Laser welding was one of the earliest applications of industrial laser material processing. In most early applications, lasers produced higher quality welds, resulting in increased productivity. As the class of lasers has evolved, laser sources are now available with higher power, different wavelengths and a wider range of pulse capabilities. In addition to this, beam delivery, machine control hardware and software, and process sensors, have all contributed to new and better developments in the laser welding process.
Laser welding offers unique advantages, including low heat input, narrow fusion and heat-affected zones, and excellent mechanical properties of materials that were previously difficult to weld using processes that would generate large heat input into the part. These properties result in stronger and more cosmetically attractive welds formed by laser welding. In addition, laser welding requires much less setup time and, with the addition of laser tracking sensors, can be automated, resulting in lower product costs. All of these new technologies further expand the range of applications for laser welding. Fiber laser welding using different metals, part shapes, sizes and volumes has been successfully applied in many industries.
Battery welding
Laser welding of aluminum alloys (usually 3000 series) and pure copper to form electrical contacts with the positive and negative terminals of a battery. All materials and material combinations used in batteries are candidates for the new fiber laser welding process. Overlapping, butt and fillet welded joints allow for a variety of connections within the battery. The laser welding of the lug material to the negative and positive electrodes creates electrical contact in the pack. The final battery pack assembly welding step, sealing the seams of the aluminum cans, creates a barrier for the internal electrolyte.
Since batteries are expected to work reliably for 10 years or more, laser welding is chosen for its consistently high quality. Using the right fiber laser welding equipment and process, laser welding consistently produces high quality welds on 3000 series aluminum alloys.
Precision Process Welding
Seals used in ships and chemical refineries as well as the pharmaceutical industry were originally TIG welded. Because they are used in sensitive environments, these components are precision machined and ground from high-temperature resistant and chemically resistant nickel-based alloy materials. Lot sizes are usually small and set-up quantities are large. It is understood that the assembly of these components has now been improved using fiber laser welding.
Reasons for replacing the earlier robotic arc welding process with fiber laser welding include: consistent laser weld quality; ease of changeover from one component configuration to another, which reduces setup time and improves throughput; and cost reductions by automating the laser welding process through the assembly of laser tracking sensors.
Gas-tight welding
Hermetically sealed electronics in medical devices such as pacemakers and other electronics have made fiber laser welding the process of choice for applications requiring the highest level of reliability. Recent advances in hermetic welding processes have addressed issues related to laser welding and the end point of the weld, which is a critical location for accomplishing hermetic seals.
Prior laser welding techniques produced depressions at the end point when the laser beam was turned off, even at reduced laser power. Advanced laser beam control eliminates dimpling in both thin and deep welds. The result is consistent weld quality with no porosity at the end point and an improved appearance and more reliable seal.
Dissimilar Metal Welding
The ability to fabricate products using dissimilar metals and alloys greatly increases design and production flexibility. Optimizing the properties of the finished product, such as corrosion, wear and heat resistance, while controlling costs, is a common motivation for performing dissimilar metal welding. Joining stainless steel and galvanized steel is an example. Due to their excellent corrosion resistance, 304 stainless steel and galvanized carbon steel have been used in a wide variety of applications, such as kitchen utensils and aerospace components. The process presents some special challenges, not least because the zinc coating can present serious weld porosity problems.
The energy used to melt the steel and stainless steel during the welding process evaporates the zinc at approximately 900 degrees Celsius, which is significantly below the melting point of stainless steel. The low boiling point of zinc results in the formation of vapors during lock-hole welding. In attempting to escape the molten metal, zinc vapors may be trapped in the solidified weld, resulting in excessive weld porosity. In some cases, zinc vapors can escape as the metal solidifies, creating porosity or roughness on the weld surface.
With proper joint design and selection of laser process parameters, finishing and mechanical welding can be easily performed. Lap welds of 304 stainless steel with a thickness of 0.6 mm and galvanized steel with a thickness of 0.5 mm were free of cracks or porosity on both the upper and lower surfaces.
