Study on the influence of unsteady casting on the flow characteristics and behavior of liquid steel in tundish

Abstract

In this paper, the flow characteristics and behavior of liquid steel in a six-strand tundish under unsteady casting state are studied by means of the combination of numerical and physical simulation. The results show that there is no obvious change in the consistency of the flow response of each flow medium in the unsteady casting state, but the flow characteristics and behavior of the liquid steel in the tundish will be greatly affected. At the same time, the fluctuation of the liquid level is enhanced, and the wave height difference is inconsistent at different positions affected by the change of flow state, among which the fluctuation is the strongest at position 5. Compared with the normal casting state, the blocking flow can change the original flow state and path. The dead zone volume fraction is increased by 1–1.5 times, the average residence time of liquid steel is increased, and the removal rate of inclusions is increased by 2.22%, 2.65% and 3.40%, respectively. The flow behavior of liquid steel in the tundish changes when the casting speed is changed. When the casting speed of outlet1 is increased, the removal rate of inclusions decreased by 1.14% on average, and the dead zone volume fraction decreased by 4.3% under the physical simulation results. When the outlet3 casting speed is reduced or the casting speed of each strand is reduced, the removal rate of fine inclusions is improved, the removal rate of inclusions increases by 2.39% and 11.42% respectively, but the dead zone volume fraction increases and the overall fluidity of liquid steel becomes worse. In addition, variable casting speed increases the instability of steel surface, and the liquid surface flow rate is basically proportional to the casting speed. When the liquid surface velocity is greater than 0.1 m/s, the protection slag has the risk of being blown open and exposed. It often occurs near the inlet of ladle nozzle. At the same time, the fluid dead zone critical velocity of 0.008 m/s defined in this study can be used for velocity calibration of fluid dead zone, and its accuracy is mutually verified by numerical and physical simulations.