- Start of sales: April 2015
What is superconductivity?
Superconductivity is a phenomenon of zero electrical resistance. To transmit electricity through a superconductive material, the material must be transformed into an electric wire. Sumitomo Electric produces superconductive wires (electric wires) and sells them under the trade name of “Bismuth-based superconductive wire DI-BSCCO.” Compared with ordinary electric wire (copper), superconductive wire needs a cross sectional area of only approximately 1/200 to transmit the same quantity of electricity (when an electric current of 200 A is applied). The zero electrical resistance of a superconductive wire enables stable transmission of electricity at a low power loss with low heat generation. Owing to these advantages, superconductive wire is expected to expand the scope of application, such as motors that drive automobiles, buses, Shinkansen bullet trains, and other vehicles.
What are the advantages of DI-BSCCO Type HT-NX?
The ultra-high strength, high-temperature bismuth-based superconductive wire developed by Sumitomo Electric achieves tensile strength approximately 50 to 60% higher than that of conventional high-strength superconductive wires. Such high tensile strength enables our superconductive wire to bear high electromagnetic force, making the wire useful for large capacity magnets or other devices being operated in a magnetic field with a flux density of a couple of dozen Tesla.* Conventional high-strength superconductive wires cannot be used in such severe operating conditions.
Our superconductive wire is expected to expand the scope of application beyond use in an ultra-high electromagnetic field. In particular, owing to its higher conducting capacity compared to conventional copper wires and metal superconductive wires, our superconductive wire can downsize the necessary equipment and devices. In addition, the excellent basic performance of our superconductive wire is expected to enhance the accuracy and stability of magnetic fields, thereby improving the sensitivity of the necessary equipment and devices.
Further, the minimum allowable bidirectional bending diameter of our superconductive wire is smaller than that of conventional high-strength wire by approximately 30%. This means that our superconductive wire is also useful for making smaller diameter coils.
On account of the “Development of High-strength Bi-2223 Wire,” Sumitomo Electric won the 19th Superconductivity Science and Technology Award from the Society of Non-Traditional Technology.
Aiming to provide users with easier-to-use superconductive wire, Sumitomo Electric will continue to improve and expand its superconductive wire production system.
Superconductivity Technology Division
What motivated Sumitomo Electric to develop this superconductive wire?
High-temperature superconductive wires are roughly divided into two types: bismuth-based wires and rare earth-based wires. Sumitomo Electric manufactures the former. A rare earth-based wire is manufactured by piling thin films on metal substrates. Since conventional bismuth-based superconductive wires were substantially inferior to rare earth-based wires in mechanical strength, wire users had no choice but to use rare earth-based wires when developing large capacity magnets and equipment that would work in magnetic fields with a flux density of a couple of dozen Tesla. To encourage these users to also use our bismuth-based superconductive wires for these applications, we started developing an ultra-high strength bismuth-based superconductive wire.
What was the biggest problem you had to solve in the development of the wire?
Our ultra-high strength superconductive wire is made by sandwiching a tape-shaped superconductive wire between metal foils and soldering the wire with the foils. The type of nickel (Ni) alloy foil we selected as the metal foil has excellent corrosion resistance but is very difficult to solder. Though we treated the surfaces of the Ni-alloy foils to improve their solderability, we had a lot of difficulty. From the advice of many specialists, we understood that the key point in the surface treatment of Ni-alloy foils is how to efficiently remove the oxide films from the foils. We finally devised the most appropriate method (conditions) for securely removing oxide films, and as a result, we could start trial manufacture of ultra-high strength superconductive wire using Ni-alloy foils.