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:
Nov. 01, 2016
Filed:
May. 10, 2013
Shinko Metal Products Co., Ltd., Kitakyusyu-shi, Fukuoka, JP;
Nhk Spring Co., Ltd., Yokohama-shi, Kanagawa, JP;
Kotaro Toyotake, Tokyo, JP;
Koji Iwaya, Kitakyushu, JP;
Tomoyuki Minami, Kitakyushu, JP;
Noritoshi Takamura, Kanagawa, JP;
SHINKO METAL PRODUCTS CO., LTD., Fukuoka, JP;
NHK SPRING CO., LTD., Kanagawa, JP;
Abstract
There are provided: a seamless steel pipe formed from a cylindrical steel material billet through a hot isostatic extrusion step, wherein a depth of a contiguous flaw formed on an inner periphery surface and an outer periphery surface of the steel pipe is 50 μm or less; a hollow spring obtained by forming a hollow body in a shape of a coil or a bar or a bar with curved part from the seamless steel pipe made of spring steel and applying a surface treatment to the hollow body so that the hollow body has compressive residual stress; and a method for producing seamless steel pipe including: a billet molding step; a first heating step; a hot isostatic extrusion step; a second heating step; an extension step; a third heating step; and a pickling step.