Method for continuously casting steel
A primary object of the present invention is to provide a technique of avoiding occurrence of surface defects caused by an electromagnetic brake while checking internal defects with this electromagnetic brake, so that cleanliness of a cast steel can be improved compared with prior arts, and the present invention provides a method for continuously casting steel, the method comprising supplying molten steel into a funnel mold while applying an electromagnetic brake to an outlet flow discharged from an outlet port of an immersion nozzle, wherein magnetic flux density (B) of the electromagnetic brake is within a range of the following (Formula 1): B min ≤ B ≤ B max , B min = 800 · ( D max D 0 ) 3 · ( H SEN H 0 ) ( v · sin θ ) , and B max = 3000 · ( D max D 0 ) 3 · ( H SEN H 0 ) ( v · sin θ ) 2 . ( Formula 1 )
1. A method for continuously casting steel, the method comprising supplying molten steel into a mold while applying an electromagnetic brake to an outlet flow discharged from an outlet port of an immersion nozzle,
wherein magnetic flux density (B) of the electromagnetic brake is within a range of the following (Formula 1), and
a funnel mold with short sides and long sides on a horizontal cross-section, in which a distance between the long sides facing each other in the mold at a middle of each long side is enlarged than a distance between the long sides at ends of the long sides, is used as the mold:
B min ≤B≤B max (Formula 1)
wherein
B
min
=
800
·
(
D
max
D
0
)
3
·
(
H
SEN
H
0
)
(
v
·
sin
θ
)
,
B
max
=
3000
·
(
D
max
D
0
)
3
·
(
H
SEN
H
0
)
(
v
·
sin
θ
)
2
,
D 0 =a mold thickness (m) of the mold having short sides and long sides on a horizontal cross-sectional shape, the mold thickness measured as a distance between the long sides facing each other in the mold at ends of the long sides,
D max =a maximum value of a mold thickness (m) of the mold having the short sides and the long sides on the horizontal cross-sectional shape, the maximum value measured as a distance between the long sides facing each other in the mold at a middle of each long side,
H 0 =a distance (m) between a surface of the molten steel and a center of an electromagnetic brake coil in a vertical direction,
H SEN =a distance (m) between a bottom surface of the immersion nozzle and the center of the electromagnetic brake coil in the vertical direction,
v=a flow velocity (m/s) of the molten steel discharged from the immersion nozzle, and
θ=an outlet flow angle (°) of the molten steel, wherein the flow velocity v of the molten steel is 0.441 m/s to 1.256 m/s.
2. The method for continuously casting steel according to claim 1 , wherein D max /D 0 is 1.16 to 1.24.
3. The method for continuously casting steel according to claim 1 , wherein H SEN /H 0 is 0.161 to 0.327.
4. The method for continuously casting steel according to claim 1 , wherein the outlet flow angle θ of the molten steel is −45° to −5°.