Abstract: The effect of di®erent peak temperature (Tp) and cooling time (t8=5) on hardness, impact toughness and fracture morphology in the heat-affected zone (HAZ) of HQ130 steel was studied by using welding thermo-simulation test. Experimental results show that the impact toughness and hardness decrease with the decrease of Tp or increase of t8=5 under the condition of a single thermal cycle. There is a brittle zone in the vicinity of Tp=800±C,where the impact toughness is considerably low. There is softened zone in vicinity of Tp=700±C,Where the hardness decreases but the toughness increases. In the practical application of multi-layer and multi-pass welding, the welding heat input should be strictly limited (t8=5<=20s) so as to reduce the softness and brittleness in the HAZ of HQ130 steel.

Key words: high strength steel, welding thermal cycle, heat-affected zone, impact toughness