JP2014181733A - Joint structure and joint method for metallic pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint structure capable of easily connecting pipe ends of metallic pipes without having a member for connection therebetween, and capable of reducing the construction time and the construction cost.SOLUTION: After an end of the other pipe is inserted and fitted to an end of one pipe, the outer side pipe and the inner side pipe in an inserted and fitted part are press-bonded by form rolling of the inserted and fitted part from the outer peripheral surface side. In the connected part, the outer side pipe and the inner side pipe preferably have recessed and projected parts, and the connected part preferably has a cross section shape in which the recessed and projected parts of the pipes are fitted with each other. Before being inserted and fitted, it is preferable that diameter reduction work is applied to the pipe end of the inner side pipe or diameter enlargement work is applied to the pipe end of the outer side pipe to be inserted and fitted.

Description

  The present invention relates to a joint structure between metal pipes used for housing equipment and building members, and a joint method thereof.

In general, various metal pipes are used for housing equipment, building members, automobile-related parts, and the like. When such a metal tube becomes long, the metal tubes are often joined and used.
For joining these metal tubes, methods such as welding joining at the pipe end, brazing joining, joining via a joining member such as a flange joint, a quick fastener or the like are employed.
Further, as seen in, for example, Patent Document 1, a method of forming a female screw at one tube end and screwing the other tube end formed with a male screw at the tube end into the one tube end is also employed. Yes.

JP 2002-130554 A

However, in the case of welding joining or brazing joining, not only is the cost high because a heat source is required, but also the joining work takes a long time. In addition, the quality of the metal tube may be deteriorated due to the heat effect. Furthermore, when different types of metals are joined together, there are combinations that are difficult to join depending on the combination of metals. In particular, when a plated metal tube is used as the material, the plating peels off due to the heat effect, so that a partial repair coating is required, which is costly and poor in workability.
If it is going to join with a flange joint, it will be necessary to give flange processing to a pipe end, and subsidiary materials, such as a bolt and a nut, will also be needed, and it will become high cost. The same applies to joining via a joining member such as a quick fastener.

By the way, in the use etc. which were shown at the beginning, as the equipment facilities become more complex and space-saving, the number of joints between the pipes used increases.
For this reason, the conventional joint system not only increases the cost, but also makes it difficult to secure the space. For these reasons, there is an increasing demand for a joining method that can be used in a space-saving manner by reducing the cost by reducing the number of parts used and simplifying the structure.
The present invention has been devised to solve such problems, and when connecting the tube ends of metal tubes, it is possible to easily connect them without using a connecting member. An object of the present invention is to provide a joint structure that can reduce construction time and construction cost.

In order to achieve the object, the metal pipe joint structure of the present invention is a metal pipe joint structure in which the end of one pipe is inserted and fitted to the end of one pipe, and the insertion fitting part However, the outer tube is strongly crimped to the outer side of the inner tube by applying an external force, or has a cross-sectional shape in which the uneven portion of the inner tube is fitted to the uneven portion of the outer tube.
In such a joint structure, after inserting and fitting the end of the other pipe into the end of one pipe, the outer pipe of the insertion fitting portion is formed by rolling from the outer peripheral surface side of the insertion fitting portion. It is obtained by providing an uneven portion on the surface.
Before the insertion fitting, it is preferable to reduce the diameter of the tube end of the inner tube, or to expand the tube end of the outer tube to be inserted and fitted.

  The joint structure of the present invention has a structure in which the end of one tube is inserted and fitted to the end of one tube. Furthermore, in the insertion fitting portion at the tube end, the uneven portion of the outer tube is crimped to the inner tube by rolling, or the uneven portion of the outer tube is transferred to the inner tube so that the fitting shape is formed on both tubes. As a result, the bonding strength is increased. Concave and convex portions are formed only on the outer tube, and even if the inner tube is in the shape of a raw tube, the frictional force due to the crimping of both tubes is improved, enabling bonding with excellent pressure resistance and tensile properties. Yes. The bonding strength can be improved by changing the number of the uneven portions, the groove shape, the groove depth, and the groove pitch at this time. At the same time, the inner tube and the outer tube of the fitting portion subjected to the rolling process are in close contact with each other, and both the tubular bodies are fixed at the concavo-convex portion, so that the fluid flows in the tube. However, the fluid is prevented from leaking.

