FCS&HT “SNPO “Eleron”, Moscow, Russia:

S. M. Merkulova, Design Engineer, e-mail: sveta.merkulova.68@mail.ru

All-Russia Institute of Light Alloys, Moscow, Russia:
S. G. Bochvar, Leading Engineer

Influence of ladle treatment of Al – Ti – B and Al – Ti – C systems on grain size of aluminium ingots made of A7 technical pure aluminium and A99 high pure aluminium is examined. This ladle treatment is based on usage of ultrasonic processing and modifying bars. It is shown that application of ultrasonic processing of melt flow using alloying composition with active origination particles allows to decrease essentially aluminium grain size. So, ladle treatment of A7 aluminium melt flow allowed to decrease grain size from 500 to 90 μm (grain is close to non-dendrite one). This result has been achieved during introduction of modifying bar (with composition Al – 5% Ti – 1% B, made by “Kawecki” company) in the area of developed cavitation, and with calculation of additional adding of 0.055% Ti. Investigation of A99 aluminium has displayed decrease of dendrite grain size from >2000 to 165 μm during introduction of modifying bar (with composition Al – 1.4% Ti – 0.15% C, made by VILS – All-Russian Institute of Light Alloys), without cavitation processing of melt flow, but with its ultrasonic processing. Decrease of dendrite grain size to 130 μm has been achieved during introduction of modifying bar of the same composition and with additional adding of 0.1% Ti. Introduction of additional origination nuclei from modifying bar of Al – Ti system was not finalized in such visible effect, though grain size has decreased by appr. 6 times. Complex ladle modifying of low-alloyed AD31 alloy (having no Zr in its composition) allowed to obtain non-dendrite structure with 60 μm grain average size in the ingots of 60 mm diameter. It is shown that modern ultrasonic generators can provide stable operation at industrial casting temperatures practically for all aluminium alloys. At the same time, acoustic processing parameters (such as frequency, power and amplitude) don't vary during long time comparative with casting period for industrial alloys (with diameter up to 300 mm and length up to 1.5 m). It is concluded that forming of stable cavitation area in the melt near operating ultrasonic source is possible in the case when oscillation amplitude of an oscillator exceeds 10 μm for 18–22 KHz frequency.

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