Both steels fall into a general category that is variously referred to as of creep resistant steels or pressure vessel steels or “Chrome – Moly’s”. They both are covered by WNr* 1.5415.

15Mo3 is the older of the two designations and it is covered by the standard DIN 17 155. This is for  steels that are used for plants that are subject to regular inspection. 16Mo3 is the designation that is used in the standard EN 11028-2 which was introduced in 1992 and which contains the statement “that conflicting national standards shall be withdrawn at the latest by October 2000.” It thus supersedes DIN 17 155. Not withstanding this, there may be many old designs and drawings that are in circulation which may call for the grade 15Mo3.

The composition and mechanical properties of the grades as given in the respective standards are compared in a separate download

*Werkstoff Nommer (WNr) Or Material Number is a European steel designation system covered by the specification DIN EN 10027-2.