This International Standard 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.
EN ISO 643:2012 history
2020EN ISO 643:2020 Steels - Micrographic determination of the apparent grain size (ISO 643:2019, Corrected version 2020-03)
2012EN ISO 643:2012 Steels - Micrographic determination of the apparent grain size
2003EN ISO 643:2003 Steels - Micrographic determination of the apparent grain size ISO 643: 2003