JP6149830B2 - Joining member and Al-Cu joining pipe using the same - Google Patents

Description

  The present invention relates to a member used for eutectic bonding between an Al tube and a Cu tube, and an Al—Cu bonded tube formed using the member.

  In heat exchangers for refrigeration equipment and air conditioning equipment such as vending machines, Al tubes are suitable for evaporators and condensers, and Cu tubes are suitable for compressors and capillaries. Al-Cu bonded pipes are used. Although fusion welding, pressure welding, brazing, and the like are known for joining an Al tube and a Cu tube, eutectic joining has begun to be used from the viewpoint of airtightness, mechanical strength, and manufacturing cost.

  Patent Documents 1 to 5 disclose eutectic bonding methods of Al and Cu. In the Al—Cu eutectic bonding, the Al member and the Cu member are in close contact with each other and heated to a temperature equal to or higher than the eutectic temperature (548 ° C.) of the AlCu alloy. In the joining method, the region interdiffused in (for example, a region where 2.5 atomic percent <Cu <32 atomic percent at the eutectic temperature) is melted and then cooled to the eutectic temperature or lower to solidify the molten region. .

  In order to ensure the mechanical strength of the Al—Cu bonded tube, it is a necessary condition that the eutectic bond is formed on the bonded surface without any spots, and various production methods are disclosed. For example, Patent Document 3 discloses a technique for increasing the bonding area by forming a taper in a Cu tube. Patent Document 4 discloses a technique for restraining an Al pipe and Cu pipe joint with a mold. Patent Document 5 discloses a method in which a Cu pipe is heated in a state where a pressing force is preliminarily applied to an Al pipe and then press-fitted. By these methods, an interdiffusion region with a width required for forming a eutectic bond is secured on the bonding surface, and an oxide film that obstructs the interdiffusion between the Al tube and the Cu tube is removed and an extra eutectic fusion is performed. The liquid can also be removed.

Japanese Patent Laid-Open No. 51-112455 JP 54-133450 A JP-A-9-85467 JP-A-11-216576 JP 2001-334371 A

  However, when a mechanical strength exceeding 1000 N is obtained in an Al—Cu bonded tube, it has been found that it is not sufficient to form a eutectic bond uniformly on the bonding surface.

When the cross section of the Al—Cu eutectic junction is observed with an optical microscope or a scanning electron microscope, an α phase and a lamellar structure are seen on the Al tube side, and a θ phase and a lamellar structure are seen on the Cu tube side. Here, the α phase is an Al alloy having a face-centered cubic structure with a Cu amount of 2.5 atomic percent or less at the eutectic temperature, and the θ phase is a Cu amount of 32 to 33 atomic percent at the eutectic temperature. On the other hand, it is a tetragonal alloy crystal expressed as Al ₂ Cu, and the lamellar structure is a striped structure composed of an α phase and a θ phase.

  A coarse (> 10 μm) θ phase is formed on the cross-section of the Al—Cu joint, which is considered to have low bonding strength in the prior art. Since the θ phase is mechanically fragile, the eutectic joint breaks around the θ phase, causing a significant reduction in the strength of the bonded tube. In an actual manufacturing process, there are variations in heating temperature and heating time, and it is difficult to control the particle size of the brittle θ phase, and therefore it is inevitable that defective products with poor mechanical strength are generated due to the coarsening of the θ phase.

  Therefore, an object of the present invention is provided for eutectic bonding of a Cu tube having a taper at the tip and an Al tube having an inner diameter large enough to fit the tip of the Cu tube. An object of the present invention is to provide a joining member that can prevent the brittle θ phase from becoming coarse at the joint with the pipe, and an Al—Cu joined pipe that is joined by the joining member and has excellent mechanical strength.

  In order to achieve the above object, the joining member of the present invention has a metal tube made of Cu, a metal tube made of Al, and an end surface of the other metal tube inserted into the inner surface of the end of the other metal tube. A joining member that is inserted between both metal tubes, heated to a temperature equal to or higher than the eutectic temperature, melted and then cooled and solidified to eutectic-join the Cu tube and the Al tube, and the Cu content is Cu and Al. It is characterized by being 16.5 to 19.0 atomic percent AlCu-based alloy with respect to the total amount.

