JP2004232757A - Method of manufacturing high tensile bolt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high tensile bolt manufacturing method for improving delayed-fracture resistance, and preventing the deterioration in quality by a shot blast. <P>SOLUTION: A screw part nonexistent bolt of a desired bolt shape is provided by performing cold forging on a raw material for a bolt covered with a phosphate coating film. Next, the phosphate coating film of a surface part of this screw part nonexistent bolt is reduced by the shot blast. Next, after this shot blast, heat treatment is performed after performing screw rolling being the formation of a screw part. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a high-strength bolt having a tensile strength of 1200 N / mm ² or more.
[0002]
[Prior art]
Conventionally, for example, thread rolling or the like is performed on a bolt material coated with a phosphate film (bonding film), which is a lubricating film for improving cold headability, and a threaded portion having a threaded portion is provided. A step of obtaining a bolt, a step of reducing the phosphate film on the surface of the obtained bolt having a threaded portion by shot blasting, and a step of performing heat treatment (quenching and tempering) after the shot blasting. A method for manufacturing a high-strength bolt is known.
[0003]
According to such a method for manufacturing a high-strength bolt, since the phosphate coating is reduced by shot blasting before the heat treatment, the phosphorus component of the phosphate coating can be prevented from penetrating into the bolt during the heat treatment, Therefore, the delayed fracture resistance can be improved (for example, see Patent Document 1).
[0004]
When a lime lubricating film is used instead of the phosphate film, the use of lime lubricating film is limited because of the problems of cold heading, rusting of the material due to moisture absorption and discoloration after heat treatment. It is a fact.
[0005]
[Patent Document 1]
JP-A-6-229409 (page 1, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, since the conventional method for manufacturing a high-strength bolt involves performing shot blasting after forming the threaded portion, the threaded portion may be easily damaged during shot blasting, and the quality of the threaded portion may be degraded.
[0007]
The present invention has been made in view of the above points, and provides a method of manufacturing a high-strength bolt capable of not only improving the delayed fracture resistance, but also preventing a decrease in the quality of a thread portion due to shot blasting. The purpose is to:
[0008]
[Means for Solving the Problems]
The method for manufacturing a high-strength bolt according to claim 1 is a method for manufacturing a high-strength bolt having a tensile strength of 1200 N / mm ² or more, and cold forging a bolt material coated with a phosphate coating. Performing a step of obtaining a screw part boltless by performing, a step of reducing the phosphate coating on the surface of the obtained screwless bolt by shot blast, and a step of performing screw part formation and heat treatment after the shot blast. It is provided with.
[0009]
And after reducing the phosphate coating of the bolt part without bolt obtained by cold heading by shot blasting, since the thread part formation and heat treatment are performed, delayed fracture resistance is improved and shot blasting is performed. Deterioration of the quality of the thread is prevented.
[0010]
The method of manufacturing a high-strength bolt according to claim 2 is the method of manufacturing a high-strength bolt according to claim 1, wherein the material for the bolt is C: 0.15 to 0.50% by mass, and Si: 0.35% by mass. Hereinafter, Mn contains 0.30 to 1.50% by mass, P: 0.03% by mass or less, S: 0.03% by mass or less, and Cr: 0.10 to 1.50% by mass. It contains at least one of V, Ti, Al and B, with the balance being Fe and unavoidable impurities.
[0011]
By using a bolt material made of a predetermined component, a high-strength bolt having a tensile strength of 1200 N / mm ² or more can be appropriately obtained.
[0012]
The method for manufacturing a high-strength bolt according to claim 3 is the method for manufacturing a high-strength hexagonal bolt or a torcia-type high-strength bolt according to the method for manufacturing a high-strength bolt according to claim 2.
[0013]
In addition, a high-strength hexagonal bolt or a torcia-type high-strength bolt excellent in delayed fracture resistance and stable in quality and having a tensile strength of 1200 N / mm ² or more can be appropriately obtained.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment of a method for manufacturing a high-strength bolt according to the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a manufacturing process diagram of a high-strength hexagonal bolt which is a high-strength bolt (high-strength bolt) having a tensile strength of 1200 N / mm ² or more and a tensile strength of 1600 N / mm ² or less used for construction of various structures, for example. It is. The high-strength hexagon bolt is, for example, a high-strength hexagon bolt of Japanese Industrial Standard JIS-B-1186.
