ASTM B925-15(2022)
(Practice)Standard Practices for Production and Preparation of Powder Metallurgy (PM) Test Specimens
Standard Practices for Production and Preparation of Powder Metallurgy (PM) Test Specimens
SIGNIFICANCE AND USE
5.1 Test specimens are used to determine the engineering properties of PM materials, for example, tensile strength, ductility, impact energy, etc.; property data that are essential to the successful use of PM material standards. Processing PM test specimens under production conditions is the most efficient method by which to obtain reliable PM material property data since in most cases it is impractical or impossible to cut test bars from sintered parts.
5.2 The performance characteristics of metal powders, for example, compressibility, green strength and dimensional changes associated with processing are evaluated using PM test specimens under controlled conditions. The data obtained are important to both metal powder producers and PM parts manufacturers.
5.3 PM test specimens play a significant role in industrial quality assurance programs. They are used to compare properties of a new lot of metal powder with an established lot in an acceptance test and are used in the part manufacturing process to establish and adjust production variables.
5.4 In those instances where it is required to present equivalent property data for a production lot of PM parts, standard test specimens compacted from the production powder mix to the same green density can be processed with the production PM parts and then tested to obtain this information.
5.5 Material property testing performed for industrial or academic research and development projects uses standard PM test specimens so the test results obtained can be compared with previous work or published data.
5.6 Powder metallurgy test specimens may have multiple uses. The dimensions and tolerances given in this standard are nominal in many cases. The user is cautioned to make certain that the dimensions of the test specimen are in agreement with the requirements of the specific test method to be used.
SCOPE
1.1 These standard practices cover the specifications for those uniaxially compacted test specimens that are used in ASTM standards, the procedures for producing and preparing these test specimens, and reference the applicable standards.
1.2 Basic tool design and engineering information regarding the tooling that is required to compact the test specimens and machining blanks are contained in the annexes.
1.3 This standard is intended to be a comprehensive one-source document that can be referenced by ASTM test methods that utilize PM test specimens and in ASTM PM material specifications that contain the engineering data obtained from these test specimens.
1.4 These practices are not applicable to metal powder test specimens that are produced by other processes such as cold isostatic pressing (CIP), hot isostatic pressing (HIP), powder forging (PF) or metal injection molding (MIM). They do not pertain to cemented carbide materials.
1.5 Detailed information on PM presses, compacting tooling and sintering furnaces, their design, manufacture and use are not within the scope of these practices.
1.6 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.7 This standard may involve hazardous materials, operations, and equipment. 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.
1.8 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.
General Information
Relations
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: B925 − 15 (Reapproved 2022)
Standard Practices for
Production and Preparation of Powder Metallurgy (PM) Test
Specimens
This standard is issued under the fixed designation B925; 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* ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 These standard practices cover the specifications for
mendations issued by the World Trade Organization Technical
those uniaxially compacted test specimens that are used in
Barriers to Trade (TBT) Committee.
ASTM standards, the procedures for producing and preparing
these test specimens, and reference the applicable standards.
2. Referenced Documents
1.2 Basictooldesignandengineeringinformationregarding
2.1 ASTM Standards:
the tooling that is required to compact the test specimens and
A34/A34M Practice for Sampling and Procurement Testing
machining blanks are contained in the annexes.
of Magnetic Materials
1.3 This standard is intended to be a comprehensive one-
A341/A341M Test Method for Direct Current Magnetic
sourcedocumentthatcanbereferencedbyASTMtestmethods
Properties of Soft Magnetic Materials Using D-C Per-
that utilize PM test specimens and in ASTM PM material
meameters and the Point by Point (Ballistic)Test Methods
specifications that contain the engineering data obtained from
A596/A596M Test Method for Direct-Current Magnetic
these test specimens.
