JP2010240696A - Joining method of tube material, and heat exchanger formed by joining tube material joined by joining method and fin material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joining method by which penetration leakage is not caused in an early stage by preventing the preferred corrosion of a torch brazed part. <P>SOLUTION: In the joining method by which two tube materials each formed by providing a clad layer of pure Al having ≥99.5 wt.% purity and ≤0.5% impurities having ≤0.25 wt.% Si, ≤0.40 wt.% Fe and the rest of inevitable impurities on an outer surface of a core material made of an Al alloy are prepared, an end part of one tube material is expanded and the other tube material is inserted in the expanded tube part to join the both tube materials by torch brazing, a brazing material used for torch brazing is an Al alloy having 11.0 to 13.0 wt.% Si, 1.0 to 2.0 wt.% Zn and the rest of inevitable impurities and torch brazing is retained for 3 to 8 sec after reaching 600°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a joining method in which brazing properties and corrosion resistance of parts joined by torch brazing are improved, and a heat exchanger in which a pipe material and a fin material joined by the joining method are joined.

  Conventionally, heat exchangers for home air conditioners have joined copper pipes and aluminum fins by mechanical expansion. As shown in FIG. 6, this method is a system in which a tube expansion jig 7 is pushed into the tube material from the end of the tube material 1, and the tube material is expanded and joined to the fin material 6. After this step, the vacant ends are connected with U-shaped parts and joined by torch brazing to produce a heat exchanger.

  In recent years, it has been proposed to replace copper pipes with aluminum alloys from the viewpoint of recycling air conditioners. Similarly, when the tube material is an aluminum alloy, the fin material and the tube material are mechanically expanded and joined by torch brazing to produce a heat exchanger.

  In heat exchangers made of aluminum alloy tubes, there is a problem that penetration corrosion occurs in the R bend and U bends that are not in contact with the fin material, compared to the case of using conventional copper tubes. It was. Therefore, a tube material in which an Al-1 wt% Zn alloy is clad on the surface of the extruded tube and a tube material in which Zn is sprayed are used. As a result, Al-1 wt% Zn alloy or pure Zn coated on the surface of these tubes acts as a sacrificial anode material, and it is possible to prevent penetration corrosion of the R bend part and U bend part not in contact with the fin material. all right.

  However, when these clad pipes and Zn sprayed pipes are used and torch brazing is performed using 4047 alloy brazing material, there is a problem that penetration corrosion leakage occurs at the joint of the torch brazing part of the pipe. It was. As shown in FIG. 7, in a pipe material having an Al—Zn layer that acts as a sacrificial anode material in the R bend portion and the U bend portion, when a torch brazing is usually performed using a brazing material of 4047 alloy, a cladding layer is formed at the joint portion. However, it is lower in potential than the brazing material layer, and therefore corrodes preferentially over the brazing material layer. In the case of a Zn spray tube, penetration corrosion occurs due to the formation of a Zn-enriched layer in the brazing filler fillet. In FIG. 7, reference numeral 1 denotes a pipe material whose end is expanded, 2 denotes a pipe material inserted into the pipe material 1, 3 denotes a sacrificial anode material preferentially corroded in the brazing part, and 5 denotes a brazing material.

  As a means for preventing such corrosion of the joint portion, as described in Patent Document 1, the joint portion of the aluminum tube body is surrounded by a sleeve provided with a brazing filler metal layer or a solder layer and then heat-joined. Can be considered. In this method, the length of the joint portion is increased, so that the time until leakage through can be extended, but the preferential corrosion of the sacrificial material cannot be completely prevented. In addition, when this method is used, the sleeve is connected to the joint portion, which leads to an increase in the number of parts and the number of man-hours, resulting in an increase in cost.

JP 58-163572 A

  On the other hand, JISA1200 alloy or the like is used as a fin material used for a home heat exchanger. However, if the potential configuration of the fin material and the pipe material is not appropriate, that is, if the potential on the surface of the pipe material is significantly lower than that of the fin material, Is a sacrificial material that prevents corrosion of the fin material, and the pipe material corrodes at the part where the fin material and the pipe material are joined, causing crevice corrosion, and there is also a problem that early penetration corrosion occurs at this tube material part. .

