| 摘要 |
PURPOSE:To prevent the variance in the electrical conductivity of a product with virtually no change in the compsn. ratio of a Cu-Zn alloy by coating the surface of the molten metal consisting of the Cu-Zn alloy with a molten coating layer of boric anhydride. CONSTITUTION:When a Cu-Zn alloy and boric acid are put into a graphite crucible in an electric furnace and are heated, the boric acid is decomposed to boric anhydride and steam. The steam evaporates from the crucible. When the crucible is further heated, the boric anhydride is made into a liquid and when the crucible is more further heated, the Cu-Zn alloy is melted and the melt of the boric anhydride forms a molten boric anhydride coating layer on the surface of the molten Cu-Zn metal. After the molten Cu-Zn metal coated with the surface is held in the above-mentioned way, the molten metal is ladled and is die-cast to the iron core of a cage type rotor by which the secondary conductor for the cage type rotor is formed. |
