Molten metal purification is important for foundry. The quality of casting and rolling metal can be further improved by adopting melt purification method, equipment and management measures. The purification of molten metal can be realized in the following ways and methods.
Molten Metal Purification
Melt transfer mode: the melt transfer mode from the furnace to the static furnace is improved, and the dropping mode is replaced by the inclined plane form, so as to avoid the oxidation increase and gas suction aggravation caused by dripping. At the same time, avoid large areas of melt exposed to air, and increase the oxidation suction. Improve the heat insulation of the chute, use new materials, increase the thickness of the chute, or cover the chute. Find a reasonable melting temperature to avoid burning in the flume due to too low melting temperature, thus increasing the oxidation and gas absorption of the melt.
Static furnace refining: by improving the refining tube or controlling the flow and pressure of degassing medium, the influence of excessive bubbles on degassing effect can be avoided. In order to produce high quality aluminum foil, the following methods are suggested to replace the current single inert gas refining to improve the purification effect of melt.
Gas flux mixed refining: blowing a small amount of flux powder, forming a liquid salt film on the surface of the bubble. The oxide film on the surface of bubble breaks, adsorbs and dissolves. The hydrogen in the melt diffuses into the bubble, which improves the degassing effect.
CCl4: CCl4 reacts with aluminum to produce AlCl3, HCl, Cl2 and other active gases. The hydrogen in the melt is removed by physical and chemical action, which improves the refining effect.
The mixture of fluorine refrigerants and argon is used for refining: chlorine and fluorine (CCL2F2) produced by the decomposition of Freon can react with aluminum alloy elements to form molten salts such as HCl, AlCl3 and AlF3, which play the role of bubble flux mixed refining.
The on-line degassing device introduces protective gas into the chamber to reduce the absorption and oxidation of hydrogen. By optimizing the rotating speed and improving the air outlet of the rotor, the bubbles are finer and the degassing effect is improved.
In order to produce high quality aluminum foil cotton, coarse filter (such as 10-20ppig filter) is added before degassing to improve the purity of melt, increase the diffusion rate of hydrogen in the melt and improve the on-line degassing effect. Strengthen the cleaning and replacement of CFF filter box to ensure the shape and size of filter chamber and ensure the filtering effect.