Effect of CaF2, FeMn and NiO additions on impact strength and hardness in submerged arc welding using developed agglomerated fluxes

This experimental study was conducted to evaluate the effects of CaF2, FeMn and NiO additives on impact strength and hardness of low carbon steel plate welds using submerged arc welding. Fluxes containing CaO, SiO2 and Al2O3 as base fluxes were designed and developed through agglomeration technique. CaF2, FeMn and NiO were added to these fluxes in the varying amounts of (2-8) %. Mathematical models were developed using design expert and these models were correlated with the Mn, Ni and C transfer to the bead. The mechanical properties also have been correlated with the microstructure developed and the oxygen content in the welds. CaF2 and FeMn are found significant factors for the impact strength while the interaction of CaF2 and NiO is significant for hardness of the weld. The optimum ranges for Mn and Ni contents that produce optimum impact strength and hardness also have been suggested. The basicity index of flux and the carbon equivalent of the welds also have been correlated with the mechanical properties of the welds. The impact strength was found minimum for those welds which were welded by fluxes having CaF2, FeMn and NiO each at mid-level of 5%, though the Δ Mn quantities for these welds were low.