Estimation of tensile strengths at 4K of 316LN forging and hot rolled plate for the ITER toroidal field coils.

A prediction method for both yield and tensile strengths of stainless steels from room temperature to liquid helium temperature (4K) has been developed by JAEA in order to rationalize qualification tests of cryogenic structural materials used in large superconducting magnet for a fusion device. This method is to use quadratic curves which are expressed as a function of carbon and nitrogen contents and strengths at room temperature. This study shows results of tensile tests at 4K and confirmation of accuracy of prediction method for tensile strengths at 4K for large forgings and thick hot rolled plates of austenitic stainless steels, which can be used in the actual coil case of the International Thermonuclear Experimental Reactor (ITER) toroidal field (TF) coils. These products are 316LN having high nitrogen and maximum thickness is 600mm. As the results, it was confirmed that the materials which satisfied ITER design requirement can be manufactured and the tensile strengths of these products at 4K can be predicted by using appropriate quadratic curves. [ABSTRACT FROM AUTHOR]