JP2001269712A - Metallic clad tube and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive clad tube and its manufacturing method in a metallic clad tube, the external tube and internal tube of which are composed of different kinds of metals and its manufacturing method. SOLUTION: In the clad tube consisting of the external tube 1 and internal tube 2 of which are composed of different kinds of metals and brought into close contact, the external tube 1 consists of titanium or titanium alloy, the external tube 1 and the internal tube 2 respectively have weld zones 3 and 4 parallel to the longitudinal direction of the tubes and the metallographic structure of respective base material parts of the external tube 1 and internal tube 2 is as-rolled or annealed structure. By this method for manufacturing the metallic clad tube, the internal tube 2 is formed by forming a metallic strip 6 into a cylindrical shape and welding its joint part and, next, the external tube 1 is formed by forming a metallic strip 5 into a cylindrical shape along the external size of the internal tube 2 and welding its joint part. After forming the internal tube 2, the internal tube 2 is cooled and, next, the external tube 1 is formed by forming the metallic strip 5 into a cylindrical shape along the external size of the internal tube 2 and welding its joint part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal double pipe in which an outer pipe and an inner pipe made of dissimilar metals are in close contact with each other, and a method of manufacturing the same. The present invention relates to a metal double pipe having excellent surface corrosion resistance in which the inner pipe is made of metal for maintaining strength.

[0002]

2. Description of the Related Art Metal pipes are often used as components of fall prevention fences and intrusion prevention fences installed on both sides of a road, fences installed around a building, and the like. Since these fences and fences are installed outdoors, they are required to have corrosion resistance.

An inexpensive iron pipe is used as a metal pipe, and its surface is coated with anticorrosion paint. If corrosion resistance is to be emphasized, the surface of the iron pipe is galvanized, and the surface is coated thereon. However, when installed in a corrosive environment near the coast, zinc is plated with a thick coating, but the amount of zinc plating is limited due to the problem of plating adhesion, and the life of the members is limited. There is a problem that it is lowered by corrosion.

In the case where a stainless steel tube is used as a metal tube, since stainless steel is more expensive than ordinary carbon steel, the use of a stainless steel tube increases the cost. There is. Also, in an easily corrosive environment near the coast, even pitting of stainless steel causes rust on the surface, deteriorating the aesthetic appearance, and requiring maintenance costs to maintain the aesthetic appearance, completely solving the problem. Does not reach.

[0005] A metal double tube is formed by an outer tube and an inner tube made of dissimilar metals, a metal having good corrosion resistance such as titanium or stainless steel is used for the outer tube, and the inner tube has sufficient tube strength. There is known a method of using a double pipe using a metal such as iron for this purpose, and using the double pipe as a member requiring corrosion resistance.

[0006] The inner pipe and the outer pipe are separately manufactured in advance,
After that, the inner tube is mounted inside the outer tube, then cold worked to improve the adhesion, and further heat treatment is performed as necessary to form a diffusion layer at the contact portion between the inner tube and the outer tube. A method for integrating an inner tube and an outer tube is known. In a double pipe, it is essential that the inner pipe and the outer pipe are in close contact with each other. In the above-mentioned method of manufacturing the inner pipe and the outer pipe separately and then mounting both, the outer pipe and the inner pipe are required. Cold working is carried out in order to obtain the adhesion between them. JP 6
In the method described in Japanese Patent Application Laid-Open No. 3-219555, cold drawing is performed as the cold working, and then a diffusion layer is formed and adhered. In the method described in JP-A-63-165028, after inserting an outer tube into an inner tube and superimposing them, the inner tube and the outer tube are tightly closed by heating to a high temperature and simultaneously pressurizing and expanding the inner tube. It is stuck to. JP-A-2-12
In the method described in Japanese Patent No. 1784, cold rolling, degreasing and washing, heating, cold working, solution treatment, and cold drawing are performed to form a double clad tube.

