Influences of Basicity and Li₂O on the Properties of Fluorine-Free Mold Flux for the Casting of Medium Carbon Steels

An investigation was carried out to study the influences of basicity and Li₂O on the melting, crystallization, and heat transfer behavior of Fluorine-free mold flux designed for the casting of medium carbon steels using double hot thermocouple technology and infrared emitter technique. The results showed that with the addition of basicity, the melting and crystallization temperatures of the mold fluxes were increased, and the final heat transfer rate was reduced, as the basicity tends to promote the crystallization behavior of the designed mold fluxes. Besides, with the increase of Li₂O content in the mold flux, the melting and crystallization temperature decreased, as the Li₂O tends to inhibit the formation of high melting temperature crystal and lower the system melting temperature zone; meanwhile the crystallization capability of the mold flux was enhanced in the low-temperature region. Moreover, the results of EDS and XRD were confirmed that the main crystal phase in the Fluorine-free mold fluxes is calcium borate silicate (Ca₁₁Si₄B₂O₂₂). Those results obtained can provide guidelines for the design of new Fluorine-free mold flux for the casting medium carbon steels.