High Heat Input Welding of 12Cr-6Ni-2.5Mo Supermartensitic Stainless Steel

In conventional welding of 13% Cr supermartensitic stainless steels, the normal microstructure that forms on cooling is martensite. Although high heat input tends to give a certain coarsening of the final microstructure, the eventual accompanying loss in toughness is not known. The present study was initiated to examine the effect of heat input on weld metal and heat affected zone mechanical properties of a 12Cr-6Ni-2.5Mo grade. The results obtained showed that the notch toughness is low (25 J) and independent of heat input for the weld metal, while it is reduced with increasing heat input for fusion line and the heat affected zone locations. Subsequent post weld heat treatment gave a substantial increase in toughness for all notch locations. Based on these results, indications are that a specified maximum heat input is not applicable in welding of supermartensitic stainless steels, allowing more production efficient techniques to be used, both in longitudinal seam and girth welding.