JP2016003356A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger having excellent corrosion resistance.SOLUTION: The heat exchanger is obtained by brazing a tube to an outer fin. The tube comprises a brazing sheet consisting of a core material, a brazing filler metal and a sacrificial material. The core material consists of an aluminum alloy containing Mn of 1.2-1.8%, Si of 0.4-1.3%, Fe of 0.21-0.5% and Cu of 0.5-1.3%. The brazing filler metal consists of another aluminum alloy containing Si of 6.0-11.0% and Zn of 0.1-5.0%. The sacrificial material consists of a different aluminum alloy containing Zn of 4.0-7.0%, Mg of 1.2-2.5% and Si of 0.1-0.4%. Among the brazing filler metal formed on the surface of the tube, the order of: at the least, potential of the brazing filler metal in the joined part thereof to the outer fin and in the vicinity of the joined part; potential of the core material of the tube; and potential of the outer fin is made, the potential of the outer fin being the lowest and the potential of the brazing filler metal being lower than the potential of the core material.

Description

  The present invention relates to a heat exchanger.

  2. Description of the Related Art Conventionally, aluminum automotive heat exchangers are known. This heat exchanger is comprised from members, such as an outer fin, a tube, a header plate, a side support, for example. Moreover, the heat exchanger for motor vehicles is generally commercialized by joining each of the above-mentioned members by a brazing process using a fluoride-based flux at a temperature of about 600 ° C.

  Moreover, the tube and header plate which comprise a heat exchanger may be comprised from a brazing sheet. As this brazing sheet, for example, an Al-Si alloy brazing material is bonded to one side of a core material made of an aluminum alloy containing Mn, Cu, Si, Fe in a specified range, and the other side. In addition, a structure in which a sacrificial material (lining material) of an aluminum alloy that is electrochemically lower than the core material is bonded (see, for example, Patent Document 1 and Patent Document 2). The sacrificial material used here can function as a sacrificial anode material and prevent corrosion of the core material by using a material that is electrochemically lower than the core material.

Japanese Patent Laid-Open No. 9-295089 JP 2012-117107 A

Incidentally, the brazing sheet used for the tube material of the heat exchanger is required to be further thinned in order to reduce the size and increase the performance of the heat exchanger. However, the above-described prior art is insufficient to improve the strength commensurate with the thinning, and conversely, when the alloying elements are increased, the deterioration of castability tends to be a problem against the improvement of the material strength.
In addition, when the thickness is reduced, diffusion of Zn added to the sacrificial material into the core material and diffusion of Cu added to the core material into the sacrificial material progress, and the sacrificial material and the core material are between. The potential gradient is reduced and the corrosion resistance of the inner peripheral surface of the tube is reduced.

  Further, since diffusion of Cu added to the core material to the brazing material side proceeds in the same manner, there is a problem that the corrosion resistance on the tube outer surface side is lowered. In particular, the corrosion resistance on the outer surface side of the tube is a problem that the potential becomes noble due to the concentration of Cu in the joint fillet with the outer fin, the sacrificial anode effect due to the outer fin cannot be sufficiently obtained, and the through hole is generated early in the tube was there.

  This invention is made | formed in view of the above situations, and it aims at providing the heat exchanger which is high intensity | strength as a thin structure, and is excellent in corrosion resistance.

  In order to solve the above problems, the present invention is a heat exchanger brazed by combining a tube and an outer fin, wherein the tube is formed of a core material and a brazing material formed on one surface of the core material. It is comprised with the brazing sheet | seat which consists of a sacrificial material formed in the other surface of the said core material, The said core material is Mn: 1.2-1.8% by mass%, Si: 0.4-1.3. %, Fe: 0.21 to 0.5%, Cu: 0.5 to 1.3%, the balance is made of an aluminum alloy having a composition of Al and inevitable impurities. : 6.0 to 11.0%, Zn: 0.1 to 5.0%, the balance is made of an aluminum alloy having the composition of Al and inevitable impurities, and the sacrificial material is Zn: 4. 0 to 7.0%, Mg: 1.2 to 2.5%, Si: 0.1 to 0 Of the brazing material formed on the surface of the tube, the brazing material in the vicinity of the outer fin and the brazing material in the vicinity of the joining portion are made of an aluminum alloy having a composition of 4% and the balance being Al and inevitable impurities. The permutation of the potentials of the tube core material and the outer fin is made lower in the order of the tube core material, the tube brazing material, and the outer fin.

