HAZ Structure, Toughness and Characteristics to Hydrogen-Induced Cracking(HIC) of Steel 20MnNiMo

In this paper the effect of the cooling condition during welding on HAZ structure,toughness and susceptibility to Hydrogen-Induced Cracking(HIC) of steel 20MnNiMo was studied.The experimental results showed that the cooling rate t_8/3 considerably affected both the HAZ toughness and the susceptibility to HIC.The M or M with a little B structure in HAZ and better low temperature toughness were obtained,when t_8/3 was less than 55s.However this structure was sensitive to HIC.In order to avoid HIC and get better toughness in HAZ,the lower heat input,lower temperature preheating and hydrogen removal promptly after welding were recommended.