Quenching apparatus and quenching method for metal sheet, and method for manufacturing steel sheet

Abstract

A quenching apparatus and a quenching method for a metal sheet with which it is possible to inhibit shape defects from occurring in the metal sheet when quenching is performed and a method for manufacturing a steel sheet. The quenching apparatus is placed on an exit side of a soaking zone in a continuous annealing furnace, and the apparatus includes a cooling fluid-spray device having plural spray nozzles for spraying mist onto both surfaces of a continuously transported metal sheet, and at least one pair of restraining rolls for restraining the metal sheet on both surfaces thereof in a region from a cooling start point to a cooling finish point in the cooling fluid-spray device.

1 . A quenching apparatus for a metal sheet, the apparatus configured to be placed on an exit side of a soaking zone in a continuous annealing furnace, and the apparatus comprising:
 a cooling fluid-spray device having a plurality of spray nozzles configured to spray mist onto both surfaces of a continuously transported metal sheet; and   at least one pair of restraining rolls configured to restrain the metal sheet on both of the surfaces in a region from a cooling start point to a cooling finish point of the cooling fluid-spray device.   
     
     
         2 . The quenching apparatus for a metal sheet according to  claim 1 , wherein the plurality of spray nozzles are arranged so that the mist is sprayed onto the metal sheet in a temperature range of from a martensite start temperature to a martensite finish temperature of the metal sheet. 
     
     
         3 . The quenching apparatus for a metal sheet according to  claim 1 , further comprising a dewatering spray nozzle arranged on a downstream side of an exit of the cooling fluid-spray device. 
     
     
         4 . A quenching method for a metal sheet, the method comprising spraying mist onto both surfaces of a continuously transported metal sheet to cool the metal sheet while restraining the metal sheet on both of the surfaces at least in a region in which a temperature of the metal sheet being cooled is in a range of from a martensite start temperature to a martensite finish temperature. 
     
     
         5 . The quenching method for a metal sheet according to  claim 4 , wherein a water flow density of the mist is in a range of 100 L/m 2 ·min or more and 800 L/m 2 ·min or less. 
     
     
         6 . A method for manufacturing a steel sheet, the method comprising:
 continuously annealing a steel sheet; and   quenching the annealed steel sheet by using the quenching method for a metal sheet according to  claim 4  to manufacture one of a high strength cold rolled steel sheet, a galvanized steel sheet, an electrogalvanized steel sheet, and a galvannealed steel sheet.   
     
     
         7 . The quenching apparatus for a metal sheet according to  claim 2 , further comprising a dewatering spray nozzle arranged on a downstream side of an exit of the cooling fluid-spray device. 
     
     
         8 . A method for manufacturing a steel sheet, the method comprising:
 continuously annealing a steel sheet; and   quenching the annealed steel sheet by using the quenching method for a metal sheet according to  claim 5  to manufacture one of a high strength cold rolled steel sheet, a galvanized steel sheet, an electrogalvanized steel sheet, and a galvannealed steel sheet.