利用扫描电镜和拉伸、冲击试验研究了回火温度对不同冷速Q690钢的组织及力学性能的影响。结果表明,试验钢淬火态组织主要为板条贝氏体,经不同温度回火后,组织为板条贝氏体、粒状贝氏体、多边形铁素体的混合组织,不同回火温度下各组织所占比例不同;随着回火温度的升高,Q690钢的屈服强度趋于稳定,抗拉强度呈下降趋势,伸长率总体呈上升趋势;在500℃回火时,组织性能最优。与低冷速相比,高冷速钢强度较高,伸长率及冲击吸收能量较低。 The effects of tempering temperature on the microstructure and mechanical properties of Q690 steel with different cooling rates were studied by scanning electron microscopy and tensile and impact tests. The results show that the quenched microstructure of the test steel is mainly lath bainite. After tempering at different temperatures, the microstructure of the test steel is a mixed microstructure of lath bainite, granular bainite and polygonal ferrite, The proportion of the organization is different; with the increase of tempering temperature, the yield strength of Q690 steel tends to be stable, the tensile strength shows a downward trend, the elongation shows an overall upward trend; when tempered at 500 ℃, the microstructure and properties are optimal . Compared with the low cooling rate, the high cooling rate steel has high strength, low elongation and impact absorption energy.