  In the bonding member of the present invention, the surface connected to the Al tube can contain more Cu than the surface connected to the Cu tube.

  Moreover, the joining member of this invention can be made into the annular | circular shape provided with a projection part in three or more places of the surface connected to the said Cu pipe | tube so that it may have a dotted contact part with the said Cu pipe | tube.

  In the Al—Cu bonded tube of the present invention, the Cu content is between 16.5 and 19.0 atomic percent of the total amount of Cu and Al between the metal tube made of Cu and the metal tube made of Al. A bonding member made of an AlCu-based alloy is inserted, the bonding member is heated to a temperature equal to or higher than the eutectic temperature, melted, and then cooled and solidified to perform eutectic bonding.

  According to the joining member of the present invention, in the joining process of the Cu tube and the Al tube, the coarsening of the brittle θ phase is suppressed regardless of variations in the preheating time, joining temperature, and joining time, and the crystal structure of the joint is a lamella. Since it has a structure, it is possible to manufacture an Al—Cu bonded tube having excellent mechanical strength.

It is a schematic diagram which shows the shape of the joining member which concerns on one Embodiment of this invention. It is a schematic diagram which shows the shape of the joining member which concerns on other embodiment of this invention. It is a schematic diagram which shows the shape of the joining member which concerns on other embodiment of this invention. It is process schematic diagram which shows an example of the joining process of the Al-Cu joining pipe | tube using the joining member of this invention. It is a schematic diagram which shows the temperature profile in the joining process of the Al-Cu joining pipe | tube of this invention. In the conventional eutectic bonding method, it is the Al-Cu type phase diagram which showed the composition range which changes into a liquid phase by joining temperature _Tj . In the conventional eutectic bonding method, it is the cross-sectional schematic diagram which shows the mutual diffusion area | region in the junction part of Al pipe | tube and Cu pipe | tube, and drawing which shows Cu content rate distribution of a perpendicular direction with respect to a joint surface. In the conventional eutectic bonding method, it is an Al-Cu phase diagram showing that the composition range to be liquid phase changes in response to the bonding temperature _Tj . In the conventional eutectic bonding method, it is a cross-sectional schematic diagram which shows the grain growth of (theta) phase in the Cu pipe side interface. In the eutectic bonding method of this invention, it is a cross-sectional schematic diagram which shows the state by which the molten joining member is hold | maintained in the clearance gap between an Al pipe and Cu pipe. In the eutectic bonding method of this invention, it is drawing which shows the form of the solidification structure calculated from the liquid phase composition of a joining member. In the eutectic bonding method of this invention, it is drawing which shows the relationship between Cu content of a liquid phase, and the particle size of (theta) phase. It is an Al-Cu system phase diagram which shows the procedure which determines the composition range and minimum heating temperature of the joining member of this invention. In the eutectic bonding method of the present invention, as a result of Al diffusing from the Al tube into the liquid phase (Cu = 18 atomic percent) of the bonding member, a lamellar structure is formed without coarsening the θ phase grains at the Al interface. It is a cross-sectional schematic diagram which shows. The diffusion of Al from the Al tube and Cu from the Cu tube into the liquid phase of the joining member in which the Cu amount on the outer diameter side of the present invention is 19 atomic percent and the Cu amount on the inner diameter side is 16.5 atomic percent. It is a schematic diagram which shows that a composition range narrows. It is a schematic diagram showing an example of the preparation process of the joining member which has Cu content gradient of this invention.

  First, the shape of the joining member by one Embodiment of this invention is demonstrated based on drawing.

