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As an approach towards more rough industrial laser welding applications, the Nd:YAG laser welding process has been coupled to the plasma powder welding process for the first time. Process stabilities have been achieved by such hybrid welding which are even better than those known from previous coupling of the laser process with gas metal arc welding (GMAW), for instance.
The present contribution focuses on the technology and potentials of the novel laser hybrid welding technique and addresses the realisation and the perspectives for practical applications. The experimental results demonstrate that the new process coupling enables welding of austenitic stainless steels in the thickness range between 3 mm and 8 mm at various weld geometries and joint configurations and at welding speeds exceeding 2 m/min. In addition it has been proven that the laser plasma powder arc welding (LPPAW) technique can also be applied to out-of-position conditions. Continuous advancement of the welding equipment ensures a high gap bridging ability and levelling of misalignment due to higher powder feeding rates. The recent development of a new plasma powder torch even provides a higher efficiency of powder feeding and guarantees smoth weld surfaces. Up to the present, the investigations demonstrated that the novel laser plasma powder hybrid welding technique offers all perspectives for application in pipe fabrication, ship building and offshore as well as transportation industry.
Up to the present, the thermomechanical loads during welding and subsequent cooling under design-specific shrinkage restraint resulting from the interaction between the materials and the structure have often not been taken into consideration approperiately for weldability assessment of components. As compared to previous investigations using small specimens this report presents component weld tests under varying intensities of restraint. Online records of the reaction forces and moments demonstrate in which way the intensity of restraint affects the reaction stresses and moments and their meaning for the evaluation of the load level in welded components.
Düring the past decades, weldability studies have predominantly been concentrated on the material and the welding process. In order to achieve a closer insight into the structural effects, component weldability tests have been performed by online monitoring of the reaction forces and moments. As a particular item, the effects of different strengths of the base and filier material on the reaction force and stress build up transverse to the welding direction have been studied at a specific structural restraint. As a most relevant result for practical welding it is demonstrated that the final reaction force and also the reaction stress level in the multilayer butt welds decreases with overmatch of the weld metal.
Die hier vorgestellte Großanlage zur Prüfung und Simulation von Bauteil schweißungen (GAPSI 16) mit einer Maximalprüfkraft von ±16 MN erlaubt wirklichkeitsnahe Analysen des Bau teilverhaltens während des Schwei ßens. Ein fundamentaler Vorteil ge genüber konventionellen Universal prüfmaschinen ist, Momente während des Schweißens mittels acht unabhän giger Hydraulikzylinder in zwei Prüf tischen aufbringen bzw. registrieren zu können.
Derzeitige Forschungsvorhaben sind zum einen Spannungs- und Verformungsvorgängen während des Schweißens von Blechen und zum anderen Modellen gewidmet, womit Kenngrößen für Flammrichtarbeiten ermittelt werden können. Simulations versuche an Großproben tragen we sentlich zu höherer Aussagesicherheit bei, zumal konventionelle Prüfmetho den mit einfachen Kleinproben und auch Berechnungen nach der Finite Elemente-Methode (FEM) stets Rand bedingungen und zumeist größere Idealisierungen enthalten. Dagegen weist die Großprüfanlage GAPSI 16 mit angepaßten Probengeometrien und Spannkräften einen neuen Weg.