Improved degassing in laser beam welding of aluminum die casting by an electromagnetic field

An electromagnetic system was used to reduce the porosity in laser beam welding of aluminum die casting. The difference of electrical conductivities between gases and molten aluminum is used by an electromagnetic system to displace the included gases to the top during a laser beam welding process. It bases on generating Lorentz forces within the weld pool via an oscillating magnetic field. A partial penetration laser beam welding of standard die-cast aluminum alloy AC-AlSi9MnMg in flat position is used. An optimized laser beam process was taken to investigate the porosity content and the surface smoothing by applying an electromagnetic field. The produced weld seams were analyzed in cross section views, by x-ray imaging and by computer tomography (CT). Depending on the magnetic flux density, a significantly reduction of the porosity down to 75% can be achieved. Especially big pores can be removed successfully. A surface smoothing of up to 75% can also be reached by using this system.