高钢级低温管线钢的韧化机制及控制技术

Toughening Mechanism and Controlling Technology for High-grade Low Temperature Pipeline Steels

针对高钢级管线钢在低温服役环境条件下韧性断裂止裂控制难题,分析了高钢级管线钢的低温断裂机理,明确了影响DWTT性能的两个重要因素。通过热模拟实验,讨论了提高DWTT性能的控制技术。采用粗轧再结晶区低温段大变形,增加粗轧阶段总累积变形量,及将精轧温度降低到临近Ar3的温度范围内,并施加足够的累积变形量,可获得一定数量的超细晶多边形铁素体,将板材心部的平均有效晶粒尺寸细化到2.5μm,使-60℃下DWTT断口剪切面积达到100%,为大口径高钢级管线钢的研发生产提供理论依据和技术参考。

In view of the problem on stopping ductile fracture of high grade pipeline steels in service at low temperature by direct controlling,the low temperature fracture mechanism of high grade pipeline steels was analyzed.Two important factors influencing the DWTT performance were identified.The control technologies for improving the performance of DWTT were discussed through the thermal simulation experiment.By taking these measures such as carrying out large deformation reduction at low temperature in rough rolling recrystallization zone to increase the total cumulative deformation reduction at rough rolling stage,lowering the finishing temperature to as close as the temperature of Ar3 and exerting sufficient cumulative deformation reduction,a certain amount of ultrafine polygon ferrite can be obtained,the average effective grain sizes in the core of steel plates can be refined to 2.5μm,and the shearing area of DWTT fracture can reach to 100%at-60℃,which provided the theoretical basis and technical reference for development and production of heavy-calibre high grade pipeline steels.