JP2010221256A - Tube joining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tube joining method capable of preventing the occurrence of any leakage through cracks by preventing preferred corrosion of a torch-brazed portion. <P>SOLUTION: In the tube joining method, two tubes having a clad layer consisting of an Al-Zn alloy on an outer surface of a core consisting of an Al alloy are prepared, one end of one tube is expanded, and the other tube is inserted into the expanded portion to join both the tubes by the torch brazing. The clad layer has the composition consisting of, by weight, 0.50-1.00% Zn and the balance inevitable impurities, and has the thickness of 50-100 μm. A brazing filler metal to be used for the torch brazing is formed of an Al alloy having the composition consisting of 11.0-13.0% Si, 1.0-2.0% Zn, and the balance inevitable impurities, and the torch brazing is kept for 3-8 seconds after the temperature reaches 600°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a joining method in which brazing and corrosion resistance of parts joined by torch brazing are improved.

  Conventionally, a heat exchanger of a home air conditioner has joined a copper tube and an aluminum fin material by mechanical expansion. As shown in FIG. 6, this method is a system in which a tube expansion jig 8 is pushed into the tube from the end of the tube 6 and the tube is expanded and joined to the fin 7. 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 a copper tube with an aluminum alloy from the viewpoint of recycling an air conditioner. Similarly, when the tube is made of an aluminum alloy, the heat exchanger is manufactured by mechanically expanding the fin and the tube and joining them by torch brazing.

  Compared to the case of using a conventional copper tube, the heat exchanger in which the tube is made of an aluminum alloy has a problem that penetration corrosion occurs in the R bend portion and the U bend portion that are not in contact with the fins. It was. Therefore, as described in Patent Document 1, a tube material in which the surface of an extruded tube is coated with pure Al having a purity of 99.0% or more, a tube material coated with an Al-1% Zn material, and a tube material sprayed with Zn are used. As a result, pure Al, Al-1% Zn material, and pure Zn coated on the surfaces of these tubes act as sacrificial anode materials, and can prevent penetration corrosion of the R bend part and U bend part not in contact with the fins. I understood.

  However, when these clad tubes and Zn sprayed tubes are used, there has been a problem that penetration corrosion leakage occurs at the joint portion of the torch brazing portion of the tube. As shown in FIG. 7, this through-corrosion leakage is caused by the pure Al layer and Al-1% Zn layer acting as sacrificial anode materials in the R bend and U bend portions, and the portion around the torch brazing portion. Since this material is more easily corroded and dissolved than the material, this portion is preferentially corroded and generated. 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 2, 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.

Japanese Patent Laid-Open No. 02-190485 JP 58-163572 A

  The present invention has been made in view of the above-described problems in the prior art, and an object thereof is to provide a bonding method in which good torch brazing performance and preferential corrosion of a brazed portion are prevented and through leakage does not occur at an early stage.

  In order to solve such a problem, the present invention prepares two pipe materials in which an outer surface of a core material made of an Al alloy is provided with a clad layer made of an Al—Zn alloy, and In the method of expanding the end portion, inserting the other tube material into the expanded portion, and joining both the tube materials by torch brazing, the cladding layer is made of the balance unavoidable impurities of Zn 0.50 wt% to 1.00 wt%, In addition, a brazing material having a thickness of 50 μm to 100 μm and used for torch brazing is an Al alloy made of Si 11.0 wt% to 13.0 wt%, Zn 1.0 wt% to 2.0 wt%, and the remainder unavoidable impurities. There was a method for joining pipe materials characterized in that the torch brazing was held for 3 to 8 seconds after reaching 600 ° C. Further, in claim 2, when the brazing material is a wire brazing material, the diameter is A (μm), and the clad layer thickness of both the pipe materials is B (μm), 15 <A / B <30 The relationship was established.

Further, according to the third aspect of the present invention, two tubes having a Zn sprayed layer provided on the outer surface of a core material made of an Al alloy are prepared, the end of one tube is expanded, and the other tube is inserted into the expanded portion. In the method of joining both pipe materials by brazing, the Zn adhesion amount in the Zn sprayed layer is 10.0 to 18.0 g / m ² , and 400 ° C. is applied to the pipe material on which the Zn sprayed layer is formed before torch brazing. Preheating treatment is performed at a temperature of ˜500 ° C. for 1 to 8 hours, and 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 remainder is inevitable It was an Al alloy made of impurities, and the method for joining pipes was characterized in that the torch brazing was held for 3 to 8 seconds after reaching 600 ° C.

