HEAVY DUTY APPLICATIONS
THICK STEEL STRUCTURE WELDS FOR WIND TURBINE TOWERS
T
he demand for clean energy has been steadily increasing in recent decades. The share
of renewable electricity generation in the European Union (EU) in total was around 38% in 2021. The basic structure of a wind turbine
(WT) tower follows similar general production steps. Prepared steel plates with a plate width of around 3 m and a thickness of up to 30 mm are first bent into a ring by machine. They are then joined with a tack weld and a longitudinal seam. After the rings have been aligned, around 10 rings are joined to form a section of 30 m with the aid of 9 circumferential weld seams. This is followed by flanges being attached, bolts welded on, door or hatch prepared, non-destructive tests carried out, painted, fitted inside with ladders and electrical lines and finally prepared for transport. The most common welding processes
when joining thick-walled steels in the industry are arc-based welding processes such as GMAW or SAW. Often, the sheets
are joined in multi-layer technique, which can lead to productivity losses due to long welding times. The process- specific challenges in welding thick steels using multi-layer technique relate to the high heat input from the process. Therefore, alternative welding processes are being actively sought. A suitable alternative is provided by beam-based welding processes such as the laser hybrid welding processes, that offer deep penetration welds and lower heat input. Implementation of the laser hybrid
welding process in heavy industry, such as the WT industry, offers economic benefits such as the increase in productivity by reducing the layer number, and the lower consumption of filler material and energy. When comparing SAW welded 25 mm thick steels in five to six layers and single-pass laser hybrid welding, the welding time can be reduced more than 80% and the costs of filler material, flux and energy can be saved up to 90%. However, the industrial use of the laser hybrid welding process is still limited to applications, where the
34 / WELDING WORLD MAGAZINE - ISSUE 04 - AUGUST 2025
material thickness does not exceed 15 mm due to some process-specific challenges such as the sagging, sensitivity to manufacturing tolerances such as gaps and misalignment, limited filler wire mixing, and deteriorated mechanical properties resulting from high cooling rates. To overcome these challenges, a
WeldNova contactless electromagnetic backing based on an externally applied AC magnetic field can be used. Eddy currents are induced due to the oscillating magnetic field, and an upward-oriented Lorentz force is generated to counteract the droplets formed due to gravitational forces. It allows to weld up to 30 mm thick
structural steels in a single-pass with a 20 kW fibre laser system. Additionally, the gap bridgeability and the misalignment of edges were increased to 2 mm when welding 20 mm thick steels. With the aid of the AC magnetic field, a vortex was formed in the weld root, which had a positive effect on the filler wire mixing. A further significant advantage of the EM backing
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