COMBUSTION PREVENTIVE TREATMENT FOR HEAT INSULATING SLEEVE IN RISER PART FOR CASTING MG ALLOY

摘要

PURPOSE:To prevent the burning of a molten metal by treating the heat insulating sleeve in a riser part with a soln. of boric acid or borofluoride alone or a soln. mixture composed thereof and blowing an inert gas into a casting mold if necessary. CONSTITUTION:The riser part 6 is provided on a mold 5 and a pouring basin 4 and the product mold 5 are connected by a runner 9. The heat insulating sleeve 7 made of ceramic fibers in the riser part is chemically treated with the soln. of >=2wt% boric acid or borofluoride alone or the soln. mixture composed thereof. Such sleeve 7 is installed in the casting mold and if the riser capacity is large, the inert gas such as sulfar dioxide is blown into the mold; thereafter the molten Mg alloy is poured into the mold. The burning of the molten alloy in the riser part 6 is prevented by the above-mentioned method.