Patent ID: 7493936

Claim:
A continuous casting method for continuously casting a bloom having a substantially rectangular section, with the length of each side constituting the sectional circumference being not less than 120 mm and an aspect ratio being not less than 1.0 to not more than 2.0, at a casting rate (Vc:[m/min]) of not less than 0.5 [m/min] to not more than 2.0 [m/min], using a mold powder to be added into a mold, which is adjusted to have a total content of CaO component and SiO 2 component of not less than 50 wt % and a content of F component of not more than 11 wt %, the method comprising: providing, on the inside of said mold, a first inclined surface and a second inclined surface differed in inclination rate in order from top to down; setting the inclination rate of said first inclined surface (TRu: [%/m]) and the inclination rate of said second inclined surface (TRd: [%/m]) within ranges satisfying the following expressions (1) and (2) when the basicity of said mold powder is less than 1.1, or the solidification temperature of said mold powder is lower than 1100° C.; setting the inclination rate of said first inclined surface and the inclination rate of said second inclined surface within ranges satisfying the following expressions (3) and (4) when the basicity of said mold powder is 1.1 or more, and the solidification temperature of said mold powder is 1100° C. or higher; setting the boundary position between said first inclined surface and said second inclined surface to be distant downwardly not less than 0.2 m and not more than 0.4 m based on the upper end of the mold; boring at least two molten steel discharge ports in lower end portions of a dipping nozzle for pouring molten steel to said mold; setting the pore area of said molten steel discharge ports to not less than 2500 mm 2 to less than 6400 mm 2 ; setting the discharge angle of said molten steel discharge ports obliquely upward, based on the horizontal, to from not less than 0° to not more than 50 or obliquely downward to from not less than 0° to not more than 35° when said casting rate is not more than 0.7 [m/min]; and setting the discharge angle of said molten steel discharge ports obliquely downward, based on the horizontal, to from not less than 10° to not more than 35° when the casting rate is larger than 0.7 [m/min]. 4.4−1.95 ×Vc≦TRu≦ 6.06−2.5 ×Vc (1) 0.92−0.3 ×Vc≦TRd≦ 1.18−0.4 ×Vc (2) 2.23−1.05 ×Vc≦TRu≦ 3.18−1.4 ×Vc (3) 0.55−0.2 ×Vc≦TRd≦ 0.77−0.25 ×Vc (4).