ASTM_B_796_-_14.pdf

Designation:B79614Standard Test Method forNonmetallic Inclusion Content of Ferrous Powders Intendedfor Powder Forging(PF)Applications1This standard is issued under the fixed designation B796;the number immediately following the designation indicates the year oforiginal adoption or,in the 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.Scope*1.1 This test method covers a metallographic method fordetermining the nonmetallic inclusion level of ferrous powdersintended for powder forging(PF)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 100.1.3 This test method is not 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 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.NOTE1The test method may be applied to powder forged parts wherethere 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 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 This standard does 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 Standards:2E3 Guide for Preparation of Metallographic SpecimensE768 Guide for Preparing and Evaluating Specimens forAutomatic Inclusion Assessment of Steel3.Summary of Test Method3.1 A section representing the core region is cut from thepowder forged test specimen,parallel to the direction offorging,to obtain a rectangular section that is mounted formetallographic grinding and polishing.3.2 The polished sample is examined microscopically at amagnification of 100 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 is 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 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 pressed and sinteredferrous materials masks the effect of inclusions on mechanicalproperties.In contrast,the properties of material powder forged1This 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 Full Density Powder Metallurgy Materials.Current edition approved Sept.1,2014.Published October 2014.Originallyapproved in 1988.Last previous edition approved in 2002 as B796 07.DOI:10.1520/B0796-14.2For 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 Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 to near full density are strongly influenced by the composition,size,size distribution,and location of nonmetallic inclusions.4.2 The test for nonmetallic inclusions 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:4.3.1 The powder used to form the test specimen does notmeet powder forging quality standards for nonmetallic inclu-sion content.4.3.2 Processing of the powder forged