1、Designation: E2142 08 (Reapproved 2015)Standard Test Methods forRating and Classifying Inclusions in Steel Using theScanning Electron Microscope1This standard is issued under the fixed designation E2142; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he 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.1. Scope1.1 This test method covers procedures to obtain particlesize distribution, chemical clas
3、sification, and Test MethodsE45 ratings of inclusions in steels using an automated scanningelectron microscope (SEM) with X-ray analysis and automaticimage analysis capabilities.1.2 There are three discrete methods described. Method 1 isthe SEM analog of Test Method E45, which uses imageanalysis and
4、 light microscopy to produce automated TestMethods E45 ratings. Method 2 produces similar ratings basedpredominantly on sorting inclusions by chemistry into thetraditional classes defined in Test Methods E45. Method 3 isrecommended when explicit detail is needed on particularinclusion types, not nec
5、essarily defined in Test Methods E45,such as to verify the composition of inclusions in inclusion-engineered steel. Method 3 reports stereological parameterssuch as volume or number fraction, rather than Test MethodsE45 type ratings.1.3 This test method deals only with the recommended testmethods an
6、d nothing in it should be construed as defining orestablishing limits of acceptability for any grade of steel orother alloy where the method is appropriate.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 do
7、es 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 Sta
8、ndards:2E3 Guide for Preparation of Metallographic SpecimensE7 Terminology Relating to MetallographyE45 Test Methods for Determining the Inclusion Content ofSteelE766 Practice for Calibrating the Magnification of a Scan-ning Electron MicroscopeE768 Guide for Preparing and Evaluating Specimens forAut
9、omatic Inclusion Assessment of SteelE1245 Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic ImageAnalysisE1508 Guide for Quantitative Analysis by Energy-Dispersive Spectroscopy2.2 Adjuncts:ANSI/IEEE STD 759 IEEE Standard Test Procedure forSemiconductor
10、 X-Ray Energy Spectrometers33. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, see Terminology E7.3.2 Definitions of Terms Specific to This Standard:3.2.1 Analysis Rules3.2.1.1 acquisition analysis rulesinclude the criteria toterminate X-ray collection (counts or time, or
11、 both), the list ofelements to be analyzed, the number of fields or particles to beanalyzed, morphologies of particles from which spectra will becollected, etc. (see Appendix X1 for a more complete listing oftypical Acquisition Rules).3.2.1.2 post-acquisition analysis rulesdefine ratios ofX-ray inte
12、nsities or elemental compositions required to identify1These test methods are under the jurisdiction of ASTM Committee E04 onMetallography and are the direct responsibility of Subcommittee E04.11 on X-Rayand Electron Metallography.Current edition approved Oct. 1, 2015. Published November 2015. Origi
13、nallyapproved in 2001. Last previous edition approved in 2008 as E214208. DOI:10.1520/E2142-08R15.2For 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 Docu
14、ment Summary page onthe ASTM website.3Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE),445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http:/www.ieee.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United St
15、ates1an inclusion as belonging to a particular chemical classificationand, for Methods 1 and 2 herein, define the main inclusionclass (A, B, or C) to which each chemical classificationbelongs.3.2.2 chemical classificationdefined compositional cat-egories in which inclusions are placed according to t
16、he analysisrules. Categories may be broad (for example, sulfide,aluminate, silicate) or more precise (for example, calciumsulfide, calcium silicate, anorthite, etc.).3.2.3 critical aspect ratiothe aspect ratio of a singleinclusion that defines the boundary between “globular” and“elongated”.3.2.4 dis
17、continuous stringertwo or more Type C or threeor more Type B inclusions aligned in a plane parallel to the hotworking axis and offset from the stringer centerline by no morethan 15 m, with a separation of 4 12 12B $2 9 9 15 15C $2 5 5 12 12D $2 8 8 13 13TABLE 2 Minimum Values for Inclusion Severity
18、Rating Levelsfor Measurements in Micrometers (For expression in other units,see Test Methods E45, Table 2)Test Method E45 Rating Limits (m at 1 or count)Severity A B C D0.5 37.0 17.2 17.8 11.0 127.0 76.8 75.6 21.5 261.0 184.2 176.0 42.0 436.1 342.7 320.5 92.5 649.0 554.7 510.3 163.0 898.0 822.2 746.
