JP2002153911A - Metallic double pipe and method of manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallic pipe where finger prints left on the surface of the external pipe are inconspicuous at a low cost in the metallic pipe which is used without coating the surface. SOLUTION: This pipe is a metallic double pipe which consists of a metallic external pipe 1 and a metallic internal pipe 2, and the surface of the external pipe 1 of which has a rolled satin finished surface. The outside diameter of the external pipe 1 is <=100 mm, the thickness of the external pipe is <=1 mm and the average roughness of the surface of the external pipe is >=0.5 μm by Ra. The external pipe 1 and the internal pipe 2 are in close contact, and the external pipe 1 and the internal pipe 2 have a parallel weld zone (3, 4) respectively in the longitudinal direction of the pipe. Because the external pipe is made by bending a thin metallic sheet after forming the rolled satin finished surface on it, the finger prints left on the surface are inconspicuous. By adopting the rolled satin finished surface, the pipe is manufactured at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal tube used without painting the surface, and more particularly to a metal double tube characterized in that fingerprints on the outer tube surface are inconspicuous and a method of manufacturing the same. It is.

[0002]

2. Description of the Related Art Metal tubes used without painting the surface of the tube are:
It is used as building members, fittings, fall prevention fences and intrusion prevention fences installed on both sides of the road, and fences installed around buildings. A metal tube made of stainless steel, titanium or a titanium alloy is excellent in corrosion resistance, and can maintain the beautiful appearance of the surface even when the surface of the tube is unpainted.

[0003] When the surface of the metal tube is unpainted, there is a problem that when a person touches the surface of the tube by hand, fingerprints appear on the surface of the tube. Fat adheres to the surface of the tube in accordance with the unevenness of the fingerprint of the finger, which makes the fingerprint more visible in appearance. Furthermore, if the fingerprint is attached and left for a while, it may not be possible to completely erase the fingerprint even if the tube is subsequently washed or wiped off.

If the surface of the metal tube is dulled by projecting grit onto the surface of the metal tube at a high speed to obtain a matte texture, the attached fingerprints become inconspicuous and can be at a level that does not pose a practical problem. However, dulling the metal tube is not advantageous because the production cost increases.
When a metal plate is cold-rolled using a roll having undergone dulling, a rolled satin surface can be formed on the surface of the metal plate. However, the conventional rolled satin surface cannot have a sufficient surface to make fingerprints attached to the surface inconspicuous.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive metal tube which is used without painting its surface and whose fingerprint on the outer tube surface is inconspicuous.

[0006]

That is, the gist of the present invention is as follows. (1) A metal double tube comprising a metal outer tube 1 and an inner tube 2, wherein the surface of the outer tube 1 is a rolled satin surface. (2) The metal double pipe according to the above (1), wherein the outer diameter of the outer pipe 1 is 100 mm or less, and the thickness of the outer pipe 1 is 1 mm or less. (3) The metal double tube according to the above (1) or (2), wherein the average roughness of the outer tube surface is 0.5 μm or more in Ra. (4) The outer pipe 1 and the inner pipe 2 are in close contact with each other, and the outer pipe 1 and the inner pipe 2 are each welded portions (3, 4) parallel to the longitudinal direction of the pipe.
The metal double tube according to any one of the above (1) to (3), comprising: (5) The metal double tube according to any one of (1) to (4), wherein the outer tube 1 is made of stainless steel or titanium or a titanium alloy, and the inner tube 2 is made of steel or stainless steel. . (6) The metal band 5 serving as the outer tube 1 is cold-rolled using a roll which has been subjected to a dulling process to make the surface of the metal band 5 a rolled satin surface, and the metal band 6 serving as the inner tube 2 is formed into a cylinder. Then, the inner tube is formed by welding the joint portion, and then the metal band 5 serving as the outer tube is formed into a cylindrical shape along the outer shape of the inner tube 2 with the rolled satin skin side as the outer surface. (1) to (5), wherein the outer tube is formed by welding the portions.
The method for producing a metal double tube according to any one of the above. (7) The outer tube 1 is made of titanium or a titanium alloy. After the inner tube is formed, the inner tube is cooled, and then a metal band is formed into a cylindrical shape along the outer shape of the inner tube, and the joint is formed. The method for producing a metal double pipe according to the above (6), wherein the outer pipe is formed by welding.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventionally, a dulling process is performed on a rolling roll to form a dulled satin surface on the rolling roll surface.
Cold rolling of a metal plate using this rolling roll forms a rolled satin surface on the surface of the metal plate. However, in the case of a metal plate whose surface is made into a rolled satin surface by this method, it was not possible to obtain a surface sufficient to make fingerprints attached to the surface inconspicuous. Further, even if a metal tube is manufactured using this metal plate, it is not enough to make fingerprints attached to the surface inconspicuous.

