Metal treatment – Compositions – Fluxing
Patent
1996-10-28
1998-06-09
Simmons, David A.
Metal treatment
Compositions
Fluxing
148 23, 75315, 75314, 75313, 75303, C22B 2100
Patent
active
057627223
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATION
This application is the national phase filing of International Application No. PCT/CN95/00090 filed Nov. 17, 1995, which is hereby incorporated by reference.
TECHNICAL FIELD
The present invention relates to a covering flux for smelting aluminum and a process for its preparation; particularly to a highly efficient covering flux for smelting aluminum which can be used in the re-smelting and reclamation of aluminum waste such as aluminum scraps, aluminum foils, ect., and to a process for the preparation of the covering flux.
BACKGROUND ART
For their unique properties, the metal aluminum and its alloys have been put into wide applications in various aspects of national economy and people's daily life. And with the development of the economy, the worldwide demand on aluminum is increasing year by year. However, on one hand, a large amount of aluminum waste emerges in the process of aluminum processing, e.g., the scraps yielded in the process of turning and milling, etc.; on the other hand, a rather big amount of aluminum waste is also produced because of the abandoned industrial equipments and the consumption of people's daily appliances. In order to re-utilize the aluminum waste, they are reclaimed by being put back into the smelting furnace for re-smelting. However, as aluminum is a rather active and easily oxidized element, the yield ratio will decrease due to the oxidization during the re-smelting process when it is put back into the smelting furnace, and therefore a portion of resources are wasted. In order to prevent the oxidization of waste during the process of re-smelting, usually a layer of protective flux, also called covering flux, is covered on the surfaces of aluminum waste in the process. One widely adopted covering flux for smelting aluminum is a mixture of potassium chloride and sodium chloride with the ratio of 1:1 by weight. The Soviet Patent No. SU571522 (published on 19 Jul., 1974) discloses a process for the treatment of aluminum alloy scraps, wherein the compressed scraps are laid on the base layer of aid-flux (a calcium-barium chloride which is preheated to 800.degree.-1000.degree. C.); then a layer of molten aluminum is laid on the scraps; afterwards a light flux (100-300 mm-thick eutectic mixture of potassium chloride-sodium chloride-cryolite, functioned to prevent the oxidization of aluminum alloy), is laid on the layer of molten aluminum. West German Patent No. DE 2821353 (published on 2 Jun., 1977) discloses a process of reclaiming aluminum from aluminum waste, by recycling the waste aluminum scrap to aluminum melt, and treating the slag with a flux of composition of 40-55 wt. % sodium chloride, 40-55 wt. % potassium chloride and 3-15 wt. % of carbonate, borax of Li, Ba, Mg or Ca. Although these methods can raise the yield of aluminum and aluminum alloys, they have one feature in common, i.e., with both methods, scraps of aluminum or its alloys need to be dipped into molten aluminum, which on one hand, a lot of energy is consumed, on the other hand, under some circumstances, especially when reclaiming aluminum alloy, it will have some difficulties in preparing molten aluminum alloys with same composition as the aluminum alloys to be reclaimed. The main reason is that the protective function of the existing covering fluxes before the aluminum scrap is molten is too weak, and, instead of adding molten aluminum, if the aluminum scraps are directly heated and molten (commonly known as net feed), violent oxidization will occur before aluminum scraps are molten, thereon the yield decreases.
DISCLOSURE OF THE INVENTION
Therefore, one object of present invention is to provide a covering flux for smelting aluminum, and as this covering flux will also have a good protective function before aluminum scraps are molten, the yield of aluminum will rise; even under the circumstance of net feed, a rather high yield can also be achieved with rather good economical profits.
The second object of present invention is to provide a method for preparing sai
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Elve M. Alexandra
Simmons David A.
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