微合金低碳Mn-B钢连续冷却转变及控轧控冷的显微组织与力学性能

Continuous Cooling Transformation, Microstructure and Mechanical Properties of Controlled Rolling and Accelerated Cooling of Microalloyed LowCarbon Mn-B Steel

采用膨胀法结合金相分析建立微合金低碳Ｍｎ－Ｂ钢的动态ＣＣＴ曲线，在二辊实验轧机和控冷设备上模拟热连轧、快速冷却及卷取工艺。实验结果表明：变形后以１０～２５℃／ｓ的速度冷却，获得针状铁素体（ＡＦ）＋多边形铁素体（ＰＦ）组织。轧后以平均冷速８℃／ｓ快冷至６２０℃装炉缓冷模拟卷取，抗拉强度达到４９０ＭＰａ，显微组织由多边形铁素体＋针状铁素体和少量珠光体构成，具有良好的冷成形性和较低的屈强比。

The continuous cooling transformation (CCT) diagram for a microalloyed lowcarbon Mn-B steel was constructed by means of the combination of dilatometry and metallography. The simulation of controlled rolling, accelerated cooling and coiling processes was carried out on a 2high experimental mill and controllable cooling system. AF+PF is obtained at the cooling rates ranging from 10 to 25 ℃/s. By accelerated cooling at rate of 8 ℃/s to 620 ℃ and slow cooling in furnace to simulate the coiling process, microstructure containing PF+AF+P, good bending formability, low ratio of yield strength to tensile strength were obtained for microalloyed lowcarbon Mn-B steel with tensile strength of 490 MPa.