Effect of Oxygen Content on the Surface Defect Generation in Pure Copper Castings

Abstract

The effect of oxygen content on the surface defect generation in pure copper castings was investigated. The castings under lower oxygen content show the skin–formation type solidification, in which flow marks are sometimes generated. These are significantly affected by both the progress of solidification during mold filling and the stepwise elevation of the melt surface. On the other hand, the casting under higher oxygen content show the mushy type eutectic solidification, in which burning of silica sand （penetration into the sand molds） often occurs. These are not only because the melt under higher oxygen content shows better wettability with the silica sand but also because the melt contacts with the sand mold for a prolonged time due to the wider freezing range. These results suggest that the generation tendencies of the surface defects can be evaluated on the basis of the parameters reflecting the solidification behavior of the castings.