  In view of the above problems in the prior art, the present invention has good brazeability and preferential corrosion resistance in a torch brazing portion that is a joint portion, and has corrosion resistance in R and U bend portions that are non-joint portions. It is an object of the present invention to provide a joined pipe material, and to provide a heat exchanger in which the pipe material and the fin material are joined and which prevents crevice corrosion at the joint of the pipe material / fin material.

  In order to solve such a problem, the present invention according to claim 1, the outer surface of the core material made of an Al alloy contains impurities having a purity of 99.5 wt% or more and 0.5 wt% or less, and the impurities are Si Prepare two pipes with a pure Al cladding layer made of the remaining unavoidable impurities at 0.25 wt% or less, Fe as 0.40 wt% or less, and expand the end of one tube, In the method in which the other pipe material is inserted and both pipe materials are joined by torch brazing, the brazing material used for torch brazing is Si 11.0 wt% to 13.0 wt%, Zn 1.0 wt% to 2.0 wt%, and the balance is not left. It was an Al alloy composed of an avoidance impurity, and a method of joining pipe materials characterized in that the torch brazing was held for 3 to 8 seconds after reaching 600 ° C. Moreover, in Claim 2, it was set as the heat exchanger which joined the pipe material joined by the joining method of Claim 1, and the fin material.

  ADVANTAGE OF THE INVENTION According to this invention, the joining pipe material which prevented the favorable brazing property and the preferential corrosion resistance of the junction part by torch brazing, and the corrosion resistance in a non-joining part can be provided, Furthermore, pipe | tube / fin material It is possible to provide a heat exchanger that prevents crevice corrosion and does not generate through-hole corrosion at an early stage.

It is sectional drawing which shows the joining method which concerns on this invention. It is sectional drawing explaining the electric potential state of the junction part in a clad tube. It is sectional drawing which shows typically the corrosion progress in a clad tube. It is sectional drawing explaining the electric potential state of the junction part in a Zn spray tube. It is sectional drawing which shows typically the corrosion progress in a Zn spray tube. It is sectional drawing explaining joining of a pipe material and a fin material. It is sectional drawing which shows the preferential corrosion of a pipe material. It is a top view which shows the junction part and non-joint part of a heat exchanger minicore. It is a front view which shows the junction part and non-joint part of a heat exchanger minicore.

A. Mechanism of Through Leakage Phenomenon When the clad pipe material clad with Al-1 wt% Zn is joined by torch brazing, the sacrificial material of the clad pipe material is preferentially corroded at the joint and leads to through leakage. When Zn sprayed tube material was joined by torch brazing, the mechanism of the phenomenon in which the Zn concentrated layer generated in the brazing filler fillet portion of the joint portion preferentially corroded and caused through leakage was studied. Specifically, as shown in FIG. 1, a case is considered in which the pipe material 2 is inserted into the expanded portion of the pipe material 1 having one end expanded, and both the pipe materials 1 and 2 are joined by torch brazing using the torch brazing material 5. did. Here, the layer 3 formed on the outer surface of the core material 4 of the tube materials 1 and 2 represents an Al—Zn layer or a Zn sprayed layer which is a cladding layer.

  As shown in FIG. 2, the phenomenon that leads to penetration leakage in the clad pipe material is that the corrosion potential of the Al—Zn layer 3, which is the clad layer, is lower than the torch brazing material 5 and the core material 4 of the pipe material. to cause. In FIG. 2, the vertical axis of the graph indicates an arbitrary distance in the radial direction from the axial center of the tube material 2, and the corrosion potential indicates a relative potential of each part. Then, as schematically shown in FIG. 3, the Al—Zn layer 31 other than the joint portion in the pipe material 2 disappears in the middle stage of corrosion in which corrosion has progressed. Further, it was found that the Al—Zn layer 32 at the joint portion of the pipe material 2 is preferentially corroded by the action of the corrosion potential difference between the torch brazing material 5 and the Al—Zn layer 3 in the late stage of corrosion.

