Patent ID: 8397793

Claim:
A steel continuous casting method using a continuous caster that includes a pair of upper magnetic poles and a pair of lower magnetic poles disposed on outer sides of a mold, the upper magnetic poles facing each other with a mold long side portion therebetween and the lower magnetic poles facing each other with the mold long side portion therebetween, and an immersion nozzle having a molten steel spout located between a peak position of a DC magnetic field of the upper magnetic poles and a peak position of a DC magnetic field of the lower magnetic poles, the method comprising braking a molten steel flow with the DC magnetic fields respectively applied to the pair of upper magnetic poles and the pair of lower magnetic poles while stirring a molten steel with an AC magnetic field simultaneously applied to the pair of upper magnetic poles, wherein the immersion nozzle, the molten steel spout of which has a molten steel discharge angle of 40° or more and less than 55° downward with respect to a horizontal direction, is used at an immersion depth (distance from a meniscus to an upper end of the molten steel spout) of 180 mm or more and less than 240 mm, a strength of the AC magnetic field applied to the upper magnetic poles is set to 0.060 to 0.090 T, a strength of a DC magnetic field applied to the upper magnetic poles is set to 0.18 to 0.35 T, a strength of a DC magnetic field applied to the lower magnetic poles is set to 0.30 to 0.45 T, and continuous casting is conducted at casting speeds (a) to (i) below: (a) when a slab width is less than 950 mm, the casting speed is 1.35 m/min or more and less than 3.05 m/min; (b) when a slab width is 950 mm or more and less than 1150 mm, the casting speed is 1.25 m/min or more and less than 3.05 m/min; (c) when a slab width is 1150 mm or more and less than 1250 mm, the casting speed is 1.25 m/min or more and less than 2.95 m/min; (d) when a slab width is 1250 mm or more and less than 1350 mm, the casting speed is 1.25 m/min or more and less than 2.75 m/min; (e) when a slab width is 1350 mm or more and less than 1450 mm, the casting speed is 1.05 m/min or more and less than 2.65 m/min; (f) when a slab width is 1450 mm or more and less than 1550 mm, the casting speed is 1.05 m/min or more and less than 2.45 m/min; (g) when a slab width is 1550 mm or more and less than 1650 mm, the casting speed is 0.95 m/min or more and less than 2.35 m/min; (h) when a slab width is 1650 mm or more and less than 1750 mm, the casting speed is 0.95 m/min or more and less than 2.25 m/min; and (i) when a slab width is 1750 mm or more and less than 1850 mm, the casting speed is 0.95 m/min or more and less than 2.15 m/min.