A novel method of roasting high-titanium slag with concentrated sulfuric acid was proposed to prepare titanium dioxide, and the roasting kinetics of titania was studied On the basis of roasting process. The effects of...A novel method of roasting high-titanium slag with concentrated sulfuric acid was proposed to prepare titanium dioxide, and the roasting kinetics of titania was studied On the basis of roasting process. The effects of roasting temperature, particle size, and acid-to-ore mass ratio on the rate of roasting reaction were investigated. The results showed that the roasting reaction is fitted to a shrinking core model. The results of the kinetic experiment and SEM and EDAX analyses proved that the reaction rate of roasting high-titanium slag with concentrated sulfuric acid is controlled by the internal diffusion on the solid product layer. According to the Arrhenius expression, the apparent activation energy of the roasting reaction is 18.94 kJ/mol.展开更多
Metallographic microscopy,scanning electron microscopy and TiN growth thermodynamic and kinetic equations were used to investigate the morphology,quantity,and size of TiN in the center of high-titanium high-strength s...Metallographic microscopy,scanning electron microscopy and TiN growth thermodynamic and kinetic equations were used to investigate the morphology,quantity,and size of TiN in the center of high-titanium high-strength steels under different solidification cooling rates.The results showed that TiN in the center of the experimental steels mainly existed in three forms:single,composite(Al2O3-TiN),and multi-particle aggregation.TiN began precipitating at around 1497℃(solidification fraction of 0.74).From the end of melting to solidification for 180 s,the cooling rates in the center of the experimental steels for furnace cooling,air cooling,refractory mold cooling,and cast iron mold cooling tended to stabilize at 0.17,0.93,1.65,and 2.15℃/s,respectively.The size of TiN in the center of the experimental steel cooled using furnace cooling was mainly concentrated in the 5-15 pm range.In contrast,the size of TiN in the center of the experimental steels cooled using air cooling,refractory mold cooling,and cast iron mold cooling were mainly concentrated in the 1-5 pm range.In addition,their density of TiN in the center of the experimental steels is signif-icantly higher than that of the furnace-cooled experimental steel.Thermodynamic and kinetic precipitation models of TiN established predicted the growth size of TiN in a high-titanium high-strength steel when the solidification cooling rates are not below 0.93℃/s.展开更多
Continuous casting of high-titanium steels face significant challenges due to steel-flux reactions,which will cause rapid compositional deviations and impair operational stability.A kinetic model to predict real-time ...Continuous casting of high-titanium steels face significant challenges due to steel-flux reactions,which will cause rapid compositional deviations and impair operational stability.A kinetic model to predict real-time mold flux composition evolution by integrating multicomponent mixed-transport-control theory with thermodynamics computing platform was developed in the current study.The model employed a cyclic time-step algorithm to compute thermodynamic equilibrium in reaction layer,mass transfer flux between reaction and bulk layers,and composition updates in reaction and bulk layers.The accuracy of the model was validated by plant trial data.The effect of casting parameters and initial compositions on the evolution of mold flux composition were investigated.The TiO_(2)accumulation and SiO_(2)consumption in mold flux under varying casting parameters was predicted.It was found that higher casting speeds accelerated compositional equilibrium,while the increase of mold flux consumption rates reduced TiO_(2)accumulation.The increase of pool depth resulted in slower consumption and accumulation rates of components like SiO_(2)and TiO_(2),prolonging the time to reach equilibrium.Additionally,the CaO-Al_(2)O_(3)-based flux suppressed the Ti-SiO_(2)reaction for the high-titanium steel continuous casting.However,the CaO-Al_(2)O_(3)-based flux should limited contents of Na_(2)O,MnO,and FeO to prevent additional TiO_(2)accumulation due to Ti-Na_(2)O,Ti-MnO,and Ti-FeO reactions.The model provided a reliable tool for understanding and optimizing the continuous casting process of high-titanium steels.展开更多
基金Project(2007CB613603)supported by the National Basic Research Program of China
文摘A novel method of roasting high-titanium slag with concentrated sulfuric acid was proposed to prepare titanium dioxide, and the roasting kinetics of titania was studied On the basis of roasting process. The effects of roasting temperature, particle size, and acid-to-ore mass ratio on the rate of roasting reaction were investigated. The results showed that the roasting reaction is fitted to a shrinking core model. The results of the kinetic experiment and SEM and EDAX analyses proved that the reaction rate of roasting high-titanium slag with concentrated sulfuric acid is controlled by the internal diffusion on the solid product layer. According to the Arrhenius expression, the apparent activation energy of the roasting reaction is 18.94 kJ/mol.
