ASTM B796-20
(Test Method)Standard Test Method for Nonmetallic Inclusion Content of Ferrous Powders Intended for Powder Forging (PF) Applications
Standard Test Method for Nonmetallic Inclusion Content of Ferrous Powders Intended for Powder Forging (PF) Applications
SIGNIFICANCE AND USE
4.1 The extensive porosity present in pressed and sintered ferrous materials masks the effect of inclusions on mechanical properties. In contrast, the properties of material powder forged 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 forged steels is useful as the following:
4.2.1 Characteristic to classify or differentiate one grade of powder from another.
4.2.2 Means of quality comparison of powders intended for powder forging, lot to lot.
4.3 Significant variations in nonmetallic inclusion content will occur if:
4.3.1 The powder used to form the test specimen does not meet powder forging quality standards for nonmetallic inclusion content.
4.3.2 Processing of the powder forged test specimen has been carried out under conditions that do not permit oxide reduction or allow oxidation of the test specimen, or both.
SCOPE
1.1 This test method covers a metallographic method for determining the nonmetallic inclusion level of ferrous powders intended for powder forging (PF) applications.
1.2 The test method covers repress powder forged test specimens in which there has been minimal lateral material flow (
1.3 This test method is not suitable for determining the nonmetallic inclusion level of powder forged test specimens that have been forged such that the core region contains porosity. At the magnification used for this test method, residual porosity is hard to distinguish from oxide inclusions. Too much residual porosity makes a meaningful assessment of the inclusion population impossible.
1.4 The test method may be applied to materials that contain manganese sulfide (admixed or prealloyed), provided the near neighbor separation distance is changed from 30 μm to 15 μm.
Note 1: The test method may be applied to powder forged parts where there has been a greater amount of material flow provided:
The near neighbor separation distance is changed, or
The inclusion sizes agreed between the parties are adjusted for the amount of material flow.
1.5 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B796 − 20
Standard Test Method for
Nonmetallic Inclusion Content of Ferrous Powders Intended
1
for Powder Forging (PF) Applications
This standard is issued under the fixed designation B796; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This test method covers a metallographic method for
determiningthenonmetallicinclusionlevelofferrouspowders
2. Referenced Documents
intended for powder forging (PF) applications.
2
2.1 ASTM Standards:
1.2 The test method covers repress powder forged test
E3Guide for Preparation of Metallographic Specimens
specimens in which there has been minimal lateral material
E768Guide for Preparing and Evaluating Specimens for
flow (<1%). The core region of the powder forged test
Automatic Inclusion Assessment of Steel
specimen shall contain no porosity detectable at 100×.
3. Summary of Test Method
1.3 This test method is not suitable for determining the
nonmetallic inclusion level of powder forged test specimens
3.1 A section representing the core region is cut from the
that have been forged such that the core region contains
powder forged test specimen, parallel to the direction of
porosity. At the magnification used for this test method,
forging, to obtain a rectangular section that is mounted for
residual porosity is hard to distinguish from oxide inclusions.
metallographic grinding and polishing.
Too much residual porosity makes a meaningful assessment of
3.2 The polished sample is examined microscopically at a
the inclusion population impossible.
magnification of 100× and a note made of inclusions larger
1.4 Thetestmethodmaybeappliedtomaterialsthatcontain
than a predetermined size.
manganese sulfide (admixed or prealloyed), provided the near
3.3 The maximum Feret’s diameter is used to determine
neighbor separation distance is changed from 30 µm to 15 µm.
inclusion size. A Feret’s diameter is a caliper diameter as
NOTE1—Thetestmethodmaybeappliedtopowderforgedpartswhere
illustrated in Fig. 1.
there has been a greater amount of material flow provided:
3.4 The fragmented nature of some inclusions means that
The near neighbor separation distance is changed, or
The inclusion sizes agreed between the parties are adjusted for the
theirsizedeterminationissomewhatcomplicated.Theconcept
amount of material flow.
of near neighbor separation is used in determining inclusion
size. If an inclusion is within a certain distance of its neigh-
1.5 Units—The values stated in SI units are to be regarded
asstandard.Nootherunitsofmeasurementareincludedinthis boring particles, it is considered a member of an inclusion
cluster or agglomerate. Detected features within 30 µm of one
standard.
another are considered part of the same inclusion.The concept
1.6 This standard does not purport to address all of the
is illustrated schematically in Fig. 2.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.5 The nonmetallic inclusion level of the test specimen is
2
priate safety, health, and environmental practices and deter- reported as the number of inclusions per 100 mm greater than
mine the applicability of regulatory limitations prior to use.
or equal to the predetermined size.
1.7 This international standard was developed in accor-
4. Significance and Use
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
4.1 The extensive porosity present in pressed and sintered
Development of International Standards, Guides and Recom-
ferrous materials masks the effect of inclusions on mechanical
properties.Incontrast,thepropertiesofmaterialpowderforged
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal
Powders and Metal Powder Products and is the direct responsibility of Subcom-
2
mittee B09.11 on Near Full Density Powder Metallurgy Materials. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2020. Published June 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1988. Last previous edition approved in 2014 as B796–14. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/B0796-20. the ASTM website.
*A Summary of Changes section appears at t
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B796 − 14 B796 − 20
Standard Test Method for
Nonmetallic Inclusion Content of Ferrous Powders Intended
1
for Powder Forging (PF) Applications
This standard is issued under the fixed designation B796; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method covers a metallographic method for determining the nonmetallic inclusion level of ferrous powders
intended for powder forging (PF) applications.
1.2 The test method covers repress powder forged test specimens in which there has been minimal lateral material flow
(< 1%).(< 1 %). The core region of the powder forged test specimen shall contain no porosity detectable at 100×.
1.3 This test method is not suitable for determining the nonmetallic inclusion level of powder forged test specimens that have
been forged such that the core region contains porosity. At the magnification used for this test method, residual porosity is hard
to distinguish from oxide inclusions. Too much residual porosity makes a meaningful assessment of the inclusion population
impossible.
1.4 The test method may be applied to materials that contain manganese sulfide (admixed or prealloyed)prealloyed), provided
the near neighbor separation distance is changed from 30 μm to 15 μm.
NOTE 1—The test method may be applied to powder forged parts where there has been a greater amount of material flow provided:
The near neighbor separation distance is changed, or
The inclusion sizes agreed between the parties are adjusted for the amount of material flow.
1.5 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
E3 Guide for Preparation of Metallographic Specimens
E768 Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel
3. Summary of Test Method
3.1 A section representing the core region is cut from the powder forged test specimen, parallel to the direction of forging, to
obtain a rectangular section that is mounted for metallographic grinding and polishing.
3.2 The polished sample is examined microscopically at a magnification of 100× and a note made of inclusions larger than a
predetermined size.
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility of Subcommittee B09.11
on Near Full Density Powder Metallurgy Materials.
Current edition approved Sept. 1, 2014April 1, 2020. Published October 2014June 2020. Originally approved in 1988. Last previous edition approved in 20022014 as
B796 – 07.B796 – 14. DOI: 10.1520/B0796-14.10.1520/B0796-20.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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B796 − 20
3.3 The maximum Feret’s diameter is used to determine inclusion size. A Feret’s diameter is a caliper diameter as illustrated
in Fig. 1.
3.4 The fragmented nature of some inclusions means that their size determination is somewhat complicated. The concept of near
neighbor separation is used in determining inclusion size. If an inclusion is within a certain distance of its neighboring particles,
it is considered a member of an inclusion cluster or agglomerate. Detected features within 30 μm of
...
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