In their textbook Modern Welding Technology, Howard B. Carey and S. Helper estimate that as much as 50% of the U.S. GDP relies on welding in one form or another. It is used to manufacture everything from bridges, buildings, and pipelines to cars, computers, and mobile phones. Yet, despite its prevalence, important processes such as laser beam welding (LBW), are still not well understood. This lack of understanding costs many industries time and money. To help remedy this situation, the Physical Measurement Laboratory (PML) and the Material Measurement Laboratory (MML) at the National Institute of Science and Technology (NIST) have teamed up to study the science of laser welding at a new facility in Boulder, Colorado. “The NIST Laser Welding Program is an exciting opportunity to bring the full breadth of NIST metrology to a difficult subject that impacts our daily lives,” says Marla Dowell, Chief of PML’s Applied Physics Division. Dowell is co-leading the program with James Fekete, Chief of Applied Chemicals and Materials Division at MML.
Laser beam welding is a technique used to join multiple pieces of metal through the use of a laser. The laser beam focused on the base material provides the heat needed to create narrow, deep welds at high welding rates. Laser beam welding is more precise and energy efficient than conventional welding, creating smaller, smoother seams on the order of millimeters instead of centimeters. This makes the process ideal for applications such as biomedical devices, batteries, and nuclear containment vessels. A wide array of remote laser beam delivery systems such as fiber optic cables and robotic arms also make laser beam welding perfect for many high-speed, industrial applications. For example, laser beam welding has found many applications in the automotive industry, ranging from the production of transmissions to air conditioners and roof assemblies. One of the reasons for its heavy use in this industry is the process’ ability to join a wide variety of metals and alloys. These include: carbon steel, stainless steel, nickel and iron-based alloys, copper, brass, aluminum, refractory metals, and even dissimilar metals.
Despite all of its advantages, laser beam welding only accounts for a small portion of all the welding processes used in the United States. Part of this may be due to the high cost of laser welding equipment. However, a lack of information may also play a part in the relatively slow adoption of the process. “A better understanding of the process could make it easier for industries to consider investing in laser welding infrastructure,” says PML physicist and laser applications project leader Paul Williams. To that end, Laser Welding Program researchers are using the combined resources of the Physical and Material Measurement Laboratories to measure the effects of complicated phenomena with large practical consequences. For example, tracking and measuring the effects of heat input and gases such as nitrogen, could help companies tune their laser welding systems to produce crack-resistant welds with optimal chemical compositions and properties. “We are applying state-of-the-art metrology to develop a fundamental understanding of the weld process, connecting process parameters to weld quality through advanced materials characterization techniques. The end goal is to develop a predictable welding process, thus avoiding costly, time-consuming destructive measurements after the fact,” said Dower.
Dower is not kidding when she says, “state-of-the-art metrology.” Metrology is the science of measurement, which seems like pretty straightforward stuff. However the complexity of the laser beam welding process has necessitated the development of new measurement tools. “Our team is developing measurement tools to accurately measure all inputs necessary at every stage in the laser welding process. The ability to accurately measure these properties over such large, dynamic time, length, and temperature ranges requires a unique combination of capabilities that only NIST can provide, making this work vital for the welding community”, says Brian Simonds of PML. “Although laser welding has the potential to replace 25 percent of existing welding activities, it is currently only used in about 0.5 percent. Making up that difference and realizing all of the technological, economic and environmental benefits that go along with it will require efforts like the one we are pursuing at NIST. I’m very proud to be part of such a group and happy to be contributing to a research effort that has the potential for making a large, meaningful impact.”
If you are interested in laser welding or other high energy beam processes, check out the online Welding Fundamentals II course offered by AWS Learning. This engaging, multimedia program provides a comprehensive overview of resistance welding, plasma arc welding, electron beam welding, and laser beam welding, cutting, and drilling. Topics include the science, equipment, consumables, process variables, safety precautions, and advantages and disadvantages inherent to each process.