Environmentally Friendly Method to Finish Refining Aluminum Alloys

Processy litʹâ, 2019, Tom 137, №5, p.11-16

Abstract

Received 18.07.2019

UDK 669.715:66.067

At the Physical-Technological Institute of Metals and Alloys of the National Academy of Sciences of Ukraine, a new method of final rotary refining of aluminum alloys has been developed and tested. The essence of the method is as follows: a dose of aluminum melt is treated with an eccentric rotating rotor, which develops powerful internal hydrocirculation flows due to eccentricity is 5−6 cm / s with simultaneous, due to imbalance, the imposition of low-amplitude vibration (A = 0.05−0.1 mm). Such a joint effect of the forces on the melt on the one hand causes local formation of discharge zones where atomic hydrogen dissolved in the aluminum melt rushes to form molecules and gas bubbles, on the other hand (due to vibration) a discontinuity of the medium in the reaction zone «melt - rotating rotor surface», due to inertia, the speed of the reciprocating motion of individual particles will be different, which leads to the formation of microcavities with reduced pressure, where the water dissolved in the melt od, forming gas bubbles. For visualization of the rotor processing process, water with different CO2 gas content was used, which made it possible to follow the process of gas evolution and determine the speed of movement of gas bubbles in the water. It was found that gas bubbles with a diameter of less than 1 mm due to low speeds of movement can not overcome the surface tension of water and accumulate on its lower surface. Pilot testing of a new environmentally friendly method of refining allowed us to increase the yield of chill aluminum castings weighing 4 and 8 kg to 100 %.