FLOTATION OF NON-METALLIC INCLUSIONS DURING PURGE OF LIQUID STEEL WITH ARGON

Abstract

The paper shows that in the process of pouring steel through the intermediate ladles of the MBRZ, inert gas blowing is used through blowing devices of various designs. It is highlighted that today the intermediate ladle is the last metallurgical container where it is possible to influence the quality of the finished product in the process of continuous pouring. It is found that in the intermediate ladle at the last stage of pouring it is possible to control such parameters as mass transfer, refining, which will ensure the stability of pouring, as well as improving the quality of the finished product by removing non-metallic inclusions of various sizes. It is indicative that the use of inert gas blowing will improve the characteristics of metal flows, reduce the number of stagnant zones and is a turbulence damper. The paper considers theoretical aspects of removing non-metallic inclusions using inert gas bubbles. The mechanism of the inert gas flotation process is presented, which consists of such stages as the approach of the bubble to the inclusion, the formation of a thin film of liquid metal between the inclusion and the bubble, the sliding of the inclusion on the surface of the bubble, drainage and rupture of the metal film with the formation of a stable contact of three phases, inclusion – bubble – molten steel, stabilization of the bubble – inclusion unit, flotation of the inclusion – bubble unit. A detailed analysis of the attachment of inclusions to argon bubbles is carried out. It is shown that first there is a thinning of the liquid metal film on the surface of the bubble to critical dimensions, at which the film is torn and the core of the contact of 3 phases is formed, with the formation of a critical wetting radius, and then there is a stretching of the contact line of three phases from the critical radius to a stable wetting perimeter. It was found that the mechanism of attachment of inclusions depends on the time parameters, which include the collision time, sliding time, drainage time, expansion time and induction time. Theoretical calculations have shown that the probability of attachment of inclusions to a gas bubble depends on the size of the latter. It is shown that the highest probability of attachment will be observed if the diameter of the bubbles is 1 and 3.25 mm. In order to confirm the theoretical calculations, physical modeling of hydrodynamic processes in the tundish during its purging with an inert gas was carried out. It was found that the maximum refining effect is achieved when using argon purging in combination with a reaction chamber.