the sizes4 Transactions, American Foundrymens Society, 1960, p. 655.TABLE 1 Graphite SizeSize Class Actual Dimension (m)A1 12801 $ 12802 640 to 12803 320 to 6404 160 to 3205 80 to 1606 40 to 807 20 to 408 108 20AThe gradation of sizes shown in each size class from the maximu
27、m 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 16a2involved. It is a commo
28、n practice in malleable irons to use nodule count per unit area instead of a comparison chart as given here.Nodule count, with known free carbon content, is a measure of calculated average nodule area.FIG. 1 Graphite Types Found in Iron CastingsA247 16a310. Nodularity10.1 Nodularity (Fig. 6 and Fig.
29、 7) is expressed by counting the nodular particles and reporting the results as a percentage ofthe total amount of graphite present in the microstructure. Ductile irons typically exhibit a nodularity between 80 to 100 %, grayFIG. 2 Graphite Distribution Typically Used to Rate Type VII Flake Graphite
30、 in Gray Iron (100)A247 16a4irons a nodularity of 0 %, and compacted graphite irons a nodularity of 0 to 20 %. Nodularity should be assessed by evaluatingmore than one field of view. The final report should state the number of fields of view or area of the sample evaluated. The locationof the measur
31、ement should be agreed upon between the manufacturer and purchaser.11. Nodule Count11.1 Nodule count is expressed 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 nodul
32、e count for each section size ofcasting, and nodule counts in excess of this range may result in a degradation 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
33、 % nodularity, respectively.FIG. 3 Size Class 1 Through 4 Flake Graphite (100)A247 16a512. Report of Graphite Microstructure12.1 To report the microstructure of graphite in cast iron the headings to be used are as follows: Sample identification; graphiteform type or types; graphite distribution; gra
34、phite 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 numeral 1 through 8.12.3 Graphite distribution is always designated for flake graphite irons, bu
35、t 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. Mixtures of these two may be described by giving both ratings with appropriate percentages,7
36、0 % VII A4, 30 % VII D7.FIG. 4 Size Class 5 Through 8 Flake Graphite (100)A247 16a612.3.2 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 malleable irons may be similarly desi
37、gnated 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 shall be reported as the number o
38、f graphite nodules / mm2.FIG. 5 Size Class 4 Through 7 Nodular Graphite (100)A247 16a7FIG. 6 Nodularity Examples (100)NOTE 1Compacted Graphite Iron Nodularity Rating Chart (Wall Chart). Available from SinterCast, .A247 16a8FIG. 7 Nodularity Examples (100)NOTE 1Compacted Graphite Iron Nodularity Rati
39、ng Chart (Wall Chart). Available from SinterCast, .A247 16a9FIG. 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 16a10FIG. 9 Nodule Count of 90 % Nodularity Ductile Iron (100)NOTE 1
40、Graphite Rating in Ductile Iron (Wall Chart). Available from the Ductile Iron Society, www.ductile.org.A247 16a11FIG. 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 16a12APPENDIX(N
41、onmandatory 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 of any patent rights asserted in connection with any item mentioned
42、in 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 m
43、ust 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 th
44、eresponsible 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 C70
45、0, 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 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 16a13
