JPH07179969A - Laminated brazing sheet made of aluminum alloy for heat exchanger - Google Patents

Abstract

PURPOSE:To prepare a laminated brazing sheet made of aluminum alloy for heat exchanger, improved in local corrosion resistance without causing an increase in weight, etc., by coating the surface of a core material, made of Al alloy of specific composition, with a sacrificial anode layer of Al alloy of specific composition and an Al-Si-Mg brazing filler metal. CONSTITUTION:An Al alloy, which has a composition containing, by weight, 0.4-1.2% Si, 0.2-0.6% Mg, and 0.01-0.4% Cu or 0.1-1.2% Mn and containing, if necessary, prescribed amounts of Hf, Mo, Nb, Ta, Ti, V, W, and Zr, is used as a core material. A sacrificial anode layer of an Al alloy is provided to one side or both sides of this core material. This Al alloy has a composition containing one or more kinds among 0.01-0.3% Hf, 0.01-0.2% Mo, 0.01-0.2% Nb, 0.01-0.2% Ta, 0.01-0.3% Ti, 0.01-0.2% V, and 0.01-0.1% W, containing 0.01-3.0% Zn or 0.01-0.05% In, and also containing, if necessary, a prescribed amount of Zr. The surface of this sacrificial anode layer is coated with an Al-Si-Mg brazing filler metal containing at least 6.5-11.5% Si.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite brazing sheet having a three-layer structure or a four-layer structure or more, which has excellent local corrosion resistance and is particularly suitable for use as a structural member of an aluminum alloy heat exchanger. It is about.

[0002]

2. Description of the Related Art Conventionally, Al is used for heat exchangers for automobiles.
Alloys are widely used, and the members are generally made of Al alloy core material containing Mn and the like, and Al-Si-
A brazing sheet having a two-layer structure coated with a Mg-based brazing material is used. When a heat exchanger is manufactured using this brazing sheet, each brazing sheet is formed into a predetermined shape and assembled for each member, and the brazing sheet is heated in a vacuum furnace or the like for brazing and joining.

By the way, since the brazing material is originally inferior in corrosion resistance, and the heat exchanger using the brazing material is used in a corrosive environment, the brazing material after brazing is likely to be corroded. Further, during the brazing heat, the brazing material penetrates into the core material and Si of the brazing component diffuses into the core material, so that the core material becomes susceptible to intergranular corrosion. For this reason, when the brazing material is used as a heat exchanger, if the erosion generated in the brazing material reaches the core material, the erosion easily progresses deeper into the core material. As a result, a large amount of local intergranular corrosion occurs in the core material, and the durability of the heat exchanger is significantly reduced.

As a method of solving this problem, the applicant of the present application has already proposed to use a composite brazing sheet having a four-layer structure as a material for a heat exchanger (Japanese Patent Publication No. Sho 6).
2-61099). In this four-layer composite brazing sheet, a sacrificial anode layer of an Al alloy mainly containing Zn and Mn is provided as an intermediate layer on one side of a core material of an Al-Mn alloy, and an Al-Si brazing alloy is provided on this surface. Cover the material,
On the other hand, on the other surface side of the core material, Al mainly containing Zn
A four-layer structure is formed by providing a sacrificial anode layer of an alloy.
According to this four-layer composite brazing sheet, by the action of Zn in the sacrificial anode layer provided as the intermediate layer, corrosion spreads laterally and corrosion in the depth direction is suppressed, and as a result, the core material is protected. It is a thing.

[0005]

However, even in the above-described improvement method, when the heat is applied to the solder, the solder penetrates into the sacrificial anode layer and makes the sacrificial anode material susceptible to intergranular corrosion. There is a problem that the effect of preventing erosion in the layer is reduced. Also, the sacrificial anode layer itself,
Since it is composed of a material with low strength, it is necessary to increase the plate thickness of the entire brazing sheet to compensate for the strength decrease in order to secure the necessary strength as a heat exchanger. However, there is a problem that the weight increases as a result. The present invention has a fundamental object to solve the above problems, and an object thereof is to provide a composite brazing sheet for an aluminum alloy heat exchanger with improved local corrosion resistance without causing an increase in weight and the like. To do.

