JP4452561B2 - High corrosion resistance tube for heat exchanger and heat exchanger - Google Patents

Description

  The present invention is capable of reducing the corrosion depth of a tube and is excellent in corrosion resistance, and is not affected by slight fluctuations in brazing conditions, and can be produced industrially and efficiently. Regarding the exchanger.

  In this specification, the term “aluminum” is used to include aluminum and its alloys. Further, in this specification, the expression “Al” means aluminum (a metal simple substance).

  As an aluminum heat exchanger, a structure in which a plurality of flat tubes are laminated in the thickness direction with fins interposed therebetween, and a hollow header is connected to both ends of these tubes in a known manner is known. The flat tube and the fin are joined and integrated by brazing. If such an aluminum heat exchanger continues to be used as it is, pitting corrosion will occur in the tube, this will reach the inner surface of the tube and penetrate, and the function as a heat exchanger will be impaired. Conventionally, sacrificial anticorrosion (formation of a sacrificial corrosion layer) is performed by forming a Zn sprayed layer on the surface of the tube and diffusing Zn on the surface (see, for example, Patent Documents 1 and 2).

  In the method of preventing corrosion by forming such a sacrificial corrosion layer, the corrosion depth is almost determined by the thickness of the sacrificial corrosion layer. There was a need to control. At this time, the main factors affecting the thickness of the sacrificial corrosion layer are the heat treatment conditions and the diffusion coefficient of Zn. Therefore, the thickness of the sacrificial corrosion layer can be reduced by slightly changing the heat treatment conditions during brazing. Since it fluctuated significantly, it was not easy to stably and efficiently manufacture a high-quality tube excellent in corrosion resistance.

As a technique for controlling the thickness of the sacrificial corrosion layer formed by diffusion of Zn or the like, a technique for shortening the brazing time, a technique for brazing at a low temperature, and the like have been proposed (see Non-Patent Document 1). .
JP-A-4-15496 JP-A-2-46913 Nakamura et al., “Ultra-Thin and Light-Weight RS Evaporator”, SAE TECHNICAL PAPER SERIES (2003 SAE World Congress), USA, SAE International March 2003, 2003-01-0527

  However, it is difficult to reliably achieve a good brazing joint with the above-described method for shortening the brazing time, while the method for brazing at a low temperature is to achieve a good brazing joint. Had to be heat-treated for a longer time, and had a problem of poor productivity.

  The present invention has been made in view of such a technical background, and is capable of reducing the corrosion depth of a tube and is excellent in corrosion resistance, and is not affected by slight fluctuations in brazing conditions. An object of the present invention is to provide a highly corrosion-resistant tube for heat exchanger and a heat exchanger that can be efficiently produced efficiently.

  In order to achieve the above object, the present invention provides the following means.

[1] In a heat exchanger tube in which a sacrificial corrosion layer is provided on the surface of an aluminum tube core,
The aluminum tube core material is a metal having a higher potential than Al as a metal mainly added to give a relative potential difference between the sacrificial corrosion layer and the tube core material. A metal element having a diffusion coefficient in aluminum of 1 × 10 ⁻⁹ cm ² / sec or less,
A high corrosion resistance tube for a heat exchanger, wherein a relative potential difference between the surface of the sacrificial corrosion layer and an intermediate position in the thickness direction of the tube core material is 30 to 250 mV.

[2] In a heat exchanger tube in which a sacrificial corrosion layer is provided on the surface of an aluminum tube core,
The aluminum tube core material is a metal having a higher potential than Al as a metal mainly added to give a relative potential difference between the sacrificial corrosion layer and the tube core material. A metal element having a diffusion coefficient in aluminum of 1 × 10 ⁻¹⁰ cm ² / sec or less,
A high corrosion resistance tube for a heat exchanger, wherein a relative potential difference between the surface of the sacrificial corrosion layer and an intermediate position in the thickness direction of the tube core material is 30 to 250 mV.

[3] A metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C. is made of Mn, Cr, and Zr. 2. The high corrosion resistance tube for a heat exchanger according to item 1, wherein the tube is one or more metals selected from the group.

[4] Mn is used as a metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less of the metal element at 600 ° C. in aluminum. 2. The high corrosion resistance tube for a heat exchanger as described in 1 above, wherein the Mn content in the tube core material is 0.5 to 2.5 mass%.

  [5] The high corrosion resistance tube for a heat exchanger according to the item 4, wherein the Mn content in the aluminum tube core is 0.8 to 2% by mass.

  [6] The highly corrosion-resistant tube for a heat exchanger as described in [4] above, wherein the Mn content in the aluminum tube core is 0.5% by mass or more and less than 1% by mass.

  [7] The high corrosion resistance tube for a heat exchanger according to the above item 4, wherein the Mn content in the aluminum tube core is more than 1.5% by mass and 2% by mass or less.

  [8] The aluminum tube core material according to any one of 4 to 7 above, wherein the aluminum tube core material contains Cu, and the Cu content in the aluminum tube core material is more than 0 and 0.6% by mass or less. High corrosion resistance tube for heat exchanger.

  [9] The aluminum tube core material according to any one of the above items 4 to 7, wherein the aluminum tube core material contains Cu, and the Cu content in the aluminum tube core material is more than 0 and 0.4 mass% or less. High corrosion resistance tube for heat exchanger.

[10] Cr is used as a metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less of the metal element at 600 ° C. in aluminum. 2. The high corrosion-resistant tube for heat exchangers according to item 1 above, wherein the Cr content in the tube core material is 0.3 to 2% by mass.

[11] Zr is used as a metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C. 2. The high corrosion-resistant tube for heat exchanger according to item 1, wherein the Zr content in the tube core material is 0.3 to 5% by mass.

  [12] The high corrosion resistance for a heat exchanger according to any one of items 1 to 11, wherein the additive metal of the sacrificial corrosion layer is one or more metals selected from the group consisting of Zn, In, and Sn. tube.

  [13] The high corrosion resistance tube for a heat exchanger according to any one of the above items 1 to 11, wherein the additive metal of the sacrificial corrosion layer is Zn, and the surface Zn concentration in the sacrificial corrosion layer is 1.5% by mass or less. .

  [14] The high corrosion resistance tube for a heat exchanger as described in [13] above, wherein the surface Zn concentration in the sacrificial corrosion layer is 1.2 mass% or less.

