JP2000129474A - Method for buffering hydrogen absorbing embrittlement of titanium clad steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the excessive convertion of the electric potential of titanium clad steel into the baser one, to buffer the hydrogen absorbing embrittlement therein and to maintain its durability by providing titanium clad steel joined to a steel structure in which the submerged part is subjected to electric corrosion prevention with a metallic material having a natural electric potential baser than that of the steel and joining it with the steel. SOLUTION: The submerged part 2 in seawater of the steel pipe pile 1 of a landing bridge 7 is, e.g. fitted with a voltaic anode 3, which is subjected to electric corrosion prevention. Moreover, titanium clad steel 5 having high corrosion resistance is coiled directly below a droplet zone and a tide zone 4 severe in corrosive environments in the steel pipe pile 1, and its corrosion resistance is moreover increased. In this steel structure, from the tide seawater face of the titanium clad steel 5 to below about 1 m, a metallic material 8 with a planar, helical or netty shape or the like of copper, a copper alloy, stainless steel, cupro, a nickel base alloy or the like having a natural electric potential baser than that of the steel is coiled, and, moreover, this metallic material 8 is welded and joined to the steel pipe pile 1. In this way, protective current is flowed on the metallic material, and it is made hard to flow on the titanium clad steel to prevent hydrogen absorption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel structure provided with a cathodic protection in a submerged part, for example, a pier or a harbor steel structure provided with a cathodic protection in brackish water or seawater. The present invention relates to a method for buffering hydrogen absorption embrittlement of titanium clad steel joined from a draft portion to an atmospheric portion of a marine steel structure composed of a large floating body typified by an outer surface of a steel material or a marine airport in a tidal zone.

[0002]

2. Description of the Related Art In steel pipe piles, piers, floating bodies, and other marine steel structures generally used for harbor steel structures, submerged portions are typically subjected to electrolytic protection, painting, or a combination thereof. On the other hand, although the non-metallic coating and painting are applied to the splash zone and the tidal zone immediately below (HWL + 1m to LWL-1m) or the draft part, the corrosion environment is severer than other parts and the progress of corrosion is large. For this reason, it has recently been practiced to coat with a highly corrosion-resistant metal such as a stainless steel plate or titanium to further enhance the corrosion resistance.

For example, as shown in FIG. 9, a submerged portion 2 of a steel pipe pile 1 of a pier 7 is provided with a galvanic anode 3 used in a galvanic anode system of the cathodic protection method by welding or the like. Attached to the steel pipe pile 1 so as to be electrically conductive, a titanium clad steel 5 is joined to the splash zone and the tidal zone 4 all around. Alternatively, as shown in FIG. 10, a hardly soluble electrode 20 used in the external power supply method of the cathodic protection method is attached to the submerged portion 2 of the steel pipe pile 1 of the pier 7 so as to be electrically insulated from the steel pipe pile 1. At the same time, the hardly soluble electrode 20 is connected to the plus side of the DC power supply 21 via an electric wire 22, and the steel pipe pile 1 is connected to the minus side of the DC power supply 21 via the electric wire 22. The titanium clad steel 5 is joined all around.

[0004]

However, the galvanic anode 3 attached to the submerged part 2 of the steel pipe pile 1 as shown in FIG. 9 or the submerged part 2 of the steel pipe pile 1 as shown in FIG. Since the anticorrosion current 6 from the attached poorly soluble electrode 20 also flows into the titanium clad steel 5, the steel pipe pile 1 of the submerged portion 2
(-900 to -1050 mV vs seawater silver chloride reference electrode, the same applies hereinafter), which is considerably lower than about -700 mV, which is said to start hydrogen absorption of titanium. Therefore, there is a possibility that the long-term durability of the titanium clad steel 5 cannot be maintained, which leads to a failure in securing a predetermined life as a structure.

The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress the potential of titanium clad steel from becoming excessively low, maintain durability over a long period of time, and improve the structure. It is intended to provide a hydrogen absorbing embrittlement buffering method for titanium clad steel which can ensure a predetermined life as the above.

