JP3822199B2 - Joint structure of dissimilar metal pipes - Google Patents

Description

  The present invention relates to a joining technique for dissimilar metal pipes, and more particularly to a joining technique for aluminum alloy piping and stainless steel vibration absorbing pipes used in a refrigerant circuit of an automobile air conditioner.

  In recent years, aluminum alloy pipes have been used for the refrigerant circuit pipes of automobile air conditioners for the purpose of reducing the weight of the vehicle body, but vibrations generated by a compressor or the like may resonate the pipes and cause noise. Therefore, in order to suppress the resonance of the pipe, conventionally, a composite hose made of rubber and resin has been used in the middle of the pipe.

By the way, HFC134a is frequently used as a refrigerant for air conditioners for automobiles in place of Freon, which is a depleting substance of the ozone layer. However, this HFC134a has an ozone depletion coefficient of zero, but has a high global warming potential and is becoming a cause of promotion of global warming. For this reason, it is being recommended to use a CO ₂ refrigerant, which is a natural refrigerant having a low global warming potential, as a substitute for HFC134a.

However, when CO ₂ refrigerant is used, the fluid temperature in the refrigerant circuit piping is 170 to 180 ° C. with respect to 120 to 140 ° C. of the HFC 134a refrigerant, and the pressure is 15 to 20 MPa with respect to 2 to 3 MPa of the HFC 134a refrigerant. .

For this reason, a conventional composite hose made of rubber and resin cannot withstand such a high temperature and high pressure specification, and a vibration absorbing tube having a stainless steel bellows has been proposed instead (for example, a patent) Reference 1). In addition, this stainless steel vibration absorption tube has a gas permeability that is far superior to a conventional composite hose made of rubber and resin because the tube wall is made of metal. There is no leakage. Therefore, this stainless steel vibration absorption tube is being used not only for CO ₂ refrigerant but also for the current HFC134a refrigerant and the like in order to bring the amount of leakage of the refrigerant to the outside air close to zero.

 However, there are the following problems when incorporating the vibration absorbing tube into the refrigerant circuit. In other words, stainless steel is currently used for the bellows portion of the vibration absorbing tube from the viewpoint of workability, strength, corrosion resistance, and economy. On the other hand, if the refrigerant circuit piping is changed to stainless steel, equipment such as a compressor to which the piping is connected is made of an aluminum alloy, so that connection with these devices becomes difficult, and the weight of the vehicle body is reduced. Since it hinders and increases the cost, it is desirable to use the current aluminum alloy. Therefore, it is necessary to join a stainless steel vibration absorbing pipe and an aluminum alloy pipe. However, it is very difficult to obtain a reliable joint having high strength and high airtightness by simply mechanically fitting or screwing these metal pipes together. In addition, when an aluminum alloy and stainless steel are joined by welding or brazing, a brittle intermetallic compound is likely to be formed at the joint. In this case as well, a reliable joint having high strength and high airtightness is obtained. It is very difficult.

 As a method of joining the iron-based material and aluminum, after roughing the surface of the base material made of the iron-based material to form irregularities, an aluminum layer is temporarily formed, and this aluminum layer is pressed from the surface side. However, a method of forming a diffusion layer made of an Fe-Al intermetallic compound by high-frequency heating has been disclosed (see Patent Document 2).

 However, this method is intended to improve the wear resistance and smoothness of the surface of the base material by forming a diffusion layer made of an intermetallic compound, and is reliable as long as an intermetallic compound is formed. A joint having a certain high strength and high airtightness cannot be obtained.

In the above description, only the joining of the Fe-based material and the Al-based material has been described. However, a brittle intermetallic compound is easily generated even in the case of the joining of the Fe-based material and the Ti-based material, or the Fe-based material and the Cu-based material. Therefore, there are similar problems. For this reason, the development of a highly reliable joining technique that can reliably join dissimilar metal tubes has been desired.
JP 2002-195474 A JP 7-310161 A

 This invention is made | formed in view of this condition, Comprising: It aims at providing the joining structure of the reliable dissimilar metal tube excellent in intensity | strength and airtightness.

