| 摘要 |
<p>PURPOSE:To appropriately set the tapping temperature in accordance with the quality of a casting material, by blocking the tapping hole at the bottom of a crucible with a bottom cover made of a material which has a higher melting point than that of a casting material, and heating and melting the casting material and bottom cover in the crucible. CONSTITUTION:A crucible 14 has a crater-shaped bath room 16 at the central portion and a tapping hole 17 at the bottom wall. The tapping hole is blocked with a bottom cover 55 made of a metallic material which has a higher melting point than a molten metal 33 has. The casting material 33 is placed on the bottom cover 55, and then, an arc discharge 54 is generated by applying a high voltage accross an arc discharge electrode 34 and the material 33 while a pressure is being applied to the crucible and the inside of crucible is set to an inert atmosphere. The material 33 is melted and becomes a molten casting material 33b. The temperature is increased further more, but the material 33 will not be boiled because of the pressure applied in the crucible. When the temperature reaches the melting point of bottom cover 55, the cover 55 is melted instantly and the molten metal flows down to the mold located at the lower position through the tapping hole 17. Simultaneously, the arc discharge 54 is stopped automatically.</p> |
