Optimization of the weldability of laser additive manufactured aluminum by minimizing the hydrogen content – process related challenges and solutionsWednesday (08.11.2017) 12:40 - 13:00 Part of:
Due to the currently limited machine productivity as well as their size, laser additive manufactured (LAM) components are still very limited in their dimensions. Joining processes are therefore required in order to integrate these LAM components into overall constructions, e.g. a car body, aircraft structure, etc. The laser beam welding is characterized by a narrow and deep seam with a low heat input compared to arc welding processes. It is therefore ideally suited for filigree LAM components. However, investigations of the iLAS already showed a significantly increased pore formation during welding of laser additive manufactured aluminum (AlSi12) compared to the cast material of the same alloy , . The reason for this is a significantly higher hydrogen content of the base material, which is separated in the form of pores in the melt pool during welding due to a solubility drop during solidification and leads to a high weld seam porosity. The increased hydrogen content compared to conventional cast or rolled material is due to multiple influence factors along the process chain from the aluminum raw material, the powder atomization process, the powder processing to the finished LAM components. Non-optimal starting material as well as the high surface of the powder, in combination with the hydrogen affinity of the aluminum material has a negative effect in the various process steps.
In the context of this paper, these influences are shown along the processing chain. Furthermore, measures are examined that reduce the hydrogen content of the powder and the finished LAM component, thus optimizing the welding properties of the material. For this purpose, powder drying tests in the furnace and directly in the LAM machine as well as subsequent heat treatments of the component for hydrogen fusion are analyzed by means of statistical tests. Finally samples correspondingly treated are joined by laser welding and analyzed the impact of the measures on weld seam porosity.
 Emmelmann, C., Beckmann, F.: “Hybrid lightweight design by laser additive manufacturing and laser welding processes”, Lasers in manufacturing, München, 2015.
 Emmelmann, C., Beckmann, F.: “Neue Leichtbaukonzepte für den Fahrzeugbau durch Laserfüge- und 3D-Druckverfahren”, Große Schweißtechnische Tagung, Leipzig, 2016.
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