PropertiesofMaterialsUsingthePointbyPoint(Ballistic)
1.4 These practices are not applicable to metal powder test Method and Ring Specimens
A773/A773M Test Method for Direct Current Magnetic
specimens that are produced by other processes such as cold
Properties of Low Coercivity Magnetic Materials Using
isostatic pressing (CIP), hot isostatic pressing (HIP), powder
Hysteresigraphs
forging (PF) or metal injection molding (MIM). They do not
A811 Specification for Soft Magnetic Iron Parts Fabricated
pertain to cemented carbide materials.
by Powder Metallurgy Techniques
1.5 Detailed information on PM presses, compacting tool-
A839 Specification for Iron-Phosphorus Powder Metallurgy
ing and sintering furnaces, their design, manufacture and use
Parts for Soft Magnetic Applications
are not within the scope of these practices.
A904 Specification for 50 Nickel-50 Iron Powder Metal-
1.6 The values stated in inch-pound units are to be regarded
lurgy Soft Magnetic Parts
as standard. The values given in parentheses are mathematical
A927/A927M Test Method for Alternating-Current Mag-
conversions to SI units that are provided for information only
netic Properties of Toroidal Core Specimens Using the
and are not considered standard.
Voltmeter-Ammeter-Wattmeter Method
1.7 This standard may involve hazardous materials, B215 Practices for Sampling Metal Powders
operations, and equipment. This standard does not purport to B243 Terminology of Powder Metallurgy
address all of the safety concerns, if any, associated with its B312 Test Method for Green Strength of Specimens Com-
use. It is the responsibility of the user of this standard to pacted from Metal Powders
establish appropriate safety, health, and environmental prac- B331 Test Method for Compressibility of Metal Powders in
tices and determine the applicability of regulatory limitations Uniaxial Compaction
prior to use. B438 Specification for Bronze-Base Powder Metallurgy
1.8 This international standard was developed in accor- (PM) Bearings (Oil-Impregnated)
dance with internationally recognized principles on standard- B439 Specification for Iron-Base Powder Metallurgy (PM)
Bearings (Oil-Impregnated)
These practices are under the jurisdiction of ASTM Committee B09 on Metal
Powders and Metal Powder Products and are the direct responsibility of Subcom-
mittee B09.02 on Base Metal Powders. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2022. Published March 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2003. Last previous edition approved in 2015 as B925 – 15. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/B0925-15R22. theASTM 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
B925 − 15 (2022)
B528 Test Method for Transverse Rupture Strength of Pow- 5. Significance and Use
der Metallurgy (PM) Specimens
5.1 Test specimens are used to determine the engineering
B595 Specification for Materials for Aluminum Powder
properties of PM materials, for example, tensile strength,
Metallurgy (PM) Structural Parts
ductility, impact energy, etc.; property data that are essential to
B610 Test Method for Measuring Dimensional Changes
the successful use of PM material standards. Processing PM
Associated with Processing Metal Powders Intended for
testspecimensunderproductionconditionsisthemostefficient
Die Compaction
method by which to obtain reliable PM material property data
B783 Specification for Materials for Ferrous Powder Metal-
since in most cases it is impractical or impossible to cut test
lurgy (PM) Structural Parts
bars from sintered parts.
B817 Specification for Powder Metallurgy (PM) Titanium
Alloy Structural Components (Withdrawn 2013) 5.2 The performance characteristics of metal powders, for
example, compressibility, green strength and dimensional
B823 Specification for Materials for Copper Base Powder
Metallurgy (PM) Structural Parts changesassociatedwithprocessingareevaluatedusingPMtest
specimens under controlled conditions. The data obtained are
B853 Specification for Powder Metallurgy (PM) Boron
Stainless Steel Structural Components important to both metal powder producers and PM parts
B939 Test Method for Radial Crushing Strength, K,of manufacturers.
Powder Metallurgy (PM) Bearings and Structural Materi-
5.3 PM test specimens play a significant role in industrial
als
quality assurance programs. They are used to compare prop-
B962 Test Methods for Density of Compacted or Sintered
erties of a new lot of metal powder with an established lot in
Powder Metallurgy (PM) Products Using Archimedes’
an acceptance test and are used in the part manufacturing
Principle
process to establish and adjust production variables.
