JPH09268339A - Al alloy brazing sheet for vacuum brazing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al alloy brazing sheet suitable for use in a heat exchanger to be joined and assembled by vacuum brazing and having excellent corrosion resistance. SOLUTION: This Al alloy brazing sheet is constituted of an Al alloy core material 5, having a composition consisting of, by mass, 0.01-1.0% Si, 0.05-0.8% Fe, 0.3-1.2% Mn, 0.1-1.0% Cu, 0.01-0.20% Mg, 0.01-0.20% Ti, and the balance Al with inevitable impurities, and an Al-Si-Mg brazing filler metals 3, 3', applied to both sides of the core material at 5-20% cladding rate per side. Further, an intermediate layer 4, of >=30μm thickness, composed of an Al alloy consisting of 0.5-2.0% Mg and the balance Al with inevitable impurities, is provided, at <=35% cladding rate, between the brazing filler metal on the side C to be the outside surface of a heat exchanger and the core material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent corrosion resistance suitable for joining and assembling Al alloy heat exchangers for automobiles and various industries by brazing, particularly vacuum brazing. The present invention relates to an Al alloy brazing sheet for vacuum brazing.

[0002]

2. Description of the Related Art Brazing is an effective means for manufacturing a complex structure made of an aluminum alloy. Vacuum brazing, which does not require a flux, has been widely used because it has no pollution concerns. Is being done. Vacuum brazing is performed by using a brazing sheet in which Al or an Al alloy is used as a core material and clad on one or both sides thereof using an Al alloy brazing material as a skin material, and is formed into various shapes. This is a method of assembling into an exchanger and heating it in a vacuum to perform brazing.

[0003] Brazing sheets for vacuum brazing include:
Various aluminum alloys for core materials and aluminum alloy brazing materials for skin materials have been developed.
It is standardized by IS-Z-3263 and JIS-H-4000. As a brazing sheet for vacuum brazing used in a heat exchanger, JIS-30 is used as a core material.
03 (representative example Al-0.15 mass% Cu-1.1 m
(ass% Mn alloy, mass% is simply referred to as% hereinafter),
JIS-3005 (Representative example Al-1.1% Mn-0.4
% Mg alloy), JIS-3105 (typical example Al-0.6)
% Mn-0.6% Mg alloy) as a skin material according to JIS-4
004 (representative example Al-10% Si-1.5% Mg alloy), JIS-4104 (representative example Al-10% Si-)
A 1.2% Mg-0.1% Bi alloy) brazing material is usually used. The brazing sheet has a thickness of 0.2.
It is about 1.2 mm, and the clad ratio of the brazing material is 5 to 20% on one side with respect to the total plate thickness, and the brazing material is clad on one side or both sides.

As an aluminum alloy heat exchanger having a hollow structure using such a brazing sheet, a drone cup type evaporator, an oil cooler, a radiator and the like are manufactured. For example, as shown in FIG. 4, in the Delon cup type evaporator 10, a brazing sheet is formed into a member 1 shown in FIGS. 1 and 2, and the member 1 is laminated as shown in FIG. The corrugated fins 2 are arranged between the members 1, and the side plates 6 ^, 6 ^, the refrigerant inlet pipe 7 and the refrigerant outlet pipe 8 are arranged and assembled, and these are vacuum brazed. ．
About 87 in a vacuum of 3 × 10 ^{−3 to} 1.3 × 10 ⁻² Pa.
It is performed by heating to 3K.

[0005]

In recent years, along with the weight reduction of automobiles, it has been demanded that materials used for these heat exchangers have a thinner plate thickness and higher strength. As a measure to cope with this, Cu is added to the core material of the brazing sheet to obtain high strength. However, Cu added to the core material diffuses into the molten brazing material during the brazing heat and is discharged and concentrated in the eutectic part when the brazing material solidifies after the brazing heat. Therefore, a brazing sheet having a large amount of Cu in the core material has a problem that the Cu layer diffused in the brazing material becomes a starting point of corrosion and the corrosion progresses faster. on the other hand,
The environment in which the heat exchanger for automobiles is used varies, but especially in regions with severe corrosive environments (such as Southeast Asia and the Middle East), it is a drone cup type heat exchanger with excellent corrosion resistance. The development of a brazing sheet for use in is strongly desired. An object of the present invention is to find a heat exchanger having excellent corrosion resistance as described above, and an Al alloy brazing sheet for vacuum brazing used in the heat exchanger.

[0006]

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that in order to improve the corrosion resistance of a brazing sheet member, a brazing filler metal is added to the brazing filler metal during the brazing heat by an intermediate layer. It was found that it is effective to provide the brazing sheet with the effect of preventing the diffusion of Cu into the material and the sacrificial anode effect. The present invention has been made based on the above findings.