  [15] The high corrosion resistance tube for a heat exchanger according to any one of the above items 1 to 14, wherein a relative potential difference between the surface of the sacrificial corrosion layer and an intermediate position in the thickness direction of the tube core material is 40 to 150 mV.

  [16] The high corrosion-resistant tube for a heat exchanger as described in any one of 1 to 15 above, wherein the thickness of the sacrificial corrosion layer is 20 to 150 μm.

  [17] The high corrosion-resistant tube for a heat exchanger according to any one of items 1 to 15, wherein the sacrificial corrosion layer has a thickness of 20 to 50 μm.

  [18] The high corrosion-resistant tube for a heat exchanger according to any one of items 1 to 17, wherein the tube core material is formed by extrusion.

  [19] The high corrosion resistance tube for a heat exchanger according to any one of the aforementioned Items 1 to 18, wherein the sacrificial corrosion layer is formed by thermal spraying.

  [20] The high corrosion resistance tube for a heat exchanger as recited in the aforementioned Item 13 or 14, wherein the sacrificial corrosion layer is formed by spraying an Al—Zn alloy.

  [21] The heat according to item 13 or 14, wherein the sacrificial corrosion layer is formed by spraying an Al—Zn alloy wire, and the Zn content in the Al—Zn alloy is 1 to 4 mass%. High corrosion resistance tube for exchangers.

  [22] A plurality of tubes each having a sacrificial corrosion layer provided on the surface of an aluminum tube core are laminated with fins interposed therebetween, and the tubes and the fins are joined together by brazing. In the heat exchanger in which a hollow header is connected in communication with both ends of the tube, the high corrosion resistance tube for a heat exchanger described in any one of the preceding items 1 to 21 is used as the tube. A heat exchanger characterized by

[23] As a metal that is mainly added to impart a relative potential difference between the sacrificial corrosion layer and the tube core material, the metal element has a higher potential than Al, and the metal element in aluminum at 600 ° C. An aluminum heat exchanger tube is formed by forming a sacrificial corrosion layer of metal lower than Al on the surface of an aluminum tube core containing a metal having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less. Manufacturing process,
Assembling fins to the heat exchanger tube;
And a step of brazing and joining the tube and the fin by heating at a predetermined temperature in the assembled state.

In the invention of [1], the aluminum tube core material is a metal having a higher potential than Al as a metal that is mainly added to give a relative potential difference between the sacrificial corrosion layer and the tube core material. The metal element at 600 ° C. contains a metal whose diffusion coefficient in aluminum is 1 × 10 ⁻⁹ cm ² / sec or less (hereinafter sometimes simply referred to as “potential noble metal”). The potential noble metal in the tube core material can be prevented from diffusing into the sacrificial corrosion layer, thereby causing a steep potential gradient in the tube thickness direction in the vicinity of the interface between the sacrificial corrosion layer and the tube core material. Since it can be applied (see FIG. 4B), the progress of corrosion can be prevented at the boundary region between the sacrificial corrosion layer and the tube core material. Moreover, since the relative potential difference between the surface of the sacrificial corrosion layer and the intermediate position in the thickness direction of the tube core material is set in the range of 30 to 250 mV, the sacrificial corrosion layer is preferentially corroded effectively (at an appropriate speed). Therefore, the tube has excellent corrosion resistance. Furthermore, since it can be produced industrially efficiently without being affected by slight fluctuations in brazing conditions, a tube with stable quality can be manufactured at low cost.

In the invention of [2], the aluminum tube core material is a metal having a higher potential than Al as a metal mainly added to impart a relative potential difference between the sacrificial corrosion layer and the tube core material. Since the diffusion coefficient of the metal element in aluminum at 600 ° C. is a metal containing 1 × 10 ⁻¹⁰ cm ² / sec or less, the potential noble metal in the tube core is sacrificial corrosion. Since diffusion into the layer can be sufficiently suppressed, a steeper potential gradient can be applied in the tube thickness direction in the vicinity of the interface between the sacrificial corrosion layer and the tube core (see FIG. 4B). The progress of corrosion can be prevented at the boundary region between the sacrificial corrosion layer and the tube core material. Moreover, since the relative potential difference between the surface of the sacrificial corrosion layer and the intermediate position in the thickness direction of the tube core material is set in the range of 30 to 250 mV, the sacrificial corrosion layer is preferentially corroded effectively (at an appropriate speed). Therefore, the tube has excellent corrosion resistance. Furthermore, since it can be produced industrially efficiently without being affected by slight fluctuations in brazing conditions, a tube with stable quality can be manufactured at low cost.

  In the invention of [3], since the diffusion of the potential noble metal in the tube core material into the sacrificial corrosion layer is further suppressed, the progress of corrosion is surely prevented at the boundary region between the sacrificial corrosion layer and the tube core material. be able to.

  In the invention of [4], the relative potential difference becomes more appropriate, and the sacrificial corrosion layer is preferentially corroded more effectively (at an appropriate rate).

  In the invention of [5], since the Mn content in the core material is set to 0.8 to 2% by mass, the relative potential difference becomes more appropriate, and the sacrificial corrosion layer becomes more effective (appropriate) Will be preferentially corroded (at speed).

  In the invention of [6], since the Mn content in the core material is set to be 0.5% by mass or more and less than 1% by mass, the extrudability of the tube is improved and the manufacture of the multi-hole fine tube is facilitated. There are advantages.

  In the invention of [7], since the Mn content in the core material is set to more than 1.5% by mass and 2% by mass or less, the high temperature strength of the tube is improved.

  In the invention of [8], since the Cu content in the core material is more than 0 and 0.6% by mass or less, a steep potential gradient in the vicinity of the interface between the sacrificial corrosion layer and the tube core material is prevented. And corrosion resistance can be further improved.

  In the invention of [9], since the Cu content in the core material is more than 0 and not more than 0.4 mass%, it is ensured that the steep potential gradient near the interface between the sacrificial corrosion layer and the tube core material becomes gentle. Therefore, the corrosion resistance can be further improved.

  In the invention of [10], the relative potential difference becomes more appropriate, and the sacrificial corrosion layer is preferentially corroded more effectively (at an appropriate rate).

  In the invention of [11], the relative potential difference becomes more appropriate, and the sacrificial corrosion layer is preferentially corroded more effectively (at an appropriate rate).

