(S155)Re-evaluation of effects of carbon and nitrogen on Md30 in metastable austenitic steels

摘要

Md30 is one of the parameter to evaluate the mechanical stability of metastable austenitic stainless steels, and defined as the temperature at which 50 vol.% of martensite is formed at a true tensile strain of 0.3. C and N, which are interstitial elements, are known to exhibit remarkable stabilizing and strengthening effects in austenite. Previously, the effect of C on Md30 is known to be identical to that of N, as shown by Angel's1) or Nohara's2) equation. On the other hand, we found that the effect of C on the mechanical stability at ambient temperature is higher than that of N in Fe-18%Cr-8%Ni supplemented with 0.1% of C and N separately3). That is, Angel and Nohara et al. could not distinguish the effects of C and N. In this study, we measured Md30 in 18%Cr-8%Ni steels supplemented with up to 0.2% C and N separately in order to assess the individual effects of C and N on Md30.