JP3151152B2 - Evaporator with excellent corrosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporator having excellent corrosion resistance.

[0002] In this specification, the term "aluminum" is used to include aluminum and its alloys.

[0003]

2. Description of the Related Art For example, a serpentine type evaporator (1) as shown in FIGS. 1 and 2 is used for an air conditioner evaporator of an automobile.

The serpentine evaporator (1)
Is a single porous flat tube through which a heat exchange medium flows.
(2) is bent in a meandering shape, and fins (3) formed by bending a brazing sheet are interposed between the straight pipes of the tube (2) .The tubes (2) and the fins (3) are alternately arranged. It is brazed and integrated.

[0005] On the other hand, such an evaporator may be made to have a corrosion resistance by using a specific material for a tube and a fin in order to withstand use in a corrosive environment. . For example, as a typical material example of the above-mentioned serpentine evaporator, a tube is formed of an Al-Mn-Cu-based alloy, a fin brazing sheet core material is JIS A3203, and a skin material is JI.
Some are formed of SA4343. In this method, a material whose pitting potential is lower than that of a tube is used as a skin material of the fin brazing sheet, and the tube is sacrificed and protected by the fin.

As a method of brazing such an evaporator, fluxless vacuum brazing has been generally used.

[0007]

However, in an area where corrosion progresses sharply in an acidic atmosphere such as Southeast Asia, the above-mentioned materials cannot sufficiently cope with the problem.
Further, there is a demand for an evaporator having good corrosion resistance.

The present invention has been made in view of such technical background, and an object of the present invention is to provide an evaporator having excellent corrosion resistance which can be sufficiently used even in an acidic atmosphere.

[0009]

In order to achieve the above object, an evaporator according to the present invention provides a tube having a surface of Zn.
By coating and using a Zn-containing aluminum brazing alloy for the skin material of the fin brazing sheet,
In addition to sacrificial corrosion protection of the tube with fins, the surface of the tube is preferentially corroded so that a hole is not formed in the tube. That is, the evaporator according to the present invention is an evaporator in which an aluminum tube (2) and fins (3) made of an aluminum brazing sheet in which a cladding material is clad on both surfaces of a core material are alternately arranged and integrated with brazing. The tube (2)
The Zn sprayed layer has a Zn adhesion amount of 5 to 15 g / m ² (1
5 g / m ² ), and the skin material of the brazing sheet (3) is Si; 3 to 15 wt% and Zn;
The tube (2) and the fins (3) are brazed using a fluoride-based flux, containing 5 to 2.0 wt%, the balance being an Al brazing alloy consisting of Al and impurities. It is characterized by.

In the evaporator of the present invention, the tube (1) is preferably made of JIS A1000-based pure aluminum, such as 1100 alloy, among aluminum because of excellent workability, strength and corrosion resistance.

The Zn sprayed on the surface of the tube (2)
Is diffused to the surface layer by brazing heat and makes the pitting potential of the surface layer of the tube lower than that of the deep part of the tube, so that the surface layer is preferentially and uniformly corroded, so that corrosion is limited to the surface layer Prevents reaching deep and prevents pitting.
The Zn deposition amount in the Zn sprayed layer is 5 to 15 g / m ^2.
(Excluding 15 g / m ² ). If it is less than 5 g / m ² , a sufficient Zn diffusion layer cannot be formed, so that the sacrificial anticorrosion effect is poor and the required corrosion resistance cannot be expected. Meanwhile, 1
If it exceeds 5 g / m ² , the above effect is saturated and material is wasted.

In the present invention, Z on the surface of the tube (2)
The reason why the n layer is formed by thermal spraying is that, as described above, a Zn layer having a sufficient thickness can be formed uniformly, and a diffusion layer having a sufficient thickness can be formed uniformly. In the case of Zn coating by a method other than thermal spraying, for example, in the case of Zn plating, the film formed is a thin film, so that the Zn diffusion layer also becomes thin. Particularly, in the bent portion (2a) of the tube (2), since the plating film is stretched by bending,
The diffusion layer becomes thinner, and the required anticorrosion effect cannot be expected. Further, if plating is performed after the bending, it is possible to prevent a reduction in the anticorrosion effect due to the bending, but it is necessary to prevent the plating solution from entering the tube (2), which increases the processing cost. On the other hand, when the Zn layer is formed by thermal spraying, the layer thickness can be increased.
In addition to the case where the thermal spraying is performed after the bending process of (2), even when the thermal spraying process is performed after the thermal spraying, the thermal sprayed layer of the bent portion (2a) can be ensured in a thick state, and the Zn diffusion layer is also assumed to be thick, so that the bent portion ( A reduction in the anticorrosion effect in 2a) can be prevented.

The method of thermal spraying is not particularly limited as long as a film having a predetermined thickness such as a flame type, an arc type, or a plasma type can be formed, and the shape of the thermal spraying material is not limited to a type such as a rod, a wire, and a powder.

