Development of an Efficient Spectroscopic Droplet Collection System for Probing Ca Transfer Mechanisms during Submerged Arc Welding

This study delves into the intricate world of submerged arc welding (SAW), focusing on the transfer mechanisms of calcium (Ca) and other alloying elements. Through a sophisticated integration of spectral diagnostics, droplet collection, and welding experiments, the research provides a comprehensive analysis of element transfer behaviors and their impact on weld metal (WM) composition. The investigation employs a CaO–SiO2–MnO flux system, chosen for its relevance to shipbuilding steels and its gradient in oxygen potential, which allows for a systematic examination of the influence of oxygen potential on element transfer. One of the key findings is the detection of Ca in the arc plasma and droplets, challenging the traditional view that Ca does not participate in element transfer due to the high thermodynamic stability of CaO. The study reveals that while Ca can transfer from fluxes to droplets, it does not transfer into the WM, highlighting the complex interplay between arc conditions and thermodynamic equilibrium. The research also explores the transfer behaviors of silicon (Si) and manganese (Mn), demonstrating that their contents in both droplets and WM decrease with increasing CaO content in the fluxes. The transfer ability of these elements is shown to follow the order of Ca < Si < Mn, aligning with the increasing oxygen potential of their corresponding oxides. The study concludes that the participation of oxides in the element transfer process is not solely determined by their oxygen potential, and that elements with higher oxidation affinity are more susceptible to oxidation and subsequent loss within the weld pool. This groundbreaking research offers valuable insights for optimizing WM composition and advancing the understanding of element transfer mechanisms during SAW.