Influences of Heat Treatment on Microstructure and Corrosion Resistance of 316L Stainless Steel Weld in Welded Joint of Composite Plate

The composite plate of Q345 carbon steel and 316L stainless steel was welded, and the welded joint was treated by different heat treatment processes. The effects of heat treatment process on the microstructure and corrosion resistance of 316L stainless steel weld were studied by observation of microstructure, intergranular corrosion test and stress corrosion test. The results show that the microstructure of 316L stainless steel weld was austenite with strips of ferrite. The grain boundary of austenite became wider when the time of heat treatment increased. After the second heat treatment of 316L stainless steel weld, Cr₂₃C₆ was precipitated in the grain boundary of austenite, where chromium depleted region formed, and intergranular corrosion and stress corrosion easily happened. So the corrosion resistance of the welded joint of 316L stainless steel was decreased.