FO-08: DEVELOPMENT OF A CERAMIC TUBE OF GAS-FIRED IMMERSION HEATER FOR THE ALUMINUM MELTING FURNACE

摘要

This paper describes the development of a ceramic tube of gas-fired immersion heater for the aluminumrnmelting furnace. In the aluminum casting industry, a high-performance, small sized, continuousrnaluminum melting furnace using city gas has widely been introduced. This new type of aluminumrnmelting furnace is one of indirect heating types using a carbon-bonded SiC ceramic tube developed byrnthe authors. To improve the performance of casting and molding of aluminum alloy, sodium flux isrngenerally added into the molten aluminum. The sodium compound passes through the wall of the heaterrntube which is made of carbon-bonded SiC and reacts with oxygen contained in the burned gas, thenrnreacts with SiC and produces amorphous glass which has a low melting point. As a result, the wallrnthickness is reduced and the service life of the ceramic heater tube is shorten owing to thermal corrosion.rnThe mechanism of thermal corrosion was experimentally examined.rnTo protect the reaction between sodium compound and SiC and to increase the life of ceramic heaterrntubes, the authors have newly developed a heater tube which has a two-layer structure combining tworndifferent materials. It was found that the durability of the ceramic heater tube is approximately 6 monthsrnor more at a molten aluminum temperature of 750℃ in a sodium flux concentration of 150 ppm.