That is, the present invention is an Al alloy brazing sheet for a heat exchanger, which comprises a press-molded brazing sheet joined by vacuum brazing to form a tank portion and a refrigerant passage. 01 to 1.
0%, Fe: 0.05 to 0.8%, Mn: 0.3 to 1.
2%, Cu: 0.1-1.0%, Mg: 0.01-0.
2%, Ti: 0.01-0.2%, balance Al
And an Al alloy core material consisting of unavoidable impurities, and an Al-Si-Mg brazing material coated on both surfaces thereof with a clad ratio of 5 to 20% on one surface, and further on the outer surface of the tank portion and the refrigerant passage. Between the brazing material and the core material on the side to be Mg, an Al alloy containing Mg: 0.5 to 2.0%, the balance being Al and inevitable impurities, and having a thickness of 3
An brazing sheet made of Al alloy for vacuum brazing, characterized in that an intermediate layer having a thickness of 0 μm or more and a clad ratio of 35% or less is provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The core material, brazing material and intermediate layer of the brazing sheet made of an Al alloy for vacuum brazing according to the present invention will be described in detail below. 1. Alloy composition of core material First, A used for the core material of the brazing sheet of the present invention
The 1-alloy is an Al-Si-Fe-Mn-Cu-Mg-Ti alloy, and the significance of the additional element and the reason for limiting the range will be described. Si precipitates an intermetallic compound with Mn and Fe and contributes to the improvement of strength. Addition amount is 0.05%
If it is less than 1.0%, the effect of improving the strength is not sufficient, and if it exceeds 1.0%, there is a risk of melting the core material during brazing heating. Therefore, the amount of Si added is specified to be 0.05 to 1.0%.

Fe contributes to the improvement of strength by precipitating an intermetallic compound with Mn. If the addition amount is less than 0.05%, the effect of improving the strength is not sufficient, and if it exceeds 0.8%, huge crystallized substances are generated during casting, and the recrystallized grain size of the core material becomes small during brazing heating, Abnormal diffusion of the brazing material into the core material occurs, and the brazing property deteriorates. Therefore, the addition amount of Fe is set to 0.05 to 0.8%, but when the Mn / Fe ratio becomes large, the precipitation of Al-Mn-Fe-based intermetallic compounds that can be the starting point of corrosion is suppressed, From the viewpoint of improving the corrosion resistance, it is more preferably 0.2 to 0.4%.

Mn is an element necessary for dispersing an intermetallic compound in the alloy and improving the strength. If this amount is less than 0.3%, the effect of improving the strength is not sufficient and 1.2
%, The moldability is lowered, and there is a risk that molding cannot be performed as a laminated evaporator plate. Further, when brazing, the amount of the brazing filler metal diffused into the core material is increased and the brazing ability is deteriorated. Therefore, the range is set to 0.3 to 1.2%, but it is more preferably set to 0.8 to 1.1% from the viewpoint that the corrosion resistance is improved as described above when the Mn / Fe ratio is increased.

Cu acts as a solid solution in the core material to improve the strength of the core material. Further, by making a solid solution in the core material, the potential of the core material is made noble and the potential difference between the core material and the sacrificial material, which is the intermediate layer, is increased to further enhance the sacrificial anode effect of the intermediate layer. However, if the addition amount is less than 0.1%, it does not contribute to the strength improvement. Further, if the addition amount exceeds 1.0%, CuAl ₂ is precipitated in the grain boundary of the core material during the brazing heating / cooling process and not only impairs the corrosion resistance of the core material but also diffuses into the brazing material during brazing heating. This increases the amount and increases the starting point of corrosion of the brazing material itself. If the amount added exceeds 1.0%, the core material may be melted by heating at 873K. Therefore, the addition amount of Cu is set to 0.1 to 1.0%, more preferably 0.3 to 1.0%.

[0012] Mg forms a solid solution in the core material as in the case of Cu, and contributes to the strength improvement of the core material. If the addition amount is less than 0.01%, it does not contribute to the strength improvement, and if it exceeds 0.2%, intergranular corrosion occurs in the core material and the corrosion resistance is impaired. Therefore, M
The addition amount of g is 0.1 to 0.2%.

The addition of a trace amount of Ti has the effect of refining the structure of the ingot. Further, it has a function of layering the corrosion and also has an effect of improving the corrosion resistance. In the present invention, 0.01 to 0.20% is added from the viewpoint of corrosion resistance. If the added amount is less than 0.01%, there is no effect, and if it exceeds 0.20%, it becomes difficult to manufacture the material. The optimum addition amount is preferably about 0.10 to 0.20%.

