EVS-EN ISO 643:2024

This document specifies micrographic methods 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.