Manufacture of practical NbTi alloy superconductors

① Alloy smelting. The best alloy ratio contains Ti in 46%~50%(mass percentage).
② In the NbTi alloy rod processing, the highly uniform NbTi rod has not only the uniformity of composition, but also the uniformity of mechanical properties.
(3) Coating stabilizing material, hundreds of thousands of NbTi filament are buried in stabilizing high-conductivity oxygen-free copper or high-purity aluminum to prevent thermal loss or provide current bypass. Remaining resistance ratio (RRR) is often used to describe the quality of stabilized materials. RRR refers to the ratio of the resistivity at room temperature 293K divided by the resistivity at low temperature (4.2K). Generally, the RRR ratio of stabilized materials is required to be above 30 for superconducting magnets.
(4) packet blocking material. Nb is a widely used barrier layer material to avoid the formation of TiCu4 and other intermetallic compounds between NbTi alloy and Cu matrix, and to prevent the cable from breaking the core and significantly reducing the critical current density (JC).
The composite design of multi-core complex is carried out before hot extrusion. The design is based on the parameter requirements of the finished superconducting wire, such as line diameter, core diameter, copper ratio, etc., to calculate the size of the casing barrier layer, NBI rod and the number of extrusion. In the multi-core composite line, the core wires of NbTi are closely arranged, from the core to the outside are arranged in a hexagonal layer, and the root number of each layer in turn constitutes the relationship of arithmetic series, such as 6, 12, 18, 24, 30, 36....
⑥ Extrusion and tensile, the use of extrusion to make the NbTi rod, Nb barrier layer and Cu layer matrix between the formation of high bond strength of the gold.