LOW NUCLEAR EXOTHERMIC/LOW ACTIVATION MN-CR NON-MAGNETIC STEEL SUPERIOR IN ANTICORROSION AND WELDABILITY

PROBLEM TO BE SOLVED: To obtain the steel that is suitable for use in a ferromagnetic field and corrosive environment and that is superior in corrosion resistance and weldability by specifying the composition made up of C, Si, Mn, Cr, N and Fe and regulating Ni quantity in inevitable impurities. SOLUTION: The superior nonmagnetic steel is obtained by which contains 0.05-0.25 wt.% C, 1.0% or less Si, 10.0-18.0% Mn, 15.0 plus-18.0% Cr, and 0.30% or less N, with the balance essentially consisting of Fe and inevitable impurities, in which Ni content in the inevitable impurities is desirably regulated at 0.2% or less, in which nuclear exothermic and activation are suppressed, with the components satisfying an expression, i.e., A/B>=1.45 (A=24C+21N, B=Cr+0.5Si+0.07Mn-13.2), and in which no δ ferrite is contained. This nonmagnetic steel is provided with the mechanical characteristics, weldability and nonmagnetism equivalent to stainless steel, and also indicative of excellent corrosion resistance in the real environment, so that it is suitable as a material for the vacuum container of a nuclear fusion reactor.