B963 Test Methods for Oil Content, Oil-Impregnation
Efficiency, and Surface-Connected Porosity of Sintered 5.4 In those instances where it is required to present
Powder Metallurgy (PM) Products Using Archimedes’ equivalent property data for a production lot of PM parts,
standard test specimens compacted from the production pow-
Principle
E8 Test Methods for Tension Testing of Metallic Materials der mix to the same green density can be processed with the
production PM parts and then tested to obtain this information.
[Metric] E0008_E0008M
E9 Test Methods of Compression Testing of Metallic Mate-
5.5 Material property testing performed for industrial or
rials at Room Temperature
academic research and development projects uses standard PM
E18 Test Methods for Rockwell Hardness of Metallic Ma-
test specimens so the test results obtained can be compared
terials
with previous work or published data.
E23 Test Methods for Notched Bar Impact Testing of Me-
5.6 Powder metallurgy test specimens may have multiple
tallic Materials
E228 Test Method for Linear Thermal Expansion of Solid uses. The dimensions and tolerances given in this standard are
Materials With a Push-Rod Dilatometer nominal in many cases. The user is cautioned to make certain
E1876 Test Method for Dynamic Young’s Modulus, Shear that the dimensions of the test specimen are in agreement with
Modulus, and Poisson’s Ratio by Impulse Excitation of the requirements of the specific test method to be used.
Vibration
4 6. Powder Metallurgy Test Specimens
2.2 MPIF Standard:
Standard 56 Method for Determination of Rotating Beam
POWDER COMPRESSIBILITY TESTING
Fatigue Endurance Limit in Powder Metallurgy Materials
6.1 Cylindrical Powder Compressibility Test Specimen:
3. Terminology 6.1.1 Description and Use—This solid cylindrical test
specimen, see Fig. 1, is produced by compacting a test portion
3.1 Definitions—Definitions of powder metallurgy terms
of powder mix in laboratory powder metallurgy tooling similar
can be found in Terminology B243. Additional descriptive
to that shown in Fig. A1.1 in the Annex. An alternative test
information is available in the Related Materials section of Vol
specimen for measuring powder compressibility is the trans-
02.05 of the Annual Book of ASTM Standards.
verse rupture test specimen. These test specimens are not
sintered. The compressibility of the metal powder mix or a
4. Summary of Practice
compressibility curve showing the green density as a function
4.1 Thesepracticesdescribetheproduction,bypressingand
of compacting pressure is determined according to the proce-
sintering metal powders, and the preparation, by machining
dures in Test Method B331.
sinteredblanks,oftestspecimensusedtomeasurepropertiesof
6.1.2 Applicable ASTM Standards:
metal powders and sintered materials.
6.1.2.1 See Test Method B331.
TRANSVERSE RUPTURE, DIMENSIONAL CHANGE
The last approved version of this historical standard is referenced on
AND GREEN STRENGTH TESTING
www.astm.org.
Available from MPIF, 105 College Road East, Princeton, NJ 08540. 6.2 Transverse Rupture Strength Test Specimen:
B925 − 15 (2022)
6.2.1.2 It is an acceptable alternative test specimen to the
cylindrical compact to determine powder compressibility ac-
cording to Test Method B331. The sintered or heat treated
specimen may be used to generate data for the elastic con-
stants. Young’s Modulus is determined by impulse excitation
of vibration and Poisson’s ratio may then be calculated. This
test specimen is also a convenient compact on which to
measure macroindentation hardness after various processing
steps.
6.2.2 Applicable ASTM Standards:
6.2.2.1 See the following Test Methods: B312, B331, B528,
B610, E18, and E1876.
6.2.2.2 See the following PM Material Specifications:
A811, A839, A904, B783, and B823.
