Kobe Steel, Ltd.

Shinko Metal Products Co., Ltd.

Nhk Spring Co., Ltd.

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

Kabushiki Kaisha Kobe Seiko Sho

Eiichi Tamura

Katsushi Matsumoto

Toshiki Ueda

Shimpei Kimura

Fumihiro Koshigoe

Kotaro Toyotake

Hitoshi Hatano

Akira Tange

Shinji Sato

Takuya Kochi

Yasuto Kataoka

Masao Kinefuchi

Shuo Huang

Takashi Yajima

Hiroyuki Takaoka

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

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

Disclosed is a high-strength steel plate having a predetermined chemical composition, in which a microstructure of the steel plate at a depth of one-fourth to one half the thickness from a surface has an area fraction of bainite of 90% or more, an average lath width of bainite of 3.5 &#x3bc;m or less, and a maximum equivalent circle diameter of martensite-austenite constituents in bainite of 3.0 &#x3bc;m or less. The steel plate exhibits high strengths and good drop weight properties and is useful as structural materials for offshore structure, ships, and bridges, as well as materials for pressure vessels in nuclear power plants.

High-strength steel plate excellent in drop weight properties

Provided is a multi-layered sheet which has undergone heating corresponding to brazing, such as an aluminum-alloy radiator tube, or a multi-layered sheet such as an aluminum-alloy brazing sheet. The multi-layered sheet can have a reduced thickness and has excellent fatigue properties. The multi-layered sheet of aluminum alloys comprises a core layer () which has been clad at least with a sacrificial layer (). This multi-layered sheet is a multi-layered sheet to be subjected to brazing or welding to produce a heat exchanger or is a multi-layered sheet which has undergone heating corresponding to brazing. The core layer () comprises a specific 3000-series composition. In this core layer (), the average density in number of dispersed particles having a specific size has been regulated. As a result, fatigue properties, which govern cracking, can be highly improved.

Multi-layered sheet of aluminum alloys

Disclosed herein is an aluminum alloy clad sheet for a heat exchanger including a core layer, a sacrificial layer formed on one surface of the core layer, and a filler layer including an Al&#x2014;Si based alloy formed on the other surface of the core layer. The core layer includes a predetermined amount of Si, Cu, Mn, Ti, and Mg, the remainder including Al and inevitable impurities, and the sacrificial layer includes a predetermined amount of Si, Mn, and Zn, the remainder including Al and inevitable impurities. The core layer has a crystal grain size after the brazing heat treatment at 595&#xb0; C. for 3 minutes of at least 50 &#x3bc;m and less than 300 &#x3bc;m. The filler layer and the sacrificial layer are defined for their thickness, and the number of intermetallic compounds in the core layer is also defined to a predetermined range. By such constitution, the aluminum alloy clad sheet has improved fatigue life and post-braze strength, high corrosion resistance, and excellent erosion resistance and brazeability.

Aluminum alloy clad sheet for a heat exchanger and its production method

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Kobe, Japan

Eiichi Tamura