Microstructure Analysis and Weldability Investigation of Stainless Steel Clad Plate

Abstract

Stainless steel clad plate and pipe have a prevailing applications in nuclear power plants. The microstructure and mechanical properties of 304 austenite stainless steel clad plate by vacuum hot rolling were investigated in detail. Due to the severe diffusion of carbon element from carbon steel substrate to stainless steel clad, the decarburized layer and carburized layer were formed at the interfacial transition zone. The bending test reveals super-high interface strength and toughness, delaying the premature occurrence of interfacial delamination crack. The stainless steel clad pipe were successfully fabricated by elbowing and welding. There are no macroscopic and microscopic defects in the weld zone, fusion zone and heat affected zone. The heat affected zone of carbon steel layer contains widmanstatten, completely crystallized zone, partial crystallized zone and recrystallized zone. The weld zone of carbon steel contains widmanstatten structure and refined ferrite and pearlite. However, the heat affected zone is only comprised of coarse grains. With the increase of distance between weld zone and fusion zone, the small plane grain firstly changes into cellular crystal grain, and finally into columnar crystal in the stainless steel weld zone.