  In the invention of [12], the additive metal of the sacrificial corrosion layer is one or more metals selected from the group consisting of Zn, In, and Sn, and these metals are sufficiently lower than aluminum tubes. Since it is a metal, the relative potential difference between the sacrificial corrosion layer surface and the intermediate position in the thickness direction of the tube core material can ensure a relatively large relative potential difference in the range of 30 to 250 mV, so that it is more excellent in corrosion resistance. It becomes a tube.

  In the invention of [13], since the additive metal of the sacrificial corrosion layer is Zn and the surface Zn concentration in the sacrificial corrosion layer is 1.5 mass% or less, the corrosion rate can be suppressed, and the sacrificial corrosion layer thickness is reduced. (Corrosion depth) can be reduced.

  In the invention of [14], the corrosion resistance can be further improved.

  In the invention of [15], since the relative potential difference between the surface of the sacrificial corrosion layer and the intermediate position in the thickness direction of the tube core material is set to 40 to 150 mV, there is an advantage that the corrosion resistance can be further improved.

  In the invention of [16], the corrosion depth can be reduced as compared with the prior art.

  In the invention of [17], the corrosion depth can be further reduced as compared with the prior art.

  In the invention of [18], since the production efficiency is improved, a high-quality heat exchanger tube is provided at a low cost.

  In the invention of [19], since the sacrificial corrosion layer is formed by thermal spraying, the production efficiency is good, thereby providing a high-quality heat exchanger tube at a lower cost.

  In the invention of [20], since the sacrificial corrosion layer is formed by thermal spraying of the Al—Zn alloy, the Zn content and the surface Zn concentration in the sacrificial corrosion layer can be strictly controlled, thereby improving the tube quality. Can be improved more.

  In the invention [21], since the Zn content in the Al—Zn alloy used for thermal spraying is 1 to 4% by mass, the corrosion resistance of the tube can be further improved.

[22] In the invention of [22], the aluminum tube core material is a metal having a potential higher than that of Al as a metal mainly added to impart a relative potential difference between the sacrificial corrosion layer and the tube core material. Since the diffusion coefficient of the metal element in aluminum at 600 ° C. is 1 × 10 ⁻⁹ cm ² / sec or less, the potential noble metal in the tube core is sacrificial corrosion. Diffusion in the layer can be suppressed, whereby a steep potential gradient can be applied in the tube thickness direction in the vicinity of the interface between the sacrificial corrosion layer and the tube core material (see FIG. 4B). Can be prevented at the boundary region between the sacrificial corrosion layer and the tube core. Moreover, since the relative potential difference between the surface of the sacrificial corrosion layer and the intermediate position in the thickness direction of the tube core material is set in the range of 30 to 250 mV, the sacrificial corrosion layer is preferentially corroded effectively (at an appropriate speed). As a result, a high-quality heat exchanger with excellent durability can be provided.

  In the invention of [23], it is possible to manufacture a high-quality heat exchanger that is excellent in the corrosion resistance of the tube and excellent in durability.

  FIG. 1 is a front view showing a heat exchanger according to an embodiment of the present invention. This heat exchanger (1) is used as a condenser and evaporator for a refrigeration cycle in a car air conditioner for an automobile, and constitutes a multiflow type heat exchanger.

  That is, this heat exchanger (1) is composed of a plurality of flat tubes along a horizontal direction as a heat exchange conduit between a pair of left and right hollow headers (4) (4) along a vertical direction arranged in parallel. (2) are arranged in parallel with both ends communicating with both hollow headers (4) and (4), and corrugated fins (3) between these tubes (2) and outside the outermost tube. ) And a side plate (10) is arranged outside the outermost corrugated fin (3).

  As shown in FIGS. 2 and 3, the tube (2) is made of a hollow extruded material of aluminum, and the inside thereof is divided into a plurality of refrigerant flow paths (2b) by partition walls (2a) continuously extending in the length direction. It is divided. The tube (2) is formed by a tube core (6) made of an aluminum hollow extruded material, and a sacrificial metal diffused on the surface of the tube core (6). It consists of a corrosive layer (7). The corrugated fin (3) is made of an aluminum brazing material clad with a brazing material. Then, the tube (2) and the fin (3) are heated in the furnace in a state where the tubes (2) and the fins (3) are alternately laminated and assembled (temporarily assembled), and the tubes (2) and the fins (3) are brazed. Are brazed and joined.

In the heat exchanger (1), the aluminum tube core (6) is provided with a relative potential difference between the sacrificial corrosion layer surface (7a) and the intermediate position (6a) in the thickness direction of the tube core. As a metal to be added mainly, a metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C. The outer surface (7a) of the sacrificial corrosion layer (7) and the intermediate position in the thickness direction of the tube core (6) (position for dividing the thickness into two equal parts) (6a) The relative potential difference is set in the range of 30 to 250 mV. The “relative potential difference” is a value measured after brazing.

As described above, the aluminum tube core (6) is a metal having a higher potential than Al as a metal that is mainly added to impart the above-described relative potential difference, and in the aluminum of the metal element at 600 ° C. Therefore, the potential noble metal in the tube core material (6) is a sacrificial corrosion layer (7) made of aluminum, because the diffusion coefficient of the metal is one containing a metal having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less. ) Can be suppressed, whereby a steep potential gradient can be applied in the tube thickness direction in the vicinity of the interface between the sacrificial corrosion layer (7) and the tube core (6) (see FIG. 4B). Therefore, the progress of corrosion can be prevented at the boundary region between the sacrificial corrosion layer (7) and the tube core (6). Moreover, since the relative potential difference between the sacrificial corrosion layer surface (7a) and the intermediate position in the thickness direction of the tube core (6) is set in the range of 30 to 250 mV, the sacrificial corrosion layer is effective (at an appropriate speed). In this case, the tube (2) is excellent in corrosion resistance because it is preferentially corroded.

The diffusion coefficient of the metal element in aluminum at 600 ° C. of the metal (metal added to the aluminum tube core material (6) having a higher potential than Al) is 1 × 10 ^−9. If it exceeds cm ² / sec, the metal diffuses largely in the sacrificial corrosion layer (7) due to heating during brazing, and therefore, in the vicinity of the interface between the sacrificial corrosion layer (7) and the tube core (6). A steep potential gradient cannot be applied in the tube thickness direction, and the progress of corrosion does not stop at the boundary region between the sacrificial corrosion layer (7) and the tube core material (6), and the inside of the tube core material (6). Corrosion will progress to the point. In particular, the aluminum tube core (6) is a metal having a potential higher than that of Al, and the diffusion coefficient of the metal element in aluminum at 600 ° C. is 1 × 10 ⁻¹⁰ cm ² / sec or less. It is preferable to contain.