  According to the present invention, good torch brazing is achieved, and preferential corrosion of the brazed portion and early occurrence of through-hole corrosion are prevented.

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 the 1st embodiment of this invention. It is sectional drawing which shows typically the corrosion progress in the 1st embodiment of this invention. It is sectional drawing explaining the electric potential state of the junction part in the 2nd embodiment of this invention. It is sectional drawing which shows typically the corrosion progress in the 2nd embodiment of this invention. It is sectional drawing explaining joining of a tube and a fin. It is sectional drawing which shows the preferential corrosion of a junction part.

A. Mechanism of through-leakage phenomenon When the clad pipe material is joined by torch brazing, the present inventors have found that the sacrificial material of the clad pipe material preferentially corrodes at the joint and leads to through-leakage, or the Zn sprayed pipe material is torch brazed. The mechanism of the phenomenon in which the Zn-concentrated layer generated in the braze filler fillet at the joint leads to preferential corrosion and leads to through leakage when joined by the above method was investigated. 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 layer 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, before the torch brazing, the Zn concentration of the Zn sprayed layer on the surface of the tube material is previously reduced.

  In the present invention, a pipe material is used in which a coating layer made of Al—Zn alloy or Zn is provided on the outer surface of a core material made of Al alloy. As the coating layer, a cladding layer, a Zn sprayed layer, a Zn plating layer, a Zn substitution treatment layer, or the like is used.

B. Embodiments using cladding layer as covering layer First, the configuration according to the first embodiment using the clad layer as a coating layer, described in detail below.
B-1. As shown in FIG. 1, the pipe material 1 having an expanded end portion and the pipe material 2 inserted into the expanded portion are each composed of a core material 4 and a clad layer 3 clad on the outside thereof. Any of the cladding layers is an Al—Zn-based alloy having Al, 0.50 wt% to 1.00 wt% Zn, and the remainder of inevitable impurities and having a thickness of 50 μm to 100 μm. 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-2. Core material In the present invention, the core material component of the pipe material is not particularly limited, but an alloy that shows an electric potential at which an Al-Zn clad layer, which will be described later, can be subjected to sacrificial corrosion protection and that 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.

B-3. The clad layer formed outside the clad layer core material is an Al—Zn alloy. Al, 0.50 wt% to 1.00 wt% Zn, and the remainder of the unavoidable impurities are used as components. The thickness of the cladding layer is 50 μm to 100 μm. By adding Zn to the cladding layer, the pitting corrosion potential of the cladding layer itself is reduced. The core material is prevented from corrosion by the pitting corrosion potential difference with the core material, and the penetration life of the tube material itself is extended. When the Zn content is less than 0.50 wt%, this effect is insufficient in the R bend portion and U bend portion where the sacrificial anticorrosive effect of the fin is not exhibited. On the other hand, if the Zn content exceeds 1.00 wt%, the amount of corrosion and dissolution of the sacrificial material increases and the penetrating life at the above-mentioned site is shortened. Examples of unavoidable impurities include 0.4 wt% or less of Si, 0.7 wt% or less of Fe, and the like.

  The clad layer thickness is 50 μm to 100 μm. When the thickness of the cladding layer is less than 50 μm, the sacrificial anticorrosive effect of the cladding layer is not sufficiently exhibited in the R bend portion and the U bend portion, and the penetration life is 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. To do.

B-4. 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.

B-5. 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 content of Zn in the brazing material is less than 1.0 wt%, the amount of liquid phase at the brazing temperature decreases, so that the brazing material dissolved in the torch brazing portion cannot completely erode the cladding layer. As a result, since the cladding layer remains, preferential corrosion of the 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. In this case, a relationship of 15 <A / B <30 is preferable when the diameter of the wire brazing material is A (μm) and the thickness of the cladding layer of the tube is B (μm). When A / B is 15 or less, the clad layer thickness is larger than the brazing material supply amount, and therefore, the extinction of the clad layer may be insufficient at the torch brazed portion. As a result, the corrosion resistance of the joint is inferior. On the other hand, when A / B is 30 or more, the clad layer can erode in the torch brazing part, but since the thickness of the clad layer is small with respect to the supply amount of the brazing material, the general part other than the torch brazing part ( The corrosion resistance of the R bend part and the U bend part may be inferior. The wire brazing material cast to a predetermined component is heated to 400 ° C., extruded through a billet into a round bar shape, and drawn through a die to produce a wire having a predetermined diameter.

