Laser wire buildup welding
This technology describes the continuous buildup welding of thin rod-shaped materials (especially thin wires) onto a substrate using laterally coupled laser radiation. The wire is positioned in relation to the substrate material in such a way that both meet at an sharp angle. In this contact area, both materials are illuminated with a pre-shaped, focused and pulsed laser beam melting the thin wires only partially.
Current processes for laser wire buildup welding require a lot of energy, since the entire wire cross-section is melted completely as well as parts of the substrate. The achievable buildup widths are accordingly larger than the diameter or width of the wire material. The creation of a weld pool on the substrate material together with the complete melting of the wire results in the applied weld tracks having a greater width than the wire itself. The described processing is further complicated by the influence of gravity. The molten portion is subject to the influence of gravity, which leads to different buildup welding results and/or elaborately adjusted process parameters depending on the welding position. Ultimately, the wire must currently be actively conveyed into the process zone. All known wire buildup welding processes are based on an actively fed wire material. This requires a suitable feed unit whose behavior must be adapted to the relative movement of the workpiece. The available feed rates limit the achievable build rate of the process. In addition, feed units for wire diameters smaller than 100 µm are not available.
Based on the above-mentioned problems, scientists at the Laser Zentrum Hannover e.V. developed a process including a device for the generative production of structures in which the wire and the substrate are only partially melted when a laser is coupled in laterally into the area where both materials meet in a sharp angle. The energy required for this is therefore lower than in conventional processes. This also reduces the influence of thermally induced distortion, which previously required a minimum thickness of the substrate. The cross-sectional width of the wire is not changed by the buildup welding process, so that buildup tracks of the same size as the wire width can be produced. Another advantage of the partial welding process and the comparatively small melt pool volume is the robustness of the weld result against gravity. In this way, the flexibility of the process is increased and, for example, vertical or overhead welding is possible. The achievable build rate depends solely on the relative movement of the positioning device with respect to the welding wire, insofar as the laser can provide sufficient energy for the welding process in the contact area. Relatively high build rates can therefore be achieved. Wires with less then 100 µm can also be processed this way, since the wire feed is implemented passively. The process is not material-specific and is therefore suitable for all materials that can be welded together.
- Welding wire and substrate are only partially melted.
- Therefore lower energy necessary for the melting process.
- Partial melting enables a continuous laser wire buildup welding.
- Smaller wires can be processed due to passive wire feeding.
- Higher buildup rates possible which are only dependent on the relative movement of the positioning device with respect to the welding wire
- Robustness versus gravity allows more flexible welding positions (vertical or overhead welding)
- Laser wire buildup welding
- Usage of fine wires for the welding process
- Two-dimensional structures consisting of buildup weld tracks created next to each other
- Grids: two-dimensional structures welded on top of each other with angular offset between the layers and welding at contact points
- Thin-walled structures by overlay welding of buildup weld tracks
Process successfully verified with stainless steel wires with 100 µm diameter on stainless steel substrate
Laser Zentrum Hannover e.V.
Dr. Markus Muchow
Patentmanager Physics, Technology and Software
Tel.: +49 551 30724 159