Effects of weld thermal cycle on microstructure and properties of heataffected zone of Q890 processed steel

By using thermal simulation technology and impact test to study Q890 steel microstructure and properties of each HAZ peak at different temperature conditions. The results show that the simulated welding thermal cycling conditions were experienced coarse grain heated affected zone (CGHAZ), fine grain heated affected zone (FGHAZ), intercritial grain heated affected(IGHAZ) zone and intercritial reheated coarse grain heated affected zone(ICCGHAZ). Impact test results show that the impact toughness of FGHAZ up to 222.7 J; and the ICCGHAZ toughness is the lowest 16.3 J. Analysis concluded that the lower value of charpy impact energy observed in the ICCGHAZ and ICGHAZ is due to the formation of martensiteaustenite constituent along the grain boundaries, and formation concentrated stress and microcracks, leading to its relatively lower impact energy. Additionally， the FGHAZ since the original austenite grain refinement, and high angle grain boundaries orientation θ, in 15°<θ<45° range has the highest percentage is 257% which can improve the impact toughness of the region.