What are the steps involved in forming the joint of a seam welding machine?

The seam formation process of the seam welding machine requires each welding point to undergo three stages: pre compression, electric heating, cooling, and crystallization. However, due to the rapid changes in the relative position between the roller electrode and the workpiece during seam welding, these three stages are not as obvious as in spot welding. You can consider the following situations.

1. Under the direct pressure of the roller electrode, the metal heated by electricity is in the "electric heating stage".

2. The adjacent metal that is about to enter below the roller electrode is subjected to a certain preheating and partial pressure by the roller electrode, and is in the "pre pressing stage".

3. On the one hand, the adjacent metal that has just emerged from under the roller electrode begins to cool down. At the same time, it is under partial pressure from the roller electrode and in the "cooling crystallization stage".

Therefore, the welding area under the roller electrode and the adjacent metal material will be at different stages simultaneously. For any welding point on the weld seam, the process under the roller consists of three stages: pre pressing, excitation, heating, cooling, and crystallization. Due to the fact that the process is carried out under dynamic conditions, the pressure effect during the preloading and cooling crystallization stages is insufficient. The quality of seam welded joints is usually worse than that of spot welded joints, and they are prone to defects such as cracks and shrinkage cavities.