JP2575043B2 - Double pipe manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The disclosed technology belongs to a technical field of manufacturing a double pipe used for an oil feed pipe or the like.

<Summary of the Summary> Accordingly, the present invention provides a method of increasing the diameter of the inner pipe by so-called ring heat shrinking after the inner pipe made of stainless steel and the like and the outer pipe made of carbon steel are relatively layered. The present invention relates to a method for manufacturing a double pipe in which an inner pipe and an outer pipe are integrated by applying a diameter reducing method or at least via the latter, and in particular, as described above, the inner pipe and the outer pipe are connected to each other. When the layers are relatively layered, the outer surface of the inner tube, the inner surface of the outer tube, or a joining material such as a brazing material between the two tubes is formed into a paste in the form of a line, a sheet, or a powder. After melting according to the gap of the pipes, it is interposed so as to be evenly distributed after the melting, and at least the latter is required to increase the inner pipe diameter by expanding the pipe and reduce the outer pipe diameter by the above ring thermal reduction method. When the diameter is reduced, the joining material is melted to be interposed uniformly between the inner pipe and the outer pipe, and the molten joining material is allowed to cool by cooling. The present invention relates to a method for manufacturing a double pipe in which a solidified state is maintained over time by solidifying and fitting an inner pipe and an outer pipe through the solid pipe.

<Prior Art> As is well known, pipes such as pipes are used in many fields, and are used not only for transporting liquids and gases, and even powders, but also in recent years. In addition to being used as structural members such as beams of objects, they are also being used for information transmission means such as surrounding tubes such as cables, air shooters for documents, and voice tubes. Are involved.

Therefore, these pipes are exposed to unfavorable conditions such as thermal behavior due to relative changes and differences in physical and chemical conditions inside and outside the pipes during operation, displacement due to relative displacement, and furthermore, corrosion and wear. Therefore, the pipes are required to have functions such as heat resistance, pressure resistance, corrosion resistance, and abrasion resistance as necessary conditions, and in particular, pipes extending over long distances on the seabed or land. In such a case, once laid, it is difficult to replace or re-lay the pipe due to a long piping distance. Therefore, it is strongly demanded that the durability including these conditions be high.

However, since the development of the material technology that constitutes the piping itself has not yet been sufficiently developed in response to the demand for long piping in various fields, a piping material that satisfies all of the above severe conditions with one material has not been developed. Therefore, in reality, double pipes that selectively impart pressure resistance, heat resistance, etc. to the outer pipe, and corrosion resistance, wear resistance, etc. to the inner pipe have been developed and adopted in various ways. Further, a double pipe such as a triple pipe or a quadruple pipe has been developed based on the double pipe.

Therefore, in the production of such a double tube, Japanese Patent Application Laid-open No.
-85684 No. thermal expansion method as disclosed in the invention,
Alternatively, a new technology such as a ring thermal contraction method as disclosed in the invention of JP-A-61-283416 has been developed and put into practical use.

The ring thermal contraction method is briefly described with reference to FIGS. 7 and subsequent drawings. As shown in FIG.
On the other hand, the inner tube 2 is relatively layered in a loosely inserted state through a predetermined gap to form a tube 3, and then, as shown in FIG. 8, the outer tube of the layered tube 3 is laminated. A high-frequency induction heating device 4 as an annular heating device and a cooling device 5 with a shower ring using tap water or the like as an annular cooling device are provided at a predetermined portion of the device at a predetermined axial distance before and after the high-frequency induction heating device 4. When the raw tube 3 is moved relative to the high-frequency induction heating device 4 and the cooling device 5 using a shower ring at a predetermined speed in the axial direction as shown by an arrow, the relative rotation is performed. When the portion of the outer tube 1 corresponding to the high-frequency induction heating device 4 is a short tube and both ends are free ends, the diameter of the entire tube expands, but both ends of the heating portion are restrained at their axial outside. And before and after As shown in FIG. 9, the material is rapidly cooled by the cooling device 5, and as shown in FIG. As described above, the outer tube 1 is reduced in diameter, and by repeating such a process in the axial direction, the outer tube 1 is reduced in diameter to the inner tube 3 so as to be tightly fitted.

<Problems to be Solved by the Invention> However, in the production of double pipes by the above-mentioned conventional technique, generally, a tensile residual stress is formed on an outer pipe and a compressive residual stress is formed on an inner pipe, so that a fitting force is formed. Had some limitations.

By the way, it is indispensable that the inner pipe 2 and the outer pipe 1 are tightly fitted and integrated to prevent relative displacement or implosion between the inner pipe 2 and the outer pipe 1 during operation. It has been strongly desired that residual stresses be uniformly formed on the inner and outer tubes 1 and 2 to obtain a large fitting force.

