High-strength cold-rolled steel sheet

Patent metadata

Field	Value
Publication number	US-11085099-B2
Application number	US-201715999603-A
Country	US
Kind code	B2
Filing date	Feb 15, 2017
Priority date	Feb 18, 2016
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

Abstract

A high-strength cold-rolled steel sheet has a composition that contains, in terms of mass %, C: 0.10% or more and 0.50% or less, Si: 1.0% or more and 3.0% or less, Mn: 1.0% or more and 2.5% or less, P: 0.05% or less, S: 0.02% or less, Al: 0.01% or more and 1.5% or less, N: 0.005% or less, Cu: 0.05% or more and 0.50% or less, and the balance being Fe and unavoidable impurities, wherein a proportion of a steel sheet surface covered with oxides mainly composed of Si is 1% or less, a proportion of the steel sheet surface covered with Fe oxides is 40% or less, CuS/CuB is 4.0 or less, and a tensile strength is 1180 MPa or more, when CuS denotes the Cu content in a steel sheet surface layer and CuB denotes the Cu content in a base material.

First claim

The invention claimed is:

1. A high-strength cold-rolled steel sheet comprising:
a composition that contains, in terms of mass %,
C: 0.10% or more and 0.50% or less,
Si: 1.0% or more and 3.0% or less,
Mn: 1.0% or more and 2.5% or less,
P: 0.05% or less,
S: 0.02% or less,
Al: 0.01% or more and 1.5% or less,
N: 0.005% or less,
Cu: 0.05% or more and 0.50% or less,
Cr: 1.0% or less, and
the balance being Fe and unavoidable impurities,
wherein a proportion of a steel sheet surface covered with oxides mainly composed of Si is 1% or less, a proportion of the steel sheet surface covered with Fe oxides is 40% or less, Cu S /Cu B is 2.0 to 4.0, and a tensile strength is 1180 MPa or more, where Cu S denotes a Cu content in a steel sheet surface layer and Cu B denotes a Cu content in a base material.

2. The high-strength cold-rolled steel sheet according to claim 1 , further comprising a steel sheet structure containing 40% or more and 100% or less of at least one selected from martensite and bainite in terms of volume fraction, 0% or more and 60% or less of ferrite in terms of volume fraction, and 0% or more and 20% or less of retained austenite.

3. The high-strength cold-rolled steel sheet according to claim 1 , wherein [Si]/[Mn]>0.4, [Si] denotes a Si content (mass %) and [Mn] denotes a Mn content (mass %).

4. The high-strength cold-rolled steel sheet according to claim 2 , wherein [Si]/[Mn]>0.4, [Si] denotes a Si content (mass %) and [Mn] denotes a Mn content (mass %).

5. The high-strength cold-rolled steel sheet according to claim 1 , wherein the composition further contains, in terms of mass %, at least one selected from Nb: 0.2% or less, Ti: 0.2% or less, V: 0.5% or less, Mo: 0.3% or less, and B: 0.005% or less.

6. The high-strength cold-rolled steel sheet according to claim 2 , wherein the composition further contains, in terms of mass %, at least one selected from Nb: 0.2% or less, Ti: 0.2% or less, V: 0.5% or less, Mo: 0.3% or less, and B: 0.005% or less.

7. The high-strength cold-rolled steel sheet according to claim 3 , wherein the composition further contains, in terms of mass %, at least one selected from Nb: 0.2% or less, Ti: 0.2% or less, V: 0.5% or less, Mo: 0.3% or less, and B: 0.005% or less.

8. The high-strength cold-rolled steel sheet according to claim 4 , wherein the composition further contains, in terms of mass %, at least one selected from Nb: 0.2% or less, Ti: 0.2% or less, V: 0.5% or less, Mo: 0.3% or less, and B: 0.005% or less.

9. The high-strength cold-rolled steel sheet according to claim 1 , wherein the composition further contains, in terms of mass %, at least one selected from Sn: 0.1% or less, Sb: 0.1% or less, W: 0.1% or less, Co: 0.1% or less, Ca: 0.005% or less, and REM: 0.005% or less.

10. The high-strength cold-rolled steel sheet according to claim 2 , wherein the composition further contains, in terms of mass %, at least one selected from Sn: 0.1% or less, Sb: 0.1% or less, W: 0.1% or less, Co: 0.1% or less, Ca: 0.005% or less, and REM: 0.005% or less.

11. The high-strength cold-rolled steel sheet according to claim 3 , wherein the composition further contains, in terms of mass %, at least one selected from Sn: 0.1% or less, Sb: 0.1% or less, W: 0.1% or less, Co: 0.1% or less, Ca: 0.005% or less, and REM: 0.005% or less.

12. The high-strength cold-rolled steel sheet according to claim 4 , wherein the composition further contains, in terms of mass %, at least one selected from Sn: 0.1% or less, Sb: 0.1% or less, W: 0.1% or less, Co: 0.1% or less, Ca: 0.005% or less, and REM: 0.005% or less.

13. The high-strength cold-rolled steel sheet according to claim 5 , wherein the composition further contains, in terms of mass %, at least one selected from Sn: 0.1% or less, Sb: 0.1% or less, W: 0.1% or less, Co: 0.1% or less, Ca: 0.005% or less, and REM: 0.005% or less.

14. The high-strength cold-rolled steel sheet according to claim 6 , wherein the composition further contains, in terms of mass %, at least one selected from Sn: 0.1% or less, Sb: 0.1% or less, W: 0.1% or less, Co: 0.1% or less, Ca: 0.005% or less, and REM: 0.005% or less.

15. The high-strength cold-rolled steel sheet according to claim 7 , wherein the composition further contains, in terms of mass %, at least one selected from Sn: 0.1% or less, Sb: 0.1% or less, W: 0.1% or less, Co: 0.1% or less, Ca: 0.005% or less, and REM: 0.005% or less.

16. The high-strength cold-rolled steel sheet according to claim 8 , wherein the composition further contains, in terms of mass %, at least one selected from Sn: 0.1% or less, Sb: 0.1% or less, W: 0.1% or less, Co: 0.1% or less, Ca: 0.005% or less, and REM: 0.005% or less.

17. The high-strength cold-rolled steel sheet according to claim 1 , the Cu content is 0.11% to 0.45% and the Si content is 1.2 to 2.0%.

Assignees

• Jfe Steel Corp

Inventors

• Yoshioka Shimpei
• Ono Yoshihiko
• Masuoka Hiroyuki

Classifications

• C21D8/02

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

• C21D8/0236 Primary

  Cold rolling · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/02 Primary

  containing silicon · CPC title

• C22C38/001

  containing N · CPC title