High-strength steel sheet excellent in seam weldability

Patent metadata

Field	Value
Publication number	US-10030291-B2
Application number	US-201213547713-A
Country	US
Kind code	B2
Filing date	Jul 12, 2012
Priority date	Aug 10, 2011
Publication date	Jul 24, 2018
Grant date	Jul 24, 2018

Abstract

Disclosed is a high-strength steel sheet having a tensile strength of 1180 MPa or more and having satisfactory seam weldability. The steel sheet has a chemical composition of C: 0.12% to 0.40%, Si: 0.003% to 0.5%, Mn 0.01% to 1.5%, Al: 0.032% to 0.15%, N: 0.01% or less, P: 0.02% or less, S: 0.01% or less, Ti: 0.01% to 0.2% or less, and B: 0.0001% to 0.01%, with the remainder including iron and inevitable impurities, has a Ceq1 (=C+Mn/5+Si/13) of 0.50% or less, and has a steel structure of a martensite single-phase structure.

First claim

What is claimed is:

1. A steel sheet, the steel sheet having a chemical composition comprising by mass percent:
carbon (C) in a content of from 0.20% to 0.40%,
silicon (Si) in a content of from 0.003% to 0.021%,
manganese (Mn) in a content of from 1.01% to 1.5%,
aluminum (Al) in a content of from 0.032% to 0.15%,
nitrogen (N) in a content of 0.008% or less,
phosphorus (P) in a content of 0.02% or less,
sulfur (S) in a content of 0.01% or less,
titanium (Ti) in a content of from 0.05% to 0.2%, and
boron (B) in a content of from 0.0001% to 0.01%,
with the remainder comprising iron and inevitable impurities,
the steel sheet having a Ceq1 expressed by following Equation (1) of 0.44% or less,
the steel sheet having a steel structure including 94 percent by area or more of a martensite structure, and
the steel sheet having a tensile strength of 1180 MPa or more:
C eq 1=C+Mn/5+Si/13  (1)

wherein symbols “C”, “Mn”, and “Si” represent the carbon content by mass percent, the manganese content by mass percent, and the silicon content by mass percent, respectively, in the steel.

2. The steel sheet according to claim 1 ,
wherein the steel sheet has a Ceq2 expressed by following Equation (2) of 0.43% or less:
C eq 2=C+Mn/7.5  (2)

wherein symbols “C” and “Mn” represent the carbon content by mass percent and the manganese content by mass percent, respectively, in the steel.

3. The steel sheet according to claim 1 ,
further comprising chromium (Cr) in a content of from 0.01% to 2.0%.

4. The steel sheet according to claim 1 ,
further comprising at least one of copper (Cu) in a content of from 0.01% to 0.5% and Ni in a content of from 0.01% to 0.5%.

5. The steel sheet according to claim 1 ,
further comprising at least one of vanadium (V) in a content of from 0.003% to 0.1% and niobium (Nb) in a content of from 0.003% to 0.1%.

6. A hot-dip galvanized steel sheet comprising:
the steel sheet of claim 1 ; and
a hot-dip galvanized coating formed on the steel sheet through hot-dip galvanization.

7. A hot-dip galvannealed steel sheet comprising:
the steel sheet of claim 1 ; and
a hot-dip galvannealed coating formed on the steel sheet through hot-dip galvanization and subsequent alloying.

8. The steel sheet according to claim 1 , wherein the carbon (C) content is from 0.223% to 0.323%, the silicon (Si) content is from 0.012% to 0.021%, and the manganese (Mn) content is from 1.01% to 1.46%.

9. The steel sheet of claim 1 , having thickness of from 1.0 mm to 3.2 mm.

10. The steel sheet of claim 1 , wherein the steel sheet is a cold rolled steel sheet, a hot-dip galvanized steel sheet, or a hot-dip galvannealed steel sheet.

11. A steel sheet, the steel sheet having a chemical composition comprising by mass percent:
carbon (C) in a content of from 0.223% to 0.323%,
silicon (Si) in a content of from 0.012% to 0.031%,
manganese (Mn) in a content of from 1.01% to 1.46%,
aluminum (Al) in a content of from 0.032% to 0.15%,
nitrogen (N) in a content of 0.008% or less,
phosphorus (P) in a content of 0.02% or less,
sulfur (S) in a content of 0.01% or less,
titanium (Ti) in a content of from 0.05% to 0.2%, and
boron (B) in a content of from 0.0001% to 0.01%,
with the remainder comprising iron and inevitable impurities,
the steel sheet having a Ceq1 expressed by following Equation (1) of 0.48% or less,
the steel sheet having a steel structure including 94 percent by area or more of a martensite structure, and
the steel sheet having a tensile strength of 1180 MPa or more:
C eq 1=C+Mn/5+Si/13  (1)

wherein symbols “C”, “Mn”, and “Si” represent the carbon content by mass percent, the manganese content by mass percent, and the silicon content by mass percent, respectively, in the steel.

