Solidification Control of Austenitic Stainless Steel Weld Metal by Electromagnetic Stirring

The effect of electromagnetic stirring on the microstructure of a fully austenitic stainless steel weld metal was investigated. The parameters examined to achieve the grain refinement were magnetic field intensity, the frequency of alternate stirring and the relative distance from electrode to magnetic field center. Bead-on-plate TIG welds were made under the conditions that welding current was 60A and travel speed was 3 cm/min. A significant decrease in the grain size of the weld metal could be achieved when the electrode was located 1 to 2 cm apart from the magnetic field center in the welding direction and the stirring frequency was 0.5 to 1 Hz. It was the most likely that the remelting of a primary dendrite arm by stirring a molten metal played a role cf the grain refinement of a weld metal, and both the existence of fragments separated from a primary dendrite arm and the increase in constitutional supercooling ahead of solid-liquid interface due to the molten-metal stirring assisted the weld metal in grain refining.