JPH02187280A - Manufacture of metallic duplex tube - Google Patents

Abstract

PURPOSE:To uniformly join an inner and outer pipes at high strength by inserting the inner pipe spirally winding an insert material in inner circumferential face into the outer pipe to make a duplex raw pipe and extruding this while heating at just below m.p. of the insert material at inlet side of a die. CONSTITUTION:The strip-state insert material 2 is wound as spiral-state at the prescribed overlapping on the inner circumferential face of the inner pipe 1. This inner pipe 1 is inserted into the outer pipe 3 to make the duplex raw pipe. The duplex raw pipe is extruded with the die 5 while heating at just below m.p. of the insert material 2 by using high frequency heating coil 8 at the inlet side of the die 5. As the insert material 2, for example an amophous foil having about 50mum thickness is used. By this method, the duplex pipe can be manufactured at extremely simple.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a metal double pipe, and particularly to a method for manufacturing a double metal pipe in which an outer pipe and an inner pipe are metallurgically joined with an insert material. Regarding the manufacturing method.

(Prior art) Oil country tubular goods used in oil fields are required to have high corrosion resistance because they are used in a corrosive atmosphere. Materials with excellent corrosion resistance include stainless steel and Examples include nickel-based high-alloy steels, and especially post-strike nickel-based high-alloy steels exhibit excellent corrosion resistance even in sour corrosive environments.However, these steels contain chromium and nickel in many needles. Therefore, it is expensive, and it is economically very important to reduce its content.

By the way, when comparing the inner and outer surfaces of a pipe from the perspective of corrosion resistance, in most cases it is the inner surface of the pipe that requires high corrosion resistance, as seen in line pipes where highly corrosive petroleum flows through the inner surface. There are few cases where high corrosion resistance is required on the outer surface of the pipe. Therefore, even if the entire tube is made of high-alloy steel, the corrosion resistance will not improve, and it is more economical to replace only the inner surface of the tube with high-alloy steel to increase the corrosion resistance. For these reasons, the introduction of metal double pipes in which an outer pipe and an inner pipe are metallurgically joined is progressing, and the outer pipe is made of relatively thick carbon steel pipes and inner pipes to maintain mechanical strength. The tubes are often thin-walled tubes made of corrosion-resistant high-alloy steel.

The manufacturing method for a metal double pipe in which an outer pipe and an inner pipe are metallurgically joined is as follows: After fitting the inner pipe and the outer pipe to form a double pipe,7 the inner pipe and the inner pipe are combined. A common method is to hot pressure weld the outer tube to the mother tube. Hot extrusion and hot roll rolling are often used for hot welding, but since these process double tubes at high temperatures, oxidation of the joint interface becomes a problem and requires large-scale equipment. Become. A method developed against this background is a method for manufacturing metal double pipes that utilizes diffusion bonding using insert materials.

The conventional method for manufacturing double tubes using insert material involves evacuation between the inner and outer tubes, heating both the inner and outer tubes, and using the stress generated by the difference in thermal expansion between the two tubes, the two tubes are bonded to the insert material. A method of diffusion bonding via
-159284.

Furthermore, JP-A-62-72423 discloses a method in which an inner tube is inserted into an outer tube through an insert material, and hot rolling or hot extrusion is carried out at a temperature higher than the melting point of the insert material. No. 62-38783 discloses a method in which an insert material interposed between an inner tube and an outer tube is brought into close contact with each other by cold drawing, and then both tubes are heated to a temperature higher than the melting point of the insert material to perform diffusion bonding. A method is disclosed.

[Problem to be solved by the invention]

In the case of the method disclosed in JP-A-59-159284, since the pressure caused by the difference in thermal expansion is only applied to the bonding surfaces, bonding failures are likely to occur due to insufficient pressure. In addition, the smoothness of the joint surface is important for this purpose.
Basically, joining is performed in one step, but in practice, cold drawing and mechanical grinding must be performed to ensure smoothness, and joining requires two or more steps.

The method disclosed in JP-A No. 62-72423 uses hot rolling and hot extrusion in combination, so there is not only little point in using insert materials, but also because the in-sheet material is heated to a temperature higher than the melting point. The melt of the material flows down, which tends to cause joint defects in the circumferential direction of the pipe.

