1、Designation: E 2142 08Standard Test Methods forRating and Classifying Inclusions in Steel Using theScanning Electron Microscope1This standard is issued under the fixed designation E 2142; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, 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 classification, and
3、Test MethodsE45ratings of inclusions in steels using an automated scan-ning electron microscope (SEM) with X-ray analysis andautomatic image analysis capabilities.1.2 There are three discrete methods described. Method 1 isthe SEM analog of Test Method E45, which uses imageanalysis and light microsco
4、py to produce automated TestMethods E45ratings. 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 necessarily defined
5、 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 MethodsE45type ratings.1.3 This test method deals only with the recommended testmethods and nothing in it s
6、hould 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 does not purport to
7、 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 Standards:2E3 Guide
8、for Preparation of Metallographic SpecimensE7 Terminology Relating to MetallographyE45 Test Methods for Determining the Inclusion Contentof SteelE 766 Practice for Calibrating the Magnification of a Scan-ning Electron MicroscopeE 768 Guide for Preparing and Evaluating Specimens forAutomatic Inclusio
9、n Assessment of SteelE 1245 Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic ImageAnalysisE 1508 Guide for Quantitative Analysis by Energy-Dispersive Spectroscopy2.2 Adjuncts:ANSI/IEEE STD 759 IEEE Standard Test Procedure forSemiconductor X-Ray Energy
10、 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 both), the l
11、ist 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 intensities or el
12、emental compositions required to identifyan 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
13、inclusions are placed according to the analysisrules. Categories may be broad (for example, sulfide, alumi-nate, silicate) or more precise (for example, calcium sulfide,calcium silicate, anorthite, etc.).1These test methods are under the jurisdiction of ASTM Committee E04 onMetallography and are the
14、 direct responsibility of Subcommittee E04.11 on X-Rayand Electron Metallography.Current edition approved Oct. 1, 2008. Published October 2008. Originallyapproved in 2001. Last previous edition approved in 2001 as E214201.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontac
15、t ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document 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
16、:/www.ieee.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.3 critical aspect ratiothe aspect ratio of a singleinclusion that defines the boundary between “globular” and“elongated”.3.2.4 discontinuous stringertwo or more Type
17、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 Rating Levelsfor Measurements in Mic
18、rometers (For expression in other units,see Test Methods E45, Table 2)Test Method E45Rating Limits (m at 13 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 92.5 649.0 554.7 510.3 163.0 898.0 822.2 746.1 253.5 1181.0 1147.0 1029.0 364.0 1
19、498.0 1530.0 1359.0 494.5 1898.0 1973.0 1737.0 815.0 2230.0 2476.0 2163.0 100E21420849.3 Inclusion retention is generally easier to accomplish inspecimens that are hardened rather than in annealed condition.If inclusion retention is inadequate in annealed specimens, theyshould be subjected to a stan
20、dard heat treatment cycle using arelatively low tempering temperature. After heat treatment, thespecimen must be descaled and the longitudinal plane must bereground below any decarburization. This recommendationonly applies to heat-treatable steel grades.9.4 Mounting of specimens is not required if
21、unmountedspecimens can be properly polished.9.5 Polishing practice should follow Practice E 768.10. Calibration and Standardization10.1 The SEM magnification should be calibrated accordingto E 766. It is important to calibrate the magnification of theSEM to obtain accurate E 45 ratings and to ensure
22、 that analysistime is minimized. The number of particles of a given sizeincreases strongly as size decreases; if particles below thedesired low size limit are included due to magnification error,the number of spectra collected, and therefore the total analysistime, will increase significantly.10.2 T
23、he EDX energy calibration should be done accordingto section 8.1 of E 1508.10.3 The EDX energy resolution should be checked peri-odically. The energy resolution, defined as the Full Width atHalf Maximum (FWHM) height of the Mn Ka X-ray line, afterbackground has been subtracted, should be measured ac
24、cord-ing to the practice suggested by the manufacturer, provided thatit is in accordance with the IEEE methodology.11. Procedure11.1 Prepare specimens following the standard protocol setforth in Practice E 768.At this time, a small piece of aluminumtape or other reference material may be placed on t
25、he 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 stability.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 appropriat
26、ely for theelemental range of interest, bearing in mind that excessivevoltage will give rise to an (unwanted) increase in matrixcontribution to the spectrum. Use of 1015 kV is typical,although slightly lower or higher voltages may be appropriatedepending on the particular application. Use the micros