[0016]
When manufacturing a high-strength hexagon bolt, first, a bolt material (for example, a spiral-wound wire steel material) is selected according to the type (size, etc.) of the high-strength hexagon bolt (Step 1).
[0017]
Here, the bolt material has been subjected to a lubricating film treatment, and its surface is coated with a phosphate film (bonding film) which is a lubricating film for improving cold headability. .
[0018]
That is, the material for bolts is, for example, C: 0.15 to 0.50% by mass, Si: 0.35% by mass or less, Mn: 0.30 to 1.50% by mass, P: 0.03% by mass or less, S: 0.03% by mass or less, Cr: 0.10 to 1.50% by mass, and one or more of Mo, V, Ti, Al and B, the balance being Fe and unavoidable impurities. On the surface of the bolt material, a phosphate film having a lubricant is formed by a lubricating film process (bonding process).
[0019]
Next, the bolt material coated with the phosphate film is cut into a predetermined length (Step 2), and the cut bolt material is subjected to cold heading, as shown in FIG. A threadless bolt 1 having a desired bolt shape shown in a) is obtained (step 3).
[0020]
The screwless bolt 1 shown in FIG. 2A has a shaft portion 2 and a head portion 3 integrally provided at a base end of the shaft portion 2. A phosphate coating 4 is formed on the outer peripheral surface of the shaft 2 and the outer peripheral surface of the head 3. In addition, the screw part is not formed in the front end side of the shaft part 2 of the screw part no bolt 1.
[0021]
Next, after performing the degreasing treatment (oil removing treatment) on the threadless bolt 1 obtained in the above (Step 3) (Step 4), the phosphorus on the surface of the degreasing screwless bolt 1 is removed. The acid salt coating 4 is reduced by shot blasting to obtain a shot-blasted screwless bolt 6 shown in FIG. 2B (step 5).
[0022]
At this time, for example, by using the shot blasting device 7 shown in FIG. 3, shot blasting is performed for each bolt group 1a including a plurality of bolts (for example, about 3000 bolts in the case of a shaft diameter of 22 volts). I do.
[0023]
That is, for example, while the bolt group 1a is mixed by the rotation of the belt 8 as a rotating body, the shot particles 9 circulating and moving against each threadless bolt 1 of the bolt group 1a on the belt 8 are collided, and the shot particles 9 collide. The phosphate coating 4 is thereby removed from the outer peripheral surface of the shaft 2 and the outer peripheral surface of the head 3.
[0024]
At the time of shot blasting, since the threaded portion is not formed in the threaded portionless bolt 1, the threaded portion is damaged due to the collision between the shot particles 9 and the threaded portion, or the threaded portions due to the rotation of the belt 8. There is no possibility that the screw part is damaged due to the collision of the tire.
[0025]
Then, after shot blasting using such a shot blasting device 7, screw portion formation and heat treatment are performed.
[0026]
In other words, for example, the shot-blasted threadless bolt 6 obtained in the above (Step 5) is subjected to thread rolling for forming a threaded portion to have a threaded portion 10 as shown in FIG. 2C. The threaded bolt 11 is obtained (step 6).
[0027]
Subsequently, heat treatment (quenching and tempering, etc.) is performed on the obtained threaded bolt 11 (step 7), and the delayed fracture resistance is excellent, and the threaded portion 10 has no damage and is stable in quality. A high strength hexagonal bolt having a tensile strength of 1200 N / mm ² or more is obtained.
[0028]
In addition, since the phosphate coating 4 has already been reduced by shot blasting during the heat treatment, the phosphorus component of the phosphate coating 4 does not penetrate into the threaded bolt 11.
[0029]
As described above, according to the method for manufacturing a high-strength hexagonal bolt according to the first embodiment, the phosphate coating 4 of the threadless bolt 1 having the desired bolt shape obtained by cold heading is used as a bolt group. Since the heat treatment is performed after forming the thread portion (screw rolling) after reducing by shot blasting for each 1a, it is possible to efficiently perform shot blasting and to improve delayed fracture resistance. In addition to being able to do so, it is possible to prevent quality deterioration due to scratching of the screw portion 10 due to shot blasting and the like.
