Molybdenum is the ideal material for glass melting electrodes due to its good electrical and thermal conductivity, excellent corrosion and creep resistance. Generally, the diameter of electrode ranges from 10mm to 120mm, which is mainly depended on the current density.
To melt borosilicate glass, the most common diameter of electrode is 50mm. When the current density ranges between 0.42 A/cm2 and 0.49A/cm2, the electrodes do not need to be moved forward as they have no consumption. For vertical electrodes, whether the electrode to be continued in the furnace required to be evaluated when the density value reaches 0.8A/cm2.
For electric furnaces with a long furnace age (more than 4 years), the current density increases as the electrode is consumed. If the electrode is not ready to continue, the current density needs to be controlled at a lower value. Normally, there is little consumption for moly electrode when the current density runs below 0.6A/cm.
When molybdenum glass melting electrode is used to smelt soda lime glass and other low-resistance glasses that have a resistivity lower than 15Ω·cm, it is difficult to control the current density below 0.6A/cm2 because of its low viscosity and low resistivity. Therefore, electrodes with φ75mm diameter are often used. In addition, the electrodes will also have different degrees of loss during operation, so the electrodes must be made continuous. From the perspective of operating cost, the plate electrode consumes less and is more suitable for electrofusion of soda lime glass.
The conductive distance of the electrode has a direct impact on the service life of moly electrode. If the distance is too close, it will be in a low-voltage and high-current state during operation. This local high power will not only reduce the life of refractory materials, but also increase the electrode loss and bring defects to the product. In addition, if the current density value is too large, the destructive effect on the electrode will be even greater. Within the allowable range of voltage that the electric melting furnace can withstand, the high-voltage and low-current operation scheme can improve efficiency on conditions that it must meet the requirements of melting process and operational safety.
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