Mathematical simulation of effects of flow control devices and buoyancy forces on molten steel flow and evolution of output temperatures in tundish

Abstract

The effects of flow control devices and buoyancy forces on the melt flow in a large tundish have been mathematically simulated using a k–ϵ turbulence model. Flow control devices included arrangements consisting of a pair of weirs and a pair of dams, a turbulence inhibitor and a pair of dams, and only a turbulence inhibitor. Buoyancy forces were simulated using step inputs of temperature and inputs of varying ladle stream temperature into the tundish. It was found that with inputs of hot steel, flow control devices improve performance by driving the melt upwards through the action of buoyancy forces. A bare tundish is less sensitive to buoyancy forces and shows greater thermal mixing than any other arrangement. Inputs of temperature steps promote higher temperature gradients of liquid steel inside the vessel than inputs of varying ladle stream temperatures. A turbulence inhibitor delays the thermal disturbance compared with a bare tundish or a tundish with a weir–dam arrangement. When using a turbulence inhibitor higher volume fractions of melt obey a plug like flow. The dimensionless quantity Gr/Re2, where Gr and Re are the Grash of and Reynolds number respectively, quantifies buoyancy forces: high values indicate that buoyancy forces have more effect than inertial forces on fluid flow. When Gr/Re2 <5, buoyancy forces have no noticeable influence on fluid flow.