FIG. 1 shows the shape of the joining member 10. The main body 101 of the joining member 10 has an annular shape with a taper on the outer surface 102 in contact with the Al tube and the inner surface 103 in contact with the Cu tube, the length h, the outer diameter R1_o and the inner diameter R1_i of the upper surface 104, Characterized by the outer diameter R2_o and the inner diameter R2_i of the lower surface 105, the upper surface 104 is wider than the lower surface 105 (R1_i> R2_i and R1_o> R2_o),
Furthermore, as a condition for mounting the joining member 10 to the taper portion of the Cu tube,
Outer diameter of Cu tube tip <R2_i <R1_i <Maximum outer diameter of Cu tube taper portion (1)
As a condition for pressing the Cu pipe on which the joining member 10 is mounted until the joining member 10 contacts the Al pipe,
The outer diameter of the Cu tube tip portion <R2_i <R2_o <the inner diameter of the Al tube tip portion (2) can be set to satisfy each dimension.

  The taper angles of the outer surface 102 and the inner surface 103 of the joining member 10 are not particularly limited. However, the Cu tube with the joining member 10 mounted thereon is reduced by reducing the excess play by making it approximately equal to the taper angle at the tip of the Cu tube. This is preferable because it can be accurately inserted into the Al pipe.

  Alternatively, as in the joining member 10 a shown in FIG. 2, the taper angle of the inner surface 103 is slightly larger than the taper angle of the tip of the Cu tube, and the protrusions 106 are arranged at three locations near the upper surface 104 of the inner surface 103. May be. The protrusion 106 of the joining member 10a can tighten the Cu tube with elasticity when a Cu tube having a tapered tip is inserted, and prevent the joining member 10a from dropping. For positioning, the protrusions 106 are preferably disposed at three or more locations on the inner surface 103, and when the projections 106 are disposed at four locations, the projection 106 looks like the joining member 10b shown in FIG.

Although not shown in FIGS. 1 to 3, the joining member of the present invention does not have to be a complete annular shape, and has a cut or open portion as long as it does not hinder Al-Cu joining. Also good.
In the above embodiment, it is assumed that the Al tube is outside and the Cu tube is inside, but the Al tube can be inside and the Cu tube can be outside. The Al tube is in contact with the inner side surface 103 of 10 and the Cu tube is in contact with the outer side surface 102.
Furthermore, the Al tube and the Cu tube are not necessarily cylindrical, but may be a rectangular tube shape or the like. In that case, the connecting member 10 is also shaped to fit them.

  Next, the material of the joining member 10 of the present invention will be described.

  The joining member 10 of the present invention can use an AlCu-based alloy containing 16.5 to 19.0 atomic percent of Cu with respect to the total amount of Cu and Al.

  Furthermore, the joining member 10 of the present invention is an AlCu-based alloy, and the outer surface 102 contains more Cu than the inner surface 103, and the Cu content of the outer surface 102 is based on the total amount of Cu and Al. The bonding member having a composition gradient is preferably 19.0 atomic percent or less, and the Cu content of the inner surface 103 is 16.5 atomic percent or more with respect to the total amount of Cu and Al.

  The joining member 10 is preferably an AlCu alloy that does not contain impurities, but may contain a trace amount of impurities as long as it does not significantly disturb the eutectic structure of AlCu and does not hinder the mechanical strength. .

  Next, the joining process of the Al pipe and the Cu pipe using the joining member of the present invention will be described with reference to the process schematic diagrams shown in FIGS. The temperature profile in the joining process is as shown in FIG.

  FIG. 4A shows the Cu pipe 20, the Al pipe 30, and the joining member 10 before joining. A taper 21 is formed at the tip of the Cu tube 20. The inner diameter of the joining member 10 satisfies the relationship of the expression (1), and the Cu tube 20 can be inserted into the joining member 10 and mounted on the tapered portion 201. On the other hand, the outer diameter of the joining member 10 satisfies the relationship of the expression (2), and the Cu pipe 20 on which the joining member 10 is mounted can be pushed in until the joining member 10 contacts the Al pipe 30. Here, it is not always necessary to provide a taper at the tip of the Cu tube 20, and a taper may be provided at the tip of the Al tube 30 or the joining member 10. Further, as long as the Cu pipe 20, the joining member 10, and the Al pipe 30 are sufficiently joined, the shape of each member may be other than a tapered shape such as a straight shape or a step shape.