[0007] A method of manufacturing a clad metal in which two kinds of metals are bonded in advance and manufacturing the clad metal to form a double pipe can be considered. However, when titanium is used for one material of the double pipe and another metal (iron-based metal or copper) is used for the other material, Fe or Cu is mixed into a welded portion between titanium in welding at the time of pipe making. As a result, there is a problem that a sound welded pipe cannot be manufactured because the welded portion is embrittled. In the method described in JP-A-53-53020, a composite member is prepared by polymerizing and fixing a foreign metal material, for example, a titanium material as a surface plate on both sides of a strip-shaped core material. A method is described in which a string-shaped end member made of a metal material of the same quality as the surface plate is fixed to both end surfaces to be joined, and the end member is welded to form a composite pipe.

[0008]

In a method of manufacturing an inner pipe and an outer pipe separately and mounting them to perform cold working such as diameter reduction or expansion, the number of steps for performing cold working increases. However, there is a problem that the manufacturing cost increases. Of course, if the inner tube and the outer tube are manufactured separately and only the two tubes are mounted, the inner tube and the outer tube do not come into close contact with each other, and it is difficult to use the inner tube and the outer tube as a double tube.

In the method described in the above-mentioned Japanese Patent Application Laid-Open No. 53-53020, the manufacturing process is complicated and the manufacturing cost is increased, and the end face material of the welded portion is the same material as the surface material. Since it is a material for obtaining corrosion resistance, such as titanium, the welded portion is made of only a corrosion-resistant material, not a core material.

An object of the present invention is to solve the above problems and to provide an inexpensive double tube and a method for manufacturing the same.

[0011]

That is, the gist of the present invention is as follows. (1) In a metal double tube in which an outer tube 1 and an inner tube 2 made of different kinds of metals are in close contact with each other, the outer tube 1 is made of titanium or a titanium alloy, and the outer tube 1 and the inner tube 2 Metal double pipes having welded portions (3, 4) parallel to the longitudinal direction of the pipes, and the metal structures of the base metal portions of the outer pipe 1 and the inner pipe 2 being as-rolled or annealed. . (2) The metal double pipe according to the above (1), wherein the metal structure of the welded portions (3, 4) is a structure that has not been subjected to working deformation since the time of welding. (3) The welded portion (3, 4) between the outer pipe 1 and the inner pipe 2 is located at substantially the same position in the circumferential direction of the double pipe, as described in the above (1) or (2). Metal double tube. (4) The thickness of the outer tube 1 is 50% of the thickness of the inner tube 2
The metal double tube according to any one of the above (1) to (3), wherein: (5) The inner pipe 2 is made of iron, an iron alloy or stainless steel, and the Fe concentration in the welded portion composition of the outer pipe 1 is an unavoidable impurity concentration. A metal double tube according to Crab. (6) A cover 7 is placed on the pipe end of the metal double pipe according to any one of the above (1) to (5), and the cover 7 can be welded to a metal constituting the outer pipe 1. Made of metal and cover 7
A metal double pipe formed by welding a contact portion between the metal pipe and the outer pipe 1. (7) The metal band 6 is formed into a cylindrical shape, and its joint is welded to form the inner tube 2. Next, the metal band 5 is formed into a cylindrical shape along the outer shape of the inner tube 2, and the joint is welded. The method for producing a metal double tube according to any one of the above (1) to (5), wherein the outer tube 1 is formed by performing the following steps. (8) After the inner tube 2 is formed, the inner tube 2 is cooled, and then the metal band 5 is formed into a cylindrical shape along the outer shape of the inner tube 2 and the joint is welded to form the outer tube 1. (7) The method for producing a metal double tube according to the above (7). (9) The method according to (7) or (8), wherein the welding speed of the outer pipe joint is 8 m / min or less.

In the present invention, the metal strip 6 is formed into a cylindrical shape, and its joint is welded to form the inner pipe 2. Then, the inner pipe 2 is made of a dissimilar metal along the outer shape of the inner pipe 2. By forming a metal band (titanium band) 5 made of titanium or a titanium alloy into a cylindrical shape and welding the joint thereof to form the outer tube 1, the outer tube 1 and the inner tube 2 made of dissimilar metals are formed. The outer tube 1 and the inner tube 2 are in close contact with each other and have welds (3, 4) parallel to the longitudinal direction of the tube, respectively. It is characterized by forming a metal double tube.

