采用Gleeble-3500型热模拟试验机对FV520B马氏体不锈钢进行了单道次等温热压缩试验，研究了该不锈钢在变形温度为850~1 150℃和应变速率为0.005~5.000 s^-1条件下的热变形行为，根据应力-应变曲线并基于Zener-Hollomon参数和Arrhenius双曲正弦方程，建立了该不锈钢在高温压缩时的本构方程，并对该本构方程进行了修正和试验验证。结果表明：FV520B马氏体不锈钢的流变应力随着变形温度的升高或应变速率的减小而降低；在0.005 s^-1、1 000~1 150℃或0.050~5.000 s^-1、1 075~1 150℃条件下，该不锈钢发生了较明显的动态再结晶；在0.005 s^-1、850℃，5.000 s^-1、850℃和5.000 s^-1、925℃条件下，由建立的本构方程计算得到的流变应力与试验值存在较大的误差；对本构方程进行修正之后，流变应力的预测值与试验值的相关系数为0.997 88，平均相对误差为2.225%，修正后的本构方程可以准确地预测该不锈钢的热变形流变应力。

The hot deformation behavior of FV520B martensitic stainless steel was investigated by single pass isothermal compression test on the Gleeble-3500 thermal simulation machine at the deformation temperatures of 850-1 150℃ and stain rates of 0.005-5.000 s^-1. According to the stress-strain curves and on the basis of Zener-Hollomon parameter and the Arrhenius hyperbolic-sine equation, the constitutive equation of the stainless steel during high temperature compression was established, and was corrected and verified by experiments. The results show that the flow stress of FV520B martensitic stainless steel decreased with the increase of deformation temperature or the decrease of strain rate. The dynamic recrystallization occurred obviously in the stainless steel at 0.005 s^-1, 1 000-1 150℃ and 0.050-5.000 s^-1, 1 075-1 150℃. The errors between the predicted flow stresses by the constitutive equation and the experimental values were relatively large under the conditions of 0.005 s^-1, 850℃ and 5.000 s^-1, 850℃ or 925℃. After the constitutive equation was corrected, the correlation coefficient between the predicted flow stress and the experimental value was 0.997 88, and the average relative error was 2.225%. The corrected constitutive equation predicted the hot deformation flow stress of the stainless steel accurately.