Visualized Study Of Bubble Behavior In The Swirling Flow Uphill Teeming Process

Uphill teeming process is one of the common methods which are used in steel ingot production.And the flow control and inclusion level control in it are hard to achieve,which hinder the development of the process.Referring to the swirling continuous casting technology,swirling flow technology has been used into uphill teeming process.Results of model experiment show that it can control the flow in the runner and the mold.On the other hand,the bubble treatment is well applied to removing the inclusions in the refining process of steel.In this study,a new process is proposed that removing inclusion by using bubble treatment in the runner in the swirling flow uphill teeming process,and a water model experiment research on the bubble movement characteristics is conducted with two high speed video cameras that set up orthogonally.The gas blowing experiments of the central runner and upper runners under different swirling flows are carried out.There are three contents that are studied in this paper,and the contents include the influence of swirl blade placed in the central runner on the pouring time,the bubble behavior(bubble trajectory,critical height of bubble floating up,bubble velocity,bubble moving distance)under different swirling flows in the central runner and the bubble behavior(vortex,bubble trajectory,bubble velocity,bubble breakup)of different swirls in the upper runner.The following conclusions are drawn follows:(1)The pouring time decreases when the swirl blade is placed,and decreases gradually with the increase of the blade twist angle.(2)The bubbles oscillate and float up in the central runner when there is no swirling flow and rotate circumferentially to different degrees and float up when there is swirling flow.The bubbles rotate circumferentially and gather to the runner central only when the angle of swirl blade is larger than 120°.With the increase of twist angle and bubble size,bubbles rotate and move towards the runner axis center faster and faster.There is a critical height of bubbles floating up that blown out by different capillaries in different swirls.The height increases with the increase of the twist angle and decreases with the increase of the capillary diameter.The trajectory,velocity,moving distance and total surface area of bubble moving distance are analyzed synthetically.The 1200 blade is the best one for removing inclusions,followed by 180°blade.When the blade angle is 120°,the motion state of bubbles blown out by 0.5mm capillary tube is most suitable for inclusion removal and 1.0mm is the next,0.1mm is the minimum.(3)When there is no blade in the upper runner,the gas-liquid fluid directly enters the casting mold.After placing the blade,the main flow from the horizontal runner impacts the blade and then a part of the gas-liquid fluid will form a vortex(only blade angle more than 60°)and the rest gas-liquid fluid will enter the casting mold directly.The height of the center of the vortex will decrease with the increase of the twist angle of the blade.For the gas-liquid fluid that enter the casting mold directly,when there is no blade,the bubbles move upward along the inner side of the upper runner;when there is blade,the bubbles circumferential rotation is enhanced with the increase of the twist angle of the blade.It is not certain that if the bubbles converge toward the center.The place where the bubbles start to rotate is the height that the main flow from the horizontal runner impacting the blade.The gas-liquid flow is the fastest under the condition of no swirl blade.When the swirl blade exists,the gas-liquid flow(average resultant velocity)slows down,and it slows down gradually with the increase of twist angle.Due to the influence of shear flow occurring at the ending of the horizontal runner and the swirl blade,bubbles will break up when passing through the upper runner.