In manufacturing the inner pipe 2, the metal strip 6 is formed into a cylindrical shape at the inner pipe forming portion 10 and the joint portion is welded at the inner pipe welding portion 11, which is the most general method for manufacturing a welded pipe. Since the method of forming the inner tube is adopted, the inner tube can be manufactured inexpensively and in large quantities. The outer pipe 1 is formed in the outer pipe forming section 13 following the inner pipe manufacturing.
The outer tube 1 is formed by forming a titanium strip 5 of a metal different from the inner tube 2 into a cylindrical shape along the outer shape of the inner tube 2 and welding the joint at the outer tube welding portion 14. Inner tube 2
As a result, the inner tube 2 and the outer tube 1 are formed in close contact with each other, and as a result of welding the joint portion of the outer tube 1, the inner tube 2 and the outer tube 1 come into close contact. A metallic double tube is formed. As described above, the outer pipe production is also the application of the most common method of producing a welded pipe. Since the production of the inner pipe and the production of the outer pipe (double pipe) can be performed simultaneously in the same continuous production process, The metal double tube can be manufactured at very low cost.

Since the metal double tube of the present invention is manufactured as described above, the outer tube 1 and the inner tube 2 are in close contact with each other, and the outer tube 1 and the inner tube 2 are each parallel to the longitudinal direction of the tube. Welding parts (3,
4). As the metal band used for pipe forming, an as-rolled or annealed metal band is used. Since cold working is not performed after the formation of the double pipe, the metal structure of the base metal portion of each of the outer pipe 1 and the inner pipe 2 is characterized by being as rolled or annealed. When cold working is performed after forming a double pipe as in the prior art, a cold drawing structure is formed on the outer surface of the outer pipe in the case of diameter reduction processing, and the inner drawing of the inner pipe is performed in the case of expanding processing. Since a cold drawn structure is also formed on the surface, the metal structure of the outer tube or the inner tube base material is no longer a rolled or annealed structure in any case. The base metal structure is
It means the metal structure of the part excluding the weld heat affected zone.
Further, since the metal double pipe of the present invention does not perform cold working after pipe forming, the metal structure of the welded portion of each of the outer tube and the inner tube is a structure that has not undergone work deformation since the time of welding. And Further, since the annealing heat treatment is not performed after the pipe making, the metal structure of the welded portion of each of the outer pipe and the inner pipe has a feature that it has not undergone any alteration due to the heat treatment after the welding.

[0015]

FIG. 1 is a sectional view of a metal double tube according to the present invention.
FIG. 2 shows a conceptual diagram of the method for manufacturing a metal double tube of the present invention in FIG.
Shown in

In the present invention, the metal band 6 is formed into a cylindrical shape at the inner tube forming portion 10 and the joint portion is welded at the inner tube welding portion 11 to form the inner tube 2. The titanium strip 5 of a metal different from that of the inner tube 2 is continuously formed in the outer tube forming portion 13 along the outer shape of the inner tube 2 without cutting the outer tube forming portion 13 into a cylindrical shape. At the outer tube welding portion 14 to form the outer tube 1. If the inner pipe is cut after the inner pipe is formed, and then the outer pipe is formed, the supply of the inner pipe at the time of manufacturing the outer pipe becomes discontinuous, so that it is possible to perform high-productivity sufficiently low-cost manufacturing. become unable.

In the production of ordinary welded pipes, the seam is located above the cylinder after the metal band is formed into a cylinder in the production process. Therefore, in the metal double pipe of the present invention, the welded portion 4 of the inner tube 2 is also replaced by the welded portion 3 of the outer tube 1.
Both are located above the cylinder in the manufacturing process,
The welded portion between the outer tube 1 and the inner tube 2 is located at substantially the same position in the circumferential direction of the double tube. Here, the substantially same position refers to the position shown in FIG.
In (b), the angle θ between the outer pipe weld 3 and the inner pipe weld 4 in the circumferential direction is within a range of 30 ° with each other. In a double-pipe pipe making apparatus, when the welding position of the outer pipe and the welding position of the inner pipe are tilted to the maximum in the opposite direction, the angle θ can be expanded to a range within 60 °. .

