Mechanical and physical properties of modified N50 steel at cryogenic temperatures

Abstract

China Fusion Engineering Test Reactor (CFETR) has more advanced design parameters compared to the International Thermonuclear Experimental Reactor (ITER), particularly demanding a high yield strength (over 1500 MPa at 4.2 K) for jacket material in the cable-in-conduit conductor (CICC). Modified N50 austenitic steel, due to its excellent mechanical properties at liquid helium temperature, has been identified as a promising candidate material for the jacket material. However, while some research focuses on the mechanical properties of modified N50 steel at cryogenic temperatures, little is known about the cryogenic physical properties that are critical for conduit jacket applications. In this study, a modified N50 steel was prepared and characterized in terms of tensile properties and physical properties at cryogenic temperatures. We tested the tensile properties of the modified N50 at 4.2 K, 77 K, and room temperature (RT). Additionally, we measured the thermal conductivity, thermal expansion, specific heat capacity, and magnetization of the modified N50 from 4 K to 300 K. These results could provide a more comprehensive reference for applying the modified N50 steel in jacket materials for the CFETR.