The figure explaining the non-seal type mechanical joining method of this invention The figure explaining the connection structure using an auxiliary sleeve The figure explaining the mechanical joining method of the sealing agent type of a comparative example The figure explaining the O-ring type mechanical joining method of a comparative example The figure which shows the joining strength when joining a stainless steel pipe and a copper pipe by the method of the present invention The figure which shows pressure resistance when joining a stainless steel pipe and a copper pipe by the method of the present invention

As described above, in the joint structure in which the flange portion is formed in advance at the pipe end and the flange portions are brought into contact with each other to fix the flange portion, it takes time to form the flange portion, and also the flange portion is fixed. The use of secondary materials becomes necessary, resulting in high costs. Also, joining via a joining member such as a quick fastener requires a secondary material with a shaped shape, resulting in high costs.
Therefore, the present inventors, when connecting the pipe ends of the metal pipe, it is possible to simply connect without a connection member, and relates to a joint structure that can reduce the construction time and construction cost, The present invention has been reached through repeated studies.

The metal pipe joint method according to the present invention will be described below.
Prepare two metal tubes to be connected. Assuming subsequent use, those having the same diameter are preferred. In order to facilitate the insertion, it is preferable to perform a pipe expanding process on the end portion of the metal pipe which is the outer side (see FIG. 1A). A diameter reduction process may be applied to the end of the inner metal tube. Then, the pipe end of the other metal pipe is inserted into one metal pipe pipe end (FIG. 1B). Then, as shown in FIG.1 (c), a joint structure is constructed | assembled by giving an uneven | corrugated | grooved part by machining an insertion fitting part from the outer peripheral surface side.

As a method for forming a mechanical uneven portion from the outer peripheral surface side, there is a rolling method using the plastic deformation of the pipe by simultaneously rotating the roll around the pipe and reducing the revolution diameter of the roll. It is done. In this processing method, grooving can be performed by rounding the tip of the roll to be used.
By forming the uneven portion, the inner peripheral surface of the outer metal tube is pressure-bonded to the outer peripheral surface of the inner metal tube, or the uneven shape of the outer metal tube is transferred to the inner metal tube and fitted in the uneven portion. Thus, a joint structure in which both metal pipes are firmly joined is obtained. In addition, since the rolling parts of the metal pipes are in close contact with each other, the insertion fitting part also has a sealing effect, and even in a usage mode in which a fluid is disposed inside the metal pipes. , There is little risk of leakage of internal fluid.

In addition, by adjusting the fitting allowance or adjusting the number of grooves, the groove shape, the groove depth, the pitch, etc., not only the bonding strength is increased, but a pressure-resistant connection body corresponding to the used internal pressure can be obtained.
There is no limitation on the types of metal pipes connected to each other. A steel pipe may be sufficient and a copper pipe and an aluminum pipe may be sufficient. The same kind of metal pipes may be connected, or metal pipes of different types may be connected.

In the previous stage, in order to facilitate insertion, it was described that it is preferable to perform pipe expansion processing on the end of the outer metal tube or to reduce diameter processing on the end of the inner metal tube. Alternatively, a sleeve may be used.
That is, as shown in FIG. 2, when connecting metal pipes having the same diameter, a short length having an inner diameter equal to or greater than the outer diameter of the metal pipe to be connected or having an outer diameter equal to or smaller than the inner diameter of the metal pipe to be connected. The cylindrical tube is prepared, and the ends of the metal tube to be connected to both ends of the cylindrical tube are fitted. Subsequently, the metal tubes can be joined to each other through the cylindrical tube of the insertion fitting portion by rolling from the outer peripheral surface side of the insertion fitting portion.
If such an aspect is employ | adopted, the prior | preceding processes, such as a pipe expansion process or a contraction process, will be unnecessary for either pipe | tube of an inner side outer side, and it will become possible to connect metal pipes simply also at a construction site.

Material used;
The materials are φ12.7 × 0.6t copper tube (C1220 phosphorous deoxidized copper O material, Hv50) and φ12.7 × 0.4t ferritic stainless steel tube (22Cr-0.2Ti-0.2Nb-1Mo Hv170). Used, the dissimilar metals of a copper pipe and a stainless steel pipe were joined.
Moreover, the anti-corrosion sealant Hermeseal 55 manufactured by Nippon Helmetics Co., Ltd., or a nitrile rubber-based O-ring manufactured by Akitsu Industry Co., Ltd. was used for sealing the gap between both pipes.

