JPH05200432A - Double pipe manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a specified strength over the entire length of the insertion part of an inserted material and to improve the yield by performing hot necking working of the end parts of inner and outer tubes respectively, then, inserting the inner tube into the outer tube through an insertion and drawing the inner and outer tubes with their necked parts combined. CONSTITUTION:The inner tube 20 and the outer tube 10 are separately subjected to hot necking working. Then, after the tape-like insert material 30 is wound on the inner tube 20, the inner tube 20 is inserted into the outer tube 10. Then, after the necked part 11 of the outer tube 10 and the necked part 21 of the inner tube 20 are welded, the necked part 11 of the outer tube 10 is clamped by a chuck 41 to extract a plug. After it is drawn, the inner and outer tubes are welded by diffusion heattreatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a double pipe in which an outer pipe and an inner pipe are diffusion-bonded through an insert material.

[0002]

2. Description of the Related Art A double pipe made of carbon steel for the outer pipe and a corrosion resistant metal such as a high Ni alloy for the inner pipe and diffusion-bonded by a low melting point insert material has already been used as an inexpensive high corrosion resistant metal pipe for oil wells. It has been put to practical use in pipes and line pipes. In the production of such a double pipe, it is necessary to sufficiently deaerate the space between the outer pipe and the inner pipe, in which the insert material is interposed, before the diffusion heat treatment. Is disclosed in JP-A-62-38783. Regarding the insert material, it can be said that it is convenient in terms of experience and efficiency that the thin tape is spirally wound around the outer peripheral surface of the inner tube. In that case, a relatively large gap is required between the inner pipe and the outer pipe, but withdrawing is also convenient in that the gap can be easily eliminated.

[0003]

However, at the time of drawing out, it is necessary to perform a mouth-drawing process for chucking the pipe end portion, and this process has conventionally been performed after the inner and outer pipes are assembled. Except when the pipe size is particularly small, the drawing process is performed hot.Therefore, the heating during the drawing process causes the surface to be joined to oxidize or the insert material partially melts. There was a problem of flowing downward. As a result, a bonding failure occurs near the narrowed portion, and a reduction in yield due to the cut-off of the defective bonding portion cannot be avoided.

To solve this problem, as disclosed in, for example, Japanese Unexamined Patent Publication No. 64-27716, it is an effective solution to perform a mouth-drawing process only on the outer pipe before the inner and outer pipes are assembled. Become. However, this method is premised on empty drawing without using a plug, and if the outer diameter reduction ratio is increased by emptying, the advance of the inner tube is blocked and only the outer tube is withdrawn, making it impossible to withdraw itself. , Reduction is limited. Further, even if both the inner and outer pipes are drawn, if the reduction is increased by emptying, the inner pipe will buckle in the circumferential direction, causing a fatal joining failure. Therefore, in the case of emptying, deaeration failure due to restriction of reduction becomes a problem.

In general, when the insert material is a tape, the overlapping is inevitable, so that a relatively large reduction is required, and the pulling out of the plug as disclosed in JP-A-62-38783 is recommended. . However, when the plug is pulled out from the outer pipe before assembling the inner and outer pipes only, the plug prevents the inner pipe from advancing, and only the outer pipe is pulled out, so that the pulling out itself becomes impossible.

The present invention has been made in view of the above circumstances, and is a double-layer structure that does not reduce the joint strength in the vicinity of the mouth-drawing portion even though hot-drawing is performed and can secure sufficient reduction. An object is to provide a tube manufacturing method.

[0007]

According to the method for producing a double pipe of the present invention, the outer pipe end is hot-narrowed while the inner pipe end is inserted into the mouth-narrowed portion. Part is hot-squeezed, and then the outer tube and inner tube are assembled with an insert material, and the outer-tube mouth-throttled part and the inner-tube mouth-throttled part inserted into the inner tube are connected, and then withdrawn. Is performed, and then diffusion heat treatment is performed.

[0008]

Since the mouth restriction is performed before the inner and outer pipes are assembled, there is no risk that the insert material will be melted by heating during the mouth restriction. The surfaces to be bonded that have been oxidized by heating can be cleaned before assembly. Since the mouth-throttled portions are provided on both the inner pipe and the outer pipe, and the both are united and combined for withdrawing, the separation of the inner and outer pipes does not occur even when the plug is withdrawn.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

The outer pipe 10 is made of, for example, carbon steel, and the inner pipe 20 is made of a highly corrosion-resistant metal such as a high Ni alloy. Outer tube 10
The inner diameter of the inner tube 20 is 5 m larger than the outer diameter of the inner tube 20 in order to prevent movement of the insert material 30 spirally wound around the outer surface of the inner tube 20.
Increase by about m.

