Reasons for electrode sticking during welding

Thread Content

Sticking of electrodes refers to the adhesion between the electrodes and the parts that occurs when abnormal welding takes place during spot welding by welders; in severe cases, this can lead to the electrodes being pulled out, and the cooling water can cause the parts to rust. There are mainly four reasons for electrode sticking during welding: the working surfaces of the two electrodes are not parallel, the working surfaces of the electrodes are rough, the electrode pressure is insufficient, and the water pipe at the cooling outlet of the welding gun is connected in reverse or the cooling water circulation is blocked. 1. Non-parallel working surfaces of the electrodes: When the working surfaces of the two electrodes are not parallel, it leads to partial contact between the electrode surfaces and the part, increasing the contact resistance between the electrode and the part and resulting in a decrease in the current in the welding circuit. When current is concentrated at a local contact point, and the current density at that point exceeds that at the working surface of the electrode during normal welding, the temperature at the contact point rises to the weldable temperature between the electrode and the part, resulting in fusion between them. 2. Rough working surface of the electrode: The working surface of the electrode does not fit perfectly against the part; only some protruding areas come into contact with the part. This situation also leads to the two electrode surfaces not being parallel, resulting in electrode sticking. 3. Insufficient electrode pressure: Contact resistance is inversely proportional to pressure. Insufficient electrode pressure increases the contact resistance between the electrode and the part, leading to increased heat generation at the contact point. This raises the temperature of the contact surface between the electrode and the part to a weldable level, thereby enabling fusion bonding between the electrode and the part. 4. The water pipe at the welding gun’s cooling outlet is connected in the wrong direction, or the circulation of cooling water is impaired; this leads to an increase in the electrode temperature, and during continuous spot welding it can result in a fused connection between the electrode and the part. All of the above four situations can easily lead to a fused connection between the electrode and the part, resulting in electrode sticking. So, how can we avoid the occurrence of electrode sticking? (1) File the electrode tips so that the working surfaces of the two electrodes are parallel and free of roughness defects. The welding program can be selected as a grinding program (with no current output), and the weld gun can be operated without making a connection in order to check whether the working surfaces of the two electrodes are parallel. (2) In the grinding state, perform 5–10 blank welds to forge the working surfaces of the two electrodes, thereby increasing the contact area within the specified electrode tip diameter range and simultaneously enhancing the surface hardness. (3) Heating the working surface of the electrode with an oxy-acetylene flame to form an oxide layer on it can increase the melting point of that surface; at the same time, it undermines the weldability between the electrode and the part. (4) Apply the red lead provided by the welder to the working surface of the electrode in order to disrupt the weldability between the electrode and the part. (5) Adjust the electrode pressure, using welding parameters with high pressure, a large power supply, and a short power-on time. (6) Regularly clean the cooling water pipes to ensure an adequate flow of cooling water. The above are all measures that can address the issue of electrode sticking during welding.