technical know-how
conduction method don’t need additional finishing. The energy enters the weld zone only by heat conduction. This limits the welding depth and thus the process is therefore ideal for joining thin materials. Heat conduction welding is often used for visible weld seams which need to be aesthetically pleasing. • Deep Penetration or Keyhole Welding uses keyhole welding (deep penetration) mode to create deep, narrow welds with uniform structure. For metals, power densities of about one megawatt per square centimetre are applied. This not only melts the metal but vaporises it, creating a narrow vapour-filled cavity. This keyhole cavity is filled with molten metal as the laser beam advances through the workpiece. Keyhole welding is a high-speed process and thus, the distortion and the formation of a heat-affected zone are kept to a minimum. Many laser welding applications are conducted without the need for additional filler material. This is called homogeneous welding . However, some challenging materials and applications require filler material to produce satisfactory welds. Adding filler material improves the weld profile, reduces solidification cracking, gives the weld better mechanical properties, and allows for more precise joint fit-up. • Laser-hybrid welding combines the concepts of electric arc and laser beam. The two simultaneously act in the same welding zone, complimenting each other and creating a unique welding process. Although laser
welding can be used in conjunction with any arc welding process, these are used more commonly.
• MIG augmented welding (often synonymous with laser-hybrid welding)
• TIG augmented welding
• Plasma-arc augmented welding
Cleaning up Lasers can also be used to clean material. Laser cleaning is a non-contact method that removes welding scale, corrosion, stains, metal black, and non-ferrous lubricants from stainless steel. Laser cleaning can be used before and after welding to improve the quality of the weld. Pre-weld laser cleaning can prevent contamination that could interfere with the weld. Post-weld lasers can remove discolouration due to oxidation, which improves the corrosion resistance of stainless steel welds. At this stage, it is not clear if laser cleaning can restore the passivity of laser welded surfaces and it is advised that standard methods of passivation are used on welded areas. Laser cleaning can reach cleaning speeds of 1 to 1.5 meters per minute, which matches common welding speeds. However, laser cleaning can provide a smooth, high quality weld and remove void-free soldering and brazing. Since it does not involve chemicals, it can improve the health and safety of operators. Since the need for wet chemical washing processes is removed, laser cleaning offers lower production space requirements, lower running costs and is still environmentally friendly.
27
Issue 1– 2024
Made with FlippingBook - professional solution for displaying marketing and sales documents online