热轧590MPa级车轮钢的奥氏体相变行为

 利用热力模拟试验技术，研究一种Nb-V-Ti复合微合金化C-Mn钢的奥氏体连续冷却相变行为，为低成本高性能热轧590MPa级车轮钢的控制轧制和控制冷却工艺制定提供必要的理论依据。研究表明：无形变条件下，铁素体转变存在的冷却速率范围为0. 5~5℃/s，珠光体转变存在的冷却速率范围为0. 5~2℃/s；形变条件下，铁素体转变存在的冷却速率范围为0. 5~25℃/s，珠光体转变存在的冷却速率范围为0. 5~10℃/s；不论是否存在形变，贝氏体转变存在于整个冷却速率范围(0. 5~30℃/s)；奥氏体区形变增加了奥氏体内部的缺陷密度，促进了非均匀形核的发生，故形变促进了铁素体转变；由于试验钢的碳的质量分数较低(＜0. 10%)，形变通过促进铁素体相变而间接促进珠光体相变；当贝氏体相变前无铁素体相变时，形变对贝氏体相变有促进作用；试验钢在实际热轧试验中冷却速率宜控制在20℃/s左右，卷取温度控制在550~650℃。

Austenitic Transformation Behavior of Hot-Rolled 590 MPa Grade Wheel Steel

By using thermal simulation experiment technology, austenitic continuous cooling transformation behavior of a Nb-V-Ti microalloying C-Mn steel was studied, which provided necessary theoretical basis for making control rolling and control cooling process of low-cost high-performance hot-rolled 590MPa grade wheel steel. The results indicate, on undeformed condition, ferritic transformation happens at cooling rate from 0. 5 to 5℃/s, and perlitic transformation happens at cooling rate from 0. 5 to 2℃/s. On deformed condition, ferritic transformation happens at cooling rate from 0. 5 to 30℃/s, and perlitic transformation happens at cooling rate from 0. 5 to 10℃/s. Whether there is deformation, bainitic transformation exists in whole cooling rates (0. 5-30℃/s). Deformation in austenitic zone increases the density of defects in austenite, which promots heterogeneous nucleation, so deformation could promote ferritic transformation. Due to the carbon content below 0. 1%, deformation indirectly promotes perlitic transformation by promoting ferritic transformation. When there was no ferritic transformation before bainitic transformation, deformation could promote bainitic transformation to some extent. In the actual hot rolling experiments, the cooling rate of experimental steel should control about 20℃/s, and the coiling temperature should be 550-650℃.