Cold rolling method, cold rolling equipment, and cold-rolled steel sheet manufacturing method

Abstract

A cold rolling method, cold rolling equipment, and a cold-rolled steel sheet manufacturing method capable of preventing sheet breakage by sufficiently suppressing occurrence of an edge crack of a material to be rolled during cold rolling. In the cold rolling method, a rolling mill including a plurality of stands to cold-rolls a material to be rolled. An N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction among the plurality of stands, includes a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter. The N-th stand rolls the material to be rolled with a linear load of 0.8 t/mm or more.

1 . A cold rolling method for cold-rolling a material to be rolled by a rolling mill including a plurality of stands,
 wherein an N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction among the plurality of stands, includes a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter, and   the N-th stand rolls the material to be rolled with a linear load of 0.8 t/mm or more.   
     
     
         2 . The cold rolling method according to  claim 1 , wherein, in a case where the N-th stand rolls the material to be rolled with a linear load of less than 1.4 t/mm, the material to be rolled is rolled by setting a tapered rolling portion width WRδ which is a length, which faces the material to be rolled, of the taper formed on the tapered work roll of the N-th stand as ±0 mm to +50 mm. 
     
     
         3 . The cold rolling method according to  claim 1 , wherein, in a case where the N-th stand rolls the material to be rolled with a linear load of 1.4 t/mm or more, the material to be rolled is rolled by setting a tapered rolling portion width WRδ which is a length, which faces the material to be rolled, of the taper formed on the tapered work roll of the N-th stand as −50 mm to −5 mm. 
     
     
         4 . The cold rolling method according to  claim 1 , wherein, among the plurality of stands, an (N+1)-th stand arranged in an (N+1)-th position on a downstream side of the N-th stand rolls the material to be rolled with a flat work roll having a uniform diameter of a roll. 
     
     
         5 . A cold rolling method for cold-rolling a material to be rolled by a rolling mill including a plurality of stands,
 wherein an N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction and an (N+1)-th stand arranged in an (N+1)-th position on a downstream side of the N-th stand among the plurality of stands, include a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter, and   each of the N-th stand and the (N+1)-th stand rolls the material to be rolled with a linear load of 1.7 t/mm or more and a tapered rolling portion width WRδ which is a length, which faces the material to be rolled, of the taper formed on the tapered work roll of each of the N-th stand and the (N+1)-th stand is set as −50 mm to −5 mm.   
     
     
         6 . The cold rolling method according to  claim 5 , wherein, among the plurality of stands, an (N+2)-th stand arranged in an (N+2)-th position on a downstream side of the (N+1)-th stand rolls the material to be rolled with a flat work roll having a uniform diameter of a roll. 
     
     
         7 . The cold rolling method according to  claim 1 , wherein, among the plurality of stands, a stand arranged on an uppermost stream side of the material to be rolled in the transfer direction rolls the material to be rolled with a flat work roll having a uniform diameter of a roll. 
     
     
         8 . Cold rolling equipment including a rolling mill having a plurality of stands for cold-rolling a material to be rolled,
 wherein an N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction among the plurality of stands, includes a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter, and   a linear load of the N-th stand is set as 0.8 t/mm or more.   
     
     
         9 . The cold rolling equipment according to  claim 8 , wherein, in a case where a linear load of the N-th stand is set as less than 1.4 t/mm, a tapered rolling portion width WRδ which is a length, which faces the material to be rolled, of the taper formed on the tapered work roll of the N-th stand is set as ±0 mm to +50 mm. 
     
     
         10 . The cold rolling equipment according to  claim 8 , wherein, in a case where a linear load of the N-th stand is set as 1.4 t/mm or more, a tapered rolling portion width WRδ which is a length, which faces the material to be rolled, of the taper formed on the tapered work roll of the N-th stand is set as −50 mm to −5 mm. 
     
     
         11 . The cold rolling equipment according to  claim 8 , wherein, among the plurality of stands, an (N+1)-th stand arranged in an (N+1)-th position on a downstream side of the N-th stand includes a flat work roll having a uniform diameter of a roll. 
     
     
         12 . Cold rolling equipment including a rolling mill having a plurality of stands for rolling a material to be rolled,
 wherein each of an N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction and an (N+1)-th stand arranged in an (N+1)-th position on a downstream side of the N-th stand among the plurality of stands, includes a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter, and   a linear load of each of the N-th stand and the (N+1)-th stand is set as 1.7 t/mm or more, and a tapered rolling portion width WRδ which is a length, which faces the material to be rolled, of the taper formed on the tapered work roll of each of the N-th stand and the (N+1)-th stand is set as −50 mm to −5 mm.   
     
     
         13 . The cold rolling equipment according to  claim 12 , wherein, among the plurality of stands, an (N+2)-th stand arranged in an (N+2)-th position on a downstream side of the (N+1)-th stand includes a flat work roll having a uniform diameter of a roll. 
     
     
         14 . The cold rolling equipment according to  claim 8 , wherein, among the plurality of stands, a stand arranged on an uppermost stream side of the material to be rolled in the transfer direction includes a flat work roll having a uniform diameter of a roll. 
     
     
         15 . A cold-rolled steel sheet manufacturing method comprising:
 cold-rolling a steel sheet to manufacture a cold-rolled steel sheet by the cold rolling method according to  claim 1 .