Aluminum is an element in the Ⅲ A group of the periodic table. It is an active metal second only to K, Ca, Na, and Mg. It can interact with oxygen, nitrogen, water vapor, carbon dioxide, etc. in the air under high temperature conditions [2 ]. Aluminum casting refers to the process of mixing, stirring, standing, refining, slagging and other processes of liquid aluminum
into finished or semi-finished products of aluminum ingots, bars or other shapes. Aluminum and aluminum alloys will experience varying degrees of loss due to oxidation, refining, slagging and other reasons during the melting and casting process. The so-called aluminum casting loss is the general term for the unrecoverable metal loss and the metal contained in aluminum slag caused by oxidation, volatilization, and interaction with furnace walls and refining agents during the smelting process of aluminum and aluminum alloys . The general calculation formula for casting loss is: (amount of primary aluminum-amount of finished product) ÷ amount of primary aluminum × 100%. The higher the casting loss, the less the amount of finished product. For aluminum enterprises with an annual output value of 100,000 tons, if the casting loss is reduced One thousandth point, without additional investment, can produce 100 tons of aluminum products (that is, reduce the burning loss of 100 tons of aluminum products), which will be considerable social and economic benefits, so how to effectively reduce casting loss is very important. 2 Analysis of the causes of casting loss 2.1 The main external manifestations of casting loss can be divided into two parts: one is in the form of pure aluminum ash, and the other is in the form of bulk aluminum and defective aluminum and aluminum slag. I am in Henan xx Aluminum Company The melting and casting workshop has conducted data statistics. Among them, non-recyclable pure aluminum ash accounts for about 90% of casting loss (oxidation burning loss and slag formation), and other factors account for about 10%. Further statistics and analysis of other factors account for 10%. It is mainly caused by the secondary furnace burning loss of bulk aluminum and inferior aluminum and the aluminum content in the aluminum ash (the main raw material of aluminum ash aluminum). Therefore, the main causes of internal casting loss are oxidation burnout, inferior aluminum, etc. Secondary burning loss, aluminum content in aluminum ash. 2.2 The principle of aluminum oxidation burning loss can be further understood by the following chemical equation: 4Al+ 3O₂u003d2Al₂O₃ The thermodynamic study of metal oxidation shows that the metal oxidation trend, the oxidation order of each alloy element and the oxidation degree are all determined by the affinity of the metal and oxygen. , And related to the composition, temperature and pressure of the alloy. The greater the affinity of the metal to oxygen, the greater the tendency of its degree of oxidation, and the higher the degree of oxidation; the higher the temperature, the greater the affinity of the metal to oxygen, the greater the tendency of its degree of oxidation, and the higher the degree of oxidation; the lower the decomposition pressure of oxides , The greater the affinity of the metal with oxygen, the greater the tendency of its degree of oxidation, and the higher the degree of oxidation. 2.3 The factors that affect casting loss are: 1) liquid aluminum temperature; 2) contact strength of molten aluminum with oxygen; 3) aluminum content in aluminum slag; 4) molten aluminum brought out by slag removal; 5) defective aluminum, bulk How much aluminum is; 6) Other losses caused 3 Ways to reduce casting loss 3.1 Control the temperature of liquid aluminum well The melting point of aluminum is 660°C. Generally speaking, the casting temperature of primary aluminum is controlled at about 730°C or even lower, while the flow of aluminum alloy The corresponding casting temperature is lower than that of primary aluminum, about 710℃-730℃. For units that directly use the liquid aluminum in the electrolytic cell, when the high-temperature aluminum liquid enters the mixing furnace, it should be mixed with cold material in time, that is, it is kept in the mixing. Add inferior aluminum, aluminum slag, etc. into the furnace, or add part of the intermediate alloy (industrial silicon) into the furnace in advance to form a pressure-melted state, which not only increases the actual yield but also reduces the temperature. At the same time, the surface of the added cold material should be clean and free of oil stains, otherwise it may burn and release heat and promote burning. In short, effectively reducing the temperature of the molten aluminum to the corresponding casting temperature can reduce the great influence of temperature on casting loss. 3.2 Reduce the contact strength between molten aluminum and air. The greater the contact strength between liquid aluminum and oxygen, the more serious the oxidation burning loss, and the greater the casting loss. 4 Conclusion According to the above analysis, although casting loss is inevitable in the casting process, it is controlled by the molten aluminum. Measures such as temperature, reducing the contact strength between molten aluminum and air, controlling the aluminum content in aluminum ash, reducing the amount of defective aluminum, etc., will effectively reduce the casting loss during the casting process, and will have a significant effect on the enterprise. Economic benefits.
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