ABSTRACT

Heat treatment is suggested as a means of improving microstructural properties for steels. Three API 5L X65 pipeline steels were subjected to a variety of quenching rates in brine and oil after heating up to 800°C. Thereafter, tempering was performed at a lower temperature of 550°C. Quenching the steels at a slower rate in oil generated refined microstructures consisting of mostly recovered and recrystallised grains with low dislocation cluster. On the other hand, faster quenching in brine created more deformed microstructures comprising of relatively higher local average misorientation. Such variations in structural properties reduced the hardness values obtained after the separate heat treatment procedures. It is notable that the quenching and tempering approach relieved the high stored energy imparted by the thermomechanical treatment, and helped to retained the key properties required for safe pipeline operation. In addition, the risks of HIC was minimised in the oil quenched pipeline steels.

摘要

建议将热处理作为改善钢显微组织性能的一种手段。三种 API 5L X65 管线钢在加热至 800°C 后，在盐水和油中进行各种淬火速率。此后，在550℃的较低温度下进行回火。在油中以较慢的速度淬火钢会产生精细的微观结构，主要由恢复和再结晶的晶粒组成，具有低位错簇。另一方面，在盐水中快速淬火会产生更多变形的微观结构，包括相对较高的局部平均取向差。这种结构特性的变化降低了单独热处理程序后获得的硬度值。值得注意的是，淬火和回火方法减轻了热机械处理赋予的高储存能量，并帮助保留了管道安全运行所需的关键特性。此外，油淬管线钢的 HIC 风险被降至最低。