Manufacturing example: 1 (Non-seal type)
A tube-expansion punch was inserted into the tube end of the outer tube, and tube expansion was performed to an inner diameter φ12.9 mm × length L30 mm slightly larger than the outer diameter of the inner tube. The expansion was performed in two modes: the case where the tube was expanded outside and the tube was a copper tube and the case where it was a stainless steel tube. In the non-seal type, the pipe end of the pipe that is disposed inside is inserted into the pipe end of the outer pipe that has been subjected to pipe expansion processing. Thereafter, a roll with R having a rounded tip (tip R = 1 mm) was rotated around the pipe, and at the same time, the revolution diameter of the roll was reduced to perform rolling on the outer pipe (FIG. 1). The number of grooves was 3, the groove pitch was 7 mm, and the groove depth was varied from 0 to 1.2 mm.

Production example: 2 (auxiliary sleeve type)
When the auxiliary sleeve was arranged outside, an auxiliary sleeve of φ13.6 × 0.4t × L65 having an inner diameter slightly larger than the outer diameter of the copper tube and the stainless steel tube was used. On the other hand, when the auxiliary sleeve is disposed inside, an auxiliary sleeve of φ11.4 × 0.4 t × L65 whose outer diameter is slightly smaller than the inner diameter of the copper tube was used. Ferritic stainless steel pipe (22Cr-0.2Ti-0.2Nb-1Mo Hv170) was used for the auxiliary sleeve. A copper tube and a stainless steel tube are placed 30 mm from both ends of the auxiliary sleeve, and a roll with an R with a rounded tip (tip R = 1 mm) is rotated around the tube and at the same time the roll revolution diameter is reduced. Fabrication was performed (FIG. 2). The number of grooves was three on each of the copper tube side and the stainless steel tube side, the groove pitch was 7 mm, and the groove depth was 1.2 mm.

Production example: 3 (sealing agent type)
A tube-expansion punch was inserted into the tube end of the outer tube, and tube expansion was performed to an inner diameter φ12.9 mm × length L30 mm slightly larger than the outer diameter of the inner tube. The expansion was performed in two modes: the case where the tube was expanded outside and the tube was a copper tube and the case where it was a stainless steel tube. In the sealing agent type, a hermetic seal 55 as a sealing agent is applied to the tube end L30 mm of the tube to be arranged on the inner side, and is inserted into the tube end of the outer tube subjected to the tube expansion process. Thereafter, a roll with an R having a rounded tip (tip R = 1 mm) was rotated around the pipe and the revolution diameter of the roll was simultaneously reduced, thereby rolling the outer pipe (FIG. 3). The number of grooves was 3, the groove pitch was 7 mm, and the groove depth was varied from 0 to 1.2 mm.

Manufacturing example: 4 (O-ring type)
A tube-expansion punch was inserted into the tube end of the outer tube, and tube expansion was performed to an inner diameter φ12.9 mm × length L30 mm slightly larger than the outer diameter of the inner tube. Also, the outer peripheral surface of the inner pipe is rolled at a position 7 mm from the pipe end, and the groove depth 0.35 so that the diameter of the groove bottom is φ12.0 mm so as to meet the O-ring inner diameter reference value. A single groove of mm was formed, and an O-ring was fitted into this groove. The expansion was performed in two modes: the case where the tube was expanded outside and the tube was a copper tube and the case where it was a stainless steel tube. After that, the inner tube with the O-ring fitted is inserted into the expanded tube section of the outer tube, and the roll with R with rounded tip (tip R = 1mm) is rotated around the tube and at the same time the roll revolves. By reducing the diameter, the outer tube was rolled for bonding (FIG. 4). The number of grooves was one, the position of the grooves was 10 mm from the pipe end arranged outside, and the groove depth was 1.0 mm.