FIG. 4B shows a state where the joining member 10 is pushed into the Al tube 30. When the Cu tube is pushed in, the joining portion can be heated. The temperature rise until time t ₁ when the eutectic temperature is reached is rapidly increased so that mutual diffusion from the Cu tube 20 to the bonding member 10 and mutual diffusion from the Al tube 30 to the bonding member 10 do not proceed unnecessarily. It is preferably warm. Further, until the joining member 10 is completely pushed into the Al tube 30, it is preferable to control the pushing speed and the temperature raising speed in conjunction so as not to exceed the AlCu eutectic temperature (548 ° C.). If melting starts before the joining member 10 is completely pushed into the Al tube 30, the melt may drip, or voids may occur without reaching the gap between the Cu tube 20 and the Al tube 30. Absent. When the protrusion 106 is provided on the inner surface 103 of the bonding member 10, since the contact between the bonding member 10 and the Cu tube 20 is a point contact, the composition variation due to mutual diffusion is suppressed more than the surface contact. The constraints imposed on speed can be relaxed.

In FIG. 4C, the AlCu eutectic temperature is exceeded at time t ₁ , the joining temperature T _j is reached at which time the joining member 10 is melted at time t ₂ , and the joining member 10 is melted and becomes the melted joining member 11. The state of the moment is shown. In the present invention, the melt to meet the clearance Cu tube 20 and the Al tube 30 is derived from the junction member 10, melting at the bonding temperature T _j is instantaneous. During the time from time t ₂ to time t ₃ , the junction temperature T _j is kept constant, and the Cu tube 20 can be further pushed into the Al tube 30 to increase the contact area between the Cu tube 20 and the Al tube 30. The molten joining member 11 can increase the joining strength by expanding the Cu tube 20 into the gap of the Al tube 30 by capillary action as the contact area increases.

The bonding temperature T _j is determined by the composition of the bonding member 10 as described later, but is preferably 555 to 660 ° C., and particularly preferably 560 to 590 ° C. If the temperature is lower than 555 ° C, spots are likely to occur in the melting, and if it is 660 ° C or higher, the Al tube is melted, which is not preferable. The reason why 560 to 590 ° C. is particularly preferable as the bonding temperature T _j is that the eutectic bonding portion becomes too thin when the bonding temperature is less than 560 ° C., and the void strength increases at temperatures higher than 590 ° C. This is because the strength is insufficient.

The holding time t _j (= t ₃ −t ₂ ) is preferably 0.5 to 2.0 seconds, and particularly preferably 0.8 to 1.2 seconds. If the time is shorter than 0.5 seconds, it is difficult to push the Cu tube 20, and if the time is longer than 2.0 seconds, the diffusion region is unnecessarily widened.

FIG. 4D shows a state where the pushing of the Cu tube 20 is completed at time t ₃ . Time t ₃ or later, to cool the joint and the heat turned off.

At time t ₄ , the joint reaches the AlCu eutectic temperature (548 ° C.), the molten joining member 11 is changed to the solidified joining member 12, and the Al pipe 30 and the Cu pipe 20 are joined by the solidified joining member 12. The Al—Cu bonded tube 40 is obtained.

  FIG. 4E shows the completed Al—Cu bonded tube 40.

  As described above, the bonding member and the bonding method of the present invention have been described. However, in the present invention, the most important component in securing the mechanical strength is that the Cu content of the bonding member is based on the total amount of Cu and Al. The point is defined as 16.5 to 19.0 atomic percent.

  Below, the effect obtained by having prescribed | regulated Cu content is demonstrated.

  First, the metallographic properties of a conventional eutectic bonding method (without using a bonding member) compared with the present invention will be described.

In the conventional Al-Cu eutectic bonding method, the heating is started from the state where the Al base material and the Cu base material are in direct contact without using a joining member, and Al and Cu are interdiffused to form a diffusion layer. The According to the Al—Cu system phase diagram shown in FIG. 6, when the AlCu eutectic temperature reaches 548 ° C., in the composition range in which the Cu content is 5 to 33 atomic percent, the eutectic composition is 17.5 atomic percent first. Then, melting starts, and, at the joining temperature T _j , hatching having the intersections C ₁ (melting lower limit Cu content) and C ₂ (melting upper limit Cu content) between the joining temperature T _j and the two liquidus lines at both ends. The resulting composition melts into a liquid phase.

