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AssigneesKabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.), NHK Spring Co., Ltd., Shinko Metal Products Co., Ltd.
InventorsHitoshi Hatano, Kotaro Toyotake
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The present invention provides a hollow seamless pipe for high-strength springs, in which the occurrence of decarburization in an inner peripheral surface and outer peripheral surface is reduced as much as possible, surface layer parts can be sufficiently hardened in the outer peripheral surface and the inner peripheral surface in a quenching step at the time of spring production, and sufficient fatigue strength can be secured in springs to be formed. The present invention relates to a hollow seamless pipe for a high-strength spring, which is composed of a steel material comprising 0.2 to 0.7 mass % of C, 0.5 to 3 mass % of Si, 0.1 to 2 mass % of Mn, more than 0 mass % and 0.1 mass % or less of Al, more than 0 mass % and 0.02 mass % or less of P, more than 0 mass % and 0.02 mass % or less of S, and more than 0 mass % and 0.02 mass % or less of N, wherein the C content in an inner peripheral surface and outer peripheral surface of the hollow seamless pipe is 0.10 mass % or more, and a thickness of a whole decarburized layer in each of the inner peripheral surface and the outer peripheral surface is 200 μm or less.
A hollow seamless pipe for high-strength springs, which is composed of a steel material comprising 0.2 to 0.7 mass % of C, 0.5 to 3 mass % of Si, 0.1 to 2 mass % of Mn, more than 0 mass % and 0.1 mass % or less of Al, more than 0 mass % and 0.02 mass % or less of P, more than 0 mass % and 0.02 mass % or less of S, and more than 0 mass % and 0.02 mass % or less of N, wherein the C content in an inner peripheral surface and outer peripheral surface of the hollow seamless pipe is 0.10 mass % or more, and a thickness of a whole decarburized layer in each of the inner peripheral surface and the outer peripheral surface is 200 μm or less.
Dependencies are inferred from the claim text.