STUDIES ON GAS IN ALUMINUM INGOT

Abstract

Hitherto the measurment of gas in aluminum ingot has been carried out by analyzing it extracted by vacum meltirg of the ingot, but the result of this measurment is difficult of application directed to actual factory operations in as much as the value measured is subject to a fairly marked change according to the device used for the measurment, preparation of test-pieces, conditions under which the gas is extracted, etc., coupled with complicity in the method of its extraction. Such being the case. the writers have studied the method of collecting and measuring the gas emanating direct from an aluminum ingot by boring holes in it, while it is immersed in a light oil, and that of collecting and measuring the gas emanating from the ingot by melting it in a caustic soda solution, and as certained that these two methods are identically effective in feeing and measuring the gas inquestion with such results as are generally applicable to actual factory operations, as the below-mentioned experiments indicate.1. Gas in Aluminum ingots:The gas contained in aluminum ingots differs in volume to some extent according as the ingots are made by different makers and according to the time of their manufacture even in those made by the same maker.2 Relation between casting temperature and cooling rate and volume of gas:Experiments made of the aluminum ingot cast at 660°, 700° and 750°C. show that the higher the temperature, the larger the volume of thegas contained in it is. It has also been ascertained that, in case the aluminum ingot once heated at a high temperatre s cooled down to its former normal temperature, the volume of gas absorped by the ingot its found notably larger than it was before being subjected to high heat. Further, it has come to the writers, knowledge that, in case the same metallic mould is used in casting aluminum ingots, the gas contained in them will decrease in volume follow the rise of the temperature of the mould, reaching the minimum at 150°C, but htiw again increasing as said temperature approaches 300°C.3. Degassing effect of chlorination:In case molten aluminum of about 10kgs, is left untouched after chloride, is passed through it for 10-20 minutes, the gas contained in it will be found to be small in volume within minutes subsequent to the passing of. chloride, but in case the molten mass is left as it is, it will again increasingly absorb the gas. Comparision of the gas measured and the specific gravity of it testifies to this tendency.4. Difference in volume of gas in aluminum ingot by the several melting and effect of degassing with zinc chloride:If the ordinary meiting method and the remelting method hitherto in practice a special method of melting, where by the ingot is degasified at the time of melting, are employed, it will be found that the volume of the gas in the molten aluminum will decrease mere, the more ease is taken in degasifying the melt and that, if the method usually in practice which merely aimes at melting it is used, the melt will absorb more gas than that already contained therein It has also been ascertained that degassing by means of chloride is effective when the gas contained in the melt is large in volume, but is not so when the gas in question is limited in volume and remain below a certain percentage.5. Melting method usually in practice and special melting method with reference to factory operations and gas contained in melt:In case an aluminum ingot is melted in a 10-ton reverberatory furnace, the volume of the gas contained in the melt while it breaks down, is subjected to degassing treatment, and comes out to the holding tray of furnace and is being cast can be measured, and the behaviour of the gasclarified, in relation to the time required for these operations.