Microstructure and mechanical properties of laser-MAG hybrid welded thick-section weathered steel joint

Weathered steel (S355J2W) joint was prepared by laser-metal active gas hybrid welding technique. The microstructures of the joint were examined with an optical microscope and a scanning electron microscope. Microhardness measurement, tensile test, side bend test, and Charpy impact test were conducted to examine the mechanical properties of the joint. Experimental results show that S355J2W steel joint has a nail head shape with three different zones: weld metal, heat-affected zone (composed of overheated zone, normalized zone, and incomplete normalized zone), and base metal. The highest microhardness of the joint is 280 HV. All the joint specimens failed in the base metal. Average tensile strength of 502.6 MPa and yield strength of 380.9 MPa were achieved. A bending angle of 180A degrees was obtained for all the joint specimens, and a crack less than 3 mm was detected. The average values of absorbed energy for the weld are 198.7 and 79.1 J at -40 and -20 A degrees C, respectively. All the specimens exhibited a level of toughness as indicated by deformation at the fracture surface.