B.X. Liu

Microstructure Analysis and Weldability Investigation of Stainless Steel Clad Plate

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.

Microstructures and Tensile Behaviors of Stainless Steel Clad Plate

A novel bi-layers clad plate comprising of stainless steel and carbon steel has been successfully fabricated by vacuum hot rolling at a high temperature of 1100 °C. The microstructure observation showed an interfacial transition zone about 80–100 μm in width, which is attributed to the diffusion of carbon element at the interface. The stainless steel clad plate exhibited a high ultimate tensile strength (578 MPa) and high uniform elongation (52%), and the elastic modulus and stress mismatch at the interface resulted into severe warping resilience phenomenon. Fracture characterizations highlight that the delamination and intergranular cracks presented at the interfacial transition zone.