PRODUCTION OF CAST SLAB FOR NON-DIRECTIONALLY ORIENTED ELECTRICAL STEEL SHEET

PURPOSE:To obtain a cast slab having excellent workability without developing ridging at the time of rolling by specifying ratio of primary columnar crystal and secondary columnar crystal formed at surface layer part and inner part of the cast slab. CONSTITUTION:Molten metal of unsolidified part 53 in inner part of the cast slab 52 drawn from a mold 51 in a continuous casting machine is stirred with a primary electromagnetic stirrer 54 and a secondary electromagnetic stirrer 56. Then, solidification of the above unsolidified part 53 is completed at downstream side from bending end point 57 of the cast slab. To the unsolidified part at upstream side from the bending end point 57, the stirring force is applied with the primary and secondary electromagnetic stirrers. The thicknesses of the primary columnar crystal 2 formed at the outer layer part in the cast slab and the secondary columnar crystal 4 formed at center part are maintained to the relations specified with the inequalities I and II. By this method, casting velocity can be increased and temp. drop of the molten steel in a tundish is made to little and the low fire resisting material can be used for the refractory for lining in converter, ladle, tundish, etc.