Effect of aging of supercooled austenite on the mechanical properties of vanadium-containing steels

Abstract

1. The development of the processes of dispersion hardening of supercooled austenite leads to improved strength properties of steels 30Kh3N3MFB and 30KhNSMFB (with a slight reduction of ductility and real fracture stress) after hardening with isothermal holding in the range of subcritical temperatures and low tempering compared with the properties of these steels obtained by conventional hardening and the same tempering. 2. The uniform distribution of regions enriched with vanadium and carbon forming in the process of isothermal transformation of supercooled austenite and inherited by martensite, the possibility of their being cut by dislocations cause the uniform development of plastic deformation throughout the bulk of the steel without stress concentrations arising. Such a structural state ensures the possibility of attaining good strength properties. Then failure of steels 30Kh3N3MFB and 30KhNSMFB proceeds by the ductile micromechanism, but when the isothermal holding before quenching is extended to more than 10 min, the tendency of steel 30KhNSMFB to brittle failure increases; this may be due to the effect of silicon. 3. The good strength properties combined with satisfactory ductility and real fracture stress enable us to recommend the newly devised steels, especially 30Kh3N3MFB, as material for improtant machine parts.