[China Aluminum Industry Network] The production of aluminum alloy ingots using electrolyzed primary aluminum liquid, common 6063 aluminum alloy accounts for more than 90%, and occasionally also produces aluminum alloys such as 3003, 6061, 6082, 6052, and 5052. The production of these aluminum alloys has a small solid-liquid phase temperature range, small tendency of hot and cold cracks, and low technical difficulty. Unlike the 2XXX series hard aluminum and the 7XXX series super hard aluminum, the alloy contains many elements and has a wide range. Due to the wide temperature range of crystallization, the plasticity in the solid-liquid region is low, and it has a great tendency to form hot cracks and looseness. Taking into account the influence of the ratio of impurity elements Si and Fe on the properties of the alloy, consider adding copper, manganese, and chromium to improve the corrosion resistance of the alloy, and adding titanium and zirconium to improve the ingot and recrystallized structure.
The smelting furnace shall add the dry head and tail material without moisture to the bottom of the smelting furnace before pouring the aluminum water. Aluminum bath liquid temperature is very high, under normal circumstances as high as 950-965 °C, the bottom aluminum bath temperature is not lower than 940 °C. After the molten aluminum is poured into the smelting furnace, there is still 820-860°C. In order to prevent oxidation of the aluminum liquid at high temperatures, a layer of coating agent is immediately sprinkled over the surface of the melt. Because the melting point of the covering agent is lower than that of the aluminum liquid, the density is smaller than that of the melt, and the wettability is good. A continuous liquid protective film is formed on the surface of the melt, and the melt in the furnace is separated from the air. Under normal circumstances, oxygen or water vapor cannot or can only react with the aluminum liquid through the cover layer, and the hydrogen atoms dissolved in the electrolyte can escape through the cover layer due to its small radius.
Due to the high content of impurities in the electrolytic aluminum liquid gas and impurities, it is necessary to strengthen the melt refining process for the above-mentioned compositional characteristics. Refining usually uses powdered refining agents and is blown with nitrogen; first, the quality of the refining agent and nitrogen must be ensured. The production of 6063 aluminum alloy ingots generally uses 1# refining agent; at present, there are many kinds of commercial refining agents in the country, and the vast majority of enterprises are on the grounds of confidentiality, and do not explain the composition of components to users, and the price competition among suppliers is fierce. , Individual bad refining agent manufacturers from the use of chemical raw materials, formulas and processing methods on the cutting corners, refining agents must ensure quality, carefully selected. The quality of the refining agent of Shenzhen Parco Chemical Materials Co., Ltd. is better. Try it out. Nitrogen can not be manufactured by itself. Commercially available industrial nitrogen is used. The purity is 99%. Then nitrogen has 1% oxygen and moisture. The longer the blowing time, the more water and oxygen are brought into the aluminum liquid. The nitrogen used for refining must ensure nitrogen purity ≥ 99.995%. A nitrogen production line with a flow rate of 20M3 was built. The equipment was put into production for less than 200,000 yuan, and the equipment investment was recovered over a year. It not only ensures the purity of nitrogen, but also saves production costs.
High-quality refining agent and high-purity nitrogen are used for refining twice at 730-750°C. According to the previous refining refining agent dosage of 2.5kg/tA, the refining time is 25-30min; After refining, slag is added, magnesium is added, and the fire is made up. The second refining refining agent dosage 1.5kg/t, refining time 15-20min. After the second refining is completed, after the slag, sample analysis, and composition are qualified, a layer of coating agent is then sprinkled and allowed to stand in the furnace for 30 minutes.
With the use of flux adsorption refining, the refining effect is closely related to the purity of the nitrogen purity of the refining agent, and is also closely related to the refining operation. Because the blowing refining is based on partial pressure diffusion and degassing and flotation and slag removal. Refining is only available in areas that are in close contact with refined gases and powders. Operators must follow the rules of operation, and let the refiner move along the bottom of the furnace at the four corners of the melting furnace and move it forward and backward and left and right, so that all the molten aluminum is in full contact with the refining agent and nitrogen, leaving no dead ends. The effect of gas refining is more dependent on the gas dispersion and the size of the bubbles. The smaller the bubble size, the better the degassing effect. Because the smaller the bubbles, the more the number of bubbles caused by the same volume of gas, the larger the surface area; and the slower the float rate; the longer the contact time with the melt. When the ordinary T-shaped refiner is used, the diameter of the bubbles is about 10mm, and the effect is very good. If a 15mm-diameter steel pipe is used as a refiner, the diameter of the bubbles can reach 300mm or more. Using more nitrogen, the degassing effect is still poor.
Flux adsorbent is used, and the refining agent is directly in contact with the aluminum melt, and the effect of deslagging is achieved through adsorption and diffusion. At the same time, the refining agent also has a degassing effect. Degassing of flux is mainly manifested in three aspects: First, with the complex γ-Al2O3. The removal of XH removes the partially-complexed hydrogen absorbed by the oxidized inclusions. The second is that when the flux decomposes and interacts with the melt, it forms a gaseous product and diffuses and removes hydrogen. Third, the melt surface oxide film is dissolved by the cryolite in the flux to facilitate the diffusion of atomic hydrogen dissolved in the aluminum liquid into the atmosphere.
The purpose of standing: First, it is convenient for the upstream of the refined oil carrier to bring the gas and fine non-metallic inclusions in the aluminum liquid out of the liquid surface, and the second is to facilitate the sinking of large non-metallic inclusions to the bottom of the furnace.
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