JPH0334412B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The disclosed technology belongs to the technical field of manufacturing double pipes such as corrosion-resistant pipes and wear-resistant pipes used for piping.

<Summary of the gist> Therefore, the invention of this application is to form a base tube by laminating each unit tube such as a stainless steel inner tube on a carbon steel outer tube, either before or after the relative layering of the inner and outer tubes. The outer tube is heated to increase its diameter, the inner tube is cooled and reduced in diameter, and in this state a mechanical expansion action is applied to the inner tube to plastically deform it, and the outer tube is integrated with the outer tube. This invention relates to a method of manufacturing a self-consolidating double pipe, in which the outer pipe is elastically deformed, the two pipes are integrated, the diameter is increased, the outer pipe is cooled and the diameter is reduced, and the two pipes are tightly connected. When expanding the inner tube, a mandrel, which is inserted into the inside of the inner tube and comes into contact with it and has a tapered part in the axial direction, is moved in the axial direction to rotate the elastic ring, and the outer periphery of the elastic ring is rotated. The inner pipe is expanded by using the elastic ring, and furthermore, when the elastic ring is moved to expand the inner pipe, the cooling liquid is caused to flow from the unexpanded part of the inner pipe to the expanded part. This invention relates to a method for manufacturing heavy pipes.

<Prior Art> As is well known, piping is widely used in various industries, and is widely used for fluid transportation, information transmission, and as building structural members and frame members of equipment.

Therefore, durability is important for piping to maintain its functionality even when it is just installed, and corrosion and abrasion resistance are often required. To date, no technology has actually been developed that satisfies all of these conditions. tubes are widely used.

In this case, it is strongly desired that the outer pipe and the inner pipe be integrated and closely joined in order to integrate the raw pipes. Heavy pipes, etc. have been used.

<Problems to be Solved by the Invention> When manufacturing the former clad steel double pipe, the joint surface between the outer pipe and the inner pipe must be finished with precision machining. In addition to the disadvantage that the processing steps at the previous stage are complicated, there is also the disadvantage of high costs.

On the other hand, the latter method of manufacturing self-tightening double-pipe tubes involves shrink-fitting and hydraulic expansion methods; the former has the disadvantage that temperature control is extremely complicated, and the latter makes it difficult to obtain sufficient fitting allowance. There was a problem.

To deal with this, the applicant developed a
The so-called thermal tube expansion method, as shown in the inventions of No.-46451 and JP-A No. 57-152328, has been researched and developed, and has been put into practical use, resulting in excellent double-walled pipes with a large fitting margin. I've gotten used to being able to do it.

However, when manufacturing double-walled pipes using the thermal expansion method, there were disadvantages such as the need for a large amount of high-pressure pipe expansion fluid, and the need for accurate sealing at both ends of the inner pipe. .

It also follows that in order to impart an axial compressive residual stress to the double tube obtained, shrinkage of the end of the inner tube must be allowed, and the above-mentioned high-pressure seal is more precisely required for this purpose. This also had the disadvantage that the equipment was complicated and could be expensive.

<Purpose of the invention> The purpose of the invention of this application is to solve the problems of manufacturing double pipes based on the above-mentioned prior art, and while making full use of the advantages of the heat expansion method developed by the applicant, It is an excellent product that does not require hydraulic pressure for pipe expansion, does not require any strict cooling fluid sealing, and provides sufficient fitting allowance for the inner and outer pipes, benefiting piping technology applications in various industries. The present invention aims to provide a method for manufacturing double pipes.

<Means/effects for solving the problem> In order to solve the above-mentioned problem, the structure of the invention of this application, which is summarized in the above-mentioned claims, includes an outer tube whose diameter is increased by heating in advance. An inner tube whose diameter has been reduced by pre-cooling is layered relative to each other with the distance between the two as small as possible to form a blank tube, and one end of the inner tube of the blank tube is made of hard rubber. An elastic ring with a liquid sealed inside is brought into contact with the inner surface of the inner tube, a mandrel having an axially tapered portion is inserted into the inner tube, and the mandrel is moved to be pulled out in the axial direction. The ring is caused to rotate inside the inner tube through friction with the mandrel, and the inner tube is forcibly expanded mechanically and plastically deformed, becoming integrated with the outer tube, and the outer tube is elastically deformed. Furthermore, during that time, the coolant is allowed to flow from the unexpanded portion at the front of the inner tube to the expanded portion at the rear via the ring-shaped groove of the elastic ring, and This method takes technical measures to obtain a self-sealing double tube by cooling the tube to reduce its diameter and tightly connecting the outer tube and inner tube of the blank tube through a large fitting margin.

