The microstructure evolution, hardness and impact toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of a V-N microalloyed X80 pipeline steel were studied. The results indicated that the microstructure mainly consisted of bainitic ferrite, acicular ferrite and granular bainite. The area fraction and size of M/A constituents were increased with increasing heat input. As heat input increased from 15 to 60 kJ cm⁻¹, the hardness gradually decreased from 301 to 243 HV, and impact energy decreased from 284 to 33 J. Hardness in the CGHAZ was not sensitive to heat input. When the heat input exceeded 30 kJ cm⁻¹, the formation of coarse granular bainite and large-sized blocky M/A constituents resulted in the deterioration of impact toughness.

研究了一种 VN 微合金化 X80 管线钢模拟粗晶热影响区 (CGHAZ) 的组织演变、硬度和冲击韧性。结果表明，显微组织主要由贝氏体铁素体、针状铁素体和粒状贝氏体组成。M/A 成分的面积分数和尺寸随着热输入的增加而增加。随着热输入从 15 kJ cm ^-1增加到 60 kJ cm ^-1，硬度从 301 HV 逐渐降低到 243 HV，冲击能量从 284 到 33 J。CGHAZ 中的硬度对热输入不敏感。当热输入超过30 kJ cm ^{-1 时}，粗粒贝氏体和大尺寸块状M/A 成分的形成导致冲击韧性变差。