Melting and Heat Transfer Behavior of Fluorine-Free Mold Fluxes for Casting Medium Carbon Steels

Abstract

As fluxing agent, fluorine is important to the properties of mold flux; however, it tends to cause serious environment and health problems. In this paper, the melting and heat transfer behaviors have been studied by using Single Hot Thermocouple Technique (SHTT) and Infrared Emitter Technique (IET). The results show that the melting temperature range of F-free mold flux decreases with the addition of Na₂O/Li₂O and B₂O₃ contents; and the heat flux decreases with the increase of basicity and Na₂O/Li₂O, as well as the decrease of B₂O₃ contents. The analysis of EDS and XRD show that Ca₁₁Si₄B₂O₂₂ and Ca₁₄Mg₂(SiO₄)₈ are the two main precipitated crystalline phases in F-free mold fluxes, and the Ca₁₁Si₄B₂O₂₂ is common and stable crystalline phase in the designed F-free mold fluxes system that shows the potential to replace Ca₄Si₂O₇F₂ in the conventional F-containing mold fluxes. Besides, through the comprehensive comparison, Sample E (Basicity 1.15, Na₂O 7.92, Li₂O 1.97 and B₂O₃ 5.98) shows the closest performances with the benchmark conventional commercial mold flux and has the potential to be used for casting medium carbon steels.