B-6. 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.

C. Embodiments with Zn thermally sprayed layer as a coating layer will now be described in detail below for each configuration according to the second embodiment of the present invention using the Zn thermally sprayed layer as a coating layer, portions different from the first embodiment only explain.

Since the pitting corrosion potential of Zn sprayed on the surface of the tube material is lower than the pitting corrosion potential of the tube material, the Zn sprayed layer acts as a sacrificial anticorrosion layer on the tube material, thereby extending the penetration life of the tube material itself. However, preferential corrosion is generated by forming a Zn-enriched layer in the torch brazing part. As a result, penetration leakage occurs early in the torch brazing part. In order to prevent this, in the present invention, the Zn concentration of the Zn sprayed layer on the surface of the pipe material is previously reduced. Specifically, the deposited amount of Zn to be sprayed is 10.0 to 18.0 g / m ² , and before torch brazing, the Zn sprayed tube material is heated to 400 ° C. to 500 ° C. for 1 to 8 hours. A preheating treatment is performed.

C-1. Tube material 3 is the same as the first embodiment except that 3 shown in FIG. 1 is a Zn sprayed layer.

C-2. Is not particularly limited core component of the core material a second embodiment, the alloy sprayed Zn layer exhibits a potential capable of sacrificial protection or brazing does not melt during attachment alloy. Specifically, an Al—Mn alloy is desirable. When the pipe material does not require a high strength, a JIS 3003 alloy is used. When a high strength is required, a JIS 3105 alloy having a relatively large amount of Cu is used. Alternatively, Al-1% Mn-0.5% Cu alloy or the like is used.

C-3. The amount of Zn sprayed layer Zn deposited is 10.0 to 18.0 g / m ² . When the sprayed Zn deposition amount is less than 10.0 g / m ² , the sprayed Zn deposition amount is small, and the entire core surface cannot be covered. As a result, the sacrificial anticorrosive effect of sprayed Zn cannot be exhibited. On the other hand, if it exceeds 18.0 g / m ² , a large amount of Zn remains and a Zn-enriched layer is still formed even if Zn diffuses in the subsequent preheating treatment. As a result, preferential corrosion of the joint cannot be prevented.

  The tube material sprayed with Zn is subjected to a preheating treatment at a temperature of 400 ° C. to 500 ° C. for 1 to 8 hours before torch brazing. When the preheating temperature of the tube material is lower than 400 ° C., the Zn concentration layer is formed in substantially the same manner as when the Zn diffusion amount is small and Zn is thermally sprayed. As a result, preferential corrosion occurs at the torch brazing part. On the other hand, when the heating temperature exceeds 500 ° C., the diffusion of Zn proceeds, the surface Zn concentration becomes low, and the preferential corrosion of the torch brazing part is reduced. However, since the sacrificial anticorrosive ability in other R bend parts and U bend parts is inferior, penetration is reached early.

  In the present invention, the preheating time is 1 to 8 hours. If it is less than 1 hour, the diffusion of Zn does not proceed sufficiently, and a Zn-enriched layer is still formed in the torch brazing portion, so that preferential corrosion occurs. When the time exceeds 8 hours, Zn diffusion sufficiently proceeds and the surface Zn concentration becomes low, so that the preferential corrosion of the torch brazing portion can be reduced. However, since the sacrificial anticorrosive ability in other R bend parts and U bend parts is inferior, it leads to penetration early.

C-4. Production of tube material A tube material is produced as follows. 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 predetermined adhesion amount of Zn is sprayed through the Zn spray gun. Next, preheating treatment is performed at 400 to 500 ° C. for 1 to 8 hours. In this manner, a Zn spray tube having a predetermined outer diameter and inner diameter was produced.

C-5. Torch brazing material As a component of the torch brazing material, an Al—Si—Zn alloy of Si 11.0 wt% to 13.0 wt% and Zn 1.0 wt% to 2.0 wt% is used. The Si content is the same as in the first embodiment. When the Zn content is less than 1.0 wt%, the potential difference between the Zn enriched layer and the brazing filler metal portion becomes large, and therefore, the preferential corrosion of the Zn enriched layer occurs at the joint. If it exceeds 2.0 wt%, the amount of Zn contained in the brazing filler metal layer formed after brazing will increase, so that the brazing filler metal layer itself will corrode and dissolve, and the brazing filler metal layer will corrode and dissolve and penetrate at the joint. Causes corrosion. Therefore, the amount of Zn contained in the torch brazing material was defined as 1.0 wt% to 2.0 wt%.

