控轧控冷工艺对900 MPa级热轧带钢组织和性能的影响

通过动态CCT曲线测试和实验室控轧控冷试验,分析了900 MPa级热轧带钢连续冷却过程中的相变过程以及不同卷取温度下显微组织、析出相和力学性能的关系。试验结果表明:随着冷却速度提高,显微组织中多边形铁素体比例下降,贝氏体组织比例升高,冷速大于15℃/s时,显微组织全部为贝氏体;随着卷取温度升高,显微组织中针状铁素体比例下降,多边形铁素体比例升高;当卷取温度为600℃时,组织为铁素体+少量珠光体,此时析出相细小弥散,可获得抗拉强度达到1 000 MPa,延伸率17%的热轧产品。

Effects of Controlled Rolling and Cooling Technology on Microstructure and Performance of 900 MPa Grade Hot-rolled Strip Steel

Through measurement of dynamic CCT curve and experiment of controlled rolling and cooling in laboratory for 900 MPa grade hot-rolled strip steel,phase transformation during continuous cooling process and relationship of microstructure,precipitate and mechanical properties at various coiling temperatures were investigated.CCT measurement show that with the increase of cooling rate,the volume fraction of polygonal ferrite decreases and the fraction of bainite increases,when cooling rate exceeds 15 ℃/s,the microstructure fully consists of bainite.With the increase of coiling temperature,the volume fraction of acicular ferrite decreases and that of polygonal ferrite increases;when coiling temperature reaches 600 ℃,microstructure is composed of ferrite and reduced pearlite,and precipitates are finely dispersed,and the resulting hot-rolled strip steel with 1 000 MPa of tensile strength and 17％ of elongation can be achieved.