BS EN ISO 643 is the international Standard that 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.
History and related standardsThis international Standard supersedes BS 4490:1989 which is withdrawn.
BS EN ISO 643 includes the following cross references:
ISO 3785, ISO 14250, ASTM E112.
