JPS5978715A - Production of double pipe - Google Patents

Abstract

PURPOSE:To produce a highly self-tightening corrosion resistant double pipe with less man-hour and high efficiency by inserting an inside pipe into an outside pipe then exerting a mechanical malleating force thereon. CONSTITUTION:A stainless steel inside pipe 1 having a wall thickness T1 is inserted into a carbon steel outside pipe 2, and a roll 3 is fitted tightly as specified to a part of the pipe 1. A malleating force is exerted on the roll so that the roll rotates by itself. The pipe 1 is reduced to the wall thickness T2 from the wall thickness T1 and a groove 4 on the inside wall surface having the thickness T2 is formed by the circumferential rotation of the roll. Thereupon, the rotation of the roll 3 is shifted axially, then the hollow groove having the thickness T2 is formed axially and continuously until finally the pipe 1 is adhered tightly, as the inside pipe having the wall thickness T2 reduced from T1, to the pipe 2. The pipe 1 is restrained by the pipe 2 by which a self-tightening effect is induced in the pipe 1 itself. The pipe 2 and the pipe 1 are thus tightly fastened and is applied with a compression stress.

Description

DETAILED DESCRIPTION OF THE INVENTION The disclosed technology belongs to the technical field of coupling outer and inner pipes of double pipes used for, for example, chemical plan 1-1 oil country tubular goods, oil delivery pipes, and heat exchanger pipes.

Therefore, in this invention, an inner tube made of stainless steel or the like is layered on an outer tube such as a carbon steel tube, and the inner tube is mechanically expanded and expanded so as to be tightly connected to the outer tube with a degree of fit. The invention relates to a method for manufacturing a double-walled pipe, and in particular, it involves continuously applying local mechanical pressure to a part of the inner wall of the inner wall using a roller or the like, and turning the inner wall of the inner wall into an outer wall. While pressing the direction, press the [J-
By rotating the roller in the circumferential direction and moving in the tube axis direction, the entire inner tube wall is expanded and expanded, and the inner tube is expanded and expanded due to the restraint on the outer tube. The present invention is directed to a method for manufacturing a double-walled pipe in which a self-tightening effect is induced in the inner pipe itself, and as a result, the inner and outer pipes are fastened together with a degree of fit.

As is well known, piping used for chemical blunts, oil country tubular goods, oil pipes, heat exchangers, etc. is made of carbon steel pipes, for example, depending on the purpose of high and low temperature resistance, strength, corrosion resistance, etc. Stainless steel pipes have been used.

However, in recent years, even higher performance has been required for these steel pipes, for example, they are required to withstand high temperature and high pressure in terms of strength, and have a high degree of corrosion resistance. To give an example of a special metal that can withstand high pressure under high temperature and withstand 1η, one example is high nickel material, which is extremely expensive and has poor durability compared to ordinary piping materials. Therefore, high-grade carbon steel pipes are generally used.

However, as the strength of high-grade carbon steel increases, its corrosion resistance tends to deteriorate, and to deal with this, stainless clad steel or carbon steel pipes with outer pipes are usually used.
A double pipe has been developed in which a stainless steel pipe is fitted as an inner pipe.

Stainless clad steel is a conventionally used material, but when high-grade carbon steel is clad with high-grade stainless steel through forge welding at high temperatures, the former exhibits its own strength and high-grade performance. On the other hand,
The latter also requires its own unique heat treatment in order to exhibit its own high-grade corrosion resistance performance, and high-grade carbon steel and high-grade stainless steel each require unique and different heat treatments for clad steel, which is made of the same material. The drawback is that it is extremely difficult, or rather, almost impossible, to achieve the high-quality performance of each material.

Furthermore, there is a large difference in strength at high temperatures between carbon steel and stainless steel, and in addition, there is a large difficulty in forge welding due to the difference in coefficient of thermal expansion.

In particular, the production of clad steel pipes made of carbon steel or stainless steel has the above-mentioned difficulties in comparison with the production of general clad steel plates, and has the disadvantage that the production cost is extremely high.

Therefore, we manufactured the high-grade carbon steel outer tube and the high-grade stainless steel inner tube separately, applied optimal heat treatment to each material of the inner and outer tubes, and then joined them together in a state that brought out the best performance of each material. Heavy pipe manufacturing technology has been developed.

One of these methods is the so-called hardening method, in which an inner tube with an outer diameter larger than the inner diameter of the outer tube by the amount of fitting and a corresponding outer tube are prepared in advance by precision machining. The outer tube is heated to enlarge the diameter of the outer tube, the inner tube is inserted into the outer tube, and the inner and outer tubes are tightly fastened together by cooling the m-layer outer tube by 71 degrees and thermally shrinking.

