Spot welding is actually a type of electric welding, which relies on the instantaneous high temperature of the current to dissolve the welded object onto another object in contact, and then weld it together. An electric soldering iron is a handmade soldering tool that requires heating the soldering iron tip to above 300 ℃ for effective soldering.

1.Spot welding head for mild steel Projection welding of mild steel is widely used. The following table shows the welding conditions of spherical and conical projection welding. 2.Projection welding of coated steel plate Projection welding of coated steel sheet has fewer problems than seam welding, the reason is that the current is current is concentrated on the bumps.Even if the coated metal at the contact is first melted and diffused, there will be ni reduction in current density such as spot welding and seam welding.In addition, due to the large contact surface ans low current density of the plane electrode of projection welding, both the adhesion of the plating layer and the deformation of the electrode are relatively small. 3.Projection welding of PVC plastic surface steel plate This kind of steel plate has an insulating PVC plastic layer on one side, and it can only be welded by single-sided single-point or single-sided double-point welding.In order to protect the adhesive plastic surface from being damaged, it is necessary to use a shorter time for welding.Generally,half a week of electricity is used to control the heat time and heat, even shortened to 1/6 week or use energy storage welder for short time welding.In order to ensure that the plastic-coated surface does not have the same obvious indentation, the steel plate backing plate with the same pattern as the plastic-coated steel plate is usually.

There are two shapes of precision spot welding tips: sector and conical. The conical shape can imporve the rigidity of the bumps  and prevent premature crushing when the electrode pressure is high; It can be also reduce the splash caused by excessive current density. But sector shape bumps are usually used. In order to prevent the extruded metal from remaining around the bumps and forming gaps between the plates, bumps with annular overflow grooves are sometimes used. In multi-point projection welding, the inconsistent height of the bumps will cause the imbalance of the current at each point and make the joint strength unstable. Therefore, the height error of the bump should not exceed ±0.12mm. If the preheat current is used, the error can be increased.