  Further, when the relative potential difference between the sacrificial corrosion layer surface (7a) and the intermediate position (6a) in the thickness direction of the tube core (6) is less than 30 mV, the sacrificial corrosion layer (7) is sacrificed because the potential difference is small. Corrosion cannot be exerted, and corrosion proceeds to the inside of the tube core (6). On the other hand, when the relative potential difference between the sacrificial corrosion layer surface (7a) and the intermediate position (6a) in the thickness direction of the tube core (6) exceeds 250 mV, the potential difference becomes too large and the sacrificial corrosion layer (7). Corrosion rate increases, and the sacrificial corrosion layer (7) is corroded in a short period of time, and the long-term anticorrosion effect of the core material (6) cannot be exhibited. In particular, the relative potential difference between the surface (7a) of the sacrificial corrosion layer (7) and the intermediate position (6a) in the thickness direction of the tube core (6) is preferably set in the range of 40 to 150 mV.

The metal having a higher potential than Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C. is not particularly limited, For example, Mn, Cr, Zr, Fe, Co, Ni etc. are mentioned. Among these, one or more metals selected from the group consisting of Mn, Cr and Zr are preferably used, and Mn is particularly preferable. Note that metals having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻¹⁰ cm ² / sec or less of the metal element at 600 ° C. in aluminum include Mn, Cr, Zr, and the like. Can be mentioned.

In the present invention, a structure in which Mn is used as a metal having a higher potential than Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in the aluminum of the metal element at 600 ° C. In the case of adopting, the Mn content in the aluminum tube core (6) is preferably set to 0.5 to 2.5% by mass. If it is less than 0.5% by mass, the Mn content is too small, and it becomes difficult to form a steep potential gradient in the vicinity of the interface between the sacrificial corrosion layer (7) and the tube core (6). Since corrosion resistance falls, it is not preferable. On the other hand, if it exceeds 2.5% by mass, a large amount of coarse intermetallic compounds are produced and formability is lowered, which is not preferable. Especially, it is more preferable that the Mn content in the aluminum tube core (6) is set to 0.8 to 2% by mass.

  Moreover, it is preferable that Mn content in the said aluminum tube core material (6) is set to 0.5 mass% or more and less than 1 mass% at the point which can improve extrudability. Alternatively, the Mn content in the aluminum tube core (6) is preferably set to more than 1.5% by mass and 2% by mass or less in that the high temperature strength of the tube (2) can be improved. .

In addition, a configuration is adopted in which Cr is used as a metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C. In this case, the Cr content in the aluminum tube core (6) is preferably set to 0.3 to 2% by mass. If it is less than 0.3% by mass, the Cr content is too small, and it becomes difficult to form a steep potential gradient in the vicinity of the interface between the sacrificial corrosion layer (7) and the tube core material (6). Since corrosion resistance falls, it is not preferable. On the other hand, if it exceeds 2% by mass, a large amount of coarse intermetallic compounds are produced and formability is lowered, which is not preferable.

Further, a configuration is adopted in which Zr is used as a metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less of the metal element at 600 ° C. in aluminum. In this case, the Zr content in the aluminum tube core (6) is preferably set to 0.3 to 5% by mass. If it is less than 0.3% by mass, the Zr content is so small that it becomes difficult to form a steep potential gradient in the vicinity of the interface between the sacrificial corrosion layer (7) and the tube core (6). Since corrosion resistance falls, it is not preferable. On the other hand, if it exceeds 5% by mass, a large amount of coarse intermetallic compounds are produced and formability is lowered, which is not preferable.

In this invention, the aluminum tube core (6) is a metal having a potential higher than that of Al, and the diffusion coefficient of the metal element in aluminum at 600 ° C. is 1 × 10 ⁻⁹ cm ² / sec or less. Although a metal is included, another metal such as Cu may be included as long as the effect of the present invention is not impaired. For example, when adopting a configuration in which Cu is contained together with Mn in an aluminum tube core (6), the Cu content is preferably set to more than 0 and 0.6% by mass or less. If the Cu content exceeds 0.6% by mass, the steep potential gradient in the vicinity of the interface between the sacrificial corrosion layer (7) and the tube core material (6) is loosened, which is not preferable. In particular, the Cu content is particularly preferably set to more than 0 and 0.4% by mass or less.

  In the present invention, the additive metal (diffusion metal) of the sacrificial corrosion layer (7) is preferably one or more metals selected from the group consisting of Zn, In and Sn. Since Zn, In, and Sn are all base metals sufficiently lower than aluminum tubes, the relative relationship between the sacrificial corrosion layer surface (7a) and the intermediate position (6a) in the thickness direction of the tube core (6). A relatively large relative potential difference can be ensured even in the range of 30 to 250 mV, thereby further improving the corrosion resistance. Among them, the additive metal (diffusion metal) of the sacrificial corrosion layer (7) is more preferably Zn.

  When the additive metal of the sacrificial corrosion layer (7) is Zn, the surface Zn concentration in the sacrificial corrosion layer (7) is preferably set to 1.5% by mass or less. If it exceeds 1.5% by mass, the corrosion rate of the sacrificial corrosion layer (7) is increased, and the sacrificial corrosion layer (7) is corroded in a short period of time, so that a long-term anticorrosive effect cannot be exhibited. Among them, the surface Zn concentration in the sacrificial corrosion layer (7) is more preferably 1.2% by mass or less, and a particularly preferable range is 0.4 to 1.2% by mass.

  The “surface Zn concentration” is a Zn concentration measured by irradiating an X-ray beam (5 μm diameter) at a position 5 μm from the tube surface using an X-ray microanalyzer (EPMA-8705) manufactured by Shimadzu Corporation. It is. The diameter of the measuring head is 10 μm.

  In the present invention, the thickness of the sacrificial corrosion layer (7) is preferably set to 20 to 150 μm. If the thickness is less than 20 μm, the thickness of the sacrificial corrosion layer (7) becomes too thin, and the sacrificial corrosion layer (7) is corroded in a short period of time, so that a long-term anticorrosive effect cannot be exhibited. On the other hand, if the thickness exceeds 150 μm, the corrosion depth increases from 150 μm and the corrosion depth becomes too deep. Especially, it is more preferable that the thickness of the sacrificial corrosion layer (7) is set to 20 to 50 μm.

