Method for manufacturing a rail and corresponding rail

Patent metadata

Field	Value
Publication number	US-12365957-B2
Application number	US-201816767105-A
Country	US
Kind code	B2
Filing date	Nov 27, 2018
Priority date	Nov 27, 2017
Publication date	Jul 22, 2025
Grant date	Jul 22, 2025

Abstract

A method for manufacturing a rail includes casting a steel to obtain a semi-product. The steel has a composition comprising 0.20%≤C≤0.60%, 1.0%≤Si≤2.0%, 0.60%≤Mn≤ 1.60% and 0.5≤Cr≤2.2%, optionally 0.01%≤Mo≤0.3%, 0.01%≤V≤0.30%; the remainder being Fe and impurities. The method also includes hot rolling the semi-product into a hot rolled semi-product having the shape of the rail and comprising a head, with a final rolling temperature T FRT higher than Ar3; and cooling the head to a cooling stop temperature T CS between 200° C. and 520° C. The method also includes maintaining the head in a temperature range comprised between 300° C. and 520° C. during a holding time t hold of at least 12 minutes, and; cooling down the hot rolled semi-product to room temperature to obtain the rail.

First claim

The invention claimed is:

1. A steel rail, made of a steel having a chemical composition comprising, by weight percent:
0.20%≤C≤0.60%,
1.0%≤Si≤2.0%,
0.60%≤Mn<1.5%,
and 0.5%≤Cr≤2.2%,
and optionally one or more elements chosen among
0.01%≤Mo≤0.3%,
0.01%≤V≤0.30%;
a remainder being Fe and unavoidable impurities resulting from smelting;

the steel rail comprising a head having a microstructure consisting of, in area fraction:
49% to 67% of bainite,
14% to 25% of retained austenite, the retained austenite having an average carbon content comprised between 1.3% and 1.44%,
13% to 34% of tempered martensite,
wherein the head of the rail has a tensile strength comprised between 1300 MPa and 1452 MPa, a yield strength of at least 1000 MPa, a total elongation of at least 13%, and a hardness in a rolling surface of the head of at least 420 HB.

2. The steel rail according to claim 1 , wherein the area fraction of bainite in the microstructure of the head of the rail consists of between 56% and 67%.

3. The steel rail according to claim 1 , wherein the area fraction of retained austenite in the microstructure of the head of the rail consists of between 18% and 23%.

4. The steel rail according to claim 1 , wherein the area fraction of tempered martensite in the microstructure of the head of the rail consists of between 14.5% and 22.5%.

5. The steel rail according to claim 1 , wherein the chemical composition of the steel comprises, by weight percent, 0.30%≤C≤0.6%.

6. The steel rail according to claim 1 , wherein the chemical composition of the steel comprises, by weight percent, 1.25%≤Si≤1.6%.

7. The steel rail according to claim 1 , wherein the chemical composition of the steel comprises, by weight percent, 0.9%≤Mn<1.5%.

8. The steel rail according to claim 1 , wherein the head of the rail has a hardness in the rolling surface of the head comprised between 420 HB and 470 HB.

9. The steel rail according to claim 8 , wherein the head of the rail has a hardness in the rolling surface of the head comprised between 450 HB and 470 HB.

10. The steel rail according to claim 1 , wherein the head of the rail has a tensile strength comprised between 1300 MPa and 1450 MPa.

11. The steel rail according to claim 1 , wherein the head of the rail has a yield strength comprised between 1000 MPa and 1150 MPa.

12. The steel rail according to claim 1 , wherein the head of the rail has a total elongation comprised between 13% and 18%.

13. The steel rail according to claim 1 , wherein the chemical composition of the steel comprises, by weight percent, 1.97%≤Cr≤2.2%.

14. A steel rail, made of a steel having a chemical composition comprising, by weight percent:
0.20%≤C≤0.60%,
1.0%≤Si≤2.0%,
0.60%≤Mn≤1.60%,
and 1.97%≤Cr≤2.2%,
and optionally one or more elements chosen among
0.01%≤Mo≤0.3%,
0.01%≤V≤0.30%;
a remainder being Fe and unavoidable impurities resulting from smelting;

the steel rail comprising a head having a microstructure consisting of, in area fraction:
49% to 67% of bainite,
14% to 25% of retained austenite, the retained austenite having an average carbon content comprised between 1.3% and 1.44%,
13% to 34% of tempered martensite,
wherein the head of the rail has a tensile strength comprised between 1300 MPa and 1452 MPa, a yield strength of at least 1000 MPa, a total elongation of at least 13%, and a hardness in a rolling surface of the head of at least 420 HB.

15. The steel rail according to claim 14 , wherein the chemical composition of the steel comprises, by weight percent, 0.9%≤Mn≤1.5%.

16. The steel rail according to claim 14 , wherein the area fraction of bainite in the microstructure of the head of the rail consists of between 56% and 67%.

17. The steel rail according to claim 14 , wherein the area fraction of retained austenite in the microstructure of the head of the rail consists of between 18% and 23%.

18. The steel rail according to claim 14 , wherein the area fraction of tempered martensite in the microstructure of the head of the rail consists of between 14.5% and 22.5%.

19. An uncoated steel rail, made of a steel having a chemical composition comprising, by weight percent:
0.20%≤C≤0.60%,
1.0%≤Si≤2.0%,
either 0.60%≤Mn<1.5% and 0.5%≤Cr≤2.2%,
or 0.60%≤Mn≤1.60% and 1.97%≤Cr≤2.2%,

and optionally one or more elements chosen among
0.01%≤Mo≤0.3%,
0.01%≤V≤0.30%;
a remainder being Fe and unavoidable impurities resulting from smelting;

the steel rail comprising a head having a microstructure consisting of, in area fraction:
49% to 67% of bainite,
14% to 25% of retained austenite, the retained austenite having an average carbon content comprised between 1.3% and 1.44%,
13% to 34% of tempered martensite,
wherein the head of the rail has a tensile strength of at least 1300 MPa, a yield strength of at least 1000 MPa, a total elongation of at least 13%, and a hardness in a rolling surface of the head of at least 420 HB.

Assignees

• Arcelormittal

Inventors

• Arancon Alvarez José
• Alvarez Diez David
• Artimez Encina José Manuel
• Garcia Caballero Francisca
• Pohu Benjamin

Classifications

• C22C38/22

  with molybdenum or tungsten · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/002

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

• C22C38/001

  containing N · CPC title