RADIAL CRUSHING STRENGTH TESTING
6.3 Radial Crushing Strength Test Specimen:
Dimensions
6.3.1 Description and Use—The radial crushing strength
in. mm
test specimen shown in Fig. 3 is compacted to size in tooling
D—Diameter 1.00 (25.4)
(Fig.A2.3) suitable for the production of a thin-walled hollow
T—Compact thickness 0.280 ± 0.010 (7.11 ± 0.25)
cylinder within the range of the dimensions listed. The testing
FIG. 1 PM Cylindrical Powder Compressibility Test Specimen
procedure involves the application of a compressive force
perpendicular to the central axis of the test cylinder and
calculating the radial crushing strength from the breaking load
6.2.1 Description and Use—The pressed-to-size transverse
and test specimen dimensions. Radial crushing strength is the
rupture test specimen, Fig. 2, is produced by compacting metal
material property that is used to quantify the mechanical
powder in tooling similar to that shown in Fig A1.2.
strength of sintered metal bearings, (oil-impregnated).
6.2.1.1 This rectangular test specimen has multiple uses in
PM. Primarily, it is designed to determine the transverse
rupture strength of sintered or heat treated compacts by
breaking the test specimen as a simple beam in three-point
loading following Test Method B528. But, it is also used to
measure the dimensional changes of metal powder mixes due
to pressing and sintering or other processing steps according to
Test Method B610, and it is used in both a 0.250 and 0.500 in.
(6.35 and 12.70 mm) thick version to determine green strength
using the procedure in Test Method B312.
Dimensions
in. mm
W—Width 0.50 (12.7) Dimensions
L—Length 1.25 (31.8) in. mm
R—Corner radius 0.01 (0.3) D—Outside diameter 0.80 to 2.00 (20 to 51)
T—Thickness (thin) 0.250 ± 0.005 (6.35 ± 0.13) d—Inside diameter 0.50 to 1.00 (13 to 25)
T—Thickness (thick) 0.500 ± 0.005 (12.70 ± 0.13) T—Thickness 0.25 to 1.00 (6 to 25)
NOTE 1—Thickness shall be parallel within 0.005 in. (0.13 mm). NOTE 1—Wall thickness (D-d) shall be less than D/3.
FIG. 2 PM Transverse Rupture Strength Test Specimen FIG. 3 PM Radial Crushing Strength Test Specimen
B925 − 15 (2022)
6.3.1.1 Radial Crushing Strength is determined following shape using tooling similar to that shown in Fig. A2.4 in the
the procedure in Test Method B939. Annex. This test specimen has been designed to have a
2 2
6.3.1.2 Thistestspecimeniswidelyusedinaqualitycontrol convenient 1.00 in. (645.2 mm ) pressing area to simplify
testtodeterminethesinteredmaterialstrengthofmetalpowder compacting calculations.
mixtures that are to be used for the production of any metal 6.4.1.1 It is intended for determining the tensile properties
powder product because it is a quick, easy test and gives and ductility of PM materials that have not been heat treated
reliable and reproducible results. Laboratories testing powder (not quenched and tempered nor sinter-hardened). The testing
mixes intended for the manufacture of porous bearings have proceduresforthisunmachinedPMtestspecimencanbefound
recognized that breaking an unsintered test specimen by in Test Method E8.
diametrical loading will give a green strength value that is 6.4.1.2 The flat tension test specimen is not normally used
relevant in production. with heat treated PM materials because it may produce
6.3.1.3 Laboratories testing powder mixes intended for the unreliable test results and it has a tendency to slip in the grips.
manufacture of porous bearings have recognized that using a Slippagecanbepreventedbytheuseofhydraulicgrips,butthe
hollow cylindrical test specimen for dimensional change mea- squarecornerdesignoftheflatspecimenwillgiverisetostress
surements and determination of green strength will give values concentrations that may result in scattered test values. The
that are relevant in production. machined 190-Round tension test specimen, Fig. 5, is recom-
6.3.1.4 This specimen finds use in determining oil content, mended for use with heat treated PM materials.
impregnation efficiency and interconnected porosity of PM 6.4.2 Applicable ASTM Standards:
bearing materials foll
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