  Although the formation method of the said sacrificial corrosion layer (7) is not specifically limited, For example, a clad material, thermal spraying, plating, vapor deposition, sputtering etc. are mentioned. Among these, the sacrificial corrosion layer (7) is preferably formed by thermal spraying, and in this case, there is an advantage that productivity can be improved. When Zn is used as the additive metal of the sacrificial corrosion layer (7), it is preferable to form the sacrificial corrosion layer by spraying an Al—Zn alloy, and it is more preferable to spray the Al—Zn alloy wire. preferable. In this case, the Zn content in the Al—Zn alloy is preferably in the range of 0.1 to 10% by mass. If it is less than 0.1% by mass, it becomes difficult to impart an appropriate potential difference between the sacrificial corrosion layer (7) and the tube core (6), while if it exceeds 10% by mass, the sacrificial corrosion layer (7) The corrosion rate is increased, and the sacrificial corrosion layer (7) is corroded in a short period of time, so that a long-term anticorrosive effect cannot be exhibited, which is not preferable. Especially, it is more preferable that Zn content in the said Al-Zn alloy is the range of 1-4 mass%. In addition, when Al—Zn alloy is sprayed, the degree of evaporation of Zn varies depending on the spraying equipment, spraying conditions, etc., so the alloy composition of the sacrificial corrosion layer (7) varies depending on the spraying equipment, spraying conditions, etc. Accordingly, in order to form the predetermined sacrificial corrosion layer (7), for example, in flame spraying and arc spraying, arc spraying has a higher spraying temperature and Zn tends to evaporate. In this case, an Al—Zn alloy wire rod It is better to increase the Zn content in the (thermal spray alloy wire).

  The technique of thermal spraying is not particularly limited, and examples thereof include a technique using an arc sprayer that has been conventionally used. Further, the thermal spraying may be performed while scanning the spray gun with respect to the tube, or may be sprayed with a fixed spray gun while feeding the coiled aluminum material. Alternatively, the tube may be extruded from the extruder and sprayed continuously immediately after that. In this case, there is an advantage that the production efficiency can be improved. The spraying conditions are not particularly limited. The thermal spraying is preferably performed in a non-oxidizing atmosphere such as a nitrogen atmosphere or an argon atmosphere in order to prevent oxidation of the thermal sprayed layer formed by thermal spraying (oxidation of the sacrificial corrosion layer). Of these, thermal spraying is preferably performed in a nitrogen atmosphere or an argon atmosphere.

  The heat exchanger (1) of this invention is manufactured as follows, for example. That is, in a state where the fin (3) is assembled to the aluminum tube (2) having a sacrificial corrosion layer (7) of a metal (Zn, In, Sn, etc.) that is lower than Al on the surface (see FIG. 2). It can be manufactured by brazing and joining the tube (2) and the fin (3) by heating at a predetermined temperature in a furnace.

  The method for forming the coating layer is not particularly limited, and examples thereof include cladding materials, thermal spraying, plating, vapor deposition, and sputtering.

  In the above manufacturing method, the tube (2) and the fin (3) may be brazed by any method. For example, using fins made of an aluminum brazing material clad with brazing material, the tube and fins may be brazed and joined by heating and melting of the brazing material, or after flux is applied to the joint and dried, Brazing and joining may be performed by heating in an inert gas atmosphere such as nitrogen.

  The heating temperature is preferably set in the range of 550 to 620 ° C. By setting to such a range, the heat exchanger of this invention can be manufactured efficiently and stably with high quality. If the heating temperature is smaller than the lower limit value, poor bonding is likely to occur, which is not preferable. In particular, the heating temperature is particularly preferably set to a range of 590 to 610 ° C.

  When brazing in the furnace, other heat exchanger components such as headers (4) (4), side plates (10) (10), etc. are temporarily assembled together, and the entire heat exchanger is brazed simultaneously. It is recommended to make it. Thus, these other components may be made of a brazing material, or a brazing material may be interposed only at the joint between the members.

  Next, specific examples of the present invention will be described.

<Examples 1-4, Comparative Examples 1-3>
Using an aluminum alloy (containing the additive metal shown in Table 1) and at a temperature of 450 ° C., tube width: 16 mm, tube thickness (height): 3 mm, wall thickness: 0.5 mm, number of hollow parts: 4 The flat tube was extruded. And on the flat surface of the front and back of the flat tube continuously extruded from the extruder, the Al-Zn alloy is sprayed from the spray nozzles (arc sprayers) arranged above and below at the position immediately after the extrusion. Obtained. The spraying current was set to 50 to 300 A, the spraying voltage was set to 20 to 30 V, and the extrusion speed was set to 5 to 100 m / min for spraying.

  Next, the flat tube (2) and corrugated fins (3) made of an aluminum brazing material clad with a brazing material are alternately laminated (see FIG. 2), and the core portion of the heat exchanger is assembled (temporarily assembled). ), The headers (4) and (4), the side plates (10) and (10), etc. were also temporarily assembled together. Next, a suspension obtained by suspending a fluoride-based flux in water is applied to the core part, dried, and then brazed by heating at 600 ° C. for 10 minutes in a nitrogen gas atmosphere furnace. A multi-flow type heat exchanger as shown in FIG. 1 was manufactured.

  Table 1 shows the configuration of the tube of the heat exchanger thus manufactured (added metal type of tube core material, added metal type of sacrificial corrosion layer and its surface concentration, sacrificial corrosion layer thickness, relative potential difference, etc.).

<Examples 5-8, 13-16, 21, 22, Comparative Examples 4, 5>
Using an aluminum alloy (containing Mn at a content shown in Table 2) and at a temperature of 450 ° C., tube width: 16 mm, tube thickness (height): 3 mm, wall thickness: 0.5 mm, number of hollow parts: Four flat tubes were extruded. And on the flat surface of the front and back of the flat tube continuously extruded from the extruder, the Al-Zn alloy is sprayed from the thermal spray nozzles (arc sprayers) arranged above and below at the position immediately after the extrusion. Obtained. The spraying current was set to 50 to 300 A, the spraying voltage was set to 20 to 30 V, and the extrusion speed was set to 5 to 100 m / min for spraying.

