Railroad is an important part of the social infrastructure, and the shutdown of any railroad service creates major problems. Railroad companies engage in daily maintenance operations to prevent the suspension of the service. However, maintenance involves a lot of night-time operations, and it is becoming difficult to secure the necessary workers. This has made it an important task to reduce the labor required for maintenance. Moreover, the transmission wires for trains that Proterial supplies (hereafter, “contact wires”) are required to have even higher electric conductivity to save energy.

Proterial has developed a copper alloy material that ensures the high strength, high wear resistance, and high electric conductivity of contact wires and applied it to contact wires. This has reduced the frequency of replacement of contact wires, thus reducing labor, and reduced electricity transmission loss, which helps conserve energy.

Normally, a metal material is given greater strength using more additive elements. However, the electric conductivity of a material declines in proportion to the amount of additive elements contained in it. As such, strength and electric conductivity are in a trade-off, making it difficult to increase both at the same time.

Proterial increased the strength of copper as the basic composition of a contact wire by adding a tiny amount of tin and indium. At the same time, the company developed a technology that inhibits the additive elements, which interfere with the movement of electrons, from melting into copper by having tin and indium react with oxygen in the copper and forming an oxide. The company has also found that fine dispersion of the oxide thus formed strengthens the organization and increases the strength and wear resistance of contact wire.

This has enabled the mass production of a copper alloy material for contact wire (SNN contact wire), which is about 1.2 times higher in strength and about 1.4 times higher in wear resistance than existing products from Proterial, while maintaining high electric conductivity, with continuous casting and rolling equipment. The SNN contact wire features a long interval between replacements, reducing the frequency of maintenance. It was consequently adopted immediately by West Japan Railway Company (JR West). At present, the SNN contact wire also contributes to the stability of the high-speed travel of bullet trains.