The key ring bodywork is a resistance welding, bolts, nuts, spot welding, and stud welding. Body structure depends on the quality and reliability of hundreds at the body spot welding.
The progress of modern technology, the focus is the use of better materials to improve the body resistant to corrosion, and the body becomes lighter and stronger. Therefore, over the past 20 years has been a steady increase in demand for thin coating steel. Recently, the growing demand for high-tension material with anti-rust coating. Although these materials continue to improve, but the spot welding process or continue a lot of new technical barriers.
This article does not make the introduction of new Welding Material technology, but rather trying to explain the use of new materials the Welding Electrode management changes, in order to obtain a better quality of spot welding.
Reason for the change of the electrode surface
In the resistance welding process, the two copper electrodes under pressure, and Joule heat is generated between the steel to be welded, in this process will produce a steel stick together nugget.
For the galvanized steel sheet, the galvanized layer during welding occurs melt infiltrated electrode, stacked on the electrode surface. In the resistance welding process, because HTHP layer Cu5Zn8 of (copper-zinc) alloy layer will be deposited on the electrode.
Repeatedly stacked, the electrodes will be stacked layer covering, and ultimately damage to the electrode, and may even cause electrode breakage. Some alloy layer will be peeled off from the electrode to stick to the metal plate, thereby causing the body surface defects. Alloy layer will drop the part, but most still stick to the electrode surface, the current is reduced by the welding conditions worse, and even the formation of cold welding. It is necessary to take some measures to clean the electrode surface, and maintain good welding conditions.
In addition to the galvanized material accumulation problem, the electrode shape, cooling condition, steel, coated, and the torch may cause the electrode deformation or fracture. Raise the current methods of electrodes disadvantage, because the larger current causes the electrode cap end portion becomes soft, prompting galvanized material diffusion electrode, resulting in the buildup of the electrode surface is thicker.
Electrode surface analysis
The analysis of the electrode alloy layer need to use the following equipment:
· Electrode: copper chromium zirconium electrode cap diameter 16mm (concave cap)
Robot: 150kg
· Welding torch: C-type gun
· Steel: galvanized material (thickness t = 1.0mm, t = 1.2mm)
· The welding technical requirements: optimum welding quality
· Spot welding length: 100,300,400,500
Penetration in the surface of the end portion of the electrode cap, the molten zinc and the steel to form an alloy layer. Alloy layer component of approximately 79% iron, zinc 13%, 6% copper, 0.8% chromium, 0.8% aluminum.