Method for manufacturing hot-rolled coil, and method for shape-correction of hot-rolled coil

Abstract

Embodiments include a method for manufacturing a hot-rolled coil and a method for correcting the shape of a hot-rolled coil. In one embodiment, the method for manufacturing the hot-rolled coil includes the steps of: reheating a steel slab comprising 0.18 to 0.56 wt % carbon (C), 0.1 to 0.5 wt % silicon (Si), 0.7 to 6.5 wt % manganese (Mn), more than 0 wt % but not more than 0.02 wt % phosphorus (P), more than 0 wt % but not more than 0.02 wt % sulfur (S), more than 0 wt % but not more than 0.3 wt % chromium (Cr), more than 0 wt % but not more than 0.004 wt % boron (B), 0.01 to 0.04 wt % titanium (Ti), and the remainder being iron (Fe) and other inevitable impurities; hot-rolling the steel slab at a finishing mill delivery temperature of 850° C. to 950° C., thereby forming a hot-rolled sheet; and cooling the hot-rolled sheet, followed by coiling at a coiling temperature of 700° C. or higher.

1 . A method for manufacturing a hot-rolled coil, the method comprising the steps of:
 reheating a steel slab to form a reheated steel slab, the steel slab comprising 0.18 wt % to 0.56 wt % carbon (C), 0.1 wt % to 0.5 wt % silicon (Si), 0.7 wt % to 6.5 wt % manganese (Mn), more than 0 wt % but not more than 0.02 wt % phosphorus (P), more than 0 wt % but not more than 0.02 wt % sulfur (S), more than 0 wt % but not more than 0.3 wt % chromium (Cr), more than 0 wt % but not more than 0.004 wt % boron (B), 0.01 wt % to 0.04 wt % titanium (Ti), and the remainder being iron (Fe) and other inevitable impurities;   hot-rolling the reheated steel slab at a finishing mill delivery temperature of 850° C. to 950° C., thereby forming a hot-rolled sheet; and   cooling the hot-rolled sheet, followed by coiling at a coiling temperature of 700° C. or higher.   
     
     
         2 . The method of  claim 1 , wherein the steel slab comprises 0.21 wt % to 0.37 wt % carbon (C), 0.1 wt % to 0.4 wt % silicon (Si), 1.1 wt % to 1.5 wt % manganese (Mn), more than 0 wt % but not more than 0.02 wt % phosphorus (P), more than 0 wt % but not more than 0.02 wt % sulfur (S), 0.1 wt % to 0.3 wt % chromium (Cr), 0.001 wt % to 0.004 wt % boron (B), 0.01 wt % to 0.04 wt % titanium (Ti), and the remainder being iron (Fe) and other inevitable impurities. 
     
     
         3 . The method of  claim 1 , wherein the steel slab comprises 0.18 wt % to 0.25 wt % carbon, 0.3 wt % to 0.5 wt % silicon (Si), 2 wt % to 6.5 wt % manganese (Mn), more than 0 wt % but not more than 0.02 wt % phosphorus (P), more than 0 wt % but not more than 0.01 wt % sulfur (S), more than 0 wt % but not more than 0.1 wt % chromium (Cr), more than 0 wt % but not more than 0.001 wt % boron (B), 0.01 to 0.04 wt % titanium (Ti), and the remainder being iron (Fe) and other inevitable impurities. 
     
     
         4 . The method of  claim 1 , wherein the steel slab comprises 0.5 wt % to 0.56 wt % carbon (C), 0.1 wt % to 0.3 wt % silicon (Si), 0.7 wt % to 1 wt % manganese (Mn), more than 0 wt % but not more than 0.02 wt % phosphorus (P), more than 0 wt % but not more than 0.01 wt % sulfur (S), 0.1 wt % to 0.3 wt % chromium (Cr), more than 0 wt % but not more than 0.001 wt % boron (B), 0.01 to 0.02 wt % titanium (Ti), and the remainder being iron (Fe) and other inevitable impurities. 
     
     
         5 . The method of  claim 1 , wherein the hot-rolled sheet is cooled and coiled at a coiling temperature of 700° C. to 900° C. 
     
     
         6 . A method for correcting a shape of a hot-rolled coil, the method comprising the steps of:
 mounting the hot-rolled coil on a hanger forming a lower part of a C-hook;   measuring a longest diameter of the hot-rolled coil using an outer diameter measuring means provided in an upper part of the C-hook;   adjusting the longest diameter of the hot-rolled coil to be perpendicular to the C-hook by means of a driving roll provided on the hanger; and   placing the C-hook, which has the hot-rolled coil mounted thereon, on a stand, followed by lifting, thereby correcting the shape of the hot-rolled coil by self-weight.   
     
     
         7 . A method for correcting a shape of a hot-rolled coil, the method comprising the steps of:
 mounting the hot-rolled coil on a hanger forming a lower part of a C-hook;   measuring a longest diameter of the hot-rolled coil using an outer diameter measuring means provided in an upper part of the C-hook;   adjusting the longest diameter of the hot-rolled coil to be perpendicular to the C-hook by means of a driving roll provided on the hanger; and   placing the C-hook, which has the hot-rolled coil mounted thereon, on a stand, followed by lifting, thereby correcting the shape of the hot-rolled coil by self-weight,   wherein the hot-rolled coil is manufactured by a method comprising the steps of:   reheating a steel slab comprising 0.18 wt % to 0.56 wt % carbon (C), 0.1 wt % to 0.5 wt % silicon (Si), 0.7 wt % to 6.5 wt % manganese (Mn), more than 0 wt % but not more than 0.02 wt % phosphorus (P), more than 0 wt % but not more than 0.02 wt % sulfur (S), more than 0 wt % but not more than 0.3 wt % chromium (Cr), more than 0 wt % but not more than 0.004 wt % boron (B), 0.01 wt % to 0.04 wt % titanium (Ti), and the remainder being iron (Fe) and other inevitable impurities;   hot-rolling the steel slab at a finishing mill delivery temperature of 850° C. to 950° C., thereby forming a hot-rolled sheet; and   cooling the hot-rolled sheet, followed by coiling at a coiling temperature of 700° C. or higher.   
     
     
         8 . The method of  claim 7 , wherein the hot-rolled coil comprises 0.21 wt % to 0.37 wt % carbon (C), 0.1 wt % to 0.4 wt % silicon (Si), 1.1 wt % to 1.5 wt % manganese (Mn), more than 0 wt % but not more than 0.02 wt % phosphorus (P), more than 0 wt % but not more than 0.02 wt % sulfur (S), 0.1 wt % to 0.3 wt % chromium (Cr), 0.001 wt % to 0.004 wt % boron (B), 0.01 wt % to 0.04 wt % titanium (Ti), and the remainder being iron (Fe) and other inevitable impurities. 
     
     
         9 . The method of  claim 7 , wherein the hot-rolled sheet is cooled and coiled at a coiling temperature of 700° C. to 900° C.