Quenching apparatus, quenching method, and method of manufacturing metal sheet

Abstract

A metal-sheet quenching apparatus that cools a metal sheet while conveying the metal sheet. The metal-sheet quenching apparatus includes a cooling device that cools a metal sheet that is conveyed, restraining rolls that convey the metal sheet cooled by the cooling device while restraining the metal sheet in the thickness direction, a roll moving device that moves the restraining rolls in the conveyance direction of the metal sheet, and a movement control device that controls the operation of the roll moving device to adjust the position of the restraining rolls.

1 . A metal-sheet quenching apparatus that cools a metal sheet while conveying the metal sheet, the metal-sheet quenching apparatus comprising:
 a cooling device configured to cool the metal sheet that is conveyed;   a restraining roll configured to convey the metal sheet cooled by the cooling device while restraining the metal sheet in a thickness direction;   a roll moving device configured to move the restraining roll in a conveyance direction of the metal sheet; and   a movement control device configured to adjust a position of the restraining roll by controlling an operation of the roll moving device.   
     
     
         2 . The metal-sheet quenching apparatus according to  claim 1 , wherein the cooling device includes a plurality of nozzles configured to jet a cooling fluid therethrough to the metal sheet to cool the metal sheet. 
     
     
         3 . The metal-sheet quenching apparatus according to  claim 1 , wherein the cooling device includes a cooling tank configured to store a cooling fluid and the metal sheet is cooled by being immersed in the cooling fluid. 
     
     
         4 . The metal-sheet quenching apparatus according to  claim 1 , wherein the movement control device controls the operation of the roll moving device to position the restraining roll such that the restraining roll restrains the metal sheet at a position at which the metal sheet has a target temperature. 
     
     
         5 . The metal-sheet quenching apparatus according to  claim 4 , wherein the target temperature is set in a temperature range of (TMs+150) (° C.) to (TMf−150) (° C.), where TMs (° C.) is a Ms temperature at which a martensitic transformation of the metal sheet starts and TMf (° C.) is a Mf temperature at which the martensitic transformation ends. 
     
     
         6 . The metal-sheet quenching apparatus according to  claim 4 , wherein the movement control device sets a distance from a cooling start position by the cooling device to the restraining roll based on a line speed of the metal sheet, a cooling start temperature of the metal sheet at a time when cooling by the cooling device is started, the target temperature, and a cooling rate of cooling of the metal sheet, and moves the position of the restraining roll such that the set distance is achieved. 
     
     
         7 . The metal-sheet quenching apparatus according to  claim 6 , wherein the movement control device obtains a distance d (mm) from the cooling start position to the restraining roll by Formula (1) below: 
       
         
           
             
               
                 
                   
                     
                       d 
                       = 
                       
                         
                           ( 
                           
                             
                               T 
                               ⁢ 
                               1 
                             
                             - 
                             
                               T 
                               ⁢ 
                               2 
                             
                           
                           ) 
                         
                         × 
                         v 
                         / 
                         CV 
                       
                     
                     , 
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         where v (mm/s) is the line speed of the metal sheet, T1(° C.) is the cooling start temperature, T2(° C.) is the target temperature, and CV(° C./s) is the cooling rate of cooling of the metal sheet by the cooling device. 
       
     
     
         8 . The metal-sheet quenching apparatus according to  claim 7 , wherein, based on a sheet thickness t of the metal sheet and a coefficient α corresponding to a condition of cooling of the metal sheet, the cooling rate CV is set as CV=α/t in the movement control device. 
     
     
         9 . A metal-sheet quenching method in which a metal sheet is cooled while being conveyed, the method comprising:
 moving a restraining roll in a conveyance direction of the metal sheet such that, when the metal sheet that has been cooled is restrained by the restraining roll in a thickness direction, the metal sheet is restrained at a position at which the metal sheet has a target temperature.   
     
     
         10 . The metal-sheet quenching method according to  claim 9 , wherein the target temperature is set in a temperature range of (TMs+150) (° C.) to (TMf−150) (° C.), where TMs (° C.) is a Ms temperature at which a martensitic transformation of the metal sheet starts and TMf (° C.) is a Mf temperature at which the martensitic transformation ends. 
     
     
         11 . The metal-sheet quenching method according to  claim 9 , wherein moving of the restraining roll is performed by:
 setting a distance from a cooling start position to the restraining roll based on a line speed of the metal sheet, a cooling start temperature of the metal sheet at a time when cooling is started, the target temperature, and a cooling rate of cooling of the metal sheet, and   moving the restraining roll such that the set distance is achieved.   
     
     
         12 . The metal-sheet quenching method according to  claim 11 , wherein, as the distance from the cooling start position to the restraining roll, a distance d (mm) from the cooling start position to the restraining roll is obtained by Formula (1) below: 
       
         
           
             
               
                 
                   
                     
                       d 
                       = 
                       
                         
                           ( 
                           
                             
                               T 
                               ⁢ 
                               1 
                             
                             - 
                             
                               T 
                               ⁢ 
                               2 
                             
                           
                           ) 
                         
                         × 
                         v 
                         / 
                         CV 
                       
                     
                     , 
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         where v (mm/s) is the line speed of the metal sheet, T1(° C.) is the cooling start temperature, T2(° C.) is the target temperature, and CV(° C./s) is the cooling rate of cooling of the metal sheet. 
       
     
     
         13 . The metal-sheet quenching method according to  claim 12 , wherein, based on a sheet thickness t of the metal sheet and a coefficient α corresponding to a condition of cooling of the metal sheet, the cooling rate CV is set as CV=α/t. 
     
     
         14 . A method of manufacturing a metal sheet, the method comprising using the metal-sheet quenching method according to  claim 9  to obtain the metal sheet. 
     
     
         15 . A method of manufacturing a metal sheet, the method comprising performing a hot-dip galvanizing treatment, an electro-galvanizing treatment, or a hot-dip galvannealing treatment on the metal sheet obtained by the method according to  claim 14 .