Method for controlling surface quality of ultra-low carbon steel slab

A method for controlling a surface quality of an ultra-low carbon steel slab, the method comprising the steps of:

• measuring of a phosphorus (P) concentration of a molten steel which is introduced into a mold in a continuous casting process for producing the ultra-low carbon steel slab,
• measuring of a sulfur (S) concentration of the molten steel,
• measuring a superheating temperature of the molten steel,
• measuring a width of the mold, and measuring a casting speed of the ultra-low carbon steel slab;
• and calculating a depth of a hook which is formed when the molten steel is solidified into the slab, as a function of the measured width of the mold, the measured phosphorus (P) concentration of the molten steel, the measured sulfur (S) concentration of the molten steel, the measured superheating degree of the molten steel, and the measured casting speed of the slab, calculating the depth of the hook utilizing the following equation:
• Y=A0ln(A1×A4/(A2×A3×A5))+B
• wherein A1 is the width of the mold;
• A2 is the superheating temperature;
• A3 is the casting speed;
• A4 is the sulfur (S) concentration;
• A5 is the phosphorus (P) concentration;
• Y is the depth of the hook;
• A0 is a coefficient;
• and B is a constant, wherein 0.51≦A0≦0.94;
• and −0.21≦B≦0.11;
• and changing the superheating degree to control the depth of the hook, when the calculated depth of the hook is deeper than a preset depth of the hook.

A method for controlling a surface quality of an ultra-low carbon steel slab, the method comprising the steps of:

• measuring of a phosphorus (P) concentration of a molten steel which is introduced into a mold in a continuous casting process for producing the ultra-low carbon steel slab,
• measuring of a sulfur (S) concentration of the molten steel,
• measuring a superheating temperature of the molten steel,
• measuring a width of the mold, and measuring a casting speed of the ultra-low carbon steel slab;
• and calculating a depth of a hook which is formed when the molten steel is solidified into the slab, as a function of the measured width of the mold, the measured phosphorus (P) concentration of the molten steel, the measured sulfur (S) concentration of the molten steel, the measured superheating degree of the molten steel, and the measured casting speed of the slab, calculating the depth of the hook utilizing the following equation:
• Y=A0ln(A1×A4/(A2×A3×A5))+B
• wherein A1 is the width of the mold;
• A2 is the superheating temperature;
• A3 is the casting speed;
• A4 is the sulfur (S) concentration;
• A5 is the phosphorus (P) concentration;
• Y is the depth of the hook;
• A0 is a coefficient;
• and B is a constant, wherein 0.51≦A0≦0.94;
• and −0.21≦B≦0.11;
• and
• scarfing a surface of the ultra-low carbon steel slab as a function of the calculated depth of the hook.