在相变仪上对20CrNi2Mo钢进行热模拟压缩试验，研究了其在840℃时不同变形量（0~50%）下的热压缩变形行为，并分析了它的显微组织和硬度。结果表明：20CrNi2Mo钢流变应力曲线呈现出明显的动态再结晶特征；当变形量达到10%时，会发生动态再结晶；随着变形量增加，晶粒逐渐细化，之后尺寸基本保持稳定，当变形量达到50%时，进入完全再结晶状态；随着变形量逐渐增大，马氏体板条束逐渐细化，残余奥氏体含量降低；当变形量由10%增至20%时，硬度显著增大，而后趋于稳定。

Thermal simulation compression experiment was carried out on 20CrNi2Mo steel by using phase change instrument, and the steel's thermal compressive deformation behavior at 840℃ under different deformations (0-50%) was studied. The steel's microstructure and hardness were also analyzed. The results show that the flow stress curve of 20CrNi2Mo steel exhibits obvious dynamic recrystallization characteristics. When the deformation amount reaches 10%, the dynamic recrystallization occurs. With the increase of the thermal compression deformation, the grain size is refined and subsequently can almost be kept stable. When the deformation amount reaches 50%, the specimen is completely recrystallized. In addition, with the increase of the thermal compression deformation, martensite is refined gradually, the content of residual austenite decreases. When the compression deformation changes from 10% to 20%, the hardness increases significantly, and then tends to stabilization.