控轧控冷工艺对低焊接裂纹敏感性高强钢Q800CFE屈强比的影响

Effect of controlled rolling and controlled cooling process on the yield ratio of high strength steel Q800CFE with low welding crack sensibility

以低焊接裂纹敏感性高强钢Q800CFE为试验材料,测试了该低碳贝氏体钢变形奥氏体的连续冷却转变行为,制定了CCT曲线。采用不同控轧控冷工艺进行了Q800CFE钢的生产试验,分析了不同终轧温度、终冷温度、冷却速度对Q800CFE组织性能的影响规律。结果表明,提高终轧温度,晶粒较粗大,可降低屈强比(YR);随着终冷温度从200℃升高至520℃,屈服强度(YS)、抗拉强度(TS)均下降,屈强比先升高后降低,在终冷温度为440℃时达到峰值(0.924);随着冷却速度从24℃/s增加到48℃/s,YS、TS、YR均升高,其中当冷却速度小于32℃/s时,增加幅度较大,当冷却速度大于32℃/s时,增加幅度较小。

Continuous cooling transformation （CCT） behavior of a Q8OOCFE high strength steel with low welding crack sensibility was studied and the CCT diagram was constructed. Effect of controlled rolling and controlled cooling process parameters, i.e. finish rolling temperature, finish cooling temperature and cooling rate, on the microstructure and mechanical properties was investigated by industrial trials. The result indicates that the yield ratio（YR） can be lowered by increasing the finish rolling temperature due to a larger grain size; as the finish cooling temperature increases from 200 to 520 ℃, the yield strength （ YS ） and tensile strength （TS） both decrease, but the YR increases first and then decreases at the peak value of 400 ℃ ; with the cooling rate increases from 24 to 48 ℃/s, the YS, TS and YR all increase, but to a smaller extent when the cooling rate is higher than 32 ℃/s.