Influence of Fluorine and CaO/Al₂O₃ Ratio on the Wetting Behavior Between CaO–Al₂O₃‐Based Mold Flux and Steel Substrate

Abstract

The wetting behavior of flux melt on the initial solidified shell greatly determines the slag entrapment in the casting product and the sliver defect in the rolled product. Herein, the wetting behavior of CaO–Al2O3‐based mold flux with various fluorine (F) contents and CaO/Al2O3 (C/A) ratio on steel substrate is studied using the sessile drop method. Results show that the contact angle decreases from 71.35° to 59.86° and from 65.96° to 22.73°, meanwhile, the interfacial tension decreases from 1743.02 to 1669.69 mN m−1 and from 1705.40 to 1448.53 mN m−1, with the addition of F and the increase of C/A ratio, respectively. X‐ray photoelectron spectroscopy analysis indicates that the addition of F and increase of C/A ratio lead to positive adsorption () of non‐bridging oxygen (O−) and free oxygen (O2−) at the interface, which is the main reason why the interfacial tension between the mold flux and steel is reduced and the wettability of flux droplet on the steel is enhanced.