2017 年 81 巻 3 号 p. 133-142
The factors influencing the tensile deformation behavior and the electrical conductivity of pure copper castings fabricated by an industrial process were investigated. The pure copper castings had sufficient deformation characteristics and electrical conductivity on the practical side. However, the deformation characteristics and the electrical conductivity of the castings were slightly inferior to those of the castings fabricated by laboratory experiments. The oxygen content in the castings fabricated by the industrial process was less than 0.01 mass%, which resulted in the absence of Cu-Cu2O eutectic phase that exhibits the brittle behavior. On the other hand, observations of the fracture surface and the cross-section of the castings showed the existences of microporosity and two types of inclusions. These may be the factors influencing the decrease in the both tensile strength and uniform elongation. The microporosity were suggested to be caused by higher hydrogen content in the melt and/or by slower cooling rate during solidification. EDX analyses suggested that the inclusions are a kind of slag and straw ashes. Furthermore, phosphorus and iron content in the castings fabricated by the industrial process were higher than those in the castings fabricated by the laboratory experiments. These may be the factors influencing the decrease in electrical conductivity. The above findings indicated the several methods to improve the properties of the castings fabricated by the industrial process.
