Continuous casting of slab caster of Tata Steel has been simulated using a three dimensional mathematical model based on considerations of fluid flow, heat transfer and solidification for better understanding of the process. Liquid metal comes in the mould by bifurcated nozzle. The principal model equations are momentum and heat balances. In various zones, different standard boundary conditions have been used. In the mould region, Savage and Prichard expression for heat flux has been used. In the spray cooling zone, heat transfer coefficient for surface cooling of the slab has been calculated by knowing the water flow rate and nozzle configuration of plant. The turbulence in the molten metal has been modelled by the Realizable k-e model. CFD software (Fluent) has been used for the solution of equations to predict the velocities in the molten pool of the slab, temperature of the entire volume of the slab, heat transfer coefficient in the mould region, heat flux in the spray and radiation region and shell thickness. The variables studied are different casting speed.KEY WORDS: slab caster; turbulence; solidification; shell profile; CFD; radiation cooling; spray cooling; heat flux; heat transfer coefficient; mathematical modelling; steel casting; realizable k-epsilon model. ISIJ International, Vol. 47 (2007), No. 3, pp. 433-442 433 © 2007 ISIJ austenite-ferrite phase transformation, which is accompanied by a sizeable volume change should not occur. To meet the above criteria, after certain length of spray cooling, the strand is allowed to be radiant cooled. The dimensions of the caster are given in Table 1. The spray zone length has been sub divided into six regions for flexibility of cooling. The first is spray ring region (Zone 0) just after the mould and having only water flow. In the narrow face of the slab, the spray ring region (Zone 0 N&S) is also having only water flow. After this region, there is no forced cooling on the narrow face. After spray ring region other spray zones are named as 1A, 1B, Zone 2, Zone 3, Zone 4 and Zone 5 as mentioned in Table 1. Slab cast should be free from surfaces and internal cracks. For a given composition of steel, solidification in the slab casting will depend on fluid flow and heat transfer in different zones. In the mould region, the total heat transfer can be easily obtained by knowing difference of temperature between the inlet and the outlet of water passing through mould cooling jacket and its flow rate. Theoretically, it is difficult to get the heat transfer along the mould length because of air gap formation between mould and slab, resistance of heat flow due to shell formation, mould plate, water-copper plate, thermal contraction of slab and mould plate, bulging due to liquid height pressure.2-6) Singh and Blazek 7) have experimentally measured the heat transfer profile along the mould length by using a bench scale casting facility. Mould was stationary, unlike the actual caster. They have shown the effect of carbon content, casting speeds, pouring practice, mou...

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An analysis of mould, spray and radiation zones of a continuous billet caster has been done by a three‐dimensional turbulent fluid flow and heat transfer mathematical model. The aim was to reduce crack susceptibility of the billets and enhance productivity of the billet caster. Enthalpy‐porosity technique is used for the solidification. Turbulence is modelled by a realizable k‐ε model. The three‐dimensional mesh of the billet is generated by Gambit software, and Fluent software is used for the solution of equations. In various zones, different standard boundary conditions are applied. Enhanced wall treatment is used for the turbulence near the wall. In the mould region, Savage and Prichard expression for heat flux is applied. In the spray cooling zone, the heat transfer coefficient for surface cooling of the billet is calculated by knowing the water flow rate and the nozzle configuration of the plant. The model predicts the velocities in the molten pool of a billet, the temperature in the entire volume of billet, the heat transfer coefficient in the mould region, the heat flux in the cooling zone and radiation cooling zone, and the shell thickness at various zones. The model forecasts that the billet surface temperature up to the cutting region is above the austenite‐ferrite transformation temperature (which is accompanied by large volume change). The model predicts a temperature difference of maximum 700 K between the centre and surface of the billet. The entire solidification takes place at 11.0 m length at 3.0 m/min. For the same casting arrangement, increasing the casting speed up to 4.0 m/min has been explored. Based on the simulation results, recommendations to alter the spray water flow rate and spray nozzle diameter are presented to avoid a sudden change of temperature.

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A two-dimensional heat and fluid flow model was used to simulate the plasma arc furnace, where the flow is governed by the steady state incompressible Navier-Stokes equations. The flow has been taken as turbulent and the standard k-epsilon model was used to simulate the turbulence in the flow. The coupled non-linear differential equations were solved with suitable boundary conditions and temperature dependent plasma properties at atmospheric pressure by employing an efficient finite volume method. The calculations and heat transfer to various parts of the furnace were calculated for argon, nitrogen and hydrogen plasmas. The voltage-current characteristic for the different types of plasma and the effect of other process parameters on heat transfer are discussed.