Development of Pb- and Cd-free NbTi/Nb<sub>3</sub>Sn Superconducting Joint Technology

This paper reviews the Pb- and Cd-free NbTi/Nb3Sn superconducting joint technology and the related technologies. The key to the Pb-free joining process is the use of a high-temperature tolerable Nb superconducting alloy as an intermediate material, which enables metallic bonding between the Nb3Sn wire and the Nb superconducting alloy intermediate material through a chemical reaction, and between the NbTi wire and the Nb superconducting alloy intermediate material by pressure welding. Consequently, the NbTi/Nb3Sn superconducting joint is realized. This novel technology is expected to be used in the world’s first Pb-free, environmentally friendly NMR superconducting magnets.