JPH0787941B2 - Double pipe manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The disclosed technology relates to pipes for transporting corrosive fluids, etc.
The outer tube is a pressure-resistant and heat-resistant metallic material of carbon steel or stainless steel, and the inner tube is a highly corrosive and wear-resistant metallic material of stainless steel or chromoly steel, or a ceramic material typified by alumina. Belongs to the field of manufacturing technology of tightly-coupled double tube.

<Summary of summary> The invention of the present application, therefore, has a ring-shaped outer tube made of carbon steel or the like and an inner tube made of SUS or the like, which are laminated to each other in a loosely inserted state to form a raw tube. A high-frequency induction heating device is used to heat the outer tube from the outside of the tube, or in the case of a metal material, from the inside to perform solution heat treatment, and before and after that, it is rapidly cooled via a shower ring with tap water. The present invention relates to a method for producing a double pipe in which an outer pipe is tightly connected to an inner pipe or an inner pipe is tightly connected to an outer pipe by performing ring heat shrinkage or ring heat expansion, and particularly, the high frequency induction heating described above. For the annular heating / cooling in solution heat treatment by an apparatus, etc., the heating temperature of the annular heating is controlled so as not to plastically deform in accordance with the yield stress of the outer tube, and then quenching is performed. , Annular heating and cooling by a high frequency induction heating device A double tube that is designed to perform relative movement and relative rotation in the axial direction of the tube, or to perform annular heating with a temperature gradient in the plate thickness direction of the tube, or to raise the maximum temperature. The invention relates to a manufacturing method.

<Prior Art> As is well known, piping is widely used in many fields and in various industries, and is not only used for fluid transport as it is.
In recent years, it has come to be used not only for information transmission but also for structural members, etc. Therefore, not only the function of piping is not only pressure resistance and heat resistance due to strength, rigidity, etc., but also
Many of the multiple functions such as flexibility, corrosion resistance, and wear resistance are required, and moreover, it is necessary to operate those under severe conditions that require these multiple functions. In the field of new technology in industry, heavy chemical industry, etc., more and more of these complicated functions and higher functions are required.

However, despite the active development of new materials and materials, in the present technology, materials and materials that satisfy all these complicated functions and conditions with one material have not yet been developed, Therefore, for example, the outer tube is made of carbon steel to control the pressure resistance and heat resistance, and the inner tube is made of stainless steel to control the corrosion resistance and wear resistance according to the application. Double-walled tubes such as double-walled tubes that are tightly fitted to each other have been used.

By the way, when the outer tube (outer tube) and the inner tube (inner tube) are tightly bonded in such a double tube, the clad method, the shrink fitting method, and the hydraulic expansion method have been developed so far. However, there are drawbacks such as technical advantages and disadvantages, economically unbalanced, and lack of reliability of product accuracy.

On the other hand, a so-called heat expansion tube method or a recent ring heat reduction method (ring heat expansion method) as shown in many of the applicant's inventions and inventions of the applicant is a double tube production method effective. Has been put into practical use as research and development, but in order to strengthen the fitting force between the outer tube and the inner tube and to reveal a sufficiently tightly connected state, secondary heat treatment etc. is required to improve the material quality. , In the ring thermal reduction method,
When carbon steel is used for the outer tube, the outer tube is reduced in diameter to withstand practical use at about 800 ° C, and the transformation temperature of the carbon steel increases.
Since the temperature is around 900 ° C, effective heat treatment (normalization) for material improvement by ring heating / cooling in these temperature ranges was performed in combination with diameter reduction.

In addition, the above-mentioned aspect is a case where it is used as γ-based stainless steel.

<Problems to be Solved by the Invention> However, as described above, when a technique such as piping in a nuclear power plant or piping in a corrosive fluid is recently required, the outer pipe of the double pipe is Not only carbon steel but also special steel such as stainless steel or chromoly steel, which is tightly fitted to a ceramic inner pipe, has been newly demanded.

