Response of Second Phase Particles in Ti-V-Nb Microalloyed Steel During Weld Thermal Cycles
Ti-V-Nb微合金钢第二相粒子在焊接热循环过程中的变化规律

By using carbon extraction replica technology and welding thermal simulation, the second phase particles in parent metal, weld metal and simulated coarse grain heat affected zone (CGHAZ) of Ti-V-Nb microalloyed steel were investigated. Experiment results and analysis show that the particle sizes in the steel are less than 100 nm, and the relative content of Ti in particles increases with increasing particle size. During welding, most of carbonitride particles in welding pool dissolved, the dissolved Ti takes part in deoxidation reaction producing TiO, TiO combined with the other deoxidation or desulfuration products to form large inclusion, dissolved Nb and V did not re-precipitated. TiO and MnAl2O4 formed at the surface of inclusions have cubic coherent relationship. A large quantity of carbonitride particles remained in CGHAZ after welding thermal cycle, the shape of particles changed from irregular shape to cubic one, the mean particle size increased and all of these particles are rich in Ti.