30+ YEARS OF EXPERIENCE IN CARBON INDUSTRY

During the use of the electrode paste, power outages occur occasionally. Such power outages are highly likely to cause the electrodes to break. Specifically, power outages can affect electrodes in the following ways:

1. Thermal Shock Leading to Physical Damage (Hard Breakage)

   When the current is suddenly interrupted, the powerful Joule heat source of the electrode disappears instantly. The exposed parts of the electrode quickly dissipate heat to the environment, causing surface contraction. The interior of the electrode, especially the center, remains in a state of high-temperature expansion due to slower heat dissipation. This temperature difference between "cold outside and hot inside" generates enormous tensile stress. If the electrode paste has insufficient thermal shock resistance (i.e., poor thermal conductivity and low strength), this stress can quickly lead to microcracks inside the electrode, and in severe cases, breakage (i.e., "hard breakage") can occur instantly or shortly after power is restored.

   
   

2. Interruption and Fluctuations in the Sintering Process

   Electrode paste undergoes a continuous sintering process from raw material to sintered material, and power outages disrupt this balance. During a power outage, the overall temperature of the electrode drops. Electrode paste, originally in the ideal sintering zone (usually near the lower cone of the electrode holder), stops sintering due to insufficient heat. When power is restored, heat needs to accumulate again, causing the electrode to sinter higher than normal. If the power outage is prolonged, the sintered layer at the electrode's working end (the part inserted into the charge) may be damaged, resulting in some of the electrode that should have been sintered becoming "raw paste." Raw paste has extremely low strength and cannot withstand significant mechanical friction and high-temperature erosion, easily leading to electrode soft breakage or a sharp increase in wear.

   
   

3. Increased Risk of Electrode Soft Breakage

   Soft breakage typically refers to the outflow of the electrode's internal paste core. During normal operation, the electrode shell is heated by current, and the internal raw paste gradually sinterstalizes into a carbon skeleton. After a power outage, the electrode shell cools much faster than the internal paste. When power is restored, if the electrode is inserted too deeply into the charge or for too long, the electrode shell rapidly expands due to heat, while the internal paste may not be fully sintered or may still be fluid. Expansion of the electrode shell can lead to weld cracking, allowing unsintered raw paste (or even liquid-phase pitch) to leak out, resulting in a soft fracture. This is typically accompanied by large arc flashes and deterioration of furnace conditions.

   
   

4. Damage to the Electrode Shell from Thermal Expansion and Contraction

   Repeated power outages and restorations (thermal cycling) can cause thermal fatigue in steel electrode shells. During expansion and contraction, the steel shell may bulge, crack the weld, or detach from the internal paste (forming an air gap). Once an air gap forms between the electrode shell and the paste, current conduction is obstructed, generating a localized arc, further burning the electrode shell and creating a vicious cycle.

   
   

In short, the impact of power outages on electrodes can be summarized as follows: thermal stress can cause hard fracture, while temperature drops can lead to poor sintering and soft fracture.