Flux column effects on metal transfer mechanism in a rutile-type FCAW: insights from comparisons with MCAW and GMAW

Abstract This study investigates the role of the flux column in the metal transfer process of Flux-Cored Arc Welding (FCAW). Three rutile-type wires with varying flux ratios were compared with metal-cored and solid wires under Ar-CO 2 shielding at 220—280 A. Transfer frequencies increased with current for all wires. At 280 A, FCAW and Metal‑Cored Arc Welding (MCAW) showed higher frequencies (142.9 and 240.5 Hz) than Gas Metal Arc Welding (GMAW) (69.8 Hz). At 220 A, FCAW and MCAW showed similar frequencies (82.1 and 71.8 Hz) attributed to long flux or metal columns (un-melted metal core), which prevented neck formation by the Lorentz force. In the 250—280 A range, the MCAW frequency increased significantly, reaching 168% of FCAW, likely because melting shortened the metal column, allowing the Lorentz force to act more effectively on droplets. Increasing the flux ratio from 12 to 20% slightly reduced flux column length and increased frequency from 131.4 to 162.8 Hz at 280 A. The ratio of Wire Feed Speed (WFS) to transfer frequency was proportional to droplet diameter. WFS increased linearly with current for all wires. Droplet diameters decreased sharply for MCAW (1.60 to 1.20 mm) and GMAW (2.43 to 1.72 mm), but only slightly for FCAW (1.60 to 1.45 mm) in the 220—280 A range. Through comparisons of frequencies and WFSs, the former was a dominant factor for controlling droplet diameters. Consequently, the results suggest that the flux column length governs the droplet size in FCAW.