Rail

Patent metadata

Field	Value
Publication number	US-10047411-B2
Application number	US-201615544686-A
Country	US
Kind code	B2
Filing date	Jan 22, 2016
Priority date	Jan 23, 2015
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

The present invention relates to a rail which has a predetermined chemical composition and in which at least 90% of a metallographic structure from an outer surface of the rail bottom portion, as the origin, to a depth of 5 mm is a pearlite structure, a surface hardness HC of a foot-bottom central portion is in a range of Hv 360 to 500, a surface hardness HE of a foot-edge portion is in a range of Hv 260 to 315, and HC, HE, and a surface hardness HM of a middle portion positioned between the foot-bottom central portion and the foot-edge portion satisfy HC≥HM≥HE.

First claim

What is claimed is:

1. A rail comprising, as steel composition, in terms of mass %:
C: 0.75% to 1.20%;
Si: 0.10% to 2.00%;
Mn: 0.10% to 2.00%;
Cr: 0% to 2.00%;
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%;
V: 0% to 0.50%;
Nb: 0% to 0.050%;
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%;
N: 0% to 0.0200%;
Al: 0% to 1.00%;
P: 0.0250% or less;
S: 0.0250% or less; and
Fe and impurities as a remainder, wherein
90% or more of a metallographic structure in a range between an outer surface of a rail bottom portion as an origin and a depth of 5 mm is a pearlite structure,
an HC which is a surface hardness of a foot-bottom central portion is in a range of Hv 360 to 500,
an HE which is a surface hardness of a foot-edge portion is in a range of Hv 260 to 315, and
the HC, the HE, and an HM which is a surface hardness of a middle portion positioned between the foot-bottom central portion and the foot-edge portion satisfy the following Expression 1,
HC≥HM≥HE  (Expression 1).

2. The rail according to claim 1 , wherein the HM and the HC satisfy the following Expression 2,
HM/HC≥0.900  (Expression 2).

3. The rail according to claim 1 ,
wherein the steel composition comprises, in terms of mass %, at least one selected from the group consisting of
Cr: 0.01% to 2.00%,
Mo: 0.01% to 0.50%,
Co: 0.01% to 1.00%,
B: 0.0001% to 0.0050%,
Cu: 0.01% to 1.00%,
Ni: 0.01% to 1.00%,
V: 0.005% to 0.50%,
Nb: 0.0010% to 0.050%,
Ti: 0.0030% to 0.0500%,
Mg: 0.0005% to 0.0200%,
Ca: 0.0005% to 0.0200%,
REM: 0.0005% to 0.0500%,
Zr: 0.0001% to 0.0200%,
N: 0.0060% to 0.0200%, and
Al: 0.0100% to 1.00%.

4. The rail according to claim 2 ,
wherein the steel composition comprises, in terms of mass %, at least one selected from the group consisting of
Cr: 0.01% to 2.00%,
Mo: 0.01% to 0.50%,
Co: 0.01% to 1.00%,
B: 0.0001% to 0.0050%,
Cu: 0.01% to 1.00%,
Ni: 0.01% to 1.00%,
V: 0.005% to 0.50%,
Nb: 0.0010% to 0.050%,
Ti: 0.0030% to 0.0500%,
Mg: 0.0005% to 0.0200%,
Ca: 0.0005% to 0.0200%,
REM: 0.0005% to 0.0500%,
Zr: 0.0001% to 0.0200%,
N: 0.0060% to 0.0200%, and
Al: 0.0100% to 1.00%.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Ueda Masaharu
• Yamamoto Takeshi
• Miyazaki Teruhisa

Classifications

• C21D9/04 Primary

  for rails · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• E01B5/02

  Rails · CPC title

• C21D8/00

  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) · CPC title

• C21D2211/009

  Pearlite · CPC title