Li Ba, Liu Qingyou, Jia Shujun, Ren Yi, Yang Ping
Engineering Steel Research Institute, Central Iron and Steel Research Institute, Beijing 100081, China.
State Key Laboratory of Metal Material for Marine Equipment and Application, Iron & Steel Research Institutes of Ansteel Group Corporation, Anshan 114009, China.
Materials (Basel). 2022 Jan 21;15(3):794. doi: 10.3390/ma15030794.
In this paper, the welding thermal cycle process of deep-sea pipeline steel was investigated by welding thermal simulation. The microstructure evolution, crystallology and second-phase precipitation behavior of the soft zone of the heat-affected zone (HAZ) were characterized and analyzed by combining scanning electron microscopy, electron back-scattered diffraction, transmission electron microscopy and hardness testing. The results show that HAZ softening appeared in the fine-grained zone with a peak temperature of 900-1000 °C for deep-sea pipeline steel, the base metal microstructure of which was the polygonal ferrite and acicular ferrite. Using V microalloying and low welding heat input could effectively decrease the softening of the HAZ fine-grained region, which was achieved by reducing the effective grain size, increasing the proportion of the dislocation substructures, and precipitating the nanoscale second-phase particles.
本文通过焊接热模拟研究了深海管线钢的焊接热循环过程。结合扫描电子显微镜、电子背散射衍射、透射电子显微镜和硬度测试，对热影响区（HAZ）软化区的微观组织演变、晶体学和第二相析出行为进行了表征和分析。结果表明，深海管线钢在峰值温度为900-1000°C的细晶区出现了HAZ软化，其母材微观组织为多边形铁素体和针状铁素体。采用V微合金化和低焊接热输入可有效降低HAZ细晶区的软化，这是通过减小有效晶粒尺寸、增加位错亚结构比例和析出纳米级第二相粒子来实现的。
