2相混合組織をもつ高珪素ステンレス鋼線の加工硬化挙動とその他の諸特性について

Abstract

Two-phase stainless steel wires composed of austenite and ferrite were studied on their mechanical properties, stress corrosion cracking behavior and corrosion resistance against chloride or acidic solutions. The volume fraction of ferrite in the alloys used is 50 percent.The main results obtained are as follows:(1) At low reductions of cold drawing, the yield strength of two-phase stainless steel wires increases with increasing cold reduction with the same work hardening rate as that of single-phase austenitic stainless steel wires. After heavy cold drawing, the work hardening rate of two-phase alloys becomes an intermediate value of those of austenitic and ferritic stainless steels. This may be attributable to preferred strain concentration in the austenite with small reductions by drawing and a distribution of strain equal in the austenite and ferrite phases after heavy drawing.(2) A good combination of the tensile strength and reduction of area is obtained by aging between 300°C and 500°C after heavy drawing. The strengthening after aging at 500°C may be due to the (Fe, Cr)23C6 carbide precipitated in the austenite and ferrite phases.(3) The resistance against stress corrosion cracking of 20Cr-10Ni-4Si steel drawn is better than that of SUS 316 austenitic stainless steel wire.(4) The pitting and chemical corrosion resistances against chloride or acidic solusions are also excellent. This may be attributed to high silicon contents of the steels.