ISO 643 specifies a micrographic method of determining apparent ferritic or austenitic grain size in steels. It describes the methods of revealing grain boundaries and of estimating the mean grain size of specimens with unimodal size distribution.
Although grains are three-dimensional in shape, the metallographic sectioning plane can cut through a grain at any point from a grain corner, to the maximum diameter of the grain, thus producing a range of apparent grain sizes on the two-dimensional plane, even in a sample with a perfectly consistent grain size.
Status: WithdrawnPublication date: 2003-02
Edition: 2Number of pages: 35
Technical Committee: ISO/TC 17/SC 7 Methods of testing (other than mechanical tests and chemical analysis)