ASTM B923-02(2008)
(Test Method)Standard Test Method for Metal Powder Skeletal Density by Helium or Nitrogen Pycnometry
Standard Test Method for Metal Powder Skeletal Density by Helium or Nitrogen Pycnometry
SIGNIFICANCE AND USE
Both suppliers and users of metals can benefit from knowledge of the skeletal density of these materials. Results of many intermediate and final processing steps are controlled by or related to skeletal density of the metal. In addition, the performance of many sintered or cast metal structures may be predicted from the skeletal density of the starting metal powder, for all or a portion of the finished piece.
SCOPE
1.1 This test method covers determination of skeletal density of metal powders. The test method specifies general procedures that are applicable to many commercial pycnometry instruments. The method provides specific sample outgassing procedures for listed materials. It includes additional general outgassing instructions for other metals. The ideal gas law forms the basis for all calculations.
1.2 This test method does not include all existing procedures appropriate for outgassing metal materials. The included procedures provided acceptable results for samples analyzed during an interlaboratory study. The investigator shall determine the appropriateness of listed procedures.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3.1 This test method uses SI units as standard in accordance with IEEE/ASTM SI 10. State all numerical values in terms of SI units unless specific instrumentation software reports volume and/or density using alternate units. In this case, present both reported and equivalent SI units in the final written report. Many instruments report skeletal density as g/cm3 instead of using correct SI units (kg/m3).
1.4 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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation:B923–02 (Reapproved 2008)
Standard Test Method for
Metal Powder Skeletal Density by Helium or Nitrogen
Pycnometry
This standard is issued under the fixed designation B923; 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 E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers determination of skeletal den-
IEEE/ASTM SI 10 American National Standard for Use of
sity of metal powders. The test method specifies general
the International System of Units (SI): The Modern Metric
procedures that are applicable to many commercial pycnom-
System
etry instruments. The method provides specific sample outgas-
sing procedures for listed materials. It includes additional
3. Terminology
general outgassing instructions for other metals. The ideal gas
3.1 Definitions:
law forms the basis for all calculations.
3.1.1 Refer to Terminology B243 for additional definitions
1.2 This test method does not include all existing proce-
relating to metal powders.
dures appropriate for outgassing metal materials. The included
3.2 Definitions of Terms Specific to This Standard:
procedures provided acceptable results for samples analyzed
3.2.1 density, n—the mass per unit volume of a material.
during an interlaboratory study. The investigator shall deter-
3.2.2 density, skeletal, n—the ratio of mass of discrete
mine the appropriateness of listed procedures.
pieces of solid material to the sum of the volumes of the solid
1.3 The values stated in SI units are to be regarded as
material in the pieces and closed (or blind) pores within the
standard. No other units of measurement are included in this
pieces.
standard.
3.2.3 outgassing, n—the evolution of gas from a material in
1.3.1 This test method uses SI units as standard in accor-
a vacuum or inert gas flow, at or above ambient temperature.
dance with IEEE/ASTM SI 10. State all numerical values in
3.2.4 skeletal volume, n—the sum of the volumes: the solid
terms of SI units unless specific instrumentation software
material in the pieces and closed (or blind) pores within the
reports volume and/or density using alternate units. In this
pieces.
case, present both reported and equivalent SI units in the final
written report. Many instruments report skeletal density as
4. Summary of Test Method
3 3
g/cm instead of using correct SI units (kg/m ).
4.1 An appropriately sized sample (to provide at least the
1.4 This standard does not purport to address all of the
minimum skeletal volume required for reliable results for the
safety concerns, if any, associated with its use. It is the
instrument or apparatus used) is outgassed under appropriate
responsibility of the user of this standard to establish appro-
conditions prior to analysis.
priate safety and health practices and determine the applica-
4.2 The sample is weighed to nearest 0.1 mg. It is important
bility of regulatory limitations prior to use.
to use an analytical balance to determine the sample mass. The
2. Referenced Documents pycnometermeasuresthetotaldisplacedskeletalvolumeofthe
2 sample under analysis. The sample mass is then used to
2.1 ASTM Standards:
calculate the skeletal density of the metal. Any error in the
B215 Practices for Sampling Metal Powders
sample mass will affect the calculated density. Some cleaning
B243 Terminology of Powder Metallurgy
of the sample surface may take place inside the pycnometer.
Therefore, it is best to reweigh the sample after analysis and
This test method is under the jurisdiction of ASTM Committee B09 on Metal
use the final mass when calculating skeletal density.
Powders and Metal Powder Products and is the direct responsibility of Subcom-
4.3 Sample skeletal volume is determined a minimum of
mittee B09.03 on Refractory Metal Powders.
five times. Skeletal volume average and standard deviation are
Current edition approved April 1, 2008. Published April 2008. Originally
approved in 2002. Last previous edition approved in 2002 as B923–02. DOI: calculated using standard statistical methods.
10.1520/B0923-02R08.
4.4 Calculations are based on the ideal gas law, as required
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
by the instrument being used for the determination. The
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
assumption of ideal behavior is accepted as valid at analytical
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B923–02 (2008)
temperatures and pressures. For instruments designed with two 8. Reagents and Materials
pressure chambers, one a sample compartment, and the other a
8.1 Helium, 99.999 mole percent, with the sum of N,O ,
2 2
gas expansion chamber, the equation for sample volume
argon, CO , hydrocarbons (as CH ), and H O totaling less than
2 4 2
calculation takes the form:
10 parts per million; dry and oil-free; cylinder, or other source
P of purified helium.
V 5 V 2 V · (1)
S D
sample cell exp
P 2 P
8.2 Nitrogen, 99.999 mole percent, with the sum of O ,
1 2
argon, CO , hydrocarbons (as CH ), and H O totaling less than
2 4 2
where:
10 parts per million; dry and oil-free; cylinder, or other source
V = calculated sample volume,
sample
of purified nitrogen.
V = calibrated sample compartment volume,
cell
8.3 Other High Purity Gas, dry and oil-free; cylinder, or
V = calibrated expansion volume,
exp
other source of gas, if other gas is to be used as the analysis or
P = measured gas pressure when only V is filled
1 cell
flushinggas.Theactualcompositionofthegasshallbeknown.
with analysis gas, and
P = measured gas pressure after expansion of the
9. Hazards
analysis gas into V .
exp
9.1 Precautions applying to the use of compressed gases
should be observed.
5. Significance and Use
5.1 Both suppliers and users of metals can benefit from
10. Sampling, Test Specimens, and Test Units
knowledge of the skeletal density of these materials. Results of
10.1 No specific instructions are given. However, it is
many intermediate and final processing steps are controlled by
important that the test portion being analyzed represent the
or related to skeletal density of the metal. In addition, the
larger bulk sample from which it is taken. The bulk sample
performance of many sintered or cast metal structures may be
should be homogenized before any sampling takes place. Best
predicted from the skeletal density of the starting metal
results are obtained when a flowing bulk material is tempo-
powder, for all or a portion of the finished piece.
rarily diverted into a collector for an appropriate time. It is
better to sample the entire flow for a short time than to sample
6. Interferences
a portion of the flow for a longer time. Collecting several small
6.1 This test method can be used to determine the skeletal
test portions and combining them improves the reliability of
volume of a powder
...
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