FIG. 7B is an enlarged view of the joining portion of the conventional Al—Cu joining pipe shown in FIG. In FIG. 2B, an interdiffusion region 50 is formed between the Cu base material 21 of the Cu tube 20 and the Al base material 31 of the Al tube 30. In FIG. (C) is a distribution diagram of Cu content in the interdiffusion region 50 is shown, corresponding to the composition sandwiched between the molten lower Cu content C ₁ and the molten upper Cu content C ₂ described in FIG. 6 The part to be melted is melted, and a melted interdiffusion region 51 is formed.

According to the Al—Cu phase diagram shown in FIG. 8, the melting range is wider in FIG. 8B where the bonding temperature T _j is higher than in FIG. 8A where the bonding temperature T _j is lower. The solidified structure of the AlCu alloy has a lamellar structure if the composition of the liquid phase is close to the eutectic point, but if the composition is hypereutectic, the primary crystal becomes the θ phase, and its solid state can be estimated by a balance law. Since the phase ratio is determined by the composition of the liquid phase, the coarsening of the θ phase is promoted as the Cu composition of the liquid phase increases.

FIG. 9A schematically shows a cross section of a joint portion manufactured under a condition where the joining temperature is low. Grain growth of the θ phase formed on the Cu tube side is about ˜5 μm, and coarsening is suppressed. However, when the bonding temperature _Tj is set low, there is a concern that, due to variations in the bonding process, if the temperature further shifts to the lower temperature side, the melting of the interdiffusion region becomes insufficient and bonding failure occurs. On the other hand, FIG. 9 (b) schematically shows a cross section of a bonded portion manufactured under conditions where the bonding temperature is high. The size of the θ phase formed on the Cu tube side grows and coarsens to about 30 μm. This is because if the temperature of the Al tube and the Cu tube are the same, the composition range of the liquid phase toward the hypereutectic side in the temperature range above the eutectic temperature and up to 591 ° C. at which the θ phase becomes completely liquid. This is because of the large shift amount. As described above, in the conventional eutectic bonding method, when the bonding temperature varies, the liquid phase composition varies, and when the liquid phase composition moves to the hypereutectic side, the θ phase becomes coarse and the strength of the Al-Cu bonded tube decreases. To do.

  From here, it becomes detailed explanation regarding the effect of the eutectic bonding by the bonding member of the present invention.

In the bonding method of the present invention, since a bonding member is used to obtain the AlCu melt, it is not necessary to form an interdiffusion layer by diffusing atoms from the base material. Rather, it is preferable to raise the temperature to the joining temperature T _j by rapid heating because this prevents mutual diffusion between the base material and the joining member. The joining member is melted at a certain temperature of 548 ° C. or higher determined by the initial composition of the joining member, and the joining temperature T _j is set by adding the process margin to the melting temperature.

In the present invention, as shown in the schematic cross-sectional view of FIG. 10B, in which the joint portion between the Cu tube 20 and the Al tube 30 shown in FIG. Is directly sandwiched between the Cu base material 21 and the Al base material 31, and no interdiffusion layer is formed. The composition of the bonding member 11 immediately after melting is the same as that of the bonding member 10 before melting, but the Cu base material 21 and the molten bonding member 11 are bonded to the molten bonding member 11 at a time t ₂ to t ₃ held at the bonding temperature T _j. If the supply of Cu atoms and Al atoms from the Al base material 31 is continued, the liquid phase composition will gradually shift.

However, if the time during which the bonding temperature T _j is maintained is short, the shift in the liquid phase composition can be ignored.

  In determining the composition range of the joining member, the inventor performed a simulation by the phase field method in devising the present invention. According to the simulation, the liquid phase composition can be input and the solidified tissue can be visually output.

