加热温度对X80管线钢显微组织和低温韧性的影响

Effect of Heating Temperature on Microstructure and Low-Temperature Toughness of X80 Pipeline Steel

采用Gleeble-3500热模拟试验机模拟了X80弯管用管线钢的感应加热过程,即以20℃/s的速率将尺寸为10.5 mm×10.5 mm×80 mm和?10 mm×80 mm的X80钢试样加热至880、980、1080和1180℃,保温100 s后以10℃/s的速率冷却至室温。随后检测试样的微观组织和低温韧性。结果表明:当加热温度从880℃升高到980℃时,钢中粒状贝氏体增多,多边形铁素体减少,M/A组元平均尺寸减小,大角度晶界比例增多,低温韧性提高;1180℃加热的钢晶粒尺寸增大,大角度晶界减少,低温韧性恶化;980℃加热的钢微观组织由细小的粒状贝氏体铁素体和M/A组元组成,低温冲击吸收能量高达200 J,因此X80管线钢的感应加热弯制过程的加热温度宜为980℃。

Process of induction heating for bending of X80 steel pipe,that is,heating samples measuring 10.5 mm by 10.5 mm by 80 mm and 10 mm in diameter by 80 mm long at 20℃/s to 880,980,1080 and 1180℃for 100 s followed by cooling them at 10℃/s to room temperature,was simulated by a Gleeble-3500 thermal simulator.After this,the samples were tested for both microstructure and low-temperature toughness.The results showed that(a)as the heating temperature increased from 880 to 980℃,the granular bainite became more,the polygonal ferrite became less,the average size of M/A constituents decreased,the proportion of large-angle grain boundaries increased in the steel,and its low-temperature toughness became better;(b)the X80 steel heated at 1180℃exhibited larger grain size and less high-angle grain boundaries,leading to deterioration of the low-temperature toughness;and(c)the X80 steel heated at 980℃displayed microstructrure consisting of fine granular bainitic ferrite and M/A constituent,and its low-temperature impact absorbed energy was as high as 200 J,so the temperature at which X80 steel pipe is induction heated for bending is preferably 980℃.