In this study, the structure, viscosity characteristics, and crystallization behavior of CaO-SiO2-B2O3 based melts were studied combining molecular dynamics (MD) simulation, Fourier transform infrared (FTIR) spectroscopy, rotating viscometer test, and FactSage thermodynamic calculation. The results showed that, in the ternary CaO-SiO2-B2O3 glass system, stable structural units of [SiO4]4− tetrahedral, [BO3]3− trihedral and [BO4]5− tetrahedral were formed, and the Si-O and B-O structure depolymerize with the basicity increase from 1.15 to 1.25, then the B-O structure become complex with the basicity further increase to 1.35. In fluorine-free mold fluxes, with the basicity increases, the viscosity at 1300 °C increases, the liquidus temperature decreases and then increases, the network structure polymerizes, it indicates that the structural complexity rather than the melting property change plays a predominant role in increasing the viscosity at 1300 °C. Moreover, due to the changes in crystallization phase and solid solution ratio, the viscosity-temperature curve of fluorine-free slag shows the characteristics of alkaline slag and the break temperature increase with the basicity increase. The MD simulation, FTIR experiment, viscosity test, and FactSage calculation results are verified and complemented each other.
The reduction rates of manganese oxide by carbon and SiC was examined by heating MnO2-carbon and MnO2-SiC mixtures in a 7-kW industrial microwave oven. The results show that the rate of the reduction increased with the amount of carbon in MnO2-carbon mixture and with SiC in MnO2-SiC mixture. The rate of the MnO2 reduction by carbon was proportional to the reaction time, and that by SiC was proportional to 2/3 power of the reaction time. The reduction was found to be controlled by chemical reaction. The reaction rate constant of the reduction of MnO2kC increased with increasing the amount of carbon in the mixtures but kSiC decreased with increasing the amount of SiC in the mixtures.
Based on the actual process for smelting cold heading steel, this article adopts the single-slag process to smelt the low-carbon, low-silicon and high-alumina cold heading steel SWRCH6A, so as to study the effect of technological factors of the smelting process on the change of molten steel component in various working procedures and steel properties. The results show that, the smelting process control level for smelting high-Al cold heading steel using single-slag process is improved, the content change for main elements in the steel, w[Al]t and calcium treatment effect are stable, w[C] and w[Si] have a close relationship with w[P] and w[S]. The calcium yield after calcium treatment by single-slag process has a linear relation with w[Ca], and ηCa=2323.4*w[Ca] -1.040. The maximum calcium yield may reach 21%. All the mechanical properties of cold heading steel exceed the ML08Al standard. The smelting cold heading steel using single-slag process can fully reach the property requirements for cold heading steel grade.
Effect of ultrasonic treatment time on inclusions in high carbon steel with the addition of pure rare earth Ce was investigated. The results showed that ultrasonic treatment could disperse, refine and remove inclusions in molten high carbon steel with rare earth. With the increase of ultrasonic treatment time, total oxygen content of high carbon steel and average diameter of inclusions decreased evidently, inclusions in high carbon steel could be removed in a certain degree, but the number of the inclusions increased significantly. Total oxygen content (mass fraction) of high carbon steel, equivalent number I and average diameter d of inclusions in ingot was respectively 59×106, 134 entries•mm-2 and 2.91 μm when the ultrasonic treatment time was 60 s, at the same time, the percentage of inclusions with diameter D<2.31 μm is up to more than 43 % of the total.
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