  FIG. 11 shows the morphology of the solidified structure obtained by calculation by changing the Cu content in the liquid phase to 17.0, 18.0, 19.0, 19.5, 20.0 atomic percent in the simulation. In the figure, the x direction corresponds to the bonding surface direction, the z direction corresponds to the bonding surface vertical direction, and an area of 100 μm × 100 μm is displayed. The black portion in the figure represents the α phase, and the white portion represents the θ phase. When the Cu content is 17.0 and 18.0 atomic percent, the α phase (black spots) is scattered in an island shape, but most of the solidified structure is a lamellar structure (striped pattern). ) Is not coarse. When the Cu content is 19.0 atomic percent, a θ-phase lump is seen on the right side of the screen. It can be seen that when the Cu content is 19.5 atomic percent, the coarsened θ phase spreads throughout the region, and when the Cu content is 20.0 atomic percent, the θ phase is further coarsened.

  FIG. 12 shows the relationship between the Cu content in the liquid phase and the particle size of the θ phase. It can be seen that when the Cu content exceeds 19 atomic percent, the grain size of the θ phase rapidly increases from 10 μm.

  Therefore, in the joining member of the present invention, it was concluded that the coarsening of the θ phase can be prevented if the upper limit of the Cu content is defined as 19.0 atomic percent.

  Next, the lower limit of the Cu content of the joining member will be described.

FIG. 13 shows an enlarged view of the vicinity of the eutectic composition of the Al—Cu phase diagram. Since the upper limit of the Cu content is defined as 19.0 atomic percent, when it moves in parallel with the temperature axis along the arrow Y1 starting from 19.0 atomic percent, it intersects the liquidus and its temperature is 555 ° C. I understand that. This temperature becomes the lower limit of the junction temperature _Tj . Next, when moving parallel to the composition axis along the arrow Y2 from this intersection point, the Cu content on the hypoeutectic side intersects with the 16.5 atomic percent liquidus line. In this invention, Cu content 16.5 atomic percent of this intersection is prescribed | regulated as the minimum of the Cu composition of a joining member.

A joining member made of an AlCu alloy having a Cu content of 16.5 to 19.0 atomic percent is completely in a liquid phase at a joining temperature T _{j of} 555 ° C. or higher. If the temperature is lower than this, the composition range of the liquid phase is closer to the eutectic composition, and thus the coarsening of the θ phase is further suppressed. However, if the amount of the liquid phase itself is reduced, it becomes difficult to reach the entire bonding surface. Therefore, it is particularly preferable to set the lower temperature limit to 560 ° C. in consideration of process tolerance.

  On the other hand, even if the temperature is higher than this, since the liquid phase composition does not change at all, the upper limit of the temperature can be set up to the melting point of Al of 660 ° C. However, at 590 ° C. or higher, the void ratio increases and the bonding strength is insufficient. For this reason, it is preferably 590 ° C. or lower.

The above is a rule that does not consider the shift of the liquid phase composition in the joining process, but there is almost no problem in practical use. The reason for this is that in the present invention, the time t ₂ to t ₃ held at the bonding temperature T _j is defined as 0.5 to 2.0 seconds, and the bonding member 11 melted within this time has a Cu base. Since the supply amounts of Cu and Al supplied from the material 21 and the Al base material 31, respectively, are very small, it is not a big problem. The rapid heating, short-time holding, and rapid cooling processes required in the present invention can be easily realized by a known method such as induction heating means.

  On the other hand, in a preferred embodiment of the present invention, the joining member 10 is an AlCu-based alloy, and the outer surface 102 contains more Cu than the inner surface 103, and the Cu content of the outer surface 102 is made of Cu and Al. It has a composition gradient of 19.0 atomic percent or less with respect to the total amount, and the Cu content of the inner surface 103 is at least 16.5 atomic percent with respect to the total amount of Cu and Al. This effect will be described next.