  Next, the flat tube (2) and corrugated fins (3) made of an aluminum brazing material clad with a brazing material are alternately laminated (see FIG. 2), and the core portion of the heat exchanger is assembled (temporarily assembled). ), The headers (4) and (4), the side plates (10) and (10), etc. were also temporarily assembled together. Next, a suspension obtained by suspending a fluoride-based flux in water is applied to the core part, dried, and then brazed by heating at 600 ° C. for 10 minutes in a nitrogen gas atmosphere furnace. A multi-flow type heat exchanger as shown in FIG. 1 was manufactured.

  Table 2 shows the configuration of the tube of the heat exchanger thus manufactured (added metal species and content of the tube core material, added metal species and surface concentration of the sacrificial corrosion layer, thickness of the sacrificial corrosion layer, and relative potential difference). Show.

<Examples 9, 10, 17, 18>
A multi-flow type heat exchanger as shown in FIG. 1 was produced in the same manner as in Examples 5 to 8 except that the Al—In alloy was sprayed instead of the Al—Zn alloy. Table 2 shows the configuration of the tube of the manufactured heat exchanger (added metal species and content of the tube core material, added metal species and surface concentration of the sacrificial corrosion layer, thickness of the sacrificial corrosion layer, and relative potential difference). .

<Examples 11, 12, 19, and 20>
A multi-flow type heat exchanger as shown in FIG. 1 was produced in the same manner as in Examples 5 to 8 except that the Al—Sn alloy was sprayed instead of the Al—Zn alloy. Table 2 shows the configuration of the tube of the manufactured heat exchanger (added metal species and content of the tube core material, added metal species and surface concentration of the sacrificial corrosion layer, thickness of the sacrificial corrosion layer, and relative potential difference). .

<Examples 23, 24, 29, and 30, Comparative Example 6>
An aluminum alloy thin plate containing the additive metal (Cr, Zr, or Cu) with the content shown in Table 3 was produced by rolling, and after blasting the surface of this thin plate, an aluminum alloy containing 1% by mass of Zn was sprayed. did. At this time, the spraying current was set to 50 to 300 A, the spraying voltage was set to 20 to 30 V, and the extrusion speed was set to 5 to 100 m / min for spraying. Next, this thin plate was formed into a tube shape by roll forming to obtain a flat tube (2).

  Next, the flat tube (2) and corrugated fins (3) made of an aluminum brazing material clad with a brazing material are alternately laminated (see FIG. 2), and the core portion of the heat exchanger is assembled (temporarily assembled). ), The headers (4) and (4), the side plates (10) and (10), etc. were also temporarily assembled together. Next, a suspension obtained by suspending a fluoride-based flux in water is applied to the core part, dried, and then brazed by heating at 600 ° C. for 10 minutes in a nitrogen gas atmosphere furnace. A multi-flow type heat exchanger as shown in FIG. 1 was manufactured.

  Table 3 shows the configuration of the tube of the heat exchanger thus manufactured (added metal species and content of the tube core material, added metal species and surface concentration of the sacrificial corrosion layer, thickness of the sacrificial corrosion layer, and relative potential difference). Show.

<Examples 25, 26, 31, 32, Comparative Example 7>
A multi-flow type heat exchanger as shown in FIG. 1 in the same manner as in Example 23 except that the aluminum alloy containing 0.1% by mass of In was sprayed instead of the aluminum alloy containing 1% by mass of Zn. Was made. Table 3 shows the configuration of the tube of the manufactured heat exchanger (added metal species and content of the tube core material, added metal species of the sacrificial corrosion layer, thickness of the sacrificial corrosion layer, and relative potential difference).

<Examples 27, 28, 33, and 34, Comparative Example 8>
A multi-flow type heat exchanger as shown in FIG. 1 except that the aluminum alloy containing 0.1% by mass of Sn was sprayed instead of the aluminum alloy containing 1% by mass of Zn. Was made. Table 3 shows the configuration of the tube of the manufactured heat exchanger (added metal species and content of the tube core material, added metal species of the sacrificial corrosion layer, thickness of the sacrificial corrosion layer, and relative potential difference).

<Examples 35-37, Comparative Examples 9-11>
Using an aluminum alloy (with a Mn content in the range of 0.5 to 2.5% by mass) at a temperature of 450 ° C., tube width: 16 mm, tube thickness (height): 3 mm, wall thickness: 0.5 mm, The number of hollow parts: Four flat tubes were extruded. And on the flat surface of the front and back of the flat tube continuously extruded from the extruder, the Al-Zn alloy is sprayed from the thermal spray nozzles (arc sprayers) arranged above and below at the position immediately after the extrusion. Obtained. The spraying current was set to 50 to 300 A, the spraying voltage was set to 20 to 30 V, and the extrusion speed was set to 5 to 100 m / min for spraying.

  Next, the flat tube (2) and corrugated fins (3) made of an aluminum brazing material clad with a brazing material are alternately laminated (see FIG. 2), and the core portion of the heat exchanger is assembled (temporarily assembled). ), The headers (4) and (4), the side plates (10) and (10), etc. were also temporarily assembled together. Next, a suspension obtained by suspending a fluoride-based flux in water is applied to the core part, dried, and then brazed by heating at 600 ° C. for 10 minutes in a nitrogen gas atmosphere furnace. A multi-flow type heat exchanger as shown in FIG. 1 was manufactured.

  Table 4 shows the structure of the tube of the heat exchanger thus manufactured (additional metal species and surface concentration of the sacrificial corrosion layer, thickness of the sacrificial corrosion layer, and relative potential difference).

<Examples 38 to 49>
A multiflow type heat exchanger as shown in FIG. 1 was produced in the same manner as in Examples 5 to 8, except that the composition of the tube was as shown in Table 5. Table 5 shows the configuration of the tube of the manufactured heat exchanger (added metal species and content of the tube core material, added metal species and surface concentration of the sacrificial corrosion layer, thickness of the sacrificial corrosion layer, and relative potential difference). . As the Al—Zn alloy used for thermal spraying, an Al—Zn alloy wire having a Zn content in the range of 1 to 4% by mass was used.

  The corrosion resistance of the tube was examined for each heat exchanger obtained as described above. These results are shown in Tables 1-5. The evaluation method is as follows.

<Corrosion test>
The SWAAT test according to ASTM D1141 was conducted for 960 hours, the pitting corrosion was not observed in the tube, and the corrosion stopped at the boundary between the tube core and the sacrificial corrosion layer. The case where the corrosion did not stop and the corrosion progressed to the inside of the tube was designated as “Δ”, and the case where the pitting corrosion penetrated to the inside of the tube was designated as “x”.

