Laser welding is one of the earliest applications in industrial laser material processing. In most early applications, laser generated welds are of higher quality, resulting in increased productivity. With the development of laser types, laser sources now have higher power, different wavelengths and wider pulse capability range. In addition, beam propagation, machine control hardware and software, and process sensors all promote the better new development of laser welding process.
Laser welding has unique advantages, including low heat input, narrow fusion zone and heat affected zone, as well as the excellent mechanical properties of materials previously difficult to use processes that produce large heat input to parts. These properties make the weld formed by laser welding stronger and more attractive in appearance. In addition, the setting time required for laser welding is much less. Coupled with the laser tracking sensor, automation can be realized, thus reducing the product cost. All these new technologies have further expanded the application range of laser welding. In many industries, fiber laser welding using different metals, component shapes, sizes and volumes has been successfully applied.
Battery welding
The increasing use of lithium batteries in electric vehicles and many electronic devices means that engineers use fiber laser welding in product design. The current carrying components generated by copper or aluminum alloy are connected to a series of batteries in the battery by optical fiber laser welding. Laser welding aluminum alloy (usually 3000 Series) and pure copper to form electrical contact with the positive and negative electrodes of the battery. All materials and material combinations used in the battery are candidate materials for the new fiber laser welding process. Overlapping, butt and fillet welded joints make various connections inside the battery. Laser welding of the lug material to the negative and positive terminals will produce packaged electrical contact. The final battery pack assembly and welding step, that is, the joint sealing of the aluminum can, creates a barrier for the internal electrolyte. Since the battery is expected to work reliably for 10 years or more, the selection of laser welding can always have high quality. Using correct optical fiber laser welding equipment and process, laser welding can consistently produce high-quality welds of 3000 series aluminum alloy.
Precision machining and welding
Seals used in ships, chemical refineries and the pharmaceutical industry were initially TIG welded. Because they are used in sensitive environments, these components are precision machined and ground by nickel base alloy materials that are resistant to high temperature and chemical corrosion. The batch size is usually small and the number of settings is large. It is understood that at present, the assembly of these components has been improved by optical fiber laser welding. The reasons for using fiber laser welding to replace the early robotic arc welding process include: the quality of laser welding is consistent; It is easy to convert from one component configuration to another, which reduces the setting time and improves the output; The cost can be reduced by assembling the laser tracking sensor to automate the laser welding process.
Gas tight welding
Hermetically sealed electronics in medical devices such as pacemakers and other electronics have made fiber laser welding the preferred process for applications requiring the highest reliability. The latest development of gas tight welding process has solved the problems related to laser welding and weld end point, which is the key position to complete gas tight sealing. The previous laser welding technology will produce a depression at the end point when the laser beam is turned off, even when the laser power is reduced. Advanced laser beam control eliminates depressions in thin and deep welds. The result is consistent weld quality, no porosity at the end point, improved appearance and more reliable sealing.
Aerospace welding
Fiber laser welding of nickel and titanium based aviation alloys requires controlling weld geometry and weld microstructure, including minimizing porosity and controlling grain size. In many aerospace applications, the fatigue performance of welds is the key design criterion. Therefore, design engineers almost always specify that the welding surface is convex or slightly convex to enhance the welding strength. For this purpose, a filling line with a diameter of 1.2 mm is used for the automated process. The addition of filler wire to the butt joint will result in consistent crowns on the top and bottom passes. By ensuring the good microstructure of the weld, the selection of welding wire alloy also contributes to the mechanical properties of the weld.
Dissimilar metal welding
The ability to manufacture products using different metals and alloys greatly improves the flexibility of design and production. Optimizing the properties of finished products, such as corrosion, wear and heat resistance, while controlling costs, is a common motivation for dissimilar metal welding. Connecting stainless steel and galvanized steel is an example. Due to their excellent corrosion resistance, 304 stainless steel and galvanized carbon steel have been widely used in various applications, such as kitchen appliances and aviation components. This process presents some special challenges, especially because zinc coating will bring serious weld porosity problems. During welding, the energy to melt steel and stainless steel will evaporate zinc at about 900 ℃, which is much lower than the melting point of stainless steel. The low boiling point of zinc leads to the formation of steam during keyhole welding. When trying to escape molten metal, zinc vapor may remain in the solidified weld, resulting in excessive porosity of the weld. In some cases, zinc vapor will escape with the solidification of the metal, forming pores or roughness on the welding surface. Finishing and mechanical welding can be easily carried out through appropriate joint design and selection of laser process parameters. There are no cracks or pores on the upper and lower surfaces of the lap welds of 304 stainless steel with a thickness of 0.6mm and galvanized steel with a thickness of 0.5mm.
