Wetting Behavior of CaO–SiO 2 ‐Based Mold Flux With Various Si Contents on the Steel Substrate

Abstract

The wetting behavior between CaO–SiO 2 ‐based mold fluxes and stainless steel substrate was investigated, as a function of elemental silicon (Si) content using sessile drop method. The results indicate that the contact angle decreases significantly from 56.7° to 39.2°, with a small addition of Si (2 wt%) at 1673 K. However, the contact angle increases to 49.5° gradually when Si content further increases to 6 wt%. A distinct layer with the thickness of 195–410 μm is found and analyzed by scanning electron microscopy and energy‐dispersive X‐ray spectroscopy, which reveals that Si migration occurs at the interface from the flux into the steel substrate. The migration of Si increases the polymerization of melt structure, as confirmed by X‐ray photoelectron spectroscopy and molecular dynamics simulations. The increase of bridging oxygen and complex Q 3 and Q 4 silicate units in melt structure as the Si content in flux is getting higher, which weakens the wettability of mold flux on steel substrate when more Si was added. The results highlight the role of Si in interfacial modification and melt‐structure evolution. These findings provide useful guidance for optimizing Si‐containing exothermic mold fluxes and improving flux/steel interfacial performance during high‐speed continuous casting.