Aluminum burning loss in casting is the non-recoverable loss rate of aluminum and aluminum alloys due to oxidation and other factors during the production process.
For an aluminum company with an annual output of 200,000 tons, if the burning loss is reduced by 1‰, 200 tons more aluminum products will be produced without additional investment.
So how to reduce burning loss is very important. This paper mainly analyzes the causes of burning loss and the methods and approaches to effectively reduce burning loss.
Factors Affecting Oxidation Burning Loss in Casting
Aluminum liquid brought out by aluminum ash during the slag removal process;
Burning loss caused by excessively high casting temperature of molten aluminum, long-term heat preservation of molten aluminum in the holding furnace, and too long contact time with oxygen;
During the casting process, the molten aluminum is disturbed to form a turbulent flow;
The formation of a new liquid level of molten aluminum causes oxidation and slagging;
In the production process, the wrong ingredients and unqualified aluminum ingots caused the aluminum loss caused by the secondary furnace.
Methods to Reduce Burning Loss in Casting
The burning loss of molten aluminum in the melting furnace is the main part of the metal aluminum loss in the foundry, and it is of great significance to take effective measures to control the burning loss. Reducing waste aluminum or aluminum ingots with oil pollution to be directly returned to the furnace can prevent them from burning after entering the melting furnace, thereby avoiding the oxidation of molten aluminum.
Correct Use of Slag Remover
Strictly carry out aluminum liquid slag removal according to the process, which can control the excessive aluminum liquid brought out during the slag removal. When the temperature of the aluminum liquid in the mixing furnace is low, it is difficult to separate the aluminum ash and the aluminum liquid when stirring and removing the slag, resulting in excessive aluminum content in the aluminum ash.
After the molten aluminum enters the mixing furnace, there is a layer of scum on the surface of the molten aluminum.
These slags contain more metal aluminum, and the function of the slag-breaking agent is to increase the surface tension on the interface between the slag and aluminum so that the slag and aluminum are separated.
Install Aluminum Ash Separator
Although the aluminum content in the aluminum slag has been reduced after adding a slag breaking agent and stirring the slag, there is still some aluminum in the aluminum ash. The aluminum ash separator can remove 75% of the high-temperature aluminum ash by rolling Aluminum is effectively separated, and the metal aluminum in the aluminum ash is recovered to the maximum extent.
Control the Casting Temperature of Molten Aluminum
The melting point of aluminum is 660°C, and the casting temperature can be around 720°C-750°C. After the aluminum liquid with a higher temperature enters the holding furnace, it should be mixed with cold material in time.
The temperature drop of molten aluminum in the launder is 1.5-2.5°C/M at room temperature. Control the casting temperature in the furnace to effectively reduce the influence of temperature on oxidation burning loss. The higher the casting temperature, the more scum in the slag-breaking area, and the easier it is to form unqualified aluminum ingots such as pores.
Continuous Casting
Continuous casting production can minimize the contact time and area between molten aluminum and oxygen and can reduce the number of stirring and slag removal, so that the amount of aluminum ash produced is much lower than that of separate furnace casting, effectively reducing the output of waste aluminum quantity.
When adopting the traditional split-furnace casting, each furnace will produce a large amount of scrap aluminum (including chute aluminum skin, dross, scrap aluminum ingots due to insufficient flow, etc.). After adopting continuous casting production, the amount of waste aluminum is greatly reduced, and the average burning loss rate is about 7.33‰, which is 2-3‰ lower than the burning loss rate of 10.2‰ using single furnace casting.
Reduce Liquid Level Disturbance
The transfer of the aluminum liquid to the holding furnace and the casting process inevitably cause the disturbance of the original aluminum liquid to form a new aluminum liquid surface, which is oxidized in the air to form an A1203 layer.
With the disturbance of the aluminum liquid, new A1203 layers are continuously formed, which intensifies the oxidation burning loss.
When adding aluminum, it should be slow to prevent the violent disturbance of the aluminum liquid, reduce the contact area between the aluminum liquid and the air, and effectively reduce the oxidation of the aluminum liquid.
At the same time, the casting chute should be designed reasonably and try to use short-distance chute, low drop, and small flow resistance for production, so that the aluminum liquid can flow smoothly and reduce the contact area between the aluminum liquid and the air.
In Summary
Continuous casting production and strict control of process technology can effectively avoid the influence of long-term heat preservation of molten aluminum and excessive contact time between molten aluminum and oxygen. Although the burning loss in casting is inevitable in the production process, the above measures can effectively reduce the burning loss and improve the economic benefits of enterprises.