Study On Water Model For Bottom-blowing Argon Ladle With Immersed Cylinder

With the increase of demand for clean steel and high quality steel day by day,refining technology has attracted increasing attention. Stirring technology of bottomargon blowing in ladle is widely used in secondary refining because of advantages,such as its simple equipment, flexible operation, making components and temperaturewell-distributed, improving the reaction of deoxidation and desulfurization, removinginclusion and harmful gas effectively in steel, improving effect of steel refining, etc.But large flow rate of argon blowing will cause some problems, for example, sprays,reoxidation of liquid steel, slag entrainment, which inhibit the improvement ofrefining efficiency by increasing the flow rate of bottom gas blowing.In the paper, physical simulation system was established based on similaritytheory by using150ton ladle in a domestic plant as the prototype. By watersimulation experiment of bottom argon blowing in ladle with immersed cylinder, theeffect of immersed cylinder on the fluid flow characteristics, slag entrapment, thecritical gas flow rate of slag entrapment and mixing behavior of molten steel wasstudied. Meanwhile, the feasibility of enhancing stirring efficiency and shorteningrefining time of liquid steel by improving the critical gas flow rate of slag entrapmentusing the way of inserting a immersed cylinder into liquid steel to limit slagentrapment was discussed. The conclusions are as follows.(1) The flow field changes when immersed cylinder is inserted into ladle. In theprocess of gas-liquid flow rising, a portion of the fluid flow into the cylinder andsymmetrical circulation flow inform in the cylinder, meanwhile, a large circulationflow inform under the cylinder and a portion of the fluid flow upward near the ladlewall. With the increase of diameter and inserting depth of immersed cylinder, thecirculation flow were strengthened inside cylinder and weakened outside cylinder.(2) Increasing the flow rate of bottom blowing argon increase the rate of fluid onthe steel-slag interface and inertia force of fluid correspondingly that slag entrainmenthappens. The bigger the gas flow rate, the more dramatic the slag entrainmenthappens. Immersed cylinder can inhibit the occurrence of slag entrainment which canimprove the critical gas flow rate under which slag entrainment starts to happen.(3) The mixing time shortens with the increase of gas flow rate. However, whenthe gas increases to a certain extent, the degree of decrease of mixing time tends toslow. After dipping into the cylinder, the mixing time is prolonged obviously, and thedegree of increase of mixing time is larger under small gas flow rate than big one.(4) Increasing the diameter and inserting depth of immersed cylinder canenhance the critical gas flow rate of slag entrainment under which the molten steelobtain more stirring energy that the mixing time shorten. When the inserted depth islarger, the shortening of mixing time is not obvious.(5) Under experimental conditions, the critical gas flow rate of occurring slag entrainment without immersed cylinder is0.10m3·h-1under which the mixing time is41s and with immersed cylinder which diameter and inserting depth are130mm and90mm respectively is0.54m3·h-1under which the mixing time is22s which is theshortest one. Immersed cylinder can increase gas flow rate of bottom-blowing,enhance stirring effect and shorten refining time. Beside the gas flow rate ofbottom-blowing, mixing time are related to the diameter and inserted depth ofimmersed cylinder. In the most optimal conditions, the empirical formula of thestirring power density and the mixing time is obtained, t78.6exp(0.068).