Quenching apparatus for metal sheet, continuous annealing equipment, method for quenching metal sheet, method for manufacturing cold rolled steel sheet, and method for manufacturing coated steel sheet

Abstract

A quenching apparatus for a metal sheet, continuous annealing equipment, a method for quenching a metal sheet, a method for manufacturing a cold rolled steel sheet, and a method for manufacturing a coated steel sheet. The quenching apparatus has a water tank in which the metal sheet is passed and immersed in a liquid to cool the metal sheet, a water injection apparatus placed in the water tank, and plural restraining roll pairs with which the metal sheet that is passed in the water tank is restrained. The water injection apparatus has plural water injection nozzles arranged in a sheet passing direction of the metal sheet on front and back surface sides of the metal sheet. A position of each of the plural restraining roll pairs is separately adjusted with respect to the metal sheet in accordance with operation conditions.

1 . A quenching apparatus for a metal sheet, the quenching apparatus comprising:
 a water tank configured to pass and immerse the metal sheet in a liquid to cool the metal sheet;   a water injection apparatus placed in the water tank; and   a plurality of restraining roll pairs configured to restrain the metal sheet that is passed in the water tank,   wherein the water injection apparatus has a plurality of water injection nozzles arranged in a sheet passing direction of the metal sheet on front and back surface sides of the metal sheet so that cooling water is injected in facing directions from the front and back surface sides, and   a position of each of the plurality of restraining roll pairs is separately adjusted with respect to the metal sheet in accordance with operation conditions.   
     
     
         2 . The quenching apparatus for a metal sheet according to  claim 1 , wherein both largest and smallest values of a maximum height roughness Rz of surfaces of the plurality of restraining roll pairs are in a range of 5 μm or more and 50 μm or less. 
     
     
         3 . The quenching apparatus for a metal sheet according to  claim 1 , wherein a roll diameter of restraining rolls constituting the plurality of restraining roll pairs is in a range of 50 mm or more and 250 mm or less. 
     
     
         4 . The quenching apparatus for a metal sheet according to  claim 1 , wherein the plurality of restraining roll pairs are arranged such that a distance between central axes of the restraining rolls facing each other across the metal sheet is in a range of (D×¼) (mm) or more and D (mm) or less,
 where D (mm) is a roll diameter of restraining rolls constituting each pair. 
 
     
     
         5 . Continuous annealing equipment having the quenching apparatus for a metal sheet according to  claim 1 , the quenching apparatus being placed on an exit side of a soaking zone of the continuous annealing equipment. 
     
     
         6 . A method for quenching a metal sheet, the method comprising:
 continuously passing and immersing the metal sheet in a liquid so as to be cooled; and   restraining the metal sheet by using a plurality of restraining roll pairs,   wherein positions of the plurality of restraining roll pairs with respect to the metal sheet are adjusted while a temperature of the metal sheet is in a range of equal to or lower than (a martensite start temperature of the metal sheet+150° C.) and equal to or higher than (a martensite finish temperature of the metal sheet−150° C.).   
     
     
         7 . A method for manufacturing a cold rolled steel sheet, the method comprising quenching a cold rolled steel sheet by using the method for quenching a metal sheet according to  claim 6 . 
     
     
         8 . A method for manufacturing a coated steel sheet, the method comprising subjecting the cold rolled steel sheet manufactured by using the method for manufacturing a cold rolled steel sheet according to  claim 7  to a coating treatment. 
     
     
         9 . The method for manufacturing a coated steel sheet according to  claim 8 , wherein the coating treatment is performed by using a method of one of an electro-galvanizing treatment, a hot-dip galvanizing treatment, and a hot-dip galvannealing treatment. 
     
     
         10 . Continuous annealing equipment having the quenching apparatus for a metal sheet according to  claim 2 , the quenching apparatus being placed on an exit side of a soaking zone of the continuous annealing equipment. 
     
     
         11 . Continuous annealing equipment having the quenching apparatus for a metal sheet according to  claim 3 , the quenching apparatus being placed on an exit side of a soaking zone of the continuous annealing equipment. 
     
     
         12 . Continuous annealing equipment having the quenching apparatus for a metal sheet according to  claim 4 , the quenching apparatus being placed on an exit side of a soaking zone of the continuous annealing equipment.