Quenching apparatus, method for quenching, method for manufacturing cold rolled steel sheet, and method for manufacturing coated steel sheet

Abstract

A quenching apparatus which produces a good cooling effect on a metal sheet, facilitates switching between a condition of performing quenching and a condition of not performing the quenching, and can suppress thermal deformation caused by thermal radiation from the metal sheet. The quenching apparatus includes a bath that contains a cooling medium in which a metal sheet is immersed and at least one pair of rolls, which are disposed such that the metal sheet running in the bath is interposed between the at least one pair of rolls in the bath, distances of which from the metal sheet are changeable, and rotate at a peripheral speed higher than or equal to a running speed of the metal sheet.

1 . A quenching apparatus that cools a metal sheet, the apparatus comprising:
 a bath that contains a cooling medium in which the metal sheet is immersed and runs; and   at least one pair of rolls disposed such that the metal sheet running in the bath is interposed between the at least one pair of rolls in the bath, the at least one pair of rolls configured to rotate at a peripheral speed higher than or equal to a running speed of the metal sheet,   wherein distances from each roll of the at least one pair of rolls and the metal sheet are changeable.   
     
     
         2 . The quenching apparatus according to  claim 1 , wherein the at least one pair of rolls are configured to rotate in a reverse direction to a running direction of the metal sheet. 
     
     
         3 . The quenching apparatus according to  claim 1 , wherein the quenching apparatus is installed on an exit side of a soaking furnace of a continuous annealing facility. 
     
     
         4 . A method for quenching in which a metal sheet is cooled by using a quenching apparatus including a bath that contains a cooling medium in which the metal sheet is immersed and runs, the method comprising:
 in a case where quenching in which the metal sheet is immersed in the cooling medium is performed:
 causing the metal sheet to run in the bath that contains the cooling medium, and 
 in the bath, cooling the metal sheet by rotating at least one pair of rolls disposed such that the metal sheet running in the bath is interposed between the at least one pair of rolls at a peripheral speed higher than or equal to a running speed of the metal sheet, and, 
   in a case where the quenching in which the metal sheet is immersed in the cooling medium is not performed:
 causing the metal sheet to run in the bath that does not contain the cooling medium, and 
 disposing the at least one pair of rolls at positions farther from the metal sheet than positions where the at least one pair of rolls are disposed in the case where the quenching is performed. 
   
     
     
         5 . The method for quenching according to  claim 4 , wherein the at least one pair of rolls are rotated in a reverse direction to a running direction of the metal sheet. 
     
     
         6 . A method for manufacturing a cold rolled steel sheet, the method comprising:
 annealing a metal sheet that is the cold rolled steel sheet; and   quenching the cold rolled steel sheet with the method for quenching according to  claim 4 .   
     
     
         7 . A method for manufacturing a coated steel sheet, the method comprising performing a coating treatment on the cold rolled steel sheet obtained with the method for manufacturing a cold rolled steel sheet according to  claim 6 . 
     
     
         8 . The method for manufacturing a coated steel sheet according to  claim 7 , wherein the coating treatment is one treatment selected from the group consisting of an electrogalvanizing treatment, a hot-dip galvanizing treatment, and a hot-dip galvannealing treatment. 
     
     
         9 . The quenching apparatus according to  claim 2 , wherein the quenching apparatus is installed on an exit side of a soaking furnace of a continuous annealing facility. 
     
     
         10 . A method for manufacturing a cold rolled steel sheet, the method comprising:
 annealing a metal sheet that is the cold rolled steel sheet; and   quenching the cold rolled steel sheet with the method for quenching according to  claim 5 .   
     
     
         11 . A method for manufacturing a coated steel sheet, the method comprising performing a coating treatment on the cold rolled steel sheet obtained with the method for manufacturing a cold rolled steel sheet according to  claim 10 . 
     
     
         12 . The method for manufacturing a coated steel sheet according to  claim 11 , wherein the coating treatment is one treatment selected from the group consisting of an electrogalvanizing treatment, a hot-dip galvanizing treatment, and a hot-dip galvannealing treatment.