Effect of heat input and heat treatment on microstructure and mechanical properties of welded joint of TMCP890 steel

The microstructure and mechanical properties of welded joint of TMCP890 are studied by means of thermal simulation and gas metal arc welding. It is found that the heat-affected zone has high toughness after welding. After welding with 900-MPa grade filler wire, the weld metal has good toughness and the strength of welded joint is comparable to that of the steel. Two hundred fifty degrees celsius postweld heat treatment does not affect the strength and toughness of welded joint. After 480 degrees C postweld heat treatment, the strength is a little lowered and toughness of weld metal and heat-affected zone is reduced remarkably. After 600 degrees C postweld heat treatment, the strength and toughness of weld metal and heat-affected zone are damaged seriously. Light optical microscope, SEM, TEM, and EBSD are used to analyze the microstructure of experimental samples. It is found that filmy residual austenite and low quantity of M-A constitutes with small size contribute to the high toughness of heat-affected zone in a great deal. The adverse effect of high-temperature postweld heat treatment on toughness is because of the large-sized precipitated particles.