Microstructural and Mechanical Properties of X70 Pipeline Steel Welds Using Formulated Shielded Metal Arc Welding Electrodes

For offshore structures, shielded metal arc welding remains the preferred procedure. The development of welding electrode coatings is required for high-strength pipeline steels. The study compares the mechanical characteristics of the welds prepared using a developed welding electrode and a commercial E8018-G electrode. The electrode flux coating is made up of fluoro-alumino-silicate systems. The developed flux was coated on the ER80S-Ni1 electrode. The mechanical and metallurgical investigation shows significant improvement. The Ni content reduces polygonal ferrite and further refines the grain boundaries. The effect of Ni is conditional; welds with 1.26% Ni performed better than those with 1.38% Ni. SEM revealed that MA increases with Ni content. The microhardness test was performed; the weld strength matching ratio for the commercial electrode weld was 0.87; for the weld with the developed electrode, it was 1.12 and 1.06. The impact toughness results were nearly similar. The microstructure displays thin grain boundaries and acicular ferrite morphology. The developed coating fluxes promote favorable inclusion sites. These features enhance both strength and toughness. The experimental results are in good agreement with the predicted thermodynamic model results. © The Minerals, Metals & Materials Society 2025.