Physical Modeling Research Of Electromagnetic Brake On Bubble Distribution And Surface Fluctuation In Slab Mold

In order to prevent nozzle clogging and promote non-metallic inclusion floating in the mold, SEN blowing argon technology has been widely applied to the field of continuous casting production. Argon bubble with hot steel went into the mold, if not properly controlled, the bubble in the upper vortex may cause entrapment to form inclusion defects; the bubble in the lower vortex impacted to the depth of the mold, were captured by solidified shell, leading to subsurface porosity defects. In addition, with the development of high efficient continuous casting, SEN out flow velocity increased. If not properly controlled, it would cause hot steel impacting the solidified shell intensely, increasing the risk of pulling leakage. At the same time, entrainment of bubble and non-metallic inclusion in hot steel were also difficult to float to remove, as impact depth of stream increased. To stabilize high efficient continuous casting process, electromagnetic brake has been widely applied in terms of control flow field in the mold.According to similarity theory, Pb-Sn-Bi low melting point alloy and argon were employed to simulate the hot steel and argon gas two-phase flow. A physical model was developed to study bubble distribution characteristics and surface fluctuation behavior in consideration of the couple effects of EMBr and argon injection in a slab mold with high casting speed. The effects of different magnetic flux density, nozzle blowing volume and casting speed and other experimental conditions on bubble distribution and surface fluctuation were investigated.The self-made resistance probe was applied to study bubble distribution characteristic in the mold in different process parameter with and without EMBr in this dissertation. The experimental results showed that when EMBr was imposed, the whole bubble distribution in the mold changed and the number of bubble changed. After the imposition of EMBr, the impact depth of metal stream was effectively suppressed, the floating up rate of bubble increased, the number of bubble was increased at the1/4width of the mold, and the number of bubble near the narrow face of the mold was decreased, thereby the possibility of capture was reduced by narrow face of the mold. In addition, the total number of large bubble at15mm under the surface in the mold was decreased with EMBr, thereby the possibility of entrapment caused by large bubble burst was reduced.The laser liquid level apparatus was applied to study instantaneous fluctuation at the1/4width of the mold in this dissertation, and then obtained by processing the average fluctuation to quantitatively analyze the effects of a variety of processing conditions on surface fluctuation. The experimental results showed that when the argon gas was injected in the mold, with the increasing of magnetic flux density, the surface average fluctuation of1/4width of the mold increased. There was an optimal magnetic flux density for depressing the surface fluctuation when the argon gas was injected in the mold. When magnetic flux density was0.28T, the surface fluctuation of the mold was the best.