Laser beam welding in vacuum

The idea: Uniting the best of both worlds

In order to further improve the results of laser beam welding, our research partner ISF combined the two know-how fields of laser beam welding and electron beam welding. In the joining laboratory, a highly brilliant single-mode laser source was integrated into an existing electron beam welding system.

From the idea to deployment

Some obstacles had to be overcome in the first tests until the process was ready for use: Which is the best way to couple the laser beam into the vacuum? How can we reliably protect the optics in the vacuum chamber from metal vapour?

Together with the ISF and our industrial partners, we successfully mastered the challenges. We developed our own vacuum chamber and also detailed solutions for the optics and their protection. After many intensive tests and precision work, the process is now ready for industrial use.

Laser with extended range of application

The reward for the effort is a welding process that clearly shifts the previous limits of laser beam welding. While unalloyed steels can be joined without vacuum using a high-performance laser up to a welding depth of approx. 15 mm, a 16 kW solid-state laser in a vacuum achieves a welding depth of more than 60 mm. One-sided joints on sheets with a thickness of up to 50 mm can be welded in a vacuum with free weld seam forming and root formation.

Moreover, the vacuum promotes degasification. Pore formation, for example, is reduced to a level that can no longer be detected. The risk of hot cracks is also minimized in a vacuum. The welding seams are as narrow as in electron beam welding.

In a vacuum, spatter is significantly reduced. In addition, oxygen affine materials such as titanium or tungsten can be welded without shielding gas. Due to the comparatively low requirements for vacuum technology, the costs for the vacuum are usually not higher than the shielding gas costs of conventional laser processes.

More flexible than electron beams

Also in comparison to electron beam welding, laser beam welding in a vacuum has its advantages. Since a significantly lower negative pressure is sufficient, the flexibility is noticeably increased. Even the application of small, mobile vacuum chambers is possible. These are limited locally to the weld and can be sealed more easily, because smaller leaks can be tolerated.

There are, moreover, clear advantages in welding preparation and clamping technology. Since laser radiation is not affected by magnetic deflection, the time-consuming demagnetization of large components in particular is no longer necessary. This means that magnetic clamping devices and inductive preheating devices can be used.

Furthermore, no X-rays are emitted when lasers are used. The complex shielding of the process with lead as used in electron beam welding can therefore be dispensed with. The required protection against laser radiation is usually already guaranteed by the vacuum chamber.

Of course, laser beam welding is not superior to electron beam welding in all aspects, even in a vacuum. Not until we have carried out systematic and objective analyses of the intended use for your specific application, will we select the most suitable process for you.