Microstructural and mechanical evaluations of SAW by manufactured granular basic bonded Cr, Mo, and Cr–Mo active fluxes on ST37 low carbon steel

Bead-on-plate submerged arc welding was conducted on St37 steel by manufactured Cr, Mo, and Cr–Mo active basic fluxes produced via the unfused bonded method. The base metal heat-affected zone and weld metal (WM) microstructures were identified and characterized by optical microscopy and scanning electron microscopy. Furthermore, each element’s recovery rate ( η ) and slag factor ( α ) determine the amount of element transferred from flux into WM. Then, the ferrite morphologies volume fraction of WMs was measured. Moreover, the chemical analysis of slag and inclusions was evaluated by point scan energy-dispersive X-ray spectroscopy and extensively discussed. The number density and size of the inclusions as well as their effects on the acicular ferrite (AF) formation were also elaborated. Then, the WMs’ longitudinal tensile strength and Vickers hardness (HV) were measured. Finally, the Charpy V-notch test was conducted to determine the impact toughness; the fracture surfaces were investigated, as well. Graphical abstract