非破壊パルスマグネットのための水田式溶製法による銅銀合金の開発

抄録

The wire used in non–destructive pulse magnets must have high strength and high conductivity in order to withstand the huge electromagnetic force load. In particular, excellent values have been shown for wires with a silver concentration of 6 mass%. However, this wire has not been able to stably reproduce the magnetic field generated by each lot, and further research and development of materials is required. It is predicted that void defects in the ingot, which is the material for the wire, will cause defects on the surface of the wire and a decrease in the strength of the wire. In this study, we compared the microstructures of Cu–Ag alloys produced different melting methods and investigated melting conditions that suppress the inclusion of voids.
In air casting, relatively large void exceeding 100 μm in diameter were observed regardless of the melting temperature. Since the oxygen content was high, it is thought that the occurrence was caused by the atmosphere that was involved during casting. On the other hand, in the vacuum melting and Mizuta method, void were observed in the solidified structure at a low melting temperature of 1160°C, but no void were observed at a high melting temperature of 1350°C. The temperature threshold for the presence of void is that void disappear when melting is performed at a temperature of 1250°C or higher. In melting at temperatures below 1200°C, shrinkage cavities were thought to have formed due to the rapid cooling rate. However, on the other hand, there is a fact that void disappear when melting is performed at 1160°C after melting at 1350°C. From this, it cannot be concluded that shrinkage cavities are generated due to solidification at low temperatures, and other factors must be considered.