New car body concepts are directly linked with innovative technologies. Generally, it is lightweight construction using ultra-high-strength steel, light metals such as aluminum and magnesium alloys, the use of fiber-reinforced plastics, or various combinations of all these materials in a single body structure.
New steel - new repair technologies
MIG brazing is a new joining technology, also called welding-soldering, used to join high-strength steels of the car body.
High-strength steels gained their hardness and stiffness values through heat treatment. But during conventional semi-automatic welding, the temperature of the weld pool is 1500-1600°C, which leads to changes in the characteristics of the joined metals and, consequently, to changes in the entire body structure. This indicates a low quality of the connection (oxidation, corrosion) and the lack of zinc coating in the place of welding.
The discovery of the MIG brazing method has made it possible to avoid such problems. Unlike welding, the brazing process does not destroy the zinc protective layer, much less damage the metal itself. MIG soldering is done at a lower melting point of approximately 900°C. There is no diffusion of metals, and due to the relatively low bath temperature, the inherent properties of the steels being joined are preserved.
This method almost eliminates the deformation of the joined metals. In addition, zinc burnout during soldering is minimal (zinc melts at 419°C, evaporates at 906°C). The resulting weld has a higher resistance to corrosion. The brazing wires are made of a copper-based alloy with silicon (CuSi3) or aluminum (CuAl8) additives. The solder combines with the zinc and the result is a highly corrosion-resistant weld.
Thin metal is not melted through when brazing with a semi-automatic soldering machine. Coated (phosphatized, galvanized, aluminized) and uncoated steel sheets can be brazed. The resulting joint is strong. The soldered joint has a higher mechanical strength and elasticity.
