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
CN100569406CActive Publication Date: 2009-12-16三野桥株式会社 +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
三野桥株式会社
Publication Date
2009-12-16

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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.
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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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