PRODUCTION OF CONTINUOUSLY CAST INGOT HAVING SOUND SURFACE AND INTERNAL QUALITY

摘要

PURPOSE:To obtain a continuously cast ingot of rimmed steel or semikilled steel having sound surface and internal quality without any blow hole defects by specifying the product of the carbon content and the amt. of dissolved oxygen in steel, the velocity of flow of the molten steel in the stage of force agitation of the molten steel and the content of S in the steel. CONSTITUTION:Molten steel of =0.015% S and CX0=8X10-4%2 is cast continuously while said steel is fluidized forcibly at =1m/sec velocity of flow by means of an agitating mechanism for molten steel provided to a mold or near the same. Here if S is contained at =0.015%, the limit amt. of dissolved oxygen can be increased considerably. CX0 is determined at the above-described value from the value CX0 of the case in which the molten steel contg. S at 0.002% which is nearly the upper limit value permissible in actual operation is agitated electromagnetically at =1m/sec. As the velocity of flow of the molten steel is lower within the range at which an effect is provided, the results are better, and in excess of 1m/sec, there is possibility of the generation of surface defects owing to slag inclusion in the corner parts of the mold with some steel kinds.