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-With modern high-power lasers (and vacuum) penetration around 100 mm is possible
-Important for industrial applications: single-pass full penetration welds with tolerances
-Contactless EM-backing helps to overcome many main restrictions:
-Single-pass HLAW of up to 30 mm can be realized with 20 kW laser power
-Increase of the gap bridgeability and misalignement of edges
-Lower sensitivity to manufacturing tolerances and edge quality; samples can be prepared by a plasma-cut instead of time-consuming milling process
-Gives the possibility to increase the welding parameter window and cooling rate so that the required mechanical properties can be reached
-Improved filler wire mixing behaviour
High-power hybrid laser arc welding of thick materials with electromagnetic weld pool support
(2023)
In addition to the many advantages of deep penetration, increased welding speed and a low sensitivity to manufacturing tolerances such as gap and edge offset, the hybrid laser arc welding (HLAW) process is used increasingly in industrial applications such as shipbuilding or pipeline manufacturing. Nonetheless, thick-walled sheets with a wall thickness of 20 mm or more are still multi-pass welded using the arc welding process, due to increased process instability by increasing laser power. Welding at reduced speed, especially in a flat position, leads to an irregular formation of the root part such as dropping. The hydrostatic pressure exceeds the surface tension, which decreases with increasing seam width. In order to prevent gravity drop-outs, the use of a melt pool support is necessary. Usual weld pool supports such as ceramic or powder supports require time-consuming mechanical detachment. The electromagnetic weld pool support system, which is described in this study, operates without contact and based on generating Lorentz forces in the weld pool. An externally applied oscillating magnetic field induces eddy currents and generates an upward directed Lorentz force, which counteracts the hydrostatic pressure. This allows single-pass welds up to 30 mm by hybrid laser arc welding process with a 20-kW fibre laser. Moreover, it is favoured by the diminished welding speed the cooling rate which leads to an improvement of the mechanical-technological properties of the seams – the lower formation of martensite in the microstructure enables better Charpy impact toughness. The electromagnetic weld pool support extends the limitation of the laser hybrid welding process in the thick sheet area. By adapting the electromagnetic weld pool support to the laser and laser hybrid welding process, the application potential of these technologies for industrial implementation can be drastically increased.