Laser beam welding
Laser beam welding allows the energy used to be precisely focussed. This makes it possible to achieve a very high welding speed. The shape of the weld seam is also very narrow and slim. This results in very little thermal distortion for the workpiece. Laser welding usually does not require any special filler material.
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Laser welding - process explained
As the name "laser beam welding" or "laser welding" suggests, light is used in this process. This is focussed on the surface of the joint edge. The laser's optics are located close to the surface and its alignment determines the welding depth, among other things.
The focal spot formed by the laser has a diameter of just a few tenths of a millimetre. With an output of several kilowatts for the laser, this results in very high energy concentrations. The surface of the workpiece absorbs this energy quickly, which results in a very rapid rise in temperature. This means that the melting temperature is exceeded in a very short time. Conversely, the seam also cools down much faster due to its very narrow design. As a result, it becomes very hard.
The very concentrated energy flow has two consequences. Firstly, less energy is required and secondly, the thermal distortion in the workpieces is low. This welding process is therefore particularly advantageous when used to attach components to prefabricated parts.
The laser welding system has a leger, a CNC-controlled unit for moving the laser, an optical system that guides the laser beam, an optical system for focussing and processing, and a device that holds the workpieces. Either the laser beam is guided over the workpiece to be welded or the workpiece is moved under the laser beam. However, there are also systems in which both the laser and the workpiece are moved against each other.
Areas of laser beam welding
Laser welding can be divided into several areas. These are laser deep penetration welding, heat conduction welding and laser remote welding. These differ mainly in terms of the beam intensity used for the laser.
Deep laser welding
If a very high beam intensity with a high focus is used, a cavity forms within the molten bath, a capillary filled with metal vapour. With the movement of the laser, this becomes a tube that is located in the depth of the workpiece. This allows the material to be melted quickly even in these deeper regions. The cavity increases the absorption of energy from the laser beam, which increases the volume of the melt pool.
Heat conduction welding
With other beam intensities, however, no cavity is created. It should also be noted that, depending on the wavelength, the metal has a reflectivity of up to 95% for the laser. This reduces the penetration depth of the energy so that sheets with a smaller thickness can also be welded on.
Remote laser welding
Scanners are used in more modern laser welding systems. These consist of rotating bevelled mirrors or deflection mirrors that can be aligned. The mirrors can then be used to move the laser beams over the surface of the workpiece. Thanks to the low mass of such a mirror, the laser beam can be correctly aligned at a very high speed.
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