JP3522077B2 - Pipe manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an automobile exhaust pipe,
The present invention relates to a method for manufacturing a pipe such as a hollow double pipe used for a heat insulating pipe for a plant.

[0002]

2. Description of the Related Art In terms of arrangement, a pipe may be bent and used in order to avoid interference with other members. A filler is used for the purpose of preventing flattening and wrinkling when the pipe is bent. A hollow double pipe consisting of an outer pipe and an inner pipe is used as an exhaust pipe for automobiles, a heat insulating pipe for plants, etc., in which it is necessary to ensure the heat retaining property of the fluid, and the air in the gap between the outer pipe and the inner pipe is used. Although the layers are made to exert a superior heat insulating effect, when bending this hollow double pipe, it is especially necessary to use a filler in order to suppress eccentricity between the inner pipe and the outer pipe. It has become indispensable. As the above-mentioned filler, sand, ice, steel balls, low melting point alloys, wax, molten salt, etc. are currently used.

As an example of the prior art using a low melting point substance as a filler, there is a method disclosed in Japanese Patent Laid-Open No. 7-39943. The method shown in this publication is that a filler is injected into a straight tubular work, and the straight tubular work is bent while the filler is injected, and the bent tubular work after bending is a hot air circulation type using air as a heat medium. In the discharge furnace, the filler is melted and discharged from the curved tubular work.

[0004]

By the way, in the above-mentioned prior art, the discharge furnace is a hot air circulation type using air as a heat medium, and since the thermal conductivity of air is low, it takes a long time to melt the filler. Heating is required. Therefore, there is a problem that it takes a long time to discharge the filler.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a pipe which can shorten the discharge time of the filler.

[0006]

An invention relating to a method for producing a pipe according to claim 1 comprises a step of filling a straight pipe with a molten salt ,
A step of bending the straight pipe to obtain a bent pipe in a state where the molten salt is solidified; and a step of dipping the bent pipe in the liquid molten salt stored in a storage means And a step of melting and discharging the molten salt .

The invention described in claim 2 is the same as that of claim 1.
In the method for manufacturing a pipe, the liquid state stored in the storage means
In the molten salt in the state, place the curved pipe with the opening side facing downward.
Immerse and discharge the molten salt in the bent tube into the storage means
It is characterized by The invention described in claim 3 is
In the method for producing a pipe according to 1 or 2, in the straight pipe,
The molten salt to be filled is in a liquid state stored in the storage means.
It is characterized in that it is the molten salt in the form of. In claim 4
The invention according to claim 1 is the pipe according to any one of claims 1 to 3.
In the method for producing, the molten salt is water-soluble
Is characterized by. The invention described in claim 5 is the same as claim 1.
In the method for manufacturing a pipe of , the straight pipe is a hollow double pipe in which the inner pipe is inserted with a predetermined gap in the outer pipe, and a jig is provided so that the hollow double pipe can be mounted, and the jig is From a tubular jig body detachably connected to the opening of the outer tube, and a connecting portion that is connected to the jig body and has a protrusion on the tip side that is inserted into the opening of the inner tube. Configure the opening of the jig body
The inner peripheral side of the portion is formed into a funnel shape, the jig is attached to the opening side of the hollow double pipe, and the molten salt is placed in the tubular jig body.
By pouring, the molten salt is injected into the void through a gap between the jig body and the connecting portion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, a hollow double straight pipe (straight pipe) 1 is roughly composed of an outer pipe 2 and an inner pipe 4 which is inserted into the outer pipe 2 with a predetermined gap 3 therebetween.

On one end side of the inner pipe 4, there is formed an enlarged diameter portion 5 whose diameter increases toward the end. The outer diameter of the end of the enlarged diameter portion 5 is the inner diameter of the outer pipe 2. The dimensions are almost the same (dimensions that can be inserted). The outer diameter 2 and the inner diameter 4 are obtained by performing spot welding (the welded portion is indicated by G) on the expanded diameter portion 5.
Is fixed. Further, since the enlarged diameter portion 5 is spot-welded, the hollow double straight pipe 1 is such that the void 3 is closed on one end side and the opening portion 6 is formed on the other end side. A molten salt (for example, nitric acid-based molten salt) 7 is filled in the void 3 of the hollow double straight pipe 1. Specific examples of the nitric acid-based molten salt used as the molten salt 7 include those having chemical components (ratio) and melting points as shown in the following table.

