Molybdenum Electrode Selection for Glass Electric Melting Furnaces: Furnace Type, Current Density and Purity Grade

1. Start with the furnace type: electrodes play different roles in all-electric and boosting furnaces

Glass electric melting furnaces can be divided by power supply into all-electric furnaces and electric boosting furnaces. An all-electric furnace relies on electrodes to input all the melting heat into the glass melt, with the electrodes immersed in high-temperature glass melt over the long term, so current density and electrical power directly determine melting capacity; a boosting furnace combines flame and electric heating, with electrodes supplementing heat and stabilizing the temperature field, commonly arranged on the sidewall or bottom of the tank furnace. The two operating conditions differ markedly in requirements for molybdenum electrode specifications, arrangement and replacement rhythm, so the furnace type and power supply regime should be clarified before selection.

The reason molybdenum electrodes have become the mainstream electrode material for glass electric melting lies in molybdenum's high melting point, good high-temperature strength and relatively stable chemical behavior toward most glass melts.

2. Current density and electrode cross-section: the main calculation thread in selection

The core parameter in glass electric melting furnace electrode selection is the working current density. The industry generally keeps the continuous working current density of electrodes in the 1–3A/cm² range: at the high end, self-heating of the electrode intensifies, end temperature rise becomes pronounced and service life shortens; at the low end, the electrode cross-section is oversized and investment rises. After determining furnace electrical power and supply voltage, first estimate the working current, then back-calculate the electrode cross-sectional area from the current density, which maps to a diameter specification. Standard rod electrodes cover Φ20–100mm; plate electrodes are custom-made to drawing.

3. Material purity and standard compliance

Purity directly affects the high-temperature stability of the electrode and the risk of contaminating the glass melt. The YS/T 1312-2019 industry standard Electrodes sets requirements for molybdenum main content and other indicators, and the industry-wide lower limit for main content is ≥99.93%; for high-purity batch melting applications, the electrodes we supply have a molybdenum main content of ≥99.95% and can be customized to higher purity. For a detailed comparison of purity grades and the effects of impurities, see High-Purity vs Standard Molybdenum Electrodes.

4. Structural form and water-cooling configuration

Beyond the high-temperature section, attention must also go to the design of the room-temperature connection section: the water-cooling jacket isolates the electrode cooling zone from the furnace body, and the conductive clamp handles the low-resistance connection. At the selection stage, check cooling water flow, clamp contact surface and furnace wall opening dimensions to avoid rework during on-site installation.

5. Customization by operating conditions and sample validation

For process notes on power supply, arrangement and operation control, see the technical process guide.

Voltage levels, glass recipes and continuous operating cycles vary widely between furnaces, and copying general specifications often fails to balance life and energy consumption. We recommend proceeding through the sequence of furnace type confirmation, power estimation, cross-section selection and structural refinement, with sample validation on the line first. We will provide selection recommendations based on your furnace drawings and power supply parameters, and support sample requests in standard specifications (1–2 pieces per company, shipping charges payable on delivery).