<Object of the Invention> The object of the present invention is to solve the problems of the production of a double pipe based on the above-mentioned prior art, and it is assumed that the inner pipe and the outer pipe are integrated by a tight connection. Tubes, and
An excellent double pipe that benefits the piping technology application field in various industries by allowing compressive stress and tensile residual stress to be uniformly generated in the outer pipe in the circumferential direction, and by applying a bonding force by brazing to be integrally joined. It does not provide a manufacturing method.

<Means and Actions for Solving the Problems> In order to solve the above-mentioned problems, the structure of the present invention, which is based on the above-mentioned claims and pursues the above-mentioned object, comprises a highly corrosion-resistant inner tube made of stainless steel or the like, When obtaining a double pipe that integrates a pressure-resistant, heat-resistant outer pipe made of steel or the like, the outer surface of the inner pipe when the inner pipe and the outer pipe are relatively layered through a slight predetermined gap, Alternatively, the inner tube of the outer tube, or a paste material in the form of a line or a sheet between the two tubes, or a bonding material such as a powdered brazing material is applied to form an interposed state, and the inner tube is connected to the inner tube. After the outer tube is relatively layered, the inner tube and the outer tube are integrated by applying at least the latter of diameter increase and diameter reduction through the above-mentioned ring thermal contraction method for the hydraulic expansion and the outer tube for the inner tube, At that time, the outer tube is heated when the outer tube is reduced in diameter, so that the brazing material is melted by the heating action, and the space between the inner and outer tubes of the joining material is reduced. It is integrated through a uniform distribution over the entire pipe, and then cooled to solidify the molten joint material between the inner pipe and the outer pipe. In this case, technical measures are taken such that the two pipes are maintained in an integrated state over time in a state where residual stress is generated. Embodiment Next, an embodiment of the present invention will be described below with reference to the drawings.

Note that the same parts as those in FIG. 7 and below are described using the same reference numerals.

In the embodiment shown in FIGS. 1 to 4, first, as shown in FIG. 1, a paste-like joining material is formed on the inner surface of the outer tube 1 made of carbon steel in a predetermined row along the longitudinal direction. Lumber 7, 7
Is applied, and in this state, the inner tube 2 made of stainless steel is superposed on the outer tube 1 via a predetermined gap 8 having a ring shape as narrow as possible.

Next, as shown in FIG. 2, a predetermined hydraulic pressure F is applied to the inner pipe 2 by a so-called thermal expansion method as shown in the prior application of the applicant, and the inner pipe 2 is increased in diameter. Then, the inner pipe 2 is increased in diameter and integrated with the outer pipe 1 so that the inner pipe 2 is integrated with the outer pipe 1 as shown in FIG. The brazing material 7 'between the two pipes 1, 2
In this state, the heater 4 'as an annular heating device is installed in a ring shape outside the outer tube 1 as shown in FIG. The ring-shaped brazing material 7 ′ is heated and melted by the annular heating through the outer tube 1 by applying the diameter method, so that the brazing material 7 ′ is further completely interposed between the inner tube 2 and the outer tube 1. It melts around the corners uniformly without any corners, and has a function of joining the inner and outer tubes 1 and 2. Thereafter, the brazing material 7 ′ is solidified by natural cooling, and the inner tube 2 and the outer tube are solidified. As shown in FIG. 4, the pipe 1 is integrally fixed with a molten adhesive, and the double pipe 6 can be obtained while maintaining the integrated state over time.

In addition, instead of increasing the diameter of the inner tube 2 in the above-described embodiment, the outer tube 1 is provided with a reduced diameter and adhered using only the ring thermal reduction method as disclosed in the above-mentioned prior application of the applicant. Brazing filler metal 7 '
The inner pipe 2 is integrated with the inner pipe 2 in such a manner that it can be uniformly melted in the circumferential direction. Needless to say, the ring heat reduction method also has an advantage that the melting of the brazing material 7 ′ by the ring heat reduction device installed on the outer periphery of the outer tube 1 is performed uniformly at once. is there.

Next, in the embodiment shown in FIGS. 5 and 6, the paste brazing material or the powder brazing material 7 is formed into a ring shape between the outer pipe 1 and the inner pipe 2 in the same manner as the above-described embodiment. The inner pipe 2 is uniformly inserted in a sheet shape, and the inner pipe 2 is increased in diameter by using a thermal expansion method in the inner pipe 2. The inner pipe 2 is integrated with the outer pipe 1 by applying a pipe expanding force F to the outer pipe 1 and a diameter reducing force F 'to the outer pipe 1, and the ring-shaped brazing material 7 is melted and The brazing material 7 'is uniformly interposed between the pipe 1 without any corners, and the inner pipe 2 and the outer pipe 1 are melted through the melting of the brazing material 7' by the ring thermal reduction method. The dual pipe 6 'is obtained through integration by the action of the brazing material 7', and by subsequent cooling by cooling, the solidification of the brazing material 7 'is maintained so that the integrated and tied state over time after production is maintained. Can do Is a Unishi was aspect.

