Press RELEASE
Reliable joining of high-strength steels using a laser hybrid welding process
Laser-gas metal arc (GMA) hybrid welding is fast, good for deep welding, and can be used to bridge large gaps. However, for thicker high-strength, fine-grain structural steels, hot cracks and undesired hardness levels can occur in the welding seam. For this reason, in an interdisciplinary project scientists at the Laser Zentrum Hannover e.V. (LZH) and the Leibniz Universität Hannover (LUH) have developed a hybrid welding system with inductive preheating. This process can be used for reliable, high-quality, single-layer welding of high-strength, fine-grain structural steels up to a thickness of 20 mm.
In order to increase the weld seam quality for laser-GMA hybrid welding, the Joining and Cutting of Metals Group at the LZH has expanded the process to include integrated, inductive preheating. Directly before the welding process takes place, an induction coil brings energy into a targeted area of the welding seam. Thus, the steel is preheated to the desired temperature, without direct contact. The weld seams are less brittle, fracture strain values are better, and hot cracks can be avoided. With this process, steel sheets can be welded with a single-layer, and time and material can be significantly saved.
Developed for Practical Application
The process was developed for high-strength, fine-grain structural steels with yield strengths from 460 to 690 N/mm². Applications for the used grades S700MC, X70 and S690QL can be found in crane, pump, pipeline and bridge construction, and in offshore areas. With this process, depending on the sheet thickness, feed rates of 0.75 m/min to 2.5 m/min can be reached.
Successful Interdisciplinary
The basis for the project was close cooperation between the material and process technicians from the LZH, and the engineers from the civil engineering and electrical engineering fields at the LUH. While the engineers at the LZH experimented with welding processes, the Institute for Electrotechnology and the Institute for Steel Construction (both LUH) made simulations of the preheating process, respectively the welding process, and evaluated the welding seams.
The project DOVOR – High-performance welding of high-strength, fine-grained steels with high process reliability, using a hybrid welding process with integrated preheating – was financially supported by the German Federation of Industrial Research Associations "Otto von Guericke" e.V. (AiF) and the Research Association for Steel Application (FOSTA).
There are three figures and a video for this press release.
Caption figure 1: High-strength, fine-grain structural steels can be joined without hot cracks using the laser-GMA hybrid welding process developed at the LZH. Photo: LZH
Caption figure 2: Experimental setup of the laser-GMA hybrid welding process with an inductive coil for preheating. Photo: LZH
Caption figure 3: Single layer laser-GMA hybrid welding: Cross-section of a weld seam of 20 mm thick high-strength, fine-grain structural steel of the grade S690QL. Photo: LZH
Caption video 1: Process video of the laser-GMA hybrid welding process: Before it is welded, the metal sheet is preheated using an induction coil. Video: LZH
Laser Zentrum Hannover e.V. (LZH)
As an independent, non-profit research institute, the Laser Zentrum Hannover e.V. (LZH) stands for innovative research, development and consulting. The LZH is supported by the Lower Saxony Ministry for Economics, Labour and Transport and is dedicated to the selfless promotion of applied research in the field of photonics and laser technology. Founded in 1986, over 170 employees are now working for the LZH.
The focus of the LZH lies on the fields of optical components and systems, optical production technologies, and biomedical photonics. Interdisciplinary cooperation between natural scientists and mechanical engineers makes innovative approaches to challenges from the most different areas possible: from the development of components for specific laser systems to process developments for the most diverse laser applications, for example for medical technology or lightweight construction in the automotive sector. Seventeen spin off companies have emerged from the LZH up to now. Thus, the LZH has created a strong transfer between fundamental science, application oriented research, and industry.
Editing:
Dipl.-Biol. Lena Bennefeld | Marketing & Communications | +49 511 2788-238 |
Laser Zentrum Hannover e.V. | Hollerithallee 8 | 30419 Hannover, Germany | +49 511 2788-0 | www.lzh.de