In order to join the workpieces by means of spot welding they must be precisely aligned with each other, as correction after welding is not easy.
2) Pressing on the electrodes
Suitable electrodes are chosen for welding the workpieces. These are mostly made of copper alloys with fractions of tungsten and molybdenum, which can withstand the high temperatures and pressures.
3) The current is flowing
If the electrodes have been positioned correctly, the current is switched on, which flows from one electrode to the other with a very high power. The material is heated so much that it liquefies and so both workpieces join.
4) The workpiece are tightly joined
The time during which the electrical current must flow through the workpieces varies, depending on the material and workpiece thickness. If the parts are tightly joined, the electrodes are removed in order to repeat the process at the next welding point.
This welding procedure can be repeated as often as necessary, depending on the workpiece size. Therefore, despite the small spot welds, a high degree of stability can be achieved.
Spot welding is generally used in sheet metalworking or, for example, for joining steel sheets in vehicle body production and vehicle production. As the force of the pressure produces internal joining of the molten metals, non-weldable raw materials can also be joined, subject to limitations. Spot welding is rarely used for aluminum.
Due to the concentration of high pressure on a relatively small area, within a very short time and high energy in the form of electrical current (up to 40,000 A), a very strong joint is produced by spot welding. In spot welding the welding control and welding parameters are decisive for durability. The influencing variables are controlled by the flow rate and temperature of the cooling water – which cools the welding electrodes -, the surface of the workpiece, the grade and thickness of the components.