2019 年 54 巻 6 号 p. 427-436
Cryogenic structural materials having high strength and high toughness at 4 K are one of essential elements to fulfill the performance of toroidal field (TF) coils for fusion facilities, in which a large electromagnetic force is generated. The National Institutes for Quantum and Radiological Science and Technology (QST) has developed cryogenic structural materials for ITER TF coils and central solenoids (CS). Two review papers that holistically describe the history of development of cryogenic structural materials at QST for over 30 years, as well as their applications to ITER TF coils and CS, were published in TEION KOGAKU in 2013. This review paper complements those papers, focusing on the 4 K mechanical properties of the base and weld metal of the cryogenic structural materials and material code, which are necessary for applying these materials to the TF coils. The effects of carbon and nitrogen on the strength, relation between strength and toughness, fatigue properties, technical background of material code published by the Japan Society of Mechanical Engineers (JSME), and so on are explained in this paper. The status and vision of the materials development towards TF coils for future fusion facilities are also briefly described.