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采用热模拟技术对X100管线钢在连续冷却转变下的显微组织的变化规律进行了研究。深入讨论了X100管线钢的CCT曲线及其在不同冷却条件下的相变规律。结果表明,X100管线钢的组织为GB(Granular Bainite)、QF(Polygonal Ferrite)、M/A构成的复相组织,且各相比例和形态对性能影响较大。发现随着冷却速度的提高,在连续冷却转变组织中依次出现多边形铁素体(QF)、粒状贝氏体(GB)、贝氏体铁素体(BF)、板条马氏体(LM)。静态CCT在5~20℃/s冷速区间可得到GB、BF、M/A构成的复相组织,动态CCT的冷却速度大于20℃/s才能得到相应的组织。研究结果表明:高温变形能够扩大相变温度区间,细化相变后晶粒尺寸。高温变形对铁素体相变影响较大,而对贝氏体相变影响较小。
The microstructure evolution of X100 pipeline steel under continuous cooling transformation was studied by using thermal simulation technology. The CCT curve of X100 pipeline steel and its phase transformation under different cooling conditions are discussed in depth. The results show that the microstructures of X100 pipeline steel are complex phase composed of GB (Granular Bainite), QF (Polygonal Ferrite) and M / A, and the proportion and morphology of each phase have a great influence on the performance. It is found that polycrystalline ferrite (QF), granular bainite (GB), bainitic ferrite (BF) and lath martensite (LM) appear in the continuous cooling and transformation microstructure as the cooling rate increases. . In static CCT, the complex microstructure consisting of GB, BF and M / A can be obtained in the cold temperature range of 5 ~ 20 ℃ / s. The cooling rate of dynamic CCT is higher than 20 ℃ / s to get the corresponding microstructure. The results show that high temperature deformation can enlarge the phase transition temperature range and refine the grain size after phase transformation. High temperature deformation has a great effect on the ferrite transformation, but has little effect on the bainite transformation.