Evaluation 1;
The joint strength was evaluated as an evaluation test of each joint joint produced. The test method was to use a universal testing machine to grip the outer and inner pipe ends with a hydraulic chuck, pull at a speed of 10 mm / min, and measure the maximum load until disconnection or breakage.
In order to prevent deformation of the tube end portion of the raw tube due to chucking, an inner die of φ11.5 × L50 was inserted only into the portion restrained by the hydraulic chuck. The tensile strength of the copper tube itself is 4.9 kN, and the tensile strength of the stainless steel tube itself is 8.2 kN.
As shown in FIG. 5, the bonding strength when the stainless steel pipe is arranged outside is higher in the non-seal type than in the sealing agent type, and is about 60 to 80% of the copper pipe itself with a constant groove depth. is there. However, when the copper pipe is arranged outside, the bonding strength is about 30% of the copper pipe. The joining strength of the auxiliary sleeve type is about 80% of that of the copper tube when the auxiliary sleeve is arranged outside. In addition, when the auxiliary sleeve is arranged on the inner side, it is about 30% of the copper pipe. Regardless of the inner / outer arrangement of the auxiliary sleeve, the copper sleeve was broken at the joint. On the other hand, since the O-ring type has one bonding groove, the bonding strength is about 30 to 40% of the copper tube.

Evaluation 2;
The pressure resistance was evaluated as an evaluation test of each prototype joint. The test method was to seal one tube end, pressurize with a hydraulic pump from the other tube end, and when there was no rupture or leakage when held for 1 minute, increase the pressure by 1MPa and measure the maximum pressure resistance . The pressure resistance of the copper tube itself is 20 MPa, and the pressure resistance of the stainless steel tube itself is 45 MPa.
As shown in FIG. 6, the non-seal type, sealing agent type, and auxiliary sleeve type have a constant groove depth, and the O-ring type has a groove bottom diameter of φ12 so as to meet the O-ring inner diameter reference value. By forming a single groove with a groove depth of 0.35mm to be 0mm and fitting an O-ring into this groove, the copper tube will rupture without leaking from the joint. There is enough pressure resistance.

Evaluation 3;
Corrosion resistance was evaluated as an evaluation test for each joint joint produced. In the test method, 80 ° C. test water containing 2000 ppm of chlorine ions and 2 ppm of copper ions was allowed to flow inside the tube for 30 days.
After the test, the joint part was split in half to remove rust. Thereafter, the corrosion state of the surface where the stainless steel tube and the copper tube were in contact and the inner surface of the inner tube which was in contact with the test water was observed. As a result, crevice corrosion was not recognized in the stainless steel tube. Moreover, although slight corrosion was observed on the inner surface of the pipe, it was confirmed that the corrosion resistance was not a problem and that it could be sufficiently used for fluid flow.

Claims (7)

  A metal pipe joint structure in which the end of the other pipe is inserted and fitted to the end of one pipe, and the insertion fitting is a structure in which the outer pipe is crimped to the inner pipe by applying external force Construction.   A joint structure of a metal tube in which the end of one tube is inserted and fitted to the end of one tube, and the insertion fitting is fitted between the uneven portion of the outer tube and the uneven portion of the inner tube by applying external force. The metal pipe joint structure according to claim 1, wherein the metal pipe joint structure has a combined cross-sectional shape.   After inserting and fitting the end of the other tube into the end of one tube, the uneven portion is formed across the inner tube and the outer tube of the insertion fitting portion by rolling from the outer peripheral surface side of the insertion fitting portion. A method for jointing metal pipes, characterized by comprising:   The metal pipe joint method according to claim 3, wherein a diameter reduction process is performed on a pipe end of an inner pipe before insertion fitting.   The metal pipe jointing method according to claim 3 or 4, wherein a pipe expansion process is performed on a pipe end into which an outer pipe is inserted and fitted before insertion and fitting.   When joining metal pipes of the same diameter, a sleeve having an inner diameter equal to or greater than the outer diameter of the metal pipe to be joined or having an outer diameter equal to or less than the inner diameter of the metal pipe to be joined is used as an auxiliary material. A metal pipe jointing method, wherein an uneven portion is provided on the outer tube of the insertion fitting portion by rolling from the outer peripheral surface side of the insertion fitting portion of the sleeve.   A joint structure of a metal tube in which an end portion of the other tube is inserted and fitted to an end portion of one tube via a sleeve, and the insertion fitting portion is connected to the uneven portion of the outer tube and the inner tube by applying external force. The metal pipe joint structure according to claim 6, wherein the metal pipe joint structure has a cross-sectional shape fitted at the uneven portion.

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