1987 Volume 51 Issue 4 Pages 370-374
The grain structure of continuously cast aluminum ingots was refined without addition of a grain refiner. A ring-type oscillator which had a heating coil insulated with alumina cement was set just below the molten surface of a mold 80 mm in inside diameter.
Coarse crystals at the chill zone and columnar crystals inside the chill zone appeared, when no oscillator used. As the temperature of the oscillator was lower than the melting point of aluminum, the oscillator was trapped by a solidifying shell, and so continuous casting was not possible.
Main variables which affected the equiaxed crystal zone were the frequency, the amplitude and the diameter of the oscillator. In this experiment, the frequency was 20 s−1 to 50 s−1, the amplitude was 0.5 mm to 4 mm, and the diameter of the oscillator was 56 mm, 64 mm and 72 mm, respectively.
The largest oscillator gave the largest equiaxed crystal zone. A greater frequency and amplitude enlarged the equiaxed zone still further. Using an oscillator 72 mm in diameter, a fully equiaxed crystal zone was obtained, when the frequency and the amplitude exceeded 40 s−1 and 4 mm, respectively.