As shown in FIGS. 2 and 3, a jig 8 is attached to the opening 6 of the hollow double straight pipe 1. The jig 8 is roughly composed of a substantially cylindrical jig body 9 that is detachably connected to the opening 2 a of the outer tube 2 and a connecting portion 10 that is connected to the inner wall side of the jig body 9. There is. The inner peripheral side of the opening 9a of the jig body 9 has a substantially conical shape (funnel shape).
Is formed in. On the tip side of the connecting portion 10, the protrusion 1
1 is formed and is adapted to be inserted into the opening 4 a of the inner tube 4. Reference numeral 12 in FIG. 4 denotes a salt bath (storage means) for storing the molten salt 7 in a liquid state. A propeller (not shown) is provided in the salt bath 12, and is driven by a driving means (not shown) to agitate the molten salt 7 in a liquid state to make its temperature uniform.

Next, a method for bending the above hollow double straight pipe 1 will be described below. First, as shown in FIG. 2, the jig 8 is attached to the opening 6 of the hollow double straight pipe 1. In this case, the jig body 9 is held by the outer tube 2, and in this state, the protrusion 11 of the connecting portion 10 is inserted into the opening 4 a of the inner tube 4. For this reason, the opening 4 of the inner pipe 4 with respect to the outer pipe 2
Since the a side portion is supported, the center line of the outer pipe 2 and the center line of the inner pipe 4 are surely aligned with each other. Next, as shown in FIG. 4, the molten salt 7 in the salt bath 12 is injected into the void 3 through the gap 13 between the jig body 9 and the connecting portion 10 (S1). At the time of injecting the molten salt 7 described above, the molten salt 7 is injected into the void 3 by pouring the molten salt 7 into the cylindrical jig body 9, so that the jig body 9 serves as a funnel. It becomes good.

Subsequently, the hollow double straight pipe 1 is cooled by a cooling device (not shown) to solidify the molten salt 7 therein (S
2). Next, the hollow double straight pipe 1 is bent while a solidified molten salt 7 is filled by a bender (not shown) to obtain a hollow double bent pipe 1A (S3). In this case, since the void 3 is filled with the molten salt 7 and the bending is performed in a state where the center line of the outer tube 2 and the center line of the inner tube 4 are surely aligned with each other, the outer tube 2 and the inner tube 4 have the same curvature. It becomes possible to bend and prevent eccentricity.

Subsequently, the hollow double bent pipe 1A is placed on a car (not shown) with the opening 6 side facing downward, and the car is lifted by a hoist (not shown) to be moved to the salt bath 12 and the salt bath 12 It is immersed in the molten salt 7 in a liquid state (S4). By immersing the hollow double-bent tube 1A in the liquid molten salt 7, the heat is rapidly transferred to the solidified molten salt 7 inside, and the solidified molten salt 7 is quickly liquefied and hollowed. It is discharged from the heavy curved pipe 1A and returned to the salt bath 12. The liquid molten salt 7 has a thermal conductivity of 0.6 [W / (m · K)] and an air (gas) thermal conductivity of 0.03 [W / (m · K)]. It is about 20 times larger than the above, and the heat transfer to the hollow double-bent pipe 1A is performed well.

For example, a hollow double bent tube 1A of 1000 mm in length filled with a molten salt 7 having a melting point of 140 ° C. (outer tube 2; outer diameter 45 mm, thickness 1.5 mm, inner tube 4; outer diameter 35 mm,
When the molten salt 7 having a thickness of 1.2 mm) is immersed in the liquid molten salt 7 at 180 ° C. in the salt bath 12 and the molten salt 7 is discharged from the hollow double bent tube 1A, the discharging is completed in about 5 minutes. On the other hand, about 50 minutes of heating is required when discharging in a hot air circulation type discharge furnace at 180 ° C. That is, by discharging the molten salt 7 from the hollow double bent tube 1A by immersing it in the liquid molten salt 7, the discharging time can be greatly shortened.

Next, from the salt bath 12 to the hollow double curved pipe 1
A is pulled up and immersed in water stored in a water tank (not shown) (S5). The molten salt 7 is water-soluble, and the molten salt 7 adhering to the hollow double curved pipe 1A is dissolved in water and removed from the hollow double curved pipe 1A. A hollow double curved tube 1A is obtained.

In the method of manufacturing a pipe constructed as described above, the hollow double-bent pipe 1A filled with the solidified molten salt 7 is immersed in the liquid molten salt 7 in the salt bath 12, so that the salt bath The heat of the molten salt 7 in 12 is quickly transferred to the solidified molten salt 7 in the hollow double-bent pipe 1A, and the solidified molten salt 7 is quickly liquefied. Therefore, the molten salt 7 is discharged from the hollow double bent pipe 1A in a short time, and the desired hollow double bent pipe 1A can be quickly obtained, and the cycle time can be shortened. Further, as compared with the hot-air circulation type exhaust furnace used in the prior art, the heat transfer area is reduced, and the energy loss is reduced accordingly, and energy saving can be achieved. Further, since the salt bath 12 is prepared and the molten salt 7 in the liquid state may be stored in the salt bath 12, the apparatus is simplified and space is saved as compared with the hot-air circulation type discharge furnace used in the prior art. And cost reduction of equipment can be achieved.

