Model Study Of Non-metallic Inclusion Removal Through Steel-slag Interface Micro-process

Inclusions in steel will destroy the uniformity of the steel structure,and most inclusions are harmful.Removal of inclusions is one of the main tasks of steelmaking.A series of micro-models were established for the micro-processes of solid and liquid inclusions' floating in molten steel,interaction with the interface,and dissolution and removal in the slag.The following conclusions were obtained:Improved the inclusions behavior model of crossing the interface which is based on force analysis.The model considers the dissolution and settlement of the inclusions;it predicts the settling conditions and dissolution process of the inclusions;and uses the model to analyze the entire physical and chemical process of inclusions on a unified timeline and concludes that the movement time of the inclusion is extremely short relative to the dissolution process;for small-sized inclusions,the process of physically crossing the interface is controlling step;for large-sized inclusions,the dissolution radius during the dynamic movement decreases by only 2.5%,and eventually disappears by static dissolution on the upper side of the interface.A CFD model of solid inclusions crossing the steel-slag interface was established,and the simulation of the motion behavior of solid inclusions in the steel-slag two-phase was achieved with high accuracy and verified by water model experiments.The behavior of floating in the molten steel and crossing the steel-slag interface are simulated and the results reveal the mechanism and rules of the inclusion removal process;under the simulated physical properties,inclusions with a radius of 10-100?m meet the Stokes floating while the 1000?m inclusions'floating speed is only 1/10 of the Stokes speed;the critical size of whether an inclusion can pass through the interface should exist,and the probability of large-sized inclusions passing through the interface is greater.The time during which the inclusion does not contact the interface is very short,and will eventually settle at the steel-slag interface;the three-phase physical parameters have different degrees of influence on the interface movement behavior of the solid inclusions.The density of the inclusions and the wetting angle of the slag phase have a significant effect on the location of the inclusion and the shape of the interface.Slag viscosity and steel-slag interfacial tension coefficient have little effect.A three-phase CFD model for the movement of liquid inclusions in molten steel and slag phases was established and verified by water model experiments.The model was used to simulate the inclusions floating in molten steel and reaching the steel-slag interface and the interface interaction.In the simulated three-phase system,the larger the size of the liquid inclusions,the easier it is to deform or even break up when floating in the molten steel;the movement mode of the liquid inclusions near the interface is:slow down near the interface-accelerated by the interface-attached to the interface;the interfacial tension coefficient between the three phases of liquid inclusions-steel-slag has a significant effect on the shape of the inclusions staying at the interface.The relationship between the tension coefficients of the three-phase system should be:aIM>aMS>?IS.A model for collision and encapsulation of solid-liquid two-phase inclusions when floating in molten steel is established;when the solid and liquid inclusions are floating,the two flow fields interact to keep the inclusions away from each other;when solid and liquid inclusions are close enough,wetting and encapsulation will occur,and the wetting process takes about 10ms time.When the combined phase inclusions float up,the liquid inclusions stick to the tail of the solid inclusions will be in a "pocket shape";the semi-wrapped shape should be the steady state when the composite phase inclusions floating up.