[0006]

In order to solve the above problems, the inventors of the present invention have diligently studied a method for preventing the penetration of wax into the sacrificial anode layer, and as a result, the higher the melting point of the sacrificial anode layer, the more
It was found that the degree of penetration was low. Then, the inventors conducted various tests to find an alloy having a higher melting point than pure Al and higher strength at high temperature and room temperature, and as a result, found the following facts. (1) The melting point of an alloy containing Hf, Mo, Nb, Ta, Ti, V, and W is higher than that of pure Al. (2) In these alloys, the content element and the Al compound are formed by adjusting the content, and the fine and even distribution thereof significantly improves the strength at high temperature and room temperature. (3) By adding these elements in combination,
The above effects are more sufficiently exhibited.

The composite brazing sheet for an aluminum alloy heat exchanger of the present invention is made on the basis of the above findings,
Some are further improvements, and specifically,
% By weight, Si: 0.4 to 1.2%, Mg: 0.2 to
0.6%, further Cu: 0.01-0.4
%, Mn: 0.1 to 1.2% of one kind or two kinds, Hf: 0.01 to 0.3% on one surface of the Al alloy core material containing the balance of Al and unavoidable impurities. Mo: 0.01
~ 0.2%, Nb: 0.01 to 0.2%, Ta: 0.0
1 to 0.2%, Ti: 0.01 to 0.3%, V: 0.0
1-0.2%, W: 0.01-0.1% of 1 or 2
Containing more than one species, further Zn: 0.01-3.0%,
In: A sacrificial anode layer of an Al alloy containing 0.01 to 0.05% of one type or two types and the rest of Al and unavoidable impurities is provided, and at least Si: Al-Si-containing 6.5-11.5%
It is characterized by being coated with a Mg-based brazing material.

The second invention is characterized in that the sacrificial anode layers are provided on both surfaces of the Al alloy core material, and one or both surfaces of the sacrificial anode layers are coated with the brazing material. .

A third aspect of the invention is the same as the first or second aspect of the invention, in which H is added in addition to the above components.
f: 0.01 to 0.3%, Mo: 0.01 to 0.2%,
Nb: 0.01 to 0.2%, Ta: 0.01 to 0.2
%, Ti: 0.01 to 0.3%, V: 0.01 to 0.2
%, W: 0.01 to 0.1%, Zr: 0.01 to 0.2
% Of one kind or two or more kinds.

A fourth invention is the above-mentioned first, second or third invention.
In the invention (1), the sacrificial anode layer component further contains Zr: 0.01 to 0.2% by weight, in addition to the above components. In the first aspect of the invention, the other surface side of the core material may be exposed, and a sacrificial anode layer having a component different from that of one sacrificial anode layer or a surface coating layer may be provided. For example, as the sacrificial anode layer having different components, a sacrificial anode layer made of an Al alloy containing Zn: 0.3 to 3.0% can be used. Further, the sacrificial anode layer in the second invention does not necessarily have to have the same composition as that on the other surface side of the core material, and may have different components as long as they are within the specified components.

[0011]

In other words, according to the present invention, since the penetration of the braze into the sacrificial anode layer during brazing is prevented, the diffusion amount of Si is also very small. Therefore, the effect of Si for promoting intergranular corrosion is removed, and the anticorrosion effect of the sacrificial anode layer is sufficiently exerted. Specifically, since the core material contains Si, Cu or Mn, it is electrochemically noble, and the sacrificial anode layer, which is less base, laterally diffuses corrosion and prevents corrosion of the core material. . In addition, Zn, In
When the sacrificial anode layer is contained, the sacrificial anode layer becomes electrochemically more base, so that the potential difference from the core material becomes large and the anticorrosion effect is further improved. Further, according to the present invention, a fine compound is dispersed in the sacrificial anode layer to improve the strength of the sacrificial anode layer. Further, according to the third aspect, the effect of preventing Si diffusion is obtained even by the core material itself, so that the corrosion resistance is further improved and the strength is also improved. Further, according to the fourth aspect of the invention, the effect of further improving the strength of the sacrificial anode layer can be obtained.