<Example> Next, an example of the invention of this application will be described below with reference to the drawings.

The illustrated embodiment is a method of manufacturing a corrosion-resistant double pipe, and in the embodiment shown in Figs. Also, inner tubes 2 made of stainless steel and also serving as unit tubes having a long set length are layered relatively to each other to form a blank tube 3.

In this case, the diameter of the outer tube 1 is increased by heating, and the diameter of the inner tube 2 is decreased by cooling, so that the distance between the two is kept as small as possible, and the outer tube 1 is heated to increase its diameter. It is possible to make the fitting allowance in the process sufficiently large.

As shown in FIG. 2, the raw tube 3 thus obtained is set inside a high-frequency induction heating device 4, for example, and cooling water 6 is supplied to the tip side of the inner tube 2 through a simple sealing device 5. Cooling water 6 is supplied from a tank 7 to the inside of the inner tube 2 through a passage 10 via a pump 8 and a valve 9.

An elastic ring 11 made of hard rubber having a circular cross section as shown in FIG. Rod-shaped mandrel 1
2 into the inside of the mandrel 1.
2 and the inner tube 2 so that the elastic ring 11 comes into contact with both the inner tube 2 and the inner tube 2.

In this case, in the initial posture of the mandrel 12, its axial large diameter portion and small diameter portion are connected by a tapered portion, and the elastic ring 11 is sheathed on the small diameter tapered portion.

When the mandrel 12 is moved in the axial direction in such a set state, the elastic ring, which rotates due to the friction between the mandrel 12 and the elastic ring 11, relatively overcomes the tapered part of the mandrel 12 and moves from the mandrel 12. advances at a low speed, is forcibly increased in diameter, contacts the inner surface of the inner tube 2, is forcibly expanded and deformed plastically, and the inner tube 2 is integrated with the outer tube 1 and is in a heated state. The outer tube 1 is also expanded and deformed elastically.

By maintaining this state over time, the elastic ring 11 is moved by the axial movement of the mandrel 12.
rolls and moves from one end side of the inner tube 2 to the other end side,
As described above, the inner tube 2 is plastically deformed and expanded, and the outer tube 1 is elastically deformed and expanded integrally.

And the mandrel 12 and the elastic ring 1
1 is taken out from the other end of the inner tube 2 after expansion, and the cooling water is discharged from the inner tube 2. The induction heating device 4 is stopped to finish heating, and the outer tube 2 is allowed to cool naturally. The inner tube 2 is then compressed, and due to the difference in elastic return, it is tightly connected to the plastically deformed inner tube 2 with a large fitting margin.

In this case, when viewed from the inner tube 2 side, in advance and
Since the tube is cooled by the cooling water inside it during the tube expansion process, the diameter increases due to natural temperature rise and heating due to the drainage of the cooling water after the tube expansion. A large fitting allowance can be obtained by the cooling contraction tube of No. 1.

In this embodiment, the elastic ring 11 may be a hard rubber ring with a filled cross section and whose interior is not sealed with liquid.

Next, in the embodiment shown in FIGS. 4 to 6, fifth and sixth
As shown in the figure, an elastic ring 1 in which ring-shaped notches 14, 14... are formed at predetermined equal intervals in the circumferential direction.
A ring-shaped high frequency guide is set in contact with the same mandrel 12 as described above in 1' and the inner surface of the inner tube 2, corresponds to the elastic ring 11' on the outside, and moves at a speed matching the axial movement speed of the elastic ring 11'. In this embodiment, a cooling water shower device 13 that moves at the same speed as the heating device 4' is set to perform the tube expansion action in the same manner as in the above embodiment. The cooling water of elastic ring 1
1' through the notches 14, 14...
The cooling water from the cooling water shower device 13 outside the outer pipe 1 flows through the expanded portion at the rear of the axial movement of the base pipe 3, and also before and after the expansion of the inner pipe 2 of the base pipe 3. At the same time, the elastic ring 11' was removed from the inner tube 2 by providing a strong cooling effect to improve the diameter increase due to temperature rise in the subsequent process and to obtain a large fitting allowance. Then, after passing through the heating device 4' and the cooling device 13, the fitting margin between the outer tube 1, which is naturally cooled, and the inner tube 2, which is naturally heated, is increased, resulting in a stronger self-contained double tube. It is made possible to do so.

