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Significance and Use
5.1.3 The absolute dimensional change may be used to classify powders or differentiate one type or grade from another, to evaluate additions to a powder mixture or to measure process changes, and to guide in the design of tooling.
5.1.4 The comparative dimensional change is mainly used as a quality control test to measure variations between a lot or shipment of metal powder and a reference powder of the same material composition.
5.1.5 Factors known to affect size change are the base metal powder grade, type and lot, particle size distribution, level and types of additions to the base metal powder, amount and type of lubricant, green density, as well as processing conditions of the test specimen; heating rate, sintering time and temperature, sintering atmosphere, and cooling rate.
5.2.1 The general procedure of measuring the die or a test compact before and after a PM processing step, and calculating a percent dimensional change is also adapted for use as an internal process evaluation test to quantify green expansion, repressing size change, heat treatment changes or other changes in dimensions that result from a manufacturing operation.
1.2 The dimensional change is determined by a quantitative laboratory procedure in which the arithmetic difference between the dimensions of a die cavity and the dimensions of a sintered test specimen produced from that die is calculated and expressed as a percent growth or shrinkage.
1.3 With the exception of the values for density and the mass used to determine density, for which the use of the gram per cubic centimetre (g/cm3) and gram (g) units is the long-standing industry practice, 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.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
B215 Practices for Sampling Metal Powders
B243 Terminology of Powder Metallurgy
B925 Practices for Production and Preparation of Powder Metallurgy (PM) Test Specimens
B962 Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes Principle
ICS Number Code 77.160 (Powder metallurgy)