Hot-rolled steel sheet and method for manufacturing same

Patent metadata

Field	Value
Publication number	US-12448660-B2
Application number	US-202117787857-A
Country	US
Kind code	B2
Filing date	Feb 5, 2021
Priority date	Feb 6, 2020
Publication date	Oct 21, 2025
Grant date	Oct 21, 2025

Abstract

A hot-rolled steel sheet has, as a chemical composition, by mass %: C: 0.01% to 0.30%; Si: 0.01% to 3.00%; Mn: 0.20% to 3.00%; P: 0.030% or less; S: 0.030% or less; Al: 0.001% to 2.000%; N: 0.0100% or less; and Ni: 0.02% to 0.50%, in which among measurement points at which elemental analysis is performed at a measurement pitch of 1 μm using an EPMA in a region of 250 μm×250 μm on a surface, the percentage of measurement points having a Ni content of 0.5 mass % or more is 10% to 70%.

First claim

What is claimed is:

1. A hot-rolled steel sheet comprising, as a chemical composition, by mass %:
C: 0.01% to 0.30%;
Si: 0.01% to 3.00%;
Mn: 0.20% to 3.00%;
P: 0.030% or less;
S: 0.030% or less;
Al: 0.001% to 2.000%;
N: 0.0100% or less;
Ni: 0.02% to 0.50%;
Nb: 0% to 0.060%;
V: 0% to 0.20%;
Ti: 0% to 0.20%;
Cu: 0% to 0.20%;
Cr: 0% to 0.20%;
Mo: 0% to 1.00%;
B: 0% to 0.0020%;
W: 0% to 0.50%;
Mg: 0% to 0.010%;
Ca: 0% to 0.0100%;
REM: 0% to 0.0100%;
O: 0% to 0.0100%;
Zr: 0% to 0.500%;
Co: 0% to 0.500%;
Zn: 0% to 0.500%;
Sn: 0% to 0.500%; and
a remainder consisting of Fe and impurities,
wherein among measurement points at which elemental analysis is performed at a measurement pitch of 1 μm using an Electron Probe Micro Analyzer in a region of 250 μm×250 μm on a surface, a percentage of measurement points having a Ni content of 0.5 mass % or more is 10% to 70%.

2. The hot-rolled steel sheet according to claim 1 ,
wherein the chemical composition contains one or two or more selected from:
Nb: 0.003% to 0.060%,
V: 0.01% to 0.20%,
Ti: 0.01% to 0.20%,
Cu: 0.01% to 0.20%,
Cr: 0.01% to 0.20%,
Mo: 0.01% to 1.00%,
B: 0.0005% to 0.0020%,
W: 0.01% to 0.50%,
Mg: 0.001% to 0.010%,
Ca: 0.0010% to 0.0100%,
REM: 0.0010% to 0.0100%, and
O: 0.0005% to 0.0100%.

3. The hot-rolled steel sheet according to claim 2 ,
wherein the chemical composition contains
Si: 0.50% to 3.00%.

4. The hot-rolled steel sheet according to claim 2 ,
wherein the chemical composition contains
Si: 0.01% or more and less than 0.50%, and
Al: 0.050% to 2.000%.

5. The hot-rolled steel sheet according to claim 2 ,
wherein the chemical composition contains
Si: 0.01% or more and less than 0.50%, and
Al: 0.001% or more and less than 0.050%, and
a total of Si and Al is 0.50% or more and less than 0.55%.

6. The hot-rolled steel sheet according to claim 3 ,
wherein among the measurement points at which the elemental analysis is performed on the surface, a percentage of measurement points having an O content of 0.5 mass % or more is 30% or less.

7. The hot-rolled steel sheet according to claim 4 ,
wherein among the measurement points at which the elemental analysis is performed on the surface, a percentage of measurement points having an O content of 0.5 mass % or more is 30% or less.

8. The hot-rolled steel sheet according to claim 5 ,
wherein among the measurement points at which the elemental analysis is performed on the surface, a percentage of measurement points having an O content of 0.5 mass % or more is 30% or less.