基金supported by Baoshan Iron and Steel Co.,Ltd. (Grant No.RH2100003354).
文摘Metallographic microscopy,scanning electron microscopy and TiN growth thermodynamic and kinetic equations were used to investigate the morphology,quantity,and size of TiN in the center of high-titanium high-strength steels under different solidification cooling rates.The results showed that TiN in the center of the experimental steels mainly existed in three forms:single,composite(Al2O3-TiN),and multi-particle aggregation.TiN began precipitating at around 1497℃(solidification fraction of 0.74).From the end of melting to solidification for 180 s,the cooling rates in the center of the experimental steels for furnace cooling,air cooling,refractory mold cooling,and cast iron mold cooling tended to stabilize at 0.17,0.93,1.65,and 2.15℃/s,respectively.The size of TiN in the center of the experimental steel cooled using furnace cooling was mainly concentrated in the 5-15 pm range.In contrast,the size of TiN in the center of the experimental steels cooled using air cooling,refractory mold cooling,and cast iron mold cooling were mainly concentrated in the 1-5 pm range.In addition,their density of TiN in the center of the experimental steels is signif-icantly higher than that of the furnace-cooled experimental steel.Thermodynamic and kinetic precipitation models of TiN established predicted the growth size of TiN in a high-titanium high-strength steel when the solidification cooling rates are not below 0.93℃/s.
基金support from the National Key R&D Program(Grant No.2023YFB3709900)the National Natural Science Foundation of China(Grant No.U22A20171)+1 种基金China Baowu Low Carbon Metallurgy Innovation Foundation(Grant No.BWLCF202315)the High Steel Center(HSC)at North China University of Technology and University of Science and Technology Beijing,China.
文摘Continuous casting of high-titanium steels face significant challenges due to steel-flux reactions,which will cause rapid compositional deviations and impair operational stability.A kinetic model to predict real-time mold flux composition evolution by integrating multicomponent mixed-transport-control theory with thermodynamics computing platform was developed in the current study.The model employed a cyclic time-step algorithm to compute thermodynamic equilibrium in reaction layer,mass transfer flux between reaction and bulk layers,and composition updates in reaction and bulk layers.The accuracy of the model was validated by plant trial data.The effect of casting parameters and initial compositions on the evolution of mold flux composition were investigated.The TiO_(2)accumulation and SiO_(2)consumption in mold flux under varying casting parameters was predicted.It was found that higher casting speeds accelerated compositional equilibrium,while the increase of mold flux consumption rates reduced TiO_(2)accumulation.The increase of pool depth resulted in slower consumption and accumulation rates of components like SiO_(2)and TiO_(2),prolonging the time to reach equilibrium.Additionally,the CaO-Al_(2)O_(3)-based flux suppressed the Ti-SiO_(2)reaction for the high-titanium steel continuous casting.However,the CaO-Al_(2)O_(3)-based flux should limited contents of Na_(2)O,MnO,and FeO to prevent additional TiO_(2)accumulation due to Ti-Na_(2)O,Ti-MnO,and Ti-FeO reactions.The model provided a reliable tool for understanding and optimizing the continuous casting process of high-titanium steels.
