Method and apparatus for control of stirring in continuous casting of metals

An induction stirring method for continuous casting of billets and blooms from molten metals, which comprises:

• providing a vertical continuous casting mold having first a.c. electromagnetic induction coils in a main portion of the mold and second a.c. electromagnetic induction coils located above the first electromagnetic induction coils and adjacent an upper entrance to the mold, said second electromagnetic induction coils being capable of providing two modes of electromagnetic stirring dependent upon the continuous casting process employed,
• feeding molten metal to the mold,
• electromagnetically inducing stirring of molten metal within the continuous casting mold through rotation of the molten metal about a vertical axis with such intensity as normally to result in turbulence in the molten metal including its free surface, by applying a first rotating magnetic field to said molten metal from said first electromagnetic induction coils,
• applying simultaneously to said molten metal in the mold at a location adjacent the free surface of said molten metal, a second rotating magnetic field from said second electromagnetic induction coils, said second rotating magnetic field provided by said second electromagnetic induction coils being of an intensity which selectively is:
• (a) at least sufficient to minimize the stirring motion and disturbances induced by said first electromagnetic induction coils in said free surface area when the second electromagnetic induction coils are operated in said first mode of operation to produce the second rotating magnetic field rotating in a direction opposite to the direction of rotation of the first rotating magnetic field when submerged entry nozzle casting is effected with surface mold powder, or
• (b) at least sufficient to enhance the stirring motion induced by said first electromagnetic induction coils in said free surface area when the second electromagnetic induction coils are operated in said second mode of operation to produce the second rotating magnetic fields rotating in a direction which is the same as the direction of rotation of said first rotating magnetic field when casting is effected without mold powder.