Method and device for continuous casting of metals in a mold

Abstract

A device for continuous or semi-continuous casting of metals, comprising a casting mold ( 1 ) which is open in both ends in the casting direction, means ( 2 ) for supplying melt to the mold ( 1 ), a first electromagnetic induction coil ( 4 ) energized by A.C. current and adapted to induce a stirring motion to the melt ( 7 ) in the mold ( 1 ), and a second electromagnetic induction coil ( 3 ) arranged upstream of the first induction coil ( 4 ) and adapted to control the stirring motion of the melt in the region adjacent to the upper free surface ( 5 ) of the melt. The second induction coil ( 3 ) is arranged to be interchangeably energized by either D.C. or A.C. current. The invention also relates to methods for control of stirring motion in a casting mold ( 1 ).

1 . A device for continuous or semi-continuous casting of metals, comprising a casting mold ( 1 ) which is open in both ends in the casting direction, means ( 2 ) for supplying melt to the mold ( 1 ), a first electromagnetic induction coil ( 4 ) energized by A.C. current and adapted to induce a stirring motion to the melt ( 7 ) in the mold ( 1 ), and a second electromagnetic induction coil ( 3 ) arranged upstream of the first induction coil ( 4 ) and adapted to control the stirring motion of the melt in the region adjacent to the upper free surface ( 5 ) of the melt, characterized in that the second induction coil ( 3 ) is arranged to be interchangeably energized by either D.C. or A.C. current.  
     
     
         2 . A device according to  claim 1 , characterized in that the device comprises means ( 12 ) for switching the current to the second induction coil ( 3 ) from A.C. to D.C. and vice versa.  
     
     
         3 . A device according to  claim 1  or  2 , characterized in that a first power source ( 10 ) is provided for supplying A.C. current to the first induction coil ( 4 ), and that a second power source ( 11 ) is provided for interchangeably supplying A.C. and D.C. current to the second induction coil ( 3 ).  
     
     
         4 . A device according to  claim 3 , characterized in that the second power source ( 11 ) is provided with electronic and programming means ( 12 ) for converting it from an A.C. current source into a D.C. current source and vice versa.  
     
     
         5 . A device according to any of the preceding claims, characterized in that the second induction coil ( 3 ) comprises coils of multi-phase and multi-pole arrangement spaced peripherally around the mold ( 1 ).  
     
     
         6 . A device according to any of the preceding claims, characterized in that the first induction coil ( 4 ) comprises coils of multi-phase and multi-pole arrangement spaced peripherally around the mold ( 1 ).  
     
     
         7 . A method for control of stirring motion in a casting mold ( 1 ) for continuous or semi-continuous casting of metals, which mold ( 1 ) is open in both ends in the casting direction, melt being supplied to the mold ( 1 ), a stirring motion being induced to the melt ( 7 ) in the mold ( 1 ) by means of a first electromagnetic induction coil ( 4 ) energized by A.C. current, the stirring motion of the melt in the region adjacent to the upper free surface ( 5 ) of the melt being controlled by means of a second electromagnetic induction coil ( 3 ) arranged upstream of the first induction coil ( 4 ), characterized in that the second induction coil ( 3 ) is interchangeably energized by either D.C. or A.C. current.  
     
     
         8 . A method according to  claim 7 , characterized in that the current to the second induction coil ( 3 ) is switched from A.C. to D.C. and vice versa by switching means ( 12 ).  
     
     
         9 . A method according to  claim 7  or  8 , characterized in that the first induction coil ( 4 ) is supplied with A.C. current from a first power source ( 10 ), and that the second induction coil ( 3 ) is interchangeably supplied with A.C. and D.C. current from a second power source ( 11 ).  
     
     
         10 . A method according to  claim 9 , characterized in that the second power source ( 11 ) is converted from an A.C. current source into a D.C. current source and vice versa by electronic and programming means ( 12 ).  
     
     
         11 . A method for control of stirring motion in a casting mold ( 1 ) for continuous or semi-continuous casting of metals, which mold ( 1 ) is open in both ends in the casting direction, melt being supplied to the mold ( 1 ), a stirring motion being induced to the melt ( 7 ) in the mold ( 1 ) by means of a first electromagnetic induction coil ( 4 ) energized by A.C. current, the stirring motion of the melt in the region adjacent to the upper free surface ( 5 ) of the melt being controlled by means of a second electromagnetic induction coil ( 3 ) arranged upstream of the first induction coil ( 4 ), characterized in that the second induction coil ( 3 ) is capable of providing three different modes of operation, namely 
 a first mode in which the second induction coil ( 3 ) is energized by A.C. current and the rotational direction of the magnetic field produced by the second induction coil ( 3 ) coincides with the rotational direction of the magnetic field produced by the first induction coil ( 4 ), the magnetic field produced by the second induction coil ( 3 ) thereby enhancing the velocity of the stirring motion induced in the region of the melt adjacent to the upper free surface ( 5 ) of the melt by the first induction coil ( 4 ), the stirring velocity of the melt in said region being controlled by adjusting the value of the A.C. current supplied to the second induction coil ( 3 ),    a second mode in which the second induction coil ( 3 ) is energized by A.C. current and the rotational direction of the magnetic field produced by the second induction coil ( 3 ) opposes the rotational direction of the magnetic field produced by the first induction coil ( 4 ), the magnetic field produced by the second induction coil ( 3 ) thereby reducing the velocity of the stirring motion induced in the region of the melt adjacent to the upper free surface ( 5 ) of the melt by the first induction coil ( 4 ), the stirring velocity of the melt in said region being controlled by adjusting the value of the A.C. current supplied to the second induction coil ( 3 ), and    a third mode in which the second induction coil ( 3 ) is energized by D.C. current so as to produce a horizontally directed D.C. magnetic field, which induces electromagnetic forces in the melt ( 7 ) opposing the direction of fluid flows, in transversal as well as longitudinal spatial planes of the mold ( 1 ), in the region of the melt adjacent to the upper free surface ( 5 ) of the melt, the magnetic field produced by the second induction coil ( 3 ) thereby reducing the velocity of the stirring motion induced in the region of the melt adjacent to the upper free surface ( 5 ) of the melt by the first induction coil ( 4 ), the velocity of longitudinal flows produced in the melt ( 7 ) by the stirring action of the first induction coil ( 4 ) as well as longitudinal flows produced by continuously discharging melt into the mold ( 1 ),    the mode of operation being selected depending upon the casting process employed.    
     
     
         12 . A method according to  claim 11 , characterized in. that the first induction coil ( 4 ) is supplied with A.C. current from a first power source ( 10 ), and that the second induction coil ( 3 ) is interchangeably supplied with A.C. and D.C. current from a second power source ( 11 ).  
     
     
         13 . A method according to  claim 12 , characterized in that the second power source ( 11 ) is converted from an A.C. current source into a D.C. current source and vice versa by electronic and programming means ( 12 ).