Influence Of Ladle Shroud On Fine Gas Bubble Formation And Characteristics Of Fluid Flow In Tundish

With the improvement of steel quality demand, the non-metallic inclusions in liquid steel should satisfy much higher requirements. But the inclusions size of 5-20μm in the liquid steel because of its small buoyancy, is hard to removal within the scope of the natural rhythm. The method of using fine gas bubbles to removal small inclusions in liquid steel is worthy to study. At present, the field of metallurgy is not clear of small bubbles formed mechanism in the ladle nozzle, and the best parameters obtained through water model experiment of control fine gas bubbles in ladle shroud is to blowing in small and small aperture,although this method can get fine gas bubbles in the tundish, but a small number of bubbles, so can’t get better removal of micro inclusions.In this case, the in-depth study of the formation mechanism of fine gas bubbles in the ladle shroud, which has important theoretical significance and application value.In view of the above problems, this paper though Reference chemical field’s study on fine gas bubbles formation mechanism in turbulence liquid,and use it to investigate fine gas bubbles formation in ladle shroud. And on this basis, the design of a new type ladle shroud. The basic structure is composed of upper part of a broken zone, the lower part is a Venturi-tube. Through the method of physical simulation and numerical simulation, studies the fine gas bubble formation in a new ladle shroud’s broken zone. By the way of contrast, comparison of the new ladle shroud and the traditional ladle shroud’s flow characteristics and dispersion ability of liquid steel in tundish.Though the study of fine gas bubble formation mechanism in ladle shroud,the fine gas bubble formation in ladle shroud can be divided into two process: bubble formation in the gas hole.and then bubble break and coalescence,the finally fine gas bubble formation. The bubble breakup can promote the formation of fine gas bubbles, bubble coalescence increases size. Bubble break-up in turbulent liquid need two condition: First, the bubble has broken more than the required turbulent kinetic energy, the second is a certain bubble residence time in the turbulent region. Traditional ladle shroud have a high turbulent kinetic energy, but the bubble residence time is very short(about0.02-0.04s), so bubbles can’t break-up. Avoid the bubbles coalescence should avoid larger size of the bubble generation.Bubble refinement characteristics in ladle shroud experimental results show that in the new ladle shroud when the blowing amount of 1.5L / min, the bubble cycle time is about 0.4s.At this point, most of the bubble size in the middle of the package is less than 0.3mm, the number of fine gas bubbles formed under this condition is more than previous studies, Compare the optimal amount of blowing 0.08 L / min,is more than 18 times.whatever the liquid level rises in the middle of the package or packages under the same intermediate level, the use of new ladle shroud can extend the response time and the residence time, within the packet flow model more reasonable, and thus more conducive to remove floating inclusions to ensure the quality of liquid steel.