以4Cr5Mo2V钢的化学成分为基础，制备了钒质量分数分别为0.15%，0.55%，1.25%的试验钢，并进行了1 040℃真空淬火和不同温度（540，620℃）回火处理，研究了钒含量对试验钢显微组织、硬度和冲击韧性的影响。结果表明：随着钒含量增加，回火处理后试验钢组织中的晶粒均发生细化，析出的VC型碳化物数量增加，晶粒细化和析出强化作用增强，导致硬度提高；650℃回火时的析出碳化物数量较多，导致基体发生软化，硬度相比于540℃回火有所下降。540℃回火后，钒含量为0.15%，0.55%试验钢发生韧性断裂，后者的冲击韧性更好，冲击吸收功达到265 J；当钒含量增至1.25%时试验钢发生脆性断裂，冲击吸收功仅为26 J。620℃回火后，3种试验钢均发生韧性断裂，冲击吸收功均在200 J以上。

On the basis of chemical composition of 4Cr5Mo2V steel, test steels with vanadium mass fractions of 0.15%, 0.55% and 1.25% were prepared, and then vacuum quenched at 1 040℃ and tempered at different temperatures (540, 620℃). The effect of vanadium content on the microstructure, hardness and impact toughness of the test steel was investigated. The results show that with the increase of vanadium content, the grains in all the tempered test steels were refined, and the number of precipitated VC-type carbides increased; the grain refinement and precipitation strengthening effects were enhanced, resulting in the increased hardness. The number of precipitated carbides after tempering at 650℃ was larger, leading to the softening of the matrix, therefore the hardness decreased compared with that tempered at 540℃. After tempering at 540℃, the test steel with vanadium content of 0.15% and 0.55% had ductile fracture, and the latter had better impact toughness, whose impact absorbing energy reached 265 J; when the vanadium content increased to 1.25%, the test steel had brittle fracture, and the impact absorbing energy was only 26 J. After tempering at 620℃, ductile fracture occurred in all three test steels, and the impact absorbing energy was greater than 200 J.