9. The hot-rolled steel sheet according to claim 1 ,
wherein the chemical composition contains
Cu: 0.01% to 0.20%, and
Ni/Cu is 0.50 or more.

10. The hot-rolled steel sheet according to claim 1 ,
wherein among the measurement points at which the elemental analysis is performed on the surface, an average interval between the measurement points having a Ni content of 0.5 mass % or more is 3 to 10 μm.

11. The hot-rolled steel sheet according to claim 1 ,
wherein the surface has a rust preventive oil film.

12. The hot-rolled steel sheet according to claim 1 ,
wherein the surface has a chemical conversion film.

13. The hot-rolled steel sheet according to claim 2 ,
wherein the chemical composition contains
Cu: 0.01% to 0.20%, and
Ni/Cu is 0.50 or more.

14. The hot-rolled steel sheet according to claim 3 ,
wherein the chemical composition contains
Cu: 0.01% to 0.20%, and
Ni/Cu is 0.50 or more.

15. The hot-rolled steel sheet according to claim 4 ,
wherein the chemical composition contains
Cu: 0.01% to 0.20%, and
Ni/Cu is 0.50 or more.

16. The hot-rolled steel sheet according to claim 5 ,
wherein the chemical composition contains
Cu: 0.01% to 0.20%, and
Ni/Cu is 0.50 or more.

17. The hot-rolled steel sheet according to claim 6 ,
wherein the chemical composition contains
Cu: 0.01% to 0.20%, and
Ni/Cu is 0.50 or more.

18. The hot-rolled steel sheet according to claim 7 ,
wherein the chemical composition contains
Cu: 0.01% to 0.20%, and
Ni/Cu is 0.50 or more.

19. A method for manufacturing a hot-rolled steel sheet comprising:
heating a steel piece having the chemical composition according to claim 1 in a heating furnace;
descaling the heated steel piece; and
hot-rolling the steel piece after the descaling to obtain a hot-rolled steel sheet,
wherein in the heating,
after a surface temperature of the steel piece reaches 1,100° C. or higher, the steel piece is held for 60 minutes or longer under an atmosphere having an air ratio of 0.9 or more, and
an extraction temperature is 1,180° C. or higher, and in the descaling,
the steel piece of which the surface temperature is 1,170° C. or higher is descaled at least once with an injection pressure of 5 to 50 MPa, and
the surface temperature of the steel piece is held at 1,100° C. or higher for 20 to 240 seconds after completion of the descaling.

20. A hot-rolled steel sheet comprising, as a chemical composition, by mass %:
C: 0.01% to 0.30%;
Si: 0.01% to 3.00%;
Mn: 0.20% to 3.00%;
P: 0.030% or less;
S: 0.030% or less;
Al: 0.001% to 2.000%;
N: 0.0100% or less;
Ni: 0.02% to 0.50%;
Nb: 0% to 0.060%;
V: 0% to 0.20%;
Ti: 0% to 0.20%;
Cu: 0% to 0.20%;
Cr: 0% to 0.20%;
Mo: 0% to 1.00%;
B: 0% to 0.0020%;
W: 0% to 0.50%;
Mg: 0% to 0.010%;
Ca: 0% to 0.0100%;
REM: 0% to 0.0100%;
O: 0% to 0.0100%;
Zr: 0% to 0.500%;
Co: 0% to 0.500%;
Zn: 0% to 0.500%;
Sn: 0% to 0.500%; and
a remainder comprising Fe and impurities,
wherein among measurement points at which elemental analysis is performed at a measurement pitch of 1 μm using an Electron Probe Micro Analyzer in a region of 250 μm×250 μm on a surface, a percentage of measurement points having a Ni content of 0.5 mass % or more is 10% to 70%.

Assignees

• Nippon Steel Corp

Inventors

• Ando Jun
• Hayashida Teruki
• Yokoi Tatsuo
• Sakakibara Akifumi

Classifications

• C21D8/02

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

• C22C38/08

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

• C22C38/06

  containing aluminium · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/02 Primary

  containing silicon · CPC title