Product Code: ICAL06_103

The Effect of Welding Parameters on Keyhole Behavior in CO2-Laser Welding
Authors:
Antti Salminen, Lappeenranta University of Technology; Lappeenranta Finland
Anna Fellman, Lappeenranta University of Technology, Laser processing laboratory; Lappeenranta Finland
Presented at ICALEO 2006

The advantages of laser welding are based on the utilization of so called keyhole, which is a vapor channel generated to base material. The energy of laser beam is brought to the material via the keyhole. There are various mathematical models created explaining the shape and behavior of keyhole during welding. However, the validation of the keyhole behavior against the models is lacking. It is commonly accepted idea that the stability of the keyhole plays a major role when considering the ability of the laser welding process to produce high quality welds. This study utilizes a high speed photography system and concentrates on the visual evaluation of the keyhole behavior, stability and effects of welding parameters on them. The materials used were common low alloyed and austenitic stainless steels of thickness 1 - 6 mm and the joint types used were both butt and lap joint. The effects of different airgap, welding speed, laser power and laser beam positioning were tested and their effects on keyhole behavior were observed with a high speed photography system. The welds were evaluated by visual and metallographic examination. It can be seen that the creation of weld faults caused by welding parameter changes can be seen in photographs. The changes in keyhole behavior viewed from top of the process are also visible in the weld cross sections.