JP5599027B2 - Long-term anti-rust joint structure - Google Patents

Description

  The present invention relates to a bonded structure made of a steel material and excellent in rust prevention, and in particular, by spraying after bolt fastening joining, it is possible to eliminate the thermal spraying of the fastening surface of the bolt, which is effective in reducing the axial force reduction rate due to relaxation. The present invention relates to a bonded structure capable of long-term rust prevention and a construction method thereof.

In steel girders used for structures such as bridges, rust prevention is required for a long period of time.
Therefore, in the new technical report (Non-Patent Document 1) of NETIS registration number: QS-040005, as a rust prevention method having a long-term rust prevention function rather than sacrificial corrosion prevention by coating or hot dip galvanization, a thermal spray material is applied to steel. To coat the surface with a sprayed film.
However, even if the steel body is rusted for a long period of time, there is a problem that the sprayed film is not coated on the bolt and the joint is corroded and red rust is generated.
The biggest reason for this is that when the bolts coated with the sprayed film are joined, the friction caused by rotational friction during tightening will leave scratches on the sprayed film and the antirust effect cannot be expected. This is because the number of sprayed coating surfaces is doubled compared to the case of coating, and the axial force is greatly reduced by relaxation caused by the sprayed coating portion of the bolt.
For example, Non-Patent Document 2 reports that the axial force of relaxation is reduced even in the case of bolts coated with hot dip galvanizing compared to the case where there is no plating film on the joint surface.
Therefore, it is not only expected that coating the sprayed coating on the hot-dip galvanized bolts for the purpose of long-term rust prevention, but also the conventional hot-dip galvanized coating will not form the sprayed coating normally. There were many.

  Patent Document 1 discloses a technique in which hot dip galvanization is performed on an iron product and then zinc is sprayed. However, there is a problem in the adhesion of the sprayed film, and it cannot be applied to a bonded structure using bolts.

JP 2006-37217 A

NETIS registration number: QS-040005 Technical name: Plas wire construction method Summaries of Technical Papers of Annual Meeting Architectural Institute of Japan (Kinki) September 1980 2412 Study on high strength bolted plating

An object of the present invention is to provide a bonded structure excellent in long-term rust prevention and a method of manufacturing a bolt used therefor while suppressing a reduction in axial force due to relaxation when bolting steel materials.
Moreover, it aims at provision of the construction order (construction method) for preventing the rubbing damage | wound of a long-term rust preventive film by bolting.

In the long-term rust prevention structure according to the present invention, the total of Pb, Cd, Sn and Bi components is 0. 16 mass% or less , Cu component is 0.20 mass% or less, Al component is 0.005 mass% or less, and the bolt is used to form a hot dip galvanized film using a plating bath consisting of Zn and inevitable impurities. Thereafter, the bolt is covered with a sprayed film.
In addition, as a specific example of the structure, a pair of steel materials each having a bolt hole and having a surface coated with a sprayed film are butt-matched, and the paired steel materials are coated with a sprayed film on the surface. And the bolts are joined to each other after fastening joining using a bolt in which a hot dip galvanized film having a total of Pb, Cd, Sn and Bi components of 0.16% by mass or less is formed with respect to the plated film. The example which coat | covered the sprayed film is mentioned.
In this case, the bolt has a hot dip galvanized coating on the entire surface, and the total of Pb, Cd, Sn and Bi components contained in the hot dip galvanized coating is 0.16% by mass or less based on the plated coating. Therefore, the gasification of the low melting point component can be suppressed against heat generation during thermal spraying, and the adhesion of the thermal sprayed film sprayed thereon is excellent.
Moreover, spraying after fastening the bolt means that there is no thermal spray film on the fastening contact surface of the bolt, and the relaxation can be reduced to that extent.
In this case, the structure is formed by joining a plurality of web and flange members, the web is bolted and joined via the web attachment plate, and the flange is bolted and joined via the flange attachment plate. The web, flange, web attachment plate and flange attachment plate are coated with a sprayed coating on the surface, and the total of Pb, Cd, Sn and Bi components is 0. Long-term rust prevention of a joint part is attained because the said thermal spray film | membrane is coat | covered to the said volt | bolt after fastening joining using the volt | bolt which formed the hot dip galvanization film of 16 mass% or less.
In this case, as a manufacturing method of the thermal spraying bolt, a hot dip galvanized film having a total of Pb, Cd, Sn and Bi components of 0.16% by mass or less is coated, and then blasting and primary rust prevention as necessary. It is advisable to adopt a method for performing processing.

