Liquid aluminum

Release time:

Jul 15,2026

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How Should Liquid Aluminum Be Transferred?

Because high-temperature molten aluminum is easily oxidized and absorbs gas when exposed to air, siphon transfer is usually used to transfer liquid aluminum in order to maintain the cleanliness of the prepared alloy melt.
Before transfer, carefully check whether the siphon pipe is unobstructed. Connect the negative-pressure device to the compressed air pipeline with a rubber hose, and check whether the negative-pressure device operates flexibly. Bend the rubber hose and hold it by hand, then slowly open the fine-adjustment valve. The pointer of the vacuum gauge should indicate above 53.32 kPa, or 400 mmHg.
During transfer, the bottom of the aluminum ladle should be higher than the aluminum inlet of the mixing furnace. Insert the short end of the siphon pipe into the bottom of the aluminum ladle, and place the long end into the aluminum inlet of the mixing furnace. Then lift the siphon pipe by about 5 cm so that the short end leaves the bottom of the ladle.
Next, slowly start the negative-pressure device while observing the vacuum gauge. Allow the gauge pointer to rise to 39.99 kPa, or 300 mmHg. When the vacuum gauge rises from 0 to 26.66 kPa, or 200 mmHg, it may rise slightly faster. However, between 26.66 and 39.99 kPa, or 200 to 300 mmHg, it should rise slowly. If the fine-adjustment valve is opened too quickly, the aluminum liquid may rush upward at the top.
When the aluminum liquid in the ladle has been completely transferred, the vacuum gauge pointer will drop. At this time, close the fine-adjustment valve, slowly lift the siphon pipe, and then remove it. After transfer is completed, clean the residual aluminum liquid from the pipe wall to avoid burns.
To prevent accidents caused by siphon pipe blockage, the siphon pipe must always be kept in good condition. When the inner diameter of the siphon pipe is less than 100 mm, it should be removed and cleaned.

Why Should Molten Aluminum Alloy Be Stirred?

In aluminum alloy production, the uniformity of chemical composition is extremely important. Otherwise, it is difficult to ensure uniform product performance, and defective products may even be produced.
In electrolytic aluminum plants, the use of liquid charge materials and master alloys during batching can create favorable conditions for uniform chemical composition, but this alone cannot fully achieve the desired result. The dissolution of solid metal begins at the interface where it contacts the aluminum melt. A local high-concentration zone forms near this interface, while areas farther away from the solid-liquid interface become low-concentration zones.
The homogenization of chemical composition is essentially the diffusion of alloying elements from the high-concentration zone to the low-concentration zone. Stirring the melt can accelerate this diffusion process.
During melting, when an external heat source is used, the temperature of the aluminum melt near the heat source is higher, while the temperature farther away from the heat source is lower. For example, when a flame furnace is used, heat is transferred from the surface of the molten metal downward. The hotter metal stays in the upper layer, while the lower-temperature metal remains at the bottom of the furnace. Under static conditions, this temperature difference often reaches 100-200°C, and it increases as the melt depth and heat-source height increase.
Increasing the convection speed of the melt can accelerate heat transfer and quickly reduce this temperature difference. Therefore, the main purposes of stirring molten aluminum are:
To accelerate dissolution and make the chemical composition of the melt uniform.
To make the temperature of the aluminum melt uniform and avoid local overheating of the aluminum alloy melt.
In addition, stirring can accelerate the melting of solid metals and help non-metallic inclusions and gas bubbles float upward.
After alloying elements are added to the melt, the molten aluminum alloy must be thoroughly stirred in the mixing furnace. In small mixing furnaces or ladles, manual stirring may be used. However, in large furnaces, manual stirring is difficult and often cannot achieve uniform results.
In recent years, electromagnetic stirrers have been widely used. They are usually installed below the bottom of the mixing furnace. The stirring effect of an electromagnetic stirrer is much better than manual stirring, and it greatly reduces labor intensity.
No matter which stirring method is used, the chemical composition of the aluminum liquid must be made uniform. During stirring, the fluctuation of the aluminum liquid should be kept as small as possible. Since high-temperature molten aluminum is easily oxidized and absorbs gas in air, excessive fluctuation will reduce the cleanliness of the aluminum liquid. It will also increase slag formation, increase metal loss, and reduce the economic efficiency of production.

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