# US 11,111,555 B2 · Method for producing rail

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- Number: US 11,111,555 B2
- Document ID: US11111555B2
- Status: Granted
- Kind: B2
- Application number: 16/488,343
- Filed: 2018-03-20
- Published: 2020-09-03
- Granted: 2021-09-07
- Earliest claimed: 2017-03-21
- Assignees: Jfe Steel Corporation
- Applicants: Jfe Steel Corporation
- Inventors: Minoru Honjo; Tatsumi Kimura; Katsuyuki Ichimiya; Kazukuni Hase
- Web page: https://patentgrep.com/patent/US11111555B2

## CPC

- C21D 9/04: for rails
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/00: Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02)
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/22: with molybdenum or tungsten
- C22C 38/24: with vanadium
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C22C 38/42: with copper
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

A rail achieves a high 0.2% proof stress after straightening treatment, the high 0.2% proof stress being effective at improving rolling contact fatigue resistance of the rail, by hot rolling a steel raw material to obtain a rail, the steel raw material having a chemical composition containing C: 0.70% to 0.85%, Si: 0.1% to 1.5%, Mn: 0.4% to 1.5%, P: 0.035% or less, S: 0.010% or less, and Cr: 0.05% to 1.50% with the balance being Fe and inevitable impurities; straightening the rail with a load of 50 tf or more; and subsequently subjecting the rail to heat treatment in which the rail is held in a temperature range of 150° C. or more and 400° C. or less for 0.5 hours or more and 10 hours or less.

## Claims

### Claim 1

A method for producing a rail comprising:
hot rolling a steel raw material to obtain a rail, the steel raw material having a chemical composition containing, in mass %,
C: 0.70% to 0.85%,
Si: 0.1% to 1.5%,
Mn: 0.4% to 1.5%,
P: 0.035% or less,
S: 0.010% or less, and
Cr: 0.05% to 1.50% with the balance being Fe and inevitable impurities;
straightening the rail with a load of 50 tf or more; and
subsequently subjecting the rail to heat treatment in which the rail is held in a temperature range of 150° C. or more and 400° C. or less for 0.5 hours or more and 10 hours or less.

### Claim 2 (depends on 1)

The method for producing a rail according to claim 1, wherein the chemical composition further contains, in mass %, at least one selected from the group consisting of
V: 0.30% or less,
Cu: 1.0% or less,
Ni: 1.0% or less,
Nb: 0.05% or less,
Mo: 0.5% or less,
Al: 0.07% or less,
W: 1.0% or less,
B: 0.005% or less, and
Ti: 0.05% or less.