It goes without saying that the embodiments of the invention of this application are not limited to the above-mentioned embodiments; for example,
In the elastic ring 11'' as shown in FIGS. 7 and 8,
Even if the circumferential length of the elastic ring 11'' can be increased, a spiral sub-ring made of piano wire 15 is wound around the elastic ring 11'' so that its partial cross section does not expand and the tube expansion action is inhibited. Various aspects can be adopted.

Further, the invention of this application can be applied to double pipes other than corrosion-resistant double pipes and wear-resistant double pipes.

<Effects of the Invention> As described above, according to the invention of this application, basically an outer tube having pressure resistance, heat resistance, etc. and an inner tube having corrosion resistance, wear resistance, etc. can be connected with sufficient fitting allowance. Not only does it have the effect of being able to tighten, but unlike manufacturing methods such as hydraulic pipe expansion, it does not require high-pressure pipe expansion fluid, so the power cost is low, and strict sealing against high-pressure pipe expansion fluid is not required. This not only simplifies the manufacturing process, but also simplifies the manufacturing equipment and reduces costs. In addition, the manufacturing process can be completed in a short time.

In addition, since strict sealing at both ends of the inner tube is not required, shrinkage at both ends of the inner tube is sufficiently tolerated, and therefore, no tensile residual stress is formed in the double tube after manufacturing, and it can be easily maintained during operation. The effect is that no stress corrosion cracking occurs.

In addition, by rolling the elastic ring in the axial direction of the tube using the mandrel, the inner tube can be expanded with respect to the outer tube, and the outer tube can be expanded at the same time. The effect is that tube expansion can be performed in the area of .

Further, by simply replacing the elastic rings with different sizes, double pipes of various sizes can be manufactured, and the excellent effect of providing flexibility in design is achieved.

In addition, in the process of expanding tubes using elastic rings, the cooling state of the inner tube can be maintained before and after expansion due to the flow of the tube expansion liquid from the unexpanded area to the expanded area. The cooling of the outer tube and the heating of the inner tube due to the natural temperature of the double-walled tube appear more significantly, resulting in an excellent effect in that a large fitting margin can be obtained.

[Brief explanation of drawings]

The drawings are explanatory diagrams of embodiments of the invention of this application, and FIG. 1 is a partially cutaway perspective view of a raw pipe of one embodiment;
Fig. 2 is a longitudinal cross-sectional view of the same tube expansion process, Fig. 3 is a partially cut perspective view of the elastic ring used in Fig. 2, and Fig. 4 is a longitudinal cross-sectional view of the same tube expansion process.
The figure is a longitudinal sectional view of another embodiment equivalent to Figure 2, Figure 5 is a perspective view of the elastic ring used in Figure 4, Figure 6 is a partial sectional view of Figure 5, and Figure 7 is equivalent to Figure 5. A perspective view of another embodiment, and FIG. 8 is a sectional view thereof. 1...outer tube, 2...inner tube, 3...base tube, 12...
...Mandrel, 11, 11', 11''...Elastic ring.

Claims (1)

[Scope of Claims] 1. The diameter of the outer tube of a raw tube in which the outer tube and the inner tube are layered relative to each other is increased by heating, and then the inner tube is forcibly expanded to form an integrated state of the inner and outer tubes, and the diameter is increased, and the outer tube is cooled. In a double pipe manufacturing method in which both pipes are tightly connected, an elastic ring is inscribed in the inner pipe in a cooled state, a mandrel is inserted through the elastic ring along the pipe axis direction, and the inner pipe is expanded using the mandrel. A method for manufacturing a double-walled pipe, characterized in that the rolling of an elastic ring is performed by axial movement of a double-walled pipe. 2. The diameter of the outer tube of the raw tube in which the outer tube and the inner tube are layered relative to each other is increased by heating, then the inner tube is forcibly expanded to make the inner and outer tubes integrated, the diameter is increased, and after the outer tube is cooled, both tubes are tied together. In the double tube manufacturing method, an elastic ring is inscribed in the inner tube in a cooled state, a mandrel is inserted into the elastic ring along the axial direction, and the inner tube is expanded by the elastic force generated by the axial movement of the mandrel. 1. A method for manufacturing a double-walled tube, which is carried out by rolling a ring, and the cooling liquid is passed from a pre-expansion section of the inner tube to a post-expansion section via the elastic ring.