C-6. Torch Brazing Torch brazing method and conditions are the same as in the first embodiment. When the holding time after reaching 600 ° C. is less than 3 seconds, heat does not spread uniformly to the torch brazing part, and brazing becomes incomplete.

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

Invention Example No. 1-11 and Comparative Example No. 12-20
First, an example of the first embodiment will be described.
Table 1 shows the components and wire diameters of the wire brazing material, the thickness and Zn content of the clad layer that is a sacrificial material for the tube material, and the brazing conditions (temperature and time).
The wire brazing material was cast into a predetermined component, extruded onto a round bar, and then drawn through a die to prepare a wire rod having a predetermined diameter.
The tube material was prepared as follows. 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 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 property evaluation After cutting the cross-section of the joint specimen and polishing and filling with resin, ○ indicates that the joint was present over 10 mm or more, ○ indicates that it is 5 mm or more and less than 10 mm, and Δ indicates less than 5 mm. . ○ and Δ were accepted and x was rejected.

(2) Corrosion test As a corrosion test of the joint, the end of the joint test piece was masked with a masking tape and an adhesive, and then a CASS test according to JISH8601 was performed for 2000 h. After the test, the corrosion products were removed with concentrated nitric acid and phosphoric acid-chromic acid mixed solution, and then the corrosion depths of the joined portion and the non-joined portion were measured by the depth of focus method. When the corrosion depth does not penetrate, the corrosion resistance is considered good, and when the corrosion depth occurs, it is judged as defective.

  Table 1 shows the evaluation results of the brazing property and the corrosion test. As can be seen from Table 1, Example No. of the present invention. In 1 to 11, the brazing property was acceptable, and the corrosion resistance of the joined portion and the non-joined portion was also good.

  In Example 10 of the present invention, A / B <15, so the corrosion resistance at the joint was slightly inferior to Examples 1-9. Moreover, in Example 11 of the present invention, since A / B> 30, the sacrificial anticorrosive effect at the non-joined part was slightly inferior to Examples 1-9.

  In Comparative Example 12, the Zn content in the clad layer was small, and the sacrificial anticorrosive effect at the non-joined part was poor. Moreover, in Comparative Example 13, the Zn content in the cladding layer was large, and the sacrificial anticorrosive effect at the non-joined part was poor.

Comparative Example No. In No. 14, since the Si content of the brazing wire was less than the range of the present invention, the liquidus temperature of the brazing material was lowered, so that the brazing property of the torch brazing part was rejected.
Comparative Example No. In No. 15, since the Si content of the brazing wire exceeded the range of the present invention, the liquidus temperature of the brazing material was lowered, and the brazing property of the torch brazing part was rejected.
Comparative Example No. In No. 16, since the Zn content of the brazing material wire is less than that of the present invention, the solidus temperature of the brazing material becomes high and the brazing of the brazing layer becomes insufficient. As a result, the clad layer remained at the joint, the clad layer was preferentially corroded, and penetration corrosion occurred at the joint.
Comparative Example No. In No. 17, since the Zn content of the brazing material wire exceeded the present invention, the clad layer did not remain in the joint portion, but the amount of corrosion of the brazing material increased, so that penetration corrosion occurred in the joint portion.
Comparative Example No. In No. 18, since the brazing time was less than 3 seconds at 600 ° C., the clad layer remained in the joint, and that part was preferentially corroded in the corrosion test, resulting in penetration corrosion in the joint.
Comparative Example No. In No. 19, since the brazing time exceeded 8 seconds at 600 ° C., the pipe material was excessively eroded by the brazing material at the joint, and the brazing property was unacceptable.
Comparative Example No. In No. 20, since the brazing temperature was less than 600 ° C., the brazing did not flow sufficiently and the brazing property was unacceptable.

