Laser beam welding of atmosphere aluminium die cast material using high frequency beam oscillation and brilliant beam sources

摘要

In serial production of components for automotive applications such as cooling and air-conditioning systems, aluminium die-cast material is frequently used due to its excellent castability. The aim of providing light weight components can be approached with thin walled cross sections even for complex structural parts. However, cast components are usually joined to semi-finished products, such as profiles or tubes. The joints are mostly required to be pressure tight. The joining technique for those applications has to be highly productive to obtain high component outcome as well as cost-efficient. Laser beam welding techniques are especially suitable for those tasks. Die-cast components have limited or no weldability due to their manufacturing process. Reasons for that are entrapped gases within pores or cavities under high pressure conditions. Furthermore, the mold release agents for the die-cast process are inappropriate for obtaining homogeneous and sound weld seams. Consequently, a high amount of pores in the weld seam and stochastic melt pool blow-outs occur, which prohibit mostly the use of the component. To solve these issues a new welding technique, remoweld T, has been developed at Fraunhofer IWS. The unique method has been extensively tested and transferred to serial-production. The decisive step was to use laser sources with brilliant beam quality in combination with a high frequency beam oscillation within the melt pool. In this paper the technological approach will be presented. With the remoweld T method it was possible to obtain homogeneous weld seams with low porosity and a strongly reduced distortion for the first time. Minor component tolerances and a reproducible joining technique with a high output for serial production can be achieved.