Natural Colour Heating Recommendations

Heating recommendations for silicon carbide crucibles (Suprex)After installation in the furnace, the crucible should be heated up slowly to a temperature of 200oC (392oF) over a period of 2 hours, to eliminate any moisture that may be present. Afterward, Silicon Carbide crucibles should be heated up to a temperature of 950oC (1742oF) on full power, if possible. Silicon Carbide crucibles used in a melting operation can be continuously heated up on full power until working temperature is reached. The crucible is then ready to be charged with care. When using Silicon Carbide crucibles for holding, the temperature of 950oC (1742oF) should be reached and held for approximately 1 hour. This ensures even melting of the glaze with the additional anti-oxidation coating, which is essential to achieve the maximum possible crucible life. For holding crucibles this procedure should be carried out periodically, but always before starting up again after a cool down period. This helps to compensate for the negative effects of low holding temperatures. Each time the crucible is heated up after a cooling down phase, it should be heated following the procedure laid down for the first installation. However, the drying time of 2 hours can be omitted. Should the Silicon Carbide crucible not be used for a longer period, it will be necessary to eliminate moisture, which may have been absorbed from slag. In this case, the crucible should be heated up to a temperature of 200oC (392oF). After reaching this temperature, further heating should be continued as per the first installation. The above recommendations refer to the use of new crucibles in existing furnaces. When installing a new Silicon Carbide crucible into a new furnace, the heating and drying instructions of the furnace manufacturer should be followed. If the furnace manufacturer prescribes a longer heating cycle (or curve), this procedure should be carried out without the crucible installed. It is essential that the crucible is installed in an absolutely dry furnace