Study On Fluid Flow And Slag Entrapment In A Wide Slab Continuous Casting Mold

Mold is known as the"heart"of continuous casting machine.According to statistics,80%of billet defects come from mold.The flow state of molten steel in mold is closely related to the quality of billet.With the increasing supply of iron and steel products and the development of continuous casting technology,people have higher and higher requirements on the quality of steel,so it is necessary to avoid inclusions into molten steel in the continuous casting process to ensure the purity of molten steel to achieve the best.In this thesis,a wide slab continuous casting mold with a section of 2040mm×200mm is taken as the research object.According to the similarity principle,a water model with a ratio of1:4 for model and prototype is established.The slag-rolling zone and non-slag-rolling zone were established to provide reference for the selection of wide slab continuous casting conditions.The critical pulling speed of slag coil with trapezoidal,elliptic,circular and-15°elliptic nozzle was studied.When the immersion depth is changed and other conditions remain unchanged,the critical tensile speed of the slag increases with the increase of the immersion depth.Under the same conditions,the critical pulling speed of slag is the highest.When the nozzle immersion depth is 40mm～50mm,the critical pull-speed of elliptic nozzle increases by about 0.05m/min and that of circular nozzle by about 0.04m/min for every 5mm increase.When the elliptic nozzle Angle changes from 0°to-15°,the critical tensile speed of the slag increases.When the kinemastic viscosity of silicone oil is 50×10^-6m²·s^-1and 100×10^-6m²·s^-1,the phenomenon of slagging does not occur when the immersion depth is greater than 40mm and 35mm,respectively.Gambit,ICEM CFD,Fluent and Tecplot software were used to simulate and calculate the flow field in three types of mold with trapezoidal,elliptic and circular openings,and the position of the vortex center of the upper reflux and the velocity of the center line of the free liquid surface in the mold were analyzed.The basic flow characteristics of molten steel in the mold are basically double circulation.The vortex center in the upper reflux region moves down when the drawing speed is kept constant and the immersion depth of the water inlet is increased.The vortex center in the upper reflux region moves down slightly when the immersion depth is kept constant and the drawing speed is increased.When the nozzle immersion depth is greater than 40mm,the upper circumfluence vortex center of the oval nozzle is the farthest from the free liquid surface of the mold,followed by the trapezoidal nozzle,and the circular nozzle is the nearest.The velocity of free surface decreases with the increase of immersion depth,and the velocity of trapezoidal orifice is round and oval at the same depth.At the same pulling speed,the free surface velocity of trapezoidal orifice is the highest,followed by elliptic and circular orifice.Dip depth 30mm～50mm,pull speed 0.3m/min～0.5m/min,use trapezoidal,oval and circular nozzle,the maximum free liquid surface speed is 1/4 of the width of the crystallizer.