Physical properties characterization of a peritectic mold flux formed from the addition of calcitic marble residue in the commercial one

Abstract

Mold fluxes play an important role in the lubrication and heat transfer control between the mold wall and steel shell during the continuous casting process. To ensure control of the heat transfer, it is necessary to evaluate the crystallinity of mold flux. The casting of peritectic steel commonly uses the mold flux that forms crystalline phases. These phases, in particular the cuspidine (Ca4Si2O7F2), increase resistance to radiation heat transfer, leading the steel to cool slowly and to ensure the production of defect-free products. The purpose of this paper is to create alternative peritectic fluxes obtaining gain due to the use of a cheaper raw material, avoiding the disposition of residues in the environment. Thus, using FactSage® software, new mold fluxes were simulated from a commercial peritectic flux with additions of calcific marble residue, SiO2 and CaF2. From the thermodynamics simulations, three new fluxes were chosen and experimentally developed. In those fluxes, the physical properties such as melting point, break temperature, phases and microstructure were analyzed and compared with the commercial peritectic flux. The measurements using Differential Thermal Analysis (DTA) showed that there was no significant change in the melting point and break temperature. Cuspidine, crystalline phases and dolomite were established in all new samples. By using the thin-film technique, it was possible to observe that the microstructures of the new fluxes obtained were similar to with the commercial one. The presence of acicular grains was the main difference in the sample with highest residue concentration. Keywords: Peritectic mold flux, Calcitic marble, Physical properties, Acicular grains