Výzkum a vývoj rafinační technologie tavenin kovů s využitím numerického modelování

Abstract

The use of aluminium alloys in many industrial sectors is still increasing today. Due to its excellent properties, aluminium is widely used, for example, in construction, automotive industries etc. The increase in the use of aluminium is also accompanied by increasing demands for chemical and metallographic cleanliness of this metal. The presence of unwanted phases in the molten metal can cause changes in final castings properties, such as porosity, corrosion susceptibility etc. These phases are represented especially by harmful gases and non-metallic inclusions. Although significant progress has been made in the field of metallurgy in recent decades, great attention is still being paid to the optimization of metallurgical processes. The refining technology of aluminium melts, which uses a rotating submersible device for blowing inert gas, is not the exception. The refining intensity of this device is strongly dependent on the operating parameters, which include rotor speed, a distance of the rotor from the bottom of the ladle, number of breakwaters and rotor geometry. This thesis is focused on numerical modelling of aluminium melt refining technology in ANSYS Fluent program to describe and evaluate the character of turbulent flow in an aluminium refining reactor through the ANSYS Fluent program. In this work, a methodology for determining the degassing efficiency of aluminium when changing operating parameters was developed. Numerical simulations of the technology were based on the flow calculation through the turbulent SST k-ω model and the free surface behaviour calculation using a two-phase VOF model. The results of the turbulent and two-phase model provided a basic overview of the flow and associated processes in the volume of the model liquid. Attention was also focused on the risk of wear of the lining due to shear stresses acting on the ladle walls. The flow results were followed by calculations of the propagation of the tracer concentration using the Species model, the purpose of which was to describe the intensity, uniformity and pattern of mixing of the model liquid in the ladle when the boundary conditions changed. Based on the previous results, the cases where the oxygen concentration drop from the model liquid was calculated and the efficiency evaluated were identified. The calculated concentration curves showed good agreement with the concentration curves measured on the physical model.