The welding electrodes transmit the welding current and the electrode force to the workpieces. They are the electrical conductors that mediate the transfer of current. The thermal conductivity of the electrode material and the shape and mass of the electrodes influence the heat balance of the welding process.
The demands on the electrodes and their materials are very complex and sometimes contradictory. In addition to good electrical and thermal conductivity, determined by the resistance of the material, the shape and mass, as well as the cooling, a high basic and hot hardness are essential for a long tool life. Furthermore, the tempering resistance, a high softening temperature and a low tendency to alloy with the material to be welded are important. To meet all these requirements, a compromise must be made in all cases.
Common electrode materials are copper-chromium-zirconium in various hardened qualities for spot, projection and roller seam welding of steel grades from coated to high-alloy. Furthermore, copper-cobalt-beryllium and copper-nickel/cobalt-beryllium are often used. For aluminium and for non-ferrous metals such as copper itself, special materials such as work-hardened mixtures of selenium-copper-silver or tungsten alloys are used.
The shape and contact surface of the electrodes are also very important. The shape is largely determined by the workpiece to be welded. Usually straight, angled or cranked point electrodes are used. For the contact surface, a distinction is made between crowned and flat electrodes. Spherical ones are preferred when you want to achieve better initial point contact between the electrode and the component.
The diameter of the electrode should be selected according to the required current density and for the transmission of the necessary electrode force.
More information on the correct choice of electrode shape and electrode material can be found in DIN ISO 5182, as well as in DVS leaflet 2903 and, of course, from your HWH partner.