In the present invention, the outer fin is preferably made of an aluminum alloy containing Zn: 0.5 to 3.5% by mass.
In the present invention, the electric potential of the outer fin is in the range of −830 mV to −750 mV, and the electric potential of the outer fin is at least a joint portion with the outer fin and the joint portion of the brazing material on the tube surface. It is characterized by being 30 mV or more lower than the potential of a nearby brazing material.
In the present invention, a potential difference between the core material of the tube and the outer fin is in a range of 120 to 220 mV.
In the present invention, the sacrificial material preferably further contains Ti: 0.3% or less by mass.

The heat exchanger of the present invention uses a core material, a brazing material, and a sacrificial material having the above-described composition, so that the tube is thinned and has a sufficient strength for a heat exchanger even if its plate thickness is less than 0.2 mm, for example. Can be obtained.
Further, by adding a specified amount of Zn to the brazing material, a potential gradient on the outer peripheral surface side of the single tube can be secured, and the corrosion resistance can be improved.
In addition, by optimizing the potential balance of the outer fin, the brazing material of the tube, and the core material, the sacrificial anode effect due to the outer fin is enhanced, and even when the tube is made thinner than the conventional heat, it has excellent corrosion resistance. An exchange can be provided.

Sectional drawing of the brazing sheet employ | adopted as the heat exchanger which is one Embodiment of this invention. Sectional drawing which shows an example of the tube formed using the brazing sheet shown in FIG. The perspective view which made a part of heat exchanger which is one embodiment of the present invention a section.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the drawings used in the following description, for the purpose of emphasizing the feature portion, the feature portion may be shown in an enlarged manner for convenience, and the dimensional ratios of the respective constituent elements are not always the same as in practice. Absent. In addition, for the same purpose, portions that are not characteristic may be omitted from illustration.

<Brazing sheet>
FIG. 1 is a cross-sectional view of a brazing sheet 1 used in the heat exchanger 20 (see FIG. 3) of the present embodiment. This brazing sheet 1 is composed of a core material 1a made of an aluminum alloy, a layered brazing material 1b made of an aluminum alloy deposited on one surface side of the core material 1a, and on the other surface side of the core material 1a. The main component is a layered sacrificial material 1c made of a deposited (clad pressure bonded) aluminum alloy.

The deposition (clad pressure bonding) is generally performed by hot rolling. Then, the aluminum alloy brazing sheet 1 having a desired thickness is obtained by further cold rolling. The configuration of the clad material can be, for example, sacrificial material 1c: core material 1a: brazing material 1b = 15%: 75%: 10%. However, the configuration of the cladding material is not limited to this, and the cladding rate of the sacrificial material 1c may be set to 17% or 20%, for example.
Further, the brazing sheet 1 employed in the heat exchanger 20 of the present embodiment may have a thin structure with a thickness of less than 0.2 mm, for example, about 0.18 mm. Thereby, the lightweight and cheap heat exchanger 20 can be comprised.

<Tube>
As shown in FIG. 2, the brazing sheet 1 is formed into a flat tube so that the sacrificial material 1c is on the inside and the brazing material 1b is on the outside with a forming roll or the like. The tube 10 as an electric-welded welded pipe can be configured.

<Heat exchanger>
Using the tube 10 having the structure shown in FIG. 2, for example, a heat exchanger 20 having the shape shown in FIG. 3 can be configured.
The heat exchanger 20 has a structure used for, for example, a radiator of an automobile, and includes a tube 10, a header 21, an outer fin 22, and a side support 23.
The header 21 and the tube 10 are connected to each other by using the brazing material 1b arranged around the insertion portion by inserting the end portion of each tube 10 into a plurality of slots (insertion holes) 21a formed in the header 21. It is joined by brazing. Moreover, the tube 10 and the outer fin 22 are joined by brazing together using the brazing material 1b provided in the brazing sheet 1 which comprises the tube 10. FIG.
Note that brazing of the end portions 1A and 1A of the brazing sheet 1 when forming the tube 10 (see FIG. 2), brazing of the header 21 and the tube 10, and brazing of the tube 10 and the outer fin 22 are heat exchange. This can be done simultaneously with the assembly of the vessel 20.

