Microstructure and Mechanical Properties of Ti-Alloyed Supermartensitic 12%Cr Stainless Steel Classes 95 ksi and 110 ksi for Oil and Gas Production

Compared to other stainless steels, the supermartensitic stainless steels (SMSS) are a new sub-family with improved weldability and mechanical and corrosion resistance properties. Besides the drastic reduction of carbon content and Ni and Mo addition, these steels may also contain microadditions of Ti, Nb, V and/or N to the improve mechanical resistance. These materials are mainly used as seamless pipes for casings and tubulars for oil and gas off-shore production. After hot rolling (Mannesman process), the tubes are quenched and tempered to achieve the required mechanical properties. Tempering temperature is adjusted as function of the class of mechanical resistance, 95 ksi or 110 ksi. In this work, based on the mechanical properties data, the heat treatment used to produce steels of classes 95 and 100 ksi were determined. The microstructural features of the as tempered steel were investigated and compared to the microstructure of specimens treated for classes 95 ksi and 110 ksi.