X80管线钢二次热循环的连续冷却转变行为及贝氏体相变动力学  

Continuous Cooling Transformation Behaviors and Bainite Transformation Kinetics of X80 Pipeline Steel During the Second Thermal Cycle

作　　者：唐丽[1] 尹立孟[1] 王金钊[1] 刘成[1] 王学军[2] TANG Li;YIN Limeng;WANG Jinzhao;LIU Cheng;WANG Xuejun(School of Metallurgy and Materials Engineering,Chongqing University of Science and Technology,Chongqing 401331;Sichuan Oil and Gas Construction Engineering Co.,Ltd,Chengdu 610041)

机构地区：[1]重庆科技学院冶金与材料工程学院,重庆401331 [2]四川石油天然气建设工程有限责任公司,成都610041

出　　处：《材料导报》2019年第18期3119-3124,共6页Materials Reports

基　　金：国家自然科学基金(51674056)~~

摘　　要：利用高温相变仪DIL805A/D实现了X80管线钢的焊接热模拟实验,采用OM、SEM、TEM和显微硬度计来获得不同连续冷却速率下X80管线钢的显微组织和硬度,进而建立了二次热循环下热影响区的连续冷却转变曲线(SHCCT曲线),并研究贝氏体相变机制及相变动力学。此外,还构建了相变点-冷却速率之间的回归模型,获得了高拟合精度的Bs、Ms、Tf与冷却速率v之间的定量关系。结果表明:在二次热循环不同冷却速率下,X80的组织依次为:先共析铁素体(0.5~1℃/s)、贝氏体(5~50℃/s)、板条马氏体(大于75℃/s);当冷却速率小于100℃/s时,显微硬度随冷却速率增大而增加,当冷却速率超过100℃/s后,硬度维持在332.5HV1左右;贝氏体相变局部激活能随其体积分数(fb)的增加而减小,平均激活能约为108.6kJ/mol,且贝氏体转变的主导生长机制是一维生长和二维生长。Based on the welding thermal simulation of X80 pipeline steel by using DIL805A/D quenching dilatometers,the microstructure and hardness of X80 pipeline steel with different continuous cooling rates were obtained by means of OM,SEM,TEM and micro-hardness testing,and continuous cooling transformation curves of X80 heat-affected zone(SHCCT curves)during the second thermal cycle was determined.The bainite transformation mechanism and bainite transformation kinetics were studied by means of kinetic analysis.In addition,the regression model of phase transformation point-cooling rate was established,also,quantitative equations between the phase transformation point(including the start temperature for bainite transformation Bs,the start temperature for martensite transformation M s,the finish temperature for phase transformation Tf)and the cooling rate with high fit degree was obtained by regression calculation.The results show that the most dominant microstructure of X80 pipeline steel after the second thermal cycle at different cooling rates appears successively such as,proeutectoid ferrite(0.5-1℃/s),bainite(5-50℃/s),lath martensite(75℃/s and above cooling rates),especially.When the cooling rate is less than 100℃/s,the hardness increases with the increase of cooling rate.On the contrary,the hardness remains at about 332.5HV 1 when the cooling rate exceeds 100℃/s.As the volume fraction of bainite transformation(fb)increases,the local activation energy decreases and the average energy is about 108.6 kJ/mol,and the dominating mechanism of bainite transformation is the two-dimensional and one-dimensional growth.

关 键 词：X80管线钢 二次热循环 显微组织 SHCCT曲线 相变动力学 

分 类 号：TG113[金属学及工艺—物理冶金] TG115[金属学及工艺—金属学]