In order to uniformly cool the outer tube by inserting the inner tube with a fitting margin into the thermally expanded outer tube, and to obtain a predetermined tightness, a uniform and precise machine is used for the inner and outer tubes. Machining is extremely difficult, and in particular, it is nearly impossible to perform precision machining on a long, thin-walled inner tube.

Another conventional method is the tube expansion method, in which expansion pressure is applied via fluid to the inner tube inserted into the outer tube at room temperature, the inner and outer tubes are expanded until plastic strain occurs, and after the pressure is removed,
Although the inner and outer tubes are designed to be fastened with a fitting distance of 1q, which corresponds to the difference in yield strength that each has as a characteristic,
There is a problem in that there is a material restriction such that the yield strength of the outer tube must be at least higher than that of the inner tube in order to achieve a 1Q fit.

Recently, there has been a strong demand for the development of pipes that have not only strength but also a high degree of corrosion resistance, but the material that controls corrosion resistance has a tendency to be under compressive stress inside the material when in use. It has become clear that it is desirable from the standpoint of having corrosion resistance of 1f, such as preventing stress corrosion cracking.

Therefore, in double pipes, especially long, thin-walled 2m pipes, it is possible to give the inner pipes made of stainless steel, etc., which contributes to the corrosion-resistant function, a highly uniform compressed internal horn.'' Double @ by conventional method! ! This method is extremely difficult to manufacture, and even if it were possible, it would have the disadvantage of being expensive due to the complexity of the manufacturing process.

The purpose of this invention is to solve the problems of corrosion-resistant double pipes based on the above-mentioned conventional technology. The concept is completely different from conventional methods such as the pipe expansion method used, and a local mechanical spreading saw is used to form a highly compressed path in the inner pipe, thereby reducing the inner and outer pipes by 1q. It is an object of the present invention to provide an excellent double-pipe manufacturing method that is useful in the field of corrosion-resistant piping used in various industries.

In order to solve the above-mentioned problems, the present invention has a structure in which a corrosion-resistant inner tube made of stainless steel or the like is laminated inside an outer tube made of carbon steel or the like, and a spreader such as a roller is set inside the inner tube. , a predetermined spreading force is applied locally to the inner wall surface of the inner tube and continuously applied to the entire surface in the same direction and the entire surface in the axial direction to spread and expand the inner tube, during which self-tensioning action is applied to the inner tube itself. In order to prevent axis misalignment by forming a joint in the outer tube and tightening it, at the same time, compressive stress is formed on the inner wall surface of the inner tube to prevent stress corrosion cracking, etc., and technical measures are taken. This is a summary of what happened.

Next, embodiments of the present invention will be described below with reference to the drawings.

The principle diagram is shown in Fig. 1.2. A stainless steel inner tube 1 having a wall thickness of T1 is set in a relatively overlapping state with a carbon steel outer tube 2, and a roller 3 is tightened in a predetermined manner on a part of the inner tube. When the inner tube 1 is rotated by applying a spreading force to it, the inner tube 1 becomes T+.
The groove 4 in the inner tube wall having a thickness T2 is formed by rotation in the circumferential direction.

Therefore, if the rotation of the roller 3 is shifted along the axial direction, the concave groove 4 with the wall thickness T2 will continue in the axial direction, and the inner tube 1 will eventually become flat, and the inner tube 1 will be reduced to a wall thickness of T2. The circumferential and axial extensions close to the outer tube and corresponding to a wall thickness reduced from wall thickness T+ to wall thickness T2 are (j).

However, this inner tube 1 is actually restrained by the outer tube 2 and causes a self-tensioning effect on the inner tube 1 itself, and as a result, the outer tube 2 and the inner tube 1 are tightly connected and compressive stress is applied. be done.

In FIG. 3, there are two rollers 3.3' on opposite sides, and as shown in FIG.
It is possible to set one or a plurality of L1-L3 cylinders, such as an embodiment in which L1-L3 is arranged every 120 degrees.

Next, the embodiment shown in FIG. 5 will be explained.
The double material tube 7 made of the carbon steel outer tube 2 and the stainless steel inner tube 1 layered relative to each other as described above is set on the stand 6.6 provided on the stand 6. A beam 10, which is provided so as to be able to slide in any direction, is concentrically placed in the material double tube 7, set on a stand 13 having a stand 11 and a winding device 12, and attached to a reel 14 and a core 15 of a motor 9. Stretch cable 1G.

Therefore, the motor 9 is rotated on one end side of the material double tube 7,
The rollers 3 are attached to and pressed against the inner wall surface of the inner tube 1 and rotated and rotated, and by pulling the cable 16 at a set speed, the rollers 3 press and expand the entire inner wall surface of the inner tube 1 in a spiral shape.

