LZH Creates Hybrid Welding Method for High Strength Steels

Laser gas metal arc or GMA hybrid welding is ideal for various welding applications, such as bridging big gaps. The problem is that high strength structural steels with fine grains can have cracks as well as incorrect stiffness levels can happen in the seams of the welded portion.

Scientists from the Leibniz Universitat Hannover and Laser Zentrum Hannover have developed a hybrid welding process that can be used for high strength structural steels up to a maximum of 20 mm in thickness. It utilizes inductive preheating.

To improve the quality of the hybrid welding process, the Joining and Cutting Group from the Laser Zentrum Hannover has incorporated inductive preheating to the process. Before the welding process, an induction coil provides energy to the targeted area. This is important in the new method of welding high strength steel.

The steel is preheated to the desired heat level but the heating element doesn’t contact the steel directly. The seams are less fragile and the amounts of fracture strain are better. It allows welders to avoid hot cracks. Steel sheets are welded with a layer. This shortened the welding process and save on material.

The process has been designed to high strength structural steels with yields of 460 to 690 N per square mm. This can be used in bridge, crane, pipeline, and pump construction, as well as in offshore areas. Feed rates of 0.75 m/min to 2.5 m/min can be achieved with the method.

The material and process technicians from the LZH worked with the electrical engineering and civil engineering departments of the LUH. The technicians from LZH worked with the welding processes and simulated with the preheating process. They also evaluated the welding seams.

The project was made possible through the support of German Federation of Industrial Research Associations as well as the Research Association for Steel Application. Thanks to this approach in welding, the constructors managed to achieve new goals in welding. The proper control over preheat and heat input let the welders get the properties that they have never thought about. Besides, the distortion is considered to be the main problem in welding and thanks to the continuous monitoring of dimensions at the time of fabrication, the welders managed to notice that the problem of distortion has disappeared. It is a great chance for welders to demonstrate their professionalism and to move to another stage of the individual and professional progress.

We also need to define that thanks to the progress in metallurgical studies, the welders discovered different ways of using this sort of welding which provides so much strength and makes the future constructions more stable.

Images in this post are form: http://www.lzh.de/en