19、1 253.5 1181.0 1147.0 1029.0 364.0 1498.0 1530.0 1359.0 494.5 1898.0 1973.0 1737.0 815.0 2230.0 2476.0 2163.0 100E2142 08 (2015)4area should be obtained so that the measurement may be madewithin the defined area away from the edges of the sample.9. Specimen Preparation9.1 Metallographic specimen pre
20、paration must be carefullycontrolled to produce acceptable quality surfaces for imageanalysis. Guidelines and recommendations are given inMethod E3 and Standards E45 and E768.9.2 Polishing must reveal the inclusions without interfer-ence from artifacts, foreign matter, or scratches, although theuse
21、of chemistry will minimize the errors associated with thesefeatures. Polishing must not alter the true appearance of theinclusions by excessive relief, pitting, and pull-out. Use ofautomatic grinding and polishing devices is recommended.9.3 Inclusion retention is generally easier to accomplish inspe
22、cimens that are hardened rather than in annealed condition.If inclusion retention is inadequate in annealed specimens, theyshould be subjected to a standard heat treatment cycle using arelatively low tempering temperature. After heat treatment, thespecimen must be descaled and the longitudinal plane
23、 must bereground below any decarburization. This recommendationonly applies to heat-treatable steel grades.9.4 Mounting of specimens is not required if unmountedspecimens can be properly polished.9.5 Polishing practice should follow Practice E768.10. Calibration and Standardization10.1 The SEM magni
24、fication should be calibrated accordingto E766. It is important to calibrate the magnification of theSEM to obtain accurate E45 ratings and to ensure that analysistime is minimized. The number of particles of a given sizeincreases strongly as size decreases; if particles below thedesired low size li
25、mit are included due to magnification error,the number of spectra collected, and therefore the total analysistime, will increase significantly.10.2 The EDX energy calibration should be done accordingto section 8.1 of E1508.10.3 The EDX energy resolution should be checked peri-odically. The energy re
26、solution, defined as the Full Width atHalf Maximum (FWHM) height of the Mn K X-ray line, afterbackground has been subtracted, should be measured accord-ing to the practice suggested by the manufacturer, provided thatit is in accordance with the IEEE methodology.11. Procedure11.1 Prepare specimens fo
27、llowing the standard protocol setforth in Practice E768.At this time, a small piece of aluminumtape or other reference material may be placed on the edge ofthe sample. The tape may later be used as a target in order todetermine the proper setting of the electron probe current or tocheck its stabilit
28、y.11.2 Position the sample in the SEM at a working distancethat is suitable for both BSE and EDX.11.3 Set the beam accelerating voltage appropriately for theelemental range of interest, bearing in mind that excessivevoltage will give rise to an (unwanted) increase in matrixcontribution to the spectr
29、um. Use of 1015 kV is typical,although slightly lower or higher voltages may be appropriatedepending on the particular application. Use the microscopemanufacturers procedures for saturating the filament, aligningthe column and setting other parameters to optimize imagequality.11.4 Calibrate the X-ra
30、y analyzer such that the collectedspectrum will include all the elements of interest; 010 keV isrecommended. If there are X rays of interest above 10 keV(such as Pb L lines), use 020 keV.11.5 Set electron probe current by direct measurement usinga pico-ammeter and Faraday cup, if the optimum probe c
31、urrenthas previously been determined. Alternatively, the current canbe set by moving the aluminum tape under the beam andrecording X-ray counts. Probe current (or “spot size”, which isproportional to probe current) is adjusted until approximately40 % dead time, if possible, is achieved. The steel ma
32、trix itselfmay be used as the basis of current setting in place of the tape,but this will likely result in the least consistent setting of thedescribed methods.11.6 Select the BSE imaging mode, which is used becausethe brightness of a feature in the BSE image is directly relatedto its average atomic
33、 number. The matrix, which consistsprimarily of iron, will be brighter than some inclusions (forexample, MnS) and darker than other inclusions (for example,Pb). Since inclusions are discriminated by the BSE gray level,the threshold(s) must be set appropriately using the procedurerecommended by the m
34、anufacturer.11.7 Select and store the region of the sample to beexamined following the stage control manufacturers recom-mended procedure. The region can be larger than but notsmaller than 160 mm2; if the sample region is larger, then thesoftware shall select a contiguous area of exactly 160 mm2whol