<Relative potential difference measurement>
The relative potential difference of the tube after brazing was measured as follows. That is, as described below, the surface (7a) of the sacrificial corrosion layer (7) and the middle position in the thickness direction of the tube core (6) (the position that bisects the distance between the upper surface and the lower surface of the tube core) ) (6a) was measured relative potential difference (see FIG. 3).

First, for the pitting corrosion potential measurement at the intermediate position (6a) in the thickness direction of the tube core material, the surface of the intermediate position (6a) is exposed by etching from the surface side of the tube, and then a square of 10 mm × 10 mm Was completely sealed with a sealing tape, and 1 L of 2.67 mol% AlCl ₃ aqueous solution (deoxygenated through nitrogen at 40 ° C., 100 mL / min for 60 minutes) The pitting potential was measured under the condition of a potential sweep rate of 20 mV / min. On the other hand, for the pitting corrosion potential measurement on the sacrificial corrosion layer surface (7a), after the fin (3) brazed and joined from the surface of the tube (2), as shown in FIG. (30) is masked with a resin that does not conduct electricity to form a mask part (31a), and all the surrounding parts are electrically charged, leaving a 10 mm × 10 mm square test surface. A mask part (31b) is formed by masking with a resin that does not pass, and this sample is immersed in 1 L of 2.67 mol% AlCl ₃ aqueous solution (deoxygenated through nitrogen at 40 ° C., 100 mL / min for 60 minutes). The pitting potential was measured at a potential sweep rate of 20 mV / min. In the measurement of the pitting potential, S.P. C. E. (Saturated calomel electrode) was used.

  The difference between the pitting corrosion potential at the intermediate position (6a) in the thickness direction of the tube core material measured as described above and the pitting corrosion potential on the sacrificial corrosion layer surface (7a) is calculated, and this is calculated as the relative potential difference. did.

  As is clear from Tables 1 to 5, the heat exchanger tubes and heat exchangers of Examples 1 to 49 of the present invention were excellent in corrosion resistance.

  On the other hand, in Comparative Examples 1-11 which deviate from the prescription | regulation range of this invention, it was inferior to corrosion resistance.

  According to the invention of [1], since a steep potential gradient can be applied in the tube thickness direction in the vicinity of the interface between the sacrificial corrosion layer and the tube core material, the progress of corrosion is caused at the boundary region between the sacrificial corrosion layer and the tube core material. Can be blocked. Furthermore, since the relative potential difference between the sacrificial corrosion layer surface and the intermediate position in the thickness direction of the tube core material is set in the range of 30 to 250 mV, the sacrificial corrosion layer is effectively preferentially corroded and has excellent corrosion resistance. Tube. Furthermore, since it can be produced industrially efficiently without being affected by slight fluctuations in brazing conditions, a product with stable quality can be manufactured at low cost.

  According to the invention of [2], since a steeper potential gradient can be applied in the tube thickness direction in the vicinity of the interface between the sacrificial corrosion layer and the tube core material, the progress of corrosion is controlled by the boundary region between the sacrificial corrosion layer and the tube core material. Can be sufficiently prevented. Furthermore, since the relative potential difference between the sacrificial corrosion layer surface and the intermediate position in the thickness direction of the tube core material is set in the range of 30 to 250 mV, the sacrificial corrosion layer is effectively preferentially corroded and has excellent corrosion resistance. Tube. Furthermore, since it can be produced industrially efficiently without being affected by slight fluctuations in brazing conditions, a product with stable quality can be manufactured at low cost.

  According to the invention of [3], since the diffusion of the potential noble metal in the tube core material into the sacrificial corrosion layer is further suppressed, the progress of corrosion is surely ensured at the boundary region between the sacrificial corrosion layer and the tube core material. Can be blocked.

  According to the invention of [4], the corrosion resistance can be further improved.

  According to the invention of [5], the corrosion resistance can be further improved.

  According to the invention of [6], there are advantages that the extrudability of the tube is improved and the manufacture of the multi-hole fine tube is facilitated.

  According to the invention of [7], the high temperature strength of the tube is improved.

  According to the invention of [8], the corrosion resistance can be further improved.

  According to the invention of [9], the corrosion resistance can be further improved.

  According to the invention of [10], the corrosion resistance can be further improved.

  According to the invention of [11], the corrosion resistance can be further improved.

  According to the invention of [12], the tube is more excellent in corrosion resistance.

  According to the invention of [13], the corrosion rate can be suppressed and the sacrificial corrosion layer thickness can be reduced.

  According to the invention of [14], the corrosion resistance can be further improved.

  According to the invention [15], since the relative potential difference between the sacrificial corrosion layer surface and the intermediate position in the thickness direction of the tube core material is set to 40 to 150 mV, there is an advantage that the corrosion resistance can be further improved.

  According to the invention of [16], the corrosion depth can be reduced as compared with the prior art.

  According to the invention of [17], the corrosion depth can be further reduced as compared with the prior art.

  According to the invention of [18], since the production efficiency is improved, a high-quality heat exchanger tube can be provided at a low cost.

  According to the invention [19], since the sacrificial corrosion layer is formed by thermal spraying, the production efficiency is high, and a high-quality heat exchanger tube can be provided at a lower cost.

  According to the invention [20], since the Zn content and the surface Zn concentration in the sacrificial corrosion layer can be strictly controlled, the quality of the tube can be further improved.

  According to the invention [21], the corrosion resistance of the tube can be further improved.

  According to the invention of [22], since a steep potential gradient can be applied in the tube thickness direction in the vicinity of the interface between the sacrificial corrosion layer and the tube core material, the progress of corrosion is controlled at the boundary region between the sacrificial corrosion layer and the tube core material. Can be blocked. Furthermore, since the relative potential difference between the sacrificial corrosion layer surface and the middle position in the thickness direction of the tube core material is set in the range of 30 to 250 mV, the sacrificial corrosion layer of the tube is effectively preferentially corroded, A high-quality heat exchanger with excellent durability can be provided. Furthermore, since it can be produced industrially efficiently without being affected by slight fluctuations in brazing conditions, a heat exchanger with stable quality can be provided at low cost.

  According to the invention of [23], it is possible to manufacture a high-quality heat exchanger excellent in the corrosion resistance of the tube and excellent in durability.

