Spot welding machines are widely used to weld aluminum alloys, but the weldability of aluminum alloys is particularly poor, especially those strengthened by heat treatment. The reasons and measures taken are as follows: Aluminum alloys require higher current and shorter time to generate sufficient heat to form fusion nuclei, reduce surface overheating, avoid electrode adhesion and diffusion of copper ions to the aluminum coating, and reduce the corrosion resistance of the joint.

A narrow plastic temperature range and a high coefficient of linear expansion require the use of larger electrode pressure. Spot welding machines have good electrode follow-up to avoid cracks caused by excessive internal tensile stress during nucleation and solidification. For aluminum alloys with a high tendency to crack, spot welding machines must also use the method of increasing forging pressure to ensure sufficient plastic deformation during nucleation and solidification, reducing tensile stress to avoid crack formation. When the electrode is unable to withstand high forging pressure, the method of adding a slow cooling pulse after the welding pulse can also be used to avoid cracks. Several methods can be used in combination for thick aluminum alloys.

Due to the ability of convex points to concentrate current density, even if the zinc layer on the contact surface melts locally and spreads, it will not cause a decrease in current for convex welding of steel plates. Therefore, single-sided single point or single-sided double point methods are required. For the convex welding of galvanized steel plates, when encountering other coated steels, refer to the welding characteristics of galvanized steel, and adjust the welding parameters appropriately according to the conductivity, melting point, and thickness of the coating.

The height of the burrs often fluctuates, ensuring consistent welding quality. Secondly, due to the use of large-sized flat electrodes, both the adhesion of the zinc layer and the deformation of the electrode itself are very small, so the strength of the welded joint will not decrease with the increase of welding points.