Bolt and fastened structure

A technology for fastening structures and bolts, which is applied in the direction of threaded fasteners, bolts, nuts, etc., can solve the problems of brittle fracture and high risk, and achieve the effect of excellent delayed fracture resistance and stable fastening axial force

Active Publication Date: 2020-09-11
NISSAN MOTOR CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003]However, the occurrence of sudden brittle fracture, the so-called "delayed fracture" of high-strength bolts of high-carbon steel under static stress after a certain period of time is remarkable. The higher the intensity, the higher the risk of occurrence

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0065] Hereinafter, the present invention will be described in detail through examples, but the present invention is not limited to the following examples.

[0066] Carbon steel for high-strength bolts with the composition shown in Table 1 below is quenched at a temperature of 900°C or higher after cold forging and screw rolling, and introduced so that the oxygen concentration becomes 3%. N 2 In an atmosphere, tempering was performed under the conditions shown in the following Table 2 to obtain high-strength bolts.

[0067] It should be noted that Comparative Examples 2 and 3, Comparative Examples 6 and 8 did not introduce N 2 If necessary, temper in air.

[0068] [Table 1]

[0069]

[0070] [Table 2]

[0071] tempering temperature tempering time tempered vibe Example 1 580℃ 100min N2+air Example 2 590℃ 100min N2+air Example 3 620℃ 100min N2+air Comparative example 1 570℃ 100min N2+air Comparative example 2 6...

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Abstract

A bolt according to the present invention has such a chemical composition in which 0.50 to 0.65% by mass inclusive of carbon (C), 1.5 to 2.5% by mass inclusive of silicon (Si), 1.0 to 2.0% by mass inclusive of chromium (Cr), 0.2 to 1.0% by mass inclusive of manganese (Mn) and 1.5 to 5.0% by mass inclusive of molybdenum (Mo) are contained, the total amount of phosphorus (P) and sulfur (S) which areimpurities is 0.03% by mass or less and the remainder is made up from iron (Fe), and the bolt has, formed on the surface thereof, an iron-based oxide film having a thickness of 3 to 20 [mu]m inclusive, has excellent delayed fracture resistance, and can achieve a stable tightening axial force.

Description

technical field [0001] The present invention relates to bolts. More specifically, the present invention relates to high-strength bolts with which the management of fastening axial force is relatively easy. Background technique [0002] In order to reduce the weight, compactness, and performance of vehicles, high-strength bolts are required, and high-carbon steel bolts with a tensile strength greater than 1200 MPa are known. [0003] However, the occurrence of sudden brittle fracture, so-called "delayed fracture", is remarkable for high-strength bolts of high-carbon steel after a certain period of time under static stress, and the higher the strength of the bolt, the higher the risk of occurrence. [0004] The delayed fracture is a kind of environmental embrittlement caused by the interaction of material-environment-stress, and it is considered that the cause is the embrittlement of the material caused by hydrogen. Usually, in order to improve the delayed fracture resistance,...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23C8/10C21D9/00C22C38/00C22C38/22F16B33/06
CPCC22C38/22F16B33/06C23C8/10C23C8/02C23C8/12C23C8/14C22C38/04C22C38/34C23C28/04C23C28/042C21D9/0093C21D9/525C21D1/76C21D3/04C21D1/25C21D9/54C21D6/008C21D6/002C21D6/005C21D8/005C22C38/002C22C38/02F16B33/00
Inventor 浜田孝浩小林大介
Owner NISSAN MOTOR CO LTD
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