In the present invention, since it is possible to thermally spray the bolt after the steel material is fastened and joined with the bolt, there is no relaxation caused by the thermal sprayed film of the bolt when the bolt is preliminarily bonded, and the bolt is in close contact after fastening. By covering the sprayed film with excellent properties, no bolt tightening flaws remain, and the entire joint can be rust-prevented for a long period of time.
Further, in the conventional thermal spraying technique, in order to ensure a predetermined amount of thermal spraying, it is necessary to perform thermal spraying quickly after the blast treatment, before rust is generated and dust or dust does not adhere to the steel material surface.
Therefore, in the conventional thermal spraying technique, there is no construction environment in which outdoor spraying can be performed.
On the other hand, on the surface of the above hot dip galvanized coating, it enables outdoor thermal spraying work by using a plating coating that has been subjected to primary rust prevention treatment by chemical conversion coating (short-term rust prevention treatment by chemical conversion coating) as a base for thermal spraying, Adhesion can be maintained even if exposed outdoors before thermal spraying, so it is only necessary to perform thermal spraying within a predetermined number of days after fastening and joining at the site, providing excellent on-site workability.

The example of a joining structure is shown, (a) shows the whole perspective view, and (b) shows the exploded view of a joined part. The component table | surface of the hot dip galvanization used for evaluation is shown. Indicates the size of the test piece. The thermal spraying condition and evaluation method of a test piece are shown. An evaluation result is shown. The thermal spraying conditions evaluated are shown. The thermal spraying conditions and the evaluation results of the adhesion of the sprayed film are shown. The treatment conditions after plating and the evaluation conditions for the adhesion are shown. The adhesion evaluation result of the thermal spray film by the presence or absence of primary rust prevention treatment is shown. The result of investigating the influence of the outdoor exposure period is shown. The chemical composition in a plating film and the adhesion evaluation result of a thermal spray film are shown.

An example of a structure according to the present invention is shown in FIG.
The present invention is characterized in that a hot-dip galvanized bolt is used and the thermal spray film can be coated on the bolt after the bolt is fastened. The invention is not limited to this embodiment.
The present embodiment is an example of a steel girder in which a plurality of H-section steels composed of a web 12 and a flange 11 are bolted and joined.
Each of the pair of left and right webs 12 has a bolt hole, butts the webs, abuts the web attaching plate 13 to the abutting portion, and inserts the bolt 20 from the bolt hole provided also in the web attaching plate 13. This is an example of fastening and joining.
The flange 11 also has a bolt hole 11 a, the flange attachment plates 14 and 15 are brought into contact with both surfaces of the abutting portion, the bolt 20 is inserted into the bolt holes 14 a and 15 a like the web, and the nut 21 is fastened and joined. To do.
Moreover, washers 20a and 21a are used as necessary.

In this case, the flange 11, the web 12, and each splice plate are sprayed with a gas flame spraying, arc spraying, plasma spraying means, etc., using Al-5% Mg alloy or Zn-Al alloy spraying material. The bolt 20, the nut 21, and the washers 20a, 21a are subjected to hot dip galvanizing described later on the entire surface, and after the fastening, the thermal spray film is coated with the thermal spray material.
Therefore, since the sprayed film is formed on the bolt and nut as well as the web, flange, and attachment plate, it is possible to prevent rust for a long period of time. Thermal spraying is performed on the contact surface of the web, flange attachment plate, etc. on the bolt, nut and washer. Less relaxation due to the absence of membranes.