12. The steel sheet according to claim 11 ,
wherein the steel sheet has a Ceq2 expressed by following Equation (2) of 0.43% or less:
C eq 2=C+Mn/7.5  (2)

wherein symbols “C” and “Mn” represent the carbon content by mass percent and the manganese content by mass percent, respectively, in the steel.

13. The steel sheet according to claim 11 ,
further comprising chromium (Cr) in a content of from 0.01% to 2.0%.

14. The steel sheet according to claim 11 ,
further comprising at least one of copper (Cu) in a content of from 0.01% to 0.5% and Ni in a content of from 0.01% to 0.5%.

15. The steel sheet according to claim 11 ,
further comprising at least one of vanadium (V) in a content of from 0.003% to 0.1% and niobium (Nb) in a content of from 0.003% to 0.1%.

16. A hot-dip galvanized steel sheet comprising:
the steel sheet of claim 11 ; and
a hot-dip galvanized coating formed on the steel sheet through hot-dip galvanization.

17. A hot-dip galvannealed steel sheet comprising:
the steel sheet of claim 11 ; and
a hot-dip galvannealed coating formed on the steel sheet through hot-dip galvanization and subsequent alloying.

18. The steel sheet of claim 11 , wherein the steel sheet is a cold rolled steel sheet, a hot-dip galvanized steel sheet, or a hot-dip galvannealed steel sheet.

19. A steel sheet, the steel sheet having a chemical composition consisting of by mass percent:
carbon (C) in a content of from 0.20% to 0.40%,
silicon (Si) in a content of from 0.003% to 0.032%,
manganese (Mn) in a content of more than 0.8% to 1.5%,
aluminum (Al) in a content of from 0.032% to 0.15%,
nitrogen (N) in a content of 0.008% or less,
phosphorus (P) in a content of 0.02% or less,
sulfur (S) in a content of 0.01% or less,
titanium (Ti) in a content of from 0.01% to 0.2%, and
boron (B) in a content of from 0.0001% to 0.01%, and optionally
at least one selected from the group consisting of Cr, Cu, Ni, and V, wherein chromium (Cr) when present has a content of from 0.01% to 2.0%, copper (Cu) when present has a content of from 0.01% to 0.5%, nickel (Ni) when present has a content of from 0.01% to 0.5%, and vanadium (V) when present has a content of from 0.003% to 0.1%,
with the remainder consisting of iron and inevitable impurities,
the steel sheet having a Ceq1 expressed by following Equation (1) of 0.44% or less,
the steel sheet having a steel structure including 97 percent by area or more of a martensite structure, and
the steel sheet having a tensile strength of 1180 MPa or more:
C eq 1=C+Mn/5+Si/13  (1)

wherein symbols “C”, “Mn”, and “Si” represent the carbon content by mass percent, the manganese content by mass percent, and the silicon content by mass percent, respectively, in the steel.

20. A hot-dip galvanized steel sheet comprising:
the steel sheet of claim 19 ; and
a hot-dip galvanized coating formed on the steel sheet through hot-dip galvanization.

21. A hot-dip galvannealed steel sheet comprising:
the steel sheet of claim 19 ; and
a hot-dip galvannealed coating formed on the steel sheet through hot-dip galvanization and subsequent alloying.

22. A The steel sheet of claim 19 , having thickness of from 1.0 mm to 3.2 mm.

23. The steel sheet of claim 19 , wherein the steel sheet is a cold rolled steel sheet, a hot-dip galvanized steel sheet, or a hot-dip galvannealed steel sheet.

Assignees

• Shiraki Atsuhiro
• Utsumi Yukihiro
• Kobe Steel Ltd

Inventors

• Shiraki Atsuhiro
• Utsumi Yukihiro

Classifications

• C21D8/02

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

• C21D2211/008

  Martensite · CPC title

• C23C2/06

  Zinc or cadmium or alloys based thereon · CPC title

• C22C38/08

  containing nickel {(C22C38/105 takes precedence)} · CPC title

• C22C38/12

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