Effect of active fluxes on thermophysical properties of 309L stainless-steel welds

The thermal history during the A-TIG welding and thermophysical properties of 309L stainless steel were measured using infrared thermometry and a thermal conductivity analyzer. A Manual-HKS weld scanner was introduced to detect the fluctuation of welding parameters, and changes in welding current were analyzed. The mean temperature at the measuring point increased when an active agent was added to the coating layer. Weld penetration increased from 2.8 mm to 5.24 mm compared with conventional tungsten inert-gas welding. The thermophysical properties of weld beads were switched with different contents of calcium fluoride, effusivity, thermal conductivity and diffusivity decreased with increasing calcium fluoride, a reverse was observed for calcium fluoride surpassed 3 wt.%. The microstructure of the welded region was found to contain equiaxed ferrite due to the proper heat applied and alloying element distribution. The obtained results can illuminate the mechanisms of penetration increase and changes in physical properties of weld beads.