TRANSFER OF ALLOYING ELEMENTS THROUGH, FLUX ADDITION DURING SUBMERGED ARC WELDING

Abstract

Submerged are welding process is most widely used are'welding proces for joining thick plates and pipes. The feature that distinguishes submerged arc welding from other arc welding processes is the granular amitterial. that covers the welding area. By common usage this. material is termed as flux.. The properties of weldment have been found to be. dependent on, flux-electrode- baseplate combinations and welding parameters. Flux plays a central role in achieving element transfer. Most widely used commercial `'fluxes •are CaO-SiO2-A1203 based fluxes•. Silicon based.-fluxes generally act as a source of dissolved oxygen which adversely affects the toughness of the weldment. Therefore, in present work transfer of Ni, Cr, Mn, Si & C has 'been chosen which in someway or other have important bearing on toughness of weldment'. The flux systems alongwith additions of NiO and Fe-Cr have been designed to study the Ni and Cr transfer to the .weldment through flux.. Minor, addions of MgO & CaF2 have also been made. While designing the fluxes, the main criterion was to have liquidus temperature less then, 1350°C. All the fluxes were prepared by agglomeration using inorganic binder i.e. sodium silicate. Sodium silicate also acts as arc stabilizer. Size consist of all the fluxes was kept uniform. These fluxes' were subsequently used for.. laying 3-high-bead-on-plate' welds on plain, carbon steel plate to minimise the effect of dilution. The welding parameters were kept constant for each flux combination. The present work was primarily confined to the -study of transfer of elements such as, Ni, Cr, Mn, Si & C to the weldment. with respect to electrode. Ni, Cr & Mn'. were anal~yddd' ; - by atomic absorption spectrophotometer,, Si was analysed • gravimetrically by chemical analysis method and C'-by carbon-sulphur analyser. • With the help of data obtained on element' transfer a relationship has 'been developed between the flux composition and the gain or loss of element in the weldmentduring welding. Agglomerated fluxes containing CaCO3 as. oneofc-the .major constituent invariably increase the Oxidising power of flux. ' A significant loss of Mn and Si in the presence of these fluxes has been resulted. Whereas Ni was transferred almost as it was in the fluxes and Cr showed the °dependence of its trari"sfer on Fe-Cr' content.