1988 Volume 74 Issue 6 Pages 1052-1057
A thermo-mechanical treatment using reversion from deformation induced martensite to austenite was suggessted to obtain ultra fine grain structure in metastable austenitic stainless steels. And, in order to determine steel composition suitable for the thermo-mechanical treatment, influence of Cr and Ni content on deformation induced transformation from metastable austenite to martensite and successive reversion to austenite was investigated for low carbon Fe-Cr-Ni ternary alloys by means of magnetic analysis. The results are as follows :
(1) An amount of martensite induced by 90% cold rolling can be estimated by the Ni equivalent of (Ni+0.35Cr), where Ni and Cr represent mass% of these elements in the alloy. In case the Ni equivalent of (Ni+0.35Cr) is smaller than 16.0%, austenite almost transforms to martensite by 90% cold rolling. An amount of austenite retained in specimens is less than 10vol%.
(2) In case the Cr equivalent of (Cr-1.2Ni) is smaller than 4.0%, martensite induced by 90% cold rolling almost reverses to austenite by 873K-0.6 ks annealing. An amount of martensite retained in specimens is less than 10vol%.
(3) On alloys whose Ni equivalent of (Ni+0.65Cr) is larger than 19.7%, Ms temperature of reversed austenite is below the room temperature, if specimens are annealed 0.6ks at 873K after 90% cold rolling.
For the Fe-Cr-Ni ternary alloys which satisfy the three conditions of (1)-(3) for composition, therefore, we can obtain almost single structure of reversed austenite by the above thermo-mechanical treatment.
