INVESTIGATION OF INCLUSION REMOVAL PROCESS IN TUNDISH STEEL MAKING PROCESS

Abstract

Molten steel contain the non-metallic inclusions that are harmful to their qualities in most cases, and all possible means are used to limit the number of inclusions. Among these means, the tundish is the last device in continuous production of slabs/billets before the molten steel reaches the mold, where they get solidified. Hence any inclusion left in the tundish and passing through its outlet will enter the mold spoiling the quality of the slabs/billets coming out of the mold. The inclusions present in the tundish may be removed by altering the flow configuration in the tundish so that inclusions get the tendency to float out at the top slag layer where they are trapped. Thus tundish, which was considered as a simple buffer or metal distributor between the ladle and the continuous casting machine, became an important metallurgical reactor for a clean steel production. Some researchers investigated the steel cleanliness in tundish through industrial trials. Since the operating condition of steel industries hint for serious problems and are expensive also, numerical simulations with industrial conditions are now mostly being used. For this purpose, during numerical simulation, various types of flow control devices, such as dam, weir, turbulence inhibitor and stopper have been developed in recent decades. In the present study the Reynolds-averaged Navier—Stokes equations have been numerically solved to obtain a steady, three dimensional velocity fields inside the single-strand tundish using the standard k-s model of turbulence. These steady flow fields so obtained are then used to predict the better mixing parameter inside the tundish which gives optimum position of the dam and its height. The removal of inclusions from molten steel is predicted by solving the inclusion transport equation. The investigation has been performed on the bare tundish with varying slope of the tundish walls. The effects of height and position of dams, weir and dam arrangement in the tundish and size of the inclusion particles on percentage inclusion removal were also investigated. To simulate the chaotic effect of the turbulent eddies on the particle path; a discrete random walk model was applied during inclusion trajectory calculations.