JP6894095B2 - Fastening structure and fastening method for steel structures - Google Patents

Description

The present invention relates to a fastening structure of a steel structure such as a bridge, which is required to prevent rust over a long period of time, and a fastening method thereof.

Rust prevention is required for a long period of time in steel girders and the like used for structures such as bridges.
Therefore, in the new technical report of NETIS registration number: QS-040005, as a rust preventive method having a long-term rust preventive function rather than rust preventive by painting or sacrificial anticorrosive by hot dip galvanizing, thermal spraying is used on the surface of steel. Disclosed to coat the membrane.
However, even if the steel body is rust-proofed for a long period of time, there is a problem that the joint portion is corroded and red rust is generated because the bolt is not covered with the sprayed film.
Therefore, the applicants have previously proposed a joint structure having excellent long-term rust prevention (Patent Document 1) and an extension for a frame thermal spray gun (Patent Document 2) suitable for the joint structure.
An object of the present invention is to combine them to have excellent workability and enable long-term rust prevention.

Japanese Unexamined Patent Publication No. 2011-99144 Japanese Unexamined Patent Publication No. 2013-173983

An object of the present invention is to provide a fastening structure of a steel structure which is excellent in on-site fastening work and metal spraying property and capable of long-term rust prevention, and a fastening method thereof.

The fastening structure of the steel structure according to the present invention is a fastening structure in which a steel material is fastened with bolts and nuts, and the fastening portion is made of a steel material to be fastened, a steel bolt, a bolt side seat, and a nut and a nut side. The bolt and the bolt side seat are composed of a seat, and the bolt and the bolt side seat have a molten zinc plating layer and a metal spray coating layer formed on the molten zinc plating layer on the bolt head and the bolt side seat, and the nut and the nut side seat have a molten zinc plating layer. On top of that, a lubricant layer is provided on one of the contact surfaces between the nut and the nut side seat, and the exposed portion on the nut side has a metal spray film layer formed on the molten zinc plating layer. It is characterized by.

Here, the bolts and nuts are steel bolts such as hexagonal high-strength bolts.
The bolt side washer is a washer located on the root side of the head of the bolt when tightened with a bolt and a nut, and the nut side washer is a washer that comes into contact with the nut side when tightened.
The exposed part on the nut side means the surface of the nut exposed to the outside after fastening the steel material with the bolt and the nut, the threaded part on the tip side of the bolt, and the exposed part of the washer on the nut side.

The lubricant layer used in the present invention refers to a material having lubricity after application and dipping, such as metal soap, and by having such a lubricant layer on the contact surface between the nut side washer and the nut, the nut can be attached at the time of fastening. The coefficient of friction when the contact surface is rubbed when tightened by turning can be suppressed within a predetermined range.

In the present invention, the metal sprayed coating formed on the exposed portion on the nut side is formed by spraying at the construction site.
The thermal spray gun will be described later.

In the present invention, it is preferable that the total amount of the Pb, Cd, Sn and Bi components contained in the hot-dip galvanized layer is 0.16% by mass or less and the balance is Zn.
As a result, as disclosed in detail in Patent Document 1, gasification of the contained components due to thermal spraying heat is suppressed, and the adhesion of the metal sprayed coating is excellent.

In the present invention, the thermal spray coating layer is preferably made of an Al—Mg-based alloy or a Zn—Al-based alloy.
For example, 5% Mg Al-Mg wire, 15% Al Zn-Al wire and the like can be mentioned as examples.

The method for fastening a steel structure according to the present invention is a fastening method for fastening steel materials with bolts and nuts. After hot-dip zinc plating treatment, the head side of the bolt is sprayed with metal and the threaded portion side is rust-proofed. Yes, the bolt side seat located on the head side of the bolt is metal-sprayed after the hot-dip zinc plating treatment, and the nut is lubricated on the contact surface with the nut side seat after the hot-dip zinc plating treatment, and then rust prevention treatment is applied. The nut side seat is rust-proofed by hot-dip zinc plating, the bolt is inserted into the fastening hole of the steel material to be fastened via the bolt side seat, and the nut is inserted from the tip of the bolt to the nut. It is characterized in that the exposed portion on the nut side is sprayed with metal after the steel material is fastened by tightening through the side seat.
The rust preventive treatment is for preventing oxidation of the hot-dip galvanized surface by chemical conversion coating or the like.

Here, the thermal spraying gun that sprays metal on the exposed portion on the nut side is a frame thermal spraying gun for a narrow portion, and can be sprayed even at a thermal spraying angle of 30 ° or less with respect to the thermal spraying surface and a thermal spraying distance of 2 to 5 cm.

In the present invention, by forming a lubricant layer made of metal soap or the like on the contact surface between the nut and the nut side washer, a predetermined tightening force can be obtained when the nut is tightened.
In addition, after hot-dip galvanizing treatment, chemical conversion treatment is performed using a chrome-based or non-chromium-based solution, and oxidation rust prevention treatment is performed, so that it may last for a long period of 30 to 180 days after hot-dip galvanizing treatment. After fastening, a metal sprayed film having excellent adhesion can be formed.
This makes it possible to perform thermal spraying even at an outdoor erection site without performing blasting immediately before metal spraying.
Furthermore, by using the frame spraying gun for narrow areas, which will be described later, it is possible to concentrate on the necessary parts except for unnecessary parts, so it is possible to suppress wasteful consumption of the thermal spray material and improve the yield. At the same time, it is possible to suppress the generation of so-called sprayed dust around the exposed portion on the nut side.

An example of the surface treatment of bolts, washers, and nuts is shown. (A) shows an example of fastening a steel structure, and (b) shows an exploded view of the fastening portion. Shows the state after fastening with bolts and nuts. (A) shows an example of a frame spraying gun, and (b) shows a partially enlarged view. The structural diagram of the extension part is shown.

