ASTM E768-1999(2018) 8125 Standard Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel.pdf

1、Designation: E768 99 (Reapproved 2018)Standard Guide forPreparing and Evaluating Specimens for AutomaticInclusion Assessment of Steel1This standard is issued under the fixed designation E768; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r

2、evision, 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.1. Scope1.1 This guide2covers two preparation methods for steelmetallographic specimens that will be analyzed

3、 for nonmetallicinclusions with automatic image analysis (AIA) equipment.The two methods of preparation are offered as acceptedmethods used to retain nonmetallic inclusions in steel. Thisguide does not limit the user to these methods.1.2 A procedure to test the suitability of the preparedspecimen fo

4、r AIA inclusion work, using differential interfer-ence contrast (DIC), is presented.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This international standard was developed in accor-dance with internationally recognized

5、 principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3E3 Guide for Preparation o

6、f Metallographic SpecimensE7 Terminology Relating to MetallographyE45 Test Methods for Determining the Inclusion Content ofSteelE883 Guide for ReflectedLight PhotomicrographyE1122 Practice for Obtaining JK Inclusion Ratings UsingAutomatic Image Analysis (Withdrawn 2006)4E1245 Practice for Determinin

7、g the Inclusion or Second-Phase Constituent Content of Metals by Automatic ImageAnalysis2.2 ASTM Adjuncts:5ADJE0768 Differential Interference Contrast Magnification100 and 500 (6 micrographs)3. Terminology3.1 Definitions:3.1.1 For definitions used in this practice, refer to Termi-nology E7.3.1.2 dif

8、ferential interference contrast microscopya com-prehensive definition appears in Guide E883, section 11.8.3.2 Definitions of Terms Specific to This Standard:3.2.1 rigid grinding diska non-fabric support surface,such as a composite of metal/ceramic or metal/polymer,charged with an abrasive (usually 6

9、 to 15-m diamondparticles), and used as the fine grinding operation in a metal-lographic preparation procedure.4. Significance and Use4.1 Inclusion ratings done either manually using Test Meth-ods E45 or automatically using Practice E1122 or E1245 areinfluenced by the quality of specimen preparation

10、. This guideprovides examples of proven specimen preparation methodsthat retain inclusions in polished steel specimens.4.2 This guide provides a procedure to determine if theprepared specimens are of suitable quality for subsequentrating of inclusions. None of these methods should be con-strued as d

11、efining or establishing specific procedures or limitsof acceptability for any steel grade.5. Preparation Methods5.1 Background:5.1.1 The inclusions in the plane of polish must be fullypreserved and clearly visible. Preparation should not produceexcessive relief around the perimeter of the inclusions

12、 thatwould exaggerate the size and number of inclusions on the1This guide is under the jurisdiction ofASTM Committee E04 on Metallographyand is the direct responsibility of Subcommittee E04.01 on Specimen Preparation.Current edition approved May 1, 2018. Published June 2018. Originallyapproved in 19

13、80. Last previous edition approved in 2010 as E76899(2010)1.DOI: 10.1520/E0768-99R18.2Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:E04-1002.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM C

14、ustomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.org.5A colored plate, consisting of six micrographs that illustrate

15、 the use of DIC indetermining a properly prepared sample (at 100x and 500x), is available fromASTM Headquarters. Order Adjuct: ADJE0768.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accord

16、ance with internationally recognized principles on standardization 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.1plane of polish. In many cases, t

17、he preparation of specimensfor inclusion rating is more readily performed after thespecimens have been hardened by a suitable heat treatmentprocedure (austenize, quench to fully martensitic structure,temper at a relatively low temperature).5.1.2 Cleanliness is an important consideration in all stage

18、sof specimen preparation.5.1.2.1 Heat-treated specimens should be wire brushed orshot blasted or have the surface ground to remove adherentscale.5.1.2.2 After completing the grinding steps and beforeperforming the polishing steps, the specimens and specimenholders must be cleaned to prevent contamin

19、ation of the nextpreparation step. Cleaning the specimens and specimen holdersbetween each grinding step can eliminate contamination ofcoarse abrasives to the following finer preparation step.5.1.2.3 After the preparation is complete, swab the surfacecarefully with cotton and a water/soap solution c

20、ontaining acorrosion inhibitor such as a machine coolant or ethyl alcoholsolution to remove any films or other debris that wouldinterfere with the inclusion rating.5.1.2.4 It is advisable to perform the inclusion analysis assoon as possible after preparation to minimize staining or otherproblems tha

21、t can affect the analysis.5.1.3 The two methods that follow have been found to bereliable procedures for retaining inclusions in steel and achiev-ing the desired results when evaluated by DIC. There are othermethods that will result in a quality specimen as revealed byDIC. Each laboratory should dev

