Effects of Tempering Temperature on the Microstructure and Mechanical Properties of Steel Large Heat Input Welding Steel

The effect of tempering temperature on the mechanical property and microstructure of a large heat input welding steel was researched by traditional mechanical testing equipment,OM and SEM.The results showed that the microstructure of the steel under TMCP is ferrite,basinet,and a little of martensite.The structure of the samples is ferrite and tempering sorbite,and some carbides are precipitated after high temperature tempering.The fracture of the samples is characterized by dimples and the inclusions are usually two or some kinds of complex inclusions including Al2O3、MnS and TiO2.With increasing tempering temperature,the carbides on the ferrite base gather and grow.The tensile strength of the samples reduces sharply after tempering,and the impact toughness improves greatly,and the elongation increases gradually.The best tempering temperature is in the rage of 600～630 ℃.