Next, the examination result about the processing method of hot dip galvanization is demonstrated.
Using a hot dip galvanizing bath having a composition as shown in FIG. 2, hot dip galvanizing is performed on an iron plate having a size as shown in FIG. 3 at a bath temperature of 450 ° C., and then, as shown in FIG. The thinner was wiped, and the left side was lightly air-blasted with Alundum # 60 (Sansho Abrasive Co., Ltd.).
The test piece is coated with a thermal spray film (pw thermal spraying) using an Al-5% Mg, φ1.6 thermal spray material, and the appearance evaluation and adhesion force measurement of the thermal spray film (Techno Tester R-2000D) Used).
The conditions are shown in a table in FIG. 4, and the measurement results are shown in FIG.
In FIG. 5, the measurement positions a, b, c, and d are the portions shown in FIG. 3, where a and b are lightly blasted portions and c and d are the portions wiped with thinner.
TPNo. No. of the plating bath. The film thickness of the sprayed film was determined by subtracting the film thickness of the plating film from the measured total film thickness.
In Comparative Example 1 (plated film shown in paragraph 0006) by conventional hot dip galvanization, the sprayed film peeled off, and the spraying itself could not be performed.
As a result, the product of the present invention had much less scorching during thermal spraying and repelling of the thermal spray coating as compared with the comparative example even with degreasing treatment only by thinner wiping.
However, NO. It became clear that 1 and 2 were not sufficient for degreasing alone, and it was preferable to lightly blast.
NO. Since a certain degree of adhesion is recognized even if only 3 and 4 are degreased, it is presumed that there is also an influence of the Cu component, which suppresses high-temperature oxidation, and NO. From FIG. 5, it was estimated that the Cu component was excessive at 0.5%.

Next, the plating bath No. 1 shown in FIG. 4 was used to investigate the difference in adhesion depending on the thermal spraying condition using a test piece that had been subjected to hot dip galvanizing treatment with a film thickness of 45 to 55 μm.
The conditions are shown in the table of FIG.
In order to evaluate the adhesion of the sprayed coating by gas flame spraying, arc spraying, and plasma spraying after lightly blasting after hot dip galvanization, spraying on-site within a specified number of days after blasting Is assumed.
Therefore, for the purpose of promoting outdoor exposure, purified water was sprayed on a blasted plated plate by spraying and was left outdoors for 24 hours, and was sprayed immediately after blasting.
The results are shown in the table of FIG.
It was revealed that the adhesion of purified water sprayed and allowed to stand outdoors for 24 hours may decrease.

Next, the treatment conditions before thermal spraying were investigated so that adhesion could be secured even after thermal spraying after outdoor exposure.
The processing conditions and the evaluation results of adhesion are shown in the table of FIG.
In the table, “plated plate specification” indicates the preparation conditions of the test piece before thermal spraying.
Plating bath no. 3 is No. 3 shown in the table of FIG. No. 3 plating bath was used, and this bath was added together with the addition of 0.15% by mass of the Bi component and evaluated.
Similarly, plating bath no. 4 is the plating bath No. in the table of FIG. 4 was used, and a comparative evaluation was made with this bath to which 0.2 mass% of the Bi component was added.
In the table, “with and without water cooling” was a comparative investigation of those that were water cooled after hot dip galvanizing and those that caused burns on the plating surface by air cooling.
In the table, “sandblasting + white rust prevention treatment” indicates that the surface of the plating was subjected to sandblasting by air injection and then immersed in a tannic acid aqueous solution having a concentration of about 0.1 to 1% to perform organic conversion coating treatment.
Therefore, in the table, “as it is” means that neither the sand blasting treatment nor the white rust prevention treatment is performed, and “sand blasting” means only the sand blasting treatment.
All of these test pieces were sprayed with purified water, and allowed to stand outdoors for 24 hours, followed by gas flame spraying using a sprayed material of Al-5% Mg alloy.
Considering the results of evaluation of adhesion shown in FIG. 9, water spraying without rust prevention treatment after hot dip galvanization, and adhesion is reduced if left outdoors for 24 hours. It became clear that the primary rust prevention treatment was good.
In addition, when sandblasting + white rust prevention treatment (primary rust prevention treatment), it was also clarified that the influence of the burn on the plating surface is reduced.
In addition, when Bi component is added, the influence on adhesion is small at Bi: 0.15%, but the adhesion of the sprayed coating is slightly lowered at Bi: 0.2%.