Next, the composition of the outer fin 22 and the core material 1a, the brazing material 1b, and the sacrificial material 1c of the tube 10 in this embodiment will be described.
<Outer fin>
It is preferable to form the outer fin 22 joined to the tube 10 from an aluminum alloy to which 0.5 to 3.5% Zn is added in mass%. In the present specification, when the upper limit and the lower limit of the composition ratio are expressed as 0.5 to 3.5%, the upper limit and the lower limit are included unless otherwise specified. Therefore, 0.5 to 3.5% means a range of 0.5% or more and 3.5% or less.
The outer fin 22 is processed into a corrugated shape by melting an aluminum alloy having the above composition by a conventional method and passing through a hot rolling process, a cold rolling process, and the like. In addition, the manufacturing method of the outer fin 22 is not specifically limited, A known manufacturing method can be employ | adopted suitably.

The potential of the outer fin 22 (pitting corrosion potential mV vs SCE) is desirably −830 mV or more and −750 mV or less. If the potential of the outer fin 22 exceeds −750 mV, the potential of the outer fin 22 cannot be sufficiently reduced with respect to the potential indicated by the brazing material 1b of the tube 10 after brazing, and the sacrificial anode by the outer fin 22 The effect may be insufficient. If the potential of the outer fin 22 is less than −830 mV, the corrosion rate of the outer fin 22 increases, and the outer fin corrodes early, so that a sufficient sacrificial anticorrosive effect cannot be obtained.
The potential of the outer fin 22 can be adjusted by the Zn content of the aluminum alloy constituting the outer fin 22. Hereinafter, the range of the content of Zn contained in the outer fin 22 will be described in detail.

[component]
The outer fin 22 contains Mn and Zn, and contains at least one selected from Cu, Si, and Fe, and the balance is made of an aluminum alloy composed of Al and inevitable impurities. The content of each component is Mn: 0.8 to 1.5 mass%, Zn: 0.5 mass% to 3.5 mass%, Cu: 0.05 to 0.3 mass%, Si: 0.05 to 1.0 mass%, Fe: 0.05-0.5 mass%. Hereinafter, each component will be described.
[Zn: 0.5% by mass to 3.5% by mass]
Zn has the effect of lowering the potential of the aluminum alloy, and when added to the outer fin 22 within the above range, it is possible to ensure a desirable potential difference with respect to the brazing material 1b, and to create a potential gradient effective for corrosion resistance. Thus, there is an effect of improving the corrosion resistance and reducing the corrosion depth. However, if the Zn content is less than 0.5% by mass, the effect is not sufficiently exhibited. If the Zn content exceeds 3.5% by mass, the potential becomes extremely low and the corrosion rate increases, so that the outer fins corrode early. To do.

[Si, Fe, Cu, Mn]
Si, Fe and Mn crystallize intermetallic compounds such as Al-Mn-Si, Al-Mn-Fe, Al-Fe-Si, or Al-Mn-Fe-Si in aluminum alloys To improve the strength of the aluminum alloy. If the content is too large, the corrosion rate may become too fast, causing problems such as the precipitation of giant crystals, so the above-mentioned range is desirable. However, the content of these elements is not particularly limited as long as the potential gradient can be controlled within the desired range in the present embodiment by controlling the Zn content described above.

<Tube core material>
The core material 1a of the tube 10 is, in mass%, Mn: 1.2 to 1.8%, Si: 0.4 to 1.3%, Fe: 0.21 to 0.5%, Cu: 0.5 to The aluminum alloy contains 1.3% and the balance is aluminum and the composition of inevitable impurities.
Hereinafter, the range of each constituent element content of the aluminum alloy constituting the core material 1a of the tube 10 will be described in detail.

