VALVE SPRING

WIPO Patent Application WO/2021/075501

A1

The present invention provides a valve spring which has excellent fatigue limit. A valve spring according to one embodiment of the present invention is provided with: a nitride layer that forms the surface layer; and a core part that is positioned on the inner side of the nitride layer. The chemical composition of the core part comprises, in mass%, from 0.53% to 0.59% of C, from 2.51% to 2.90% of Si, from 0.70% to 0.85% of Mn, 0.020% or less of P, 0.020% or less of S, from 1.40% to 1.70% of Cr, from 0.17% to 0.53% of Mo, from 0.23% to 0.33% of V, from 0.0001% to 0.0050% of Ca, 0.050% or less of Cu, 0.050% or less of Ni, 0.0050% or less of Al, 0.050% or less of Ti and 0.0070% or less of N, with the balance being made up of Fe and impurities. The number density of V-based precipitates having a maximum diameter of from 2 nm to 10 nm in the core part is from 500 to 8,000 per μm2; and the number ratio of Ca sulfides to the total number of oxide-based inclusions and sulfide-based inclusions in the core part is 0.20% or less.

TERAMOTO SHINYA (JP)
NEISHI YUTAKA (JP)
AONO MICHIMASA (JP)
KOZAWA SHUJI (JP)
TAKAHASHI FUMIO (JP)
NISHIMOTO SHIGEKAZU (JP)
KONDO MITSUHIRO (JP)
OCHI TATSURO (JP)
SUZUKI SHOICHI (JP)

PCT/JP2020/038932

April 22, 2021

October 15, 2020

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NIPPON STEEL CORP (JP)
NHK SPRING CO LTD (JP)
NIPPON STEEL SG WIRE CO LTD (JP)

C21C7/04; C21D1/06; C21D8/06; C21D9/52; C22C38/00; C22C38/50; F16F1/02; F16F1/06

JP2018178184A	2018-11-15
JP2018176268A	2018-11-15
JP2010222604A	2010-10-07

ASCEND IP LAW FIRM (JP)

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