In a nutshell:
ROSEN Factory in Lingen now TÜV-certified for titanium welding processes
Certified employee welds titanium assemblies in mobile forming chamber
Process is required to manufacture frames for ROSEN AUV
The ROSEN Group in Lingen can now weld titanium in its manufacturing. It has developed a TÜV-certified process for welding assemblies in a mobile forming chamber. This is a process that does not exist very often in (northern) Germany. Sometimes, it was a long way to go.
The most annoying thing right at the beginning: somehow getting your hands into these gloves. "Not as easy as it looks," says Leo and tries again. The welder stands in front of an inflatable forming chamber and fights his way in, finger by finger. Then it's time to get started. Inert gas atmosphere checked, warning alarms switched on, welding tool and components in formation, action. But why all this effort? "For a few weeks now, Leo has been our first employee to be certified for titanium welding," says his supervisor Jan. "And for titanium welding, we need very special conditions under which we can weld the material."
For example, an airtight area is needed in which there is pure argon and virtually no oxygen. Normally, entire rooms are placed under a vacuum atmosphere and then flooded with pure argon 5.0. Welders work in this area under respiratory protection. The so-called forming gas ensures that titanium components can be welded. However, since the employees do not have to weld titanium assemblies daily, a separate area would be somewhat oversized. So, a mobile solution was needed. "We had to do some searching and finally found what we were looking for in the USA," says Jan. "Here we tracked down a supplier who was able to supply us with a mobile forming chamber in which we can weld components up to a size of 280 x 120 x 130 centimeters."
Titanium welding. Why actually?
The size is relevant because the titanium assemblies are needed for the ROSEN AUV. The company has been developing its own Autonomous Underwater Vehicle (AUV) for several years. "Titanium is very light and at the same time extremely strong. In the AUV project, we want to build a lightweight and relatively small vehicle to be able to drive in an energy-efficient way. For this reason, we designed the main frame of the AUV from titanium," says Matthias Piepel from the AUV-Team. In addition, titanium has the property of not rusting even when in contact with salt water.
In designing the AUV frame, the team used welding techniques commonly used in the production of transport frames. Basically, it is a push-fit system that is spot-welded with fillet welds. "One challenge with welding is making sure the material doesn't get too hot and warp," Leo explains. "We had to trial and error for about two weeks before we had an idea of how to make it work."
By "we," he means himself and Norbert (Quality Assurance Technician). The two refined the conventional TIG (tungsten inert gas) welding process until the right framework for titanium welding was found. "I did push Leo quite a bit here and there, and sometimes we had to take a break," Norbert looks back. But the ideas finally came, says Leo, "The topic didn't let us go, and we continued to tinker with it over the weekend." Heat dissipation, in particular, was a major concern for the two. After they borrowed a finned cooler and thermal paste from other departments of the Lingen site for the test phase, the breakthrough came. In cooperation with the TÜV (technical testing organization that performs safety inspections), they were then able to successfully complete the trial phase and process testing.
TÜV certified
At the end of the process, which lasted several weeks, the process was TÜV-certified. Leo is now the first certified welder for titanium at ROSEN. Another employee is to follow later this year. Leo has welded the first frame for the AUV. By summer at the latest, the mobile forming chamber will then be flooded with argon again to produce another frame. "ROSEN is now one of the few companies in northern Germany that is even TÜV-certified to weld titanium. We are very proud of this and are pleased to have such qualified employees as Leo," Jan concludes.