Economical joining of tubular steel towers for wind turbines employing non-vacuum electron beam welding for high-strength steels in comparison with submerged arc welding

Abstract

Owing to restricted energy resources and the worldwide ambitions to reduce CO2 emissions, renewable energy sources, such as wind energy, are gaining economical interest and promise great growth potential. This is closely connected with the increase of plant unit sizes. The wall thickness of the tower construction is rising accordingly and leads to increasing costs for the joining technology. The rising number of weld passes for submerged arc welding (SAW) leads to rising process times and high filler material consumption. The employment of non-vacuum electron beam welding (NVEBW) can significantly reduce the number of passes, the welding time, and the filler consumption. A substantial aspect of the control of the welding process is the formation of solidification cracks. Formation mechanisms and preventions methods such as preheating, alloying, and full penetration welding will be presented and experimentally backed up. The subsequent application of the SAW and NVEBW processes will be compared to standard multi-pass SAW for an exemplary weld of 30 mm thick high-strength steel. An additional aim of current research is the overall reduction of the wall thickness of wind turbine towers applying high-strength steels. Here, it is of chief concern to preserve the advantages of the material.