In the present invention, since the outer tube is formed along the outer shape of the inner tube after the inner tube is manufactured, the inner tube has sufficient rigidity at the time of forming the outer tube, and has a rigidity within the range of rigidity of the inner tube. It is necessary for the outer tube to be formed at. For this purpose, it is preferable that the inner tube 2 has a large thickness and the outer tube 1 has a small thickness. In the present invention, by setting the thickness of the outer tube 1 to 50% or less of the thickness of the inner tube 2, the inner tube can have a sufficient rigidity at the time of forming the outer tube and function as a mold. . In the use of the present invention, the inner tube 2 is a strength holding member and requires a predetermined thickness, and the outer tube 1 is a member for maintaining corrosion resistance and may be thin. Particularly, since an expensive titanium material is used for the outer tube 1, the thickness of the outer tube 1 is designed to be thin in the first place. Therefore, as described above, setting the thickness of the outer tube 1 to 50% or less of the thickness of the inner tube 2 is consistent with the requirement based on the use of the present invention.

When the inner tube 2 is made of iron, iron alloy or stainless steel having a thickness of 2 mm or more, a stable outer tube can be formed by making the thickness of the outer tube 1 1 mm or less. It is preferable that the outer tube made of titanium or a titanium alloy has a thickness of 0.1 mm or more. If the thickness of the outer tube is less than 0.1 mm, holes or cracks occur in the titanium or titanium alloy portion of the outer tube due to scratches during pipe making or handling scratches generated when handling the double tube, This is because it may significantly reduce the corrosion resistance of the double pipe.

In applications where severe corrosion resistance is required,
In the present invention, since the outer tube 1 is made of titanium or a titanium alloy, pitting corrosion that appears when stainless steel is used on the surface can also be prevented. If the inner tube 2 is made of stainless steel instead of carbon steel or the like, the effect of preventing corrosion of the inner tube can be improved.

As a method for welding the joints of the inner pipe 2 and the outer pipe 1, a method of forging and joining the joints of the base material by heating them, TI
A G welding method, a MIG welding method, a high frequency welding method, a seam welding method, a gas welding method, or the like can be employed. Since the outer tube uses titanium or a titanium alloy, it is most preferable to use TIG welding for outer tube welding from the viewpoint of the soundness of the welded portion.

[0022] After welding the inner pipe, the weld may form a bead raised from the surface of the inner pipe. By cutting this bead with a cutting means using a cutting tool or the like, it is possible to further ensure close contact with an outer tube to be formed later.

In the present invention in which the outer tube 1 is made of titanium or a titanium alloy and the inner tube 2 is made of iron, iron alloy or stainless steel, it is necessary to consider the TIG welding of the outer tube joint. When the metal of the inner pipe 2 adjacent to the outer pipe is welded at the time of welding the outer pipe joint, and components such as Fe constituting the inner pipe metal are mixed into the welded portion 3,
The weld 3 becomes brittle and poor welding occurs. In the present invention, after the inner pipe 2 is formed, the inner pipe is cooled in the cooling zone 12, and then the inner pipe 2 is formed in the outer pipe forming portion 13.
The metal (titanium or titanium alloy) band 5 is formed into a cylindrical shape along the outer shape of the above, and the seam portion thereof is welded at the outer tube welding portion 14 to form the inner tube. The outer tube 1 can be welded without melting. As a result, in the metal double pipe of the present invention, the Fe concentration in the composition of the welded portion of the outer pipe is at or below the unavoidable impurity concentration level.

In the cooling of the inner pipe 2 after the formation of the inner pipe, the inner pipe 2 is cooled down to a temperature of 700 ° C. or less, and then the outer pipe 1 is welded. Melting of the inner tube metal can be prevented. In the tube making equipment,
By providing a cooling zone 12 between the inner pipe weld 11 and the outer pipe weld 14 and forcibly cooling the inner pipe 2 in the cooling zone 12, the inner pipe temperature can be reduced to a target temperature.

In the present invention, the contact surface between the outer tube 1 and the inner tube 2 is in close contact. The degree of close contact can be such that the distance between the inner surface of the outer tube 1 and the outer surface of the inner tube 2 is 200 μm or less on average in the circumferential direction. The distance between the inner surface of the outer tube 1 and the outer surface of the inner tube 2 may be preferably 100 μm or less, more preferably 50 μm or less, in the circumferential average.

