Steel sheet for crown cap, manufacturing method therefor, and crown cap

Abstract

A steel sheet for a crown cap has sufficient strength and formability even when the thickness thereof is reduced for use, and has a composition containing, in percent by mass, C: 0.010% to 0.025%, Si: 0.10% or less, Mn: 0.05% to 0.50%, P: 0.050% or less, S: 0.005% to 0.050%, Al: 0.020% to 0.070%, N: less than 0.0040%, and the balance being Fe and inevitable impurities, wherein yield strength after heat treatment at 210° C. for 15 minutes is as follows: the yield strength is 550 MPa or more in a rolling direction, and the yield strength in a direction 45° from the rolling direction in a rolling plane is equal to or less than the average of the yield strength in the rolling direction and the yield strength in a direction 90° from the rolling direction in the rolling plane.

1 - 4 . (canceled) 
     
     
         5 . A steel sheet for a crown cap comprising:
 a composition containing, in percent by mass, C: 0.010% to 0.025%, Si: 0.10% or less, Mn: 0.05% to 0.50%, P: 0.050% or less, S: 0.005% to 0.050%, Al: 0.020% to 0.070%, N: less than 0.0040%, and the balance being Fe and inevitable impurities, the steel sheet having a yield strength after heat treatment at 210° C. for 15 minutes, wherein 1) and 2):   1) yield strength is 550 MPa or more in a rolling direction, and   2) yield strength in a direction 45° from the rolling direction in a rolling plane is equal to or less than an average of the yield strength in the rolling direction and a yield strength in a direction 90° from the rolling direction in the rolling plane.   
     
     
         6 . A method of manufacturing the steel sheet for a crown cap according to  claim 5 , comprising:
 a hot rolling step of hot rolling a slab and coiling the hot rolled steel sheet at a coiling temperature of 530° C. to 590° C.;   a primary cold rolling step of cold rolling the hot rolled steel sheet after the hot rolling step;   an annealing step of annealing the cold rolled steel sheet at an annealing temperature of 650° C. to 720° C. after the primary cold rolling step; and   a secondary cold rolling step of performing secondary cold rolling with a rolling reduction of 25% to 40% after the annealing step.   
     
     
         7 . A crown cap comprising the steel sheet for a crown cap according to  claim 5 . 
     
     
         8 . A method of manufacturing a steel sheet for a crown cap comprising:
 a hot rolling step of hot rolling a slab having a composition containing, in percent by mass, C: 0.010% to 0.025%, Si: 0.10% or less, Mn: 0.05% to 0.50%, P: 0.050% or less, S: 0.005% to 0.050%, Al: 0.020% to 0.070%, N: less than 0.0040%, and the balance being Fe and inevitable impurities, and coiling the hot rolled steel sheet at a coiling temperature of 530° C. to 590° C.;   a primary cold rolling step of cold rolling the hot rolled steel sheet after the hot rolling step;   an annealing step of annealing the cold rolled steel sheet at an annealing temperature of 650° C. to 720° C. after the primary cold rolling step; and   a secondary cold rolling step of performing secondary cold rolling with a rolling reduction of 25% to 40% after the annealing step,   the manufactured steel sheet having a yield strength after heat treatment at 210° C. for 15 minutes, wherein 1) a yield strength of 550 MPa or more in a rolling direction, and 2) a yield strength in a direction 45° from the rolling direction in a rolling plane being equal to or less than an average of the yield strength in the rolling direction and a yield strength in a direction 90° from the rolling direction in the rolling plane.