The use of lasers for welding has some distinct advantages over other welding techniques. Many of these advantages are related to the fact that with laser welding a 'keyhole' can be created. This keyhole allows heat input not just at the top surface, but through the thickness of the material(s). The main advantages of this are detailed below:
Speed and flexibility
Laser welding is a very fast technique. Depending on the type and power of laser used, thin section materials can be welded at speeds of many metres a minute. Lasers are, therefore, extremely suited to working in high productivity automated environments. For thicker sections, productivity gains can also be made as the laser keyhole welding process can complete a joint in a single pass which would otherwise require multiple passes with other techniques. Laser welding is nearly always carried out as an automated process, with the optical fibre delivered beams from Nd:YAG, diode, fibre and disk lasers in particular being easily remotely manipulated using multi-axis robotic delivery systems, resulting in a geometrically flexible manufacturing process.
Deep, narrow welds
Laser welding allows welds to be made with a high aspect ratio (large depth to narrow width). Laser welding, therefore, is feasible for joint configurations that are unsuitable for many other (conduction limited) welding techniques, such as stake welding through lap joints. This allows smaller flanges to be used compared with parts made using resistance spot welding.
Low distortion and low heat input
Lasers produce a highly concentrated heat source, capable of creating a keyhole. Consequently, laser welding produces a small volume of weld metal, and transmits only a limited amount of heat into the surrounding material, and consequently samples distort less than those welded with many other processes. Another advantage resulting from this low heat input is the narrow width of the heat affected zones either side of the weld, resulting in less thermal damage and loss of properties in the parent material adjacent to the weld.
Suitable for a range materials and thicknesses
With lasers, many different materials can be welded or joined, both metallic and non-metallic, and including steels, stainless steels, Al, Ti and Ni alloys, plastics and textiles. Furthermore, taking the example of steels, the thickness of the material that can be welded can be anything from under a millimetre to around 30mm , depending on the type and power of laser used.
Performed out of vacuum
Unlike the majority of electron beam keyhole welding operations, laser welding is carried out at atmospheric pressure, although gas shielding is often necessary, to prevent oxidation of the welds.
Non-contact, single-sided process
Laser welding does not apply any force to the workpieces being joined, and more often or not is a single sided process, ie completing the joint from one side of the workpieces. However, in common with many other fusion processes, weld root shielding can be required from the opposite side.
Using lasers, spot or stitch welds, if fit for purpose, can be made just as easily as continuous welds.
Apart from welding, with a few adjustments, a laser source can be used for many other materials processing applications, including cutting, surfacing, heat treatment and marking, and also for more complex techniques such as rapid prototyping. Furthermore, the way in which the beam(s) is/are delivered to the workpieces can be approached in a number of different ways, including:
- Time-sharing of a single beam between different welding stations, allowing one laser source to process multiple jobs.
- Energy-sharing a single beam, allowing one laser source to process two different areas (or the same area from opposite sides) on a workpiece.
- Beam shaping or splitting using special transmission or focusing optics, allowing processing of materials with beams of different energy distributions.
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