  As shown in FIG. 4, the phenomenon that leads to penetration leakage in the Zn sprayed tube material is such that the corrosion potential of the Zn concentrated layer 51 generated in the brazing filler fillet portion of the joint is lower than that of the torch brazing material 5 and the core material 4 of the tube material. This is due to the fact that In FIG. 4, the vertical axis of the graph indicates an arbitrary distance in the radial direction from the axial center of the tube material 2, and the corrosion potential indicates a relative potential of each part. Then, as schematically shown in FIG. 5, the Zn sprayed layer 31 other than the joint portion in the pipe material 2 disappears in the middle stage of corrosion in which the corrosion has progressed. Further, in the later stage of corrosion in which corrosion has progressed, not only the Zn sprayed portion other than the joint in the pipe material 2 disappears but also the Zn concentrated layer 51 has priority due to the effect of the corrosion potential difference between the torch brazing material 5 and the Zn concentrated layer 51. Was found to corrode. In FIG. 5, 52 represents a corroded Zn concentrated layer portion.

As a result of intensive studies, the present inventors have found that, as a fundamental measure for preventing this preferential corrosion, it is effective to prevent the Al—Zn layer from being present in the joint portion for the penetration leakage in the clad pipe material. It was. Specifically, at the time of torch brazing, the Al—Zn material is eroded by the molten brazing material, and the brazing material and the Al—Zn material are integrated.
On the other hand, it has been found that it is effective to prevent a Zn-enriched layer from being present in the brazing filler metal layer at the joint portion against penetration leakage in the Zn sprayed tube material. Specifically, in the pre-stage of torch brazing, thermal diffusion is applied to the Zn sprayed layer on the surface of the tube material so that the Zn concentration in the surface layer is previously reduced.

  In any case of the clad tube material and the Zn sprayed tube material, it was necessary to add 1.0 to 2.0 wt% of Zn to the 4047 brazing material in the torch brazing material. As a result, in the clad tube material, the clad layer was eroded by the torch brazing material, and the clad layer disappeared. In the Zn sprayed tube material, the Zn concentration in the joint became low and uniform. As a result, it was found that in any case, preferential corrosion at the pipe joint can be prevented.

  However, even if such preferential corrosion at the pipe joint is prevented, another problem arises when the corrosion resistance is evaluated as a heat exchanger. As a fin material of a heat exchanger core of a home air conditioner, JISA1200 alloy is usually used from the viewpoint of strength and thermal conductivity. In a pipe material provided with an Al-Zn cladding layer or a Zn sprayed layer, the potential relationship between the surface layer and the fin material is such that the pipe material serves as a sacrificial layer to prevent corrosion of the fin material. It has been found that the pipe material corrodes in this part and crevice corrosion occurs, and early corrosion penetration may occur in the pipe material in this part. The present inventors have found that it is effective to make the potential on the surface of the pipe material nobler than the Al—Zn layer or the Zn sprayed layer as a fundamental measure for preventing this crevice corrosion. Specifically, it has been proved that it is effective to use a pipe material in which pure Al having a purity of 99.5 wt% or more is used as a cladding layer.

B. Tube according to the tube present invention are those having a clad layer of a purity 99.5 wt% or more pure Al on the outer surface of the core material made of Al alloy.
As shown in FIG. 1, the tube material 1 whose end is expanded and the tube material 2 inserted into the expanded portion are each composed of a core material 4 and a cladding layer 3 clad on the outside thereof. In any of the cladding layers, pure Al having a purity of 99.5 wt% or more is used. The pipe materials 1 and 2 are usually the same pipe material in which the metal composition of the core material and the clad layer, the thickness of the core material and the clad layer, the outer diameter and the inner diameter of the entire pipe material are the same. However, it is also possible to use those in which at least one of the metal composition of the core material and the clad layer, the thickness of the core material and the clad layer, and the outer diameter and the inner diameter of the entire pipe material are different.

