Effect of Postweld Heat Treatments on the Hardness and Microstructure of 17% Cr Ferritic Stainless Steels.

Poor weldability is the main obstacle that prevents greater utilization of 17% chromium ferritic stainless steels. As far as the mechanical properties are concerned, the welds of this steel are characterized by low toughness and ductility. In the present paper the effect of postweld heat treatments on the microstructure and hardness of AISI 430 steels was studied. Alloys with addition of niobium and titanium were also investigated. The TIG process without filler metal was employed in welding the materials. Postweld heat treatments consisted of isothermal annealing in the temperature range 250 to 900 degree C for 30 min, followed by air cooling. No sensitive changes in microstructure were observed after the postweld heat treatments. The changes in hardness were more remarkable.