采用Gleeble 3500型热模拟试验机对HG700汽车大梁钢进行单道次压缩试验，研究了其在变形温度950～1 150℃和应变速率0.01～5.00 s^-1条件下的流变应力行为；根据真应力-真应变曲线，采用线性回归方法建立该钢的流变应力本构模型，并进行了试验验证。结果表明：在高应变速率（1.00，5.00 s^-1）下，HG700汽车大梁钢的动态软化行为以动态回复为主，而在低应变速率（0.01，0.10 s^-1）下，HG700汽车大梁钢发生了明显的动态再结晶；变形温度的升高及应变速率的降低均会促进流变应力的降低，且会促进应力更早达到峰值；由构建的以变形温度、应变速率、真应变为变量的流变应力本构模型得到的预测结果与试验结果吻合良好，该模型可准确地预测HG700汽车大梁钢的流变应力。

The single-pass compression test of HG700 automobile beam steel was carried out using a Gleeble 3500 thermo-simulation machine, and the flow stress behavior at deformation temperatures of 950-1 150℃ and strain rates of 0.01-5.00 s^-1 was investigated. Based on true stress-true strain curves, the flow stress constitutive model of the steel was established by linear regression method, and was verified by tests. The results show that the dynamic softening behavior of HG700 automobile beam steel was dominated by the dynamic recovery at high strain rates (1.00,5.00 s^-1); the dynamic recrystallization of HG700 automobile beam steel occurred obviously at low strain rates (0.01,0.10 s^-1). Both the increase of deformation temperature and the decrease of strain rate would promote the reduction of flow stress and the early arrival of peak stress. The prediction results obtained by the flow stress constitutive model with the variables of deformation temperature, strain rate and true strain agreed well with the test results, indicating that the model could predict the flow stress of HG700 automobile beam steel accurately.