B-1. Core Material In the present invention, the core material component of the tube material is not particularly limited, but an alloy that exhibits a potential at which a pure Al layer described later can be sacrificial and corrosion-proof and does not melt during brazing is used. When high strength is not required for the clad tube, JIS3003 alloy is used. When high strength is required, JIS3105 alloy or Al-1% Mn-0.5% Cu alloy with a relatively large amount of Cu added, etc. Are preferably used. As a component of the core material, Si is preferably 0.6 wt% or less, Fe 0.7 wt% or less, Mn 0.8 to 1.5 wt%, Cu 0.05 to 0.5 wt%.

  Si is contained as an impurity, but if this amount exceeds 0.6 wt%, the corrosion resistance of the core material may be inferior, so the amount of Si added is preferably 0.6 wt% or less. Fe is also contained as an impurity. However, if this addition amount exceeds 0.7 wt%, the corrosion resistance of the core material may be inferior, so the addition amount of Fe is preferably 0.7 wt% or less. If the amount of Mn added is less than 0.8 wt%, the strength of the tube may be inferior, and if it exceeds 1.5 wt%, it may be difficult to extrude the tube. Therefore, the amount of Mn added is preferably 0.8 wt% to 1.5 wt%. If the added amount of Cu is less than 0.05 wt%, the potential difference between the core material and the pure Al layer as the cladding layer becomes small, and the sacrifice effect of the pure Al layer may not be exhibited. Moreover, when it exceeds 0.5 wt%, intergranular corrosion may occur. Accordingly, the amount of Cu added is preferably 0.05 wt% to 0.5 wt%.

B-2. The clad layer formed outside the clad layer core material is a pure Al layer having a purity of 99.5% or more. If the content of Si or Fe, which is an impurity contained in Al, exceeds 0.25 wt% for Si and 0.40 wt% for Fe, the potential of the pure Al layer becomes noble and the sacrificial anticorrosive effect may be impaired. is there. As a result, the corrosion resistance of the R bend part and the U bend part where the pipe material is exposed to the corrosive environment is deteriorated. Therefore, in the present invention, the surface of the clad pipe material is coated with pure Al having a purity of 99.5% or more. Impurities include unavoidable elements. In order to make the Al purity 99.5% or more, the total amount of impurities composed of Si, Fe and unavoidable elements is specified to be 0.5 wt% or less. Therefore, on the assumption that the total amount of impurities is 0.5 wt% or less, Si is up to 0.25 wt%, Fe is up to 0.40 wt%, and unavoidable elements are contained.

  The cladding layer thickness is preferably 50 μm to 100 μm. If the clad layer thickness is less than 50 μm, the sacrificial anticorrosive effect of the clad layer may not be sufficiently exhibited in the R bend part or U bend part, and the penetrating life may be shortened. On the other hand, if it exceeds 100 μm, the corrosion resistance of the R bend part and U bend part is secured, but in the torch brazing part, the clad layer cannot be eroded by the torch brazing material by brazing, so preferential corrosion of the clad layer occurs. There is a case.

B-3. Production of tube material A tube material is produced as follows. First, a combination billet is manufactured by covering the outer surface of a cylindrical core material with a skin sleeve serving as a cladding layer. The thickness of the skin sleeve is selected so as to obtain a desired cladding layer thickness. Next, the combined billet is soaked at 350 ° C. to 600 ° C. in a heating furnace. Next, sandwich the combination billet between the die and the ramnose and insert it into the container. With the die and the ramnose fixed, press-fit a mandrel with an outer diameter larger than the inner diameter of the core, and expand the inner diameter of the core Expel the air between the core and skin. Further, the mandrel is fixed at a predetermined position, the hollow system is advanced, the combination billet is pushed out through a die, and a seamless hollow tube material is obtained. Finally, a clad tube having a predetermined outer diameter and inner diameter is produced through a drawing process.
Alternatively, a core tube may be produced by extrusion and a cladding layer may be formed on the outer surface by thermal spraying.