In addition, when an excessive binding stress occurs when the outer tube made of stainless steel or chromoly steel is tightly fitted to the inner tube made of ceramics, thermal shock during operation of the inner tube made of ceramics is generated. There is a risk of breakage and cracks during manufacturing.Therefore, it is necessary to find the optimum tight fitting by the use of piping and the selected combination of outer and inner pipes. Ring heat shrinkage (ring thermal expansion diameter) that causes multiple fittings to be performed more than once and to be tightly bonded so that optimum fitting stress is generated gradually without variation.
The method has suddenly come into the limelight.

Then, when the ring thermal contraction method is outlined according to the drawing,
As shown in FIG. 1, an inner tube 2 is loosely inserted into a predetermined outer tube 1 with a gap therebetween, and the layers are relatively laminated to form an elementary tube 3. Then, as shown in FIG. A high-frequency induction heating device 4 as an annular heating device at a predetermined portion of the outer pipe 1 of the base pipe 3 which is relatively overlaid, and a water supply as an annular cooling device before and after the high-frequency induction heating device 4 with a predetermined axial interval. The shower ring cooling device 5 made of water or the like is integrally set, and the base pipe 3 is relatively moved with respect to the high frequency induction heating device 4 and the shower ring cooling device 5 at a predetermined axial speed and is relatively rotated. Then, when the portion of the outer tube 1 corresponding to the high-frequency induction heating device 4 is a short tube and both ends thereof are free ends, the diameter is expanded as a whole, but both ends of the heating portion are in the axial direction. Restraint on the outside, and before and after the shower ring To be quenched by retirement unit 5,
As shown in FIG. 3, the pressing bending moment F acts to heat-treat the material, and the so-called ring thermal contraction is performed, so that the outer tube 1 contracts as shown in FIG. By repeating the process, the outer tube 1 is reduced in diameter with respect to the inner tube 3 to be tightly fitted in a predetermined manner.

Regarding the ring thermal expansion diameter of the inner pipe 2, the high frequency induction heating device 4 and the shower ring cooling device 5 are set inside the inner pipe 2 so that a warp bending moment is applied to the inner pipe 2. The inner tube 2 is expanded relative to the outer tube 1.

However, when new demand arises and the outer tube 1 is made of stainless steel, chromoly steel, or the like, the transformation temperature is higher and the yield stress is higher than when carbon steel is used. The heating temperature has to be higher than that of carbon steel and the heat management for suppressing the temperature lower than the transformation temperature is difficult.

Further, according to a plurality of types of repeated experiments, a ring thermal contraction having a sufficiently noticeable tight fitting stress when the heating temperature of the outer tube 1 in the plate thickness direction by the high frequency induction heating device 4 is uniformly distributed. A bug was discovered that could not be obtained as designed.

It was also discovered that if the ring heat history varies depending on the material of the tube, the material of the tube after heat treatment may deteriorate.

<Object of the Invention> The object of the invention of the present application is a ring thermal contraction (expansion) based on the difference in the material of the outer tube and the inner tube in the double tube such as a double tube due to the ring thermal change based on the above-mentioned prior art. It is a technical issue to solve the problem of tight fitting due to, and while using the advantage of ring heat variable diameter that can obtain a constant tight fitting by reducing the outer pipe by one pass with respect to the inner pipe, Providing an excellent double pipe manufacturing method that can be optimally connected by heat treatment of the outer pipe depending on the combination of the materials of the outer pipe and the inner pipe, and which is useful in the field of piping technology application in various industries. It is something to do.

