- Lasers Improve Conventional Welding
HANOVER, Germany, Aug. 11, 2010 — Laser Zentrum Hannover (LZH) recently announced two new laser techniques that are improving conventional welding.
Laser stabilization makes gas metal-arc welding (GMAW) faster and better. On the left, GMAW without laser stabilization; on the right, with laser stabilization.
The first technique is a welding process that is based on gas metal-arc welding (GMAW). According to the company, by adding a laser beam to guide and stabilize the process they can achieve twice the speed.
In conventional GMAW, the electric arc naturally follows the path of least resistance between the electrode and the base material. The arc is difficult to control, and under certain conditions (e.g. welding materials of different thicknesses) good welding seams are almost impossible. When the laser beam is "added" to the gas metal-arc welding process, the arc follows the laser beam path and is stabilized. Not only is the quality of the welding seam greatly improved, but welding speeds can be increased up to 100 percent for the same welding depth. Furthermore, oscillating seams or seams with a complex geometry are easy when using laser beam stabilization.
The new welding process can be used for conventional steels as well as for high and higher strength steels, or for aluminum materials.
Since the laser used for this welding method has a relatively low output power (200 to 400 watts), investment cost are also kept at a minimum, making this process especially attractive for small and middle-sized welding companies.
The laser-stabilized GMA-welding process is a result of the "FÜLAS" project, which was funded by the German Federal Ministry of Education and Research and supported by the Project Management Agency Karlsruhe.
The second technique, which is a collaboration between LZH and the Institute of Electrotechnology (ETP) at Leibniz University at Hannover, is a process that inductively hardens and welds multi-piece construction elements of heat-treatable steels in one step.
Schematic structure of the combined processing head for the laser hot welding of heat-treatable steels.
Heat-treatable steels are often used for highly stressed construction elements, since they show a high tensile and endurance strength resulting from the heat treatment. In order to weld heat-treatable steels, they must pass through a complex multi-step process. This enables a flawless and stress-resistant weld between both construction elements.
LZH and ETP developed a process which combines inductive hardening and laser beam welding of multi-part construction elements in one process step. The construction elements are heated to a temperature of over 900 °C, the parts are laser welded and then quenched.
The so called “hot welding” immediately reduces tensions occurring during the welding process, so that the danger of cold cracks in the welding seam and a softening of the basic material are avoided. In order to achieve this, a processing head has been conceived and constructed, which combines inductive heating, the welding process and quench hardening in one step. The processing head consists of a laser processing head, an inductor, a quench shower and a shielding gas nozzle.
Laser hot welding of heat-treatable steels.
In comparison to construction elements which have not been preheated, the processing head used increased the welding depth by 25 percent. The welding seams and the heat-affected zone show a homogenous hardness distribution. Also, martensitic structures were detected in both areas.
After the welding/hardening process has been complete, it is also possible to harden the surface of the construction material using the inductor.
The hot welding process significantly shortens the processing time for heat-treatable steels, and simplifies the process run. In addition, the process simulation developed in the project can be used for an exact calculation of the process.
This research project was funded by the Stiftung Stahlanwendungsforschung, Essen, and coordinated by the Forschungsvereinigung Stahlanwendung e.V., Düsseldorf.
For more information, visit: www.lzh.de
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