Rotary degasser and rotor therefor

A device for releasing and mixing gas into molten metal, the device comprising:

• (a) a motor;
• (b) a drive shaft having a first end connected to the motor and a second end, the drive shaft having a passage through which gas can travel and opening at the second end through which the gas is released;
• and
• (c) an impeller connected to the second end of the drive shaft, the impeller comprising:
• (i) a gas-release opening through which gas from the second end of the drive shaft is released;
• (ii) a top portion having a lower surface;
• (iii) a second portion below the lower surface of the top portion and connected to the lower surface, the second portion including a plurality of cavities and a protrusion between each cavity, wherein each protrusion has an edge for shearing gas as the impeller rotates, the edge of each protrusion being turned inwards towards the cavity to which it is juxtaposed, and the cavities, protrusions and edges are covered by the lower surface of the top portion;
• wherein when gas is released from the gas-release opening it rises into the plurality of cavities and the lower surface of the top portion helps to retain the gas in the plurality of cavities to help mix the gas and molten metal, and the edges of the protrusions shear the gas into smaller bubbles to assist in mixing the gas with the molten metal.