Nippon Steel Corporation

Nippon Steel Sg Wire Co., Ltd.

Nhk Spring Co., Ltd.

Aisin Corporation

Michimasa Aono

Yutaka Neishi

Tatsuro Ochi

Shoichi Suzuki

Shinya Teramoto

Shuji Kozawa

Fumio Takahashi

Shigekazu Nishimoto

Mitsuhiro Kondo

Kenichiro Miyamoto

Masanobu Suzuki

Satoru Mineta

Yoichi Oi

Naoki Takabayashi

Junji Tanaka

A damper spring which has an excellent fatigue limit is provided. A chemical composition of the damper 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%, and N: 0.0100% or less, with the balance being Fe and impurities. In the damper spring, a number density of V-based precipitates having a maximum diameter ranging from 2 to 10 nm is 5000 to 80000 pieces/μm.

Damper spring

A damper spring having an excellent fatigue limit is provided. A damper spring according to the present embodiment includes a nitrided layer formed in an outer layer, and a core portion that is further inward than the nitrided layer. The chemical composition of the core portion consists of, in mass %, C: 0.53 to 0.59%, Si: 2.51 to 2.90%, Mn: 0.70 to 0.85%, P: 0.020% or less, S: 0.020% or less, Cr: 1.40 to 1.70%, Mo: 0.17 to 0.53%, V: 0.23 to 0.33%, Cu: 0.050% or less, Ni: 0.050% or less, Al: 0.0050% or less, Ti: 0.050% or less, N: 0.0070% or less, and Nb: 0 to 0.020%, with the balance being Fe and impurities. In the core portion, a number density of V-based precipitates having a maximum diameter ranging from 2 to 10 nm is 500 to 8000 pieces/μm.

A valve spring includes a nitrided layer, and a core portion that is further inward than the nitrided layer. A chemical composition of the core portion consists of, in mass %, C: 0.53 to 0.59%, Si: 2.51 to 2.90%, Mn: 0.70 to 0.85%, P: 0.020% or less, S: 0.020% or less, Cr: 1.40 to 1.70%, Mo: 0.17 to 0.53%, V: 0.23 to 0.33%, Ca: 0.0001 to 0.0050%, Cu: 0.050% or less, Ni: 0.050% or less, Al: 0.0050% or less, Ti: 0.050% or less, and N: 0.0070% or less, with the balance being Fe and impurities. In the core portion, a number density of V-based precipitates having a maximum diameter ranging from 2 to 10 nm is 500 to 8000 per μm, and in the core portion, 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.

Valve spring

A steel wire which has an excellent fatigue limit when made into a spring is provided. A chemical composition of the steel wire according to the present embodiment consists of, in mass %, C: 0.53 to 0.59%, Si: 2.51 to 2.90%, Mn: 0.70 to 0.85%, P: 0.020% or less, S: 0.020% or less, Cr 1.40 to 1.70%, Mo: 0.17 to 0.53%, V: 0.23 to 0.33%, Cu: 0.050% or less, Ni: 0.050% or less, Al: 0.0050% or less, Ti: 0.050% or less, N: 0.0070% or less, Ca: 0 to 0.0050%, and Nb: 0 to 0.020%, with the balance being Fe and impurities. In the steel wire, a number density of V-based precipitates having a maximum diameter ranging from 2 to 10 nm is 500 to 8000 pieces/μm.

Steel wire

Low-oxygen clean steel is provided containing C, Si, Mn, P, and S as chemical components, and further containing, by mass %, 0.005% to 0.20% of Al, greater than 0% to 0.0005% of Ca, 0.00005% to 0.0004% of REM, and greater than 0% to 0.003% of T.O, wherein the REM content, the Ca content, and the T.O content satisfy 0.15&#x2264;REM/Ca&#x2264;4.00 and Ca/T.O&#x2264;0.50, nonmetallic inclusions which have a maximum predicted diameter of 1 &#x3bc;m to 30 &#x3bc;m measured using an extreme value statistical method under the condition in which a prediction area is 30,000 mm, and contain AlOand REM oxide are dispersed in the steel, an average proportion of the AlOin the nonmetallic inclusions is greater than 50%, the REM is one or two or more of rare-earth elements La, Ce, Pr, and Nd, and the steel is Al-deoxidized steel or Al&#x2014;Si-deoxidized steel.

Low-oxygen clean steel and low-oxygen clean steel product

Growing community of inventors

Hokkaido, Japan

Michimasa Aono