<Means / Action for Solving the Problems> In order to solve the above-mentioned problems, the structure of the invention of the present application, which has the above-mentioned claims as its gist, has a gap between an outer pipe and an inner pipe of a predetermined material. While forming a raw pipe by laminating the pipes in a loosely inserted state through a tube, set a ring-shaped heating device such as a high-frequency induction heating device in a predetermined part of the pipe body, and tap water in at least one of the front and back. Set a ring-shaped cooling device such as a shower ring cooling device by
The ring-shaped heating device, the ring-shaped cooling device, and the tube in which the tube body is layered relative to each other are axially moved relative to each other in a predetermined manner and are also rotated together. The outer tube is reduced in diameter by heating or rapid cooling after heating, or the inner tube is expanded, and by repeating this process, the outer tube is bonded to the inner tube or the inner tube is bonded to the outer tube. When mating, the heating temperature is controlled below the transformation temperature of the outer tube by the material of the inner and outer tubes, and the heating temperature is set according to the yield stress to obtain the maximum diameter reduction ratio, and a reliable and remarkable diameter reduction is obtained. In addition, the temperature is improved so that a gradient (temperature difference in the plate thickness direction) is given to the heating temperature in the plate thickness direction of the raw tube, and the maximum heating temperature is raised further It is a technical measure that makes it possible to obtain such a reduced diameter.

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

The outer pipe 1 made of carbon steel (S55C) having a normalizing temperature of 800 to 850 ° with respect to the inner pipe 2 made of ceramics has a predetermined gap with respect to the inner pipe 2 as shown in FIG. 2 and 3 in a loosely inserted state to form a tubular body 3 of a raw tube, and as shown in FIG. 2, a high frequency induction heating device 4 as an annular heating device at a predetermined portion of the carbon steel outer pipe 1. And the shower ring cooling device 5 with tap water as a ring-shaped cooling device is integrally set at the front and rear through a predetermined axial interval of the tubular body 3, and annular heating by the high frequency induction heating device 4 is performed. To 850 ° C., which is lower than 900 ° C. which is the transformation temperature of the outer tube 1, to relatively move the tube body 3 in the axial direction and to relatively rotate in the circumferential direction so that a uniform diameter reduction can be made in the circumferential direction ( Either one of the tube body 3 and the heating and cooling devices 4 and 5 or both are rotated), As shown in the above theory, the carbon steel pipe as the outer pipe 1 is ring-heat-reduced and reduced in diameter without deterioration of the material due to normalization. The pipe 1 is adapted to be tightly fitted to the inner pipe 2 to obtain a double pipe 6.

In the annular heating / cooling process, the temperature unevenness in the pipe circumferential direction can be made extremely small by rotating the tube or the annular heating / cooling devices 4 and 5.

As a construction example, high frequency induction heating coil (coil length Bm
m) 4, when the pipe is moved in the axial direction at a certain transport speed (vmm / min), the number of revolutions (as a guideline for N rpm, By doing so, the local portion in the circumferential direction of the pipe that passes while rotating just below the coil can always make a round immediately below the coil (the heating effect is the highest in this part), and the pipe can be heated without uneven temperature in the circumferential direction. It can be done (see FIG. 2).

Then, in the annular heating of the outer tube 1 by the high frequency induction heating device 4 in each ring thermal contraction process, the heating temperature applied to the outer tube 1 is applied with a difference of 850 ° C. to 800 ° C. according to the normalization. .

Further, depending on the thermal history of the base pipe 3 due to the above-mentioned changes in heating conditions, the base pipe 3 is conditioned to prevent deterioration of the material.

By doing so, a remarkable ring heat shrinkage can be obtained,
There is no crack of the inner pipe 2 during manufacturing or breakage during operation after installation.

Further, in the above-mentioned ring thermal shrinkage, the maximum amount of heating temperature is set to, for example, 1050 ° C., whereby the amount of shrinkage can be increased.

Next, in the second embodiment, stainless steel is used as the outer tube 1 under the solution heat treatment condition of annular heating and cooling to a temperature slightly higher than the solution heat treatment temperature, and as shown in FIG. When a temperature gradient of 100 ° C. or less, for example, 50 ° C., was applied between the outer surface and the inner surface of the outer tube 1 in the plate thickness direction, a uniform diameter reduction with a large diameter reduction ratio was obtained.

By doing so, the outer tube 1 is not deteriorated by heat treatment, the inner tube 2 is not cracked, and the double tube 6 having the fitting stress as designed is obtained.

Moreover, such results have been confirmed by experiments.

