Influence of AC magnetic field on the cladding layer during the micro beam plasma welding of austenitic stainless steel

In the process of micro beam plasma welding of thin-walled parts, gravity and surface tension make a molten metal flow downward, sometimes causing a bad formation. To solve this problem, a new external magnetic field-controlled method based on the eddy current principle was proposed. The distribution of the magnetic flux density, the induced current density, and the Lorentz force on a 4 mm stainless steel AISI 304 thin plate was examined using different oscillation frequencies (1, 5, 10 kHz) of the magnetic field with the finite element package COMSOL Multiphysics 5.0. The higher frequency was found to be more helpful to create greater electromagnetic force. This study examined the single-pass and three-layer welding of the 4-mm-thick stainless steel AISI 304 with different magnetic fields (3~12 mT) at 10 kHz. The results show that 7- and 8-mT magnetic fields were effective in suppressing the sagging of the cladding layer.