（1. China Iron and Steel Research Institute Group，Beijing 100081，China 2. Shanghai First Machine Tool Factory Ltd.，Shanghai 201308， China 3. Fushun Special Steel Group， Fushun 113001， Liaoning， China）
Abstract：Custom 450 is a widely used maraging stainless steel， and the melting method and chemical composition variations in different batches have a significant effect on its properties. The composition and content of equilibrium phases at various aging temperatures were investigated by thermodynamic software Thermo-Calc， and the effects of C， N and Nb content were also discussed by analyzing room temperature mechanical properties together with thermodynamics. The results indicate that the equilibrium phases between 760～640 ℃ comprise α， γ， σ， NbNi3， FCC-Cu， M23C6， Nb（C，N） and a small amount of Z-CrNbN， Laves and χ； with the increasing of aging temperature， the UTS and YS decrease with the transition of equilibrium phases and the reduction of total mass fraction of precipitations； in addition， the fraction of carbides and carbonitrides increase and the fraction of intermetallic decrease with the increasing of C and N content；the increasement of Nb content shows little effect on the fraction of carbides and carbonitrides， but improves the fraction of intermetallics.
2017, Vol. 36 
