Kobe Steel, Ltd.

Nhk Spring Co., Ltd.

Kabushiki Kaisha Kobe Seiko Sho (kobe Steel, Ltd.)

Shinko Metal Products Co., Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Takuya Kochi

Takeshi Kuroda

Hiroshi Yaguchi

Wataru Urushihara

Takaaki Minamida

Hitoshi Hatano

Hidenori Nako

Shogo Murakami

Yoshihiko Kitagawa

Hidenori Sakai

Tomotada Maruo

Munenobu Sato

Akira Tange

Mikako Takeda

Takashi Onishi

Kotaro Toyotake

Eiichi Tamura

Koji Yamashita

Nao Yoshihara

Mamoru Nagao

Takehiro Tsuchida

Masamichi Chiba

Yoshitomi Okazaki

Kiyoshi Kurimoto

Takashi Yajima

Masao Toyama

Yurika Goto

Masahiro Nomura

Shoji Miyazaki

Kei Masumoto

Noriaki Hiraga

Fujio Koizumi

Hiroyuki Kawasaki

Yuki Sasaki

Masayuki Sakata

Ken Ishida

Hiromichi Tsuchiya

Peng Han

Masumi Nishimura

Provided is a steel for a mechanical structure for cold working, which contains C, Si, Mn, P, S, Al and N and in which the metal structure includes pearlite and ferrite, the total areal proportion of pearlite and ferrite relative to the overall structure is 90% or higher, the average circle-equivalent diameter of bcc-Fe crystal grains surrounded by large angle grain boundaries is 5-15 &#x3bc;m, the average aspect ratio of pro-eutectoid ferrite crystal grains is 3.0 or lower, and the average spacing at the narrowest pearlite lamellar spacing is 0.20 &#x3bc;m or less.

Steel for mechanical structure for cold working, and method for producing same

A method for manufacturing steel, by quenching and tempering a seamless pipe for use as a material of a hollow spring, where the seamless pipe including predetermined components is subjected to a heat treatment which is performed to satisfy quenching conditions (1) and tempering conditions (2),

Method for manufacturing steel for high-strength hollow spring

The present invention is a weld metal formed by gas shielded arc welding using a flux cored wire, the welded metal having a predetermined chemical composition, residual austenite particles being present in an amount of at least 2500 particles/mm, and the volume fraction of residual austenite particles being at least 4.0%.

Weld metal having excellent resistance to hydrogen embrittlement

Disclosed is a weld metal which is formed by gas-shielded arc welding using a flux-cored wire, and which has a specific chemical composition, in which retained austenite particles are present in a number density of 2500 per square millimeter or more and in a total volume fraction of 4.0% or more based on the total volume of entire structures of the weld metal. The weld metal has excellent hydrogen embrittlement resistance and is resistant to cracking at low temperatures even when the weld metal has a high strength.

Weld metal excellent in hydrogen embrittlement resistance

A seamless steel pipe for a hollow spring includes C: 0.2 to 0.7 mass %, Si: 0.5 to 3 mass %, Mn: 0.1 to 2 mass %, Cr: 3 mass % or less (excluding 0 mass %), Al: 0.1 mass % or less (excluding 0 mass %), P: 0.02 mass % or less (excluding 0 mass %), S: 0.02 mass % or less (excluding 0 mass %) and N: 0.02 mass % or less (excluding 0 mass %). A residual austenite content in an inner surface layer part of the steel pipe is 5 vol. % or less. An average grain size of a ferrite-pearlite structure in the inner surface layer part of the steel pipe is 18 &#x3bc;m or less. A number density of a carbide having a circle equivalent diameter of 500 nm or more and being present in the inner surface layer part of the steel pipe is 1.8&#xd7;10particles/&#x3bc;mor less.

Seamless steel pipe for hollow spring

The weld metal of the present invention is formed by gas shield arc welding using a flux-cored wire, has a predetermined chemical component composition, and contains 20% or more of Ti. The amount of Ti-containing oxide particles having a circle-equivalent diameter of 0.15-1.0 &#x3bc;m is at least 5000 per square mm, the amount of V per total mass of weld metal present as a compound within the weld metal is 0.002% or more, and the average circle equivalent diameter of V-containing carbide present in the weld metal is 15 nm or less.

Weld metal having excellent resistance to hydrogen embrittlement susceptibility

A hollow seamless pipe for a high-strength spring in the present invention includes a steel material in which chemical component compositions are properly adjusted, wherein a depth of a whole decarburized layer in an inner surface layer part is 100 &#x3bc;m or less, a depth of a flaw which is present in an inner surface is 40 &#x3bc;m or less, a width of the flaw is 60 &#x3bc;m or less, and a number density of a carbide which has a circle equivalent diameter of 500 nm or more and is present in the inner surface layer part is 1.8&#xd7;10particles/&#x3bc;mor less.

Hollow seamless pipe for high-strength spring

A hot-rolled wire rod excelling in wire drawability is provided, in which breakage can be suppressed even in heavy work from a large diameter. A hot-rolled wire rod contains C: 0.35 to 0.65% (percent by mass, hereinafter expressed as well), Si: 1.4 to 3.0%, Mn: 0.10 to 1.0%, Cr: 0.1 to 2.0%, P: 0.025% or less (exclusive of 0%), S: 0.025% or less (exclusive of 0%), N: 0.006% or less (exclusive of 0%), Al: 0.1% or less (exclusive of 0%), and O: 0.0030% or less (exclusive of 0%), with the remnant consisting of Fe and inevitable impurities; wherein the content of hydrogen in steel is 2.50 ppm (ppm by mass, hereinafter expressed as well) or less, and hardness (HV) is 460&#xd7;Cor less (Cindicates the content of C (percent by mass) in a position of depth of D/4 (D: diameter of the wire rod)).

