980 MPa级冷轧双相钢的热处理工艺优化

利用Gleeble-3500热模拟试验机、光学显微镜和拉伸试验机分析研究了连续退火工艺中均热温度、缓冷温度和过时效温度对DP980钢力学性能及组织的影响。结果表明:随着均热温度的升高DP980钢组织中马氏体含量逐渐增加,规定塑性延伸强度和抗拉强度也随之提高,经分析选取780 ℃为最优均热温度。研究缓冷温度对DP980双相钢力学性能的影响,结合连退产线设备控制能力,选取670 ℃为最优缓冷温度。此外,过时效温度对DP980钢规定塑性延伸强度具有较大调整幅度,能够显著降低其屈强比,随着过时效温度的升高,DP980钢组织中马氏体含量基本不变并伴有少量的碳化物析出,能够降低马氏体的强度即改善双相钢塑性。最终确定均热温度780 ℃、缓冷温度670 ℃和过时效温度320 ℃的最优工艺参数。

Optimization of heat treatment process of 980 MPa cold-rolling dual phase steel

Effects of soaking temperature, slow cooling temperature and overaging temperature during continuous annealing on mechanical properties and microstructure of DP980 steel were investigated by means of Gleeble-3500 annealing simulator, optical microscope and tensile testing machine. The results indicate that the martensite content of the DP980 steel is increased with the increase of soaking temperature, which leads to the enhancement of yield strength and tensile strength accordingly. The optimal soaking temperature is 780 ℃. Effect of slow cooling temperature on mechanical properties of DP980 steel is investigated based on the control capability of equipment, and 670 ℃ is selected as the optimal temperature. Besides, the overaging temperature has been possessed large adjustment range on yield strength of DP980 steel, which can reduce the yield ratio significantly. With the increase of overaging temperature, the martensite content is remained stable and a little carbide is precipitated, which reduces the martensite strength and improves the plasticity of DP980 steel. The optimal parameters of soaking temperature, slow cooling temperature and overaging temperature are 780, 670, 320 ℃, respectively.