The present inventors cold roll a metal plate using a rolling roll having a matte surface by dulling, and form a rolled matte surface on the surface using a thin metal plate. Then, it was found that when this metal plate was bent to form a metal tube, fingerprints attached to the surface of the metal tube became inconspicuous. When the thickness of the metal plate is large, it is rolled with a roll having a dulled satin surface, and further processed into a metal tube to form a rolled satin surface sufficient to make fingerprints inconspicuous. Can not do. On the other hand, when the thickness of the metal plate is thin, rolling is performed using a rolling roll having a dulled satin surface, and when the metal plate is further processed into a metal tube, fingerprints adhered to the surface of the metal tube stand out. Can be eliminated. This is considered to be because the metal plate had a small thickness, so that a good rolled satin surface was formed on the metal plate when the metal plate was rolled with a roll having a dulled satin surface. Further, it is presumed that, by bending a metal plate having a rolled satin surface to form a steel pipe, the light incident on the surface of the steel pipe is reflected on a curved surface, so that the attached fingerprint is not noticeable.

Metal pipes used for building members, fittings, fences, fences, etc., have a predetermined thickness as a metal plate to be processed into a metal pipe in order to secure strength required for each application. There is a need. Therefore, even if a rolled satin surface can be formed on a thin metal plate to make fingerprints inconspicuous, a metal tube having the necessary strength can be formed simply by bending this metal plate to form a metal tube. I can't. In the present invention, as shown in FIG. 1 (a), the metal pipe is a metal double pipe composed of an outer pipe 1 and an inner pipe 2, and the outer pipe 1
This problem was solved by using a thin metal plate having a rolled satin surface. Since it is a metal double tube, the inner tube can be used as a member for maintaining the strength required for the metal tube. Therefore, a thin metal plate having a thickness sufficient to make fingerprints inconspicuous can be used for the outer tube.

The metal plate used as the outer tube 1 of the metal double tube has a thickness of 1 mm or less and an outer diameter of the outer tube 1 of 100 mm.
By performing the bending process as described below, it is possible to obtain a rolled satin texture sufficient to make fingerprints inconspicuous. The thickness of the metal plate is more preferably 0.4 mm or less.

In the present invention, fingerprints can be made inconspicuous if the average roughness of the outer tube surface having a rolled satin surface is 0.5 μm or more in Ra. The average roughness of the outer tube surface is more preferably 1 μm or more in Ra.

Since the metal double tube of the present invention is used without painting and is often used outdoors, the outer tube of the metal double tube has a corrosion-resistant metal such as stainless steel, titanium or titanium. It is preferable to use a titanium alloy. These metals are also preferable metals for forming a rolled satin surface. Further, in the present invention, the metal plate constituting the outer tube has a small thickness, so that even when an expensive metal such as titanium or a titanium alloy is used, the production cost of the metal tube of the product can be reduced. Titanium or titanium alloys have very good corrosion resistance and are therefore the most suitable metals for use in harsh environments where corrosion is a problem even for stainless steel.

As the inner tube 2 of the metal double tube of the present invention, it is preferable to use steel or stainless steel. Even in a metal tube used outdoors, a portion in contact with the outside air can be dealt with by the corrosion resistance of the outer tube, so that inexpensive steel can be used for the inner tube. In particular, when using in a severe environment, when corrosion resistance of the inner surface of the inner tube is required, stainless steel may be used as the inner tube.

When the inner tube 2 is made of steel or stainless steel having a thickness of 2 mm or more, a stable outer tube can be formed if the thickness of the outer tube 1 is 1 mm or less. In the present invention, the thickness of the outer tube 1 is set to 1 mm or less for the purpose of making the outer tube surface have an effective rolled satin surface, so that the above condition is satisfied. It is preferable that the outer tube 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 will occur in the outer tube due to flaws during pipe making or handling defects generated when handling the double tube, which is the corrosion resistance of the double tube. Is significantly reduced.

