Aluminum laser welding - The process
As with all welding processes, the joining zones of the two components to be joined are locally melted by a targeted heat input, in this case by a diode laser. The melts of the two components flow into each other, cool down and form a solid joint after solidification. Since the individual alloy components of the aluminum solidify at different temperatures, there is a risk of hot cracks due to the shrinkage stresses occurring in the microstructure during cooling. These would significantly reduce the strength of the welded joint. To avoid hot cracks, a filler wire of aluminum silicon (AlSi) is therefore added to optimize aluminum weldability. The weld produced in this way not only has excellent strength, but is also visually appealing and requires no post-processing.
In hot wire welding, electrical current is passed through the filler wire and heats it via Joule heating before the laser completes melting to a liquid state. Liquid metals absorb laser energy at much higher rate. The less laser energy is required to liquefy the filler wire, the more efficient the laser becomes in the process. Put simply, in the hot wire process, the electrical power substitutes laser power that is no longer applied to melt the filler wire. Overall, there are positive effects on the energy footprint and process stability. Significant process advantages are associated with the laser hot-wire process: the heat input and the heat-affected zone are smaller compared to other welding processes, reducing distortion. In addition, higher process speeds can be achieved at high weld grades. The weld seam quality is excellent.
Process advantages of the diode laser in aluminum welding
A major advantage of the process is the quiet melt pool during laser welding of aluminum. The weld seams therefore turn out very uniformly shaped, clean and smooth. Contamination due to unwanted metal splashes on the surface of the workpiece and on the laser optics can be avoided.
Another advantage is the significantly higher energy efficiency of the diode laser compared to other industrial lasers, which makes it attractive for laser welding aluminum in terms of both process technology and economy. Alongside the higher efficiency, yet another factor has a positive impact: Compared to many other industrial lasers, the generally shorter wavelength range of diode lasers is closer to aluminum's absorption maximum. Less laser energy is reflected and less laser power is required to melt the material. Developments in recent years show that energy efficiency and sustainability are becoming a major factor in production in almost all industries. The development of future-oriented technology that produces optimum results with consistently high performance is therefore trend-setting for Laserline.
Last but not least, the Laserline Multi-Spot module can be used to implement almost any spot geometry to suit any specific process requirement, be it splitting the beam into several individual spots, adjusting the spot spacing or distributing the intensity within a spot. With the spot-in-spot configuration, for example, symmetrical and asymmetrical seams can be achieved with a considerably better weld quality than with conventional circular or rectangular spots, and this at high speeds. The spot-in-spot technique is used, among other things, for welding aluminum with filler wire.
In laser brazing, a process somewhat similar to aluminum welding with filler wire, the multi-spot module is used in a so-called triple-spot configuration: Two secondary spots upstream of the main spot remove the coating at the edge of the wire melting area. During the directly subsequent melting process, this contributes to a considerably smoother, controlled welding process. Read more...