Qualification of Cryogenic Structural Materials for the ITER Toroidal Field Coils

Abstract

This paper provides qualification test results of large forgings and thick hot rolled plates of austenitic stainless steels, newly developed JJ1 (0.03C-12Cr-12Ni-10Mn-5Mo-0.24N), and 316LN containing high nitrogen of 0.2%, to be used in coil cases of the ITER toroidal field coils. The distributions of tensile properties at liquid helium temperature (4K) in products, average strengths with standard deviations at 4K, temperature dependence of strengths are evaluated to qualify the materials and to establish a reasonable quality control method to be applied to mass production materials for the ITER toroidal field coils. It is also demonstrated that temperature dependence of strengths are expressed by quadratic curves, which are expressed as a function of carbon and nitrogen contents and strengths at room temperature.