| 摘要 |
PURPOSE:To obtain sound structure at boundary part and to prevent breakdown accident by casting an outer layer by centrifugal casting method and next casting an inner layer by top pouring under condition of reduced pressure. CONSTITUTION:The outer layer 10 is formed by the centrifugal casting method and flux 12 for preventing oxidation is spread on the surface of outer layer. After solidifying the outer layer 10, a metallic mold 8 is stood and the pressure reducing device is set and by working a vacuum device, the pressure in inner part of the metallic mold 8 is reduced at the prescribed pressure. Next, a ladle 24 is set to the metallic mold 8 and at the time of pouring molten metal 14 for inner layer from a pouring hole 28 of the ladle 24, a metal plate 18 having low melting point is melted and the molten metal is filled up from lower part 6 to middle part 4 and upper part 2 and solidified, to form the inner layer. The molten metal 14 for inner layer is violently reacted with the flux 12 on the surface of outer layer 10 to generate CO gas. By this method, the flux 12 is melted out and the molten metal 14 is brought into contact with inner face of the outer layer having no impurity and by melting a little of the inner face of outer layer, they are perfectly jointed under melting.
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