and cost. With lasers, individual sheets are precision butt welded with no fi ller wire (autogenous welding) and feature a low heat affected zone (HAZ). “Preci- sion is critical, which is what the laser offers,” said Eisenmenger. The steel sheets for the blanks range in thickness from less than 1 mm up to 3-mm thick. The weld itself can be 1-mm wide. “The weld nugget gets harder and stronger, with less ductility and therefore can be a limiting factor in subsequent stamping op- erations,” he said. So the smaller the weld the better.
“Lasers are becoming the welding tool of choice, replacing TIG, brazing, or torch welding.”
Starting with 5-kW CO2 lasers in the early
1990’s, the company migrated to 8-kW lasers about a decade later and is now employing 7–10-kW fi ber lasers. While new welders use fi ber lasers, earlier CO2
lasers remain in production, though the
company expects to phase them out over time with state-of-the-art fi ber lasers. The company designs and integrates their own welding stations. Interestingly, while lasers were a key enabler for the process, they are not a signifi cant part of the cost of each welding station, perhaps 10%. The rest of the cost is in precision guideways,
robotics, and material handling. Eisenmenger notes another advantage of laser welding is it is a process easy to reprogram for new parts. “Five years ago we had about 18 standard parts in production in North America, and we now deliver about 50 different parts,” he said, using the same lines to create a num- ber of different ones. From fi rst introducing welded blanks, TWB devel- oped engineered blanks with curvilinear welds and hot-formed blanks made of manganese-boron steel for strong, crash-critical stampings. The company also pioneered tailor welded coils, introduced in 2011. These are lengths of coil thousands of meters long with butt welds of different gages, steels, and coatings used in progressive dies. Only lasers can maintain precise welds with consistency and speed over such long lengths, according to Eisenmenger. They see aluminum and new high-strength steels replacing some traditional steel applications to lower the weight of vehicles. According to Eisenmenger, alu- minum today is not used in any tailor welded product. His company is investigating various alloys and thick- nesses. The Ford F-150 with its heavy use of aluminum is catching their attention. “We are investigating 5000, 6000, and 7000 series alloys of aluminum,” he said. The company has proven laser welding using only 5000 series alloys and continues to experiment with other grades and welding processes.
Powertrain Too
In addition to BIW applications, companies are also turning to lasers for powertrain components. “We are seeing lasers used in powertrain welding
Hot stamping of manganese and boron steel parts, welded with lasers, delivers higher strength, lower weight, and more complex shapes than cold formed stampings.
Photo courtesy Tailor Welded Blanks LLC LF20
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