The high content of aluminum in the steel reacts with the CaO-Si2O-based mold fluxes, resulting in deterioration of the mold slag physical and chemical properties, which cannot be applied to the continuous casting molten slag casting process of high-Mn high-Al steel Herein, the thermodynamic and structural properties of low-reactivity CaO-Al2O3-based mold fluxes were investigated. The thermodynamic properties were studied based on the first principles of quantum mechanics. The results show that the formation of stable structures of B-O and O-B-O in the mold fluxes was beneficial to reduce the probability of structural interconnection, degree of polymerization, and viscosity of the molten slag. The increase in the ratio of CaO/Al2O3 = 0.88–2 led to an increase in the O2− concentration. O2− entered the [AlO4] structure to form a stable structure of [AlO6] and [AlO5], wherein [AlO6] was more stable than [AlO5], reducing the degree of polymerization of the network structure. When cosolvent content B2O3 = 2%–10%, a simple layered structure of [BO3] was formed, and the particle migration resistance, break temperature, and viscous activation energy of the mold fluxes were reduced, while the corrected optical basicity of mold fluxes was gradually increased.
An oxygen lance represents a commonly used piece of equipment in converter steelmaking. Its jet characteristics and the interaction of these jets with the molten pool will directly affect the smelting effect and blowing time. This work investigates the oxygen lance of a 260 t converter in a steel plant. Through numerical simulations and physical experiments, the influence of the operating pressure, ambient temperature, top-blowing flow, lance position, and other operating parameters on the jet flow characteristics of the oxygen lance is studied. Furthermore, the oxygen lance interaction with the molten pool is analyzed. The results show that the operating pressure has little effect on the fusion distance of the jet; however, its size determines the impact force of the jet on the molten pool. In addition, the high-temperature environment causes the density of the jet fluid to decrease, the jet attenuation speed to decrease, the jet fusion speed to increase, and the degree of fusion to attenuate. Furthermore, the spray volume of the furnace mouth continues to increase upon increasing the top-blowing flow; by contrast, the spray volume first increases and then decreases as the gun position increases. The maximum spray volume of the furnace mouth occurs at the 35-de gun position; the diameter of the impact pit varies with the gun position. As the top-blowing flow increases, the depth of the impact pit increases with the decrease in the gun position and the increase in the top-blowing flow. The mixing time gradually reduces with the increase in the top-blowing flow and the decrease in the gun position.
There are two problems to be solved in the numerical simulation of the top blown oxygen vacuum refining process. (1) The two-equation turbulence models underpredict the turbulence mixing shear process for high-temperature gradient jet flows. (2) The high compressibility of the jet in a low vacuum environment. In this study, the SST k-ω turbulence model is modified by the composite function of the compressibility factor and the total temperature gradient. Based on the experimental model of the Kotani vacuum jet, the modified turbulence model was used to simulate the supersonic jet behavior of oxygen lance at different ambient temperatures. The reliability of the model is verified by the semi-empirical formula of Ito and Muchi. The simulation results show that the entrainment rate is an important inducing factor. The potential core length and the supersonic core length at the temperature of 1800 K are 2.5 times and 2.0 times that at the temperature of 285 K, respectively. Besides, based on the ejection model established by Ricou and Spalding, the calculation formula of turbulence entrainment rate at different ambient temperatures is obtained. This research work will benefit greatly to the supersonic jet behavior in Vacuum Refining.
Oxygen lance is the key piece of equipment for iron and steel smelting. During the entire steelmaking process, the performance of the oxygen lance determines the occurrence of decarburization, slagging, heating, and splashing. In this paper, the influence of structural and process parameters on converter steelmaking is studied using a six-nozzle staggered oxygen lance and the traditional six-nozzle oxygen lance by performing jet tests, numerical simulation, and water model experiments. The research results show that, compared with the traditional oxygen lance nozzle, a stepwise fusion of the jet streams of the staggered oxygen lance nozzles occurs, which increases the fusion distance to varying degrees, reduces the amount of splash at the furnace mouth, and increases the effective impact area. For the six-nozzle staggered oxygen lance nozzle, the most ideal structure and maximum performance are obtained at an inner nozzle angle of 14° with a flow ratio of 55% and an outer nozzle angle of 18° with a flow ratio of 45%. The results show that the fusion distance of the inner nozzle and outer nozzle is 2.1 and 2.25 m, respectively; compared to the traditional oxygen lance nozzle, the splash amount of 0.19 g at the furnace mouth is reduced to only 16%, while the effective impact area has doubled to reach a value of 0.47 m2. With the increase in the oxygen lance position, the effective impact area of the jet of the oxygen lance nozzle on the molten pool first increases and then decreases, and the best position of the traditional and staggered oxygen lance nozzles is determined as 30.0 and 35.0–37.5 de, respectively.
For this article, the bottom regiments distribution is designed to investigate the instantaneous kinetic energy of molten pool with the help of numerical simulation. The results indicate that the time required for kinetic energy to reach the stable state is affected by the angle among regiments. When the blowing gas flowrate is 720 Nm 3 •h − 1 , the shorter equilibrium time is 66 s with the angle of 15°. Meanwhile, the higher kinetic energy of 2 915 J has been discovered as the outer regiments kept at a pitch circle diameter ratio of 0.5, which reflects the preferable internal dynamic conditions of liquid steel. While the molten pool can get enough stirring force, and the outer cluster should not be arranged closely to the furnace wall to avoid unnecessary energy dissipation. Besides, the weak stirring zones inside the bath can be reduced by the elevation of blowing gas intensity, and the proportions of the proper scheme are 0.84, 0.74, 0.69, and 0.67 under four diverse operation conditions, respectively.
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