Welding of the tube girder cover made of the C-Mn high strength steel

The welding procedure and technology for welding the cover of the tube girder is presented in this paper. The tube cover is made of the C-Mn high-strength steel. The welding has to be performed over the whole perimeter in the V groove. Since the structure in question is a very responsible one (a part of the assembly of the large hadron collider – LHC), the check of the base metal chemical composition and the mechanical properties had to be conducted before actual prescribing of the welding process type and the complete welding technology. Then the weldability of the base metal was estimated, which showed that this particular steel was conditionally weldable with application of preheating. The welding technology was prescribed, based on the previously determined parameters including the welding procedure and the filler metals selection. The prescribed technology was afterwards executed on the selected experimental samples. To verify that the selected technology was adequate, the hardness and the microstructure of all the zones of the welded joints were determined. Analysis of executed experimental welds on chosen samples has confirmed that the welding technology was appropriate and that it could be applied to the real part – the LHC assembly.