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Electrode Paste Resistivity: Is Lower Always Better?

Electrode paste resistivity is one of its key performance indicators, significantly impacting the operation of submerged arc furnaces for calcium carbide and ferroalloys. The resistivity directly affects the electrode's sintering characteristics, conductivity, and thermal stability, thus influencing production efficiency, energy consumption, and safety. It's well known that lower resistivity equates to better conductivity; however, is lower resistivity always better? Not necessarily.

Problems Caused by Excessively Low Resistivity

When resistivity is too low, the electrode itself doesn't heat up sufficiently, causing the sintering rate to lag behind the consumption rate, potentially leading to electrode softening, deformation, or "paste runoff." Softened electrodes are difficult to control stably, affecting furnace stability. Incompletely sintered electrodes have low mechanical strength and are easily damaged under furnace stress. Low resistance can also cause current to concentrate in a specific part of the electrode, leading to localized overheating while other areas react incompletely. Insufficient electrode heating can affect furnace mouth temperature, causing the reaction zone to shift upwards, reducing thermal efficiency. Uneven furnace temperature can also lead to unstable product composition.

Problems Caused by Excessively High Resistivity

Let's discuss another scenario—when resistivity is too high. High resistivity means high heat generation, which may lead to premature sintering of the outer layer of the electrode while the interior remains insufficiently sintered, resulting in a "half-burnt" electrode. A large temperature difference between the inner and outer layers can easily cause cracks, reducing the electrode's mechanical strength. Furthermore, excessive self-heating of the electrode reduces the effective energy available for the furnace reaction, leading to increased power consumption per unit product. Poorly sintered electrodes are prone to breakage and detachment, causing production stoppages or even safety accidents.

Conclusion

The ideal resistivity range for the electrode paste needs to be determined based on the specific furnace type and process conditions. The optimal resistivity range must be determined through experimentation and comprehensively optimized in conjunction with other electrode paste indicators (such as volatile matter and strength) to ensure efficient, stable, and safe operation of the submerged arc furnace.