Production process of cast-cast corundum brick - oxidation e

In order to produce carbon-free and less-porosity (less shrinkage) cast-cast corundum bricks, the oxidative melting method (exposure arc method) production process is generally employed. At the same time, an oxygen bubbling method in which an oxidizing agent is added or an oxygen blowing method is applied.

 

It is impossible to completely exclude the pores and shrinkage cavities inside the brick in the cast corundum brick. There are three main possibilities for forming the gas of the fused pores of the cast brick: one is that a small amount of air is brought along with the raw material during the production of the feed; the other is that during the electrofusion process, the carbon powder on the electrode enters the melt and is oxidized. Part of the oxygen in the material forms CO or CO2 gas; the third is the decomposition of residual burning matter and hydrate in the raw material. The presence of these gases has a direct and indirect effect on the formation of pores and expansion of the pores.

 

Another important reason for the formation of shrinkage cavities is that the volume density of the cast-cast corundum bricks is greatly reduced upon melting, resulting in a large volume expansion. For example, the true density of the corundum brick is 3.99 g/cm3, but when the alumina is melted at 2052 ° C, the bulk density is only 2.98 g/cm 3 . 5%。 The molar volume of the melt increased significantly, the increase was 23.5%. And as the melting temperature increases, its density continues to decrease.

In the case of casting a corundum brick without adding an admixture, the temperature of the molten pool should reach 2200 to 2300 ° C. In this case, the melt has a large expansion, and the volume expansion under the action of the gas inside the melt, Therefore, after the casting is cooled, a large shrinkage hole is inevitably generated.

 

In order to reduce the shrinkage of the cast brick, a small amount of the additive is added to the furnish to lower the melting temperature, thereby reducing the volume expansion of the melt, and at the same time, oxygen blowing is used in the smelting process. The oxygen blowing method can play the dual role of stirring and decarburization. In the casting process, the mold used is attached with a compensation riser, and the operation method of side vibration and side casting is used in the casting.