Uneven graphite electrode graphitization causes overheating and wear

Handan Qifeng Carbon Co., Ltd. has released an analysis explaining how uneven degrees of graphitization in graphite electrodes can cause localized overheating and abnormal wear. This phenomenon is critical for the efficiency and longevity of electric arc furnaces (EAFs) and submerged arc furnaces (SAFs).

The core issue stems from differing electrical resistivity. Well-graphitized areas have low resistivity, allowing current to pass easily. Conversely, poorly graphitized regions exhibit higher resistivity. As current flows through the entire electrode cross-section, the higher resistance areas generate more heat due to Joule heating (I²R). This uneven heat distribution creates "hot spots" where temperatures significantly exceed the average.

Furthermore, poorly graphitized areas possess incomplete crystal structures and lower thermal conductivity. Even if generating the same amount of heat, they cannot dissipate it effectively, leading to localized heat accumulation. This high temperature further degrades these regions, creating a positive feedback loop. The localized overheating also induces significant thermal stress due to inconsistent thermal expansion coefficients, potentially causing microcracks. These cracks reduce the effective conductive area, further concentrating current and intensifying overheating.

In the high-temperature environment of electric furnaces, especially with molten metal corrosion, poorly graphitized regions are more susceptible to oxidation from oxygen, slag, or molten metal. Their lower mechanical strength also makes them prone to spalling or slagging under thermal and electromagnetic stress. This results in irregular electrode shapes, distorted current distribution, and accelerated consumption.

Uneven graphitization also exacerbates problems at electrode joints, which inherently have higher resistance. Inconsistent graphitization near the joint can lead to increased contact and bulk resistance, causing rapid local heating. This can result in joint loosening, oxidation, or breakage, leading to abnormal electrode consumption. Handan Qifeng Carbon concludes that uneven graphitization ultimately translates to localized overheating and abnormal wear, manifesting as pitting, spalling, and a significant increase in electrode consumption per ton of steel.