Spot welding, as an important metal connection technology, has various methods and characteristics. According to the direction of the electrode current and the number of welds that can be formed in one spot welding cycle, we can divide spot welding into the following types:
1. Double-sided single spot welding
In this method, electrode 1 and electrode 2 are located on the upper and lower sides of the weldment 3, respectively, for precise single-spot welding. The advantage of this welding method is that the electrode force is strong and the welding current can be highly concentrated in the welding area, thereby effectively reducing the heating range of the weldment and significantly improving the welding quality. Therefore, if conditions permit, we should give priority to using this efficient spot welding method.
2. Single-sided double spot welding
Single-sided double spot welding means that both electrodes are located on the same side of the weldment for welding, and two welds can be formed at the same time. This method is particularly suitable for weldments with large structures, complex shapes, and difficult movement, while ensuring that one side of the weldment remains traceless. However, during the welding process, part of the current may directly pass through the weldment above to form a shunt, causing the weldment to warp and deform. In order to effectively reduce shunt, we usually add a copper pad under the weldment so that most of the current flows through the copper pad with excellent conductivity, thereby ensuring the stability of the welding current density. In addition, since the electrode force used is limited by the rigidity of the weldment, we should use a rigid jig with a copper pad for assistance. This method has been widely used in the production of large structures such as automobiles and passenger car compartments.
3. Single-sided single-spot welding
In single-sided single-spot welding, the two electrodes are also located on the same side of the weldment, but one of the electrodes only acts as a conductive block. This method is similar to single-sided double-spot welding in characteristics and is mainly used for structures that cannot use double-sided single-spot welding.
4. Double-sided double-spot welding
Double-sided double-spot welding uses two welding transformers to supply power to the paired electrodes on the upper and lower sides of the weldment respectively. To ensure the welding effect, the wiring direction of the two transformers should ensure that the polarity of the upper and lower paired electrodes is opposite during the welding time. In this way, the secondary circuits of the upper and lower transformers together form a complete welding circuit, and two welding spots can be formed at the same time in one welding. This method is characterized by small shunt, unrestricted electrode force, and high welding quality. It is particularly suitable for welding large components with thick plates. Despite its significant advantages, it is relatively rarely used in practical applications.
In summary, the diversity of spot welding methods provides us with a wealth of choices to meet different welding needs. When choosing a specific spot welding method, we should fully consider factors such as the material, shape, size, and welding quality requirements of the weldment to ensure the smooth progress of the welding process and the steady improvement of welding quality.
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