Comparison of the Laser and Electron Beam Welding of Steel Sheets Treated by Nitro-Oxidation

摘要

Nitro-oxidized steel specimens welded by a CO_2 laser and an electron beam were examined for quality and integrity by visual inspection, microstructure, and microhardness analysis. Visual inspection of the specimens welded by laser revealed the lack of root penetration at maximal welding speed from the selected welding speed range (30 to 60 mm/s) and a neat weld at the welding speed of 40 mm/s. However, in comparison to laser beam welding, the electron beam welding (EBW) process produced the weld joints with a wider heat affected zone, while the weld joints were much more prone to porosity. The microstructure of the weld joints made by both the laser beam welding and EBW methods did not show any abnormalities in phase composition owing to the presence of nitrides in the surface layer of the materials welded after nitro-oxidation.