The paper describes research and development of aluminium melt refining technology in a ladle with rotating impeller and breakwaters using numerical modelling of a finite volume/element method. The theoretical aspects of refining technology are outlined. The design of the numerical model is described and discussed. The differences between real process conditions and numerical model limitations are mentioned. Based on the hypothesis and the results of numerical modelling, the most appropriate setting of the numerical model is recommended. Also, the possibilities of monitoring of degassing are explained. The results of numerical modelling allow to improve the refining technology of metal melts and to control the final quality under different boundary conditions, such as rotating speed, shape and position of rotating impeller, breakwaters and intensity of inert gas blowing through the impeller.

Entrapped gases, solidification shrinkage and non-metallic compound formation are main sources of porosity in aluminium alloy castings. Porosity is detrimental to the mechanical properties of these castings; therefore, its reduction is pursued. Rotary degassing is the method mostly employed in industry to remove dissolved gases from aluminium melts, reducing porosity formation during solidification of the cast part. Recently, ultrasonic degassing has emerged as a promising alternative thanks to a lower dross formation and higher energy efficiency. This work aims to evaluate the efficiency of the ultrasonic degasser and compare it to a conventional rotary degassing technique applied to an AlSi10Mg alloy. Degassing efficiency was evaluated employing the reduced pressure test (RPT), where samples solidified under reduced pressure conditions are analysed. Factors affecting RPT were considered and temperature parameters for the test were established. The influence of ultrasonic degassing process parameters, such as degassing treatment duration and purging gas flow rate were studied, as well as treated aluminium volume and oxide content. Finally, ultrasonic degassing process was contrasted to a conventional rotary degassing technique, comparing their efficiency.

The gas porosity is one of the most serious problems in the casting of aluminum. There are several degassing methods that have been

studied. During smelting of aluminum, the intermetallic compound (IMC) may be formed at the interface between molten aluminum and

solid steel of crucible furnace lining. In this study, the effect of degassing treatment on the formations of IMC has been investigated. The

rectangular substrate specimens were immersed in a molten aluminum bath. The holding times of the substrate immersions were in the

range from 300 s to 1500 s. Two degassing treatments, argon degassing and hexachloroethane tablet degassing, were conducted to

investigate their effect on the IMC formation. The IMC was examined under scanning electron microscope with EDX attachment. The

thickness of the IMC layer increased with increasing immersion time for all treatments. Due to the high content of hydrogen, substrate

specimens immersed in molten aluminum without degasser had IMC layer which was thicker than others. Argon degassing treatment was

more effective than tablet degassing to reduce the IMC growth. Furthermore, the hard and brittle phase of IMC, FeAl3, was formed

dominantly in specimens immersed for 900 s without degasser while in argon and tablet degasser specimens, it was formed partially.