ASTM B796-02
(Test Method)Standard Test Method for Nonmetallic Inclusion Content of Powders Intended for Powder Forging (P/F) Applications
Standard Test Method for Nonmetallic Inclusion Content of Powders Intended for Powder Forging (P/F) Applications
SIGNIFICANCE AND USE
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.
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.
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 powders intended for powder forging (P/F) 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 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: B 796 – 02
Standard Test Method for
Nonmetallic Inclusion Content of Powders Intended for
1
Powder Forging (P/F) Applications
This standard is issued under the fixed designation B 796; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Summary of Test Method
1.1 This test method covers a metallographic method for 3.1 A section representing the core region is cut from the
determining the nonmetallic inclusion level of powders in- powder forged test specimen and mounted for metallographic
tended for powder forging (P/F) applications. grinding and polishing.
1.2 The test method covers repress powder forged test 3.2 The polished sample is examined microscopically at a
specimens in which there has been minimal lateral material magnification of 1003 and a note made of inclusions larger
flow (< 1%). The core region of the powder forged test than a predetermined size.
specimen shall contain no porosity detectable at 1003. 3.3 The maximum Feret’s diameter is used to determine
1.3 This test method is not suitable for determining the inclusion size. A Feret’s diameter is a caliper diameter as
nonmetallic inclusion level of powder forged test specimens illustrated in Fig. 1.
that have been forged such that the core region contains 3.4 The fragmented nature of some inclusions means that
porosity.At the magnification used for this test method residual their size determination is somewhat complicated. The concept
porosity is hard to distinguish from oxide inclusions.Too much of near neighbor separation is used in determining inclusion
residual porosity makes a meaningful assessment of the inclu- size. If an inclusion is within a certain distance of its neigh-
sion population impossible. boring particles, it is considered a member of an inclusion
1.4 Thetestmethodmaybeappliedtomaterialsthatcontain cluster or agglomerate. Detected features within 30 µm of one
manganese sulfide (admixed or prealloyed) provided the near another are considered part of the same inclusion. The concept
neighbor separation distance is changed from 30 µm to 15 µm. is illustrated schematically in Fig. 2.
3.5 The nonmetallic inclusion level of the test specimen is
NOTE 1—The test method may be applied to powder forged parts where
2
reported as the number of inclusions per 100 mm greater than
there has been a greater amount of material flow provided:
or equal to the predetermined size.
The near neighbor separation distance is changed, or
The inclusion sizes agreed between the parties are adjusted for the
4. Significance and Use
amount of material flow.
4.1 The extensive porosity present in pressed and sintered
1.5 This standard does not purport to address all of the
ferrous materials masks the effect of inclusions on mechanical
safety concerns, if any, associated with its use. It is the
properties.Incontrast,thepropertiesofmaterialpowderforged
responsibility of the user of this standard to establish appro-
to near full density are strongly influenced by the composition,
priate safety and health practices and determine the applica-
size, size distribution, and location of nonmetallic inclusions.
bility of regulatory limitations prior to use.
4.2 The test for nonmetallic inclusions in powder forged
2. Referenced Documents steels is useful as the following:
4.2.1 Characteristic to classify or differentiate one grade of
2.1 ASTM Standards:
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powder from another.
E 3 Practice for Preparation of Metallographic Specimens
4.2.2 Means of quality comparison of powders intended for
E 768 Guide for Preparing and Evaluating Specimens for
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powder forging, lot to lot.
Automatic Inclusion Assessment of Steel
4.3 Significant variations in nonmetallic inclusion content
will occur if:
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This test method is under the jurisdiction of ASTM Committee B09 on Metal
4.3.1 The powder used to form the test specimen does not
Powders and Metal Powder Products and is the direct responsibility of Subcom-
meet powder forging quality standards for nonmetallic inclu-
mittee B09.11 on Near Full Density Powder Metallurgy Parts.
sion content.
Current edition approved April 10, 2002. Published May 2002. Originally
published as B – 88. Last previous edition B – 00.
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Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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B 796
7. Procedure
7.1 Preparation of Specimens—In polishing the specimens,
it is highly important that a clean polish be obtained and that
the inclusions not be pitted, dragged, or obscure
...
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