Chlorine and fluorine are well known as effective degassing agents for aluminum and its alloys. Fluorine has usually been used as a flux of fluorides. However, being different from gaseous chlorine, ...fluorine cannot be used so effectively as the "direct bubbling" of chlorine into molten metals. On the other hand, "Freon l2 (CCl2F2)" which is widely used as a refrigerant, contains both of chlorine and fluorine. Because of its odorless and non-poisonous properties, it is very simple in handling. Hence, it is very promissing of excellent degassing agent for aluminum and its alloys. In this paper, the authors report the effectiveness of CCl2F2 and N2-CCl2F2 mixture for degassing agents as well as the harmfulness of the waste gas after the degassing treatment. The results obtained were as follows: (1) Degassing ability of CCl2F2 evaluated by the porosity of aluminum castings was nearly twice as large as that of Cl2. However, the waste gas after the treatment of CCl2F2 was more poisonous than that of Cl2. (2) Degassing ability of N2-CCl2F2 mixture was greater than that of N2-Cl2 mixture. The degassing ability rapidly increased with the increase of CCl2F2 content up to 30% and the ability of N2 70%-CCl2F2 30% mixture was almost equal to that of 100% Cl2. (3) N2-CCl2F2 mixture containing less than 50% of CCl2F2 was less poisonous than 100% Cl2. The former was less corrosive against mild steel or aluminum than the latter. (4) By mixing CCl2F2 with Cl2, the degassing ability of the mixture increased in linear proportion with the increase of CCl2F2 content. The ability of N2-Cl2 mixture also increased by mixing CCl2F2 and it was equal to that of N2 70%-CCl2F2 30% when 20% of CCl2F2 was mixed with N2 90%-Cl2 10% mixture.
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