In the method disclosed in Japanese Patent Application Laid-Open No. 62-38783,
Considering efficiency, workability, etc., it is industrially necessary to wind a ribbon-shaped insert material in a spiral shape around the outer circumferential surface of the inner tube with a predetermined overlap. Cold drawing alone cannot bring the insert material 2 into uniform contact with the inner circumferential surfaces of the inner tube and the outer tube 3 at the overlapping portions, resulting in microscopic gaps. As a result, even if heated to a temperature above the melting point, this gap cannot be completely filled with the melt of the insert material, and areas with low joint strength periodically form in the tube axis direction due to the winding pinch of the insert material. The result appears. Furthermore, the melt of the insert material flows in the circumferential direction, and the problem of poor bonding in the tube circumferential direction still remains, and bonding requires two steps: drawing and heating.

The present invention solves all of these problems and makes it possible to efficiently manufacture highly reliable metal double pipes that are uniform in both the circumferential direction and the axial direction of the pipe and have high joint strength with a small number of man-hours. The purpose is to provide a method.

[Means to solve the problem]

In the manufacturing method of the present invention, an inner tube in which a ribbon-shaped insert 1 is spirally wound with a predetermined overlap on the inner circumferential surface is inserted into an outer tube to form a double element tube. This is a method for manufacturing a metal double pipe in which the pipe is drawn by a die while being heated to just below the melting point of the insert material mentioned above on the entrance side of the die.

(Function) In the manufacturing method of the present invention, drawing is performed while the insert material is heated, so the insert material is plastically deformed during the drawing process, and even in the overlapped portion, the inner circumferential surface of the outer tube and the outer circumference of the inner tube are The insert material adheres to the surface.Moreover,
Since the heating temperature of the inner material is limited to just below the melting point, there is no flow of the inner material, and eventually the insert material melts and diffuses due to the processing increase due to drawing, and the outer tube and inner tube are separated. are joined in one step.

[Example〕 Embodiments of the present invention will be described below with reference to FIG.

In the manufacturing method of the present invention, first, a ribbon-shaped insert material 2 is wound spirally around the surface of an inner tube 1 made of alloy steel. At this time, the adjacent insert members 2 are arranged such that their both sides overlap with each other by a predetermined width so that the outer circumferential surface of the inner tube 1 is not exposed.

For the insert material 2, for example, an amorphous foil strip with a thickness of about 50 μm is used. A typical amorphous foil strip is N 1llAt Cr +s, s, St, , B1
．． S (melting point 1180°C), N ImAL pH
(melting point 980'C), etc. The width of the insert material 2 may be appropriately selected in consideration of workability and the like when wrapping the insert material 2 around the outer circumferential surface of the inner tube l.

When the insert material 2 is wound around the outer peripheral surface of the inner tube 1, it is inserted into the outer tube 3 made of ordinary steel to form a double blank tube.

In the double blank pipe, the gap between the inner pipe 1 and the outer pipe 3 should be made as narrow as possible within a range that does not interfere with the insertion of the inner pipe 1, so as to improve the degree of processing in subsequent drawing. Usually, the number of cormorants is limited to about 1 to 5 cormorants.

When the double blank pipe is assembled, a mouth constriction part 4 is formed at one end thereof, and then the double blank pipe is set on the entry side of the die 5.

Then, insert the plug 7 supported at the tip of the core bar 6 into the inner tube 1 of the double tube from the die 5 side, set it at the proper position in the die 5, and then insert the double tube into the die 5. While being heated by the high-frequency heating coil 8 on the person's side, the die 5 is pulled out to the exit side using the grip 9.

The temperature at which the double tube is heated by the high-frequency heating coil 8 is just below the melting point of the insert material 2. This is insert material 2
If the insert material 2 is heated to the melting point of the insert material 2, it will flow down and its thickness in the circumferential direction will become uneven.If the heating temperature is extremely low compared to the melting point of the insert material 2,
It becomes difficult to plastically deform the insert material 2 during drawing, and even if the processing temperature rise associated with drawing is applied, the insert material 2
does not reach its melting point. From this point of view, the heating temperature is usually lower than the melting point of the insert material 2 (
(melting point -50°C).

