Fachbeitrag von Frau Dr. Jerems
Do you still weld with the electron beam or already with the laser?
Das weltweit erste und einzige Hochvakuum-Laserschweißgerät von KTW Systems
Für besonders sensitive Anwendungen muss der Schweißprozess im Hochvakuum stattfinden. Gründe dafür sind die Einlagerung von Fremdpartikeln und reaktiven Gasen, was zu Versprödungen in der Schweißnaht führen kann. In solchen Fällen ist das Elektronenschweißen das Verfahren der Wahl – allerdings sehr aufwendig und kostspielig im Einsatz. Mit dem Vakuum-Laser-System des Start-Up-Unternehmens KTW Systems GmbH aus dem rheinland-pfälzischen Wehr können diese Nähte zukünftig auch mit dem Laser verschweißt werden. Unabhängig vom Lasertyp, zu deutlich reduzierten Kosten und mit gleichwertigen Schweißergebnissen.
Decoupling of laser and vacuum
The core idea of this patented laser welding system is the decoupling of the vacuum chamber and the laser beam source. The components to be welded are positioned in the vacuum chamber and the space is pumped down to 5 multiplied 10 to the power-5 mbar in around ten minutes - this corresponds to a high vacuum. The laser beam is focused on the welding spot through a quartz or sapphire glass pane. The choice of the laser beam source is completely free. For the maximum of six laser heads, an individual number of openings can be made through which the laser beam can penetrate the vacuum chamber. In addition, there is a freely selectable number of openings for observing the welding process.
The vacuum chamber
The heart of the vacuum chamber is the clamping device that holds the component(s). The clamping technology is designed in such a way that it has no hollow chambers in which air pockets can be found. They are purely mechanical so as not to have any other feeds to the outside that would need to be sealed.
The size of the vacuum chamber is almost freely scalable and can be adapted to the respective applications - as small as possible and as large as necessary. Because optimising the volume of the vacuum chamber reduces pumping time and increases productivity.
The laser weld seam
A laser weld created in a high vacuum has the same appearance as an electron weld: it is characterised by an extreme height-to-width ratio. In the vacuum, there are no particles that could deflect the laser beam. The focal length of the optics is constant, the focusing on the welding spot is done by means of a relative movement of the component to the focal point.
This advantage is particularly evident when welding gas-sensitive materials such as titanium, zirconium, molybdenum, tantalum, tungsten, vanadium, nickel or niobium. Without the ambient air, a shielding gas atmosphere is also obsolete. The weld seams produced do not have any porosities.
Advantages compared to electron beam welding
In addition to the significantly lower investment costs of a laser beam source compared to an electron beam source, high-vacuum laser welding has other process advantages over electron beam welding. Since the electron beam involves highly accelerated electrical charge carriers, X-rays can be emitted when the electron beam collides with the material to be welded, which must be shielded at great expense. Direct observation of the welding process is therefore not possible. Furthermore, the electrical charge carriers can be sensitively influenced by magnetic fields. If there is even a small current flow, this can have a negative influence on the welding process and lead to rejects in production.
The laser beam, on the other hand, transports its energy in the form of light. Neither X-rays are produced nor are there any deflection phenomena due to magnetic and/or electric fields. Theoretically, laser high-vacuum welding could even be used to reliably weld current-carrying components with a statistically changing current flow.
The areas of application
Laser high-vacuum welding covers the same areas of application as electron beam welding - and beyond. Material thicknesses are up to 20 mm - regardless of the material to be welded and the material pairings. Typical applications can be found in the automotive and railway construction sectors as well as in aerospace, the electronics industry or medical technology, in innovative industries such as wind energy or in sensitive applications in defence, petrochemicals or power plant construction.
Autor: Dr. Jerems, chilirot