22、elop preparation proceduresfor their materials so that the prepared surfaces meet therequirements presented in 6 of this guide.5.1.4 As described in Practice E3, the specimens may besectioned and mounted to ease handling during preparation. Itis advisable to use a mounting medium that is hard enough

23、 topreserve edges and maintain flatness.5.1.5 Abrasive grit size designations in this guide areexpressed in theAmerican National Standards Institute (ANSI)or Coated Abrasives Manufacturers Institute (CAMI) systemunits with the corresponding Federation of European AbrasiveProcedure (FEPA) numbers in

24、parentheses. Table 1 provides acorrelation between these two systems and the approximatemedian particle diameter for a given grit size in micrometres.5.1.6 Most preparation systems apply pressure on the speci-mens being processed. The best pressure to be used for eachpreparation step should be deter

25、mined experimentally. Conver-sions between applied force and pressure are discussed in theAppendix X1.NOTE 1Care must be taken to protect the polished specimen surfacefrom scratches or contaminants when using a specimen leveling device.5.2 Silicon Carbide Procedure:5.2.1 A summary of the silicon car

26、bide procedure can befound in Table 2.5.2.2 When using a semi-automatic polishing equipment,grinding and polishing should be performed using approxi-mately 18 kPa pressure per specimen. (For a specimen holdercontaining six 32-mm mounts, a force of approximately 87 Nmust be applied (see X1.4.2).5.2.2

27、.1 Low pressures are recommended to ensure theretention of an assortment of inclusion types found in a varietyof steel grades. The relatively low pressures suggested in thisprocedure will not necessarily result in a satisfactory polish foretching and the further evaluation of the specimens generalmi

28、crostructure. The pressures used in the following rigid diskprocedure are more likely to result in a surface more satisfac-tory for revealing general microstructures.5.2.3 Grind the specimens on ANSI 80 grit (P80 FEPA)silicon carbide paper to ensure all sectioning artifacts anddeformation damage hav

29、e been removed and the entire speci-men surface is co-planar to the grinding surface.NOTE 2If the sectioning method resulted in a smooth face and littledeformation damage, and if after securing the specimens in a fixture forpolishing, the entire surface of interest is co-planar to the grinding surfa

30、ce,then finer grit papers, such as ANSI 180 to 240 (P180 to P240 FEPA) canbe used for the initial grinding step.5.2.3.1 An adequate flow of water should remove all loos-ened abrasive and grinding debris from the paper during thegrinding procedure. The flow of water should ensure thespecimen is kept

31、cool during grinding.5.2.4 Continue grinding through the sequence of siliconcarbide papers listed in Table 2. It may be necessary to cleanthe samples between every grinding step to prevent contami-nation of the next preparation step.5.2.5 After completing the entire grinding operation, cleanthe spec

32、imens thoroughly, using ethyl alcohol and cotton, thenrinse and dry. Ultrasonic cleaning can be used.5.2.5.1 The use of a soap and water solution in an ultrasoniccleaner can attack non-metallic inclusions in some carbon andlow alloy steels, leading to an exaggeration in the inclusionsapparent size.

33、Adding an inhibitor (such as that used as amachining coolant) may reduce this size exaggeration.TABLE 1 Comparison of ANSI (CAMI) versus FEPA versusMedian Diameter of Grit Size in MicrometersANSIA(CAMI)BFEPACApproximate MedianDiameter(m)60 P60 25080 P80 180100 P100 150120 P120 125150 P150 90180 P180

34、 75220 P220 63240 P240 58.5P280 52.2280 P320 46.2320 P360 40.5P400 35.0360 P500 30.2400 P600 25.8P800 21.8500 P1000 18.3600 P1200 15.3800 P2400 8.41200 P4000D3.0AANSI - American National Standards InstituteBCAMI - Coated Abrasives Manufacturers InstituteCFEPA - Federation of European Abrasive Produc

35、ersDNot a FEPA designationE768 99 (2018)25.2.6 Polish the specimens using 3-m diamond abrasive ona low nap cloth, such as woven wool, for 50 s. Clean and drythe specimens as described in 5.2.5.5.2.7 Polish the specimens using a 1-m diamond abrasiveon a high nap cloth for 50 s. Clean and dry the spec

36、imens asdescribed in 5.2.5.5.2.8 A final manual polishing step may be added, using0.25-m diamond abrasive on a low nap cloth for 10 to 20 s,using relatively high pressure. Clean and dry the specimens asdescribed in 5.2.5.5.2.8.1 Ultrasonic cleaning is not recommended after thefinal manual or automat