The fastening method and a structural example thereof according to the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

FIG. 2 shows an example of fastening steel girders.
This is an example in which the web of the girder and the flange portion 50 are fastened with bolts and nuts via the splicing plates 51 on both sides.
An exploded view of the fastening portion is shown in FIG. 2 (b).
A washer 20 on the bolt side is attached to the bolt 10, passed through a fastening hole provided in the steel material, a washer 30 on the nut side is attached from the tip side of the bolt 10, and the nut 40 is further tightened.

The specifications of bolts and nuts are shown in Fig. 1.
The entire bolt 10 such as a hexagonal high-strength bolt is subjected to a plating treatment (1) by hot-dip galvanizing to form a plating film 1 on the surface.
Next, the parts other than the screw portion 10b such as the head portion 10a and the body portion of the bolt 10 are subjected to metal spraying (2) after the blast treatment to form the thermal spray coating 2.
The thermal spray coating 2 is subjected to a hole-sealing treatment that is usually carried out.
The threaded portion 10b is lightly sweep blasted and subjected to rust preventive treatment (3) such as chromate treatment and non-chrome type chemical conversion treatment to form a rust preventive film 3.
This enables long-term storage of 30 to 180 days until it is used locally according to the construction period.

The bolt side washer 20 is hot-dip galvanized (1) and then metal sprayed.

Similarly, the nut side washer 30 is subjected to sweep blasting after forming the plating film 1, and is subjected to rust prevention treatment (3).

Similarly, in the nut 40, after forming the plating film 1, the contact surface with the nut side washer 30 is lubricated (4) to form a lubricating film 4 such as metal soap.
As a method of forming the lubricating film 4, it may be partially applied to the contact surface, or after forming the lubricating film 4 on the entire nut by dipping or the like, sweep blasting other than the contact surface and the inner threaded portion. The lubricating film 4 may be removed by such means.
Further, sweep blasting may be performed so that the lubricating material easily adheres before forming the lubricating film 4 on the contact surface.
The nut 40 can be subsequently subjected to the rust preventive treatment (3) and stored.

FIG. 3 shows a state in which steel materials are fastened using these bolts, washers, and nuts.
The nut 40, the threaded portion 10b of the bolt 10, and the nut side washer 30 are not formed with a metal sprayed coating at this point.
Therefore, the exposed portion on the nut side shown by the dotted line in FIG. 3 is formed by using a thermal spray gun for a narrow portion while suppressing the generation of thermal spray dust around the exposed portion.
After the thermal spray coating 2 is formed, the usual hole-sealing treatment is performed.
Next, a structural example of the thermal spray gun will be described.
FIG. 4A shows an overall view of the gun 100, and FIG. 4B shows an enlarged view of the tip portion.
FIG. 5 shows a structural example of the extension 110.
The connecting portion 119 of the extension 110 is inserted into the inside of the gun body, and is screwed to the gun body using the joint member 120 with the female screw portion 120a.
A female threaded portion 111a on the rear end side of the extension pipe 111 can be screwed onto the threaded portion 120b at the tip of the joint member 120.
In this embodiment, inside an extension pipe having an outer diameter of about 27 mm, a wire pipe 112 for feeding the radiation ray material M is arranged in the center, and a fuel conduit 114 and oxygen gas for passing fuel gas are arranged on both sides thereof. Oxygen conduits 113 for passing through were arranged in parallel.
The tips of the fuel conduit 114 and the oxygen conduit 113 are connected to the mixing portion 115.
A nozzle 117 is attached to the tip of the mixing portion 115 with a nozzle nut 116, and the rear end portion of the air cap 118 is pressed against the tip step portion of the nozzle nut 116 so that the rear end portion of the air cap 118 is pressed against the tip inner protrusion 111b of the extension pipe 111. This is an example in which the rear end of the extension pipe 111 is screwed to the joint member 120 so as to tighten the step portion on the outer side of the rear end.

As a result, in such a frame spraying gun, oxygen and fuel gas such as acetylene gas are mixed at the tip of the extension 110, and the air flow of the air cap 118 provided at the tip of the extension causes the combustion frame. F is formed.
As a result, the metal sprayed wire M having a wire diameter of 2 to 3 mm can be sufficiently melted with a small combustion flame.
Since the thermal energy is small, the thermal spraying distance can be set to a short distance of 2 to 5 cm.
Further, a sprayed coating having strong adhesion is formed even at a small spraying angle of 30 ° or less and 10 to 20 ° with respect to the sprayed surface.

1 Plating film 2 Spray coating 3 Anti-corrosion film 4 Lubricating film 10 Bolt 20 Bolt side washer 30 Nut Side washer 40 Nut

Claims (2)

It is a fastening method that fastens steel materials with bolts and nuts.
After hot-dip galvanizing the bolt, the head side is sprayed with metal and the threaded side is rust-proofed.
The bolt side washer located on the head side of the bolt is sprayed with metal after hot dip galvanizing.
The nut is hot-dip galvanized, then lubricated on the contact surface with the nut side washer, and then rust-proofed.
The nut side washer is hot-dip galvanized to prevent rust.
The bolt is inserted into the fastening hole of the steel material to be fastened via the bolt side washer, and the nut is tightened from the tip of the bolt via the nut side washer to fasten the steel material, and then the exposed portion on the nut side is exposed. A method for fastening a steel structure, which comprises spraying metal. The thermal spraying gun that sprays metal on the exposed part on the nut side is a frame thermal spraying gun for narrow areas.
Spraying angle 30 ° or less with respect to the sprayed surface, fastening method of claim 1 steel structure, wherein a range of spray distance 2~5cm be sprayed.

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