一种控轧控冷高强钢焊接接头行为研究

Study on the Behavior of Welding Joint with TMCP High-Strength Steel

采用80％Ar＋20％CO2混合气体保护焊对一种具有代表性的控轧控冷高强钢进行了焊接强度试验研究，重点分析了热影响区回火工艺对焊接接头软化性能的影响。结果表明，试验钢的强化手段以细晶强化、变形强化和析出强化为主；随着焊接热输入增大，焊接接头强度降低，微观机理体现在粗晶热影响区的晶粒长大及其内部细小的（Ti，Nb）（C，N）第二相粒子的回溶行为有关；回火处理后的焊接接头随回火温度的提高，焊接接头软化程度降低，但回火脆性严重增大，其原因为回火处理促使焊态CGHAZ组织中大量的M／A岛分解，形成了正交Fe3C型碳化物，脆化了晶界。

The welding strength of a typical high- strength steel with TMCP applied by MAG （80% Ar ＋ 20% CO2 ） is studied and main point focuses on the softening reasons in HAZ and the influence of drawing temper on mechanical properties of MAG welding joint. The results indicate that the mechanism of tested steel includes fine-grain strengthening, deformation strengthening and precipitation strengthening. The strength of welding joint decreased with the increase of welding heat input, resulting from growth of grain in CGHAZ and dissolution of the （ Ti, Nb） （ C, N） in the same area. The softening of welding joint reduces with the drawing temperature increasing, while the impact toughness of CGHAZ decreased rapidly due to the disintegration of M/A on CGHAZ after drawing temper, making the Fe3C-style carbide precipitation along the grain boundaries.