The invention according to claim 1 is a joining structure of two dissimilar metal tubes each made of an Fe-based material and an Al-based material , and these dissimilar metal tubes are formed of a double-layer metal clad plate. The two types of dissimilar metal materials that are joined via a metal fitting and constitute the two-layer metal clad plate are the same material as the two dissimilar metal tubes, respectively , and constitute the two-layer metal clad plate. The Fe-based material has a thickness of 15 to 35% of the total thickness of the two-layer metal clad plate, and the connection fitting is a tube whose tip is opened by performing hole flange processing on the two-layer metal clad plate. The raised parts are formed in a flange shape, and the raised part has a raised height of 1.0 times or more of the inner diameter of the raised parts, and the two dissimilar metals Pipe the outer peripheral surface side and the inner periphery of the raised part It is divided into the surface side, and is inserted and inserted so that the metals of the same kind are in contact with each other, and only the part where the metals of the same kind are in contact with each other is joined by welding or brazing. It is the joining structure of different metal pipes.

 According to a second aspect of the present invention, after the connecting metal fitting is formed with a cylindrical rising portion having a tip opened by subjecting the double-layer metal clad plate to hole flange processing, the vicinity of the root of the rising portion is formed. 2. The dissimilar metal tube joining structure according to claim 1, wherein the dissimilar metal tube is formed into a cylindrical shape by cutting.

  The invention according to claim 3 is the joining structure of dissimilar metal pipes according to claim 1 or 2, wherein the hole flange processing is one in which the tip portion is opened after deep drawing of the double-layer metal clad plate. It is.

  According to a fourth aspect of the present invention, in the hole flange processing, after the deep drawing of the double-layered metal clad plate, a pilot hole is opened at the tip, and thereafter burring is performed. It is the joining structure of the dissimilar metal pipe described in 1.

 The invention according to claim 5 is the dissimilar metal tube joining structure according to claim 1, wherein the hole flange processing is to perform burring after a pilot hole is previously formed in the double-layer metal clad plate. .

Since the present invention is configured as described above, by using a double-layer metal clad plate as a material for the connection fitting, the dissimilar metals are physically firmly joined by the clad, and only between the same kind of metals. Therefore, it is possible to provide a highly reliable dissimilar metal pipe joint structure excellent in strength and airtightness while suppressing the formation of brittle intermetallic compounds. In addition, the provision of a highly reliable stainless steel pipe and aluminum alloy pipe with excellent strength and airtightness makes it possible to use a CO ₂ refrigerant in an automotive air conditioner. It has become possible to achieve both a reduction in load and a reduction in weight of the vehicle body.

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment 1]
FIG. 1 shows a joining structure of dissimilar metal tubes according to an embodiment of the present invention. In the figure, reference numerals 1 and 2 denote stainless steel pipes and aluminum alloy pipes as different metal pipes, respectively, and reference numeral 3 denotes a connection fitting.

 As a hole flange process for forming the connection fitting 3, an example using a burring process will be described first. The connection fitting 3 is formed as follows, for example. A double-layer metal clad plate made of stainless steel and an aluminum alloy (hereinafter also simply referred to as “clad plate”) is formed into a cut plate or slitter coil cut out to an appropriate size, and a pilot hole is previously formed in the cut plate or slitter coil. Is opened, and then a burring process is performed to form a cylindrical rising portion 4 having an open end. Then, by punching the outer peripheral portion into a circular shape by blanking or the like, the flange-shaped connecting fitting 3 having the rising portion 4 and the outer peripheral portion including the annular flange portion 5 can be formed. In this example, burring is performed so that the outer peripheral surface side 4a of the raised portion 4 is stainless steel and the inner peripheral surface side 4b is an aluminum alloy.

 Then, the stainless steel pipe 1 and the aluminum alloy pipe 2 which are different metal pipes are divided into the outer peripheral surface side 4a and the inner peripheral surface side 4b of the rising portion 4 of the connection fitting 3, respectively, so that metals of the same kind are in contact with each other. Insert to fit. Specifically, first, the rising portion 4 of the connection fitting 3 is inserted into the stainless steel pipe 1 from the side without the flange 5 to the back, and then the aluminum alloy is inserted into the rising portion 4 of the connection fitting 3 from the flange portion 5 side. Insert tube 2. Thereby, the inner surface of the stainless steel tube 1 is in contact with the stainless steel on the outer peripheral surface side 4a of the rising portion 4, and the outer surface of the aluminum alloy tube 2 is in contact with the aluminum alloy on the inner peripheral surface side 4b of the rising portion 4. Become.

