摘要
利用Thermecmastor-Z型热模拟试验机、Formastor-F型相变仪,结合光学显微镜、扫描电子显微镜及显微硬度计等设备系统研究了CSP热轧TRIP 600钢的连续冷却相变行为,获得了试验钢的动态及静态CCT曲线,探讨了形变和冷速对其相变行为的影响。研究结果表明:随着冷速的增加,试验钢中铁素体转变温度逐渐降低,体积分数不断减少,其转变温度范围为480~716℃;珠光体含量则先增加后减少,转变温度范围为519~647℃。当冷速大于2℃/s时,试验钢中已出现贝氏体转变,其含量随冷速的增加先增大后减小,转变温度范围为451~533℃。试验钢经变形后,钢中铁素体、珠光体及贝氏体转变温度范围往左上方移动,分别为550~760、539~708和478~550℃,而且相同冷速下钢中组织更加细小。此外,变形也会提高奥氏体的机械稳定性,抑制马氏体转变,使得马氏体开始转变温度Ms由418℃降至360℃。
The continuous cooling transformation behavior of hot rolled TRIP 600 steel produced by CSP process was investigated by means of Thermecmastor-Z thermal simulation testing machine,Formastor-F full automatic transformation instrument,OM,SEM and microhardness tester.The dynamic and static continuous cooling transformation(CCT)curves of the experimental steel were obtained.And the effect of deformation on phase transformation behavior was discussed.The results show that the temperature of austenite to ferrite and the volume fraction of ferrite gradually decrease with the increase of cooling rate.The transformation temperature range of the pro-eutectoid ferrite is 480-716℃.Meanwhile,the transformation temperature range of pearlite is 519-647℃,and the volume fraction of pearlite increases first then decreases with the increase of cooling rate.When the cooling rate is larger than 2℃/s,the bainite phase transformation will take place.The volume fraction of bainite also increases first then decreases with the increase of cooling rate.The transformation temperature range is 451-533℃.Moreover,it is found that the hot deformation of austenite will refine the microstructure and promote the ferrite,pearlite and bainite transformation,the corresponding transformation temperature ranges alter to 550-760,539-708 and 478-550℃,which move to the left top places in the dynamic CCT curve.In addition,the de-formation will also enhance the mechanical stability of austenite,leading to the inhibition of martensitic transformation and decrease the martensite starting temperature(Ms)from 418℃to 360℃.
引文
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