In the above-described embodiment, the case where the molten salt 7 is filled in the space 3 between the outer pipe 2 and the inner pipe 4 has been described as an example, but the molten salt 7 may be filled in the inner pipe 4. You may comprise.

In the above-described embodiment, a so-called batch type [a plurality of hollow double-bent pipes 1A in a car is used, in which a car (not shown) is used to immerse the hollow double-bent pipe 1A in the liquid molten salt 7. (Work) is placed, and a plurality of hollow double-bent pipes 1A (work) together with the basket are immersed in the molten salt 7 of the salt bath], but instead of this, a hanger is used. Continuous type used [Hangers are attached to a cable (conveyor) at predetermined intervals, hollow double curved pipes 1A are fixed to the respective hangers, and cables are moved to move the hollow double curved pipe 1
A may be sequentially immersed in the molten salt 7 of the salt bath].

In the above embodiment, the case where the straight pipe is the hollow double straight pipe 1 is taken as an example, but the present invention is not limited to this, and it may be a single pipe or a hollow pipe. It may be a multiple tube such as a triple tube.

[0020]

In the invention according to any one of claims 1 to 5, since the bent pipe filled with the solidified molten salt is immersed in the molten molten salt stored in the storing means, The heat of the stored liquid molten salt rapidly solidified the bent tube
Transferred to the molten salt , the solidified molten salt is quickly liquefied. Therefore, the molten salt is discharged from the curved pipe in a short time, a desired curved pipe can be quickly obtained, and the cycle time can be shortened. Further, as compared with the hot-air circulation type exhaust furnace used in the prior art, the heat transfer area is reduced, and the energy loss is reduced accordingly, and energy saving can be achieved. Since it is sufficient to provide a molten salt in a liquid state and a storage means for storing the molten salt , compared to the hot-air circulation type discharge furnace used in the prior art, the apparatus is simplified, space is saved, and the equipment is inexpensive. Can be realized.

According to the fifth aspect of the present invention, the jig body is held by the outer tube, and in this state, the projection of the connecting portion is inserted into the opening of the inner tube. Therefore, the opening side portion of the inner pipe is supported with respect to the outer pipe, and the center line of the outer pipe and the center line of the inner pipe are surely aligned with each other. It does not cause eccentricity of the pipe. Further, since the molten salt is injected into the gap by pouring the molten salt in the liquid state into the gap between the tubular jig body attached to the outer tube and the connecting portion, the jig body serves as a funnel. Therefore, the injection property becomes good.

[Brief description of drawings]

FIG. 1 is a perspective view of a hollow double tube used in an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a jig attached to the hollow double tube of FIG.

3 is a plan view showing the jig of FIG. 2. FIG.

FIG. 4 is a process chart schematically showing the manufacturing method of the pipe according to the embodiment of the present invention.

[Explanation of symbols]

1 hollow double straight pipe 1A hollow double bent tube 2 outer tube 3 void 4 inner tube 7 Molten salt 8 jigs 12 salt bath 13 gap

Claims (5)

(57) [Claims] 1. A step of filling a straight pipe with a molten salt , and
Melt and obtaining a curved pipe by bending the straight pipe in a state of solidifying the molten salt, the curved pipe immersed in the molten salt in the liquid state which is stored in the storage means a molten salt in the curved pipe A method for manufacturing a pipe, which comprises a step of discharging. 2. A method of manufacturing a pipe according to claim 1, wherein
When the molten salt in the liquid state stored in the storage means is opened,
Immerse the curved pipe with the mouth side down and
A pipe characterized by discharging molten salt into the storage means.
Production method. 3. A method for manufacturing a pipe according to claim 1 or 2.
The molten salt filled in the straight pipe is stored in the storage
Characterized in that it is the molten salt in a liquid state stored in the means
The manufacturing method of the pipe. 4. The method according to any one of claims 1 to 3.
In the method for producing a pipe, the molten salt is water-soluble.
A method for manufacturing a pipe, characterized in that 5. The straight pipe is a hollow double pipe in which an inner pipe is inserted with a predetermined gap in the outer pipe, and a jig is provided so as to be attachable to the hollow double pipe. It is composed of a tubular jig body detachably connected to the opening of the pipe, and a connecting portion which is connected to the jig body and has a projection portion at the tip side which is inserted into the opening of the inner pipe. , The inner peripheral side of the opening of the jig body
Is formed into a funnel shape, the jig is attached to the opening side of the hollow double tube, and the molten salt is poured into the cylindrical jig body.
The method for manufacturing a pipe according to claim 1, wherein the molten salt is injected into the void through a gap between the jig body and the connecting portion.