 Thereafter, only the portions where the metals of the same kind are in contact with each other are joined by welding or brazing.

 For example, the inner surface of the stainless steel pipe 1 and the outer peripheral surface side 4 a of the rising portion 4 can be joined by laser welding the entire circumference from the outer surface side of the stainless steel pipe 1. In the laser welding, the entire thickness of the stainless steel pipe 1 of the welded portion 9 is melted from the outer surface of the stainless steel pipe 1, and a part of the stainless steel on the outer peripheral surface side 4a of the rising portion 4 is also melted. It is desirable to carry out instantaneously and locally under various conditions. Thereby, since the stainless steel pipe 1 and the stainless steel on the outer peripheral surface side 4a of the rising portion 4 can be melt-bonded while suppressing the formation of intermetallic compounds, a strong bond is obtained. Further, by laser welding the entire circumference of the stainless steel pipe 1, there is no gap between the inner surface of the stainless steel pipe 1 and the outer peripheral surface side 4 a of the rising portion 4, and sealing performance (airtightness) can be ensured. Since the laser welding heat can be instantaneously and locally input and is quickly dissipated through the aluminum alloy having excellent thermal conductivity on the inner peripheral surface side 4b of the rising portion 4, the stainless steel 4a and the aluminum alloy 4b There is no possibility that an intermetallic compound is formed on the contact surface. However, if the depth of laser welding is too deep, the aluminum alloy may be affected by heat and the material may be deteriorated. Therefore, it is desirable to adjust appropriately within a range in which the joining strength between stainless steels can be sufficiently obtained. .

 In addition, the joining of the outer surface of the aluminum alloy tube 2 and the aluminum alloy on the inner peripheral surface side 4b of the rising portion 4 is performed, for example, by laser welding the whole circumference of the base portion 5a of the flange portion 5 at a high temperature in a short time. Or by brazing at a relatively low temperature. Thereby, the outer surface of the aluminum alloy tube 2 and the aluminum alloy on the inner peripheral surface side 4b of the rising portion 4 can be firmly joined while suppressing the formation of intermetallic compounds and ensuring the sealing property.

  In the above example, the two-layer metal clad plate constituting the connection fitting 3 is made of the same stainless steel and aluminum alloy as the material of the dissimilar metal tube, but is not necessarily limited to the same material as the dissimilar metal tube. It may be of the material. Here, the same kind of material as the dissimilar metal tube means that the base metal component is the same as that of the dissimilar metal tube, and even if it is welded or brazed to the dissimilar metal tube, a brittle intermetallic compound is not formed or formed. It is a trace amount that has virtually no effect. The metal component used as a base here is Fe in the case of stainless steel, and Al in the case of an aluminum alloy.

 Therefore, in the above example, the stainless steel constituting the clad plate may be made of a material (steel type) different from the stainless steel pipe (for example, when the stainless steel pipe is SUS304, the clad plate stainless steel is SUS430). Ordinary steel can be used instead of steel, and can be appropriately selected in consideration of workability by burring, weldability (brazing property), strength, and the like.

  Further, the aluminum alloy constituting the clad plate may be made of a material different from that of the aluminum alloy tube (for example, when the aluminum alloy tube is A5052, the aluminum alloy of the clad plate is A1100). Aluminum can also be used and can be appropriately selected in consideration of workability by burring, weldability (brazing property), strength, and the like.

 The overall thickness of the clad plate is preferably thin so as not to make the joint portion excessively large. However, it is desirable that the clad plate is appropriately adjusted in consideration of workability by burring, weldability (brazing property), strength, and the like.

