Corundum formation and its subsequent destruction of the furnace lining can be a constant worry to the maintenance department. The picture below is all too common of a reality in a typical Aluminium Foundry.

The following conditions facilitate corundum formation:

• Excessive free silica in the refractory.

• Excessive amounts of sodium, either in the refractories or in the fluxes.

• Refractory products that do not have any non-wetting agents.

• Inefficient burner operation carbonizes deposits on the refractory, thus rendering it wettable by molten aluminIum. Carbon deposits would occur if the burners are not runnning properly.

• Negative furnace pressure, thus aspirating oxygen into the furnace.

• Excessive temperature, e.g., 850°C plus and it would be worst if burner`s flame beats the lining.

* Same as above, if electric roof heaters are very close to linings not having good properties against aluminium.

As you can see by the above points, there are multiple factors that go into corundum formation. We want to make it clear that there is no one factor that will eliminate corundum.

Also, the formation cannot be solved by refractory selection alone. This helps but we need to go to the root cause.  Aluminium producers must make an analysis and clean the furnaces on a regular basis in order to reduce the chances of  corundum build ups.

Do not hesitate to contact us if you need further information.