Effect of Thermal Cycle on Microstructure and Fracture Morphology in HAZ of HQ130 Steel

摘要

The effect of different peak temperature(T_P) and cooling time(t_(8/5)) on microstructure,hardness,impact toughness and fracture morphology in the heat-affected zone(HAZ) of HQ130 steel was studied by using weld thermo-simulation test.Experimental results indicate that the impact toughness and hardness decrease with the decrease of T_P or increase of t_(8/5) under the condition of a single thermal cycle.There is a brittle zone in the vicinity of T_P = 800 ℃,where the impact toughness is considerably low.There is a softened zone in the vicinity of T_P = 700℃,where the hardness decreases but the toughness increases.In the practical application of multi-layer and multipass welding,the welding heat input should be strictly limited(t_(8/5)≤20s) so as to reduce the softness and brittleness in the HAZ of HQ130 steel.