Invention Example No. 21-28 and Comparative Example No. 29-41
Next, an example of the second embodiment will be described.
Table 2 shows the components of the wire brazing material, the Zn spraying amount in the Zn sprayed layer, the preheating conditions of the Zn sprayed tube material, and the brazing conditions (temperature and time).
The wire brazing material was cast into a predetermined component, extruded onto a round bar, and then drawn through a die to prepare a wire rod having a predetermined diameter.
The pipe material was produced as follows. 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 shown in Table 1 was produced through the Zn spray gun. The Zn thermal spray tube was subjected to the heat treatment shown in Table 1. 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 torch brazing was performed using a wire brazing material to obtain a joining test piece.

  About the obtained joining test piece, it carried out similarly to Example 1, and evaluated by brazing property evaluation and a corrosion test. The results of brazeability evaluation and corrosion test are shown in Table 2. As can be seen from Table 2, Example No. of the present invention. In Nos. 21 to 28, the brazing property was acceptable, and the corrosion resistance of the joined portion and the non-joined portion was also good.

In Comparative Example 29, since the amount of sprayed Zn was less than the range of the present invention, penetration corrosion occurred at the non-joined portion. In Comparative Example 30, since the amount of sprayed Zn was large, penetration corrosion occurred at the joint.
In Comparative Example 31, through-corrosion occurred at the joint because the preheating temperature of the pipe material was low. In Comparative Example 32, since the preheating temperature of the pipe material was high, penetration corrosion occurred at the non-joined portion.
In Comparative Example 33, since the preheating time of the pipe material was short, penetration corrosion occurred at the joint. In Comparative Example 34, since the preheating time of the pipe material was long, penetration corrosion occurred at the non-joined portion.
Comparative Example No. In No. 35, 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 the brazing condition of the torch brazing part was poor.
Comparative Example No. In No. 36, since the amount of Si in the brazing wire exceeded that of the present invention, the liquidus temperature of the brazing material was lowered and the brazing condition of the torch brazing part was poor.
Comparative Example No. In No. 37, 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, and penetration occurred in the joint.
Comparative Example No. In No. 38, the amount of Zn in the brazing material wire exceeded that of the present invention, so the amount of Zn in the brazing material increased, the amount of corrosion increased, and penetration occurred in the joint.
Comparative Example No. In No. 39, since the brazing temperature was lower than that of the present invention, the brazing property was poor.
Comparative Example No. At 40, the brazing time of the torch brazing part was poor because the brazing time was less than the present invention.
Comparative Example No. In No. 41, since the brazing time exceeded the present invention, the brazing of the torch brazing part was poor.

  As described above, according to the present invention, it is possible to obtain good jointability of the joint portion by torch brazing and good corrosion resistance in the joint portion and other general portions.

DESCRIPTION OF SYMBOLS 1 ... Tube material 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 …… corroded Zn enriched layer portion 6 …… Tube 7 …… Fin 8 …… Jig for expansion

Claims (3)

  Prepare two tubes with an Al-Zn alloy clad layer on the outer surface of an Al alloy core, expand the end of one tube, and insert the other tube into the expanded portion. In the method of joining both pipes by brazing, the clad layer is composed of 0.50 wt% to 1.00 wt% of Zn, the balance is inevitable impurities, and has a thickness of 50 μm to 100 μm, and will be used for torch brazing. The material is an Al alloy composed of Si 11.0 wt% to 13.0 wt%, Zn 1.0 wt% to 2.0 wt% and the remaining inevitable impurities, and held for 3 to 8 seconds after the torch brazing reaches 600 ° C. A method for joining pipe materials, characterized in that:   The relation of 15 <A / B <30 is established when the brazing material is a wire brazing material, the diameter thereof is A (μm), and the clad layer thickness of both pipe materials is B (μm). 2. The method for joining pipe materials according to 1. Prepare two tubes with Zn sprayed layer on the outer surface of the core material made of Al alloy, expand the end of one tube, insert the other tube into the expanded portion, and torch both tubes by torch brazing In the bonding method, the Zn deposition amount in the Zn sprayed layer is 10.0 to 18.0 g / m ² , and the tube material on which the Zn sprayed layer is formed at a temperature of 400 ° C. to 500 ° C. before the torch brazing. Pre-heating treatment for 1 to 8 hours is performed, and the brazing material used for torch brazing is an Al alloy composed of Si 11.0 wt% to 13.0 wt%, Zn 1.0 wt% to 2.0 wt%, and the balance non-avoidable impurities. A method for joining pipe materials, characterized in that the brazing is held for 3 to 8 seconds after the torch brazing reaches 600 ° C.

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