Aluminum Melt Purification Treatment in Casting Foundry

The aluminum melt purification treatment technology is the first key process that determines the application of aluminum alloy materials. It determines whether aluminum alloy materials have the heritability of metallurgical defects and high performance, and dominates its application and development in various fields.

Aluminum Melt Purification Treatment

The company’s aluminum alloy melt purification treatment mainly uses furnace flux refining and static slag removal processes. The removal of static slag is based on the density difference between the non-metal oxide and the alloy liquid itself. In a certain period of time, the non-metal oxides are separated from the alloy liquid to achieve the purpose of purifying the aluminum liquid. This article aims to determine the optimal residence time of molten aluminum through experiments.

The test furnace is a 20-ton aluminum alloy static furnace. The purpose of the static furnace is to remove the slag and keep it still, and fine-tune the composition of the molten aluminum mixture in the smelting furnace and the scrap aluminum furnace, thereby purifying the aluminum alloy liquid and providing high-quality aluminum alloy liquid for the next purification.

The molten aluminum in the smelting furnace and the scrap aluminum furnace enters the static furnace through the casting launder proportionally, and the temperature is increased. When the temperature reached 740°C or higher, 20 kg of slag scavenger was added to the powder sprayer, and the slag scavenger was blown into the aluminum alloy with nitrogen. The inside of the liquid undergoes a melt purification operation, and the slag is removed after 15 minutes of spraying. After the slag discharge is completed, it starts to stand still.

Immediately after slagging in the vertical furnace, the slag inclusion value of molten aluminum is higher. With the extension of the residence time, the slag inclusion value of molten aluminum gradually decreases. When the standing time is 15 minutes, the slag inclusion value of molten aluminum basically reaches a low value, and when the standing time is 15 minutes or more, the slag inclusion value of molten aluminum is basically stable with almost no change.

As the residence time increases, the slag inclusion defect rate of the alloy shows a downward trend. After the vertical furnace slag removal is completed, the defect rate of slag inclusions is the largest. In the first 25 minutes, the defect rate dropped significantly, and then basically stabilized with a defect rate of 0.05%.

When the standing time is 15 minutes, the slag inclusion value of molten aluminum basically reaches a low value, and if it is greater than 15 minutes, the slag inclusion value of molten aluminum is basically stable. When the standing time exceeds 25 minutes, the defect rate is basically stable. When the molten aluminum is left to stand for more than 25 minutes, the cleanliness of the molten aluminum can reach a better state, that is, the molten aluminum can be left to stand for at least 25 minutes, and then transferred to the next station.