[0006]

In order to achieve the above object, the method of the present invention provides a steel structure in which a steel material in a submerged portion is subjected to electrolytic protection and a titanium clad steel is joined to a part of the steel material. In the object, a metal material having a higher natural potential than the steel material is provided on the entire surface or a part of the titanium clad steel, and the metal material is joined to the steel material.

As the metal material, any one of copper, copper alloy, stainless steel, cupro or nickel-based alloy is used. Further, as the shape of the metal material, a plate shape, a spiral shape, or a net shape is preferable, and a band shape or a linear shape is suitable for the spiral shape, and a linear shape is suitable for the mesh shape.

[0008]

In a steel structure in which a steel material in a submerged portion is subjected to electrolytic protection and a titanium clad steel is joined to a part of the steel material, a natural potential is applied to the whole or part of the titanium clad steel from the steel material. By providing the noble metal material and joining the metal material to the steel material, the anticorrosion current flows into the metal material and returns to the negative electrode of the galvanic anode or the DC power supply device through the steel material. Therefore, it is difficult for the titanium clad steel to flow into the titanium clad steel.
It hardly goes below mV. Further, in order to make it more difficult for the anticorrosion current to flow into the titanium clad steel, the larger the natural potential difference between the metal material and the steel material, the better. That is, the electric potential of the steel which is generally subjected to electrolytic protection in submerged water is about -900 to -1050 mV, and is negatively polarized by about 400 mV from the natural potential (-500 to -600 mV). Therefore, if the potential of the metal material is about -700 mV even when the metal material is negatively polarized by about 400 mV, the possibility of hydrogen absorption embrittlement in the titanium clad steel is extremely low. For that purpose, a metal material whose natural potential is more noble than steel is advantageous, and in consideration of workability, cost, corrosion resistance, etc.,
It is preferable to join any one of copper, copper alloy, stainless steel, cupro, and nickel-based alloy.

On the other hand, considering the workability and cost, the thickness of the metal material is 0.5 to 5 mm, preferably
A 1 to 3 mm plate may be wound around the entire surface or a part of the circumference of the titanium clad steel, and this may be welded to the steel material, or a bolt may be erected on the steel material and fixed with a nut. . A spiral band having a width of about 10 to 20 mm or a linear one having a diameter of about 3 to 7 mm can be fixed by the same position and method as described above. Further, it can be appropriately selected according to the material of the above-mentioned metal material. Usually, a linear material having a diameter of about 1 to 3 mm and a mesh of about 5 to 10 mesh can be fixed by the same position and method as described above. The shape of the mesh may be a square, a rectangle, a rhombus, or the like, and the weave may be a plain weave, a twill weave, a tatami weave, or the like.

The present invention can be applied to all titanium clad steels regardless of the type of titanium. The “submerged portion” of the present invention includes not only a seawater environment but also a brackish water environment and a freshwater environment.

[0011]

1 to 8 show an embodiment of the present invention.
It will be described based on. FIG. 1 shows a steel pipe pile 1 of a pier 7 in which a submerged portion 2 is provided with a galvanic anode 3 for cathodic protection, and a titanium clad steel 5 is wound immediately below a splash zone and a tidal zone 4. A plate-like metal material 8 made of copper is wound around the entire circumference about 1 m below the sea level of the clad steel 5 at low tide, and the steel pipe pile 1 and the plate-like metal material 8 are attached by welding.

FIG. 2 shows a steel pipe pile 1 similar to FIG.
A submersible electrode 20 is attached to the submerged part 2 in place of the galvanic anode 3, and a hardly soluble electrode 20 is connected to the positive side of the direct current electrode device 21 and a steel pipe pile 1 is connected to the negative side via an electric wire 22. Instead of the plate-shaped metal material 8 made of copper, a plate-shaped metal material 9 made of stainless steel is wound around the entire surface of the titanium clad steel 5 and attached to a bolt (not shown) installed on the steel pipe pile 1 with a nut. is there.

