By: Hongping Gu and Boris Shulkin
Stronach Centre for Innovation (SCFI)
With the advancement of high power fiber delivery lasers, remote laser welding becomes a reality and furthermore cost reduction on a new laser system in recent years drives adoption of laser welding process into production lines. Remote laser welding takes the advantages of less mechanical movement and better accessibility of the beam to the workpiece, thus much faster processing speed can be achieved. In most cases, remote laser welding involves lap welding. While the sheet metal components in automotive industry are mostly zinc coated for better corrosion resistance. One typical concern involved in laser lap welding of zinc coated materials is the potential porous weld caused by the zinc vapour. Since zinc has a vaporizing temperature that is lower than the melting point of steel, zinc vapour generated during laser welding will expel the molten metal out of the weld pool, resulting in rough weld. Therefore, laser beam lap welding of zinc coated steel components is not a straightforward process and it requires a special procedure to provide proper venting of the zinc vapour. Although there are several approaches to address this issue, many of the approaches are either impractical or too costly to apply to remote laser beam welding. Currently, the only practical solution for remote laser welding is to maintain a small gap between the joining materials. It has been proved through trials that a gap around 0.15 mm in size is optimum for such welding. The open question remains, however, how to generate such a small gap consistently and effectively at the welding location?