TWI Frequently asked questions
by Andrea Gregori (updated by Briony Holmes)
NORSOK Standard M-630 Rev.4 January 2004 - Material data sheets for piping - includes material requirements in the form of a collection of material data sheets (MDS) for use in piping systems for the petroleum industry. These MDSs provide both HRC and HV10 limits for duplex and superduplex stainless steels. The limits for 22Cr duplex parent material, HAZ, weld metal are 28HRC or 271HB or 290HV10. The limits for 25Cr duplex are 32HRC or 301HB or 330HV10. NORSOKStandard M-601 Rev.3 January 2004 - Welding and inspection of piping - states in Table 2 that hardness of duplex stainless steel welds for sour service shall be below the following limits: 22Cr duplex 310HV10, 25Cr duplex 330HV10.
Section 7, Table 7-11 of DNV Standard OS-F101 2007 - Submarine pipeline systems - provides HV10 limits for weldments in 22Cr and 25Cr duplex stainless steels for linepipes. For 22Cr and 25Cr duplex, the hardness in the weld and HAZ shall not exceed 350HV10 and Section 6, paragraph B201 of DNV Standard OS-F101 2007 states that materials shall be selected for compliance with ISO 15156.