[0030]
Next, a second embodiment of the method for manufacturing a high-strength bolt of the present invention will be described with reference to the drawings.
[0031]
FIG. 4 is a manufacturing process of a torsia-type high-strength bolt which is a high-strength bolt (high-strength bolt) having a tensile strength of 1200 N / mm ² or more and a tensile strength of 1600 N / mm ² or less, which is used for construction of various structures, for example. FIG.
[0032]
The torsia-type high-strength bolts include, for example, a torsia-type high-strength bolt of JSSII-09 of the Japan Steel Construction Association standard and a torsia-type ultra-high-strength bolt of trade name “SHTB”.
[0033]
When manufacturing a torcia-type high-strength bolt, first, a bolt material (for example, a spiral-wound wire steel material) is selected according to the type (size, etc.) of the torcia-type high-strength bolt (step 11). ).
[0034]
Here, the material for the bolt has been subjected to a lubricating film treatment, and its surface is coated with a phosphate film (bonding film) which is a lubricating film for improving cold forging property. .
[0035]
That is, the material for bolts is, for example, C: 0.15 to 0.50% by mass, Si: 0.35% by mass or less, Mn: 0.30 to 1.50% by mass, P: 0.03% by mass or less, S: 0.03% by mass or less, Cr: 0.10 to 1.50% by mass, and one or more of Mo, V, Ti, Al and B, the balance being Fe and unavoidable impurities. On the surface of the bolt material, a phosphate film having a lubricant such as bonder lube is formed by a lubricating film process (bonding process).
[0036]
Next, the bolt material coated with the phosphate film is cut into a predetermined length (step 12), and the cut bolt material is subjected to cold heading, as shown in FIG. A threadless bolt 21 having a desired bolt shape shown in a) is obtained (step 13).
[0037]
5A includes a shaft portion 22, a head portion 23 integrally provided at a base end of the shaft portion 22, and a pin tail portion integrally provided at a distal end of the shaft portion 22. 25. A phosphate coating 24 is formed on the outer peripheral surface of the pin tail portion 25, the outer peripheral surface of the shaft portion 22, and the outer peripheral surface of the head portion 23. In addition, the screw part is not formed in the front end side of the shaft part 22 of the screw part no bolt 21.
[0038]
Next, after performing the degreasing process (oil removing process) on the threadless bolt 21 obtained in the above (Step 13) (Step 14), the phosphorus on the surface of the degreasing screwless bolt 21 is removed. The salt film 24 is reduced by shot blasting to obtain a shot-blasted screwless bolt 26 shown in FIG. 5B (step 15).
[0039]
At this time, for example, as in the case of the first embodiment, by using the shot blasting device 7 shown in FIG. Shot blasting is performed for each bolt group 21 a composed of 21.
[0040]
That is, for example, while the bolt group 21a is mixed by the rotation of the belt 8, which is a rotating body, the shot particles 9 circulating and moving against each threadless bolt 21 of the bolt group 21a on the belt 8 collide with each other. As a result, the phosphate film 24 is removed from the outer peripheral surface of the pin tail portion 25, the outer peripheral surface of the shaft portion 22, and the outer peripheral surface of the head portion 23.
[0041]
At the time of shot blasting, since the threaded portion is not formed in the threaded portion boltless 21, the threaded portion is damaged by the collision between the shot particles 9 and the threaded portion, or the threaded portions are caused by the rotation of the belt 8. There is no possibility that the screw part is damaged due to the collision of the tire.
[0042]
Then, after shot blasting using such a shot blasting device 7, screw portion formation and heat treatment are performed.
[0043]
That is, for example, thread rolling and fracture groove rolling for forming a thread portion are performed on the shot blasted threadless bolt 26 obtained in the above (Step 15), as shown in FIG. The threaded bolt 31 having the threaded portion 30 and the break groove 33 is obtained (step 16).
