Recycling Welding Fluxes: A Case Study into Manganese-Silicate System

Abstract

Recycling presents a waste-free solution to substantial disposal of welding slags which retain most components originated from the original fluxes. However, uncertainties in weld appearance and element contents render it unjustified to reuse welding slags as fluxes. In the present study, a manganese-silicate flux has been demonstrated to be fully recyclable subject to submerged arc welding (SAW) for three times. The weld appearance is assessed against the initial weld metal (WM), while alloying element contents are evaluated according to AWS (American Welding Society) requirements. Flux composition and structure, two decisive factors affecting welding performance, are quantified. It is manifested that compositional changes mainly occur in the contents of MnO (39.50 to 34.66 wt pct), SiO₂ (38.46 to 34.25 wt pct), and Fe_tO (1.55 to 6.78 wt pct). Moreover, crystalline structures of MgMnSiO₄, and Mg_0.6Mn_1.4SiO₄ appear in the initially amorphous flux. The crystallinity is enhanced to 32.7 wt pct through flux recycling. Slight depolymerization is found in the amorphous structure, as the NBO/Si (non-bridging oxygens per silicon atom) is elevated by 0.2. Overall, this study demonstrates the capability of recycling welding fluxes and is poised to offer insight into further sustainable applications.