In the brazing sheet constituting the fin (3), the skin material may be a general-purpose brazing material such as Al-3 to Al-3.
The tube (2) is protected from corrosion by using an Al brazing alloy in which Zn is blended with a 15 wt% Si alloy and making the pitting potential on the surface of the fin (3) lower than that of the tube body. The Al
In the composition of the brazing alloy, the Si content needs to be in the above range in order to obtain an appropriate melting point for brazing an aluminum material. A particularly preferred lower limit is 7.9 wt% and an upper limit is 9.5 wt%. %. The Zn content is
When the amount is too small, the anticorrosion effect is poor. On the other hand, when the amount is excessive, the initial corrosion becomes severe due to the high concentration, and the generation of white powder as a corrosion product becomes remarkable. There is. A particularly preferred lower limit of the Zn content is 0.9 wt%, and an upper limit is 1.4 wt%. The balance is Al and impurities, but the presence of trace elements added for improving the brazing function is permissible.

The material of the core material of the brazing sheet for the fins (3) is not particularly limited.
The cladding ratio of the skin material is preferably 5 to 15%, which is almost the same as that of a conventional brazing sheet.

Tube (2) material and fin as described above
(3) The type of the evaporator using the material is not particularly limited, but even when a Zn sprayed layer is formed before bending, a thick Zn layer of the bent portion (2a) can be ensured, and as a result, the bent portion (2
Since excellent corrosion protection against a) can be ensured, the present invention is preferably applied to a serpentine-type evaporator that bends the tube (2) in a meandering manner.

The brazing of the tubes (2) and the fins (3) is performed using a fluoride-based flux. According to the flux brazing, unlike the vacuum brazing that does not use the flux, which has been performed in the production of the conventional evaporator, the brazing can be performed while preventing the evaporation of Zn from the surface of the tube (2). Further, since the fluoride-based flux itself is non-corrosive, it is advantageous in that cleaning after brazing is not required as compared with brazing using a chloride-based flux. In addition, by using flux
(2) Since the Zn coating layer on the surface is coated with the flux, there is an advantage that the inorganic odor of Zn can be suppressed and the appearance quality can be maintained by coating the white powder of Zn. 45.8% KF-54.2% as a fluoride-based flux
Complex mixture eutectic composition or is which is substantially complexing include a composition range close to the AlF3, KAlF _4, K ₂ Al
F ₅ , K ₃ AlF ₆ , AlF ₃ , CsF, BiF ₃ , LiF
Etc. can be exemplified.

Next, an example of a method for manufacturing an evaporator according to the present invention will be described.
After fabricating (2), Zn spraying is performed on the tube (2) surface. The thermal spraying is preferably performed on an extruded material extruded from an extruder. By doing so, the extrusion process and the thermal spraying process can be performed continuously, and in addition to being efficient, thermal spraying is performed at a high surface temperature immediately after extrusion, so that the tube of the Zn thermal spray layer ( 2) It is possible to increase the adhesion to the surface and to diffuse a part of the sprayed layer to the surface.

Next, when the evaporator is of the serpentine type, the tube (2) is bent in a meandering shape. Of course, the Zn sprayed layer may be formed after bending the tube (2).

On the other hand, a fin (3) is prepared by bending a desired aluminum double-sided brazing sheet.

Then, the tube (2) and the fins (3) are assembled, and if necessary, other evaporator components are assembled to form an evaporator assembly.

Next, a flux is applied to the evaporator assembly. The method of application is not particularly limited, but the simplest method is to adopt an immersion method in which the evaporator assembly is immersed in a suspension in which the flux is suspended in a solvent.

Next, the evaporator assembly to which the flux has been applied is placed in an atmosphere of an inert gas such as N ₂ gas or the like.
Heat at 50 ° C. to melt the brazing material (skin material) on the surface of the fin (3) and braze the fin (3) and the tube (2). Due to this brazing heat, the Zn sprayed layer on the surface of the tube (2) diffuses into the tube (2) in the thickness direction to form a Zn diffusion layer.

In the evaporator of the present invention, the tube (2) is formed by sacrificial corrosion of the Zn diffusion layer on the surface of the tube (2) and the skin material of the fin (3) containing Zn.
Corrosion to the deep part is suppressed not only in a non-acidic atmosphere but also in an acidic atmosphere, and fatal corrosion as a heat exchanger, which has a hole in the tube (2), is avoided.

Since the Zn layer is formed by thermal spraying and has a sufficient thickness, the outer periphery of the bent portion (2a) is formed by an evaporator of a type in which the tube (2) is bent in a meandering shape. Even when the Zn layer is thinly extended on the surface, sufficient anticorrosion performance can be ensured.

[0026]

EXAMPLE A serpentine type evaporator (1) shown in FIGS. 1 and 2 was manufactured by changing the materials of a tube (2) and a fin (3) and a brazing method. In FIG. 1, (4) shows an outlet header, and (5) shows an inlet header.

