Concern for the environment and rational management of resources requires the development of recoverable methods of obtaining metallic materials. This also applies to the production of aluminium and its alloys. The quality requirements of the market drive aluminium producers to use effective refining methods, and one of the most commonly used is blowing an inert gas into liquid aluminium via a rotating impeller. The efficiency and cost of this treatment depends largely on the application of the correct ratios between the basic parameters of the process, which are the flow rate of the inert gas, the speed of the rotor and the duration of the process. Determining these ratios in production conditions is expensive and difficult. This article presents the results of research aimed at determining the optimal ratio of the inert gas flow rate to the rotary impeller speed, using physical modeling techniques for the rotor as used in industrial conditions. The tests were carried out for rotary impeller speeds from 150 to 550 rpm and gas flow rates of 12, 17 and 22 dm3/min. The research was carried out on a 1:1 scale physical model, and the results, in the form of visualization of the degree of gas-bubble dispersion, were assessed on the basis of the five typical dispersion patterns. The removal of oxygen from water was carried out analogously to the process of removing hydrogen from aluminium. The curves of the rate of oxygen removal from the model liquid were determined, showing the course of oxygen reduction during refining with the same inert gas flows and rotor speeds mentioned above.

• Klíčová slova
• aluminium, physical modeling, refining, rotary impeller,
• Publikační typ
• časopisecké články MeSH

One of the most important indicators of casting quality is porosity. The formation of pores is largely conditioned by the presence of hydrogen in the batch and subsequently in the melt. The gasification of the melt is the primary factor increasing the porosity of casts. This paper addresses the issue of reducing the melt gasification by using FDU (Foundry Degassing Unit) unit. The gas content in the melt is evaluated by determining the Dichte Index depending on the geometry and the degree of the FDU unit rotor wear. For experiments performed under the operating conditions, three types of graphite rotors with different geometries are used. The extent of melt gasification and the Dichte Index are monitored during the rotor wear, at a rate of 0%, 25%, 50%, 75% and 100% rotor wear. Secondly, the chemical composition of the melt is monitored depending on the design and wear of the rotor. It is proven that the design and the degree of rotor wear do not have significant effect on the chemical composition of the melt and all evaluated samples fell within the prescribed quality in accordance with EN 1706. With regard to the overall comparison of the geometry and wear of individual rotor types, it has been proven that, in terms of efficiency, the individual rotors are mutually equivalent and meet the requirements for melt degassing throughout the service life.

• Klíčová slova
• FDU unit, aluminum alloys, graphite rotor, melt degassing, refining,
• Publikační typ
• časopisecké články MeSH

The paper presents the results of tests carried out during the refining of the AlSi9Cu3(Fe) alloy in industrial conditions at the FDU stand. In the tests, three different rotors made of classical graphite, fine-grained graphite and classical graphite with SiC spraying were tested for the degree of wear. A series of tests was conducted for five cases-0% to 100% of consumption every 25%-corresponding to the cycles of the refining process. The number of cycles corresponding to 100% wear of each rotor was determined as 1112. The results of the rotor wear profile for all types of graphite after the assumed cycles are presented. Comparison of CAD models of new rotors and 3D scans of rotors in the final stage of operation revealed material losses during operational tests. The study assessed the efficiency of the rotor in terms of its service life as well as work efficiency. It was estimated on the basis of the calculated values of the Dichte Index (DI) and the density of the samples solidified in the vacuum. The structure of samples before and after refining at various stages of rotor wear is also presented, and the results are discussed.

• Klíčová slova
• aluminum refining, graphite wear, rotary impeller, wear testing,
• Publikační typ
• časopisecké články MeSH