Valve spring

Patent metadata

Field	Value
Publication number	US-12338518-B2
Application number	US-202117904448-A
Country	US
Kind code	B2
Filing date	Feb 19, 2021
Priority date	Feb 21, 2020
Publication date	Jun 24, 2025
Grant date	Jun 24, 2025

Abstract

A valve spring which has an excellent fatigue limit is provided. A chemical composition of the valve spring according to the present embodiment contains, in mass %, C: 0.50 to 0.80%, Si: 1.20 to less than 2.50%, Mn: 0.25 to 1.00%, P: 0.020% or less. S: 0.020% or less: Cr: 0.40 to 1.90%, V: 0.05 to 0.60%, Ca: 0.0001 to 0.0050%, and N: 0.0100% or less, with the balance being Fe and impurities. In the valve spring, a number density of V-based precipitates having a maximum diameter ranging from 2 to 10 nm is 5000 to 80000 pieces/μm 3 , and a numerical proportion of Ca sulfides with respect to a total number of oxide-based inclusions and sulfide-based inclusions is 0.20% or less.

First claim

The invention claimed is:

1. A valve spring, wherein:
when a wire diameter is defined as d (mm), a chemical composition at a d/4 depth position from a surface contains, in mass %,
C: 0.50 to 0.80%,
Si: 1.20 to less than 2.50%,
Mn: 0.25 to 1.00%,
P: 0.020% or less,
S: 0.020% or less,
Cr: 0.40 to 1.90%,
V: 0.05 to 0.60%,
Ca: 0.0001 to 0.0050%,
N: 0.0100% or less,
Mo: 0 to 0.50%,
Nb: 0 to 0.050%,
W: 0 to 0.60%,
Ni: 0 to 0.500%,
Co: 0 to 0.30%
B: 0 to 0.0050%,
Cu: 0 to 0.050%,
Al: 0 to 0.0050%, and
Ti: 0 to 0.050%,
with the balance being Fe and impurities,
and wherein:
in a microstructure of the valve spring, an area fraction of martensite is 90.0% or more,
a number density of V-based precipitates having a maximum diameter ranging from 2 to 10 nm is 5000 to 80000 pieces/μm 3 , and
wherein, among inclusions,
inclusions in which, in mass %, an O content is 10.0% or more are defined as oxide-based inclusions,
inclusions in which, in mass %, an S content is 10.0% or more and the O content is less than 10.0% are defined as sulfide-based inclusions, and
among the sulfide-based inclusions, inclusions in which, in mass %, a Ca content is 10.0% or more, the S content is 10.0% or more, and the O content is less than 10.0% are defined as Ca sulfides,
a numerical proportion of the Ca sulfides with respect to a total number of the oxide-based inclusions and the sulfide-based inclusions is 0.20% or less.

2. The valve spring according to claim 1 , wherein:
the chemical composition contains one or more types of element selected from the group consisting of:
Mo: 0.01 to 0.50%,
Nb: 0.001 to 0.050%,
W: 0.01 to 0.60%,
Ni: 0.001 to 0.500%,
Co: 0.01 to 0.30%, and
B: 0.0001 to 0.0050%.

3. The valve spring according to claim 2 , wherein:
the chemical composition contains one or more types of element selected from the group consisting of:
Cu: 0.001 to 0.050%,
Al: 0.0001 to 0.0050%, and
Ti: 0.001 to 0.050%.

4. The valve spring according to claim 1 , wherein:
the chemical composition contains one or more types of element selected from the group consisting of:
Cu: 0.001 to 0.050%,
Al: 0.0001 to 0.0050%, and
Ti: 0.001 to 0.050%.

Assignees

• Nippon Steel Corp
• Nippon Steel Sg Wire Co Ltd

Inventors

• Teramoto Shinya
• Neishi Yutaka
• AONO Michimasa
• Mineta Satoru
• Suzuki Shoichi
• Ochi Tatsuro

Classifications

• C21D8/06

  during manufacturing of rods or wires · CPC title

• C22C38/52

  with cobalt · CPC title

• C22C38/48

  with niobium or tantalum · CPC title

• C22C38/46

  with vanadium · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title