Laser Beam Welding (LBW) is a high energy welding process that continues to expand into modern industries and new applications because of its many advantages. Some of the advantages of laser welding versus arc-welding are:
- High power density: deep weld penetration with minimal Heat Affected Zone (HAZ)
- Automation: easily automated using robotic machinery or CNC
- Accessibility: non-contact nature allows normally inaccessible areas to be welded along a “line of sight” or through thin parts as in the case of a cover plate (see Laser Welding page on our Website for more info)
- Versatility: capable of welding steels, aluminum, titanium, kovar, precious and refractory metals
- “Laser brazing”: high degree of accuracy allows melting of a filler metal placed within a joint without affecting the base material
- Laser welders can also be used for precision cutting and engraving
From a furnace brazing standpoint, laser welding is an important process used to reduce cost and increase productivity. When brazing complex, miniscule, and/or precision assemblies, fixturing quickly becomes the weak link in the process. To compensate for overly complex fixturing, processes are usually modified to incorporate “step brazing”, which still may require some form of fixturing to accompany the part into the furnace. Additionally, if fixturing is necessary to maintain precise location of components, the tooling cost can be even higher. If components can be pre-assembled and precision joined using laser welding such that step brazing is no longer necessary, a great deal of cost can be avoided. One important aspect to remember is that the relative spacing of welded parts does not change during a braze cycle. This can be good or bad depending on the application. This phenomenon must be understood before selecting laser welding instead of using braze fixtures or changing the configuration of the components to be self fixturing/self-aligning.
Another benefit of laser welding is that the non-contact nature of the process makes it easy to produce consistent welds with metallurgical quality. In preparation for brazing, laser welding is a very clean process that, with the proper shielding gas, can produce oxidation free welds. For hermetic braze joints needing pre-welding, laser welding allows parts to go from welder to furnace without needing a post-weld cleaning operation.
One of the most important aspects of laser welding in preparation for brazing is the lack of distortion as a result of the weld. Because of the miniscule HAZ, welded joints see little to no local distortion. Thus, precision joints can retain their tight clearances, which is essential for capillary action during braze.
For small or complex, low or high volume brazed assemblies, laser welding is one option that should be considered to reduce assembly and/or fixturing complexity and cost without affecting braze quality.