SIMULATION OF SLAG SKULL FORMATION ON THE WALL OF CCM MOLD

The processes of formation of the skull and liquid film between the mold and surface of the billet effect on quality indicators and stability of the continuous casting of steel. A number of theoretical studies devoted to the forecast of skull thickness and the film of liquid slag are known. However, these studies do not take into account the mutual influence of formation processes of skull and film, as well as formation of shell thickness of the billet. In this connection, the paper presents a mathematical model of interrelated thermal processes developed by the authors in the system of layers “copper wall of crystallizer  – skull  – film of liquid slag – crust of ingot”. The model makes it possible to predict the dynamics of formation of the thickness of the ingot crust, slag skull and the layer of liquid slag along the height of the mold and the length of liquid friction portion in it, depending on casting speed, temperature of casting steel and melting of the slag, thickness of the slab and working layer of the copper wall. The adequacy of the model to the object is determined by such parameters, as surface temperature of the billet, thickness of the crust, specific heat flux in the mold and temperature of the working wall. An example of application of the developed model is shown, in which the effect of casting speed on length of the liquid friction portion in the mold is investigated. It was found that at speeds of 0.8; 1.0 and 1.2  m/min the slag layer is retained for 0.331; 0.415 and 0.498  m from the meniscus of the metal, respectively. At the same time, the thickness of the skull reaches a maximum value of 0.77  mm. Further formation of the preform occurs in the absence of lubrication in the mold. The possibility of using the developed model by technologists for selecting the chemical composition of casting powder, which provides the required length of the liquid slag section, is indicated by the designers when choosing the mold profile, taking into account the thickness of the skull, and, also for educational purposes.

continuous casting machine, mold, heat transfer, slag-forming mixture, slag skull, math model

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