【国外标准】 Standard Test Method for Measuring Dimensional Changes Associated with Processing Metal Powders Intended for Die Compaction

5.1 Dimensional Change When Compacting and Sintering Metal Powders:5.1.1 The dimensional change value obtained under specified conditions of compacting and sintering is a material characteristic inherent in the powder.5.1.2 The test is useful for quality control of the dimensional change of a metal powder mixture, to measure compositional and processing changes and to guide in the production of PM parts.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 Dimensional Change of Various PM Processing Steps: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.1.1 This standard covers a test method that may be used to measure the sum of the changes in dimensions that occur when a metal powder is first compacted into a test specimen and then sintered.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.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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 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.