Effects of nitrogen, niobium, phosphorous and carbon on the mechanical properties of aged 316LN stainless steels at the cryogenic temperature, 4K

Type 316LN stainless steel is a candidate material for jacketing materials of Toroidal Field (TF) coil for International Thermonuclear Experimental Reactor (ITER). It was known very well that superconducting reaction heat treatment, i.e., aging caused intergranular sensitization and decreasing of ductility and toughness of stainless steels at 4K. In this paper, the effect of N, Nb, P and C on the 4K mechanical properties of aged 316LN stainless steels was discussed. In order to prevent decreasing of 4K ductility and toughness of aged 316LN stainless steels with P content of an industrial level, Nb free, C content less than 0.01 mass% and N content less than 0.18 mass% were recommended. (author)