Authors have developed a spherical shaped container having the internal wall constructed with ceramic hollow units for transferring molten aluminum. This newly designed container was expected to provide light weight and high heat retaining properties, compared with current cylindrical containers having the internal wall made of castable refractories. In this report, a pentagonal hollow unit having circular holes in the side wall was designed on the basis of thermal fluid analysis. Thus designed RBSN (Reaction-bonded Silicon Nitride) pentagonal hollow units were fabricated by slip casting forming processes using silicon powder slurry, green machining processes and reaction sintering processes in nitrogen gas. The evaluation of over-all heat transfer coefficient of the units showed that punching circular holes in the side wall made it possible to reduce the heat emission and the weight of the unit.

View full abstract

The amount of ceramics-work that can fill a furnace is limited by temperature differences in the effective volume of the furnace, and the energy consumption volume of ceramics-work sintering becomes higher due to vacant space in the effective volume. Utilizing high emissivity of SiC, we found that filling rate of ceramic-work rises by 16％ by using SiC powder coated Al2O3 setter, thereby reducing by 23％ sintering energy consumption rate of ceramics products. At the same time, the emissivity drop phenomenon was evaluated using SiC－ powder coated Al2O3 setter which is aged in air at 1700K. We then evaluated the emissivity of SiC (by parameters of smooth or rough surface, sinter or powder, with or without aging), and find new knowledge at the wave shape of thermal emissivity.

View full abstract