Refractory for melting and holding furnaces

The melting furnaces commonly used for melting and alloying of primary aluminum ingots and waste aluminum are mostly fixed or tilting reflector furnaces that use gas or oil, as well as resistance reflector furnaces and induction crucible furnaces.

Although the temperature of liquid aluminum and aluminum alloy in the melting furnace is only 700~800℃, but the magnesium, silicon and manganese in aluminum and its aluminum alloy are very active, very easy to react with some components in the refractory, causing damage to the refractory. The erosion damage mechanism of aluminum melting furnace is mainly as follows:

(1) Aluminum liquid is easy to penetrate into refractory materials;

(2) The alloy-elements in aluminum and its alloys have a strong reducing ability to some oxides, and the REDOX reaction that occurs is a strong exothermic reaction; Some alloying elements such as magnesium have high vapor pressure, which is easier to penetrate refractories than liquid aluminum, and then oxidize to infiltrate refractory materials, resulting in deterioration of refractory materials, loose structure and damage.

(3) In the smelting process of large aluminum melting furnace, aluminum ingots and alloys are constantly added, and aluminum ingots and alloy blocks impact and wear the furnace mouth, bottom and wall very seriously;

(4) The addition of aluminum ingots and alloy blocks, the outflow of aluminum liquid and the fluctuation of temperature in the furnace, etc. cause thermal shock damage to the lining of refractory materials.

 

Refractories used in aluminum smelting and reflection furnace are required to resist the infiltration of aluminum liquid and magnesium vapor, and have excellent wear resistance and thermal impact resistance, etc. The furnace lining contacting aluminum liquid in aluminum smelting and reflection furnace is generally constructed with high aluminum bricks with Al2O3 content of 80%~85%. Mullite or corundum bricks are used in the smelting of high purity aluminium. Silicon nitride bonded silicon carbide brick is used in the furnace bed slope and the sites easy to corrode and wear out, such as loading waste aluminum material. Flow of aluminum groove and aluminum mouth and other parts, aluminum liquid scour is serious, generally using self-binding or si3n4 combined silicon carbide brick, also useful zirconite brick lining. The vacuum casting refractory fiber has a good effect. Non - contact aluminum lining, usually clay brick, clay refractory castable or refractory plastic. The inner lining of fluted aluminum groove is usually made of silicon carbide brick or prefabricated brick of fused silica foam brick.

At present, with the large scale of aluminum melting furnace and the requirement of smelting intensification, the high strength anti-aluminum permeable castable has been well applied due to its excellent anti-aluminum liquid and magnesium vapor infiltration performance, excellent anti-wear and thermal impact performance.