EN ISO 643:2012

Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviated terms
5 Principle
6 Selection and preparation of the specimen
7 Characterization of grain size
8 Test report
Annex A (informative) - Summary of methods for revealing
        ferritic, austenitic or prior-austenitic grain
        boundaries in steels
Annex B (normative) - Determination of grain size -
        Standard charts taken from ASTM E112
Annex C (normative) - Evaluation method

ISO 643:2012 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.