Effects of Nitrogen on the Mechanical Propeties of 316LN Stainless Steels

Abstract

Type 316LN stainless steel is one of the candidate structural materials for the low stress regions of the toroidal field coil for International Thermonuclear Experimental Reactor (ITER). It was confirmed that contribution of nitrogen to 0.2% yield strength of 316LN at 4K is more than that of carbon in a previous paper. ⁸⁾ However, it has never be investigated the tensile property of the 316LN, in which carbon content was controlled at low level and nitrogen content was varied. Therefore, it was systematically investigated the mechanical properties of the low carbon controlled 316LN, in which nitrogen content was varied in the wide range, at 4K, 77K, room temperature and high forging ternperatures. In consequence, it was confirmed that the cryogenic elongation of the specimens included the high nitrogen content over 0.221mass% was lower than an elongation-(T-M_d30) curve. T means tensile test temperature. In addition, the data of the reduction of area at 1373K were increased with increasing nitrogen content over 0.175mass%. It was inferred that these behaviors were influenced by enhance ment of dislocation density by super saturation of solution nitrogen.