C. Components of the torch brazing material torch brazing material, Si11.0wt% ~13.0wt%, is Zn1.0wt% ~2.0wt% of Al-Si-Zn alloy is used. When the Si content is less than 11.0 wt%, the liquid phase amount is insufficient at the time of brazing because it deviates from the eutectic composition of the brazing material. As a result, the torch brazability is poor. On the other hand, when the content exceeds 13.0 wt%, since the brazing material has a hypereutectic composition, primary crystals of large Si grains are precipitated in the brazing material, thereby inhibiting the flowability of the brazing. As a result, the torch brazability is poor. Therefore, the amount of Si is defined as 11.0 wt% to 13.0 wt%.

  When the Zn content in the brazing material is less than 1.0 wt%, the potential difference between the pure Al cladding layer and the brazing material becomes large, so that the preferential corrosion of the pure Al cladding layer occurs at the joint. When the content exceeds 2.0 wt%, the liquid phase amount at the brazing temperature is sufficient and the clad layer can be eroded. However, since the Zn content in the brazing material layer formed after brazing increases, the brazing material layer The amount of its own corrosion dissolution increases. As a result, the brazing filler metal layer is corroded and dissolved, and penetration corrosion occurs at the joint. Therefore, the amount of Zn contained in the torch brazing material was defined as 1.0 wt% to 2.0 wt%.

  In the present invention, it is preferable to use a wire-shaped torch brazing material. A wire brazing material cast to a predetermined component is heated to 400 ° C., extruded into a round bar shape through a die, and drawn through a die to produce a wire having a predetermined diameter.

D. Torch Brazing As shown in FIG. 1, a tube material 2 with a flux applied to a joint portion is inserted into a tube expansion portion of a tube material 1 having one end expanded. Next, the torch brazing material 5 is disposed at the joint, and both the pipe materials 1 and 2 are brazed and joined by torch brazing using a torch such as propane, air, and torch. As the flux, a fluoride-based flux or a cesium-based flux can be used. Thus, a general method can be used for the torch brazing method.

  The torch brazing conditions are held for 3-8 seconds after reaching 600 ° C. When the brazing temperature is 600 ° C. for less than 3 seconds, heat does not flow uniformly to the torch brazing portion, and the brazing material cannot completely erode the sacrificial material. On the other hand, if it exceeds 8 seconds, the erosion of the brazing will become severe, and a smooth joint surface cannot be formed, resulting in poor brazing. On the other hand, if the brazing temperature is less than 600 ° C., the brazing is not sufficiently dissolved and brazing becomes incomplete. Therefore, the brazing condition was defined as holding for 3 to 8 seconds after reaching 600 ° C.

E. Production of Heat Exchanger A heat exchanger according to the present invention can be obtained by joining the above-described tube material and fin material. As the fin material, JISA1200 alloy, JISA1100 alloy or the like is used. By using these alloys, the shape of the fin hole (burring shape) into which the pipe material is inserted can be formed into a shape in which the fin and the tube are brought into close contact with each other. In combination with these tube material and fin material, a tube expansion jig is pushed into the tube material, and the tube material is expanded and brought into close contact with the fin hole. After this, the tubes containing the expansion jigs are connected with the expanded U-tube components of the same structure, and a heat exchanger is manufactured by placing a wire solder at the joint and brazing the torch. .

  Embodiments of the present invention will be specifically described below based on the present invention examples and comparative examples.

