"Cold" laser beam improves arc welding. (Mechanical Engineering).

While arc welding has been used for decades to join metal parts on everything from cars to boats to airplanes, the basic technology behind this multibillion-dollar industry has changed little since World War II. Now, though, engineers at Ohio State University, Columbus, have devised a way to improve the precision of arc welding and help manufacturers save energy and equipment costs. Charles Albright, professor of industrial, welding, and systems engineering, and his colleagues found a way to guide the position of welds with a special low-power laser beam. They call the newly patented technique Laser Assisted Arc Welding (LAAW).

Traditional arc welding is hard to control and sometimes damages metal parts. More precise welding is done today with inexpensive multikilowatt lasers in the automobile and aerospace industries. The LAAW system uses just seven watts--little more than a Christmas tree light bulb. Albright thinks that, once the technology is commercialized, a LAAW system could cost one-tenth of what today's typical laser welding systems do.

Since the late 1970s, researchers have known that laser beams could be used to create a path of electrons for arcs to follow, but generating enough electrons to attract a welding arc always required a high-power laser and a high-temperature laser beam path. A one-kilowatt laser, for instance, concentrates the power of a small space heater into a single, submillimeter-size spot. Such lasers are often used to manufacture electronics because they generate enough heat to melt thin metal parts in very small, controlled areas.

The researchers came up with a technique for creating an electron path with much more finesse than brute force. They infused small amounts of carbon monoxide gas into a welding gas, then used a low-power laser at just the right frequency to cause molecules of the gas to vibrate. The laser beam cut a glowing blue trail through the weld chamber as the vibrating carbon monoxide molecules shed their electrons, creating an attractive path for the welding arc to follow at low temperatures. Since very little energy is required in this process, very-low-power lasers can be used. The engineers dubbed this effect "cold ionization" because it charged, or "ionized," the carbon monoxide gas without generating heat.

When the engineers turned on the welding arc, it immediately jumped to the laser beam. First, the engineers aimed the laser at the head of a bolt they'd placed in the weld chamber, then to a sheet of stainless steel. The arc followed the beam each time, creating welds in the metal. "We're hoping that, one day, with a $5,000 power supply and a $20,000 laser, we could do the work of a laser system costing 10 times as much," Albright indicates.