Wire with excellent suitability for drawing and process for producing the same

A steel for heat treatment, which exhibits high strength and high toughness even when the heat treatment (such as quenching and tempering) of the steel is conducted under conventional conditions in an after stage. The steel for heat treatment contains C: 0.10 to 0.70 mass %, Mn: 0.1 to 3.0 mass %, Al: 0.005 to 2.0 mass %, P: 0.050 mass % or less, S: 0.50 mass % or less, O: 0.0030 mass or less, N: 0.0200 mass % or less, and one or more selected from the group consisting of Ti: 0.30 mass % or less and Nb: 0.30 mass or less with the balance being Fe and unavoidable impurities, and has a TH value of 1.0 or above as calculated according to the formula: ({Ti}/48+{Nb}/93) 10and grain diameters of 10 &#x3bc;m or below. {Ti} and {Nb} refer respectively to the contents of Ti and Nb in precipitates of 5 to 100 nm in size as determined about their respective extraction residues.

Steel for heat treatment

Disclosed is a spring steel wire rod that comprises C in a range of 0.35 to 0.65% (mass %, the same applies to respective elements described hereinafter), Si in a range of 1.4 to 2.2%, Mn in a range of 0.10 to 1.0%, Cr in a range of 0.1 to 2.0%, P not more than 0.025% (0% excluded), and S not more than 0.025% (0% excluded), balance comprising iron, and unavoidable impurities, wherein an average grain size Dc of a central part of the steel wire rod is not more than 80 &#x3bc;m while an average grain size Ds of a surface layer part of the steel wire rod is not less than 3.0 &#x3bc;m.

Spring steel wire rod excellent in decarburization resistance and wire drawing workability and method for producing same

A high carbon steel wire material which is made of high carbon steel as a raw material for wire products such as steel cords, bead wires, PC steel wires and spring steel, allows for these wire products to be manufactured efficiently at a high wire drawing rate and has excellent wire drawability and a manufacturing process thereof. This high carbon steel wire material is made of a steel material having specific contents of C, Si, Mn, P, S, N, Al and O, and the Bcc-Fe crystal grains of its metal structure have an average crystal grain diameter (D) of 20 &#x3bc;m or less and a maximum crystal grain diameter (D) of 120 &#x3bc;m or less, preferably an area ratio of crystal grains having a diameter of 80 &#x3bc;m or more of 40% or less, an average sub grain diameter (d) of 10 &#x3bc;m or less, a maximum sub grain diameter (d) of 50 &#x3bc;m or less and a (D/d) ratio of the average crystal grain diameter (D) to the average sub grain diameter (d) of 4.5 or less.

Process for manufacturing a high carbon steel wire material having excellent wire drawability

The present invention aims at providing a method for production of a steel product which surely retains scale during cooling, storage, and transportation and permits scale to scale off easily at the time of mechanical descaling and pickling that precede the secondary fabrication. The steel product is produced by heating and hot rolling a steel billet and spraying the hot-rolled steel product with steam and/or water mist having a particle diameter no larger than 100 &#x3bc;m, for surface oxidation.

Method for production of steel product with outstanding descalability; and steel wire with outstanding descalability

A spring steel having a high strength of 1900 MPa or more and superior in the brittle fracture resistance, as well as a method for manufacturing the same, are provided. The high strength spring steel comprises, as basic components in mass %, C: 0.4-0.6%, Si: 1.4-3.0%, Mn: 0.1-1.0%, Cr: 0.2-2.5%, P: 0.025% or less, S: 0.025% or less, N: 0.006% or less, Al: 0.1% or less, and O: 0.003% or less, the amount of solute C being 0.15% or less, the amount of Cr contained as a Cr-containing precipitate being 0.10% or less, and a TS value represented by the following equation being 24.8% or more, and in point of structure, the pre-austenite grain diameter being 10 &#x3bc;m or smaller, wherein TS=28.5*[C]+4.9*[Si]+0.5*[Mn]+2.5*[Cr]+1.7*[V]+3.7*[Mo] where [X] stands for mass % of element X.

High-strength spring steel excellent in brittle fracture resistance and method for producing same

A steel for high-strength springs contains, on the mass basis, 0.35% to 0.65% of C, 1.4% to 2.5% of Si, 0.1% to 1.0% of Mn, 2.0% or less (exclusive of 0%) of Cr, 1.0% or less (exclusive of 0%) of Ni, 1.0% or less (exclusive of 0%) of Cu, 0.020% or less (exclusive of 0%) of P, 0.020% or less (exclusive of 0%) of S, 0.006% or less (exclusive of 0%) of N:, and 0.1% or less (exclusive of 0%) of Al, with the remainder being iron and inevitable impurities, in which Wp(Fe) and W(C) satisfy the following condition: Wp(Fe)&#x3e;5&#xd7;W(C), wherein Wp(Fe) is the content of Fe (percent by mass) constituting Fe-containing precipitates in the steel; and W(C) is the carbon content (percent by mass) of the steel. The steel is excellent in cold workability and quality stability.

Steels for high-strength springs excellent in cold workability and quality stability

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Kobe, Japan

Takuya Kochi