It is a front view which shows the heat exchanger which concerns on one Embodiment of this invention. It is a perspective view which shows the joining state of a tube and a fin. It is sectional drawing of the tube for heat exchangers. It is explanatory drawing which shows typically the electric potential state in a tube core material and a sacrificial corrosion layer, (a) shows a prior art example, (b) shows an example of this invention, respectively. It is explanatory drawing of the measuring method of a relative potential difference.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heat exchanger 2 ... Tube 3 ... Fin 4 ... Header 6 ... Tube core material 6a ... Middle position of thickness direction 7 ... Sacrificial corrosion layer 7a ... Surface

Claims (23)

In the heat exchanger tube in which the sacrificial corrosion layer (7) is provided on the surface of the aluminum tube core (6),
The aluminum tube core (6) has a higher potential than Al as a metal that is mainly added to impart a relative potential difference between the sacrificial corrosion layer (7) and the tube core (6). A metal having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C.
A high corrosion-resistant tube for a heat exchanger, wherein a relative potential difference between the surface of the sacrificial corrosion layer (7) and an intermediate position in the thickness direction of the tube core (6) is 30 to 250 mV. In the heat exchanger tube in which the sacrificial corrosion layer (7) is provided on the surface of the aluminum tube core (6),
The aluminum tube core (6) has a higher potential than Al as a metal that is mainly added to impart a relative potential difference between the sacrificial corrosion layer (7) and the tube core (6). A metal whose diffusion coefficient in aluminum of the metal element at 600 ° C. is 1 × 10 ⁻¹⁰ cm ² / sec or less,
A high corrosion-resistant tube for a heat exchanger, wherein a relative potential difference between the surface of the sacrificial corrosion layer (7) and an intermediate position in the thickness direction of the tube core (6) is 30 to 250 mV. A metal having a higher potential than Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C. is selected from the group consisting of Mn, Cr and Zr The high corrosion-resistant tube for heat exchangers according to claim 1, wherein the high-corrosion resistant tube is one or two or more metals. Mn is used as a metal having a higher potential than Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C., and the aluminum tube core material The high corrosion resistance tube for a heat exchanger according to claim 1, wherein the Mn content in the heat exchanger is 0.5 to 2.5 mass%.   The high corrosion-resistant tube for heat exchangers according to claim 4 whose Mn content in said aluminum tube core material (6) is 0.8-2 mass%.   The highly corrosion-resistant tube for heat exchangers according to claim 4, wherein the Mn content in the aluminum tube core (6) is 0.5 mass% or more and less than 1 mass%.   The high corrosion-resistant tube for heat exchangers according to claim 4, wherein the Mn content in the aluminum tube core (6) is more than 1.5% by mass and 2% by mass or less.   The aluminum tube core material (6) contains Cu, and the Cu content in the aluminum tube core material (6) is more than 0 and 0.6 mass% or less. The high corrosion-resistant tube for heat exchangers as described in the item.   The aluminum tube core material (6) contains Cu, and the Cu content in the aluminum tube core material (6) is more than 0 and 0.4 mass% or less. The high corrosion-resistant tube for heat exchangers as described in the item. Cr is used as a metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C., and the aluminum tube core material The high corrosion resistance tube for a heat exchanger according to claim 1, wherein the Cr content in (6) is 0.3 to 2 mass%. Zr is used as a metal having a potential higher than that of Al and having a diffusion coefficient of 1 × 10 ⁻⁹ cm ² / sec or less in aluminum of the metal element at 600 ° C., and the aluminum tube core material The high corrosion resistance tube for a heat exchanger according to claim 1, wherein the Zr content in (6) is 0.3 to 5 mass%.   The heat exchanger height according to any one of claims 1 to 11, wherein the additive metal of the sacrificial corrosion layer (7) is one or more metals selected from the group consisting of Zn, In and Sn. Corrosion resistant tube.   The high corrosion resistance for a heat exchanger according to any one of claims 1 to 11, wherein the additive metal of the sacrificial corrosion layer (7) is Zn, and the surface Zn concentration in the sacrificial corrosion layer is 1.5 mass% or less. tube.   The high corrosion-resistant tube for heat exchangers according to claim 13, wherein the surface Zn concentration in the sacrificial corrosion layer (7) is 1.2 mass% or less.   The height for a heat exchanger according to any one of claims 1 to 14, wherein a relative potential difference between the surface of the sacrificial corrosion layer (7) and an intermediate position in the thickness direction of the tube core material (6) is 40 to 150 mV. Corrosion resistant tube.   The thickness of the said sacrificial corrosion layer (7) is 20-150 micrometers, The high corrosion-resistant tube for heat exchangers of any one of Claims 1-15.   The thickness of the said sacrificial corrosion layer (7) is 20-50 micrometers, The high corrosion-resistant tube for heat exchangers of any one of Claims 1-15.   The high corrosion-resistant tube for a heat exchanger according to any one of claims 1 to 17, wherein the tube core (6) is formed by extrusion.   The highly corrosion-resistant tube for a heat exchanger according to any one of claims 1 to 18, wherein the sacrificial corrosion layer (7) is formed by thermal spraying.   The high corrosion resistance tube for a heat exchanger according to claim 13 or 14, wherein the sacrificial corrosion layer (7) is formed by spraying an Al-Zn alloy.   The sacrificial corrosion layer (7) is formed by spraying an Al-Zn alloy wire, and the Zn content in the Al-Zn alloy is 1 to 4 mass%. High corrosion resistance tube for heat exchanger. A plurality of tubes (2) each having a sacrificial corrosion layer (7) provided on the surface of an aluminum tube core (6) are laminated with fins (3) interposed therebetween, and the tubes ( In the heat exchanger (1) in which 2) and the fin (3) are joined and integrated by brazing, and a hollow header (4) is connected to both ends of the tube (2).
The heat exchanger according to any one of claims 1 to 21, wherein the tube (2) is a high corrosion resistance tube for a heat exchanger. As a metal mainly added to give a relative potential difference between the sacrificial corrosion layer (7) and the tube core material (6), the metal element at 600 ° C. is a metal having a potential higher than that of Al. A sacrificial corrosion layer (7) of a metal lower than Al is formed on the surface of an aluminum tube core (6) containing a metal whose diffusion coefficient in aluminum is 1 × 10 ⁻⁹ cm ² / sec or less. At least a step of producing an aluminum heat exchanger tube (2);
Assembling the fin (3) to the heat exchanger tube (2);
A method of manufacturing a heat exchanger, comprising a step of brazing and joining the tube (2) and the fin (3) by heating at a predetermined temperature in the assembled state.

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