退火温度对440MPa级含铌型IF钢显微组织和力学性能的影响

以传统高强度IF钢为对比，用Gleeble-1500热模拟机研究了高C-高Nb 高强度IF钢再结晶行为，采用盐浴退火方法研究了退火温度对高C-高Nb高强度IF钢显微组织和力学性能的影响。实验结果表明，高C-高Nb 高强度IF钢再结晶完成温度比传统高强度IF钢约高20℃。再结晶完成后，高C-高Nb高强度IF钢铁素体晶粒长大倾向很小，晶粒尺寸比传统高强度IF钢明显细小。盐浴退火温度在870℃以上时，高C-高Nb高强度IF钢得到铁素体和贝氏体混合组织。为了保证高C-高Nb高强度IF钢得到较好的综合力学性能，退火温度控制在810℃-830℃为最佳。

Effect of Annealing Temperature on Microstructure and Mechanical Properties of High C-Nb IF Steel with a Strength Level of 440MPa

Compared with traditional high strength IF steel,the recrystallization behavior during annealing process of a high C-Nb high strength IF steel was studied by using a Gleeble-1500 simulator,The effect of annealing temperature on microstructure and mechanical properties of the high C-Nb IF steel was also investigated using salt annealing method. Results show that the recrystallization finishing temperature of the high C-Nb IF steel is 20℃ higher than that of traditional high strength IF steel.After completely recrystallized,the ferrite grains of the steel have a small growing tendency,and the average grain sizes are much finer than that of traditional IF steel, with the same heatments. For the high C-Nb IF steel,the mixture of ferrite and bainite is obtained when salt bath annealing temperature is above 870℃.In order to obtain good comprehensive mechanical properties,the optimum annealing temperature of the high C-Nb high strength IF steel should be controled between 810℃ and 830℃.