Thus, in the obtained double pipes 6 and 6 ', the inner gap 2 between the inner pipe 2 and the outer pipe 1 at the time of relative layering is formed by the brazing material 7 interposed therebetween. Compressive stress is uniformly and slightly applied to the inner surface of the outer tube by the outer tube 1 (when a fitting force is generated,
A stress is generated in the inner and outer tubes 1 and 2. For example, if a compressive stress is generated in the inner tube 2, a tensile stress is generated as a reaction force in the outer tube 1. However, in the embodiment of the present embodiment, the brazing material 7 'is Since the brazing material 7 'is interposed in a uniform state in the circumferential direction, the tensile residual stress generated in the outer tube 2 is uniformly distributed without being displaced in the circumferential direction. The compressive stress generated as a content stress also occurs in the inner tube 1 in a uniform and uniform distribution in the circumferential direction, so that the inner and outer tubes 1 and 2 are uniform and uniform over the entire circumference. A good fitting force can be obtained.

In addition, the inner and outer pipes 1 and 2 are provided with a bonding force through the brazing material 7 ', and the relative displacement and peeling between the inner pipe 2 and the outer pipe 1 in the double pipes 6 and 6' during operation. And so on.

Of course, the intrinsic corrosion resistance and wear resistance of the inner tube 2 are sufficiently maintained, and the pressure resistance and heat resistance of the outer tube 1 are also sufficiently maintained.

<Effects of the Invention> As described above, according to the present invention, in a method for manufacturing a double pipe basically used for a pipe such as an oil feed pipe, basically, an inner pipe and an outer pipe are relatively separated via a predetermined minute gap. When layering, a joining material such as brazing material is interposed between the two tubes to increase the diameter of the inner tube, or to reduce the diameter of the outer tube by the ring thermal reduction method described above, or at least in addition to the latter. The inner pipe and the outer pipe are integrated via both, and the joining material interposed between the inner pipe and the outer pipe is melted by ring heating to form a uniform ring-shaped interposed state. The solidification of the molten joint material is allowed to cool through solidification by cooling, and at the time of fitting of the inner and outer tubes at least due to the reduction of the diameter of the outer tube, the compressive stress is applied to the inner tube by the action of the joining material in the circumferential direction. In the outer tube, residual stress is uniformly generated in the circumferential direction, and a uniform fitting force (joining force) is obtained in the circumferential direction. An excellent effect that a real joining state appears is exhibited.

In addition, since a molten joining material such as a brazing material is interposed between the inner tube and the outer tube during the relative layering, the inner tube and the outer tube are increased by the joining material by increasing the diameter of the inner tube and reducing the diameter of the outer tube. The temporal integration can be maintained thereafter, and the inner pipe and the outer pipe are always integrated as pipes, so that there is an effect that relative displacement does not occur during operation.

In addition, the inner tube and the outer tube are more strongly connected to each other through the joining force in addition to the fitting force by the joining material interposed between the inner tube and the outer tube, and the joining force is combined with the frictional force of the joining material. Since the connection can be made strong, there is an effect that an unexpected situation over time can be avoided.

[Brief description of the drawings]

Drawings are explanatory views of an embodiment of the present invention, FIGS. 1 to 4 are explanatory views of one embodiment, FIG. 1 is a cross-sectional view at the time of relative superposition, FIG. 2 is a cross-sectional view at the time of integration, FIG. 3 is a cross-sectional view when the joining material is melted, FIG. 4 is a cross-sectional view of a double pipe, FIGS. 5 and 6 are explanatory views of another embodiment, and FIG. ,
FIG. 6 is an integrated sectional view of the bonding material interposition, and FIGS. 7 to 10 are process sectional views of the ring thermal diameter reduction method. 2 ... inner pipe, 1 ... outer pipe, 6 ... double pipe, 7, 7 '... joining material

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kiyoshi Hasegawa 1-1, Kawasakicho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Inside the Akashi Plant (56) References JP-A-61-283416 (JP, A) 62-117387 (JP, U) Jiko 35-638 (JP, Y1)

Claims (1)

(57) [Claims] 1. A method for manufacturing a double pipe in which an inner pipe and an outer pipe are integrated with each other, wherein the inner pipe and the outer pipe are stacked relative to each other at the outer surface of the inner pipe, the inner face of the outer pipe, or between the two pipes. A joining material is interposed in advance, and at least the latter is performed to increase the diameter of the inner tube and reduce the ring thermal reduction of the outer tube, thereby integrating the two tubes and melting the joining material to integrate the two tubes. A method for manufacturing a double pipe, comprising: holding the pipe.