热基镀锌高扩孔钢的组织性能研究及其工业试制

热基镀锌是提高高扩孔钢耐腐蚀性能的重要手段之一。利用光学显微镜、扫描电镜、拉伸试验机和成形试验机等设备,研究了退火温度对铁素体贝氏体型高扩孔钢组织性能的影响,并进行了450 MPa级热基镀锌高扩孔钢的工业试制。结果表明:随退火温度由710 ℃升高至790 ℃,钢中渗碳体颗粒逐渐溶解,贝氏体体积分数先升高后降低,铁素体晶粒尺寸先增大后趋于稳定,屈服强度和抗拉强度先升高后降低,断后伸长率先降低后升高。不同退火温度下,试验钢的扩孔率均达到85%以上。工业试制产品具有良好的组织和性能均匀性,其横向屈服强度为396 MPa、抗拉强度为477 MPa、断后伸长率为27.5%、烘烤硬化值为42 MPa、扩孔率大于80%,各项性能均达到标准要求。

Study on microstructure and properties of hot-rolled galvanized high hole expansion steel and its industrial trial production

Hot-rolled galvanizing is one of the important means to improve the corrosion resistance of high hole expanding steel. The effect of annealing temperature on microstructure and properties of ferrite-bainite high hole expansion steel was studied by using optical microscope (OM), scanning electron microscope (SEM), tensile testing machine and forming testing machine. Moreover, the industrial trial production of 450 MPa grade hot-rolled galvanized high hole expansion steel was carried out. The results showed that with the increase of annealing temperature from 710 ℃ to 790 ℃, the cementite particles gradually dissolved, and the volume fraction of bainite first increased and then decreased. The grain size of ferrite first increased and then tended to be stable. The yield strength and tensile strength first increased and then decreased, and the total elongation first decreased and then increased with the increase of annealing temperature. Atdifferent annealing temperatures, the hole expansion rate of the tested steels was higher than 85%. The industrial trial products possessed good uniformity of microstructure and properties. The transverse yield strength was 396 MPa, the tensile strength was 477 MPa, the total elongation was 27.5%, the bake hardening value was 42 MPa, and the hole expansion rate was higher than 80%, all of which meet the standard requirements.