[component]
[Mn: 1.2% to 1.8% by mass]
Mn has the effect of increasing the material strength by forming Al—Mn—Si, Al—Mn—Fe, and Al—Mn—Fe—Si intermetallic compounds in the matrix. However, when the amount of Mn is less than 1.2% by mass, the effect is not sufficiently exhibited. When the amount exceeds 1.8% by mass, a huge intermetallic compound is generated at the time of casting, so that the formability of the material is lowered. For the same reason, the Mn content is desirably 1.4 to 1.8% by mass, and more desirably 1.5 to 1.75% by mass.

[Si: 0.4 to 1.3% by mass]
Si has the effect of increasing the material strength by forming Al—Mn—Si and Al—Mn—Fe—Si intermetallic compounds in the matrix. However, if the amount of Si is less than 0.4% by mass, the effect is not sufficiently exhibited, and if it exceeds 1.3% by mass, the melting point of the material is lowered. For the same reason, the Si content is preferably 0.6 to 1.2% by mass, and more preferably 0.7 to 1.1% by mass.

[Fe: 0.21 to 0.5% by mass]
Fe is an Al-Mn-Fe-based, Al-Mn-Fe-Si-based intermetallic compound formed in the matrix, and the effect of increasing the material strength and by refining the crystal grains after brazing heat treatment, There is an effect of improving the strength after brazing. However, if the amount of Fe is less than 0.21% by mass, the effect is not sufficiently exerted, and if it exceeds 0.5% by mass, the corrosion resistance is deteriorated, or a huge intermetallic compound is produced during casting to form the material. Decreases. For the same reason, the Fe content is preferably 0.25 to 0.45% by mass, and more preferably 0.28 to 0.40% by mass.

[Cu: 0.5% by mass to 1.3% by mass]
Cu dissolves in the matrix and increases the strength of the material, and when added to the core material 1a, the potential difference between the core material 1a and the sacrificial material 1c is increased and the effect of improving the corrosion resistance is obtained. is there.
However, if the amount of Cu is less than 0.5% by mass, the effect is not sufficiently exhibited, and if it exceeds 1.3% by mass, the melting point of the material is lowered. For the same reason, the Cu content is preferably 0.6 to 1.2% by mass, and more preferably 0.7 to 1.1% by mass.

<Tube brazing material>
The brazing material 1b of the tube 10 contains 6.0% by mass to 11.0% by mass of Si, 0.1% by mass to 5.0% by mass of Zn, and the balance is made of aluminum and an aluminum alloy of inevitable impurities. .
Hereinafter, the range of the content of each constituent element of the aluminum alloy constituting the brazing material 1b of the tube 10 will be described in detail.

[component]
[Si: 6.0% by mass to 11.0% by mass]
Si contained in the brazing filler metal 1b is a component that lowers the melting point and imparts fluidity. If the content is less than 6% by mass, the desired effect is insufficient. On the other hand, if the content exceeds 11% by mass, On the contrary, it is not preferable because the fluidity is lowered. Therefore, the content of Si in the brazing material 1b is preferably in the range of 6.0 to 11.0% by mass.

[Zn: 0.1% by mass to 5.0% by mass]
Zn has the effect of lowering the potential of the aluminum alloy, and when added to the brazing material 1b, the potential difference from the core material 1a is increased, and a potential gradient effective for corrosion resistance is created, thereby improving the corrosion resistance and increasing the corrosion depth. There is an effect of reducing the thickness. However, when the Zn content is less than 0.1% by mass, the effect is not sufficiently exhibited. When the Zn content exceeds 5.0% by mass, the potential of the brazing material 1b is too low, and a potential difference from the outer fin 22 is ensured. I can't do that.

<Sacrificial material for tubes>
The sacrificial material 1c of the tube 10 contains 4.0% by mass to 7.0% by mass of Zn, 1.2% by mass to 2.5% by mass of Mg, and 0.1% by mass to 0.4% by mass of Si. The balance is preferably made of an aluminum alloy having a composition of aluminum and inevitable impurities.
Hereinafter, the reasons for limiting the constituent elements of the aluminum alloy constituting the sacrificial material 1c of the tube 10 will be described.

