US 2012/0230800 A1Published application

High-Strength Bolt

AssigneesNational Institute for Materials Science, Kyowa Kogyosyo Co., Ltd., Fusokiko Co., Ltd.

InventorsYuuji Kimura, Tadanobu Inoue, Shuji Murasaki, Mataichi Fukuda

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Abstract

Provided is a high-strength bolt which has a tensile strength of 1,200 MPa or more while exhibiting excellent ductility and delayed facture resistance, and further has an excellent impact toughness which had not been obtained in the conventional high-strength bolt. The high-strength bolt has a tensile strength of 1.2 GPa or more and includes a threaded portion and cylindrical neck portion. The bolt has K of 0.8 or more and satisfies Ho<Hs, where K is defined by the equation: (Ao×Ho)/(As×Hs)=K, in which Ao is an effective cross-sectional area of the cylindrical neck portion with a diameter larger than that of the threaded portion, Ho is a Vickers hardness of a portion at which Ao is measured, As is an effective cross-sectional area of the threaded portion, and Hs is a Vickers hardness of the threaded portion.

Claims4

Dependent claims

A high-strength bolt having a tensile strength of 1.2 GPa or more and comprising a threaded portion and a cylindrical neck portion,

wherein the bolt has K of 0.8 or more and satisfies Ho<Hs, Ho and Hs being hardness obtained after a rolling process for forming the threaded portion and a heading process for forming a head portion, K being defined by the following equation (1):
(Ao×Ho)/(As×Hs)=K (1)
wherein
Ao is an effective cross-sectional area of the cylindrical neck portion,
Ho is a Vickers hardness of a portion at which Ao is measured, the Vickers hardness being measured in accordance with a testing method prescribed in JIS-Z-2244,
As is an effective cross-sectional area of the threaded portion, and
Hs is a Vickers hardness of a portion at which As is measured, the Vickers hardness being measured in accordance with a testing method prescribed in JIS-Z-2244,
the Vickers hardness being measured on a cross section of a sample obtained by cutting the bolt along an axis thereof and buffing the cross section to mirror finish.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/395,298Filed 10 Sep 2010
Priority: JP 200920958110 Sep 2009
Published: 13 Sep 2012
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

F16B 35/041
With specially-shaped head or shaft in order to fix the bolt on or in an object: specially-shaped shafts
C21D 8/06
Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment: during…
C21D 9/0093
Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor: for screws; for bolts
C22C 38/001
Ferrous alloys, e.g. steel alloys: containing N