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Steel wire for high-tension bolts and method for manufacturing high-tension bolts

A technology of high-strength bolts and manufacturing methods, which is applied in the direction of bolts, screws, threaded fasteners, etc., can solve problems such as the incidence of defective bolts, uneven resistance to delayed failure of high-strength bolts, and uneconomical problems, and achieve the elimination of delayed failure Good non-uniformity, anti-sintering, and the effect of avoiding breakage and bite

Active Publication Date: 2009-12-16
三野桥株式会社 +1
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  • Summary
  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

[0009] This decarburization method makes the delayed failure resistance of high-strength bolts uneven, and the incidence of defective bolts is several percent, which is uneconomical.

Method used

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  • Steel wire for high-tension bolts and method for manufacturing high-tension bolts
  • Steel wire for high-tension bolts and method for manufacturing high-tension bolts
  • Steel wire for high-tension bolts and method for manufacturing high-tension bolts

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Embodiment Construction

[0019] The best mode for carrying out the present invention will be described below with reference to the drawings.

[0020] (1) Application of lubricating film

[0021] Such as figure 1 As shown, when high-strength bolts are manufactured using steel wire for high-strength bolts as a base, steel wires such as SCM435, 440H and boron steel are coated with a lubricating film and then drawn to a specified diameter. Furthermore, cold-rolled plastic processing is performed so that the overall shape of the bolt head and the bolt shaft portion appears, and the semi-finished bolt is heat-treated. Finally, the thread is threaded on the shaft of the bolt to obtain a high-strength bolt.

[0022] The present invention as figure 2 As shown, the surface of the steel wire 1 is coated with a lubricating coating layer 2 of a multi-layer structure that has never been seen before.

[0023] The lubricating film layer 2 is composed of an inorganic salt lubricating film 3 directly coated on the...

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Abstract

The present invention relates to a steel wire for high-strength bolts excellent in delayed fracture resistance and cold-rolled plastic workability, and a method for producing high-strength bolts. The present invention is a steel wire for high-strength bolts because it exhibits good cold-rolled plastic workability and excellent delayed fracture resistance. The steel wire is coated with the following new lubricating coating layer and subjected to cold-rolled plastic working. The new lubricating coating layer is a multi-layered coating composed of an inorganic salt lubricating coating coated on the surface of the contact wire and a non-phosphorus special lubricating coating laminated on the inorganic salt lubricating coating. Potassium silicate is preferred as the above-mentioned inorganic salt-based lubricating coating, and calcium stearate is preferred as the special lubricating coating. The above-mentioned steel wire for high-strength bolts coated with a new lubricating film layer is subjected to good cold-rolled plastic processing. Next, heat treatment is performed to control the decarburization of the steel surface layer to a specified depth, and high-strength bolts with excellent delayed fracture resistance can be obtained.

Description

technical field [0001] The present invention relates to a steel wire (steel wire) for high-strength bolts excellent in delayed fracture resistance and cold-rolled plastic formability, and a method for manufacturing high-strength bolts. Background technique [0002] In strength over 1000N / mm 2 In the high-strength bolts of high-strength bolts, after many years, the so-called delayed failure in which the top of the bolt falls off or the shaft of the bolt breaks occasionally occurs. [0003] As the biggest cause of delayed fracture, it is known that the surface of the steel wire is coated with a phosphate lubricating film in order to ensure excellent ductility during cold rolling plastic working. [0004] The composition of the phosphate film is composed of a phosphate film such as zinc phosphate or zinc calcium phosphate mixed with a lubricant such as metal soap. However, the phosphorus component in it is infiltrated during heat treatment and forms an embrittlement layer on t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B21C9/00B21K1/44C21D3/04F16B35/00
Inventor 大竹洋平西乡史隆土屋典雄儿玉等
Owner 三野桥株式会社
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