HQ100热轧高强钢连续冷却相变研究

Research on continuous cooling transformation of HQ100 hot rolled high strength steel

在Gleeble3800热模拟试验机上,测定了HQ100热轧高强钢的动态CCT曲线,并通过光学显微镜和透射电镜观察试验钢在不同冷却条件下的显微组织形貌,以及采用显微硬度法检测其维氏硬度。结果表明：在0.1～60℃/s冷速范围内,试验钢存在珠光体、贝氏体、马氏体转变区;随着冷速的增加,试验钢硬度增加;冷速高于10℃/s时,试验钢屈服强度达到900 MPa以上,满足高强度工程机械用钢的要求;组织中存在大量50nm以下含Ti、V、Mo元素的析出相粒子,其强化机理以沉淀强化和相变强化为主。

CCT curves of HQ100 hot rolled steel were determined by using Gleeble3800 thermal simulator.Microstructures of this steel under different cooling conditions were investigated by means of optical microscope and transmission electron microscopy.Vickers-hardness was detected by micro-hardness method.The results showed that at the range of 0.1-60 ℃/s cooling rates,there were transformed zones of pearlite,bainite and martensite appearing in test steels.Meanwhile,with the cooling rate increasing,the vickers-hardness was increased obviously.The yield strength of test steel may reach more than 900 MPa at the range of10-30 ℃/s cooling rate that could meet the requirements of engineering machine.A number of precipitates with the size under50 nm including Ti,V,Mo elements were found.The test steel obtained high strength mainly by precipitation strengthening and phase transformation strengthening.