[component]
[Zn: 4.0 to 7.0% by mass]
Zn has the effect of lowering the potential of the aluminum alloy, and when added to the sacrificial material 1c, the potential difference from the core material 1a increases, and a potential gradient effective for corrosion resistance can be formed, so that the brazing sheet 1 (that is, the tube 10). Has the effect of improving the corrosion resistance and reducing the corrosion depth. Zn also has the effect of increasing the strength after brazing by forming a fine Mg—Zn compound with Mg in a very short time after brazing.
However, when the Zn content is less than 4.0% by mass, the effect is not sufficiently exerted. When the Zn content exceeds 7.0% by mass, the corrosion rate becomes too fast, so that the sacrificial material 1c disappears early, and the corrosion depth is low. To increase. For the same reason, the Zn content is preferably 4.5 to 7.0% by mass, and more preferably 4.8 to 6.8% by mass.

[Mg: 1.2-2.5% by mass]
Mg diffuses into the core material after brazing and has the effect of improving the strength of the material by forming a fine Mg-Si compound with Si in the region where Mg and Si coexist. However, when the amount of Mg is less than 1.2% by mass, the effect is not sufficiently exhibited, and when it exceeds 2.5% by mass, the moldability of the material is lowered. For the same reason, the Mg content is preferably 1.2 to 2.2% by mass, and more preferably 1.3 to 2.0% by mass.

[Si: 0.1 to 0.4% by mass]
Si has the effect of improving the strength of the material by forming a fine Mg-Si compound with Mg. However, if the amount of Si is less than 0.1% by mass, the effect is not sufficiently exhibited, and if it exceeds 0.4% by mass, the melting point of the material is lowered. For the same reason, the Si content is preferably 0.13 to 0.35% by mass, and more preferably 0.15 to 0.32% by mass.
[Ti: 0.3% by mass or less]
When Ti is added, a portion having a high Ti concentration and a portion having a low Ti concentration are formed during casting, and these form a layered Ti concentration distribution in the material, thereby improving the corrosion resistance. However, when the Ti content exceeds 0.3% by mass, the castability and workability of the material deteriorate. For these reasons, the Ti content is preferably in the range of 0.01 to 0.25% by mass.

<Permutation of potential>
Conventionally, it is known that the potential of the sacrificial material 1c is made lower than the potential of the core material 1a in order to increase the corrosion resistance on the inner peripheral surface of the tube 10. However, on the outer peripheral surface of the tube 10, in the process of brazing the tube 10 and the outer fin 22, Cu added to the core material 1 a diffuses into the brazing material 1 b and joins 30 (fillet) with the outer fin 22. When Cu concentrates, the potential becomes noble and there is a problem that a through hole is generated in the tube 10.

In the heat exchanger 20 of the present embodiment, after brazing, the permutation of the potentials of the brazing material 1b, the core material 1a, and the outer fin at the joint portion 30 between the tube 10 and the outer fin 22 is as described above. The core material 1a, the brazing material 1b at the joint, and the outer fin are in this order.
Thereby, the sacrificial anode effect with respect to the tube 10 can be given to the outer fin 22, the corrosion resistance of the tube 10 can be improved, and the occurrence of through holes can be prevented.