First, consider the effect of diffusion from the Al and Cu tubes. Even in the Al—Cu bonding interface using the bonding member of the present invention, the influence of composition variation due to diffusion from the Al tube and Cu tube is inevitable in the bonding process from t _{2 to} t ₃ . FIG. 14 shows the results of examining how much the composition of the liquid phase fluctuates when there is diffusion from the Al tube interface with the Cu amount in the liquid phase of the joining member being 18 atomic percent. As described above, when the solidification structure was examined by the simulation by the phase field method, the grains crystallized as primary crystals on the Al interface are almost the same in the α phase and the θ phase, and the case where there is no diffusion from the Al tube. It was found that the crystal composition is almost equivalent, that is, the composition fluctuation of about 0.5 atomic percent is caused. Of course, the value obtained here is considered to vary depending on the bonding temperature, time, etc., but it is one standard. Therefore, in a preferred embodiment of the joining member of the present invention, according to the upper and lower limits of the above estimation, the amount of Cu on the outside is larger than the amount of Cu on the outside, the Cu is 19 atomic percent on the outside and 16.5 atomic percent on the inside. The composition distribution should be an amount. Then, in the joining process from t _{2 to} t ₃ , there is diffusion from the Al tube and the Cu tube, respectively, and it can be seen that the liquid phase composition range can be further narrowed when the liquid phase composition varies. This situation is shown in FIG. That is, if the above diffusion amount is adopted, the composition outside the joining member in contact with the Al tube is 19 atomic percent to 18.5 atomic percent, and the composition inside the joining member in contact with the Cu tube is 16.5 atomic percent to 17 It turns out that it becomes atomic percent, becomes narrower than the composition range of the original joining member, and approaches a eutectic composition. Although it is not certain how much the spatial distribution of the composition of the joining member reflects the spatial distribution of the liquid phase composition, it is actually generated considering that the actual joining time is ~ 1 second or less and the joining width is ~ 100 μm. It is thought that the spatial distribution of the liquid phase composition is appropriate. Therefore, by providing the above-mentioned composition gradient in the joining member, the diffusion range from the Al tube and the Cu tube is taken into consideration, and the composition range of the liquid phase is made closer to the eutectic composition to prevent the θ phase from becoming coarse. Is possible.

[Preparation of joining member]
An example of a manufacturing process of a joining member having a Cu content gradient according to the present invention will be described with reference to FIG.

  As shown in FIG. 16A, a molten AlCu alloy 61 having a eutectic composition (Cu composition = 17.5 atomic percent) was poured into a mold 60 and solidified to obtain a plate-shaped casting 62. Since specific gravity is different between Al and Cu, the Cu content is lower than the eutectic composition in the upper part of the solidified AlCu alloy, and the Cu content is higher than the eutectic composition in the lower part, as shown in FIG. Thus, it becomes a casting in which the Cu composition is inclined in the vertical direction. According to the EDX measurement, the Cu content was 17 atomic percent at the upper end surface of the casting, and the Cu content was 18 atomic percent at the lower end surface.

  A cast plate-like cast 62 shown in FIG. 5B was pressed from the upper surface and molded so that the front side was thin and the depth was thick.

  FIG. 3C shows a cast 63 after press molding. The thickness on the deeper side was (R1_o-R1_i) / 2, and the thickness on the thinner side was (R2_o-R2_i) / 2.

  FIG. 4D is a plan view of the cast 63 after press molding as seen from above. In the cast 63 after press molding, the joining member 64 before bending is marked with a broken line. When the joining member 64 before bending is cut out along the broken line and bent so that the sides A-A ′ and B-B ′ are adjacent to each other, the joining member 10 having an annular shape is obtained. Since the side A-A ′ and the side B-B ′ are not welded, a cut portion remains in the joining member 10. However, since the joining member melts and becomes liquid in the actual joining process, the cut portion does not become a problem, and the target Al—Cu tube is obtained.

  Further, although not shown in FIG. 16, in order to form the protrusion 106 on the joining member 10, when pressing from the upper surface in FIG. You can press at. On the surface of the cast 63 after press molding, a convex portion is formed at a position in the concave portion, which becomes a protrusion 106.