Of course, the embodiment of the invention of this application is not limited to each of the above-mentioned embodiments. For example, the heating temperature is changed to control the amount of change in the pipe diameter, or as described above, the outer pipe 1 The inner tube 2 is expanded in place of the reduced diameter to tightly connect the inner tube 2 to the outer tube 1. At that time, the maximum temperature of the heating section is increased, and the heat history of the tube causes the material of the tube body to be increased. It is possible to operate various modes such as adjusting

Further, as a design change, the material of the outer tube 1 is not limited to the above carbon steel and stainless steel, but can be applied to other special steel materials, and the inner tube 2 may be reduced in diameter depending on the design mode. By doing so, it is possible to separate the outer tube 1 from the inner tube 2 by expanding the outer tube 1 so as to separate the inner tube 2 from the outer tube 1. is there.

And, as a matter of course, the target pipe body can be applied not only to a double pipe but also to a double pipe of three or more pipes.

<Effects of the Invention> As described above, according to the invention of the present application, the ring thermal contraction diameter of a double-walled tube such as a double tube in which the combination material of the outer tube and the inner tube, which have various new needs recently, is basically different ( For tight fitting by bulging
The temperature of the annular heating according to the yield stress of the outer tube (inner tube) for each application to the inner tube (outer tube) is controlled and given to the heat treatment condition that deteriorates the material, and the heating and cooling equipment and tube Due to the relative rotation of the body, the outer tube is fitted to the inner tube with the optimum diameter reduction ratio (the inner tube has the optimum expansion diameter to the outer tube) with uniform accuracy, and therefore during manufacturing The excessive fitting stress in the above is not applied to the outer pipe and the inner pipe, and therefore, the cracks and the breakage during the operation are not generated, and the excellent effect that the durability of the pipe is improved is exhibited.

Thus, the annular heating / cooling treatment is applied to the tubular body with a temperature gradient in the plate thickness direction of the outer tube, whereby the variation of the tubular diameter can be changed and a large amount of tight binding can be obtained. The effect is played. Then, there is an effect that a more remarkable diameter reduction (expansion) can be obtained.

By doing so, there is an effect that the heat treatment is efficiently performed without deteriorating the material of the outer pipe in the double pipe manufacturing, and an ideal double pipe or the like as designed can be obtained.

[Brief description of drawings]

The drawings show the basic mode of ring thermal contraction. Fig. 1 is a partial cross-sectional view of relative layers of an outer pipe and an inner pipe, Fig. 2 is a partial cross-sectional view of annular heating and annular cooling, and Fig. 3 is FIG. 4 is a schematic perspective view of applying a pressing bending moment to the outer tube, FIG. 4 is a partial sectional view of a double tube formation, and FIG. 5 is a graph of temperature distribution in the tube thickness direction of annular heating. 1 ... Outer tube, 2 ... Inner tube 3 ... Element tube, 4 ... Ring heat heating device 5 ... Cooling device, 6 ... Double tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 1-233012 (JP, A) JP-A 1-118306 (JP, A)

Claims (5)

[Claims] 1. A method for producing a double pipe by applying annular local heating / cooling to a raw pipe in which an outer pipe and an inner pipe are layered relative to each other. A method for producing a double tube, which is characterized by suppressing the temperature to a temperature not higher than the transformation temperature of the outer tube and setting it to a heating temperature according to its yield stress, and thereby rotating the element tube and the annular local heating / cooling relative to each other. 2. The double pipe according to claim 1, wherein the process of performing the relative rotation of the annular local heating / cooling is performed while imparting a temperature difference in the plate thickness direction. Production method. 3. The process according to claim 1, wherein the process of rotating the annular local heating / cooling relative to each other is performed while changing the heating temperature and changing the diameter reduction amount.
The method for producing a double tube according to the item. 4. The double pipe according to claim 2, wherein the process of performing relative rotation of the annular local heating / cooling is performed by raising the maximum heating temperature to a constant temperature. Production method. 5. The double structure according to claim 1, wherein when applying the treatment in which the annular local heating / cooling is relatively rotated, the material of the tubular body is tempered. Pipe manufacturing method.