Combined effects of welding heat input and peak temperature on precipitation and mechanical properties of the HAZ for modified austenitic medium manganese steels

Abstract

We studied the microstructure and mechanical properties of the simulated welding heat-affected zone (HAZ) for modified austenitic medium manganese steels (MAMMS) in the welding peak temperature range of 750 °C to 1050 °C. The precipitation behavior of cementite and VC particle was sensitive to the welding thermal cycle in this temperature range. When the peak temperature increased from 750 °C to 850 °C, the intergranular cementite and VC particle became coarser, leading to deterioration of toughness. However, when the peak temperature raised to 1050 °C, the intergranular cementite disappeared. The sensibility of tensile strength to heat input at high peak temperature was higher than that at low temperature, which implied that it was affected by combined effects of the two factors of heat input and peak temperature, rather than a single factor. This variation tendency was highly related with the coarsening behavior of VC particle depending on the interaction effect of these two factors. The growth rate of VC particle with peak temperature of 850 °C was ∼4 times as high as that with peak temperature of 750 °C. However, it only increased to ∼1.3 times when the peak temperature increased from 850 °C to 1050 °C.