2015 Volume 55 Issue 4 Pages 821-829
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.