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为了实现非调质钢轴类件楔横轧热成形后控制冷却过程性能优化和节能减排,采用物理模拟手段对热变形后的非调质钢40MnV进行了连续冷却和等温冷却相变动力学研究。首先采用膨胀仪测定试验钢临界点Ac1、Ac3温度,然后利用Gleeble 3500热模拟机测定了40MnV钢的冷却过程相变动力学转变曲线,并分析了转变产物的显微组织。结果表明:冷却速度增大将减小铁素体的晶粒尺寸,同时也减小铁素体的体积分数;奥氏体晶粒尺寸和钒都对转变温度有影响,但在相变区快冷时奥氏体晶粒尺寸起主要作用,且晶粒尺寸减小将提高转变温度;相变区冷却速度为3℃/s时相变生成贝氏体,且其形态为典型的上贝氏体,而相变区冷却速度为6℃/s时对应转变的组织是马氏体;随着冷却速度的增加,析出过程中V(C,N)的数量增加,最大颗粒尺寸减小;等温冷却中V(C,N)析出物的形态为圆形和方形且数量很少,析出物的颗粒尺寸随转变温度的降低而减小。
In order to optimize the performance of control cooling process and reduce energy consumption and emission after thermoforming of non-quenched and tempered steel shaft cross-section hot rolling, physical simulation was used to study the kinetics of continuous cooling and isothermal cooling transformation of non-quenched and tempered steel 40MnV after hot deformation . The dilatometer was used to measure the temperature of Ac1 and Ac3 at the critical point of the test steel. The phase transition kinetics curves of 40MnV steel were measured by Gleeble 3500 thermal simulator. The microstructure of the products was analyzed. The results show that: the cooling rate increases will reduce the ferrite grain size, but also reduce the volume fraction of ferrite; austenite grain size and vanadium have an impact on the transition temperature, but the rapid cooling in the phase transition zone When austenite grain size plays a major role, and the grain size decreases will increase the transition temperature; phase transformation zone cooling rate of 3 ℃ / s phase transformation to generate bainite, and its morphology is typical upper bainite , While the corresponding transformation microstructure is martensite at the cooling rate of 6 ℃ / s in the phase transition zone. As the cooling rate increases, the amount of V (C, N) increases and the maximum particle size decreases during isothermal cooling The shape of V (C, N) precipitates is round and square with a small number. The size of precipitates decreases with decreasing transformation temperature.