The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 16, 2017
Filed:
Jun. 11, 2013
Kobe Steel, Ltd., Kobe-shi, JP;
Shinko Metal Products Co., Ltd., Kitakyusyu-shi, JP;
Takuya Kochi, Hyogo, JP;
Hitoshi Hatano, Hyogo, JP;
Eiichi Tamura, Hyogo, JP;
Kotaro Toyotake, Fukuoka, JP;
KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.), Kobe-shi, JP;
SHINKO METAL PRODUCTS CO., LTD., Kitakyusyu-shi, JP;
Abstract
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 μm 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 1.8×10particles/μmor less.