Welding

In the past decade laser welding has exhibited a great expansion with numerous industrial applications, which today still continue to increase. Future prospects for the growth of laser welding are very encouraging; as they are based on the fact that laser is not solely an alternative to other welding technologies, but is a technology that offers new opportunities to optimize production cycles and even product designs themselves, which are not even fully exploited today. There are mainly two mechanisms to achieve welding with a laser beam, which are conduction (melting) welding and deep penetration (evaporation or keyhole) welding. The latter is the typical mechanism of the welding technologies where high power density energy sources are utilized. Amongst these technologies, laser is the most flexible and is the most suitable to adapt to industrial applications.

The common advantages of the two laser welding mechanisms (conduction and deep penetration) are mainly as the following:

- Possibility of welding with proximity heads or remote systems with high focal lengths and scanner heads.

- High productivity: obtainable welding speeds with laser technology are by far superior to those obtainable with conventional welding technologies.

- Limited thermal distortions: the limited thermal input to the weld bead ensures extremely reduced amount of thermal distortion. Thus, this unique characteristic of the laser process permits welding to be the final process in the production cycle, as the need for further processes to reach dimensional requirements is eliminated. Furthermore, it is possible to apply proximity welding to thermally sensitive materials such as plastics, rubber, wood, etc.

- Absence of filling material: laser welding can be applied without the need of filler materials, which evidently simplifies the process.

- Facilitated access: laser beam, without the necessity of any proximity element (i.e. an electrode) allows access to relatively confined zones, which are not reachable with conventional technologies.

- Possibility of obtaining esthetic welds: weld beads obtained with laser present esthetic characteristics, which render them suitable to apply painting immediately, without the necessity of any surface finish. In many cases, the esthetic characteristics of the bead allow welding to be the final process in the production chain, even for components that are characterized by strict esthetic requirements such as furniture, home appliances, etc. Furthermore, the specific advantages of deep penetration welding can be summarized as:

- High aspect ratio that can reach up to 10:1. This permits obtaining highly penetrating weld bead, thus enables applying lap-joint welding

- High repeatability: for its nature, the key-hole generation mechanism is repeatable. Consequently, the weld characteristics are constant, both in terms of dimensions and microstructures, and are affected very little by external factors such as surface preparation etc.

- High bead quality: thanks to the generation of keyhole, in the weld bead a whirling motion is generated, which consents a better homogenization of the chemical composition in the molten bath.

 

 

 
 
SITEC - Laboratorio per le Applicazioni Laser
Dipartimento di Meccanica
POLITECNICO DI MILANO
Via G. La Masa 1
20156 Milano

Mail: segreteria.tecnologie@mecc.polimi.it