Melt flow, mixing and grade change studies in the continuous casting of steel

Fluid flow in the tundish and mold affects the cleanliness of the cast product by its influence on flotation of non-metallic inclusions in the tundish and by its effect on mixing between grades during a grade change operation. Water modeling, using tracers, is commonly used for studying the flow behavior in tundishes. The tracer used should not affect the flow patterns in the system. Therefore, a neutrally buoyant, inert tracer should be used. In this work the effect of using a non-neutrally buoyant tracer on the flow profiles and RTD was shown by means of water modeling and mathematical modeling. The effect of using different quantities of copper as tracer in RTD studies on molten steel in tundishes was also demonstrated.; Thermal effects play an important role in determining the flow profiles in an actual steel tundish. In this work a criterion was developed to incorporate these effects in a water model. The criterion was derived from the dimensionless Navier-Stokes equations and was tested for different operating conditions using numerical simulation and experiments on a water model of a tundish.; The low tundish grade change process was simulated using mathematical modeling. A model was developed for simulating the emptying and filling of the tundish. It was shown that while thermal effects may not be important in determining mixing in a tundish with no flow control devices, it may be necessary to include them while modeling mixing in a tundish with dams and weirs. The effect of different operating parameters on mixing in the tundish was studied. Based on the information obtained, it was shown that using a combination of filling rates while filling the tundish resulted in further reduction in the transition time. A tanks-in-series model was developed to simulate mixing in tundish.; Coupled mixing between tundish and mold observed during a low tundish operation was studied for the first time in this work. It was shown that it is important to include thermal effects while modeling mixing in the mold. The effect of various operating parameters on mixing was also studied.