This paper describes a novel method for laser lap welding of zinc-coated sheet steel commonly used in automotive body fabrication. Problems associated with laser welding of such material are first described along with the limitations of current methods used in industry. This is followed by the description of a new zero-gap, alloying-based technique for producing better welds. In addition, a method for in-process quality monitoring of such welds is also discussed. The work presented here was carried out keeping in mind its implementation feasibility on actual production floors The experiments with copper were found to be very promising. Sandwiched copper not only ensured a zero-gap, but also actively participated in controlling vigorous boiling of zinc - the main cause of weld porosity and spattering. Comprehensive weld analysis indicates that addition of copper produces mechanically acceptable welds. Minimal presence of copper in the weld zone and extended solid solubility due to non-equilibrium processing rules out the possibility of hot cracking or other defects in the welds. A U.S. Patent (No. 6,479,168) has already been issued for this method and a refined version is pending for international acceptance. Results from spectroscopic study of zinc emission have led to accurate understanding of zinc behavior during welding. Higher zinc intensity in the plasma indicates deterioration in weld quality. Another U.S. patent is pending for this type of monitoring and/or control of process and resulting sensors. The ease of integrating the process of copper addition with existing automation systems on shop floors promises a robust solution to automakers. This new method which takes care of imprecise stampings/fixturing and does not demand huge capital investment, can be used with zinc emission sensors to make high quality, repeatable welds on zinc-coated steel.
A novel method for lap welding of automotive sheet steel using high power CW CO2 laser
Ein neuartiges Überlappschweißverfahren für Kraftfahrzeugstahlblech mit einem Hochleistungs-CW-CO2-Laser
2005
6 Seiten, 10 Bilder, 16 Quellen
Aufsatz (Konferenz)
Englisch
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