There are many factors that affect the colors of fused cast block, such as the melting atmosphere, the solubility of the impurities, the valence of multivalent ions, and the reaction between the mold sand and the molten glass.

The oxidizing degree, the residual carbon content and the valence of the transition element ions have a significant effect on the color of fused cast AZS block.

There are two methods for the production of fused cast AZS block: reducing method and oxidizing method. The fused cast AZS block made in the reducing way features dense structure and low viscosity glass phase, while the AZS made in the oxidizing method features good corrosion resistance.

In the reducing atmosphere, the multivalent ions are Fe2+ and Ti3+. FeO is black and the Ti3+ is purple. The residual carbon content is higher compared to the oxidizing method. All these factors make the fused cast AZS darker in color.

In the oxidizing atmosphere, the multivalent ions are Fe3+ and Ti4+. Fe3+ is red and TiO2 is red or orange-red. The residual carbon content is lower. Thus the fused cast AZS is light yellow or white.

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