Invention Example No. 1-9 and Comparative Example No. 10-18
Table 1 shows the components of the wire brazing material, the impurity content of the pure Al cladding layer, and the brazing conditions (temperature and time). The wire brazing material was cast as a predetermined component, extruded onto a round bar, and then drawn through a die to produce a wire material having a diameter of 1.4 to 2.2 mm.
The tube material was prepared as follows. A cylinder of JIS3003 was used as a core material, and a skin sleeve of a pure Al alloy containing Si and Fe as impurities was placed on the outer surface thereof to produce a combined billet. Next, the combined billet was soaked at 350 to 600 ° C. in a heating furnace. Further, sandwich the combination billet between the die and the ram nose and insert it into the container. With the die and the ram nose fixed, press-fit a mandrel having an outer diameter larger than the inner diameter of the core, and expand the inner diameter of the core. The air between the core and skin was expelled. The mandrel was fixed in place, the hollow system was advanced and the combined billet was extruded through a die to produce a seamless hollow tube material. Subsequently, two clad tubes having an outer diameter of φ8 mm and an inner diameter of φ7 mm were produced through a drawing process. Using these pipes, the pipe material 1 was expanded in the same manner as the joining portion of the actual heat exchanger, and the pipe material 2 was inserted into the expanded pipe portion. Next, a fluoride-based flux was applied to the joining portion, and torch brazing was performed using a wire brazing material to obtain a joining test piece.

The following evaluation was performed using the joining test piece produced as described above.
(1) Brazing evaluation at joints between pipe materials After cutting the cross-section of the joint specimen and polishing with resin filling, the mark where the joint mark was present over 10 mm or more was marked with ◯, and the joint mark was 5 mm or more and less than 10 mm or less Those having a thickness of less than 5 mm were evaluated as “x”. ○ and Δ were accepted and x was rejected.

  Next, the joining test piece produced as described above and a fin material made of JISA1200 alloy are molded, and the tube test piece is hydraulically expanded to form a mini-core that resembles an actual heat exchanger (FIGS. 8 and 8). 9) The following evaluation was performed. In FIGS. 8 and 9, reference numerals 1, 2 and 6 are the same members as in the other drawings, A is the joint between the pipes 1 and 2, B is the R bend, C is the U bend, and D is the lower fin. .

(2) Corrosion test Using the heat exchanger mini-core produced as described above, a CASS test according to JISH8601 was performed for 2000 h. After the test, the core fin material was removed, and the corrosion products attached to the pipe material were removed with concentrated nitric acid and phosphoric acid-chromic acid mixed solution. Next, the depth of corrosion of the pipe material 2 which is the inner pipe material in the joint portion shown in FIGS. 8 and 9 and the corrosion depth of the pipe material under the R bend portion, U bend portion and fins which are non-joint portions are used as the depth of focus method. Measured. The results are shown in Table 1. Those that did not penetrate were accepted, and those that penetrated were rejected.

Comparative Example 19
A cylinder according to JIS3003 was used as a core material, and a skin sleeve made of an Al-1% Zn alloy was covered on the outer surface thereof to produce a combined billet. Next, the combined billet was soaked at 350 to 600 ° C. in a heating furnace. Further, sandwich the combination billet between the die and the ram nose and insert it into the container. With the die and the ram nose fixed, press-fit a mandrel having an outer diameter larger than the inner diameter of the core, and expand the inner diameter of the core. The air between the core and skin was expelled. The mandrel was fixed in place, the hollow system was advanced and the combined billet was extruded through a die to produce a seamless hollow tube material. Subsequently, two clad tubes having an outer diameter of φ8 mm and an inner diameter of φ7 mm were produced through a drawing process. Using these pipes, the pipe material 1 was expanded in the same manner as the joining portion of the actual heat exchanger, and the pipe material 2 was inserted into the expanded pipe portion. Next, a fluoride-based flux was applied to the joint portion, and a torch brazing was performed at 600 ° C. for 3 seconds using a wire brazing material to obtain a joint specimen.

Comparative Example 20
A billet of JIS3003 was produced as a tube material, and this was soaked at 350 ° C. to 600 ° C. in a heating furnace. Next, the billet was inserted into a container, and the billet was extruded through a die to produce a hollow tube material. Further, a Zn spray tube having an adhesion amount of 10 g / m ² was produced through the Zn spray gun. This Zn sprayed tube was preheated at 430 ° C. for 8 hours. In this way, two Zn spray tubes having an outer diameter of 8 mm and an inner diameter of 7 mm were produced. Using these pipes, the pipe material 1 was expanded in the same manner as the joining portion of the actual heat exchanger, and the pipe material 2 was inserted into the expanded pipe portion. Next, a fluoride-based flux was applied to the joining portion, and a torch brazing was performed at 600 ° C. for 5 seconds using a wire brazing material to obtain a joining test piece.

