Ti-V微合金化热轧高强钢的相变规律及组织性能

Microstructure, mechanical properties and phase transformation behavior of Ti-V microalloyed high-strength hot-strip steel

为进一步提升热轧高强钢的性能,利用热模拟试验机、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HR-TEM)等设备系统研究了Ti-V微合金热轧带钢连续冷却相变规律、组织和性能随卷取温度的变化规律及强化机理。结果表明,当冷却速度低于1℃/s时,试验钢中的组织为铁素体和珠光体。当冷却速度为5~30℃/s时,基体组织由铁素体、珠光体和贝氏体组成,贝氏体相变开始温度介于580~600℃。当冷却速度增加至50℃/s时,试验钢中的奥氏体全部转变为贝氏体。此外,对不同卷取温度下试验钢的组织和性能研究表明:随着卷取温度的降低,试验钢的强度降低,塑性基本不变。当卷取温度为650℃时,力学性能最佳,其抗拉和屈服强度分别为716和653 MPa,断后伸长率达到21.3%,主要是由于晶粒细化和沉淀强化所致。

In order to further improve the properties of high-strength hot-strip steel,the transformation behavior under continuous cooling,the effect of coiling temperature on microstructure and mechanical properties and strengthening mechanisms of Ti-V microalloyed high-strength hot-strip steel were systematically investigated by using thermal simulation testing machine,SEM and HR-TEM.The results show that the microstructure of experimental steel consists of ferrite and pearlite when the cooling rate is less than 1℃/s.With the cooling rates ranging from 5 to 30℃/s,the matrix consists of ferrite,pearlite and bainite,and the bainitic transformation occurs between 580 and 600℃.When the cooling rate increases to 50℃/s,the austenite transfers to bainite totally.Furthermore,the study on the effect of coiling temperature on the microstructure and mechanical properties of experimental steel has shown that the strength decreased with the decreasing coiling temperature,but the total elongation basically remained constant.When the coiling temperature is 650℃,the experimental steel possesses optimal mechanical properties mainly attributed to the grain refinement and precipitation hardening whlie the tensile strength and yield strength were 653 and 716 MPa,respectively,and the elongation reaches 21.3%.