Image of Laser Welding
Inside NIST’s laser welding booth, a high-power laser melts a piece of metal to form the letters “NIST.” (Credit: Paul Williams/NIST)

A better understanding of the interaction between laser and metal could give industry more control over laser welding. Scientists at NIST have been collecting data on the most fundamental aspects of laser welding. The measurements of this complicated process are more accurate and comprehensive than any data ever collected on the subject, the researchers say.

Now, this information is starting to be used by computer modelers to improve simulations of laser welding processes, a necessary step to prepare the work for industry, including medical manufacturing.

If manufacturers want to weld two pieces of an unfamiliar alloy of metal, they might use trial and error to figure out which combination of laser settings will produce the best weld for their application. But most manufacturers would prefer to streamline the research process and move into production as quickly as possible.

That’s where computer models come in. These simulations help manufacturers predict what kinds of welds they can expect with different settings.

To make the models, though, researchers need data from past experiments. And at the moment, that research is spread across hundreds of studies, representing decades of work from dozens of laboratories. The NIST team is attempting to build a much firmer foundation for a model. NIST researchers are measuring everything that a simulator would need — the amount of power that is hitting the metal, the amount of energy the metal is absorbing, the amount of material that is evaporating from the metal as it is heated — all in real time.

Many of the techniques the researchers are using to collect the data were either designed or developed at NIST to measure novel aspects of welding. They also found a way to better measure the weld plume, a cloud of vaporized materials that includes tiny amounts of elements that evaporate out of the sample during welding. To sense these minuscule signals, NIST researchers are adapting a technique called laser-induced fluorescence (LIF) spectroscopy.

Another important aspect of the work is that researchers are conducting all of their experiments with a type of stainless steel that is a NIST standard reference material (SRM), meaning its composition is extremely well known.