CONTINUOUS CASTING METHOD

摘要

PURPOSE:To prevent generation of a flaw like crazing on the surface of a continuous casting billet in the stage of casting continuously a steel contg. elements which are liable to produce carbonitride by cooling quickly the continuous casting billet until the surface thereof attains a specific temp. and applying work strain to the surface layer. CONSTITUTION:A continuous casting billet is quickly cooled by ejecting gaseous He or the like until the surface thereof attains a temp. range of 650-950 deg.C in the stage of casting continuously an Al-killed steel or a molten steel contg. elements such as Nb, Ti, B or the like for improving the strength and toughness of the continuous casting billet. The billet is subjected to impact working such as by shot blasting, air hammering or the like to apply work strain thereto. The cooling is then returned to an ordinary cooling rate and the billet is slowly cooled by the heat regenerated from the inside to accelerate precipitation of carbonitride such as AlN, NbC or the like thereby preventing precipitation of said carbonitride at the grain boundary between ferrite and austenite and forming the finer austenite grains. The ductility of the cntinuous casting billet is improved and the generation of a flaw like crazing on the surface is prevented.