Modeling and analysis by response surface methodology of hardness for submerged arc welded joints using developed agglomerated fluxes

TLDR: In this paper, the hardness of submerged arc welded joints by using developed agglomerated fluxes during submerged arc welding was evaluated using Response surface methodology (RSM) technique to conduct the experiments.

Abstract: The present study evaluates the hardness of submerged arc welded joints by using developed agglomerated fluxes during submerged arc welding. Response surface methodology (RSM) technique is used to conduct the experiments. Flux constituents MnO, CaF2, NiO, MgO and Fe-Cr are chosen as variables added into the main constituents CaO, SiO2 and Al2O3 to study the performance in terms of hardness. The results identify the most important constituents favoring the hardness are MnO, MgO, NiO and Fe-Cr, where as CaF2 is not so prominent to improve the hardness. The submerged arc welding (SAW) process is a versatile process; therefore, it is used for wide range of applications including the critical application, e.g., joining of pressure vessels, thick plates, ship hulls etc. In submerged arc welding, the arc is covered by flux. The constituents present in the flux controlled arc stability, bead shape and mechanical and chemical properties of weld metal 1 . The SiO2 content in the synthetic fluxes improves the welding performance. It is determined through metallographic examination that the presence of a metallic mist in the matrix of the flux and the amount of metallic mist in the flux increased with increasing silica content 2 . Colvin 3 in his study revealed that the basic fluxes are associated with the improved metallurgical properties of weld than the acidic fluxes. The study of commercial acidic fluxes by Bennett has correlated the slag detachability and weld-bead surface appearance to their chemical composition 4 . Ferrera and Olson 5 studied the performance of MnO-SiO2-CaO flux with respect to viscosity, arc stability, and weld-bead morphology. The flux behavior, flux chemistry and slag/metal interactions were reported elsewhere 6-10 . Terashima and Tsuboi 11 used highly basic agglomerated flux containing adequate amounts of carbonate and fluoride which produce low hydrogen weld metal.