Causes of Electrode Sticking Phenomenon in Medium-Frequency Inverter Spot Welding of Galvanized Steel Sheets？

Galvanized steel sheets are commonly used in various industries due to their excellent corrosion resistance. However, when welding galvanized steel using a medium-frequency inverter spot welding machine, a phenomenon known as electrode sticking can occur. This article aims to explore the causes of electrode sticking in medium-frequency inverter spot welding of galvanized steel sheets and provide insights into how to mitigate this issue.

1. Zinc Vapor and Contamination: One of the primary causes of electrode sticking in welding galvanized steel sheets is the release of zinc vapor during the welding process. The high temperatures generated during welding can vaporize the zinc coating, which then condenses and adheres to the electrode surfaces. This zinc contamination forms a layer that causes the electrodes to stick to the workpiece, leading to difficulties in electrode separation.
2. Formation of Zinc Oxide: When the zinc vapor released during welding reacts with atmospheric oxygen, it forms zinc oxide. The presence of zinc oxide on the electrode surfaces exacerbates the sticking issue. Zinc oxide has adhesive properties, contributing to the adhesion between the electrode and the galvanized steel sheet.
3. Electrode Material and Coating: The choice of electrode material and coating can also influence the occurrence of electrode sticking. Certain electrode materials or coatings may have a higher affinity for zinc, increasing the likelihood of sticking. For example, electrodes with a copper-based composition are more prone to sticking due to their higher affinity for zinc.
4. Insufficient Electrode Cooling: Inadequate electrode cooling can contribute to electrode sticking. Welding operations generate significant heat, and without proper cooling mechanisms, the electrodes can become excessively hot. The elevated temperature promotes the adhesion of zinc vapor and zinc oxide to the electrode surfaces, resulting in sticking.

Mitigation Strategies: To reduce or prevent electrode sticking when welding galvanized steel sheets with a medium-frequency inverter spot welding machine, several strategies can be employed:

1. Electrode Dressing: Regular electrode dressing is essential to remove zinc buildup and maintain clean electrode surfaces. Proper electrode maintenance helps prevent the accumulation of zinc vapor and zinc oxide, minimizing the occurrence of sticking.
2. Electrode Coating Selection: Choosing electrode coatings that have low affinity for zinc can help reduce sticking. Coatings with anti-stick properties or coatings specifically designed for welding galvanized steel can be considered.
3. Adequate Cooling: Ensuring sufficient cooling of the electrodes during welding is crucial. Proper cooling mechanisms, such as water cooling, can effectively dissipate heat and prevent excessive electrode temperature rise, minimizing the likelihood of sticking.
4. Optimization of Welding Parameters: Fine-tuning welding parameters, such as current, welding time, and electrode force, can help reduce sticking. By finding the optimal parameter settings, the welding process can be optimized to minimize zinc vaporization and sticking.

The occurrence of electrode sticking in medium-frequency inverter spot welding of galvanized steel sheets is primarily attributed to the release of zinc vapor, the formation of zinc oxide, electrode material and coating factors, and insufficient electrode cooling. By implementing strategies such as regular electrode dressing, selecting appropriate electrode coatings, ensuring adequate cooling, and optimizing welding parameters, the sticking issue can be mitigated. These measures will contribute to smoother welding operations, improved productivity, and higher quality welds when working with galvanized steel sheets.