The double tube that is drawn out from inside the die 5 is particularly important for its outer tube 3.
is reduced in diameter, and the outer circumferential surface of the inner tube 1 and the inner circumferential surface of the outer tube 3 are pressed against the insert material 2. Since the insert material 2 is heated to just below its melting point until this crimping, there is no flow down, and it is plastically deformed during the crimping stage, and there is no gap near the overlapping part, so that the insert material 2 is heated just below its melting point. and the inner circumferential surface of the outer tube 3. Finally, only the surface layer of the insert material 2 melts due to the processing temperature increase, and the outer circumferential surface of the inner tube 1 and the inner circumferential surface of the outer tube are melted and diffusion bonded.

In addition, in order to prevent the joint surface from oxidizing, an inert gas supply cap is attached to the rear end of the double tube, and the inner tube 1
Ar gas may be supplied between the outer tube 3 and the outer tube 3.

The results of actually manufacturing a double pipe using the manufacturing method of the present invention described above will be described next.

Material is 5US304, outer diameter 20 mm, inner diameter 15 mm, meat *
2.5 length, 6000mm long, on the outer circumferential surface of inner pipe 1, thickness 5mm
Low melting point amorphous brazing filler metal (F
A thin strip of e-Cr-3L-13 series (melting point: 1180°C) was made into a spiral shape with an average overlap of 21nl as the insert material 2, and then the material was 310C'r, the outer diameter was 28 + nm, and the inner diameter was 22 marks. , meat 1 yen 311111,
It was inserted into the outer tube 3 having a length of G O00nun. After that,
t, 11The assembled double blank tube is heated to 1140°C by the high-frequency heating coil 8 on the inlet side of the die 5jJl! It was drawn at a speed of 50 m/s while heating.

The dimensions of the metal double pipe finally obtained by bending and stretching are an outer diameter of 25
++++++++, inner diameter 15mm, flesh *5M, length 6000
It is worth it.

When this double pipe was examined by ultrasonic flaw detection, it was found that it was firmly diffusion bonded over the entire length, and no defective bonding was observed in the tube circumferential direction. On the other hand, if the same double tube is cold-drawn with the same specifications as above and then heated to a temperature above the melting point of the insert material (250°C), the entire length will be temporarily joined. , parts with low joint strength appeared in the longitudinal direction of the tube, corresponding to the winding pinch of the insert material.

〔Effect of the invention〕

Since the manufacturing method of the present invention first uses drawing, there is no need to place importance on the smoothness of the inner tube surface, and pretreatment of the material such as mechanical grinding can be omitted or simplified.

Further, since the insert material is wound in a spiral shape, this operation is easy, and furthermore, subsequent drawing and heating are performed in the same process. Therefore, the double pipe can be easily manufactured.

Second, the insert material is wrapped with overlap, which ensures that the insert material is interposed throughout the entire space between the inner tube and the outer tube, and the heating of the insert material causes the insert material to deform in the overlapped portion, thereby closing the gap. Does not occur. Further, by limiting the heating temperature to just below the melting point of the insert material, the insert material does not flow down. Finally, processing elevation is added to this heating to melt and diffuse the insert material. As a result, the inner tube and the outer tube are joined evenly and with high strength in both the tube circumferential direction and the tube axial direction.

4. Brief Description of the Drawings FIG. 1 is a sectional view schematically showing the method for manufacturing a double pipe according to the present invention, and FIG. 2 is a schematic diagram showing a state in which an insert material is wound around the outer circumferential surface of the inner pipe.

In the figure, l: inner tube, 2: insert material, 3: outer tube, 4: mouth drawing part, 5 dice, 6: core metal, 7: plug, 8: high frequency heating coil.

Claims (1)

[Claims] 1. Insert the inner tube, which has thin strip-shaped insert material spirally wound around the inner circumferential surface with a predetermined overlap, into the outer tube to make a double tube, and insert the double tube at the entrance side of the die. A method for manufacturing a metal double pipe, comprising drawing with the die while heating the insert material to just below its melting point.