Product Code: ICAL09_105

Monitoring of Hybrid Laser-Arc Welding of Galvanized Steels in a Gap-Free Lap Joint Configuration
Authors:
Shanglu Yang, Southern Methodist University; Dallas TX USA
Rouzbeh Sarrafi, -; -
Radovan Kovacevic, -; -
Presented at ICALEO 2009

Hybrid laser-arc Welding of galvanized steels in a gap-free lap joint configuration is a complicated welding process, which is involved in many welding parameters such as laser power, welding speed as well as the distance between laser beam and GTAW torch. Furthermore, the dynamic behaviors of the molten pool, which reflect the stability of the welding process, is significantly affected by the dynamic behaviors of highly-pressurized zinc vapor developed at the interface of two metal sheets. It is impossible to directly observe the dynamic behaviors of the molten pool due to the formation of a large amount of plume and plasma as well as the extremely high intensity light during the welding process. In this paper, a high speed camera with the frame rate of 4000 f/ps is applied to real-time monitor the hybrid laser-arc welding process of galvanized steels in a gap-free lap joint configuration. With the help of the illumination light, the fluid flow patterns of the molten pool under various welding conditions are obtained by the high speed camera. Effects of the zinc coating and the gap between two plates on the flow fluid features of the molten pool are investigated. It was found that when the fluid flow is stable, the keyhole is kept open, which provides a chancel for the highly-pressurized zinc vapor to be vented out from the interface of two metal sheets. Consequently, the stable welding process is obtained. However, when the fluid flow of the molten pool becomes turbulent due to the instable highly-pressurized zinc vapor, the stationary fluid flow in the rear part of the molten pool is immediately transformed into the swirling status and spatially progresses forward to close the keyhole. This results in the formation of a large amount of spatters and blowholes in the welds.