The method for manufacturing a metal double tube according to the present invention and the metal double tube manufactured by the method will be described. First, formation of the rolled satin surface on the metal plate constituting the outer tube will be described. Regarding a roll for cold rolling for forming a rolled satin surface, dulling is performed on the roll surface to make the roll surface a satin surface. Dulling of the rolling roll is performed by projecting grit onto the roll surface at high speed.

Next, a method of manufacturing a metal double tube using a metal plate having a rolled satin surface will be described. Manufacture the inner tube and the outer tube separately in advance, then attach the inner tube to the inside of the outer tube, then perform cold working to improve adhesion, and perform heat treatment if necessary and There is known a method in which a diffusion layer is formed at a contact portion with an outer tube to integrate the inner tube and the outer tube. In a metal double pipe, it is essential that the inner pipe and the outer pipe are in close contact with each other. In the above-described method of manufacturing the inner pipe and the outer pipe separately and then mounting both, the outer pipe and the inner pipe are required. It is necessary to perform cold working in order to obtain adhesion to the tube. However, in this method, the number of steps for performing the cold working increases, and 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 above (4) and (5) of the present invention, as shown in FIG. 2, the metal strip 6 is formed into a cylindrical shape, and the joint thereof is welded to form the inner pipe 2, and then the inner pipe 2 is formed. The outer tube 1 and the inner tube 2 come into close contact with each other by forming the metal band 5 having a rolled satin surface along the outer shape of 2 into a cylindrical shape and welding the joint thereof to form the outer tube 1. The outer tube 1 and the inner tube 2 each form a metal double tube having welds (3, 4) parallel to the longitudinal direction of the 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 common method of 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.
A method of forming a metal strip 5 having a rolled satin surface on the surface thereof into a cylindrical shape with the rolled satin skin side outside along the outer shape of the outer tube 1 and welding the joint portion thereof at the outer tube welding portion 14. Since the inner pipe 2 is used as a mold for forming the outer pipe, the inner pipe 2 and the outer pipe 1 are formed in close contact with each other, and the inner pipe is welded to the joint of the outer pipe 1 as a result. A metal double tube in which the outer tube 2 and the outer tube 1 are in close contact 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.
As shown in (b), the outer pipe 1 and the inner pipe 2 each have welds (3, 4) parallel to the longitudinal direction of the pipe. 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 metal structure of the base metal means a metal structure of a portion excluding the 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.

In the above manufacturing method, the manufacturing of the inner pipe and the manufacturing of the outer pipe are continuously performed on the same manufacturing line. Compared to a method of manufacturing an inner tube, cutting it to an appropriate length, and then coating the outer tube on the surface of the inner tube, it is possible to manufacture a metal double tube at a lower cost.

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. When using titanium or a titanium alloy for the outer tube, it is most preferable to use TIG welding for the 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.

When the outer tube 1 is made of titanium or a titanium alloy and the inner tube 2 is made of steel or stainless steel, consideration must be given to TIG welding of the outer tube joint. When the metal of the inner pipe 2 adjacent to the outer pipe is melted at the time of welding the outer pipe joint, and a component such as Fe constituting the inner pipe metal is mixed into the weld 3, the weld 3
Becomes brittle and poor welding occurs. In the present invention,
After forming the inner tube 2, the inner tube is cooled in the cooling zone 12, and then the metal (titanium or titanium alloy) band 5 is formed into a cylindrical shape along the outer shape of the inner tube 2 in the outer tube forming portion 13. By forming the inner pipe by welding the joint portion at the outer pipe welding portion 14, the outer pipe 1 can be welded without the metal forming the inner pipe 2 being melted. 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 becomes the unavoidable impurity concentration level or lower.

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.

For a conventional metal tube having a matte texture,
While the surface of the metal tube is dulled to give a matte surface, the present invention differs in that the metal tube surface is made of a rolled matte surface. Rolled pear-skinned pipes have an inconspicuously fine weld bead.
Such a weld bead does not remain on the dulled pear surface and is different in this respect, so that both can be distinguished.