27、copemanufacturers procedures for saturating the filament, aligningthe column and setting other parameters to optimize imagequality.11.4 Calibrate the X-ray analyzer such that the collectedspectrum will include all the elements of interest; 010 keV isrecommended. If there are X rays of interest above
28、 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 currenthas previously been determined. Alternatively, the current canbe set by moving the aluminum tape under the beam andrecording X-ray counts. P
29、robe current (or “spot size”, which isproportional to probe current) is adjusted until approximately40 % dead time, if possible, is achieved. The steel matrix 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 thedesc
30、ribed 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 number. The matrix, which consistsprimarily of iron, will be brighter than some inclusions (forexample, MnS) and darker than other inclusions (fo
31、r example,Pb). Since inclusions are discriminated by the BSE gray level,the threshold(s) must be set appropriately using the procedurerecommended by the manufacturer.11.7 Select and store the region of the sample to beexamined following the stage control manufacturers recom-mended procedure. The reg
32、ion 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 mm2wholly contained within the user-selected region to analyze. InMethod 3 of this Test Method, analysis can be based on thenumber of inclusions detected
33、 rather than sample area.11.8 As the beam rasters the selected region, the softwarerecognizes features that fall within the previously defined rangeof gray-levels. Morphological and chemical parameters areimmediately calculated and stored or, alternatively, raw data isstored for off-line processing.
34、11.8.1 In Test Method E45inclusions are examined usingfield areas of 0.50 mm2and magnifications of 1003. Theinclusions can be examined and discriminated by type usingmagnifications other than 1003 and field areas other than 0.50mm2as long as the severity ratings (see Section 12) are basedon the requ
35、ired 0.50 mm2field area.11.9 Define the Analysis Rules:11.9.1 The EDX acquisition should continue until sufficientstatistics are accumulated to classify the inclusion. For adiscussion on X-ray counting and chemical classificationstatistics, see Appendix X2 and standard text books.4Theminimum number
36、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 the
37、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 Defin
38、e 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) ele
39、men-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.4Goldstein, et al, Scanning Electron Microscopy and X-Ray Microanalysis, 2nded, Pl
40、enum Publishing Corporation, New York, NY, 1992 , pp 493-505.E214208511.10 Set the relevant imaging parameters such as themagnification(s) to be used, the minimum and maximumparticle sizes to be recorded, and the critical aspect ratiodefining an elongated inclusion (see 11.14). Appendix X1provides a
41、 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 adequate numberof pixels in each inclusion for the computer program toaccurately make measurements. In order to detecta2mparticle, the step size of the el
42、ectron probe, which is in fact thepixel size, must be at most 2 m. If a 256 3 256 image isdisplayed on a 10 cm screen, the field of view is 512 m wide,and the magnification is 195.3 3 (magnification = 10/0.0512).However, to accurately measure the size ofa2mparticle towithin, say, 10%, a step size of
43、 0.2 m would be dictated,corresponding to a magnification of 19533 . Depending uponthe inclusion analysis software, such pixel size and magnifica-tion may be selected automatically, based on the minimuminclusion size of interest input by the user. In the examplegiven, a magnification of 195.33 could
44、 be used to search forinclusions; once detected, the magnification is automaticallyincreased to 19533 to measure the inclusion dimensions. Theinclusion analysis software must include this or an equivalentanalysis strategy to provide the required accuracy.11.11 Start the analysis, which will run unat
45、tended in acompletely automated system.11.12 Ratings similar to E45 ratings will be determinedautomatically within Methods 1 and 2 of this Test Method.Inclusions will be classified according to type (or chemistry),morphology and thickness. Since ratings using light micros-copy may differ from those
46、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 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-
47、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, ar
48、elatively high AR of 2 is used in order to more reliablydifferentiate silicates, which are generally highly elongated,from aluminates, which are less elongated. In this Test Method,the X-ray spectrum from the inclusion is directly obtained andwill serve to differentiate aluminates from silicates, re
49、ducingthe dependence on morphology. In Method 2, used for“chemistry-based” E45 ratings, and Method 3, used forcustom analyses, a criticalAR of 2 is suggested for consistencywith E45, but other values of AR may be used. Inclusionanalysis software must allow the critical AR to be selectable asan Analysis Rule, with default settings as described above.11.15 In Method 3, the analysis will automatically terminatewhen a minimum number of inclusions has been classified (forexample, 1000) or when a specified area of the sample has beenexamined (For example, 160 mm2), whic
