Electromagnetic stirrer coil

A method for molding a steel slab by a casting process, characterized by

• (i) providing an apparatus for stirring molten steel, said apparatus comprising:
• a mold having a rectangular horizontal cross-section formed by a first and a second long side and a first and a second short side, wherein said mold comprises a nozzle at the center of the mold, said nozzle having an immersion depth L from the top of said mold,
• a first electromagnetic stirrer coil arranged along a length direction outside said first long side within a depth L from the top of said mold and parallel to said length direction of said first long side, and
• a second electromagnetic stirrer coil arranged along a length direction outside said second long side within a depth L from the top of said mold and parallel to said length direction of said second long side,
• wherein each said electromagnetic stirrer coil comprises a coil formed by a water cooled copper pipe having an outer diameter of 4 mm or less wound around a yoke for stirring molten steel in said mold by electromagnetic force and is characterized in that a space factor of a yoke sectional area located within an inside area of a vertical cross-section of said coil formed by the copper pipe with respect to said inside area is 0.5 or more and a yoke width B is less than L and in the range of 100 mm to 300 mm, and
• wherein the first and second electromagnetic stirrer coils are arranged in a manner such that a thrust generated by the first electromagnetic stirrer coil is in an opposite direction to a thrust generated by the second electromagnetic stirrer coil in said mold;
• (ii) injecting molten steel into said mold through said nozzle;
• and
• (iii) stirring molten steel in said mold by a swirl produced by the thrusts from the first and second electromagnetic stirrer coils, wherein each said electromagnetic stirrer coil generates a magnetomotive force F satisfying F/B of 800 kAT/m or more.