- Using the CO2 laser in the TEM01* mode, all investigated copper and aluminium alloy strips can be seam welded with good results. With the 2.5 kW laser, incoupling was sufficient for all materials, except for electrolytic copper, where a thin nickel layer was needed.
- Seam and spot welds made with a pulsed Nd:YAG laser are much more sensitive to hot cracking, possibly because the available laser power did not allow a sufficient high pulse rate.
- Hot cracking can be reduced, by choosing the proper weld geometry; in order of weldability: standing-edge, overlap-fillet and overlap-penetration. Butt welding is benific- ial for aluminium, but more difficult for copper alloys.
- In the Nd:YAG welding of heat treatable aluminium alloys in difficult geometries, cracking could be prevented in general using AlSi filler material.
- In ND:YAG welding of copper alloys, a thin nickel layer is also required to improve incoupling in E-Cu. A Sn filler material is sometimes beneficial in reducing the effect of tin loss in the welding of CuSn8.
- In comparing laser soldering, brazing and welding in joining copper wires with different insulation layers to CuSn8 strips, it is concluded that brazing offers better results than soldering. However, laser welding with relatively low intensity and long pulse times gives the best results. The optimum joint geometries were established in the project.
- An intelligent control system, based on the detection of emission from the plume, could successfully be used to improve the Nd:YAG welding of aluminium in the overlap-penetration geometry.
- An approach was developed for the modelling of stresses in welding which lead to cracking. The model was based on the assumption that cracking occurs it the total (von Mises) stress in the heated weld zone is larger than the local rupture strength at the relevant temperature. This approach is not yet fully tested.
Laser welding of cooper, aluminium and their alloys is difficult, due to the high reflectivity for laser radiation, their high thermal conductivity, and the crack sensitivity of some of the alloys. In this project, laser welding, brazing, and soldering will be studied. This will be performed using alloys commonly used in the electrical, electronic, domestic appliances, and automobile industry. CO2 and Nd: YAG lasers will be used. The project will focus on the establishment of design rules for laser joining, and on the identification of methods for on-line control of the processes. Experiments will be supported by modelling. Finally all the results will be collected in a database.
Funding Schemeundefined - undefined
5943 AD Lomm
7550 KA Hengelo