Torsion and Tensile Properties of Thin Wires of Nickel-Free Stainless Steel with Nitrogen Absorption Treatment

Abstract

A new manufacturing process for nickel-free austenitic stainless steel has been developed by authors. In combination with machining and a nitrogen absorption treatment, this process makes it possible to form small precise devices with a maximum thickness or diameter of 4 mm. The refinement of grains of Fe-24Cr-2Mo in mass% was attempted by thermo-mechanical treatment before nitrogen absorption treatment in order to increase the mechanical properties after nitrogen absorption treatment. Torsion and tensile properties and microstructures of Fe-24Cr-2Mo before and after nitrogen absorption treatment were evaluated to understand the effects of grain refinement on nitrogen absorption. The thin wire of the alloy is completely austenitized with nitrogen absorption at 1473 K for over 7.2 ks. The mean grain size of the alloy with nitrogen absorption decrease with the grain refinement process attempted in this study. The values of ultimate tensile strength and elongation in the alloy with and without nitrogen absorption increase with the grain refinement process. The torsional stress and rotation angle to fracture of the alloy increase with the grain refinement process and nitrogen absorption. According to the results of the torsion and tensile tests, the thin wire of the alloy with nitrogen absorption is expected to have good mechanical properties than conventional austenitic stainless steels.