[0044]
Subsequently, heat treatment (quenching and tempering, etc.) is performed on the obtained threaded bolt 31 (step 17), which is excellent in delayed fracture resistance, has no damage on the threaded portion 30, and is stable in quality. A torsia-type high-strength bolt having a tensile strength of 1200 N / mm ² or more is obtained.
[0045]
In addition, since the phosphate coating 24 has already been reduced by shot blasting during the heat treatment, the phosphorus component of the phosphate coating 24 does not permeate into the bolt 31 having the screw portion.
[0046]
As described above, according to the method for manufacturing the torcia-type high-strength bolt according to the second embodiment, the phosphate coating 24 of the threadless bolt 21 having the desired bolt shape obtained by cold heading is bolted. After reducing by shot blasting for each group 21a, heat treatment is performed after thread formation (screw rolling and fracture groove rolling), so that shot blasting can be performed efficiently and delayed fracture resistance Not only can be improved, but also the quality can be prevented from deteriorating due to damage of the screw portion 30 due to shot blasting.
[0047]
In the above embodiment, the case where the thread portions 10 and 30 are formed by thread rolling has been described. However, the thread portions 10 and 30 may be formed by thread cutting, for example.
[0048]
Further, the method is not limited to the method in which the heat treatment is performed after the formation of the screw portion after the shot blast, and the heat treatment may be performed after the formation of the screw portion after the shot blast.
[0049]
Furthermore, the present invention is not limited to the method in which the shot blast is performed for each of the bolt groups 1a and 21a including the plurality of threaded bolts 1 and 21 to reduce the phosphate coating 24, and the shot blast may be performed one by one. Good.
[0050]
The details of the components and shapes of the bolt material (high-strength bolt steel) and high-strength bolts (high-strength hexagon bolt, torcia-type high-strength bolt, etc.) are described in Japanese Patent Publication No. 6-89768 and Japanese Unexamined Patent Publication No. -278735 and JP-A-2002-276637.
[0051]
【The invention's effect】
According to the present invention, since the thread portion is formed and the heat treatment is performed after reducing the phosphate coating of the bolt portion without bolts obtained by cold heading by shot blasting, the delayed fracture resistance is improved. In addition to the above, it is possible to prevent deterioration in quality due to shot blasting.
[Brief description of the drawings]
FIG. 1 is a manufacturing process diagram of a high-strength hexagon bolt according to a first embodiment of the present invention.
FIGS. 2A and 2B are schematic sectional views of a high-strength hexagonal bolt in the process of manufacturing, in which FIG. 2A is a sectional view before shot blasting, FIG. 2B is a sectional view after shot blasting, and FIG. It is sectional drawing after fabrication.
FIG. 3 is a schematic view of a shot blasting apparatus that performs shot blasting.
FIG. 4 is a manufacturing process diagram of the torcia-type high-strength bolt according to the second embodiment of the present invention.
5A and 5B are schematic cross-sectional views of a torcia-type high-strength bolt in the process of manufacturing, wherein FIG. 5A is a cross-sectional view before shot blast, FIG. 5B is a cross-sectional view after shot blast, and FIG. It is sectional drawing after rolling and a fracture groove | channel.
[Explanation of symbols]
1,21 screw part no bolt 4,24 phosphate coating

Claims (3)

A method for producing a high-strength bolt having a tensile strength of 1200 N / mm ² or more,
A step of performing cold heading on the bolt material coated with the phosphate coating to obtain a screw-less bolt,
A step of reducing the obtained phosphate coating on the surface of the screwless bolt by shot blasting,
A step of forming a screw portion and performing a heat treatment after the shot blasting. The bolt material is
C: 0.15 to 0.50% by mass;
Si: 0.35% by mass or less,
Mn: 0.30 to 1.50% by mass,
P: 0.03% by mass or less,
S: 0.03% by mass or less,
Cr: 0.10 to 1.50% by mass and at least one of Mo, V, Ti, Al and B,
2. The method according to claim 1, wherein the balance comprises Fe and inevitable impurities. The method for producing a high-strength bolt according to claim 2, wherein the method is a method for producing a high-strength hexagon bolt or a torcia-type high-strength bolt.

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