| 摘要 |
PURPOSE:To cast a small diameter rod of a Co-base alloy of superior appearance stably for a long time by forming a feed nozzle of a joined object of a BN molding and oxide ceramics. CONSTITUTION:A cast rod is drawn out through a feed nozzle 2 and a mold 3 from a molten Co-base alloy holding furnace 1, whereby a small diameter rod is produced. Here, the nozzle 2 consists of tubular oxide caramics 2a communicating at one end with the side face of the furnace 1 and a tubular molding 2b of 40-85wt% BN of the same bore of which the end part is joined tightly in one body to the other end of said ceramics. The bore of the nozzle 2 is the same as that of a tubular mold 3 or slightly smaller than the same. Here, if the BN in the molding 2b is below the lower limit, there is virtually no lubricity, and above the upper limit, workability is extremely poor, resulting in degraded corrosion resistance and hardness. The molding 2b is extremely good in spalling resistance, but is eroded at its high temp. part and does not withstand long-term use; it is therefore combined with oxide ceramics 2a such as Al2O3. |