In the present invention, it is preferable that the welding speed of the outer tube weld 4 is set to 8 m / min or less. If it is 8 m / min or less, the instantaneous heat load applied to the welded portion is reduced, the melting of the inner tube metal can be prevented, and the soundness of the welded portion is improved.

FIGS. 3 and 4 show the metal double tube of the present invention.
The lid 7 can be arranged at the end of the tube as shown in FIG. The cover 7 is covered from the outside of the metal double tube, and the contact portion between the end of the cover and the outer tube 1 of the metal double tube is welded and sealed, so that the inside of the metal double tube is sealed at the end of the tube. And the outside atmosphere. When the outer tube of the metal double tube is made of titanium or a titanium alloy, the lid 7 is also made of titanium or a titanium alloy, so that T
IG welding can be performed. When the outer tube 1 is made of titanium or a titanium alloy and the lid 7 is made of an iron-based metal, when welding between the outer tube 1 and the lid 7, the two metals are mixed to form a sound weld 8. become unable.

[0028]

Embodiment No. 1 in Table 1 The metal double tube of the present invention was manufactured using the conditions shown in Nos. 1 to 14. The continuous tube forming apparatus shown in FIG. 2 was used. The material of the outer tube 1 was titanium or a titanium alloy, and the material of the inner tube 2 was stainless steel or carbon steel.

[0029]

[Table 1]

First, the continuous metal band 6 is formed in the inner tube forming portion 19.
Is formed into a cylindrical shape, and the joint is welded by high-frequency welding or TIG welding at the inner tube welding portion 11 to form the inner tube 2. Subsequently, the inner tube 2 is formed at the cooling zone 12 having a length of 5 m.
Was subjected to forced water cooling to reduce the inner tube temperature to 330 ° C., and the bead was cut in the bead cutting section 15 using a cutting tool. Thereafter, the titanium strip 5 continuous along the outer shape of the inner pipe 2 was formed into a cylindrical shape in the outer pipe forming section 13, and the outer pipe 1 was formed by TIG welding the joint at the outer pipe welding section 14. The TIG welding conditions for the outer tube are as shown in Table 1. The formed double tube was cut into a predetermined length at a cutting section (not shown).

The positional relationship between the inner pipe weld 4 and the outer pipe weld 3 was set at positions shifted from each other in the circumferential direction by the angle shown as the weld angle θ in Table 1. The average distance between the inner surface of the outer tube 1 and the outer surface of the inner tube 2 was 50 μm or less in the circumferential direction. In any of the examples, the penetration of the material of the inner tube into the welded portion 3 of the outer tube did not occur, and a good welded portion could be formed.

Example No. 1 in which carbon steel was used as the material of the inner tube.
In 11 and 12, the lid 7 as shown in FIG. 4 was installed at both ends of the cut metal double tube. Also, in a high temperature area, the lid 7 shown in FIG. 4 was similarly installed at the end of the pipe, even when stainless steel was used as the material of the inner pipe, for members to be installed on the shore within 100 m from the shore. . The material of the lid 7 was pure titanium, and the contact portion between the end of the lid 7 and the outer tube was sealed by TIG welding to form a welded portion 8 to block the inside of the double tube from the outside atmosphere. Regarding members installed in locations where the temperature is 100 m or more away from the coast even in high-temperature areas, and in low-temperature areas,
When the material of the inner tube was stainless steel, it was used without installing the lid 7.

The metal double tube was used in a fall prevention fence installed near the coast. No surface corrosion of the metal double tube occurred even after long-term use, and no pitting occurred on the surface as seen in stainless steel tubes. Also, no corrosion of the inner tube occurred. For this reason, the beautiful appearance of the fall prevention fence can be maintained for a long period of time, and it has become possible to continue using it semipermanently.