37、ic polishing step. Ultrasonic cleaningcan cause cavitation damage, ultimately distorting the inclu-sion sizes.NOTE 3Depending on the material, it may be advisable to avoid waterafter polishing.5.3 Rigid Grinding Disk Procedure:5.3.1 Asummary of the rigid grinding disk procedure can befound in Table

38、3.5.3.2 Semi-automatic grinding equipment is required, withspecimens contained in a circular fixture for the entire proce-dure. For 5.3.2 5.3.5, a pressure of 42 kPa should be appliedper specimen. (For a specimen holder containing six 32-mmcircular mounts, a force of approximately 203 N must beappli

39、ed (see X1.4.3).5.3.3 Grind for at least 15 s after achieving a co-planarcondition, using a 150-grit alumina grinding stone at 1450 rpmor 80-grit (P80 FEPA) alumina/zirconia grinding paper at 300rpm.5.3.3.1 An adequate flow of water should remove all loos-ened abrasive and grinding debris from the p

40、aper during thegrinding procedure. The flow of water should ensure thespecimen is kept cool during grinding.TABLE 2 Preparation Method I Silicon Carbide Abrasive Paper GrindingSurface Coolent/LubricantAbrasive Size/TypeANSIAFEPABTime(seconds)ForceCnewtons lbsSurfaceSpeedRPMRelative RotationPlanar Gr

41、indingPaper Water 80 P80 grit SIC 60 14 2 300 ComplementaryDFine GrindingPaper Water 120 P120 grit SIC 14 2 300 ComplementaryPaper Water 240 P240 grit SIC 60 14 2 300 ComplementaryPaper Water 320 P500 grit SIC 60 14 2 300 ComplimentaryPaper Water 400 P600 grit SIC 60 14 2 300 ComplementaryPaper Wate

42、r 600 P1200 grit SIC 60 14 2 300 ComplimentaryPaper Water 800P2400 grit SIC 60 14 2 300 ComplementaryRough PolishingNAP free cloth Extending fluid 3 m diamond 50 14 2 150 ComplementaryFinal PolishingLow nap cloth Extending fluid 1 m diamond 50 14 2 150 ComplementaryOptional Polishing (manual)Low nap

43、 cloth Extending fluid 1 m diamond 50 relatively high NA NAEAAmerican National Standards Institute (ANSI) designation of grit size.BFederation of European Producers of Abrasives (FEPA) designation of grit size.CForce per 3-mm (1.25-in.) diameter specimen.DComplementary rotation, surface and specimen

44、s spin in same direction.ESince this optional step is completed manually, these two categories are not applicable.TABLE 3 Preparation Method II - Rigid Grinding Disk ProcedureSurface Coolant/LubricantAbrasive Size/Type ANSIAFEPABTime - seconds ForceCnewtons lbsSurface SpeedRPMRelative RotationPlanar

45、 GrindingAlumina/zirconia paper Water 80 P80 grit 15 34 8 300 ComplementaryDOrAlumina grinding stone Water 150 P150 grit 15 34 8 1450 ComplementaryFine GrindingRigid grinding disk Alcohol/glycol 9 m diamond 180 34 8 150 ComplementaryRough PolishingNapless or stiff napped cloth Alcohol/glycol 3 m dia

46、mond 240 34 8 150 ComplementaryFinal PolishingSoft short napped cloth Alcohol/glycol 1 m diamond 120 34 8 150 ComplementaryOptional PolishingPorous Synthetic Cloth Water Alkaline Colloidal Silica orAcidic Colloidal AluminaE90 100 23 150 ComplementaryAAmerican National Standards Institute (ANSI) desi

47、gnation of grit size.BFederation of European Producers of Abrasives (FEPA) designation of grit size.CForce per 32-mm (1.25-in.) diameter specimen.DComplementary rotation surface, and specimens spin in same direction.EWater is substituted for the colloidal oxide during the last 20 s.E768 99 (2018)35.

48、3.3.2 It may be necessary to clean the samples betweenevery grinding step to prevent contamination of the nextpreparation step.5.3.4 Finish grind using 9-m diamond on a rigid grindingdisk for3mat150rpm, using an alcohol/glycol lubricant.Clean the specimens and fixture thoroughly (ultrasonic clean-in

49、g is helpful) with alcohol and cotton, then dry with forced air.5.3.4.1 The use of a soap and water solution in an ultrasoniccleaner can attack non-metallic inclusions in some carbon andlow alloy steels, leading to an exaggeration in the inclusionsapparent size. Adding an inhibitor (such as that used as amachining coolant) may reduce this size exaggeration.5.3.5 Rough polish using 3-m diamond on a napless cloth(silk or non-woven chemotextile) or a low nap cloth (wovenwool) for 4 min at 150 rpm using