Rail and method of manufacturing rail

Patent metadata

Field	Value
Publication number	US-12264373-B2
Application number	US-201917271266-A
Country	US
Kind code	B2
Filing date	Aug 21, 2019
Priority date	Sep 10, 2018
Publication date	Apr 1, 2025
Grant date	Apr 1, 2025

Abstract

According to one aspect of the present invention, what is provided is a rail including, by mass %: C: 0.75% to 1.20%; Si: 0.10% to 2.00%; Mn: 0.10% to 2.00%; Cr: 0.10% to 1.20%; V: 0.010% to 0.200%; N: 0.0030% to 0.0200%; P≤0.0250%; S≤0.0250%; Mo: 0% to 0.50%, Co: 0% to 1.00%; B: 0% to 0.0050%; Cu: 0% to 1.00%; Ni: 0% to 1.00%; Nb: 0% to 0.0500%; Ti: 0% to 0.0500%; Mg: 0% to 0.0200%; Ca: 0% to 0.0200%; REM: 0% to 0.0500%; Zr: 0% to 0.0200%; Al: 0% to 1.00%; and a remainder consisting of Fe and impurities, in which a structure ranging from an outer surface of a head portion as an origin to a depth of 25 mm includes 95% or greater of a pearlite structure by area ratio, the hardness of the structure is in a range of Hv 360 to 500, and in ferrite of the pearlite structure at a position at a depth of 25 mm from the outer surface of the head portion as the origin, the number density of a V nitride having a grain size of 0.5 to 4.0 nm and including Cr is in a range of 1.0×10 17 to 5.0×10 17 cm −3 .

First claim

What is claimed is:

1. A rail comprising, by mass %:
C: 0.75% to 1.20%;
Si: 0.10% to 2.00%;
Mn: 0.10% to 2.00%;
Cr: 0.10% to 1.20%;
V: 0.010% to 0.200%;
N: 0.0030% to 0.0200%;
P≤0.0250%;
S≤0.0250%;
Mo: 0% to 0.50%;
Co: 0% to 1.00%;
B: 0% to 0.0050%;
Cu: 0% to 1.00%;
Ni: 0% to 1.00%;
Nb: 0% to 0.0500%;
Ti: 0% to 0.0500%;
Mg: 0% to 0.0200%;
Ca: 0% to 0.0200%;
REM: 0% to 0.0500%;
Zr: 0% to 0.0200%;
Al: 0% to 1.00%; and
a remainder including Fe and impurities, wherein
a structure ranging from an outer surface of a head portion as an origin to a depth of 25 mm includes 95% or greater of a pearlite structure by area ratio,
a hardness of the structure is in a range of Hv 360 to 500, and
in ferrite of the pearlite structure at a position at the depth of 25 mm from the outer surface of the head portion as the origin, a number density of a V nitride having a grain size of 0.5 to 4.0 nm and including Cr is in a range of 1.0×10 17 to 5.0×10 17 cm −3 .

2. The rail according to claim 1 ,
wherein in the V nitride having the grain size of 0.5 to 4.0 nm and including Cr in the ferrite of the pearlite structure at a position at the depth of 25 mm from the outer surface of the head portion, when the number of V atoms is represented by VA and the number of Cr atoms is represented by CA, an average value of CA/VA satisfies the following Expression 1,
0.01≤average value of CA/VA≤ 0.70  Expression 1.

3. The rail according to claim 1 , comprising, by mass %, one or more groups selected from the group consisting of:
a group a: Mo: 0.01% to 0.50%;
a group b: Co: 0.01% to 1.00%;
a group c: B: 0.0001% to 0.0050%;
a group d: one or two selected from Cu: 0.01% to 1.00% and Ni: 0.01% to 1.00%;
a group e: one or more selected from Nb: 0.0010% to 0.0500% and Ti: 0.0030% to 0.0500%;
a group f: one or more selected from Mg: 0.0005% to 0.0200%, Ca: 0.0005% to 0.0200%, and REM: 0.0005% to 0.0500%;
a group g: Zr: 0.0001% to 0.0200%; and
a group h: Al: 0.0100% to 1.00%.

4. The rail according to claim 2 , comprising, by mass %, one or more groups selected from the group consisting of:
a group a: Mo: 0.01% to 0.50%;
a group b: Co: 0.01% to 1.00%;
a group c: B: 0.0001% to 0.0050%;
a group d: one or two selected from Cu: 0.01% to 1.00% and Ni: 0.01% to 1.00%;
a group e: one or more selected from Nb: 0.0010% to 0.0500% and Ti: 0.0030% to 0.0500%;
a group f: one or more selected from Mg: 0.0005% to 0.0200%, Ca: 0.0005% to 0.0200%, and REM: 0.0005% to 0.0500%;
a group g: Zr: 0.0001% to 0.0200%; and
a group h: Al: 0.0100% to 1.00%.

Assignees

• Nippon Steel Corp

Inventors

• Ueda Masaharu
• Takahashi Jun
• Miyazaki Teruhisa
• Tanahashi Takuya

Classifications

• C21D8/00 Primary

  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) · CPC title

• E01B5/02

  Rails · CPC title

• C22C38/38

  with more than 1.5% by weight of manganese · CPC title

• C22C38/34

  with more than 1.5% by weight of silicon · CPC title

• C22C38/24

  with vanadium · CPC title