Spot welding

Spot welding is a high-speed, economical connection method. It is suitable for producing stamped and rolled sheet members that can be overlapped, the joints do not require airtightness, and the thickness is less than 3mm. It is to weld the individual points of the weldment on the contact surface of the joint. Spot welding requires the metal to have good plasticity.

When welding, first clean the surface of the weldment, then lap and assemble the welded sheet, press it between the two columnar copper electrodes, and apply pressure P to compress it, as shown in Figure 2. When a sufficiently large current is passed, a large amount of resistive heat is generated at the contact of the plates, and the metal in the hottest area in the center is quickly heated to a highly plastic or molten state, forming a lens-shaped liquid molten pool. Continue to maintain the pressure P, disconnect the current, and after the metal cools, a solder joint is formed.

Spot welding is only used for the welding of thin-plate lap structures and metal meshes, cross-reinforced steel structures, etc., which do not require sealing due to a certain distance between the welding points. If the cylindrical electrode is replaced with a disc-shaped electrode, the electrode is pressed against the weldment and rotated, and the weldment is continuously fed between the disc-shaped electrodes, and then energized in a pulsed manner. A continuous and overlapping weld can be formed to form a weld, which is seam welding. It is mainly used for the welding of thin-plate overlapping structural parts with sealing requirements or high joint strength requirements, such as fuel tanks, water tanks, etc.