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A two-dimensional heat transfer model was developed for the secondary cooling system during beam blank continuous casting. The finite element method was used to calculate the heat transfer. Accurate cooling boundary conditions in the secondary cooling zone are involved, including spray water cooling, water evaporation cooling, radiation cooling and roll contact cooling in the casting direction and non-uniform distribution of spray water flow density in the cross-section. The causes of longitudinal crack at the fillet during Q235 steel continuous casting were analysed on the basis of the simulation of the developed model, and then the spray water flow and the transverse nozzle layout were optimised. Practical results show that the surface quality of the beam blank improved after optimisations. Numerical results from the present model were validated using previous experimental measurements, which show good agreement.

Ultrathick continuous slab casting is a growing technology, especially in developing countries due to the vast market demand of thick rolled plate. The structure of the submerged entry nozzle is regarded as the crucial factor to determine flow related phenomena in the mould. This article conducts a 0·55 scale water model and a three-dimensional numerical model to investigate the influences of submerged entry nozzle on flow behaviour, temperature field and solidified shell distribution in a 420 mm ultrathick slab mould. Physical and numerical finite volume methods with K–ϵ turbulence model simulations verify that the flow pattern in ultrathick mould is similar with that in conventional slab mould. The diffuse type nozzle fails to increase the surface velocity while easily causing slag entrainment. The four-spout nozzle gives a detrimental effect on shell distribution. The tunnel bottom nozzle is optimal, because it shows a lively surface behaviour and a favourable heat transfer between mould flux and surfa...

The technology of nail shooting was improved and used to study the transverse shape of the solidified shell during steel continuous casting. Three locations across the slab width (1/2, 1/4 and 1/8) were measured by nail shooting and which indicated a larger solidification coefficient and longer liquid core in the slab at higher casting speeds. The solidified shell across the slab width direction was non-uniform due to uneven secondary spray cooling. The point of final solidification at locations 1/8 and 1/4 was much longer than the position between the slab centre and location 1/4, leading to a long solidification end of >2 m, which is poor for the application of dynamic soft reduction. A mathematical model was developed to simulate the growth of the solidified shell and which was in good agreement with the measurements measured by nail shooting. Based on the measurements and simulations, the water spray pattern was improved, making the solidified shell more uniform. Dynamic soft reduction was the...

Based on a basic water cooling model, a novel model with closed feedback loop was developed for online temperature control system (OTCS) to control the strand surface temperature online during steel continuous casting process. The OTCS considered the temperature delay to the casting speed and water flowrate and combined the feedback control model with feed forward control model for the control of secondary cooling water. The online feed forward control with the temperature of molten steel in the tundish and the temperature of cooling water was also considered. A fine adjusting temperature region and an optimal temperature region were applied to the OTCS to avoid big temperature fluctuation during control process and to shorten the adjusting time. A single point OTCS was applied to a slab continuous caster, showing that the slab surface temperature was well stabilised at the target temperature under the control of the OTCS in continuous casting process. During tundish change or big variation of cas...

A water modelling experiment was conducted to study the fluid flow in a continuous slab casting mould with solidified shell. The level fluctuation, residence time distribution and velocity of free surface have been varied in the water model to study the differences of flow behaviour between the mould with a shell and without a shell. The results show that the mould with a solidified shell has higher level fluctuations, higher surface velocities and worse liquid slag distribution. The tapering of the shell in the mould enabled downward flow to facilitate more fluid being ‘pushed’ into the upper recirculation zone, yielding higher velocities and greater turbulence at the top surface. With the consideration of the solidified shell, the fluid flow in the mould is more representative of real casters, and the physical modelling results will be more accurate and reliable. It may cause unrealistic lower surface level fluctuations and surface velocities in the water model when the solidified shell is neglected in ...

With the increased use of smelting reduction processes, it is necessary to study some important properties of smelting reduction slags, which are different from those through the BF route. In this research, chemical reagents are utilised to simulate the real slag, the activities of FeO in slag and the viscosities of FeO–CaO–SiO2–Al2O3–MgO–TiO2–V2O5 slag system were measured under different temperatures, and the viscosity diagram and isoactivity curves of above slag system were obtained. The effect of different factors on the viscosity and activity of the slag was analysed respectively.