Rail and method for manufacturing same

Patent metadata

Field	Value
Publication number	US-11530471-B2
Application number	US-201917040539-A
Country	US
Kind code	B2
Filing date	Mar 28, 2019
Priority date	Mar 30, 2018
Publication date	Dec 20, 2022
Grant date	Dec 20, 2022

Abstract

The rail having a chemical composition containing C: 0.70-0.85 mass %, Si: 0.50-1.60 mass %, Mn: 0.20-1.00 mass %, P: 0.035 mass % or less, S: 0.012 mass % or less, Cr: 0.40-1.30 mass %, the chemical composition satisfying the formula (1)

0.30≤[% Si]/10+[% Mn]/6+[% Cr]/3≤0.55  (1)
where [% M] is the content in mass % of the element M,

the balance being Fe and inevitable impurities, where Vickers hardness of a region between positions where a depth from a surface of a rail head of 0.5 and 25 mm is ≥370 HV and <520 HV, a total area ratio of a pearlite microstructure and a bainite microstructure in the region is ≥98%, and an area ratio of the bainite microstructure in the region is >5% and <20%.

First claim

The invention claimed is:

1. A rail comprising a chemical composition containing
C: 0.70 mass % or more and 0.85 mass % or less,
Si: 0.79 mass % or more and 1.20 mass % or less,
Mn: 0.20 mass % or more and 1.00 mass % or less,
P: 0.035 mass % or less,
S: 0.012 mass % or less,
Cr: 0.40 mass % or more and 1.30 mass % or less, and
at least one selected from the group consisting of
Nb: 0.017 mass % or more and 0.05 mass % or less,
Al: 0.015 mass % or more and 0.07 mass % or less, and
Ti: 0.02 mass % or more and 0.05 mass % or less,

where the chemical composition satisfies the following formula (1)
0.30≤[% Si]/10+[% Mn]/6+[% Cr]/3≤0.55  (1)

where [% M] is the content in mass % of the element M in the chemical composition, the balance being Fe and inevitable impurities, wherein

Vickers hardness of a region between a position where a depth from a surface of a rail head is 0.5 mm and a position where the depth is 25 mm is 370 HV or more and less than 520 HV, a total area ratio of a pearlite microstructure and a bainite microstructure in the region is 98% or more, and an area ratio of the bainite microstructure in the region is more than 5% and less than 20%.

2. The rail according to claim 1 , wherein the chemical composition further contains at least one selected from the group consisting of
V: 0.30 mass % or less,
Cu: 1.0 mass % or less,
Ni: 1.0 mass % or less, and
Mo: 0.5 mass % or less.

3. The rail according to claim 1 , wherein the chemical composition further contains at least one selected from the group consisting of
W: 1.0 mass % or less,
B: 0.005 mass % or less, and
Sb: 0.05 mass % or less.

4. The rail according to claim 2 , wherein the chemical composition further contains at least one selected from the group consisting of
W: 1.0 mass % or less,
B: 0.005 mass % or less, and
Sb: 0.05 mass % or less.

5. A method of manufacturing a rail, comprising subjecting a steel material having the chemical composition according to claim 1 to hot rolling where a finish temperature is 850° C. or higher and 950° C. or lower, then to cooling where a cooling start temperature is equal to or higher than a pearlite transformation start temperature, a cooling stop temperature is 350° C. or higher and 600° C. or lower, and a cooling rate is 2° C./s or higher and 10° C./s or lower; thereby producing the rail according to claim 1 .

6. A method of manufacturing a rail, comprising subjecting a steel material having the chemical composition according to claim 2 to hot rolling where a finish temperature is 850° C. or higher and 950° C. or lower, then to cooling where a cooling start temperature is equal to or higher than a pearlite transformation start temperature, a cooling stop temperature is 350° C. or higher and 600° C. or lower, and a cooling rate is 2° C./s or higher and 10° C./s or lower; thereby producing the rail according to claim 2 .

7. A method of manufacturing a rail, comprising subjecting a steel material having the chemical composition according to claim 3 to hot rolling where a finish temperature is 850° C. or higher and 950° C. or lower, then to cooling where a cooling start temperature is equal to or higher than a pearlite transformation start temperature, a cooling stop temperature is 350° C. or higher and 600° C. or lower, and a cooling rate is 2° C./s or higher and 10° C./s or lower; thereby producing the rail according to claim 3 .

8. A method of manufacturing a rail, comprising subjecting a steel material having the chemical composition according to claim 4 to hot rolling where a finish temperature is 850° C. or higher and 950° C. or lower, then to cooling where a cooling start temperature is equal to or higher than a pearlite transformation start temperature, a cooling stop temperature is 350° C. or higher and 600° C. or lower, and a cooling rate is 2° C./s or higher and 10° C./s or lower; thereby producing the rail according to claim 4 .

Assignees

• Jfe Steel Corp

Inventors

• Ando Keisuke
• Kimura Tatsumi
• Igi Satoshi

Classifications

• C21D9/04

  for rails · CPC title

• C21D6/005

  containing Mn · CPC title

• C21D2211/009

  Pearlite · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/18

  containing chromium · CPC title