Railway axle

Patent metadata

Field	Value
Publication number	US-12377888-B2
Application number	US-202118007428-A
Country	US
Kind code	B2
Filing date	Sep 28, 2021
Priority date	Sep 29, 2020
Publication date	Aug 5, 2025
Grant date	Aug 5, 2025

Abstract

The railway axle according to this disclosure has a pair of fitting portions and which each include a fitting portion hardened layer and a base metal portion, and a center parallel portion which includes a center parallel portion hardened layer and the base metal portion. The base metal portion has the chemical composition described in the description. In a region having the Vickers hardness of 480 HV or more in the center parallel portion hardened layer, a dislocation density ρ obtained based on a CoKα characteristic X-ray diffraction result is 2.5×10 16 m −2 or less, a half-value width B of the (211) diffraction plane is 1.34 degrees or less, and the dislocation density ρ and the half-value width B of the (211) plane obtained by X-ray diffraction satisfy Formula (1).

(−4.8×10 16 ×B +8.5×10 16 )/ρ≥1.00  (1)

First claim

The invention claimed is:

1. A railway axle, comprising:
a pair of fitting portions, on each of which a railway wheel is to be press-fitted, and
a center parallel portion located between the pair of fitting portions, wherein:
the fitting portion includes:
a fitting portion hardened layer formed in an outer layer of the fitting portion, and
a base metal portion located inward of the fitting portion hardened layer;
the center parallel portion includes:
a center parallel portion hardened layer formed in an outer layer of the center parallel portion, and
the base metal portion located inward of the center parallel portion hardened layer;
the base metal portion consists of, in mass %,
C: 0.22 to 0.29%,
Si: 0.15 to 0.40%,
Mn: 0.50 to 0.80%,
P: 0.020% or less,
S: 0.040% or less,
Cr: 0.90 to 1.20%,
Mo: 0.15 to 0.30%,
N: 0.0200% or less,
O: 0.0040% or less,
Ca: 0 to 0.0010%,
Cu: 0 to 0.30%,
Ni: 0 to 0.30%,
Al: 0 to 0.100%,
V: 0 to 0.060%,
Ti: 0 to 0.020%,
Nb: 0 to 0.030%, and
B: 0 to 0.0050%,
with the balance being Fe and impurities; and
in a region having the Vickers hardness of 480 HV or more in the center parallel portion hardened layer,
a dislocation density ρ obtained based on a CoKα characteristic X-ray diffraction result is 2.5×10 16 m −2 or less,
a half-value width B of a (211) diffraction plane measured by CoKα characteristic X-ray diffraction is 1.34 degrees or less, and
the dislocation density ρ obtained based on a CoKα characteristic X-ray diffraction result, and the half-value width B of a (211) diffraction plane measured by CoKα characteristic X-ray diffraction satisfy Formula (1):
(−4.8×10 16 ×B +8.5×10 16 )/ρ≥1.00  (1)

wherein, in Formula (1), ρ is the dislocation density in m −2 obtained based on a CoKα characteristic X-ray diffraction result, and B is the half-value width in degrees of a (211) diffraction plane measured by CoKα characteristic X-ray diffraction.

2. The railway axle according to claim 1 , wherein:
the base metal portion has, in mass %, one or more elements selected from the group consisting of:
Cu: 0.01 to 0.30%,
Ni: 0.01 to 0.30%,
Al: 0.005 to 0.100%,
V: 0.005 to 0.060%,
Ti: 0.002 to 0.020%,
Nb: 0.002 to 0.030%, and
B: 0.0003 to 0.0050%.

Assignees

• Nippon Steel Corp

Inventors

• Makino Taizo
• Kozuka Chihiro
• Yamamoto Yuichiro
• Hata Toshiyuki
• Yamane Akihito

Classifications

• 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

• C21D9/0075

  for rods of limited length (of unlimited length C21D9/52) · CPC title

• C21D7/13

  by hot working · CPC title

• C21D1/25

  Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten") · CPC title

• C21D1/10

  by electric induction · CPC title