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Steel wire for bolts, bolt, and methods for manufacturing same

A technology for bolts and steel wires, applied in the field of steel wires for bolts, can solve the problems of water quenching strength deviation, improper rolling temperature and wire drawing processing rate, difficulty in delayed fracture resistance, etc., and achieve excellent delayed fracture resistance. , The effect of preventing crystal coarsening

Inactive Publication Date: 2016-07-20
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, water quenching not only causes significant variation in strength, but also the final rolling temperature and wire drawing ratio are not appropriate, so it is difficult to exhibit the same delayed fracture resistance as standard alloy steel
[0007] In this way, the same delayed fracture resistance as standard alloy steel cannot be obtained in the technology proposed so far.

Method used

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  • Steel wire for bolts, bolt, and methods for manufacturing same
  • Steel wire for bolts, bolt, and methods for manufacturing same
  • Steel wire for bolts, bolt, and methods for manufacturing same

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Embodiment

[0140] Hereinafter, the present invention is described in more detail by enumerating the examples, but the present invention is not limited by the following examples, and can also be modified and implemented within the scope of being able to meet the purpose of the foregoing and the following, and these are all included in the technical scope of the present invention Inside.

[0141] After melting the steel materials of steel types A to Z shown in Table 1 below, a steel billet with a square cross section and 155 mm in one side was produced. In addition, "tr." in Table 1 indicates that it is lower than the analysis limit value of each element. Thereafter, the billet is processed into a wire rod (process 1), the wire rod is processed into a bolt wire (process 2), the bolt wire is processed into the shape of a head molded product (process 3), and the head molded product is processed into a bolt ( Step 4), making various flange bolts (tensile strength 1000-1400MPa, M10-14 (coarse...

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Abstract

Provided are: a high-strength bolt that has a tensile strength of 1,000-1,400 MPa and a delayed fracture resistance that is on par with standard steel alloys even when Mo and Cr are omitted or reduced with respect to SCM steel or SCr steel; a steel wire for a bolt that is for producing the aforementioned high-strength bolt; and a useful method for producing the bolt and the steel wire for a bolt. The steel wire for a bolt satisfies a predetermined chemical composition. With regard to the boron content of the surface of the steel wire for a bolt, when the diameter of the steel wire for a bolt is denoted by D0 and the boron content of a D0 / 4 portion of the steel wire for a bolt is 100%, the average proportion of the boron content of the surface of the steel wire for a bolt is 75% or less and the difference between the maximum value and the minimum value of this proportion is 25% or less. The prior austenite grain size number in an area from the surface of the steel wire for a bolt to a depth of 100 [mu]m is no.8 or higher.

Description

technical field [0001] The present invention relates to bolts used in automobiles and various industrial machines, steel wires for bolts used for manufacturing the bolts, and a method for manufacturing the bolts. Specifically, it relates to a high-strength bolt exhibiting excellent delayed fracture resistance even at a high tensile strength of 1,000 to 1,400 MPa, a steel wire for bolts used for manufacturing the above-mentioned high-strength bolt, and a steel wire for manufacturing them. useful method. Background technique [0002] Bolts used for the above-mentioned applications tend to cause delayed fracture if the tensile strength is 1000 MPa or more. Conventionally, standard alloy steels such as SCM (Steel Chromium Molybdenum) steel and SCr (Steel Chromium) steel specified in JISG4053 have been used as raw materials for high-strength bolts with a tensile strength of 1000 MPa or more. However, in recent years, boron-added (B) steel, which can omit or simplify the steps o...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D8/06C21D9/00C22C38/32C22C38/54F16B35/00
CPCC21D8/06C21D9/00C22C38/00C22C38/32C22C38/54F16B35/00C21D8/065C21D9/0093C22C38/001C22C38/002C22C38/008C22C38/02C22C38/04C22C38/06C22C38/18C22C38/22C22C38/24C22C38/26C22C38/28C22C38/42C22C38/44C22C38/48C22C38/50C22C38/20B21K1/46F16B33/06
Inventor 松本洋介千叶政道
Owner KOBE STEEL LTD
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