钒的添加对S30432奥氏体耐热钢影响的研究

Study on the Influence of Vanadium on S30432 Austenitic Heat-resisting Steel

本工作研究了添加0.18%的V对S30432奥氏体耐热钢的影响。对比了不含V和含V的S30432钢650℃持久断裂时间,测量了固溶态和持久断裂后试样的硬度,利用OM、SEM、TEM和Thermo-Calc软件研究了V对S30432钢析出相的影响,分析了V的加入对S30432耐热钢强度改善的机理。结果表明,在S30432钢中添加0.18%V,延长了其650℃持久断裂时间并提高了硬度。含V的S30432钢不仅晶粒变细,而且二次MX相数量更多。特别是,含V的S30432钢存在大量细小的Z相(Cr(Nb,V)N)。这是由于V(C,N)溶解温度较Nb(C,N)低,V的添加促进了MX相的溶解,促使含V的S30432钢优先析出细小的Z相。Z相的析出强化是含V钢硬度和强度增加的主要原因。

The effect of 0.18%V addition on S30432 austenitic heat-resistant steel was studied in this paper.Creep rupture time at 650℃and hardness before and after crept at 650℃of V-free and V-containing steels were compared.OM,SEM,TEM and Thermo-Calc software were used to study the influence of 0.18%V on the precipitates in S30432 steel.The mechanism of improving strength of V-containing S30432 heat-resistant steel was also analyzed.The results show that the addition of 0.18%V to S30432 steel leads in the increase of creep rupture time at 650℃and hardness.Not only the grains become finer,but also there are more secondary MX particles in V-containing S30432.In particular,a large number of fine Z-phase(Cr(Nb,V)N)precipitate in V-containing S30432 steel.Because the solution temperature of V(C,N)is lower than Nb(C,N),the addition of V accelerates the dissolution of more MX and promotes the precipitation of fine Z-phase in V-containing S30432 steel.The precipitation strengthening of Z-phase is the main reason to improve the hardness and strength of V-containing S30432 steel.