[0027]

EXAMPLE A metal double tube of the present invention was manufactured using titanium for the outer tube and stainless steel for the inner tube. The outer diameter of the pipe is 42.7m
m, the thickness of titanium of the outer tube is 0.3 mm, and the material of stainless steel of the inner tube is SUS304 and the thickness is 2.0 mm.

A rolled satin surface was formed on the surface of the titanium plate constituting the outer tube by cold rolling. The average roughness of the rolled pear surface was 2.1 μm in Ra.

As shown in FIG. 2, a metal strip 6 of stainless steel is formed into a cylindrical shape, and its joint is welded to form the inner tube 2. Then, the surface is rolled along the outer shape of the inner tube 2. Titanium metal strip 5 as a background is formed into a cylindrical shape, and its joint is T
The outer tube 1 was formed by IG welding. The outer tube 1 and the inner tube 2 are in close contact, and the outer tube 1 and the inner tube 2 each form a metal double tube having welds (3, 4) parallel to the longitudinal direction of the tube.

This double metal tube was used as a road crossing prevention fence. The cross-prevention fence had a pitch of 3 m between the columns and a four-step beam. When the fingerprint was applied by touching the metal double tube of the cross-prevention fence with the hand, it was not possible to recognize the adherence of the fingerprint by visual observation, and good results were obtained.

[0031]

In the present invention, the metal tube used without painting is a metal double tube, and the surface of the outer tube is a rolled satin surface. Since the outer tube of the metal double tube can be thinned, a rolled satin surface is formed on a thin metal plate, and the metal plate is bent to form an outer tube of the metal double tube. According to the present invention, the fingerprint attached to the surface of the metal tube can be made inconspicuous despite the rolled satin surface. Since the matte surface is formed by rolling, the metal tube can be manufactured at a lower cost than a conventional metal tube having a dulled matte surface.

When an expensive metal having corrosion resistance is used on the surface of the metal tube, only the outer tube having a small thickness is used as the expensive metal and an inexpensive metal can be used for the inner tube. It is possible to manufacture a metal tube having the same at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing a metal double pipe of the present invention, in which (a) is a cross-sectional view and (b) is a perspective view having a welded portion.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer pipe 2 Inner pipe 3, 4 Welded part 5, 6 Metal strip 8 Welded part 10 Inner pipe formation part 11 Inner pipe welded part 12 Cooling zone 13 Outer pipe formation part 14 Outer pipe welded part 15 Bead cutting part

 ──────────────────────────────────────────────────続 き Continued 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, Otemachi, Chiyoda-ku, Tokyo 3 Inside Nippon Steel Corporation (72) Inventor Akihiko Kusano 1-9-9 Yaesu, Chuo-ku, Tokyo Inside Kyushu Fire Brick Co., Ltd. Inside the corporation

Claims (7)

[Claims] 1. A metal double tube comprising a metal outer tube and an inner tube, wherein the outer tube has a rolled satin surface. 2. The outer tube has an outer diameter of 100 mm or less, and the outer tube has a thickness of 1 mm or less.
2. The metal double tube according to item 1. 3. The average roughness of the outer tube surface is 0.5 μm in Ra.
The metal double pipe according to claim 1 or 2, wherein: 4. An outer pipe and an inner pipe are closely contacted with each other, and the outer pipe and the inner pipe each have a welded portion parallel to a longitudinal direction of the pipe. A double metal tube as described. 5. The metal double pipe according to claim 1, wherein the outer pipe is made of stainless steel, titanium, or a titanium alloy, and the inner pipe is made of steel or stainless steel. 6. A metal band serving as an outer tube is cold-rolled using a roll which has been subjected to a dulling process so that the surface of the metal band has a rolled satin surface, and a metal band serving as an inner tube is formed into a cylindrical shape. Then, the seam portion is welded to form an inner tube, and then the metal band serving as the outer tube is formed along the outer shape of the inner tube into a cylindrical shape with the rolled satin skin side as the outer surface, and the seam portion 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. 7. The outer tube is made of titanium or a titanium alloy, and after the inner tube is formed, the inner tube is cooled, and then a metal band is formed into a cylindrical shape along the outer shape of the inner tube, and the seam portion is formed. 7. The method according to claim 6, wherein the outer tube is formed by welding.