Institute of Solid State Chemistry of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

V. M Skachkov, Researcher

S. P. Yatsenko, Head of Laboratory, e-mail: yatsenko@ihim.uran.ru

“Kamensk-Uralsky Metallurgical Works” JSC, Kamensk-Uralsky, Sverdlovsk Oblast, Russia:

P. A. Varchenya, Head of Prospective Technologies Bureau
B. V. Ovsyannikov, Chief Specialist on Casting Production

Introduction of scandium into aluminum alloys enhances the mechanical properties and corrosion resistance of constructions and ensures their weldability. Considering that more than 150 t of scandium are annually dumped with the sludge at each alumina plant, large-scale recovery of scandium from alumina production sludge makes it possible to utilize this element not only in aerospace industry, but also in civil industries and sports. The injection method improves the alloy quality by intensifying exchange processes and promotes more equilibrium distribution of alloying element, removal of some impurities, and elimination of the intermediate stage — master alloy preparation. The laboratory-scale studies of injections and 3 melting processes in the kilns at Kasensk-Uralsky Metallurgical Works made possible the perfection of technology and refinement of process powder compositions. Replacement of alkaline components by calcium ones in halogenide mixtures decreases the content of these impurities in the final alloy. It was also found that the existing strict requirements to the sodium content in such alloys stipulate usage of primary aluminum (grade A85) instead of more pure metal in the injection method. Injection was carried out on a UFR-20 plant at a temperature 780–800 ^оС. Casting of ingots with different alloy casting rates was tested. Scandium segregation in the ingots was insignificant. The required master alloys and the additive to carnallite flux were used in melts with aluminum-magnesium alloy (grade 1545K). Ingots with a 270 mm diameter were cast with different rates at 720–740 ^оС. The alloys were homogenized. The contents of sodium and hydrogen were lower than the maximum permissible values. Calcium concentration was smaller than 10^–2% (mass.). The eutectic intermetallic compounds of the alloys had a form of 10–30 μm long irregular-shaped or skeleton-like particles.

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