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采用Gleeble试验机研究了厚规格(22mm)X80管线钢的动态相变行为,得到了动态CCT曲线,对不同冷却工艺钢的显微组织、力学性能以及析出行为进行了系统的对比分析。结果表明,在40℃/s的高冷速条件下试验用钢的组织为细小的板条贝氏体(LB),相变终止温度达到约400℃;在超快冷工艺条件下钢卷的强度有所提高,韧性没有明显的变化;其显微组织中准多边形铁素体(QF)的比例下降,板条贝氏体(LB)的比例上升,M/A岛的比例有所降低;轧后快冷可抑制奥氏体中的析出,提高Nb在铁素体中的析出比例,使析出粒子尺寸更加细小,提高析出强化效果。
The dynamic phase transformation behavior of thick gauge (22mm) X80 pipeline steel was studied by Gleeble test machine, and the dynamic CCT curve was obtained. The microstructure, mechanical properties and precipitation behavior of different cooling steel were systematically contrastively analyzed. The results show that the microstructure of the test steel is fine lath bainite (LB) at a high cooling rate of 40 ℃ / s and the final temperature of transformation reaches about 400 ℃. The strength of the alloy increased, but the toughness did not change obviously. The proportion of quasi-polygonal ferrite (QF) in the microstructure decreased, the proportion of lath bainite (LB) increased and the proportion of M / A island decreased. Rapid cooling after rolling can inhibit the precipitation of austenite, increase the precipitation of Nb in the ferrite ratio, the precipitated particle size is more small, to enhance the precipitation strengthening effect.