 Also, the ratio of the thicknesses of the dissimilar metals constituting the clad plate can be appropriately adjusted in consideration of workability by burring, weldability (brazing property), strength, and the like. In addition, when the combination of the dissimilar metals is a combination of the Fe-based material and the Al-based material as in the first embodiment, the thickness of the Fe-based material constituting the double-layer metal clad plate is the same as the double-layer metal. It is preferable to be 15 to 35% of the total thickness of the clad plate. If it exceeds 35%, the proportion of the Al-based material that is excellent in workability is too small, and there is a possibility that the rising height of the rising portion 4 cannot be secured sufficiently during burring (or deep drawing processing described later). On the other hand, if it is less than 15%, the proportion of Fe-based material is too small, and the Fe-based material of the raised portion 4 may be thinned and cut during burring (or deep drawing described later).

 The inner diameter of the raised portion 4 formed by burring is slightly larger than the outer diameter of the aluminum alloy tube 2 so that the aluminum alloy tube 2 can be easily inserted, but the gap is not opened too much. In addition, when inserting the insert material 7 of after-mentioned Embodiment 3 in between, a little clearance gap is opened.

The rising height of the rising portion 4 is such that heat input during welding or brazing is dissipated to suppress the generation of intermetallic compounds, and each of the tubes when the stainless steel pipe 1 and the aluminum alloy pipe 2 are inserted. It is desirable that the contact area is sufficiently high with respect to 1 and 2, and the height is such that welding (or brazing) is easy. That is, depending on the pipe diameters of the pipes 1 and 2 to be connected, for example, when used in a CO ₂ refrigerant circuit of an automobile air conditioner, the pipe diameters of the pipes 1 and 2 are as small as several millimeters to 10 mm. The rising height of the portion 4 is preferably 1.0 times or more of the inner diameter of the rising portion 4 and more preferably 2.0 times or more.

 For burring, generally, a rising part is provided on the plate material and screwed there to use it as a stop screw, or a rising part is provided on the side wall of the main pipe and a branch pipe is brazed there to be used as a branch pipe It is used for the purpose of doing. For this reason, it is not necessary to make the rising height of the rising portion so high, and burring is usually performed at room temperature (cold). However, as described above, when it is necessary to increase the rising height of the rising portion 4 to 1.0 times or more of the inner diameter of the rising portion 4, depending on the material, processing may be difficult in the cold state. In such a case, the clad plate may be preheated before burring.

 In the above example (FIG. 1), the burring of the clad plate was performed such that the outer peripheral surface side 4a of the raised portion 4 was stainless steel and the inner peripheral surface side 4b was an aluminum alloy. Alternatively, the outer peripheral surface side 4a of the rising portion 4 may be an aluminum alloy and the inner peripheral surface side 4b may be stainless steel. Note that the aluminum alloy having the inner peripheral side 4b as in the above example (FIG. 1) improves the formability because the aluminum alloy exhibits a lubricating function when plastically deformed by burring, so that the start-up portion 4 is improved. Therefore, it is more preferable since a smooth processed surface can be obtained without causing problems such as processing flaws and the rising height of the rising portion 4 can be increased.

(Modification)
In addition, in the said Embodiment 1, although the connection metal fitting 3 was made into the flange shape, you may form in a cylinder shape by cut | disconnecting the base vicinity of the raising part 4 (refer FIG. 2). When the connection fitting 3 has a flange shape, the formation of an intermetallic compound can be more reliably prevented by the heat radiation effect of the flange portion 2a when the connection fitting 3 and the metal tube 1 or 2 are welded or brazed. On the other hand, when the connection fitting 3 is cylindrical, the heat dissipation effect is inferior, but there is no protrusion of the flange portion 2a. For example, when used in a CO ₂ refrigerant circuit of an automobile air conditioner, the engine room and the like are limited. There is an advantage that the degree of freedom of piping layout in the space is increased.

 Further, the joining of the inner surface of the stainless steel pipe 1 and the outer peripheral surface side 4a of the rising portion 4 is performed by laser welding the entire circumference from the outer surface side of the stainless steel pipe 1 (see FIG. 1), instead of FIG. As shown, the end of the stainless steel pipe 1 may be welded by fillet welding by laser welding.

