对不同碳含量的4Cr5Mo2V钢进行淬火+回火热处理，研究了碳含量（0.35%，0.47%，0.71%，质量分数）对其显微组织、碳化物演变规律和热稳定性的影响。结果表明：在1 030 ℃淬火后，碳质量分数为0.35%的试验钢中无碳化物，碳质量分数为0.47%，0.71%的试验钢中存在颗粒状富钒MC型碳化物；淬火+回火处理后，试验钢中均析出M₂₃C₆碳化物，随碳含量增加，M₂₃C₆碳化物增多；进行热稳定性试验后，碳化物大量析出并发生粗化，随热稳定保温时间缩短和碳含量增加，试验钢硬度增大，热稳定性增强；碳含量增加能够提高试验钢的回火转变激活能，碳元素的固溶强化作用与MC型碳化物的析出强化作用是钢热稳定性增强的主要原因。

Quenching and tempering heat treatment of 4Cr5Mo2V steel with different carbon contents were carried out, and the effect of carbon content (0.35%, 0.47%, 0.71%, mass fraction) on its microstructure, carbide evolution and thermal stability was studied. The results show that There was no carbide in test steel with carbon mass fraction of 0.35% after quenching at 1 030 ℃, while granular vanadium-rich MC carbides existed in test steels with carbide mass fraction of 0.47% and 0.71%. M₂₃C₆ carbides were precipitated in test steels after quenching and tempering treatment, and the M₂₃C₆ carbides increased with the carbon content. After thermal stability test, a large amount of carbides were precipitated and coarsened, and with the thermal stability holding time decreasing and the carbon content increasing, the hardness and thermal stability of test steels increased. The increasing carbon content could improve the tempering transition temperature of test steels, the solid solution strengthening effect of carbon element and the precipitation strengthening effect of MC carbide were the main reasons for the enhancement of high temperature thermal stability of the steel.