As electric arc furnace steelmaking develops toward larger scale and higher power, the performance bottleneck of electrode joints has evolved from a simple “insufficient strength” issue into a systemic engineering challenge. It is concentrated in coupled failures across four dimensions: mechanical, thermal, electrical, and microstructural materials.
1. Structural Shortcomings in Mechanical Strength
The joint is the weakest link in the mechanical performance of the electrode column. Measured data show that the strength at the joint is only about 60% of the strength of the electrode body itself, and if there is a poorly connected “open joint,” its strength may even plummet to 25% of that of a solid column. In large electric furnaces, enormous electromagnetic forces, impact loads generated by scrap collapse, and mechanical vibration all act in a concentrated manner on this weak connection point, making it a high-incidence area for fracture accidents. In addition, insufficient thread machining precision or the presence of microcracks can create stress concentration points, further weakening its load-bearing capacity.
2. Thermal Expansion Mismatch and Thermal Stress Damage
Ultra-high-power electrodes and their joints usually need to adopt different formulations and processes to meet their respective requirements, which creates a hidden risk of mismatched coefficients of thermal expansion (CTE). When a huge current passes through the joint, the Joule heating effect combined with radiant heat from the arc causes the temperature in the joint area to rise sharply. If the thermal expansion behavior of the joint and the electrode body is inconsistent, even a slight CTE difference can generate enormous thermal stress at the thread root, and after repeated thermal cycles, fatigue fracture is highly likely to be induced. At the same time, severe temperature gradients, caused by the alternating action of temperatures reaching thousands of degrees at the end and cold scrap, also require the material to have extremely high thermal shock resistance, while the structural non-uniformity of the joint area often makes it the origin of thermal spalling or cracking.
3. A Vicious Cycle of Electrical Contact and Oxidation Loss
Contact resistance at the joint is the source of Joule heating. If there is a gap in the thread fit, or if the contact surface deteriorates due to oxidation, the contact resistance will increase significantly, thereby causing local overheating. This overheating not only intensifies material weakening, but also triggers oxidative attack in the joint gaps, reducing the effective load-bearing area of the threads and further increasing resistance, forming a vicious cycle of “increased resistance -> overheating -> intensified oxidation -> even greater resistance.” Loosening of the joint that may occur at high temperatures will also cause the contact state to deteriorate rapidly, possibly even leading to disconnection or burning damage.
4. Microstructural Uniformity and Manufacturing Defects
Macroscopic failure often originates from microscopic weaknesses. As a component requiring high density and high strength, the joint’s uniformity of graphitization, the bonding strength of the interface between aggregate and binder, and the morphology and distribution of pores directly determine its thermal shock resistance and fracture resistance. If there are areas inside the joint with insufficient graphitization, excessively large pores, or concentrated pore distribution, these locations will become “highways” for the preferential initiation and propagation of cracks under thermal shock and mechanical stress, causing the joint to fail under stress far below its theoretical strength.
In summary, the performance bottleneck of electrode joints in large high-power electric furnaces is a manifestation of the “bucket effect.” It is not the lag of a single indicator, but rather the result of four factors—inherently weak mechanical strength, difficulty in matching thermal expansion, susceptibility of electrical contact to deterioration, and difficulty in controlling microstructural uniformity—mutually coupling and mutually amplifying one another.
Post time: Sep-15-2026