Steel sheet for crown cap, crown cap and method for producing steel sheet for crown cap

Patent metadata

Field	Value
Publication number	US-11359255-B2
Application number	US-201816628793-A
Country	US
Kind code	B2
Filing date	Jul 25, 2018
Priority date	Jul 31, 2017
Publication date	Jun 14, 2022
Grant date	Jun 14, 2022

Abstract

A steel sheet for crown cap having: a chemical composition containing, C, Si, Mn, P, S, Al, N, with the balance being Fe and inevitable impurities; a ferrite phase in a region from a depth of ¼ of a sheet thickness to a mid-thickness part, the ferrite phase having a standard deviation of ferrite grain size of 7.0 μm or less; a yield strength of 560 MPa or more and 700 MPa or less in a rolling direction; and a difference of 25 MPa or more between a yield strength in a 2% strain tensile test and a yield strength in a tensile test after heat treatment at 170° C. for 20 minutes, in the rolling direction.

First claim

The invention claimed is:

1. A steel sheet for crown cap having a chemical composition containing, in mass %,
C: more than 0.0060% and 0.0100% or less,
Si: 0.05% or less,
Mn: 0.05% or more and 0.60% or less,
P: 0.050% or less,
S: 0.050% or less,
Al: 0.020% or more and 0.050% or less, and
N: 0.0070% or more and 0.0140% or less, with the balance being Fe and inevitable impurities, wherein
the steel sheet has a ferrite phase in a region from a depth of ¼ of a sheet thickness to a mid-thickness part, the ferrite phase having a standard deviation of ferrite grain size of 7.0 μm or less,
the steel sheet has a yield strength of 560 MPa or more and 700 MPa or less in a rolling direction, and
the steel sheet has a difference of 25 MPa or more between a yield strength in a 2% strain tensile test and a yield strength in a tensile test after heat treatment at 170° C. for 20 minutes, in the rolling direction.

2. The steel sheet for crown cap according to claim 1 having a sheet thickness of 0.20 mm or less.

3. A crown cap made of the steel sheet for crown cap according to claim 1 .

4. The crown cap according to claim 3 comprising a resin liner having an ultra-low loaded hardness of less than 0.70.

5. A method for producing the steel sheet for crown cap according to claim 1 comprising:
hot rolling a steel slab having the chemical composition according to claim 1 , whereby the steel slab is heated to a slab heating temperature of 1200° C. or higher, and then the steel slab is subjected to hot rolling under conditions of a finisher delivery temperature of 870° C. or higher and a rolling reduction at a final stand of 10% or more to obtain a steel sheet, and then the steel sheet is coiled at a coiling temperature of 550° C. to 750° C.;
after the hot rolling, pickling the steel sheet;
after the pickling, subjecting the steel sheet to primary cold rolling at a rolling reduction of 88% or more;
after the primary cold rolling, subjecting the steel sheet to continuous annealing; and
after the continuous annealing, subjecting the steel sheet to secondary cold rolling at a rolling reduction of 10% to 40%, wherein
in the continuous annealing,
the steel sheet is heated to a soaking temperature of 660° C. to 760° C. at an average heating rate of 15° C./s or less in a temperature range from 600° C. to the soaking temperature,
the steel sheet is then held in a temperature range of 660° C. to 760° C. for a holding time of 60 seconds or less,
after the holding, the steel sheet is subjected to primary cooling to a temperature of 450° C. or lower at an average cooling rate of 10° C./s or more, and
subsequently, the steel sheet is subjected to secondary cooling to a temperature of 140° C. or lower at an average cooling rate of 5° C./s or more.

6. A crown cap made of the steel sheet for crown cap according to claim 2 .

7. A method for producing the steel sheet for crown cap according to claim 2 comprising:
hot rolling a steel slab having the chemical composition according to claim 1 , whereby the steel slab is heated to a slab heating temperature of 1200° C. or higher, and then the steel slab is subjected to hot rolling under conditions of a finisher delivery temperature of 870° C. or higher and a rolling reduction at a final stand of 10% or more to obtain a steel sheet, and then the steel sheet is coiled at a coiling temperature of 550° C. to 750° C.;
after the hot rolling, pickling the steel sheet;
after the pickling, subjecting the steel sheet to primary cold rolling at a rolling reduction of 88% or more;
after the primary cold rolling, subjecting the steel sheet to continuous annealing; and
after the continuous annealing, subjecting the steel sheet to secondary cold rolling at a rolling reduction of 10% to 40%, wherein
in the continuous annealing,
the steel sheet is heated to a soaking temperature of 660° C. to 760° C. at an average heating rate of 15° C./s or less in a temperature range from 600° C. to the soaking temperature,
the steel sheet is then held in a temperature range of 660° C. to 760° C. for a holding time of 60 seconds or less,
after the holding, the steel sheet is subjected to primary cooling to a temperature of 450° C. or lower at an average cooling rate of 10° C./s or more, and
subsequently, the steel sheet is subjected to secondary cooling to a temperature of 140° C. or lower at an average cooling rate of 5° C./s or more.

Assignees

• Jfe Steel Corp

Inventors

• Kariya Nobusuke
• Ueno Takashi
• Yamamoto Yoshihide
• Kojima Katsumi
• Tateno Bungo

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C21D9/46 Primary

  for sheet metals · CPC title

• C22C38/06

  containing aluminium · CPC title

• C21D6/005

  containing Mn · CPC title

• C21D8/0236

  Cold rolling · CPC title