二次热循环对X80钢管焊缝组织及韧性的影响

Effect of secondary thermal cycle on weld microstructure and toughness of X80 steel pipe

采用焊接热模拟技术及力学性能测试等,研究了X80钢管焊缝组织在不同二次峰值温度下的变化规律及冲击韧性。结果表明:对于焊缝粗晶区,当二次热循环峰值温度处于未变粗晶区范围时,其韧性最差;对于焊缝细晶区,在经历两相区二次热循环后冲击韧性变化不大;对于焊缝临界区,由于在晶界形成了大尺寸的M-A链状组织,对韧性不利。对比不同化学成分的焊缝,减少铁素体稳定元素以降低奥氏体相变转变温度对提高环缝冲击韧性有利。

By using the welding thermal simulation technology and the mechanical property test, the regularity and the impact toughness of X80 steel pipe weld at different secondary peak temperatures were studied. The results showed that when the peak temperature of the second thermal cycle was in the range of un-coarsening zone, the toughness of the weld coarse-grained zone was the lowest. For the weld fine-grained zone, the impact toughness changed little after the second thermal cycle in the two-phase zone. For the weld intercritical zone, the formation of large size M-A chain organization in the grain boundary was detrimental to weld toughness. Comparing the two joints with different chemical composition, reducing the ferrite stable elements to decrease the temperature of the austenite transformation was beneficial to improve the impact toughness of the girth weld.