Effect of Slag Composition on the Distribution Behavior of Pb between FetO-SiO2 (-CaO, Al2O3) Slag and Molten Copper

Wang

Metallurgical and Materials Transactions E

2015

In order to lower the weight of automotive bodies for better fuel-efficiency and occupant safety, the demand for high Al-containing advanced high strength steel, such as transformation-induced plasticity and twinning-induced plasticity steel, is increasing. However, high aluminum content in steels would tend to significantly affect the properties of mold flux during the continuous casting process. In this paper, a kinetic study of the effect of Al 2 O 3 content on the crystallization behavior of mold flux was conducted by using the single hot thermocouple technique and the Johnson-Mehl-Avrami model combined with the Arrhenius Equation. The results suggested that Al 2 O 3 behaves as an amphoteric oxide in the crystallization process of mold flux. The precipitated phases of mold flux change from cuspidine (Ca 4 Si 2 O 7 F 2) into nepheline (NaAlSiO 4) and CaF 2 , and then into gehlenite (Ca 2 Al 2 SiO 7) with the increase of Al 2 O 3 content. The kinetics study of the isothermal crystallization process indicated that the effective crystallization rate (k) and Avrami exponent (n) also first increased and then decreased with the increase of Al 2 O 3 content. The values for the crystallization activation energy of mold flux with different Al 2 O 3 contents were E R0.8A7 = 150.76 ± 17.89 kJ/mol, E R0.8A20 = 136.43 ± 6.48 kJ/mol, E R0.8A30 = 108.63 ± 12.25 kJ/mol and E R0.8A40 = 116.15 ± 8.17 kJ/mol.

Section: A the Effect Of Al 2 O 3 Content On Continuous Cooling Crysmentioning

confidence: 99%

Effect of Al2O3 on the Crystallization of Mold Flux for Casting High Al Steel

Wang

Metallurgical and Materials Transactions E

2015

“…The sulfide capacity C s 2À was also calculated using the FactSage TM 7.3 software, [20,21] a commercial thermochemical computing package which has been widely used to obtain the equilibria of multicomponent, and multiphase metallurgical systems. [22][23][24][25][26][27][28][29][30][31] The effect of the different TiO 2 content and C/A ratio on C s 2À can be compared and the calculation results are plotted as iso-capacity contours in Figure 4. It can be easily found that the iso-capacity contours exhibit nearly the same tendency with the iso-a CaO contour in the present slag system: i) Sulfide capacity strongly dependent on the CaO content, ii) Sulfide capacity contours are parallel to the CaO saturation liquidus line, iii) Effect of TiO 2 content on sulfide capacity is less significant than that of…”

Section: Resultsmentioning

confidence: 99%

Desulfurization Behavior of Incoloy® 825 Superalloy by CaO-Al2O3-MgO-TiO2 Slag

Cho

Martinsson

Sichen

et al. 2021

Metall Mater Trans B

Self Cite

Ni-based superalloy, which has excellent high-temperature strength and corrosion resistance, is mainly used in aviation materials, high-performance internal combustion engines, and turbines for thermal and nuclear power generation. For this reason, refining the impurities in Ni-based superalloys is a very important technical task. Nevertheless, the original technology for the melting and refining of Ni-based superalloys is still insufficient. Therefore, in this study, the effect of the CaO-Al2O3-MgO-TiO2 slag on the removal efficiency of an impurity element sulfur in Incoloy® 825 superalloy, one of the representative Ni-based superalloys, was investigated. The desulfurization behavior according to the change of TiO2 content and CaO/Al2O3 (=C/A, basicity) ratio as experimental variables was observed at 1773 K (1500 °C). Although the TiO2 content in the slag increases to 15 mass pct, the mass transfer coefficient of sulfur in molten alloy showed a constant value. Alternatively, under the condition of C/A > 1.0 of slag, the mass transfer coefficient of sulfur showed a constant value, whereas under the condition of C/A < 1.0, the mass transfer coefficient of sulfur greatly decreased as CaO decreased. Hence, in the desulfurization of Incoloy® 825 superalloy using the CaO-Al2O3-MgO-TiO2 slag, the TiO2 content in the slag does not have a considerable effect on the desulfurization rate and desulfurization mechanism (metal phase mass transfer controlled regime), but the basicity of the slag has a significant effect on desulfurization mechanism. When the slag basicity decreases below the critical level, i.e., C/A < 1.0, which is corresponding to sulfur distribution ratio, Ls < 200, it was confirmed that the desulfurization mechanism shifts from the metal phase mass transfer-controlled regime to the slag phase mass transfer-controlled regime due to the variation in the physicochemical properties of the slag such as viscosity and sulfide capacity. In addition, the different desulfurization rates between steel and Ni alloy melts were discussed by employing the diffusivity of sulfur in both systems.

“…The schematic diagram of the experimental apparatus is shown in previous articles. 17,18) The slag (7.0 g) and SiMn alloy (3.5 g) were held in graphite crucibles under a CO atmosphere to equilibrate. For reducing removal of phosphorous under a very low oxygen potential, CO gas was diluted with Ar, which was purified using silica gel also in addition to Mg turnings at 723 K. The oxygen partial pressure can be calculated based on the following reaction: 19) ... With a CO/(CO + Ar) ratio of 0.25, the oxygen partial pressure is about 1.7 × 10 -17 atm at 1 823 K. The CO gas was passed through Drierite (W. A. Hammond Drierite Co. Ltd., Xenis, OH), Mg(ClO4)2, silica gel, and soda lime to eliminate moisture and impurities.…”

Section: Methodsmentioning

confidence: 99%

Effect of Atmosphere and Slag Composition on the Evolution of PH3 Gas during Cooling of Reducing Dephosphorization Slags

Shin

Park

2013

ISIJ Int.

Self Cite

The distribution ratio of phosphorous between the CaO-CaF2 (-SiO2) flux and SiMn alloy melts at 1 823 K was measured under strongly reducing atmosphere. Furthermore, thermodynamic and kinetics analyses were carried out for the environmental stability of reducing refining slags containing Ca3P2 under wet cooling conditions from the effect of slag composition on the evolution of PH3 (phosphine) gas. The distribution ratio of phosphorous between the CaO-CaF2 (-SiO2) flux and SiMn metal phases increased with increasing CaO concentration in the flux, followed by a constant value. The composition for the saturating distribution ratio of phosphorous was in good accordance to the saturation content of CaO in the CaOCaF2 flux at 1 823 K. When the Vee ratio (= CaO/SiO2) of the dephosphorization slag was greater than about 1.35, the lime and dicalcium silicate phases precipitated during solidification, resulting in an increase in the evolution rate of PH3 gas under wet and dry conditions due to an increase in the reaction area. However, when the Vee ratio of the slag was lower than about 1.35, fluorite, cuspidine, and wollastonite phases precipitated from the phase diagram, resulting in less amount of PH3 evolution during cooling because the reaction between Ca3P2 and H2O was restricted to the surface of bulk slag.