Simulated Weld HAZ Impact Toughness of 700 MPa Ultra-low Carbon Bainitic Steel

Abstract Ultra-low carbon bainitic steel is a kind of high strength and high toughness steel with ultra-low carbon, high cleanliness and ultra-fine grain characteristics. In this paper, the welding thermal simulation technology is used to study the influence law of 700MPa ultra-low carbon bainitic steel B700 welding thermal process on the microstructure and properties of its CGHAZ. The results show that CGHAZ with a peak temperature of 1350 °C and a t8/5 of 15 s can obtain higher impact toughness. The impact toughness of HAZ with a peak temperature of 950°C is higher. The secondary thermal cycles with peak temperatures of 1150°C and 950°C significantly improved the impact toughness of CGHAZ, and the former improvement was better than the latter.