Numerical simulation of an electromagnetic weld pool control for high power laser beam welding of high thickness metal parts

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The positive results of computer simulation of electromagnetic meltpool control as well as their experimental verification for high power laser beam welding of thick plates of AlMg3-alloy and austenitic stainless steel Type 304 gained in the first phase of the project show good perspectives for applicability of this technology. The extension of the technology for the case of ferromagnetic materials seems to be very attractive. The prolongation option was already considers in the original project. The molten metal and partially the material in HAZ, which is overheated above the Curie-Temperature TCurie , do not exhibit ferromagnetic properties. The rest part of the workpiece is ferromagnetic and hinders the transfer of generated magnetic fields to the meltpool. In order to minimize the influence of the ferromagnetic zone we suggest to guide a strong DC magnetic field into material, in order to magnetize the workpiece over the saturation limit. The experimental trials will take place first with light ferromagnetic duplex steel, where application of this method would be possible at low magnetic field strength values. For this material the magnetic fields values of 1 T would be enough for orientation of magnetic domains correspondent to direction of the external magnetic field. Herewith the effective permeability is very low. The simulation of ferromagnetic zone will take place by using of OPERA software, which enables a simulation of nonlinear effects like temperature dependent hysteresis and saturation effects in ferromagnetic materials. In molten pool zone the new computer simulation by means of COMSOL-Multiphysics will be carried out. This will use the results of OPERA-Simulations as boundary conditions at the border between ferromagnetic and non-ferromagnetic regions (T = TCurie) .The results obtained from welding trials and computer simulations will be transferred to the normal mild steels.