35、ly contained within the user-selected region to analyze. InMethod 3 of this Test Method, analysis can be based on thenumber of inclusions detected rather than sample area.11.8 As the beam rasters the selected region, the softwarerecognizes features that fall within the previously defined rangeof gra
36、y-levels. Morphological and chemical parameters areimmediately calculated and stored or, alternatively, raw data isstored for off-line processing.11.8.1 In Test Method E45 inclusions are examined usingfield areas of 0.50 mm2and magnifications of 100. Theinclusions can be examined and discriminated b
37、y type usingmagnifications other than 100 and field areas other than 0.50mm2as long as the severity ratings (see Section 12) are basedon the required 0.50 mm2field area.11.9 Define the Analysis Rules:11.9.1 The EDX acquisition should continue until sufficientstatistics are accumulated to classify th
38、e inclusion. For adiscussion on X-ray counting and chemical classificationstatistics, see Appendix X2 and standard text books.4The4Goldstein, et al, Scanning Electron Microscopy and X-Ray Microanalysis, 2nded, Plenum Publishing Corporation, New York, NY, 1992 , pp 493-505.E2142 08 (2015)5minimum num
39、ber of counts in a peak necessary for peakidentification must be entered.11.9.2 Define the relevant chemical classes and their analy-sis rules. In Method 2, for example, at least three chemicalclasses are defined: sulfides, aluminates, and silicates. Addi-tional classes may be defined, depending on
40、the application.For example, a “calcium silicate” class may be defined andincluded as Type B, as such inclusions appear similar to andhave the same detrimental effects as traditional Type Binclusions. Each chemical class and the main inclusion class towhich it is assigned should be reported.11.9.3 D
41、efine the measure of intensity in the X-ray spectrumwhich must be met in order to identify the particle as belongingto a certain classification. Each class should be defined in termsof one or more of the following: (1) peak intensity range, (2)peak to background ratio, (3) peak intensity ratios, (4)
42、 elemen-tal percentage as calculated by established methods, or (5)other chemical measurement(s) that characterizes a specifictype of inclusion.This choice is either narrowed or made by thesystem or software manufacturer.11.10 Set the relevant imaging parameters such as themagnification(s) to be use
43、d, the minimum and maximumparticle sizes to be recorded, and the critical aspect ratiodefining an elongated inclusion (see 11.14). Appendix X1provides a more complete list of analysis rules.11.10.1 For the selected magnification, digital imaging reso-lution should be chosen such that there are an ad
44、equate numberof pixels in each inclusion for the computer program toaccurately make measurements. In order to detecta2mparticle, the step size of the electron probe, which is in fact thepixel size, must be at most 2 m. If a 256 256 image isdisplayed on a 10 cm screen, the field of view is 512 m wide
45、,and the magnification is 195.3 (magnification = 10/0.0512).However, to accurately measure the size ofa2mparticle towithin, say, 10%, a step size of 0.2 m would be dictated,corresponding to a magnification of 1953 . Depending uponthe inclusion analysis software, such pixel size and magnifica-tion ma
46、y be selected automatically, based on the minimuminclusion size of interest input by the user. In the examplegiven, a magnification of 195.3 could be used to search forinclusions; once detected, the magnification is automaticallyincreased to 1953 to measure the inclusion dimensions. Theinclusion ana
47、lysis software must include this or an equivalentanalysis strategy to provide the required accuracy.11.11 Start the analysis, which will run unattended in acompletely automated system.11.12 Ratings similar to E45 ratings will be determinedautomatically within Methods 1 and 2 of this Test Method.Incl
48、usions will be classified according to type (or chemistry),morphology and thickness. Since ratings using light micros-copy may differ from those using the SEM, ratings resultingfrom application of this Test Method shall be called E45-SEM1, if method 1 is used, and E45-SEM2, if method 2 isused.11.13
49、The acquired raw data should be saved, unaltered bythe application of any analysis software. The raw data can thenbe used at a later time for re-classification of the inclusionsbased on different criteria.11.14 A critical parameter in the morphological character-ization of an inclusion is the Aspect Ratio (AR), at or abovewhich an inclusion is considered elongated. In Test MethodsE45, which relies on morphology to distinguish oxide types, arelatively high AR of 2 is used in order to more reliablydifferentiate silicates, which are generally highly elon