[Embodiment 2]
As a method of joining the inner surface of the stainless steel pipe 1 and the outer peripheral surface side 4a of the raised portion 4, in the first embodiment (FIG. 1), a method of laser welding the entire circumference from the outer surface side of the stainless steel pipe 1 is adopted. Instead, as shown in FIG. 3, an insert material 6 is inserted between the inner surface of the stainless steel pipe 1 and the outer peripheral surface side 4a of the raised portion 4, and the insert material 6 is melted by high-frequency heating or the like. You may attach

 Further, as a method of joining the outer surface of the aluminum alloy tube 2 and the aluminum alloy on the inner peripheral surface side 4b of the rising portion 4, in the first embodiment (FIG. 1), the entire circumference of the base portion 5a of the flange portion 5 is brazed. However, instead of this, as shown in FIG. 3, the insert material 7 is placed between the outer surface of the aluminum alloy tube 2 and the inner peripheral surface side 4b of the rising portion 4 as in the case of the stainless steel. The insert material 7 may be melted and brazed by high frequency heating.

[Embodiment 3]
Or as shown in FIG. 4, you may insert the aluminum alloy ring 8 in the upper surface side, ie, the aluminum alloy side 5b, of the flange part 5, and braze aluminum alloys (2, 5b, 8). Of course, the ring 8 is not necessarily made of the same material as the material of the inner peripheral surface 4b of the aluminum alloy tube 2 or the connection fitting 3, and the same type or pure Al material may be used.

[Embodiment 4]
In the first to third embodiments, the case where burring processing is used as hole flange processing of a double-layer metal clad plate has been described, but the present invention is not limited to this, and for example, deep drawing processing is used instead of burring processing. It may be used. In the burring process, the raised portion 4 is formed by a single plastic deformation. Therefore, when the clad plate is made of a difficult-to-work material, it is difficult to set the raised height of the raised portion 4 to a required height. There are cases. On the other hand, when the raised portion 4 is formed by deep drawing, plastic deformation can be applied little by little in a plurality of times. You can get it. Of course, the deep drawing may be processed after pre-heating the clad plate. In the deep drawing process, since the processing is performed without previously preparing the pilot hole, the tip end portion is opened after the processing.

[Embodiment 5]
Or it is also preferable to use the processing method which combined deep drawing processing and burring processing as hole flange processing. For example, after deep-drawing a double-layer metal clad plate, a pilot hole is opened at the tip, and then burring is performed to ensure the rising height of the rising portion 4 and to change the tip shape of the opening. Smooth finish.

[Embodiment 6]
Further, as shown in FIG. 5, a step is provided in a portion into which the connection fitting 3 is inserted in the inner surface of the stainless steel tube 1, and the aluminum alloy tube 2 is inserted so as to be in direct contact with the inner surface of the stainless steel tube 1. preferable. As a result, the brazing material and the insert material used for joining the outer surface of the aluminum alloy tube 2 and the aluminum alloy on the inner peripheral surface side 4b of the rising portion 4 can be more reliably prevented from entering the tube and contaminating the refrigerant. it can.

[Embodiment 7]
In Embodiments 1 to 6 described above as the connection fitting 3, the method of using a hole formed by subjecting the clad plate to hole flange processing has been described. Instead of this, as shown in FIG. You may use what gave the hole process and formed in the ring shape. However, it is necessary to flange each end portion on the side where the different metal pipes 1 and 2 are connected. And these flange parts 1a and 1b are faced | matched so that the metal of the same kind material may contact through the ring-shaped connection metal fitting 3. FIG. That is, the flange portion 1a of the stainless steel pipe 1 and the stainless steel side 3a of the connection fitting 3 are brought into surface contact, and the flange portion 2a of the aluminum alloy tube 2 and the aluminum alloy side 3b of the connection fitting 3 are brought into surface contact. Thereafter, only the portions where the metals of the same type are in contact with each other are joined by welding or brazing. For example, as shown in FIG. 6, the outer diameter of the connection fitting 3 is made slightly larger than the outer diameters of the flange portions 2a and 2b, and the entire circumferences of the outer peripheral portions 1b and 2b of the flange portions 1a and 2a are brazed. That's fine. Thereby, the dissimilar metal pipes 1 and 2 can be firmly joined while ensuring sealing properties without generating an intermetallic compound.