Cr, Zn, etc. are unavoidable impurities other than the above elements in the core material, but generally accepted ranges, that is, Cr is 0.20% or less and Zn is 0.40%.
If it is below, there is no particular problem.

2. About brazing material There is no particular limitation on the brazing material used in the present invention. Al-Si-Mg usually used for vacuum brazing
System brazing material, namely 4004 (typical example Al-10% Si-
1.5% Mg alloy), 4104 (typical example Al-10% S)
i-1.2% Mg-0.1% Bi alloy) or the like can be used. Also, regarding the clad ratio of the brazing filler metal, the normal clad ratio, that is, 5 to 20% per one side of the total plate thickness
Can be used. In the case of the present invention, both sides of the plate are clad.

3. About Intermediate Layer Next, the Al—Mg alloy used for the intermediate layer of the brazing sheet according to the present invention will be described. The Al-Mg alloy used for the intermediate layer serves to prevent the element Cu of the core material from diffusing into the brazing material during brazing and heating. In the Al-Mg alloy material that is the intermediate layer, Mg in the alloy forms a solid solution during the brazing and heating, and becomes less base in potential than the brazing material and the core material. This has the effect that the corrosion generated from the brazing material stops at the intermediate layer due to the sacrificial anode effect. In order to obtain this effect, Mg in the present invention is 0.1-2.
Add 0%. The reason for setting Mg in this range is that if the addition amount is less than 0.1%, this effect is small, and if it exceeds 2.0%, excessive corrosion occurs. Another reason is M
If the addition amount of g exceeds 2.0%, there is a problem in that it is not joined to the brazing material and the core material in the combined rolling (clad rolling) in the hot rolling.

Elements other than Mg in the Al-Mg alloy of the intermediate layer, which are inevitable impurities, include Si, Fe, Cr, and
There are Zn, etc., but the generally accepted range is Si0.6.
% Or less, Fe 0.7% or less, Cr 0.10% or less, Zn
0.20% or less, but especially Si is 0.2% or less, F
It is more preferable that e be 0.25% or less.

Next, the Al alloy intermediate layer is provided on one of the core materials, that is, on the surface corresponding to the outer side of the tank portion and the refrigerant passage of the heat exchanger, and the brazing material is further clad thereon. The brazing material is directly clad on the other surface of the core material. The reason why the intermediate layer is provided on the surface corresponding to the outside of the tank portion and the refrigerant passage is that the outside is more severe in the corrosive environment.

In the intermediate layer of the brazing sheet made of Al alloy according to the present invention, the thickness is set to 30 μm or more. When the thickness of the intermediate layer is less than 30 μm, Cu of the core material is not added when the brazing heat is applied. This is because it will pass through the intermediate layer and diffuse to the brazing material. When Cu reaches the brazing filler metal, it is discharged to the eutectic part when the brazing material melts and solidifies and becomes concentrated, which becomes a starting point of corrosion and reduces corrosion resistance.

The reason why the clad ratio of the intermediate layer is 35% or less with respect to the total plate thickness is that there are many portions where the core material is sacrificed and corroded if the intermediate layer becomes too thick with respect to the total plate thickness. This is because when the corrosion progresses too much and the corrosion progresses, the remaining plate thickness becomes thin, and it becomes impossible to withstand the internal pressure of the heat exchanger. Further, if the clad ratio exceeds 35%, it becomes difficult to roll each of the brazing filler metal and the core material to a predetermined clad ratio in hot rolling. Therefore, Al-Mg
The intermediate layer of the alloy has a thickness of 30 μm or more and the clad ratio is 35% or less.

The structure of the Al alloy brazing sheet according to the present invention is as described above. The sectional structure of this sheet (plate) is shown in FIG.
That is, the brazing material 3 is provided on the side C corresponding to the outer surface of the heat exchanger tank portion and the refrigerant passage of the Al alloy core material 5 with the intermediate layer 4 interposed therebetween, and the other side of the core material 5 (corresponding to the inner surface). wax material 3 on the side) ^D, a four-layer structure in which a.

The Al alloy brazing sheet according to the present invention can be manufactured by a conventional method as in the conventional method. That is, a predetermined Al alloy material such as a core material, an intermediate layer material, and a brazing material is melt-cast, the ingot is subjected to a homogenizing heat treatment (soaking), and further, if necessary, is rolled to a predetermined thickness. Hot rolling, followed by cold rolling (annealing if necessary).

