开始冷却温度对X80管线钢组织与性能的影响

Effects of start cooling temperature on microstructure and properties of X80 pipeline steel

通过组织观察与力学性能测试，分析了X80管线用钢板轧后开始冷却温度（SCT）对其组织与性能的影响。研究结果表明，当开始冷却温度在680—785℃温度范围内时，不改变钢板的合金成分，钢板的强度指标不低于X70管线钢的要求，并具有良好的低温冲击性能，-20℃冲击吸收能量最低值不小于280J。开始冷却温度对钢板的显微组织有明显的影响，当开始冷却温度为785℃与750℃时，显微组织以贝氏体为主；当开始冷却温度为715℃与680℃时，显微组织为铁素体、贝氏体复合组织为主。组织中含有一定体积分数的铁素体，可以改善钢板的塑性，但会在一定程度上降低强度与冲击性能。

The effects of start cooling temperature（SCT） on microstructure and properties of the pipeline steel X80 were analyzed by means of microstructure observation and mechanical property test. When the SCT is in the range of 680-785 ℃, the strength of the tested pipeline steel can satisfy the requirement of X70 grade steel at least. The pipeline steel plates also show good toughness with impact energy higher than 280 J at -20 ℃. Microstructure observation shows that the SCTs have obvious effect on microstructure of the tested pipeline steel plates. When the SCTs are 785 ℃ and 750 ℃, the microstructure is bainite predominantly. When the SCTs are 715 ℃ and 680 ℃, the microstructure is ferrite and bainite. When the steel contained a certain amount of ferfite, the ductility of plate is improved, but strength and impact property will decrease to a certain extent.