[0034]

According to the present invention, a metal band is formed into a cylindrical shape and its joint is welded to form an inner tube. Then, a metal band of a metal different from the inner tube is formed along the outer shape of the inner tube. By forming it into a cylindrical shape and welding its joints to form an outer tube,
The outer tube and the inner tube made of dissimilar metals are in close contact with each other, and the outer tube and the inner tube each have a welded portion parallel to the longitudinal direction of the tube. It is possible to form a metal double tube having an as-rolled or annealed structure.
As a result, the step of bringing the outer tube and the inner tube into close contact with each other by cold rolling as in the related art is not required, and a metal double tube can be manufactured at low cost.

As a result, by maintaining the mechanical strength by the inner tube and arranging a metal tube having excellent corrosion resistance, such as titanium, as the outer tube, even when used near the coast, no corrosion occurs and the appearance of the surface is improved. It has become possible to provide a metal double tube that can be kept for a long time at extremely low cost.

A cover is placed on the end of the metal double tube of the present invention, and the cover is made of a metal that can be welded to the metal constituting the outer tube. The metal double pipe with the welded part cuts off the inside of the double pipe and the outside atmosphere, thereby preventing corrosion of the inner pipe.

[Brief description of the drawings]

FIG. 1 is a sectional view of a metal double pipe of the present invention.

FIG. 2 is a conceptual diagram illustrating a method for manufacturing a metal double tube according to the present invention.

FIG. 3 is a partial cross-sectional view of the metal double pipe of the present invention having a lid attached to the pipe end.

FIG. 4 is a partial cross-sectional view of the metal double pipe of the present invention having a lid attached to the pipe end.

[Explanation of symbols]

 Reference Signs List 1 outer tube 2 inner tube 3, 4 welded portion 5 metal band (titanium band) 6 metal band 7 lid 8 welded portion 10 inner tube forming portion 11 inner tube welded portion 12 cooling zone 13 outer tube formed portion 14 outer tube welded portion 15 Bead cutting part

Continuing on the front page (72) Inventor Kazuhiro Kinoshita 2-6-3 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Steel Corporation (72) Inventor Shoichi Maruyama 2-6-3 Otemachi, Chiyoda-ku, Tokyo New Japan Inside Steel Works Co., Ltd. (72) Inventor Akihiko Kusano 1-9-9 Yaesu, Chuo-ku, Tokyo Kyushu Fire Brick Co., Ltd. F term (reference) 4E028 CA02 CA13 4F100 AB01B AB02B AB04B AB12A AB31A AB31B BA02 EC172 EH032 EJ502 JB02

Claims (9)

[Claims] 1. A metal double pipe in which an outer pipe and an inner pipe made of dissimilar metals are in close contact with each other, wherein the outer pipe is made of titanium or a titanium alloy, and the outer pipe and the inner pipe are each formed of a pipe. A metal double pipe having a welded portion parallel to the longitudinal direction, wherein the base metal microstructure of each of the outer pipe and the inner pipe is as-rolled or annealed. 2. The metal double pipe according to claim 1, wherein the metal structure of the welded portion is a structure that has not been subjected to working deformation since the time of welding. 3. The welded portion between the outer tube and the inner tube is located at substantially the same position in the circumferential direction of the double tube.
Or the metal double tube according to 2. 4. The thickness of the outer tube is 5 times the thickness of the inner tube.
The metal double pipe according to any one of claims 1 to 3, wherein the content is 0% or less. 5. The inner pipe is made of iron, iron alloy or stainless steel, and the Fe concentration in the welded composition of the outer pipe is an unavoidable impurity concentration.
The metal double tube according to any one of the above. 6. The metal double pipe according to any one of claims 1 to 5, wherein the pipe end is covered with a lid, and the lid is made of a metal which can be welded to a metal constituting the outer pipe. A metal double pipe constituted and welded at a contact portion between a lid and an outer pipe. 7. A metal band is formed into a cylindrical shape and its joint is welded to form an inner tube, and then the metal band is formed into a cylindrical shape along the outer shape of the inner tube and the joint is welded. The method for producing a metal double pipe according to any one of claims 1 to 5, wherein an outer pipe is formed. 8. Forming the inner tube after cooling the inner tube, forming a metal band into a cylindrical shape along the outer shape of the inner tube, and welding the joint to form an outer tube. The method for producing a metal double pipe according to claim 7, wherein 9. The method according to claim 7, wherein a welding speed of the outer pipe joint is 8 m / min or less.