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

A technology of high-strength bolts and manufacturing methods, applied in the directions of screws, threaded fasteners, connecting components, etc., can solve the problems of uneconomical, uneven delayed damage resistance of high-strength bolts, and the incidence of defective bolts, so as to avoid damage. and bite, eliminating the unevenness of delayed failure, good lubricity

Active Publication Date: 2005-11-02
三野桥株式会社 +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] This decarburization method makes the delayed failure resistance of high-strength bo

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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Experimental program
Comparison scheme
Effect test

Embodiment Construction

[0018] The best mode for carrying out the present invention will be described below with reference to the drawings.

[0019] (1) Application of lubricating film

[0020] 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.

[0021] The 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.

[0022] The lubricating film layer 2 is composed of an inorganic salt lubricating film 3 directly coated on the surface...

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PUM

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Abstract

The invention relates to high-strength screw steel wire which has excellent delayed failure resistance and cold rolling plastic working property, and the producing method of high-strength bolt. Said invention coats the steel wires with following new lubricating coating for cold rolling plastic property process. The inorganic salt lubricating coating which covers the contacted surface of steel wires, and the non-phosphate special lubricating coating which laminates on aforementioned the coating, integrates said new lubricating coating as multiply layers coating. The optimization of aforementioned inorganic salt lubricating coating is potassium silicate while optimization for the special lubricating coating is calcium stearate. Excellent process of cold rolling plastic property is operated on high-strength after coated new lubricating coating with steel wires. Then the surface layer of steel are heating with decarbonization control to the set depth, and the high-strength screw steel wire which has excellent delayed failure resistance and cold rolling plastic working property is attained.

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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IPC IPC(8): F16B35/00
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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