Abstract
Surface penetration in copper alloys takes place depending a great deal upon both the species of metals and the condition of mold sand. From our testings, it is obvious that the chemical penetration in copper alloys will take place at the oxide film, when copper oxide produced in an oxidising atmosphere at elevated temperature, on the surface of castings. Moisture in mold sand, however, causes also this chemical penetration. So the presence of moisture in mold sand at elevated temperature will promote the oxidation of metal.
These results led us to conclusion that in such kinds of copper alloys making cupric oxide films on their surface, the presence of moisture in mold increases the amount of cupric oxide, and eventually the degree of penetration. (N. T.)