 When a clad plate made of different metals such as stainless steel and aluminum alloy is used, there is a concern that electrocorrosion may occur between different metals due to the presence of rainwater or the like. Therefore, if necessary, the end face of the clad plate where the interface of the different metal is exposed may be covered with, for example, a resin.

  In the above example, only the combination of the stainless steel pipe and the aluminum alloy pipe has been described as the dissimilar metal pipe, but the present invention is not limited to this combination of materials, and any combination of materials that are likely to generate brittle intermetallic compounds. It can be applied to any combination. For example, a combination of Fe-based material and Al-based material, a combination of Fe-based material and Ti-based material, a combination of Fe-based material and Cu-based material, a combination of Al-based material and Cu-based material, or an Al-based material It can also be applied to combinations of Ti and Ti-based materials. As the Fe-based material, normal steel may be used in addition to the stainless steel of the first to fifth embodiments. In addition to the aluminum alloys of the first to fifth embodiments, the aluminum material may be pure aluminum. Even in the case of Ti-based materials and Cu-based materials, either pure metals or alloys may be used in the same manner as Al-based materials.

(Molding of connecting metal)
As a material for the connection fitting, a double-layer metal clad plate having a total thickness of 1.7 mm made of 0.5 mm thick stainless steel (SUS430 series) and a 1.2 mm thick aluminum alloy (A1100) was used. The two-layer metal clad plate was subjected to deep drawing in six steps so that the inner surface was made of an aluminum alloy, and then punched the tip with a punch, an inner diameter of 7 mm, and a rising height. A rising portion of 15 mm was formed. And the outer peripheral part of this starting part was punched out circularly by blanking, and the flange-shaped connection metal fitting was formed. FIG. 7 shows details of (a) a longitudinal section, (b) a transverse section in the vicinity of the center of the length, and (c) a vicinity of an interface between different metals in this transverse section. Although the thickness of the clad plate was reduced to about 1.5 mm by multiple deep drawing processes, as shown in FIG. 7, no delamination was observed at the interface between the stainless steel and the aluminum alloy constituting the clad plate. (Note that the black line at the boundary between the stainless steel and the aluminum alloy in FIG. 7A is a step formed on the boundary surface when the sample is polished).

(Join the connection fitting and stainless steel pipe)
After inserting a stainless steel pipe (SUS304, wall thickness 1.0 mm) on the outer peripheral surface side of the connection fitting (without inserting an aluminum alloy pipe on the inner peripheral surface side), it is rotated around the tube axis. The entire circumference was laser welded by irradiating the laser from the outer surface of the stainless steel pipe with a carbon dioxide laser welding machine (rated: 1 kW) (see FIG. 1). FIG. 8 is a cross-sectional view showing the state in the vicinity of the interface between the stainless steel and the aluminum alloy constituting the clad material after laser welding, where (a) is the root of the flange, (b) is the weld, ) Shows the structure in the vicinity of the interface at a position 5 mm away from the welded portion in the direction opposite to the flange portion. As shown in (b) and (c), it was observed that a very small amount of intermetallic compound (black portion) having a thickness of about several μm was formed at the interface. On the other hand, as shown to (a), the production | generation of the intermetallic compound was not seen by the heat dissipation effect in the flange part vicinity. Thus, even if there is a part where a small amount of the intermetallic compound is generated, the required strength of the component may be maintained at a part where the intermetallic compound is not generated. In this example, since laser welding was performed without inserting an aluminum alloy tube on the inner peripheral surface side of the connection fitting, a small amount of intermetallic compound was produced in the welded portion as described above. If the above laser welding is performed after fitting or brazing the aluminum alloy tube to the inner peripheral surface side of the connection fitting, the amount of intermetallic compound produced is further reduced due to the heat dissipation effect of the aluminum alloy tube. It is considered a thing.

