The topography change of electrode tips at resistance welding of deep drawn steel DC05+ZE

During resistance welding, the electrode tips are significantly worn. The amount of wear is strongly dependent on the welded material, the surface treatment of the welded sheet, the thickness of the surface treatment, the welding parameters and, last but not least, especially on the number of performed welds. The paper describes the change in topography (RedLux optical profilometer) and roughness (Mitutoyo roughness tester) of the contact surface of the electrode tip during the wear process (thus depending on the number of welds performed). It also deals with the change of welding parameters due to the change in the size of the actual contact area. Deep drawing steel DC05 + ZE (EN 10152) electrolytically coated with Zn (with a total thickness h = 0.7 mm and a zinc coating thickness of 4.5 μm) was used as the experimental material. The roughness of the contact surface increases evenly. It reaches a maximum after about 100 welds and then decreases. The welding current also increases evenly. It is kept constant between 200 and 350 welds and then grows again.