Probing microstructural evolution in weld metals subjected to varied CaF 2 –TiO 2 flux cored wires under high heat input electro-gas welding

Fused CaF 2 –TiO 2 fluxes have been designed, prepared, and applied in the flux cored wires to join EH36 shipbuilding steels under high heat input electro-gas welding. Ensuing microstructural evolution in the weld metals subjected to varied CaF 2 –TiO 2 flux cored wires has been fully documented. It has been demonstrated that as the content of TiO 2 in the fused fluxes increases, columnar grain size increases, and major constituents in the weld metal change from lath bainite, to granular bainite, and then to acicular ferrite. Such phenomena are elucidated via salient chemical reactions involving oxygen pickup and concurrent titanium transfer.