Properties of Cr−Mn−Ni steels containing nitrogen at low temperatures

Summary

• 1. Cr−Mn−Ni steel containing nitrogen has high strength, ductility, and resilience at +20°C and −196°C after quenching.

• 2. The presence of up to 30% δ-ferrite in the structure of austenitic steel has no significant influence on the mechanical properties at temperatures down to −196°C.

• 3. The presence of large amounts of δ-ferrite (up to 15%) apparently has a positive effect because the tendency of austenite grains to increase in size during heating to quenching temperature is decreased.

• 4. The steel investigated is susceptible to embrittlement as the result of heating at 500–800°C. As the result of embrittlement, the strength, ductility, and resilience decrease.

• 5. The susceptibility of the steel to embrittlement as the result of tempering is determined by the carbon concentration. Steels cotaining 0.010% C do not become susceptible to embrittlement as the result of tempering.

• 6. The brittleness of austenitic Cr−Mn−Ni steel as the result of tempering at 700–800°C is induced by the precipitation of the M₂₃C₆ carbide along the grain boundaries.