A superconducting material consisting of niobium and tin. Niobium and tin can form three intermediate-phase compounds, (Nb3Sn), Nb6Sn5 and NbSn2. They all have superconductivity. Nb3Sn has the highest superconducting critical temperature Tc= 18.05k, and the upper critical magnetic field Hc= 22.5t (4.2k). The critical current density of Jc is about 105A/cm2 (4.2k,10T). Nb3Sn is an Al5 intermetallic compound, cubic crystal system, and the lattice constant a=529.02 ~ 529.16 PM. Nb3Sn has a wide homogeneous region, ranging from 17% to 27% (at) Sn. Niobium tin superconducting alloy is brittle and difficult to be processed into materials. The films were prepared by vapor deposition of niobium and tin chloride through hydrogen reduction. Niobium-tin superconducting materials have been applied to superconducting magnets.
At present, inner tin method is one of the most important methods to prepare Nb3Sn superconducting wire. This method usually adopts the method of multiple recombination. The Nb rod is squeezed into the porous copper ingot to get CuNb composite rod, and then the Sn rod is loaded into the CuNb composite rod after drilling to get subcomponents. Through the design of porous copper ingots, the Cu/Nb/Sn ratio in the superconducting wire can be changed to improve the performance of the final wire.
At present, porous copper ingots used for Nb3Sn superconducting wire are usually distributed in a multilayer uniform way, with the same pore size in each layer and uniform distribution along the circumference. However, Nb3Sn superconducting wire is mainly processed by cold drawing. The deformation of outer core wire is large and the force is uneven, which is likely to produce core wire distortion. As a result, the final wire is overlapped after heat treatment, which increases the magnetic hysteresis loss of the wire.
