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利用DIL805A/D高精度差分膨胀仪,通过线膨胀行为测量获得相关动力学信息,结合冷却后的组织特征,研究了T91钢不同冷却速度(2～6000℃/min)下过冷奥氏体的相变过程和产物,确定了该钢组织转变的临界冷却速度以及淬火速率对马氏体转变点及组织的影响,绘制了连续冷却转变曲线。研究表明:T91钢的连续冷却过程中只存在铁素体和马氏体转变区,10℃/min为马氏体转变的临界冷却速度。不同淬火速率对T91钢马氏体开始转变温度有较大的影响,它不同于随冷速增加而相变点升高的经典理论。淬火速率通过碳原子气团、内应力的形成来影响过冷奥氏体状态,从而影响相变点;随淬火速度的增加,过冷奥氏体转变后的组织呈细化趋势。
Using DIL805A / D high precision differential dilatometer, the relevant dynamic information was obtained through the measurement of linear expansion behavior. Combined with the microstructure characteristics after cooling, the effects of supercooled austenite at different cooling rates (2 ~ 6000 ℃ / min) Phase transition process and the product, the critical cooling rate and quenching rate on the martensitic transformation point and the microstructure of the steel were determined, and the continuous cooling transformation curve was drawn. The results show that there are only ferrite and martensite transformation zones in the continuous cooling process of T91 steel, and the critical cooling rate of martensite transformation at 10 ℃ / min. Different quenching rates have a great influence on the martensitic transformation temperature of T91 steel, which is different from the classical theory that the transformation point increases with the increase of cooling rate. The quenching rate affects the state of undercooled austenite through the formation of carbon clusters and internal stress, which affects the transformation point. With the increase of quenching rate, the microstructure of the structure after the subcooling of austenite is refined.