(Junction of connection fitting and aluminum alloy pipe)
After fitting an aluminum alloy tube (A1070, wall thickness 1.5 mm) on the inner peripheral surface side of the connecting fitting (without inserting a stainless steel tube on the outer peripheral surface side), the base of the flange portion of the connecting fitting The entire circumference was brazed (see FIG. 1). An Al—Si brazing material (Alu 19FCW-Cs50 [manufactured by Nice Co., Ltd., trade name)) was used as the brazing material, and an oxygen-acetylene burner was used as the heat source for brazing. FIG. 9 is a cross-sectional view showing a state in the vicinity of the interface between the stainless steel and the aluminum alloy constituting the clad material in the vicinity of the brazed portion after brazing. As shown in the figure, no intermetallic compound was formed at the interface.

It is a longitudinal cross-sectional view which shows the joining structure of the stainless steel pipe and aluminum alloy pipe which concern on Embodiment 1. It is a longitudinal cross-sectional view which shows the joining structure of the stainless steel pipe and aluminum alloy pipe which concern on the modification of Embodiment 1. It is a longitudinal cross-sectional view which shows the joining structure of the stainless steel pipe and aluminum alloy pipe which concern on Embodiment 2. It is a longitudinal cross-sectional view which shows the joining structure of the stainless steel pipe and aluminum alloy pipe which concern on Embodiment 3. It is a longitudinal cross-sectional view which shows the joining structure of the stainless steel pipe and aluminum alloy pipe which concern on Embodiment 6. It is a longitudinal cross-sectional view which shows the joining structure of the stainless steel pipe and aluminum alloy pipe which concern on Embodiment 7. It is the (a) longitudinal cross-sectional view which shows the mode of the connection metal fitting after an shaping | molding of an Example, (b) A cross-sectional view, and (c) A partial cross-sectional view. It is a partial cross-sectional view which shows the mode of the clad material interface vicinity after joining of a connection metal fitting and a stainless steel pipe | tube of an Example. It is a fragmentary longitudinal cross-section which shows the mode of the clad material interface vicinity after joining of a connection metal fitting and an aluminum alloy pipe | tube of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Stainless steel pipe 1a ... Flange part 1b ... Outer peripheral part 2 ... Aluminum alloy pipe 2a ... Flange part 2b ... Outer peripheral part 3 ... Connection metal fitting 3a ... Stainless steel side 3b ... Aluminum alloy side 4 ... Rising part 4a ... Outer peripheral side 4b ... inner peripheral surface side 5 ... flange part 5a ... root part 5b ... aluminum alloy side 6, 7 ... insert material 8 ... aluminum alloy ring 9 ... welded part

Claims (5)

It is a joint structure of two dissimilar metal tubes made of Fe-based material and Al-based material ,
These dissimilar metal tubes are joined via a connection fitting formed from a double-layer metal clad plate,
The two types of dissimilar metals constituting the two-layer metal clad plate are the same material as the two dissimilar metal tubes, respectively, and the thickness of the Fe-based material constituting the two-layer metal clad plate is 15 to 35% of the total thickness of the two-layer metal clad plate,
The connection fitting is formed in a flange shape having a cylindrical rising portion having an open end by subjecting the double-layer metal clad plate to hole flange processing, and the rising portion of the rising portion The height is 1.0 times or more of the inner diameter of the raised portion,
The two dissimilar metal tubes are divided into an outer peripheral surface side and an inner peripheral surface side of the rising portion, and are inserted so that the metals of the same kind are in contact with each other. Only the parts that come into contact with each other are joined by welding or brazing,
Bonding structure of dissimilar metal tubes characterized by   The connecting metal fitting is formed into a cylindrical shape by cutting the vicinity of the root of the raised portion after forming a cylindrical raised portion having an open end by subjecting the double-layer metal clad plate to hole flange processing. 2. The dissimilar metal pipe joining structure according to claim 1, wherein the dissimilar metal pipe is joined.   The joint structure for dissimilar metal tubes according to claim 1 or 2, wherein the hole flange processing opens the tip portion of the double-layer metal clad plate after deep drawing.   The joint structure for dissimilar metal pipes according to claim 1 or 2, wherein the hole flange processing is to deeply drill the double-layer metal clad plate, then to form a pilot hole at the tip, and thereafter to perform burring. .   The dissimilar metal pipe joining structure according to claim 1 or 2, wherein the hole flange processing is to perform burring after a pilot hole is previously formed in the double-layer metal clad plate.

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