The volatile content of electrode paste decreases with increasing temperature. As a result, as the electrode descends during the sintering process, the amount of volatile materials decreases, leading to a denser electrode. Volatile components in the electrode paste are primarily expelled from two sources. During the softening and melting process at temperatures ranging from room temperature to 250°C, volatile components with lower boiling points are released in small quantities from the top opening of the electrode cylinder. In the electrode sintering process, as the electrode volume contracts, gaps form between the electrode and the cylinder. Between 300°C and 500°C, a significant amount of volatile gases is generated, expelling from these gaps. This leads to a sharp reduction in the volatile content of the electrode paste. Beyond 650°C, the volatile content gradually diminishes to zero, aligning with the electrode temperature nearing 1000°C, signifying the completion of the sintering process and the formation of a compact electrode.
The electrical resistivity of electrode paste decreases with rising temperature. Within 200°C, the resistivity is relatively high, contrasting the resistivity of well-sintered electrodes by a factor of thousands. As the temperature rises to 300°C to 500°C, the evaporation of volatile components significantly lowers the resistivity. Continuing to 500°C to 800°C, the resistivity stabilizes to below 100 μΩ·m. At temperatures exceeding 800°C, the resistivity essentially remains steady, allowing the majority of electrical current to enter the furnace through the electrode.
Carbon materials exhibit higher strength at elevated temperatures but experience reduced strength after cooling. Prolonged power outages cause electrode cooling, and due to internal stresses, their strength can drop to half of their normal operational strength. Thus, minimizing instances of thermal shutdown is crucial, and appropriate measures should be taken to insulate electrodes after power loss. When reactivating electrodes, gradually increasing the load, mitigating heat and electrical shocks, and avoiding hard breaks are recommended practices.
