ASTM B312 – Standard Test Method for Green Strength of Specimens Compacted from Metal Powders
Significance and Use
5.1 The green strength value determined under the conditions specified by this test method is influenced by the characteristics of the powder, how it compacts under the specified conditions (that is, the particle to particle bonding that exists following compacting), and the lubrication system used.
5.2 Knowledge of the green strength value is useful to the production, characterization, and utilization of metal powders in the manufacture of PM structural parts and bearings.
5.3 The test for green strength of a compacted metal powder can be used to:
5.3.1 Relate the resistance of a pressed compact to breakage or damage due to handling.
5.3.2 Compare the quality of a metal powder or powder mixture from lot to lot.
5.3.3 Determine the effect of the addition of a lubricant or other powders to a base powder.
5.3.4 Evaluate powder mixing or blending variables.
5.4 Factors that are known to influence the green strength of a metal powder are particle shape, particle size distribution, and compressibility of the metal powder.
5.5 The amount and type of lubricant or other additives and the mixing procedures have a strong effect on the green strength of specimens produced from metal powder mixtures.
1.1 This standard covers a test method that may be used to measure the transverse rupture strength of a compacted but unsintered (green) test specimen produced from lubricated or unlubricated metal powders or powder mixtures.
1.2 Green strength is measured by a quantitative laboratory procedure in which the fracture strength is calculated from the force required to break an unsintered test specimen supported as a simple beam while subjected to a uniformly increasing three-point transverse load under controlled conditions.
1.3 This test method is a companion standard to Test Method B528 that covers the measurement of the transverse rupture strength of sintered PM test specimens.
1.4 Units—With the exception of the values for density and the mass used to determine density, for which the use of the gram per cubic centimeter (g/cm3) and gram (g) units is the longstanding industry practice, the values 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.