A comparison study on interfacial properties of fluorine-bearing and fluorine-free mold flux for casting advanced high-strength steels

A comparison study on interfacial properties of a traditional fluorine-bearing (F-bearing) mold flux and a newly designed fluorine-free (F-free) mold flux to produce advanced high-strength steels (AHSSs) by compact strip production technology was conducted. The results showed that these two kinds of mold fluxes gradually spread out on the typical AHSS substrate when slags began to melt with the increase in heating temperature, and they had a good interfacial ability between the two mold fluxes and the AHSS substrate, and there was no other interfacial reaction except the oxidization of steel substrate by the mold fluxes. In comparison, the wettability of the designed F-free mold flux with the AHSS substrate was better than that of the F-bearing mold flux. The reason could be explained as the addition of B₂O₃ would increase the complexity and polymerization degree of the melt structure and weaken the attractive force between the ions and ionic groups, then leading to a better wettability. Besides, B₂O₃ is an effective flux, which can reduce the melting temperature obviously, and the surface tension of the liquid F-free mold flux would get reduced with the addition of B₂O₃.