1、Designation: B796 14Standard 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
2、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 lev
3、el 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 (350 mm 2 area required by the standard method. Thenumber of nonmetallic inclusions of the three specified sizes(Sect
4、ion 9) were determined and the results for the threemounts combined, divided by the total area examined, thenmultiplied by 100 to obtain the number per 100 mm2.10.1.2 As the values are not normally distributed, membersof Committee E11 helped with the analysis of the data. Theyapproached the task by
5、considering that the nonmetallicinclusion data might follow a Poisson rather than a normaldistribution. They indicated that as the data set is very small weshould expect considerable uncertainty in the stated results.The hypothesis cannot be rejected that the different inclusionsizes are occurring a
6、t different frequencies, and if the data arecombined into one set, the hypothesis cannot be rejected thatthe combined set has a homogeneous Poisson distribution. Fora Poisson distribution, the standard deviation is proportional tothe square root of the mean. (The mean is 0.667 inclusions per400 mm2o
7、r 0.167 per 100 mm2). The pooled standarddeviation of specimen repeatability is therefore approximately0.4.10.1.3 The reproducibility of this test method is beingdetermined and will be available on or before June 2019.10.2 BiasNo information can be presented on the bias ofthe procedure in Test Metho
8、d B796 for measuring nonmetallicinclusions because no material having an accepted referencevalue is available.10.3 Measurement UncertaintyThe precision of TestMethod B796 shall be considered by those performing the testwhen reporting nonmetallic inclusion test results.11. Keywords11.1 nonmetallic in
9、clusions; powder forged (PF) steel parts3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:B09-1022. ContactASTM CustomerService at serviceastm.org.FIG. 4 Example of a spotty oxide inclusion. The maximum Feretsdiameter is indicated
10、.FIG. 5 Example of a discontinuous sulphide inclusion. The maxi-mum Ferets diameter is indicated.B796 143SUMMARY OF CHANGESCommittee B09 has identified the location of selected changes to this standard since the last issue (B796-07)that may impact the use of this standard.(1) The word “ferrous” has
11、been added to the title.(2) A statement on units has been added in Section 1.(3) The direction for taking the section has been added toSection 3.(4) Reference to inch-pound units in parentheses has beendeleted from Section 7.2 and 8.2.1.(5) Reference to a new figure (Fig. 3) has been added inSection
12、 7.3 and Figures 3 and 4 were renumbered to Fig. 4 andFig. 5.(6) Section 10 on Precision and Bias has been revised and dataadded on the repeatability of the test method.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin
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