[Preparation of Al-Cu bonded tube]
An Al tube having an outer diameter of φ8.2 mm and an inner diameter of φ8.1 mm, and a Cu tube having an outer diameter of 8.0 mm and an outer diameter of the tip of the tapered portion of φ6.6 mm were used. The dimensions of the joining members are R1_o = φ8.1 mm, R1_i = φ7.9 mm, R2_o = φ8.0 mm, R2_i = φ7.8 mm, h = 2.0 mm, the Cu content on the outer side is 18 atomic percent, the inner side The Cu content was set to 17 atomic percent. The temperature increase rate of the bonding process was 50 ° C./second, the bonding temperature was 570 ° C., the bonding time was 1 second, and the cooling rate was −50 ° C./second. A microwave induction heating method was used for heating. The strength of the produced Al—Cu bonded tube was measured at a pulling speed of 1 mm / s using a tensile tester (Instron, MicroTester 5848). The strength of the Al—Cu bonded tube according to this example was 2500 N, and a good result exceeding the initial target of 1000 N was obtained. When the cross section of the joint portion of the Al—Cu joint tube was observed with a transmission electron microscope, the grain size of the θ phase on the Cu tube side was 2 to 3 μm, and it was confirmed that the coarsening of the θ phase was suppressed. Moreover, in order to see the influence of process fluctuation | variation, it produced by changing joining temperature into 560 degreeC, 580 degreeC, and 590 degreeC, However, In any case, the intensity | strength of the joining pipe showed 2300-2500N stably and showed high joining strength.

  In addition, although the purity of the Al tube and the Cu tube exemplified in this embodiment is often 2N to 3N, inevitable impurities may be present, and the manufacturing process of the joining member is as described above. It is not limited to that.

10, 10a, 10b: Joining member 101: Joining member main body 102: Joining member outer surface 103: Joining member inner side surface 104: Joining member upper surface 105: Joining member lower surface 106: Projection 11: Molten joining member 12 : Solidified joint member (eutectic)
20: Cu pipe 201: Tapered portion of Cu pipe 21: Cu base material 30: Al pipe 31: Al base material 40: Al—Cu bonding pipe 50: Interdiffusion region 51: Molten interdiffusion region (liquid phase)
52: Solidified interdiffusion region 53: Solidified θ phase crystal grains 60: Mold 61: AlCu alloy 62 with molten eutectic composition (Cu content = 17.5 atomic percent) 62: Plate-shaped casting 63: Press Cast 64 after molding: joining members Y1 and Y2 before bending: arrows

Claims (4)

A metal tube made of Cu, a metal tube made of Al, and inserted between both metal tubes when the end surface of the other metal tube is inserted into the inner surface of the end portion of one metal tube. A joining member that is heated and melted and then cooled and solidified to eutectic-join the Cu tube and the Al tube, and the Cu content is 16.5 to 19.0 atoms relative to the total amount of Cu and Al. A joining member comprising a percentage of an AlCu-based alloy , wherein a surface connected to the Al pipe contains more Cu than a surface connected to the Cu pipe . A metal tube made of Cu, a metal tube made of Al, and inserted between both metal tubes when the end surface of the other metal tube is inserted into the inner surface of the end portion of one metal tube. A joining member that is heated and melted and then cooled and solidified to eutectic-join the Cu tube and the Al tube, and the Cu content is 16.5 to 19.0 atoms relative to the total amount of Cu and Al. consists% of AlCu alloy so as to have the Cu tube and point-like contact sites, characterized in that it is a circular shape with a projection over three locations of the surface which is connected to the Cu pipe Joining member. A metal pipe made of Cu, between the metal pipe made of Al, consisting 16.5 to 19.0 atomic percent of the AlCu alloy to the total amount of Cu content Cu and Al, the Al pipe As for the surface to be connected, a joining member containing more Cu than the surface to be connected to the Cu tube is inserted, and the joining member is heated to the eutectic temperature or higher to be melted and then cooled and solidified to form the eutectic. manufacturing method of Al-Cu joint tube, characterized in that the junction. A metal pipe made of Cu, between the metal pipe made of Al, Ri Do from 16.5 to 19.0 atomic percent of the AlCu alloy to the total amount of Cu content Cu and Al, the Cu tube And inserting a joining member having an annular shape having projections at three or more places on the surface connected to the Cu tube so as to have a point-like contact portion , and heating the joining member to the eutectic temperature or higher. manufacturing method of Al-Cu joint tube, characterized in that the cooled and solidified eutectic bonding was melted in.