FIG. 3 shows a steel pipe pile 1 similar to FIG.
In place of the plate-like metal material 8 made of copper, a metal material 10 in which a strip made of a copper alloy is spirally wound instead of the plate-shaped metal material 8 made of copper over the entire circumference about 1 m below the sea level at the time of low tide of the titanium clad steel 5 is wound. It is what was welded to. FIG. 4 shows FIG.
The entire surface of the titanium-clad steel 5 is made of a copper-based wire made of copper instead of a spiral-shaped metal material 10 over the entire circumference about 1 m below the sea level at low tide. A spirally wound metal material 11 is wound and welded to the steel pipe pile 1.

FIG. 5 shows an example in which a plate-like metal material 12 made of cuple is wound in place of the plate-shaped metal material 8 made of copper in FIG. 1 and attached to the steel pipe pile 1 by welding. FIG. 6 is a diagram in which a plate-shaped metal material 13 made of a nickel-based alloy is wound around the plate-shaped metal material 9 made of stainless steel in FIG. 2 and attached to the steel pipe pile 1 by welding. FIG. 7 shows a structure in which a net-like metal material 14 made of copper is wound in place of the plate-shaped metal material 8 made of copper in FIG. 1 and attached to the steel pipe pile 1 by welding.

FIG. 8 shows that a titanium clad steel 5 is joined to the entire surface of a marine steel structure 15 composed of a floating body from a draft portion 16 to an atmospheric portion 17, and a submerged portion 2 has a galvanic anode 3.
A plate-shaped metal material 18 made of a copper alloy is attached to a part of the entire circumference from a draft portion 16 to an atmospheric portion 17 and is welded to a steel material portion 19 of a structure.

In general, the steel pipe pile 1 is provided with titanium clad steel 5 immediately below the splash zone and the tidal zone 4.
The length of the submerged part is about 1 m.
The present invention can be applied even if it is as large as 5 m.

[0017]

EXAMPLE 1 A steel pipe pile having a diameter of 700 mm was subjected to an electric current test by the method shown in FIG. 1, and after one month, the potentials of the metal pipe part and the submerged part were measured. The potential of the material part is -65
0 to -710 mV, and the steel pipe pile in the submerged part is -800 to
It was -1050 mV. From this result, the steel pipe pile in the submerged part maintains the anticorrosion potential, and the metal part is almost -700.
It shows a potential nobler than mV, indicating that the possibility of hydrogen absorption embrittlement of titanium clad steel is extremely low.

Example 2 A steel pipe pile having a diameter of 700 mm was subjected to an electricity test by the method shown in FIG. 2, and after one month, the potentials of the metal pipe part and the submerged part were measured. Part potential is -68
0 to -730 mV, and the submerged steel pipe pile is -810 to
It was -1050 mV. From this result, the steel pipe pile in the submerged part maintains the anticorrosion potential, and the metal part is almost -700.
It shows a potential of around mV, which indicates that the possibility of hydrogen absorption embrittlement of titanium clad steel is extremely low.

Example 3 An electric current test was performed on a steel pipe pile having a diameter of 800 mm by a method as shown in FIG. 3, and after one month, the potentials of the metal pipe part and the submerged part were measured. The potential of the part is -66
0 to -720 mV, and the steel pipe pile in the submerged part is -800 to
It was -1050 mV. From this result, the steel pipe pile in the submerged part maintains the anticorrosion potential, and the metal part is almost -700.
It shows a potential nobler than mV, indicating that the possibility of hydrogen absorption embrittlement of titanium clad steel is extremely low.

[0020]

Since the present invention is configured as described above, it has the following effects. Suppresses the excessive lowering of the potential of titanium clad steel and buffers the hydrogen absorption embrittlement of titanium clad steel, maintaining the long-term durability of titanium clad steel and ensuring the required life as a structure it can.