More specifically, it is desirable that the potential difference between the outer fin 22 and the brazing material 1b of the joint portion 30 is 30 mV or more. The potential difference between the outer fin 22 and the core material 1a is preferably 120 mV or more and 220 mV or less. Thereby, the heat exchanger 20 with high corrosion resistance can be produced.
In the heat exchanger 20 having the above-described configuration, while the core material 1a is made of a high strength material corresponding to thinning with the contents of Mn, Si, Fe, and Cu as specific ranges, Mg and Si are also specified for the sacrificial material 1c. As a range, the sacrificial material 1c is made to be a high-strength material corresponding to the thinning, and the balance of potential difference among the outer fin 22, the joint portion 30, and the core material 1a is made as described above, so that the thinning of the tube 10 is supported. And even if it makes the tube 10 thin, while having the intensity | strength required as the heat exchanger 20, the heat exchanger 20 excellent in corrosion resistance can be provided.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to these Examples.
<Preparation of sample>
Aluminum alloy for core material, aluminum alloy for sacrificial material, and aluminum alloy for brazing material were cast by semi-continuous casting. The composition of the aluminum alloy for the core material, the aluminum alloy for the sacrificial material, and the aluminum alloy for the brazing material is collectively shown in the subsequent stage.
The obtained core material was homogenized at 585 ° C. for 8 hours. The conditions for this homogenization treatment are an example, and can be selected from the range of temperature: 550 to 600 ° C. and holding time: 8 to 16 h. The sacrificial material and the brazing material can be subjected to the same homogenization treatment.

  Next, a sacrificial material was combined on one surface of the core material, and a brazing material was combined on the other surface, which was hot-rolled to form a clad material, and further cold-rolled. Thereafter, intermediate annealing was performed at 330 ° C. for 6 hours, and a cold-rolled H14 tempered clad material (sample) having a thickness of 0.18 mm was produced by final cold rolling at a predetermined rolling rate. The composition of the clad material was sacrificial material: core material: brazing material (thickness) = 15%: 75%: 10%. However, the intermediate annealing can be selected from the range of temperature: 200 to 380 ° C. and holding time: 1 to 6 h.

  The brazing sheet of sample No.1-No.21 was produced through the above process. Table 1 below shows the compositions of the core material, brazing material, and sacrificial material of the brazing sheets of samples No. 1 to No. 21. In Table 1, the balance of the elements shown is Al and inevitable impurities.

Hereinafter, characteristics of each sample of the brazing sheet shown in Table 1 will be described.
Sample No. 1 and 2 are samples in which the Si content of the core material is adjusted to set the upper limit and the lower limit of the preferable range, respectively. Sample No. 3 and 4 are samples in which the content of Si in the brazing material is adjusted to be an upper limit and a lower limit of a preferable range, respectively. Sample No. 5 and 6 are samples in which the content of Zn in the brazing material is adjusted to set the upper limit and the lower limit of the preferable range, respectively.
Sample No. 7 and 8 are samples in which the content of Si in the sacrificial material is adjusted to be an upper limit and a lower limit of a preferable range, respectively. Sample No. 9 and 10 are samples in which the content of Zn in the sacrificial material is adjusted to be the upper limit and the lower limit of the preferable range, respectively.
Sample No. 11 is a sample in which the constituent elements other than Al and unavoidable impurities constituting the core material, the brazing material, and the sacrificial material are in the preferable range.

Samples Nos. 12, 13 are prepared by adjusting the Si content of the core material so as to exceed the upper limit and lower than the lower limit of the preferable range, respectively. Samples Nos. 14, 15 are samples in which the content of Si in the brazing material is adjusted to be more than the upper limit and less than the lower limit of the preferable range, respectively. Samples Nos. 16, 17 are samples in which the content of Zn in the brazing material is adjusted to be more than the upper limit and less than the lower limit of the preferable range, respectively. Samples Nos. 18, 19 are samples in which the content of Si in the sacrificial material is adjusted to be above the upper limit and below the lower limit of the preferable range, respectively.
Samples Nos. 20 and 21 are samples in which the content of Mg in the sacrificial material is adjusted to be above the upper limit and below the lower limit of the preferred range, respectively.

  Next, each brazing sheet was processed into an electric resistance welded tube having the structure shown in FIG. A-No. E outer fin, combined with a 1.2 mm thick header plate (sacrificial material: JIS7072 / core material: JIS3003 + 0.5% Cu / brazing material: 4343, clad rate sacrificial material: 10%, brazing material: 10%) A heat exchanger was produced. Brazing is performed by applying a fluoride flux from the outside to the heat exchanger, and then maintaining in a high-purity nitrogen gas atmosphere and heat treatment equivalent to brazing at 600 ° C. for 3 minutes (the temperature rising time from room temperature to 600 ° C. is 5 to 7). Min).

