High Strength Stainless Austenitic CrMnCN Steels – Part I: Alloy Design and Properties

Abstract

Generally the strength of stainless austenitic steels does not live up to their good corrosion resistance. Solid solution hardening by interstitial elements is a means of raising the strength, but is used only moderately because of poor weldability, which, however, is not required in various applications. The solubility of nitrogen is high in stainless austenite of steels with 18 mass% of Cr and Mn each, but low in the melt. Carbon reveals the opposite behaviour. Instead of producing high nitrogen steels by pressure metallurgy, about 1 mass% of C+N is dissolved in the melt at ambient pressure. The new cost‐effective C+N steel reaches a yield strength of 600 MPa, a true fracture strength above 2500 MPa and an elongation above 70 %. Conduction electron spin resonance revealed a high concentration of free electrons. Thus, the ductile metallic character of the C+N steel is enhanced, explaining the high product of strength times toughness. The high interstitial content requires rapid quenching to avoid an embrittling precipitation and respective intercrystalline corrosion.