High-strength cold-rolled steel sheet

Patent metadata

Field	Value
Publication number	US-2020071784-A1
Application number	US-201715999603-A
Country	US
Kind code	A1
Filing date	Feb 15, 2017
Priority date	Feb 18, 2016
Publication date	Mar 5, 2020
Grant date	—

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

1 - 5 . (canceled)

6 . 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, 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 4.0 or less, 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.

7 . The high-strength cold-rolled steel sheet according to claim 6 , 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.

8 . The high-strength cold-rolled steel sheet according to claim 6 , wherein [Si]/[Mn]>0.4, [Si] denotes a Si content (mass %) and [Mn] denotes a Mn content (mass %).

9 . The high-strength cold-rolled steel sheet according to claim 7 , wherein [Si]/[Mn]>0.4, [Si] denotes a Si content (mass %) and [Mn] denotes a Mn content (mass %).

10 . 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 Nb: 0.2% or less, Ti: 0.2% or less, V: 0.5% or less, Mo: 0.3% or less, Cr: 1.0% or less, and B: 0.005% or less.

11 . 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 Nb: 0.2% or less, Ti: 0.2% or less, V: 0.5% or less, Mo: 0.3% or less, Cr: 1.0% or less, and B: 0.005% or less.

12 . 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 Nb: 0.2% or less, Ti: 0.2% or less, V: 0.5% or less, Mo: 0.3% or less, Cr: 1.0% or less, and B: 0.005% or less.

13 . The high-strength cold-rolled steel sheet according to claim 9 , 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, Cr: 1.0% or less, and B: 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 9 , 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.

18 . The high-strength cold-rolled steel sheet according to claim 10 , 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.

19 . The high-strength cold-rolled steel sheet according to claim 11 , 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.

20 . The high-strength cold-rolled steel sheet according to claim 12 , 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.

21 . The high-strength cold-rolled steel sheet according to claim 13 , 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.

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

• C22C38/12

  containing tungsten, tantalum, molybdenum, vanadium, or niobium · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/20

  with copper · CPC title