某CSP线生产热轧双相钢DP600终轧温度的研究

Study on Finishing Temperature of Hot Rolled Dual-phase Steel DP600 Produced by A CSP Line

针对某CSP短流程生产线的特点,设计了中温卷取型600 MPa级热轧双相钢的化学成分,测定了其动态CCT曲线。研究了终轧温度对热轧板的显微组织与力学性能的影响。结果表明:终轧温度在821~858℃变化时,热轧板的显微组织均由铁素体和马氏体组成。随着终轧温度的升高,铁素体的体积分数略微增大,由84.60%增大到85.14%,而铁素体的晶粒尺寸增大较为明显,由5.07μm增大到5.97μm。不同终轧温度下,抗拉强度均达到600 MPa以上,伸长率均在24.0%以上,应力-应变曲线均表现为连续屈服。但随着终轧温度的升高,热轧板的屈服强度呈现降低趋势,当终轧温度达到858℃时,热轧板的屈服强度(322 MPa)未达到DP600钢的性能要求(325 MPa以上)。结合某CSP线的特点及DP600钢的性能要求,生产DP600钢合理的终轧温度规程应为(830±15)℃。

The chemical composition of 600 MPa grade hot-rolled dual phase steel coiled at medium temperature was designed according to the characteristics of a CSP short process production line,and the dynamic CCT curve of the steel was measured.The effect of finishing temperature on the microstructure and mechanical properties of hot rolled plates was studied.The results show that when the finishing temperature changes in 821-858℃,the microstructure of the hot rolled plate is composed of ferrite and martensite.With the increase of finishing rolling temperature,the volume fraction of ferrite increases slightly from 84.60%to 85.14%,while the grain size of ferrite increases obviously from 5.07μm to 5.97μm.Under different finishing temperatures,the tensile strength reaches more than 600 MPa,the elongation is above 24.0%,meanwhile the stress-strain curves all show continuous yield.But with the increase of the finishing temperature,the yield strength of the hot rolled plates tends to decrease,when the finishing temperature reaches 858℃,the yield strength of the hot rolled plate(322 MPa)is lower than the performance requirement(more than 325 MPa)of DP600 steel.The reasonable finishing temperature specification for DP600 steel should be(830±15)℃ according to the characteristics of CSP line and the performance requirement of DP600 steel.