Influence of Magnesium on Spatter Behavior in Laser Deep Penetration Welding of Aluminum Alloys

Felsing Felsing,Woizeschke Woizeschke

doi:10.3390/jmmp3030071

Abstract

The quality of welds, as well as the necessity of post-processing, is challenged by spatter generation during the laser keyhole welding process. In this study, the influence of the magnesium content on spatter behavior is studied for three aluminum alloys (Al99.5, AlMg3, and AlMg5). A synchronized dual high-speed camera system is used to observe the spatter behavior and to reconstruct 3D spatter trajectories as well as determine the characteristics of spatter velocity, flight path angle, and approximate spatter size. The mean spatter velocities and flight path angles of the welding experiments with the three alloys were in welding direction between 4.1 m/s and 4.6 m/s and 44.8° and 51.0°, respectively. Furthermore, the AlMg alloys show excessive spatter behavior with spray events of more than 50 spatters at a time, and less frequently spatter explosions. Spatter spray events show a character similar to spatter explosions. Volumetric evaporation is proposed as effecting these events. In contrast, and resulting from a different mechanism, pure aluminum (Al99.5) shows group ejection events with at least 10 spatters at a time. In this study, there are no correlations between spatter velocities and flight path angles, nor between velocities and approximate spatter sizes.

Highlights

Laser beam welding is a well-established process with increasing use in industrial production lines, such as in the car manufacturing industry
The spatter behavior will be differentiated between spatter explosions and spatter spray events in case of welding of AlMg3 and AlMg5
If a heat source like a laser beam is applied to the spatter, the inner melt layer can quickly reach its boiling point, which will result in a volumetric evaporation

Summary

Introduction

Laser beam welding is a well-established process with increasing use in industrial production lines, such as in the car manufacturing industry. In cases with materials that have a high reflectance, the laser beam energy can be input efficiently by a process type known as keyhole welding or laser deep penetration welding. Laser keyhole welding enables fast material processing, resulting in deep and narrow welds accompanied by high cooling rates. With the ongoing demand for lightweight construction due to the goal of exhaust emission reduction, aluminum alloys make it possible to achieve a significant weight reduction in vehicles (up to 50%), while providing sustainability as 95% of the aluminum can be recycled [1]. The non-heat treatable 5000 series AlMg alloys are popular for their high corrosion resistance in the marine environment, good weldability, and moderate to high strength (~280 MPa) and toughness properties, which can be gained by work hardening [2]

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Conclusion