Steel sheet

Patent metadata

Field	Value
Publication number	US-11242583-B2
Application number	US-201816761724-A
Country	US
Kind code	B2
Filing date	Nov 8, 2018
Priority date	Nov 8, 2017
Publication date	Feb 8, 2022
Grant date	Feb 8, 2022

Abstract

A steel sheet includes, as a chemical composition, by mass %: C: 0.05-0.30%; Si: 0.2-2.0%; Mn: 2.0-4.0%; Al: 0.001-2.000%; P: 0.100% or less; S: 0.010% or less; N: 0.010% or less; Ti: 0-0.100%; Nb: 0-0.100%; V: 0-0.100%; Cu: 0-1.00%; Ni: 0-1.00%; Mo: 0-1.00%; Cr: 0-1.00%; W: 0-0.005%; Ca: 0-0.005%; Mg: 0-0.005%; a rare earth element (REM): 0-0.010%; B: 0-0.0030%; and a remainder of Fe and impurities, in which a metallographic structure contains, by area ratio, 95% or more of a hard structure and 0-5% of residual austenite, by mass % in a cross section in a thickness direction, C1/C2 which is a ratio of an upper limit C1 of a Mn content to a lower limit C2 of the Mn content is 1.5 or less, and a bake-hardening amount BH is 150 MPa or less.

First claim

What is claimed is:

1. A steel sheet comprising, as a chemical composition, by mass %:
C: 0.05% to 0.30%;
Si: 0.2% to 2.0%;
Mn: 2.0% to 4.0%;
Al: 0.001% to 2.000%;
P: 0.100% or less;
S: 0.010% or less;
N: 0.010% or less;
Ti: 0% to 0.100%;
Nb: 0% to 0.100%;
V: 0% to 0.100%;
Cu: 0% to 1.00%;
Ni: 0% to 1.00%;
Mo: 0% to 1.00%;
Cr: 0% to 1.00%;
W: 0% to 0.005%;
Ca: 0% to 0.005%;
Mg: 0% to 0.005%;
a rare earth element (REM): 0% to 0.010%;
B: 0% to 0.0030%; and
a remainder of Fe and impurities,
wherein a metallographic structure contains, by area ratio, 95% or more of martensite and 0% to 5% of residual austenite,
in a cross section in a thickness direction, by mass %, C1/C2 which is a ratio of an upper limit C1 of a Mn content to a lower limit C2 of the Mn content is 1.5 or less, and
a bake-hardening amount BH is 150 MPa or more.

2. The steel sheet according to claim 1 ,
wherein the chemical composition includes, by mass %, one or two or more of:
Ti: 0.003% to 0.100%;
Nb: 0.003% to 0.100%; and
V: 0.003% to 0.100%, and

a total amount of Ti, Nb, and V is 0.100% or less.

3. The steel sheet according to claim 2 ,
wherein the chemical composition includes, by mass %, one or two or more of:
Cu: 0.005% to 1.00%;
Ni: 0.005% to 1.00%;
Mo: 0.005% to 1.00%; and
Cr: 0.005% to 1.00%, and

a total amount of Cu, Ni, Mo, and Cr is 1.00% or less.

4. The steel sheet according to claim 3 ,
wherein the chemical composition includes, by mass %, one or two or more of:
W: 0.0003% to 0.005%;
Ca: 0.0003% to 0.005%;
Mg: 0.0003% to 0.005%; and
a rare earth element (REM): 0.0003% to 0.010%, and

a total amount of W, Ca, Mg, and the rare earth element (REM) is 0.010% or less.

5. The steel sheet according to claim 4 ,
wherein the chemical composition includes, by mass %:
B: 0.0001% to 0.0030%.

6. The steel sheet according to claim 3 ,
wherein the chemical composition includes, by mass %:
B: 0.0001% to 0.0030%.

7. The steel sheet according to claim 2 ,
wherein the chemical composition includes, by mass %, one or two or more of:
W: 0.0003% to 0.005%;
Ca: 0.0003% to 0.005%;
Mg: 0.0003% to 0.005%; and
a rare earth element (REM): 0.0003% to 0.010%, and

a total amount of W, Ca, Mg, and the rare earth element (REM) is 0.010% or less.

8. The steel sheet according to claim 7 ,
wherein the chemical composition includes, by mass %:
B: 0.0001% to 0.0030%.

9. The steel sheet according to claim 2 ,
wherein the chemical composition includes, by mass %:
B: 0.0001% to 0.0030%.

10. The steel sheet according to claim 1 ,
wherein the chemical composition includes, by mass %, one or two or more of:
Cu: 0.005% to 1.00%;
Ni: 0.005% to 1.00%;
Mo: 0.005% to 1.00%; and
Cr: 0.005% to 1.00%, and

a total amount of Cu, Ni, Mo, and Cr is 1.00% or less.

11. The steel sheet according to claim 10 ,
wherein the chemical composition includes, by mass %, one or two or more of:
W: 0.0003% to 0.005%;
Ca: 0.0003% to 0.005%;
Mg: 0.0003% to 0.005%; and
a rare earth element (REM): 0.0003% to 0.010%, and

a total amount of W, Ca, Mg, and the rare earth element (REM) is 0.010% or less.

12. The steel sheet according to claim 11 ,
wherein the chemical composition includes, by mass %:
B: 0.0001% to 0.0030%.

13. The steel sheet according to claim 10 ,
wherein the chemical composition includes, by mass %:
B: 0.0001% to 0.0030%.

14. The steel sheet according to claim 1 ,
wherein the chemical composition includes, by mass %, one or two or more of:
W: 0.0003% to 0.005%;
Ca: 0.0003% to 0.005%;
Mg: 0.0003% to 0.005%; and
a rare earth element (REM): 0.0003% to 0.010%, and

a total amount of W, Ca, Mg, and the rare earth element (REM) is 0.010% or less.

15. The steel sheet according to claim 14 ,
wherein the chemical composition includes, by mass %:
B: 0.0001% to 0.0030%.

16. The steel sheet according to claim 1 ,
wherein the chemical composition includes, by mass %:
B: 0.0001% to 0.0030%.

Assignees

• Nippon Steel Corp

Inventors

• Nagano Mai
• Hayashi Koutarou
• Uenishi Akihiro

Classifications

• C21D8/02

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

• C22C38/50

  with titanium or zirconium · CPC title

• C21D9/46

  for sheet metals · CPC title

• C21D1/22

  Martempering · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title