KINETICS OF DESULPHURIZATION IN PERMANENT CONTACT OF SLAG AND STEEL

The curve of % S vs reaction time is described quantitatively based on the electrochemical model directly deduced from the principle of electrochemistry as well as the given method for calculating the initial oxygen potential along slag/steel interface.The calculated data is in good agreement with the experimental results. During desulphurization,both L_s~* and L_s,the sulphur partition along the interface and that in the bulk,go up in association with the descending of oxygen potential along interface. The plot of L_s~* against reaction time follows a parabolic curve,while that of L_s is of hyperbola type.Correspondingly,on curves of driving force parameter vs reaction tone,either calculated or experimental,a hump occurs.

A boundary layer model for capture of inclusions by steel-slag interface in a turbulent flow

A boundary layer model was developed to predict the capture of inclusions by steel-slag interface in a turbulent fluid flow,which is based on the detailed analysis of inclusion trajectories.The effective boundary layer for inclusion removal was proposed by a statistical method.It is noticed that the capture of inclusions by steel-slag interface is not only dependent on the diameter of inclusions but also related to the local turbulent conditions.In high turbulent flow fields,the transport of inclusions is mainly dominated by the turbulent flow,and thus,the effective boundary layer thickness is mainly affected by the level of turbulent kinetic energy and is almost independent of the inclusion diameter.The inertia of inclusions gradually takes over the stochastic effect of turbulent flow,and the effect of inclusion diameter on effective boundary layer thickness becomes more noticeable with the decrease in the level of turbulent kinetic energy.Besides,the effective boundary layer thickness is more susceptible to the inclusion diameter for larger inclusions due to its greater inertia under the same turbulent condition while it principally depends on the level of turbulent kinetic energy for smaller inclusions.As the characteristic velocity increases,the time for inclusions transport and interaction with steel-slag interface decreases,and thus,the effective boundary layer thickness decreases.Moreover,the graphical user interface was developed by using the cubic spline interpolation for ease of coupling the current boundary layer model with the macro-scale model of a turbulent fluid flow in the metallurgical vessel.

Numerical Analysis of Fluctuation Behavior of Steel/Slag Interface in Continuous Casting Mold with Static Magnetic Field

Utilizing ANSYS CFX commercial software and volume fraction of fluid （VOF） model, fluctuation behav- ior of steel/slag interface was numerically simulated in continuous casting mold with static magnetic field, and the influence of metal jet characteristics on the behavior of steel/slag interface was investigated. The results indicated that the behavior of steel/slag interface is similar at different process parameters, which is closely related to the characteristic of the flow field. The steel/slag interface has an obvious trough characteristic, which can be divided in- to three zones： frontal valley zone, back valley zone and horizontal zone~ as the magnetic flux density increases, the fluctuation of liquid level increases firstly and then decreases, and a reasonable magnetic flux density can make steel/ slag interface obtain a relatively flat interface, which can prevent slag from being entrapped into liquid steel. For a thin slab continuous casting process, when the casting speed is 4 m/min, a reasonable magnetic flux density is about 0.5 T, and the interfacial fluctuation is weaker. No matter the position of magnetic field is horizontal or vertical, for different operating parameters, there is a corresponding reasonable magnetic field position where the steel/slag inter- face fluctuation can be properly controlled and slag entrapment can be prevented.

Interfacial Fluctuation Behavior of Steel/Slag in Medium-Thin Slab Continuous Casting Mold With Argon Gas Injection

The flow field of molten steel and the interfacial behaviour between molten steel and liquid slag layer in medium-thin slab continuous casting mold with argon gas injection were studied by numerical simulation, in which the effects of nozzle submergence depth and port angle, casting speed, and argon gas flow rate on the flow and the level fluctuation of molten steel were considered. The results show that the molten steel is jetted from the submerged en- try nozzle （SEN） with three ports into the mold and forms three recirculation zones including one upper recireulation zone and two lower recirculation zones. Argon gas injection results in a secondary vortex flow in the upper zone near the nozzle. For a given casting speed and argon gas flow rate, increasing the side port angle and submergence depth of nozzle can effectively restrain the steel/slag interracial fluctuation. Increasing the casting speed would prick up the level fluctuation. For a fixed casting speed, argon gas flow rate has a critical value, the interracial fluctuation with argon gas injection are stronger than the case without argon gas injection when the argon gas flow rate is less than the critical value, but when the argon gas flow rate exceeds the critical value, the level fluctuation is calmer than that without argon gas injection.

Simulation research on oxygen mass transfer between steel and slag in IF steel refining process

The effects of oxidizing slag on oxygen mass transfer and inclusions in different stages of IF(interstitial-free)steel refining were investigated by several heat simulation experiments.The results of the experiments showed that the oxidizability of slag changed considerably during different refining stages.Keeping the content of FeO in the slag within 1 wt.%would narrow the difference of slag oxidizability,stabilize the content of[Al]s in the steel,avoid secondary oxidation of molten steel by the slag,and reduce the inclusions.When the mass transfer of FeO in the slag phase was a limiting step,the secondary oxidation reaction occurred at the steel–slag interface;when the diffusion of oxygen in the molten steel was a limiting step,the secondary oxidation reaction took place inside the molten steel.The oxygen transfer rate was affected by the mass transfer coefficient of oxygen.For every 0.0001m/s increase in mass transfer coefficient,the oxygen transfer rate increased by about 2.2×10^-6 min^-1.By changing the mass transfer coefficient,the oxygen transfer rate of the slag to the molten steel can be controlled.