[Brief description of the drawings]

FIG. 1 is a diagram with a main part plan view showing a state in which a sheet metal material made of copper according to the present invention is joined to a part of titanium clad steel of a steel pipe pile.

FIG. 2 is a diagram with a main part plan view showing a state in which a sheet metal material made of stainless steel according to the present invention is joined to the entire surface of titanium clad steel of a steel pipe pile.

FIG. 3 is a diagram with a main part plan view showing a state in which a strip-shaped spiral metal material made of a copper alloy according to the present invention is joined to a part of titanium clad steel of a steel pipe pile.

FIG. 4 is a diagram with a main part plan view showing a state where a linear spiral metal material made of copper according to the present invention is joined to the entire surface of a titanium clad steel of a steel pipe pile.

FIG. 5 is a diagram with a main part plan view showing a state where a plate-shaped metal material made of cupro according to the present invention is joined to a part of titanium clad steel of a steel pipe pile.

FIG. 6 is a diagram with a main part plan view showing a state in which a plate-shaped metal material made of a nickel-based alloy according to the present invention is joined to the entire surface of a titanium clad steel of a steel pipe pile.

FIG. 7 is a diagram with a main part plan view showing a state in which a reticulated metal material made of copper according to the present invention is joined to a part of titanium clad steel of a steel pipe pile.

FIG. 8 is a view showing a state in which a plate-like metal material made of a copper alloy according to the present invention is joined to a part of titanium clad steel of a marine steel structure made of a floating body.

FIG. 9 is a plan view of a steel pipe pile partially joined to titanium clad steel, showing a main part in a state of cathodic protection by a galvanic anode method with a cross section of a main part.

FIG. 10 is a diagram with a main part plan view showing a state of cathodic protection by a conventional external power supply method for a steel pipe pile partially joined with titanium clad steel.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steel pipe pile 2 submerged part 3 galvanic anode 4 splash zone and tidal zone 5 titanium clad steel 6 anticorrosion current 7 pier 8 plate metal material made of copper 9 plate metal material made of stainless steel 10 strip made of copper alloy Spiral metal material 11 Linear spiral metal material made of copper 12 Plate metal material made of cupro 13 Plate metal material made of nickel-based alloy 14 Net metal material made of copper 15 Marine steel structure made of floating body 16 Draft Part 17 Atmospheric part 18 Plate metal material made of copper alloy 19 Steel part 20 Refractory electrode 21 DC power supply 22 Electric wire

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) E02D 31/06 E02D 31/06 D (72) Inventor Sakae Fujita 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Yasushi Tanaka, Inventor 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Toshio Takano 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside Steel Pipe Co., Ltd. (72) Inventor Takeshi Karasawa 1-21-12 Minami Kamata, Ota-ku, Tokyo Japan Inside Corrosion Protection Industry Co., Ltd. (72) Inventor Kenji Kono 1-12-112 Minami Kamata, Ota-ku, Tokyo Japan Corrosion Protection Within Industrial Co., Ltd. (72) Inventor Guan Hanayama 1-21-12 Minami Kamata, Ota-ku, Tokyo Japan F Corrosion Protection Industrial Co., Ltd. F-term (reference) 4E001 AA03 BB01 CC03 4E081 YQ02 4K 060 AA02 AA03 AA10 BA19 BA47 EA01 EB01 EB06 FA03

Claims (3)

[Claims] 1. In a steel structure in which a steel material in a submerged portion is subjected to electrolytic corrosion protection and a titanium clad steel is joined to a part of the steel material, the steel material is applied to the entire surface or a part of the titanium clad steel. A method of buffering hydrogen absorption embrittlement of titanium clad steel, comprising providing a metal material having a noble natural potential and bonding the metal material to the steel material. 2. The method according to claim 1, wherein the metal material is made of any one of copper, copper alloy, stainless steel, cupro, and nickel-based alloy. 3. The method according to claim 1, wherein the metal material has a plate shape, a spiral shape, or a net shape.