Firing silicon carbide refractories in a nitrogen atmosphere

Conclusions

During the firing of specimens of silicon carbide and silicon in a nitrogen atmosphere at 1200–1400°C, the silicon is converted almost completely to silicon nitride. The content of impurities of SiO₂ and Si varies from 1.7 to 1%, and from 2.8 to 0.5% respectively.

The compressive strength of the specimens, depending on the firing temperature, is 2500−1750 kg/cm², the porosity 17–18%, and the solubility in cryolite-alumina melt 10.0−2.5μ/h.

The minimum firing temperature of the specimens is 1200°C, and the soaking time at this temperature should not be less than 6 h. The maximum firing temperature is 1400°C with a 3-h soak.

Silicon carbide refractories for the linings of aluminum electrolyzers need to be fired with a staged cycle, with soaking periods at 1200 and 1400°C.