Effect of Ni and Mn on the Mechanical Properties of 22Cr Micro-duplex Stainless Steel

Abstract

The tensile properties of 22Cr–2Ni–4Mn–0.2N micro-duplex stainless steels with different Ni and Mn contents were investigated. Duplex stainless steels were vacuum induction melted and hot rolled, then annealed at 1,000–1,100 °C, at which temperature both the austenite and ferrite phases were stable. The volume fraction of the ferrite phase was markedly affected by the alloying elements of Mn and Ni; 1 wt% of Mn was equivalent to 0.4 wt% of Ni. All of the steels tested at room temperature showed the common strain-hardening behavior, while the steels tested at lower temperatures (−30 or −50 °C) showed a distinct inflection point in their stress–strain curves, which resulted from the transformation of the austenite to strain-induced martensite. The onset strain (ε ₀) of the inflection point in the stress–strain curve depended on the M _d30 value of the steel. Testing at lower temperatures resulted in smaller ε ₀ and consequently higher strengths and fracture strains (ε _f). The tensile behavior was examined from the perspective of austenite stability of the micro-duplex stainless steels with the different Ni and Mn contents.