Evaluation of Residual Stresses and Mechanical Properties of IF Steel Welded Joints by Laser and Plasma Processes

Interstitial free (IF) steel has an extensive application in the automotive industry where the Laser Beam Welding (LBW) process is widely used due to its high productivity. Similarly, the other used process, Plasma Arc Welding (PAW), is characterized by a greater energy concentration and current density and therefore lower distortion, higher welding speeds and higher penetration may be obtained. However, while the traditional welding processes have been extensively studied with regard to the generation of residual stresses, there are few studies about residual stresses analysis and characterization of LBW and PAW joints. Therefore, the aim of the present work is to analyse the residual stresses resulting from LBW and PAW processes by X-ray diffraction technique with sin²ψ method in IF steel butt joints. For both joints, macro and microstructure were characterized and mechanical properties were determined. Tensile residual stresses in the heat-affected zone (HAZ) and in the fusion zone (FZ) were verified for both welding processes.

Keywords:
interstitial free steels (IF); laser beam welding (LBW); plasma welding (PAW); residual stresses; X-ray diffraction; mechanical properties