Impact of Rotor Design on Its Wear and Work Efficiency of the Aluminum Refining Process

Abstract

Both the wear and the geometry of the rotor determine the efficiency of the process of aluminum refining. The paper presents wear tests of two different rotors: I (pump type) and II (propeller type). The operation of both rotors in industrial conditions was compared and their service life was examined. It was found that rotor I is more durable than the tested rotor II, and at the same time it provides a good level of hydrogen removal throughout the operation period, i.e., 1112 refining cycles. Rotor wear after refining was calculated by 3D scanning. The study also investigated the impact of rotor geometry on the efficiency of the refining process. The degassing efficiency was determined during refining in a foundry using the Dichte Index (DI). The alloy density and the volume of hydrogen removed were also tested for five stages of rotor wear: 0%, 25%, 50%, 75% and 100%. Both new rotors performed worse in removing hydrogen from the liquid alloy than the worn rotors due to their humidity which cannot be eliminated in the initial stage of their operation. A Dross Test was also performed to determine non-metallic impurities and compare size and number of cavities for rotor I and II. The best results of removing non-metallic inclusions by flotation were obtained for rotor I at the end of its operation.

Assessment of refining efficiency during the refining cycle in a foundry degassing unit in industrial conditions

“…However, some discrepancy in the results is understandable, considering that physical modelling was carried out in laboratory conditions, where there are fewer variables and it is easier to ensure the same conditions for each experiment. One should also take into account the increasing wear of the rotor, which is already known to have a positive effect on its efficiency 39 . In this case, however, the effect of wear cannot be taken into account, because the tests were carried out with the most worn rotor of the variant with the lowest rotary impeller speed, which, however, turned out to be the least efficient.…”

“…In order to obtain appropriate results, it is therefore necessary to conduct experiments directly in the operating conditions of the foundry 38 . The study of the efficiency of degassing depending on the wear of the rotor 39 , and the study of the operation of various types of refining gases (Ar, N 2 ) should also be mentioned.…”

Preparation of Rotor Geometry for Setting up Numerical Model of Flow in Refining Ladle

“…The refining process using an FDU unit can be divided into particular cycles with regard to the rotor lifetime. In case the material of the rotor system is graphite, the geometry of the rotary impeller changes with the increasing number of cycles due to external phenomena such as oxidation at higher temperatures and abrasion, which subsequently has an effect on the refining process [2]. We can identify purely negative effects such as the peeling-off of the rotor parts, which affects the purity of the aluminum-liquid alloy after the refining.…”

The processing of experimental data from the physical model of A fdu refining unit

“…To develop the methodology, data from a physical model of the FDU refining unit used in the operating conditions of MOTOR JIKOV Slévárna a.s. were used. The physical modelling was carried out as part of research aimed at optimizing the refining technology in order to increase the quality of aluminium castings [14,16,17]. A number of rotors of different shapes and materials were examined as part of the modelling.…”