As the tube (2), a porous flat extruded tube shown in FIG. 2 was used, and a Zn layer was formed by thermal spraying or plating by a conventional method before bending. For Comparative Examples 1 and 5, the extruded materials were used as they were without performing these surface treatments. Table 1 shows the material of the tube (2), the Zn coating method, and the Z formed by the Zn coating.
The Zn adhesion amount of the n-layer is shown.

The fins (3) are constituted by a brazing sheet in which a skin material is clad on both sides of a core material. Table 1 shows the material of the core material, the material of the skin material, the thickness, and the single-sided cladding ratio of the skin material.

Then, as shown in FIGS. 1 and 2, the tube (2) and the fin (3) are bent in a meandering manner, and the fin (3) is inserted between the straight pipe portions of the tube (2). It was assembled in a state where it was interposed, and further brazed with the separately manufactured headers (4) and (5) arranged at both ends of the tube (2). For brazing, either flux brazing using a fluoride-based flux or vacuum brazing using no flux was employed. The brazing with the fluoride-based flux was performed by immersing the heat exchanger assembly in a flux suspension and drying, and then heating in a N 2 gas atmosphere at 600 ° C. for 5 minutes. In addition, vacuum brazing is 10
^This was performed by heating at 600 ° C. for 5 minutes in a vacuum of ⁻⁴ to 10 ⁻⁵ Torr. Table 1 shows the brazing method of each example.

For each of the serpentine-type evaporators (1) manufactured in this manner, the inorganic odor (Zn
The odor and the appearance were relatively evaluated, and a corrosion test was performed by SWATT shown below to examine the time until the leakage and the location of the leakage in an acidic atmosphere, and the corrosion resistance was evaluated. Table 1 shows the evaluation results. [SWATT] AS
TM artificial seawater (NaCl: 20.6 g / l, MgCl ₂
6H ₂ O: 6 g / l, Na ₂ SO ₄ : 4.8 g / l, C
uCl ₂ .2H ₂ O: 1.4 g / l, KCl: 0.8 g /
1, NaHCO ₃ : 0.2 g / l, KBr: 0.2 g / l
l) and acetic acid were mixed at a ratio of 1 liter of artificial seawater / 10 ml of acetic acid, and the mixed solution (pH 2.8-3.0, liquid temperature 49) was mixed.
℃) for 30 minutes, and then wet (49 ° C, 98%
RH) for 90 minutes, and this was repeated for one cycle of 120 minutes until the evaporator leaked.

[0031]

[Table 1]

From the results shown in Table 1, it was confirmed that all the evaporators of the examples of the present invention did not corrode from the tube, had excellent corrosion resistance, had no inorganic odor, and had good appearance quality.

[0033]

As described above, the present invention relates to an evaporator in which an aluminum tube and fins made of an aluminum brazing sheet in which a cladding material is clad on both sides of a core material are alternately arranged and integrated with brazing. In the above, the tube has a Zn sprayed layer formed on a surface portion thereof, and a skin material of the brazing sheet is Si;
wt. and Zn; 0.5 to 2.0 wt.%, the balance being an Al brazing alloy consisting of Al and impurities, and the tube and the fins being brazed using a fluoride-based flux. Therefore, the tubes are sacrificed and protected by the fins, and the tubes themselves are sacrificed and corroded only on the surface to prevent corrosion to the deep part. Due to such anticorrosion behavior, excellent corrosion resistance as an evaporator can be obtained.

Since the Zn layer is formed by thermal spraying, it can be formed to a sufficient thickness.
Even when the tube is bent after the thermal spray layer is formed, a thick Zn thermal spray layer at the bent portion can be ensured, and a sufficient Zn diffusion layer can be formed at that portion. For this reason, even in an evaporator of a type in which the tube is bent in a meandering shape, the tube can have excellent corrosion resistance.

[Brief description of the drawings]

FIG. 1 is a plan view of a serpentine evaporator according to an embodiment of the present invention.

FIG. 2 is a partially enlarged perspective view of FIG.

[Explanation of symbols]

 2 ... Tube 3 ... Fin

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 4/08 C22C 21/00 F28F 19/06

Claims (1)

(57) [Claims] 1. A aluminum tubes (2), a fin (3) of cladding material on both surfaces of the core material is made of an aluminum brazing sheet which is clad are alternately arranged, in integrated Ebaboreta brazing the tube (2) indicates the amount of Zn deposited on the surface layer
Formed at 5 to 15 g / m ² ( excluding 15 g / m ² ) ,
The skin material of the brazing sheet (3) is Si;
wt. and Zn; 0.5 to 2.0 wt.%, the balance being made of an Al brazing alloy consisting of Al and impurities, and wherein the tube (2) and the fin (3) use a fluoride-based flux. An evaporator with excellent corrosion resistance characterized by being brazed .