As is apparent from Table 1, in Examples 1 to 8 of the present invention, the torch brazing property at the joint was good. Moreover, the corrosion resistance in the junction part and non-joint part in a heat exchanger minicore was also favorable.
In Comparative Example 10, since the amount of Si in the pure Al cladding layer exceeded the range of the present invention, the corrosion resistance of the R bend portion and the U bend portion was inferior, and penetration corrosion occurred.
In Comparative Example 11, since the amount of Fe in the pure Al cladding layer exceeded the present invention, the corrosion resistance of the R bend part and the U bend part was inferior, and penetration corrosion occurred.
In Comparative Example 12, since the amount of Si in the brazing material wire was less than that of the present invention, the liquidus temperature of the brazing material was lowered, and thus the torch brazing was poor.
In Comparative Example 13, since the amount of Si in the brazing material wire exceeded the present invention, the liquidus temperature of the brazing material was lowered, and the torch brazing property was poor.
In Comparative Example 14, since the amount of Zn in the brazing filler metal wire was less than that of the present invention, the potential difference between the Zn-enriched layer and the brazing filler metal portion increased, preferential corrosion occurred in the joint portion, and the corrosion resistance at the joint portion was poor.
In Comparative Example 15, since the amount of Zn in the brazing material wire exceeded the present invention, the amount of Zn in the brazing material increased and the amount of corrosion in the fillet portion increased, resulting in poor corrosion resistance at the joint.
In Comparative Example 16, since the holding time of the torch brazing was less than that of the present invention, the brazing property of the joint was poor.
In Comparative Example 17, since the holding time of the torch brazing exceeded the present invention, the brazing of the joint portion was poor.
In Comparative Example 18, since the temperature of the torch brazing was lower than that of the present invention, the brazing of the joint portion was poor.
In Comparative Examples 19 and 20, since a pure Al clad layer having a purity of 99.5 wt% was not used, the corrosion resistance at the lower portion of the fin was inferior.

  As described above, according to the present invention, there is provided a joining pipe material having good brazing property and preferential corrosion resistance in a torch brazing part which is a joint part, and corrosion resistance in R joint and U bend part which are non-joint parts. Is done. And the heat exchanger which prevented the crevice corrosion in the junction part of a pipe material / fin material by joining these pipe materials and fin materials is provided.

DESCRIPTION OF SYMBOLS 1 ... Tube material, tube 2 ... Tube material 3 ... Cladding layer, Zn sprayed layer, sacrificial anode material 31 ... Al-Zn layer 32 ... Al-Zn layer 4 ... Core material 5 ... Brazing material, torch brazing Material 51 …… Zn enriched layer 52 …… Zn enriched layer 6 …… Fin 7 …… Jig for tube expansion A …… Junction B BR R bend C …… U bend D Dfin bottom

Claims (2)

  The outer surface of the core material made of an Al alloy contains impurities of purity 99.5 wt% or more and 0.5 wt% or less, and the impurities are 0.25 wt% or less as Si and 0.40 wt% or less as Fe, and the remainder is inevitable In a method of preparing two pipes provided with a pure Al cladding layer made of impurities, expanding one end of one pipe, inserting the other pipe into the expanded part, and joining both pipes by torch brazing The brazing material used for torch brazing is an Al alloy consisting of Si 11.0 wt% to 13.0 wt%, Zn 1.0 wt% to 2.0 wt% and the remaining inevitable impurities, and the torch brazing reaches 600 ° C. The method for joining pipe materials is characterized in that the tube material is held for 3 to 8 seconds.   The heat exchanger which joined the pipe material and the fin material which were joined by the joining method of Claim 1.

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