Optical Properties of Bismuth Borate Glasses Doped with Zinc and Calcium Oxides

Some bismuth-borate oxide glass' samples were prepared by the fast quenching method, where B2O3 was replaced with equal concentrations of ZnO and CaO. X-ray diffraction (XRD) was used to examine the internal structure and Fourier transform infrared (FTIR) to identify building units and bonds throughout the studied structural matrices. XRD showed that all samples have short range order structural nature, while FTIR demonstrated some of Zn2+ acted as glass network formers and all Bi3+ acted as glass. UV-visible measurements and calculations showed a decreasing in the energy band gap from 3.83 eV to 1.73 eV with decreasing B2O3 content. Also with decreasing B2O3 content, both real refractive index and metallization factor decreased from 3.1 to 1.9 and from 0.56 to 0.71, respectively. For the studied glass' samples, density and molar volume showed inverted behaviors, where the density decreased while the molar volume increases with decreasing B2O3.

Effects of B2O3 on Melting Characteristics and Temperature-Dependent Viscosity of High-Basicity CaO–SiO2–FeOx–MgO Slag

In order to reduce the amount of fluorite during the steelmaking process for environmental protection, it is essential to investigate the fluorine-free slag system. Thus, high-basicity CaO–SiO2–FeOx–MgO slag with B2O3 content from 0% to 15% was designed, and its melting characteristics and viscosity were investigated. The influence of B2O3 content on the phase diagram of the slag system was calculated using FactSage 7.3, and the break temperature was determined from the curves of temperature-dependent viscosity. The results show that, with the increase in B2O3 content, the melting characteristics of the CaO–SiO2–FeOx–MgO/B2O3 slag system, including liquidus temperature, flow temperature, softening temperature, and hemispheric temperature, all decreased; the main phase of the slag system transformed from Ca2SiO4 into borosilicate, and finally into borate; the viscous flow activation energy reduced from 690 kJ to 130 kJ; the break temperature reduced from 1590 °C to 1160 °C. Furthermore, the melting characteristics and the break temperature of the slag system with 5% and 8% B2O3 content were found to be the closest to the values of fluorine-containing steel slag.

Effect of B2O3 on the Crystallization Behavior of CaF2-Based Slag for Electroslag Remelting 9CrMoCoB Steel

The non-isothermal crystallization characteristics of the electroslag remelting (ESR)-type slag with varied B2O3 contents were investigated by non-isothermal differential scanning calorimetry (DSC), field emission scanning electron microscopy (SEM-EDS), and X-ray diffraction (XRD). The crystallization mechanism of the B2O3-bearing slag was also identified based on kinetics analysis. The results showed that the primary crystalline phase was CaF2, there was no change in the type of the primary crystal as B2O3 content increased, and the morphology of the CaF2 crystal was mainly dendritic. The sequence of crystal precipitation during the cooling process was CaF2 to Ca12Al14O32F2 and MgO/MgAl2O4, followed by Ca3B2O6. The activation energy of CaF2 crystallization increased firstly, then decreased and reached stability, while the activation energy of Ca3B2O6 crystallization increased continuously with the increasing B2O3 content. The crystallization behavior of CaF2 was three-dimensional growth with a constant nucleation rate. The proper B2O3 content added into the CaF2-based ESR slag should be around 1.0% to limit the precipitation of the CaF2 crystal to attain good surface ingot quality and stable ESR operation.

Design of ESR Slag for Remelting 9CrMoCoB Steel under Simple Protective Ar Gas

Thermodynamic calculations by using Factsage 7.3 and simple protective gas electroslag remelting (ESR) experiments were conducted to design the appropriate ESR slag for remelting the qualified 9CrMoCoB ingot. First, the proper basic slag was determined based on the phase diagram of CaF2–CaO–Al2O3–x%MgO calculated using Factsage 7.3. Second, equilibrium reactions between 9CrMoCoB and the basic slag containing varied SiO2, and B2O3 contents were calculated to study the effects of B2O3 and SiO2 on B, Si, and Al contents in steel. Then, equilibrium reaction experiments were conducted to validate the calculated results. Finally, the appropriate slags were attained and the simple protective Ar gas ESR experiments were conducted to make a verification. Results showed that the liquid phase region of the slag of CaF2–CaO–Al2O3–x%MgO at 1300–1400 °C increased first, then decreased with the MgO addition. With the B2O3 content increasing, the boron content increased, while the Si, Al contents decreased, and at a given B2O3 addition, the B and Al contents decreased with the SiO2 content increasing, whereas the Si content increased. The appropriate slags for simple protective gas ESR remelting 9CrMoCoB were 55%CaF2–20%CaO–3%MgO–22%Al2O3–2%SiO2–1.3%B2O3 and 55%CaF2–20%CaO–3%MgO–22%Al2O3–3%SiO2–1.7%B2O3.

PHYSICAL PROPERTIES OF SLAGS OF CaO – SiO2 – B2O3 SYSTEM CONTAINING 15 % OF Al2O3 AND 8 % OF MgO

Influence of the chemical composition of CaO – SiO2 – B2O3 oxide system containing 15 % Al2O3 and 8 % MgO (in this expression and hereinafter indicated by mass %) on viscosity and crystallization temperature was studied using experiment method of simplex lattice planning. Addition of B2O3 to the slags of oxide system expands the range of slags composition with a low crystallization temperature and viscosity. Slags with a basicity of 2 – 3, containing 1 – 3 % of B2O3 are characterized by a low crystallization temperature, varying from 1400 to 1450 °С and have high flowability. The viscosity of such slags when heated to 1550 and 1600 °C does not exceed 0.20 and 0.15 Pa·s, respectively. An increase in B2O3 content to 4 – 6 % in slags with a basicity of 2 – 3 is accompanied by a decrease in crystallization temperature to 1350 – 1425 °C with keeping low, not more than 0.15 Pa·s, viscosity in the range of heating temperatures at 1550 and 1600 °C. The displacement of formed slags containing 1 – 6 % of B2O3 to the area of increased basicity up to 3 – 5 preserves their relatively high fluidity. In this case, with an increase in B2O3 concentration, there is a clear tendency for the studied oxide system to shift to the region of low crystallization temperatures. Crystallization temperature of slags with basicity of 3 – 4 containing 6 % of B2O3 reaches 1400 °С and practically does not exceed 1475 °С of slags with basicity of 4 – 5 containing 1 – 2 % of B2O3 . At temperature of 1600 °C, the viscosity of such slags varies from 0.15 Pa·s with a basicity of 3 and a content of 5 – 6 % of B2O3 to 0.25 Pa·s in the basicity range of 4 – 5 with B2O3 content of 1 – 3 %. A decrease in temperature of the studied oxide system by 50 °C is accompanied by a slight (no more than 0.05 Pa·s) increase in viscosity.