Herein, the fluid mechanical aspects involving flow interactions between flows formed by the top impinging jet and bottom blowing bubbles in a combined blowing converter bath are focused on. The effects of different operation conditions on the flow field and the kinetic energy of the bath are investigated to examine different roles of the blowing operations with the help of numerical model. It is found that the stirring intensity in the region near the bath wall is decreased even though the flow is more active in the vicinity of the impact cavity when the top lance declines. For the combined blowing converter, the bottom blowing plumes normally dominate the bath flow. However, the bath stirring intensity is increased slightly when the bottom blowing flowrate is higher than a critical value (0.08 Nm3 min−1 t−1). In addition, the results of energy dissipation demonstrate that higher flowrate of bottom blowing causes more intensive interaction between flows formed by the top and the bottom blowing, which, in turn, causes more energy dissipation.

The role of thermal-driven buoyancy flow in the steady macro-solidification process of a continuous slab caster and its effect on the predicted flow and temperature distribution are discussed by combining the non-dimensional analysis and the predicted results obtained from a steady three-dimensional coupled fluid flow, heat transfer and macro-solidification model. Results show that the relative strength among the thermal-driven buoyancy flow, the forced flow caused by the SEN impinging jet and the fluid flow through the porous matrix of mushy-zone continuously changes. The strength of thermal-driven buoyancy flow in the mold and sub-mold zone of slab caster is dependent on the characteristic flow velocity, temperature difference and the porosity-permeability ratio relation. The convection flow caused by thermal buoyancy at liquidus temperature of steel can result in the occurrence of local turbulence. The obvious effect zone of the thermal buoyancy flow on the predicted flow and temperature is in the region where the forced flow has become inferior and the mushy porous flow does not play a dominant role.KEY WORDS: continuous slab caster; solidification; thermal-driven buoyancy flow; numerical simulation.liquid steel and solid steel is regarded as the constant value and Boussenisque's approximation is used to consider the thermal-driven buoyancy flow. 3) The low-Reynolds number k-e turbulent model of Lam and Bremhorst is utilized to consider the turbulent flow in the mold. Boundary ConditionsAll general initial and boundary conditions for simulation on a continuous slab caster have been noted in several references. 18,22) The specified coordinate and grid system for a given caster in the present study is shown in Fig. 1. The geometrical parameters and operating conditions of this caster are summarized in Table 1. The value of the Darcy coefficient is adopted in concert with the work of Seyedein et al. 18) and the values of various turbulent constants are assigned by the reference. 23)It is very difficult to determine the mold heat flux due to the existing gas gap between the mold and the shell. A simple local heat flux formulation obtained by the measurement of the mold water volume and water temperature difference between the inflow and the outflow of cooling water is employed, as given by: At the strand surface below the mold, the values of heat transfer flux from the strand surface to the environment are governed by combination of three heat-transfer mechanisms: conduction, convection and radiation. Therefore, it is very difficult to decide the combined heat-transfer coefficient and a trial and error study procedure is adopted, which can be simply outlined as follows: 1) the known spray cooling water volume obtained from the plant's database is inputted into the known empirical or semi-empirical formulations 24) to calculate the combined heat transfer coefficient in different segments of the caster; 2) the heat transfer coefficient is used as the boundary condition to obtain the calculated surface temperatu...

The current study focuses on the melting behavior of a scrap bar with low carbon content in hot metal which contains high carbon concentration by applying experiments and mathematical modelings. The experiments suggest that higher temperature is favorable for the melting of the bar and the melting rate of the bar is initially high while decreased to a relative stable level after 90 s in the current conditions. It can be found from the mathematical results that the bar temperature is increased near to bath temperature in about 20 s after it was immersed into the bath, and the temperature in the axis of the bar is not distributed evenly during the temperature increase stage. Moreover, the mathematical results shows that a bath circulation flow would be formed in the bath under the effects of temperature and carbon distribution during the melting process. The bath flow near the melting interface would influence the carbon concentration of the molten phase, in turn, affects the melting rate of the bar in the vertical direction. Both the experimental and mathematical results show that the melting rate in the upper part, which is in the upstream of the bath flow, is higher than that of the middle part, followed by the down part of the bar in the downstream of the flow, in which the carbon concentration is much lower than that of the bath. At this period, the main factor that dominate the bar melting is not the temperature but the carbon distribution at the melting interface after the bar temperature is increased to the bath temperature.

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