ISO 2639 defines the case-hardened depth, and specifies methods for the determination of this depth, in steel.It is applicable tocarburized cases and carbonitrided cases;parts that, when heat treated to final hardness, have a hardness of less than 450 HV 1 at a distance of three times the case-hardened depth, from the surface.The case-hardened depth is defined by special agreement where these conditions are not met.