Recycling of steel slag as a flux for submerged arc welding and its effects on chemistry and performance of welds

The slag generated by the steel plant has been utilized to produce submerged arc welding flux. The flux produced by recycling steel slag has been applied in the submerged arc welding process. The effects of recycled slag on the chemical composition, microhardness, and microstructure of weld metal have been evaluated. For chemical composition, weld pads were prepared and beads on plates for bead geometry were deposited. It has been found that the chemistry of welds deposited using recycled steel slag is acceptable in accordance with ASME specifications. It is further observed that the addition of 10% CaCO3, 20% SiO2, and 6% MnO to the steel slag during recycling provided 0.10% carbon, 0.11% Si, and 0.8% Mn, respectively, in the weld metal. The microstructure of welds produced using recycled steel slag contains acicular ferrite which is desirable for improved tensile and impact strength. The microhardness of weld metal prepared using recycled steel slag is 220.9 VHN, which is more than that of weld metal deposited with fresh flux. Smooth surface appearance and desirable bead profile having deeper penetration were obtained. It is interesting to note that the cost of recycled steel slag is economical by 62% in comparison with equivalent virgin flux available in the market. The developed technology after fine-tuning will be transferred to the industry for practical applications.