At the time of drawing, the outer pipe 10 and the inner pipe 20 are first subjected to hot drawing. The mouth-throttled portion 11 of the outer tube 10 has a regular size according to the drawing equipment. With respect to the mouth throttle portion 21 of the inner pipe 20, when the inner pipe 20 is inserted into the outer pipe 10, the mouth throttle portion 21 of the inner pipe 20 is fitted into the mouth throttle portion 11 of the outer pipe 10, and The dimensions are adjusted so that the tip of the mouth throttle 21 slightly protrudes from the tip of the mouth throttle 11. Outer tube 1 by heating at the time of mouth restriction
When the inner surface of 0 and the outer surface of the inner tube 20 are oxidized, the oxide and the like are mechanically and chemically removed.

When the mouth-drawing process is completed, a tape-shaped insert material 30 is formed on the outer peripheral surface of the inner tube 20 excluding the mouth-drawing portion 21.
Are spirally wound with a predetermined overlap. Then, the inner pipe 20 is inserted into the outer pipe 10 to assemble the inner and outer pipes. As a result, the mouthpiece 21 is fitted in the mouthpiece 11, and the tip of the mouthpiece 21 projects from the tip of the mouthpiece 11. Then, the tip of the mouth-drawing portion 11 is welded to the protruding portion. This welding is performed continuously or intermittently in the circumferential direction, but in any case, since the heating is limited to the tips of the apertured parts 11 and 21, the heat adversely affects the insert material 30 and the wound part thereof. There is no such thing.

When the inner and outer tubes are assembled, the inner tube of the outer tube 10 is pressed against the outer tube of the inner tube 20 through the insert material 30 by pulling the plug. In the plug drawing, the mouth-neck portion 11 of the outer tube 10 is sandwiched by the chuck 41, and the outer tube 10 is passed through the die 42.
Since the mouthpiece 21 of the inner pipe 20 is welded to the inner pipe 1, the inner pipe 20 passes through the die 42 together with the outer pipe 10 even though the inner pipe 20 is restrained by the plug 43 from the inner surface side. Therefore, sufficient reduction is applied without separating the inner and outer tubes, and the inner and outer tubes are sufficiently degassed.

After the drawing, the inner and outer tubes are joined by diffusion heat treatment.

A double tube was actually manufactured by such a method. Table 1 shows the material dimensions of the inner and outer pipes and the insert material. The joint strength of the product pipe after removing the narrowed part is measured by JI
In addition to the investigation by S G0601, the defects of the joint were investigated by an ultrasonic test. For comparison, the same investigation was performed when the mouth drawing was performed after the inner and outer tubes were assembled and when the mouth drawing was performed only on the outer tube. The results of the investigation are shown in Table 2 together with the dimensions of the product pipe and Rd. Table 2
Rd in the figure indicates reduction, which is calculated by Equation 1.

[0016]

[Equation 1]

[0017]

[Table 1]

[0018]

[Table 2]

In the example of the present invention, sufficient joint strength was obtained over the entire length of the product pipe, and no joint defect was observed.
However, when the mouth drawing process is performed after assembly, the joint strength is significantly reduced at the top end where the mouth drawing portion was located during plug drawing, and many defects are observed. It buckled and could not be pulled out. When only the outer tube is drawn, the joint strength is low over the entire length of the product tube when the reduction is small (Rd = 6.6%), and the reduction is large (Rd = 9.9%).
Moreover, the inner tube was left unplugged by pulling the plug.

[0020]

As described above, according to the method for producing a double pipe of the present invention, since the predetermined strength can be obtained over the entire length of the insert material insertion portion, there is no cutoff of the defective joint portion,
The manufacturing yield can be increased. Sufficient reduction can be given by pulling the plug, and the overall joint strength can be increased.

[Brief description of drawings]

FIG. 1 is a schematic view showing one embodiment of the method of the present invention.

[Explanation of symbols]

 10 Outer Pipe 11 Port Drawing Part 20 Inner Tube 21 Port Drawing Part 30 Insert Material 41 Chuck 42 Die 43 Plug

Claims (1)

[Claims] 1. An outer tube end is hot-narrowed, while an inner tube end is hot-narrowed so that the inner tube end is inserted into the mouth-narrowed part. Assemble the outer tube and the inner tube through the, and pull out in a state in which the outer tube mouth narrowing section and the inner tube mouth narrowing section inserted therein are connected,
A method for producing a double tube, characterized by performing a diffusion heat treatment after that.