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What Happens to Aluminum and Its Alloys During Smelting? (Part 1)

May. 07, 2020

Aluminum is located in Ⅲ A group elements in the periodic table, is second only to K, Ca, Na, Mg of an active metal, under the condition of high temperature and oxygen, nitrogen, water vapor, carbon dioxide in the air, etc.

Aluminum melting casting is the process of turning liquid aluminum into aluminum ingots, bars or other shapes of finished products and semi-finished products by batching, stirring, standing, refining and slagging.In the process of melting and casting, aluminum and aluminum alloys will suffer from different losses due to oxidation, refining and slagging.

In the opinion of 99.9% aluminum ingot suppliers, the so-called aluminum casting loss is the general term for the non-recoverable metal loss and the metal contained in aluminum slag caused by oxidation, volatilization and interaction with furnace wall and refining agent during the smelting process of aluminum and aluminum alloy.

Casting damage of the general calculation formula for - finished product amount (aluminium) present aluminium amount by 100%, casting loss is higher, the product quantity is less, the annual output value in 100000 tons of aluminum enterprises, if cast loss reduce 1 ‰, which does not need additional input, more output of 100 tons of aluminum products (i.e., reduce the loss of 100 tons of aluminum products), it will be a considerable social and economic benefits, so how to effectively reduce the casting damage appears very important.

Aluminum Alloy Ingot Supplier

Aluminum Alloy Ingot Supplier

The aluminum alloy ingot supplier considers the cause of the casting damage

2.1 the main external forms of casting damage can be divided into two parts: one is in the form of pure aluminum ash; the other is in the form of bulk aluminum, defective aluminum and aluminum slag.

Casting workshop for data statistics, including not pure aluminium ash accounted for about 90% of the casting loss (oxidation burning loss slagging formation), other factors accounted for about 10%, against 10% of other factors for further data statistical analysis, the main is large, such as aluminum and aluminum defect and aluminium ashes of secondary oven burning aluminum content (main raw material of aluminum ash), so the inner cause of casting damage is the main reason why oxidation burning loss, defective secondary burning, such as aluminium ashes aluminum content.

2.2 aluminum oxidation burning loss principle can be further understanding through the following chemical equation: 4 al + 3 O ₂ = 2 al ₂ O ₃

The study of metal oxidation thermodynamics shows that the trend of metal oxidation, the order and degree of metal oxidation are all determined by the affinity between metal and oxygen, and are related to the composition, temperature and pressure of the alloy.The greater the affinity between metal and oxygen, the greater the tendency of oxidation degree and the higher the degree of oxidation.The higher the temperature, the greater the affinity between metal and oxygen, the greater the tendency of oxidation degree, the higher the degree of oxidation;The smaller the oxide decompression, the greater the affinity between metal and oxygen, the greater the tendency of oxidation degree, and the higher the oxidation degree.

In melting temperature range, the aluminum and oxygen affinity is very big, easy to oxidation, surface form Al ₂ O ₃ film after oxidation, when higher than 500 ℃ for metastable r - Al ₂ O ₃, this kind of metastable oxide film to stable oxidation film process, the volume shrinkage and further oxidization and crack.With the increase of temperature and the extension of time, the oxidation film grows faster and the oxidation amount and thickness increase significantly.

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