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.