Effect of residual austenite and content of hardening elements on the mechanical properties of transition class stainless steels

Conclusions

• 1. The mechanical properties of the transition class stainless steel 03K12N5KM in the quenched condition are determined by its phase composition and do not depend to any significant extent on its Co and Mo contents.

• 2. For the same steel in the aged condition, Co and Mo additions have an effect if the austenite content is less than 50%. If it is higher than 50%, then the mechanical properties of the steel are the same as in the quenched condition.

• 3. The maximum aging effect was observed for the steel with an austenite content of 10–20%, with the Co content increased from 8–10% to 12%, and the Mo content increased from 4–5% to 6%. The ulitmate tensile strength of such a steel is 30% higher and the impact toughness is 3 times lower.

• 4. The ductility and impact toughness of the steel studied are determined by its strength, which depends to an equal extent on the phase compostion and on the total concentration of alloying elements in the hardening phase.

• 5. To obtain maximum impact toughness, the Co and Mo concentrations in the steel have to be restricted to the minimum value which provides the necessary strength level.