1、Designation: B 796 02Standard Test Method forNonmetallic Inclusion Content of Powders Intended forPowder Forging (P/F) Applications1This standard is issued under the fixed designation B 796; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a metallographic method fordetermining the nonmetallic inclusion level of
3、 powders in-tended for powder forging (P/F) applications.1.2 The test method covers repress powder forged testspecimens in which there has been minimal lateral materialflow ( 1%). The core region of the powder forged testspecimen shall contain no porosity detectable at 1003.1.3 This test method is n
4、ot suitable for determining thenonmetallic inclusion level of powder forged test specimensthat have been forged such that the core region containsporosity. At the magnification used for this test method residualporosity is hard to distinguish from oxide inclusions. Too muchresidual porosity makes a
5、meaningful assessment of the inclu-sion population impossible.1.4 The test method may be applied to materials that containmanganese sulfide (admixed or prealloyed) provided the nearneighbor separation distance is changed from 30 m to 15 m.NOTE 1The test method may be applied to powder forged parts w
6、herethere has been a greater amount of material flow provided:The near neighbor separation distance is changed, orThe inclusion sizes agreed between the parties are adjusted for theamount of material flow.1.5 This standard does not purport to address all of thesafety concerns, if any, associated wit
7、h 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:E 3 Practice for Preparation of Metallographic Specimens2E 768 Guide
8、 for Preparing and Evaluating Specimens forAutomatic Inclusion Assessment of Steel23. Summary of Test Method3.1 A section representing the core region is cut from thepowder forged test specimen and mounted for metallographicgrinding and polishing.3.2 The polished sample is examined microscopically a
9、t amagnification of 1003 and a note made of inclusions largerthan a predetermined size.3.3 The maximum Ferets diameter is used to determineinclusion size. A Ferets diameter is a caliper diameter asillustrated in Fig. 1.3.4 The fragmented nature of some inclusions means thattheir size determination i
10、s somewhat complicated. The conceptof near neighbor separation is used in determining inclusionsize. If an inclusion is within a certain distance of its neigh-boring particles, it is considered a member of an inclusioncluster or agglomerate. Detected features within 30 m of oneanother are considered
11、 part of the same inclusion. The conceptis illustrated schematically in Fig. 2.3.5 The nonmetallic inclusion level of the test specimen isreported as the number of inclusions per 100 mm2greater thanor equal to the predetermined size.4. Significance and Use4.1 The extensive porosity present in presse
12、d and sinteredferrous materials masks the effect of inclusions on mechanicalproperties. In contrast, the properties of material powder forgedto near full density are strongly influenced by the composition,size, size distribution, and location of nonmetallic inclusions.4.2 The test for nonmetallic in
13、clusions in powder forgedsteels is useful as the following:4.2.1 Characteristic to classify or differentiate one grade ofpowder from another.4.2.2 Means of quality comparison of powders intended forpowder forging, lot to lot.4.3 Significant variations in nonmetallic inclusion contentwill occur if:4.
14、3.1 The powder used to form the test specimen does notmeet powder forging quality standards for nonmetallic inclu-sion content.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.11 on Near
15、Full Density Powder Metallurgy Parts.Current edition approved April 10, 2002. Published May 2002. Originallypublished as B 88. Last previous edition B 00.2Annual Book of ASTM Standards, Vol 03.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Uni
16、ted States.4.3.2 Processing of the powder forged test specimen hasbeen carried out under conditions that do not permit oxidereduction or allow oxidation of the test specimen, or both.5. Apparatus5.1 Equipment for the metallographic preparation of testspecimens.5.2 A metallographic microscope permitt
17、ing observationand measurement up to a magnification of 1003 using lightwith a wavelength of 544 nm (green filter), an objective lenswith a magnification of from 83 to 12.53, and a numericalaperture between 0.16 and 0.20.NOTE 2Defining the light optics used is important because thisdetermines the fe
18、atures that will be resolved, and all detected features areincluded in the assessment of inclusion size.6. Sampling6.1 A metallographic sample shall be removed from thepowder forged test specimen, austenitized, and quenched.6.2 The polished surface of the sample to be examined shallbe not less than
19、350 mm2(0.54 in.2) in area. Multiple sectionsare permitted in order to obtain the necessary area for mea-surement.6.3 The polished surface shall be parallel to the direction offorging, that is, parallel to the direction of travel of the forgingpunch, and shall represent the core region of the test s
20、pecimen.7. Procedure7.1 Preparation of SpecimensIn polishing the specimens,it is highly important that a clean polish be obtained and thatthe inclusions not be pitted, dragged, or obscured. It isrecommended that the procedures described in Practice E 3 andGuide E 768 be followed. Automated grinding
21、and polishingprocedures are recommended. Examine specimens in theas-polished condition, free of the effects of any prior etching,if used.7.2 Measurement of Nonmetallic Inclusion Content:7.2.1 Survey at least 350 mm2(0.54 in2) of the surface of thepolished specimen at a magnification of 1003 using li
22、ght witha wavelength of 544 nm (green filter), an objective lens with amagnification of from 83 to 12.53, and a numerical aperturebetween 0.16 and 0.20.7.2.2 Size detected inclusions on the basis of near neighborseparation. Features within 30 m of one another are consid-ered to be part of the same i
23、nclusion.7.2.3 For individual features less than 30 m in size, threesuch features within 30 m of one another are required toconstitute an inclusion aggregate.7.2.4 Add an individual feature less than 30 m in size to aninclusion larger than 30 m, provided both features are within30 m of one another.
24、Examples are given in Figs. 3 and 4.7.2.5 Measure and record the number of inclusion particlesaccording to the principle of near neighbor separation and sizedusing the maximum Ferets diameter that are as follows:7.2.5.1 Greater than or equal to 30 m but less than 100 min length,7.2.5.2 Greater than
25、or equal to 100 m but less than 150 min length, and7.2.5.3 Greater than or equal to 150 m in length.8. Report8.1 Report the number of nonmetallic inclusions per100 mm2that are as follows:8.1.1 Greater than or equal to 30 m but less than 100 m inlength.8.1.2 Greater than or equal to 100 m but less th
26、an 150 min length.8.1.3 Greater than or equal to 150 m in length.8.2 The total area examined.FIG. 1 Schematic illustration of Ferets diameter.FIG. 2 Schematic illustration of the “near neighbor” concept andmaximum Ferets diameter.FIG. 3 Example of a spotty oxide inclusion. The maximum Feretsdiameter
27、 is indicated.B 79629. Precision and Bias9.1 The precision and bias that can be expected through theuse of this test method is currently under review by Subcom-mittee B09.11.10. Keywords10.1 nonmetallic inclusions; powder forged (P/F) steel partsASTM International takes no position respecting the va
28、lidity of any patent rights asserted in connection with any item mentionedin 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 su
29、bject to revision at any time by the responsible technical committee and must 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 Headqu
30、arters. Your comments will receive careful consideration at a meeting of theresponsible 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 stand
31、ard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, 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).FIG. 4 Example of a discontinuous sulphide inclusion. Themaximum Ferets diameter is indicated.B 7963