The characteristics of each sample of the outer fin shown in Table 2 will be described.
Sample No. A is a sample in which the content of Zn in the outer fin is adjusted to exceed the upper limit of the preferred range. Sample No. B is a sample in which the content of Zn in the outer fin is adjusted to the upper limit of the preferred range. Sample No. C is a sample in which the content of Zn in the outer fin is adjusted to the middle of the preferred range. Sample No. D is a sample in which the content of Zn in the outer fin is adjusted to the lower limit of the preferred range. Sample No. E is a sample in which the content of Zn in the outer fin is adjusted to be less than the lower limit of the preferred range.

<Evaluation>
The potential difference, the corrosion resistance, and the strength after brazing were measured for the heat exchanger of the brazed product produced by the above procedure. The methods for measuring potential difference, corrosion resistance, and strength after brazing are shown below. The measurement results are shown in Table 3.

"Pitting corrosion potential"
Anodic polarization measurement was performed, and the pitting corrosion potential of each of the outer fin and brazing material joints and the outer fin and core material was measured. A saturated calomel electrode was used for anodic polarization, and measurement was performed at a potential sweep rate of 0.5 mV / s in a 2.67% AlCl ₃ solution at 40 ° C. deaerated by blowing nitrogen gas.

"Corrosion resistance" (external corrosion resistance measurement test)
For heat exchangers (minicores) that combine outer fins and tubes by brazing heat treatment, the SWAAT test specified by ASTM G85-A3 is conducted for 500 hours, and the maximum corrosion depth of the tube material is measured after 500 hours. did.

"Heat exchanger durability"
The manufactured heat exchanger was repeatedly subjected to a pressure test of 0.5 to 150 kPa, and the number of times until the member broke was measured. In this example, the durability of the heat exchanger is described as an evaluation item regarding strength.

In Table 3, [pitting corrosion potential permutation] is indicated by tube core material> tube brazing material> outer fin material: ○, other than: ×.
In Table 3, the [corrosion resistance] is indicated by a corrosion depth of 40 μm or less: ◎, 41 to 70 μm: ◯, 71 μm or more: x.
In Table 3, the [durability] is indicated by the number of repetitions until the member breaks of 150,000 times or more: A, less than 10 to 150,000 times: ○, less than 100,000 times: x.

Heat exchanger sample No. 1 and 2 are samples in which the Si content of the core material is adjusted and set to the upper and lower limits of the preferred range, respectively, and the other contained elements are within the preferred range.
Heat exchanger sample No. 3 and 4 are samples in which the content of Si in the brazing material is adjusted and set to the upper and lower limits of the preferred range, respectively, and the other contained elements are within the preferred range.
Heat exchanger sample No. Nos. 5 and 6 are samples in which the Zn content of the brazing material is adjusted to set the upper limit and the lower limit of the preferred range, respectively, and the other contained elements are within the preferred range.
Heat exchanger sample No. 7 and 8 are samples in which the content of Si in the sacrificial material is adjusted and set to the upper and lower limits of the preferred range, respectively, and the other contained elements are within the preferred range.
Heat exchanger sample No. Nos. 9 and 10 are samples in which the Zn content of the sacrificial material is adjusted and set to the upper and lower limits of the preferred range, respectively, and the other contained elements are each within the preferred range. The example samples of heat exchanger samples No. 1 to 10 were excellent in corrosion resistance, high in strength after brazing, and excellent in durability.
Heat exchanger sample No. 11, 12, and 13, each element constituting the core material, the brazing material, and the sacrificial material is set within a preferable range, the tube sample No. 11 is used, and the outer fin sample Nos. B and C shown in Table 2 are used. , D was used properly, but it was excellent in corrosion resistance, high in strength after brazing, and excellent in durability.