As described above, since the inner tube 1 is restrained by the outer tube 2, the inner tube 1 is thinned and self-tightened with a fitting allowance, and compressive stress is applied to the inner tube 1.

Further, the embodiment shown in FIG. 6 has two or more double pipe single pipes 7',
1' is made into a long pipe through the welded joint 11, and the ends of the single pipes are welded together in the heat affected range H by forming the welded joint 17. The double pipes formed at the time of manufacturing each single pipe 7' are tightly fastened together. However, in this case, it becomes possible to restore the tight connection even in the heat-affected range of the welded joint 17 due to the rotation and rotation of the roller 3 while pressing the welded joint 17.

In the embodiment shown in FIG. 7, when the inner tube end is welded overlay 18 as a tube end treatment for the double tube 7', the double tube is stuck together over the area 1-1 affected by the welding heat at the tube end. Although loosening of the fastening occurs, the loosened fastening is recovered by using the suppressing means of the roller 3 as described above.

4 In addition, in the embodiment shown in FIG. 8, welding overlay 19 is performed on the outer tube end as a single tube end treatment for a coupling joint of a double pipe 7', and the rear end is machined and finished 20 for a joint. When performing this, a weld heat affected area H is formed by weld build-up, but
This invention makes it possible to recover from loosening of double pipe fastening.

The manufacturing principle of this valve opening described above with reference to the drawings is based on the mode in which the spreading roller rotates along the inner surface of the double tube in a direction perpendicular to the tube axis.

However, even if this spreading roller rotates along the inner surface of the double tube in the tube axis direction or diagonally to the tube axis, the effect of spreading the inner wall of the inner tube, which is the basic principle of this invention, remains the same. .

It should be noted that the embodiment of the present invention is not limited to this example. For example, instead of spreading with a roller, it is possible to spread with impact peening, shot blasting, etc. In each of the above embodiments, a double pipe with an inner pipe made of stainless steel has been described, but in the double pipe according to the present invention, as long as the material of the inner pipe is expandable, there are no restrictions on the selection of materials for the inner and outer pipes. Of course, there are no restrictions.

As described above, according to the present invention, in a double pipe in which an inner pipe is relatively layered on an outer pipe, it is easier to form a double pipe than a clad steel τ double pipe, a shrink-fit double pipe, or a double pipe made by the tube expansion method. An excellent effect is achieved in which a tightly fastened double pipe can be manufactured reliably and at a low cost.

As a result, a highly self-tensioning, corrosion-resistant double-walled pipe can be created simply by applying mechanical stretching force after relatively overlapping the inner and outer pipes, resulting in uniform precision machining of high hemp on the firing surface and long, thin-walled inner pipes. Difficulties such as heating and inserting the tube can be avoided, the number of man-hours is small, and the excellent effect of manufacturing with high efficiency and low cost is achieved.

Further, according to the present invention, even a long thin-walled inner pipe can be covered with a self-tightening corrosion-resistant double pipe, and compressive stress can be applied to the inner pipe when performing the spreading action. It also has the effect of preventing stress corrosion cracking during operation.

[Brief explanation of the drawing]

The drawings are detailed explanatory views of the present invention, with FIG. 1 being a partially cutaway perspective view for explaining the principle, and FIG. 2 being a cross-sectional view of the embodiment. 2...Outer tube, 1...Inner tube, 7'...
Double Pipe Procedures - Sansho (Volunteer) December 13, 1982.・Former Commissioner of the Japan Patent Office Kazuo Wakasugi 2 Name of the invention Double pipe manufacturing method 3 Relationship with the person making the amendment Case Patent applicant address 1-2-234 Rikyumae-cho, Suma-ku, Kobe City,
5. The specification to be amended (1) and the scope of the claims are as follows: [In a double pipe manufacturing method in which an inner pipe is relatively stacked on an outer pipe, the inner pipe is expanded and expanded, and is tied to the outer pipe.] (After the inner pipe is relatively stacked on the outer pipe, local A mechanical stretching force is continuously applied to the inner tube wall, this is applied to the entire inner tube type, the inner tube inner wall is expanded and expanded, and both tubes are tightened through the self-tightening effect of the inner tube caused by the expansion. 2. In the specification, page 6, line 16, ``same direction'' is changed to ``circumferential direction.''
First of all, please correct it.

Claims (1)

[Claims] In a double tube manufacturing method in which an inner tube is relatively stacked on an outer tube, the inner tube is expanded and expanded, and then tied to the outer tube, after the inner tube is layered on the outer tube, local mechanical treatment is performed. A stretching force is continuously applied to the inner tube wall, this is applied to the entire inner tube type, the inner tube inner wall is expanded and expanded, and both tubes are tightly fastened together through the self-tightening effect of the inner tube caused by the expansion. The double tube llllll method is characterized by the fact that it is made to do so.