Surface deposits in laser brazing

Laser brazing is a joining technology which is typically employed in areas with particularly high quality requirements, e.g. to create zero gap roof joints in automotive production. These seams have to be leak proof and are situated in an area of the car body which is in direct view of the customer. Hence, seam defects and imperfections are inacceptable and require extensive rework whenever they occur. Resulting high rework costs can be avoided by investigating the causes of these imperfections in order to prevent their formation. One type of imperfection which may occur during the laser brazing of galvanised steel are dark deposits on the seam surface. This paper examines the mechanisms leading to the formation of this type of imperfection. Results on the properties of surface deposits are presented along with conclusions regarding the systematic reasons behind their formation. Finally, strategies for preventing the occurrence of surface deposits are recommended.