Heat exchanger sample No. 14 is a sample using tube sample No. 12, but since the amount of Si in the core material is large, the tube core material melted during brazing.
Heat exchanger sample No. 15 was a sample using tube sample No. 13, but the result was inferior in durability because the amount of Si in the core material was small.
Heat exchanger sample No. 16 is a sample using tube sample No. 14, but because the amount of Si in the brazing material was too large, the brazing of the fin occurred and buckling occurred. Buckling means a state in which the shape of the heat exchanger cannot be maintained because the outer fin is eroded and lost due to flowing brazing during brazing.
Heat exchanger sample No. 17 was a sample using tube sample No. 15, but the bonding amount between the fin and the tube was poor because the amount of Si in the brazing material was small.
Heat exchanger sample No. 18 was a sample using tube sample No. 16, but because of the large amount of Zn in the brazing material, bonding failure between the fin and the tube occurred.
Heat exchanger sample No. 19 was a sample using tube sample No. 17, but because the amount of Zn in the brazing material was small, the perforation potential permutation collapsed, resulting in insufficient corrosion resistance.
Heat exchanger sample No. 20 was a sample using tube sample No. 18, but the sacrificial material melted during brazing because the amount of Si in the sacrificial material was large.
Heat exchanger sample No. 21 was a sample using tube sample No. 19, but the durability was lowered because the amount of Si in the sacrificial material was small.
Heat exchanger sample No. 22 was a sample using tube sample No. 20, but the sacrificial material melted during brazing because the amount of Mg in the sacrificial material was large.
Heat exchanger sample No. 23 is a sample using tube sample No. 21, but because the amount of Mg in the sacrificial material is small, the pitting potential permutation collapses and the corrosion resistance is reduced.
Although heat exchanger sample No. 24 is a sample using outer fin sample No. A, since there was much Zn quantity of an outer fin, a pitting potential permutation collapsed and corrosion resistance fell.
Although heat exchanger sample No. 25 is a sample using outer fin sample No. E, since the amount of Zn in the outer fin was small, the pitting potential permutation collapsed and the corrosion resistance decreased.

DESCRIPTION OF SYMBOLS 1 ... Brazing sheet, 1A ... End part, 1a ... Core material, 1b ... Brazing material, 1c ... Sacrificial material, 10 ... Tube, 20 ... Heat exchanger, 21 ... Header, 22 ... Outer fin, 23 ... Side support, 30 ... Junction.

Claims (5)

A heat exchanger brazed by combining a tube and an outer fin,
The tube is composed of a brazing sheet comprising a core material, a brazing material formed on one surface of the core material, and a sacrificial material formed on the other surface of the core material,
The core material is Mn: 1.2 to 1.8%, Si: 0.4 to 1.3%, Fe: 0.21 to 0.5%, Cu: 0.5 to 1.3% by mass%. Made of an aluminum alloy having a composition of the balance Al and inevitable impurities,
The brazing material contains Si: 6.0 to 11.0% by mass, Zn: 0.1 to 5.0%, and consists of an aluminum alloy having a composition of the balance Al and inevitable impurities,
The sacrificial material contains Zn: 4.0-7.0%, Mg: 1.2-2.5%, Si: 0.1-0.4% by mass%, the balance being Al and inevitable impurities An aluminum alloy having a composition of
Among the brazing materials formed on the surface of the tube, at least the joint portion with the outer fin and the brazing material in the vicinity of the joint portion, and the permutation of the potential of the core material and the outer fin of the tube are the core material of the tube, 2. A heat exchanger characterized in that the brazing material of the tube and the outer fin are made in this order.   The heat exchanger according to claim 1, wherein the outer fin is made of an aluminum alloy containing Zn: 0.5 to 3.5% by mass.   The outer fin has a potential in the range of −830 mV to −750 mV, and the outer fin has a potential of at least a joint with the outer fin and a brazing filler in the vicinity of the joint among the brazing filler metals on the tube surface. The heat exchanger according to claim 1 or 2, wherein the heat exchanger is at least 30 mV lower than the potential.   The heat exchanger according to any one of claims 1 to 3, wherein a potential difference between the core material of the tube and the outer fin is in a range of 120 to 220 mV.   The heat exchanger according to any one of claims 1 to 4, wherein the sacrificial material further contains Ti: 0.3% or less in terms of mass%.

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