Rail

Patent metadata

Field	Value
Publication number	US-10995396-B2
Application number	US-201716098987-A
Country	US
Kind code	B2
Filing date	May 19, 2017
Priority date	May 19, 2016
Publication date	May 4, 2021
Grant date	May 4, 2021

Abstract

A rail according to an aspect of the present invention is manufactured by melting steel using an electric furnace, satisfies a predetermined range as a chemical composition and particularly includes Pb: 0.0003% to 0.0020%, 95 area % or more of a region from an outer surface of a head portion to a depth of 20 mm is a pearlite structure, and a hardness in the region from the outer surface of the head portion to the depth of 20 mm is in a range of Hv 300 to Hv 500.

First claim

The invention claimed is:

1. A rail manufactured by melting steel using an electric furnace comprising, as a chemical composition, by unit mass %:
C: 0.75% to 1.20%;
Si: 0.10% to 2.00%;
Mn: 0.10% to 2.00%;
P≤0.0250%;
S≤0.0250%;
Ph: 0.0003% to 0.0020%;
a group a: one or two of Cr: 0% to 2.00% and Mo: 0% to 0.50%;
a group b: Co: 0% to 1.00%;
a group c: B: 0% to 0.0050%;
a group d: one or two of Cu: 0% to 1.00% and Ni: 0% to 1.00%;
a group e: one or two or more of \′: 0% to 0.50%, Nb: 0% to 0.0500%, and Ti: 0% to 0.0500%;
a group f: one or two or more of Mg: 0% to 0.0200%, Ca: 0% to 0.0200%, and REM: 0% to 0.0500%;
a group g: Zr: 0% to 0.0200%;
a group h: Al: 0% to 1.0000%;
a group i: N: 0% to 0.0200%; and
a remainder including Fe and impurities,
wherein 95 area % or more of a region from an outer surface of a head portion to a depth of 20 mm is a pearlite structure,
a hardness in the region from the outer surface of the head portion to the depth of 20 mm is in a range of dv 300 to 500,
an impact value is 10.0 J/cm 2 or more, and
the hardness in the region from the outer surface of the head portion to the depth of 20 mm is obtained by measuring the Vickers hardness at 10 or more points under a load of 98 N at each of the measurement position of a depth of 2 ram from the outer surface of the head portion and the measurement position of a depth of 20 mm from the outer surface of the head portion, and calculating the average value thereof.

2. The rail according to claim 1 ,
wherein an average number density of Pb oxide-based inclusions having a grain size of 1.0 μm to 5.0 μm is 100 pieces/1000 μm 2 or less, in a cross-section of the region from the outer surface of the head portion to the depth of 2 mm to 20 mm.

3. The rail according to claim 2 comprising, as the chemical composition, by unit mass %:
one group or two or more groups of,
a group a: one or two of Cr: 0.10% to 2.00% and 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 of Cu: 0.01% to 1.00% and Ni: 0.01% to 1.00%;
a group e: one or two or more of V: 0.01% to 0.50%, Nb: 0.0010% to 0.0500%, and Ti: 0.0030% to 0.0500%;
a group f: one or two or more of 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%;
a group h: Al: 0.0050% to 1.0000%; and
a group i: N: 0.0050% to 0.0200%.

4. The rail according to claim 1 comprising, as the chemical composition, by unit mass %:
one group or two or more groups,
a group a: one or two of Cr: 0.10% to 2.00% and 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 of Cu: 0.01% to 1.00% and Ni: 0.01% to 1.00%;
a group e: one or two or more of V: 0.01% to 0.50%, Nb: 0.0010% to 0.0500%, and Ti: 0.0030% to 0.0500%;
a group f: one or two or more of 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%;
a group h: Al: 0.0050% to 1.0000%; and
a group i: N: 0.0050% to 0.0200%.

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Nippon Steel Corp

Inventors

• Ueda Masaharu
• Miyazaki Teruhisa

Classifications

• C21D2211/009

  Pearlite · CPC title

• C22C38/12

  containing tungsten, tantalum, molybdenum, vanadium, or niobium · CPC title

• C21D2211/004

  Dispersions; Precipitations · CPC title

• C21D9/04

  for rails · CPC title

• C22C38/002

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