In previous reports (Tetsu-to-Hagane Vol.45.(1959), No.1, p.1276; Vol.46, (1960), No.3 and 5, p.375 and 566), the authors reported the effect of Nb, Ti, Mo and W on properties of 18Cr-12 Ni austenitic stainless steels. This report concerned the effect of V, Al and Zr on.aging behaviour, microstructure, precipitates, tensile strength at various temperatures and creep rupture strength of the same steel.
The following results were oftained:
1) The steels were hardened during aging by precipitation of VC, Al3Ni and σ phase.
The steels containing Zr were scarcely hardened during aging.
2) Grain size became finer in proportion to the content of the elements.It was observed that the precipitates were VS, VN, Cr23C6, γ VC and VC in the steels containing V, and Al3Ni, σ phase, α phase, AlN and Cr23C6 in the steels containing Al, and ZrS2, ZrC and α phase in the steels containing Zr by X-ray diffraction of the electrolytically extracted residues.
3) Tensile strength was much increased linearly with V content and slightly decreased with Zr content.It was invariable with different Al contents, but it was much higher at lower temperature when α phase existed in the steels.
4) Creep rupture strength was almost invariable with different contents of additional elements when C content was low.But when C content was higher, it was much increased with V content and slightly decreased with Al content.Creep rupture strength was maximum at the content of about 0.2% Zr.