回火温度对中碳合金钢4Cr5MoSiV1Nb组织和性能的影响

为了优化合金性能,研究了回火温度对中碳合金钢4Cr5MoSiV1Nb组织和性能的影响。试验结果表明,4Cr5MoSiV1Nb合金钢的二次硬化温度区间为300～550℃,峰值出现在550℃,此时硬度值为56.3HRC,同时伴有冲击韧性的显著降低,冲击韧性降低的原因是合金钢回火时含铬铬的细短棒状合金渗碳体在晶界析出,可以推测减少淬火合金钢中铬的偏析将会减少晶界析出,提高冲击韧性。微量铌的加入形成了(V,Nb)C强化相颗粒。合金在250～350℃回火综合性能最佳,可以达到冲击韧性15 J/cm^2、硬度55HRC以上。

Effect of tempering temperature on microstructure and properties of medium carbon alloy steel 4Cr5MoSiV1Nb

The effect of tempering temperature on microstructure and properties of medium carbon alloy steel 4Cr5MoSiV1Nb was studied in order to optimize properties of the alloy. The results show that the secondary hardening temperature of 4Cr5MoSiV1Nb alloy steel ranges from 300-550 ℃ and the peak value appears at 550 ℃. The hardness of 4Cr5MoSiV1Nb steel reaches 56.3HRC and meanwhile，its impact toughness decreases markedly. The reason for the decrease of impact toughness is that the fine and short bar cementite containing Cr precipitates at grain boundary during tempering. It can be speculated that reducing the segregation of Cr in its parental quenched alloy steel will reduce the precipitation at grain boundaries of the tempered alloy and improve its impact toughness. The addition of trace Nb forms strengthening particles of （V，Nb）C phase. The alloy tempered at 250-350 ℃ can reach the best comprehensive properties higher than 15 J/cm2 impact toughness and 55HRC hardness.