Next, the influence of the white rust prevention treatment (primary rust prevention treatment) on the adhesion of the sprayed film was investigated.
The conditions and evaluation results are shown in the table of FIG.
In the table, the presence or absence of a plating bath and a water cooling step in the “plating specification” is the same as in the table of FIG. 7, and “E” in the “white rust prevention treatment” is 0.1 to 1.0. % Tannic acid aqueous solution, and “C” indicates a chromate-treated chromate aqueous solution.
In the table of FIG. 9, each test piece is lightly air-blasted (average surface roughness Ra: 5 to 30 μm) using White Alundum # 24 (Sansho Abrasive Co., Ltd.) as the blasting material, and then Gas flame spraying of Al-5% Mg sprayed material was performed on the tannic acid treatment or chromate treatment and left outdoors for 24 hours after spraying with purified water.
As a result, it is clear that if the galvanizing treatment is lightly blasted after hot dip galvanization and the primary rust prevention treatment is performed with a chemical conversion coating, the adhesion of the sprayed film is excellent even after 24 hours exposure. Even if Bi: 0.15% is added to the plating bath, there is no problem in adhesion if the Pb component in the bath is 0.008% or less, the Cd component is 0.002% or less, and the Sn component is 0.002% or less. Became clear.

Now that the conditions for ensuring the adhesion of the thermal spray coating have been clarified, the effect of the outdoor exposure period was confirmed.
The conditions and evaluation results are shown in the table of FIG.
In the table, the outdoor exposure period indicates the number of days left outdoors after sprinkling of purified water, and other conditions are the same as those shown in the table of FIG.
As a result, no decrease in adhesion was observed even when left outdoors for 14 days after watering.
In addition, if the adhesive force is 3 MPa or more, there is no problem in practical use.

Since the treatment conditions after hot dip galvanization became clear by the previous tests and evaluation studies, the influence of the low melting point component in the hot dip galvanized film was re-investigated.
The chemical components in the plating film subjected to the investigation are shown in the table of FIG.
Each sample was left outdoors for 24 hours after hot-dip galvanizing, water cooling, sandblasting, primary rust prevention treatment (organic chemical conversion coating) with an aqueous tannic acid solution, and watering of purified water.
As a result, as shown in (b), the adhesion force measurement result corresponding to the sample number of (a) is controlled not only when the low melting point component is kept low and the Bi component is controlled to be 0.15% or less. When the component was suppressed to a level of 0.001%, the adhesion of the sprayed film did not decrease even when 0.15% of any other Pb, Cd, or Sn was added, so Pb, Cd, Sn It was confirmed that the adhesiveness of the sprayed film could be secured if the plating film had a total of Bi components suppressed to about 0.16% by mass or less.

10 Girder 11 Flange 12 Web 13 Web splicing plate 14 Flange splicing plate

Claims (3)

Each having a bolt hole, butting a pair of steel materials coated with a thermal spray film on the surface, the pair of steel materials butted together, are bolted and joined via an attachment plate coated with a thermal spray film on the surface,
The bolt has a total of Pb, Cd, Sn and Bi components of 0. A hot dip galvanized film is formed using a plating bath of 16% by mass or less , Cu component of 0.20% by mass or less, Al component of 0.005% by mass or less and the balance of Zn and inevitable impurities ,
Structure of long rust junction, characterized in that are coated with a sprayed coating on the bolt after tightening bonded using the bolt. The structure is formed by joining a plurality of members composed of a web and a flange,
The web is a steel girder that is bolted and joined via a web attachment plate, and the flange is a bolt that is bolted and joined via a flange attachment plate,
The web, flange, web bears against plate and the flange bears against plate structure for long-term anticorrosive joint according to claim 1, wherein the Oh isosamples coated with a sprayed coating on the surface. 3. The structure for long-term rust-proof bonding according to claim 1, wherein the bolt is subjected to a primary rust-proofing treatment after the hot-dip galvanized film is formed.