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High-strength bolt excellent in delayed fracture resistance characteristics and its steel product

A high-strength bolt and high-strength technology, applied in the direction of bolts, screws, nuts, etc., can solve the problems of delayed fracture of bolts that cannot reach the strength

Inactive Publication Date: 2006-01-11
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This can reduce the stress concentration acting on the threaded part 3, but even with such a shape, the stress concentration factor acting on the central part M of the thread root 4c of the threaded thread 4 is 2.54, which corresponds to 1200N / mm 2 When the standard bolt tension of the above tensile strength is stretched along the X-X direction of the bolt axis, the thread root of the thread tooth only produces plastic strain, which cannot reach 1200N / mm 2 Treatment of delayed fracture occurrence of high-strength bolts above tensile strength

Method used

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  • High-strength bolt excellent in delayed fracture resistance characteristics and its steel product
  • High-strength bolt excellent in delayed fracture resistance characteristics and its steel product
  • High-strength bolt excellent in delayed fracture resistance characteristics and its steel product

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0084] Use the steel for the test with the chemical composition shown in the following table 1, hot-roll it into a wire rod with a wire diameter of Ф21.5mm, use the various wire rods obtained, and make the threaded part M22 (JIS metric standard bolt of F10T) There are two types of bolts in the conventional shape and the shape of the present invention. Then, through quenching and tempering, the tensile strength of the bolt is 1200N / mm 2 ~1700N / mm 2 Adjust within the range. At this time, the tensile strength is adjusted by the composition and tempering temperature, and the tempering temperature is in the range of 290°C to 700°C. Table 2 shows the tempering temperature and tensile strength at this time.

[0085]

Steel for test

Chemical composition (mass%)

C eq

C

Si

mn

P

S

Cr

Mo

Al

V

Ni

Ti

Nb

1

2

3

4

5

6

7

8

9 ...

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PUM

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Abstract

The present invention provides a high strength bolt superior in delayed fracture resistant property having a bolt tensile strength of 1200 N / mm<2> or more and a steel material for the same. <??>A high strength bolt comprised of a head portion and shaft portion formed by a steel material, wherein the relation between a bolt tensile strength TS (N / mm<2>) and tempering temperature T ( DEG C) satisfies the following expression (1), the relation between the bolt tensile strength TS (N / mm<2>) and the carbon equivalent Ceq (%) calculated from the chemical composition of the steel material used for the high strength bolt satisfies the following expression (2), and the tensile strength of the bolt is refined to a range of 1200 N / mm<2> to 1600 N / mm<2> by quenching and tempering: <DF NUM="(1)">TS≤.1T+850 < / DF> <DF NUM="(2)">TS≤550Ceq+1000 < / DF> where, <DF>Ceq=C+(Mn / 6)+(Si / 24)+(Ni / 40) +(Cr / 5)+(Mo / 4)+(V / 14) < / DF>

Description

technical field [0001] The present invention relates to high-strength bolts and their steel materials used for construction such as civil engineering, construction or various machinery and equipment structures, and in particular to bolts with 1200N / mm 2 High-strength bolts and steel products with excellent tensile strength and delayed fracture resistance of the above-mentioned bolts. Background technique [0002] As is well known, when joining steel materials used in various industrial fields, in addition to various welding joining methods, bolt joining methods are generally used. In such a bolt joint method, the high strength of steel is promoted in pursuit of economy and technological progress, and especially in the fields of civil engineering and construction, friction of high-strength bolts with high joint reliability and excellent operability are often used. Joining method. [0003] As high-strength bolts for frictional joints, for example, sets of high-strength hexag...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D9/00F16B35/00C22C38/00C22C38/24C21D1/18C22C38/06C22C38/22C22C38/28C22C38/44C22C38/46F16B33/02
CPCC22C38/46C21D1/18F16B35/00C22C38/06C22C38/22C22C38/44C22C38/24F16B33/02C21D9/0093
Inventor 宇野暢芳蟹泽秀雄
Owner NIPPON STEEL CORP
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