[0023]

EXAMPLES Next, examples of the present invention will be described in more detail in comparison with comparative examples and conventional examples. Various core ingots shown in Table 1 were manufactured, and after being face-cut, homogenized heat treatment was performed at 600 ° C. for 9 hours. Various intermediate layer materials with different Mg contents shown in Table 1 were combined on one surface of this ingot at a clad ratio of 5 to 40% with respect to the total plate thickness, and further on both outer surfaces thereof JIS-4004 alloy (Al-10). % Si-1.5% Mg alloy) was clad with 15% on one side, and this was heated to 490 ° C. and hot-rolled together. Subsequently, cold rolling, intermediate annealing, cold rolling, and final annealing (360 ° C. × 2 h) were performed, and the invention examples (No. 1 to 8) and the comparative example (N) shown in Table 1.
o. 9-12) brazing sheet having a thickness of 0.4 mm was produced. As shown in Table 1, brazing sheets (three-layer materials) of conventional examples (Nos. 13 to 14) in which no intermediate layer material was used were also manufactured.

The brazing sheet (annealed material) shown in Table 1 was press-formed into the shape shown in FIG. 1 to produce a refrigerant passage member for a heat exchanger. This was washed, laminated so that the intermediate layer side was the outer surface, and assembled into a heat exchanger (dron cup evaporator) having a shape as shown in FIG. The fin is
A corrugated fin made of 3203 alloy (Al-1.2% Mn alloy) was used.

Next, this was subjected to vacuum brazing addition heat at 873 K × 3 minutes in a vacuum of 6.7 × 10 ⁻³ Pa to obtain a Delon cup evaporator. The obtained evaporator was subjected to a JIS-H-8601 corrosion test (CASS test). Two months after the start of the test, the surface corrosion products were removed, the presence or absence of through pitting, and the pitting depth of the maximum pitting portion were measured and evaluated. The pit depth is
It was measured by the depth of focus method using an optical microscope. The measurement results are shown in Table 1. In addition to the above test,
The electric potentials of the core material, the intermediate layer material and the brazing material after brazing were measured and are also shown in Table 1.

[0026]

[Table 1]

As is clear from Table 1, the brazing sheet according to the present invention has the sacrificial anode effect and the effect of preventing Cu diffusion from the core material to the brazing material during the brazing heat by the intermediate layer, and thus the brazing sheet has In comparison, it can be seen that the corrosion resistance is remarkably excellent.

[0028]

As described in detail above, the present invention can significantly improve the corrosion resistance of one side of a corrosive environment which is severe in the use of an Al alloy brazing sheet. In this case, the corrosion life of the heat exchanger can be remarkably improved, and this has an industrially remarkable effect.

[Brief description of drawings]

FIG. 1 is a plan view showing a molded member for a drone cup evaporator.

FIG. 2 is a cross-sectional view taken along the line B-B ′ of FIG.

FIG. 3 is an enlarged cross-sectional view of a portion A of the member of FIG. 2, showing a cross-sectional structure of a conventional Al alloy brazing sheet.

FIG. 4 is an explanatory view showing an example of a heat exchanger (Drone cup evaporator), and is a schematic sectional view thereof.

FIG. 5 is a diagram showing a cross-sectional structure of an Al alloy brazing sheet according to the present invention.

[Explanation of symbols]

1 Refrigerant passage constituent member for a drone cup evaporator 2 Fins 3 Brazing material layer 4 Intermediate layer 5 Core material layer 6 Side plate 7 Refrigerant inlet pipe 8 Refrigerant outlet pipe 10 Heat exchanger (dron cup evaporator) C Heat exchanger tank part And the side corresponding to the outer surface of the refrigerant passage D The side corresponding to the tank section of the heat exchanger and the inner surface of the refrigerant passage

Claims (1)

[Claims] 1. An Al alloy brazing sheet for a heat exchanger, which comprises a press-molded brazing sheet joined by vacuum brazing to form a tank section and a refrigerant passage, the composition of which is Si: 0.01-1. 0.0 mass
%, Fe: 0.05 to 0.8 mass%, Mn: 0.3
~ 1.2mass%, Cu: 0.1-1.0mass
%, Mg: 0.01 to 0.2 mass%, Ti: 0.0
Al-Si containing 1 to 0.2 mass% and the balance being Al and inevitable impurities, and Al-Si coated on both surfaces thereof with a clad ratio of 5 to 20% on each surface.
-Mg-based brazing material, and further, between the brazing material and the core material on the outer surface of the tank portion and the refrigerant passage, Mg:
An Al alloy containing 0.5 to 2.0 mass% and the balance being Al and unavoidable impurities and having a thickness of 30.
An Al alloy brazing sheet for vacuum brazing, characterized in that an intermediate layer having a cladding ratio of 35 μm or more and a clad rate of 35% or less is provided.