G115钢管埋弧自动焊焊缝冲击性能不足的原因分析及热处理修复措施

Cause analysis of insufficient impact toughness and heat treatment repair process of G115 steel pipe SAW weld

采用埋弧自动焊(SAW)对大口径厚壁G115钢管进行焊接,焊后经785℃回火后发现焊缝冲击吸收能量低于标准要求的最低值。通过对焊接方法、焊材及回火温度的分析和试验表明,焊缝的回火温度超出了熔覆金属的Ac_(1)点,产生不完全相变组织,且碳化物回溶、沉淀强化作用减少、马氏体亚结构和位错密度降低、析出相长大粗化等多种因素的交互作用最终造成了焊缝冲击性能的下降。采用1080℃×3 h正火+770℃×6.5 h回火的热处理修复后,焊缝的冲击性能得到大幅度的提升。

A large-diameter thick wall G115 steel pipe was welded by submerged arc automatic welding(SAW).After post weld tempering at 785℃,the impact absorbed energy of the weld is lower than the minimum value required by the standard.Based on the analysis and test of the welding method,welding material and tempering temperature,the results show that the tempering temperature of the weld exceeds the Ac_(1) point of the clad metal,resulting in incomplete phase transformation structure,and the interaction of various factors such as carbide redissolution,reduction of precipitation strengthening,martensite substructure and dislocation density,as well as growth and coarsening of precipitated phases,eventually leads to the decrease of weld impact property.Through the heat treatment repair process of normalizing at 1080℃for 3 h and tempering at 770℃for 6.5 h,the impact property of the weld is greatly improved.