ISO 2566-1:2021

This document specifies a method of converting room temperature percentage elongations after fracture obtained on various proportional and non-proportional gauge lengths to other gauge lengths.
Formula (1), on which conversions are based, is considered to be reliable when applied to carbon, carbon manganese, molybdenum and chromium molybdenum steels within the tensile strength range 300 N/mm2 to 700 N/mm2 and in the hot-rolled, hot-rolled and normalized or annealed conditions, with or without tempering.
These conversions are not applicable to:
a) cold reduced steels;
b) quenched and tempered steels;
c) austenitic steels.
These conversions are not applicable when the gauge length exceeds  or where the width to thickness ratio of the test piece exceeds 20.