Next, the reasons for limiting each component in the present invention will be described. (Core material) Si: 0.4 to 1.2% Mg: 0.2 to 0.6% These components generate Mg2Si which is a fine precipitate, and secure the strength by age hardening. Further, Si makes the core material electrochemically precious like Cu and Mn described later, and improves the corrosion resistance. If the content of each of these components is less than the lower limit, the above effect cannot be obtained.On the other hand, if the content exceeds the upper limit, not only the risk of local melting of the core material due to the lowering of the melting point occurs, but also intergranular corrosion causes corrosion resistance. Since it deteriorates, it is limited to the above range.

Cu: 0.01 to 0.4% Mn: 0.1 to 1.2% These elements increase the strength and make the potential of the core material noble to improve the corrosion resistance. However, if the content of each is less than the lower limit, the desired effect is not sufficient, while
If it exceeds the upper limit, intergranular corrosion occurs and the corrosion resistance is deteriorated, so the content is limited to the above range. Hf: 0.01 to 0.3%, Mo: 0.01 to 0.2
%, Nb: 0.01 to 0.2%, Ta: 0.01 to 0.
2%, Ti: 0.01 to 0.3%, V: 0.01 to
0.2%, W: 0.01 to 0.1%, Zr: 0.01
.About.0.2% These elements prevent Si from diffusing and lowering the corrosion resistance, similarly to the reason for addition in the sacrificial anode layer described later. The deterioration of the corrosion resistance of the core material due to the diffusion of Si is prevented by the sacrificial anode layer in the present invention, but in order to make this more reliable, the above-mentioned elements are added to the core material as desired. Further, the addition of these elements also has the effect of improving the strength. The reason for limiting the range of the above components is the same as that for the sacrificial anode layer, and it is desirable to similarly control the total amount to 0.8% at maximum.

(Sacrificial Anode Layer) Hf: 0.01 to 0.3%, Mo: 0.01 to 0.2
%, Nb: 0.01 to 0.2%, Ta: 0.01 to 0.
2%, Ti: 0.01 to 0.3%, V: 0.01 to
0.2%, W: 0.01 to 0.1% These elements raise the melting point of the Al alloy and prevent the penetration of the brazing filler metal into the core material and the diffusion of Si during brazing. It also produces finer compounds to improve strength. If the content of these elements is less than 0.01%, the desired effect is not sufficient. On the other hand, if the content of each element exceeds the upper limit, not only there is no further improvement effect, but also the dispersed particles of the compound become coarse, Since the rolling property and strength of the material are deteriorated, they are set within the above ranges. It should be noted that the above effects are further exhibited by the combined addition of these elements. However, in the case of multiple addition, it is desirable to regulate the total amount to 0.8% at maximum. The reason is that if the total amount exceeds 0.8%, the compound becomes coarse and the rolling processability is impaired.

Zn: 0.01-3.0% In: 0.01-0.05% These components make the potential of the sacrificial anode layer base and increase the sacrificial anode action to cause erosion in the depth direction. It has a further suppressing effect. However, if it is less than the lower limit, the action is insufficient, and if it exceeds the upper limit, there is a problem that the self-corrosion rate increases and wear is reduced at an early stage. Zr: 0.01 to 0.2% Zr is optionally contained in order to enhance high-temperature strength. However, if less than 0.01%, the effect is not sufficient,
Further, if it exceeds 0.2%, not only is there no further effect, but also the compound becomes coarse and the rolling workability is impaired, so the above range is made.

(Brazing material) Si: 6.5 to 11.5% Si is added to lower the liquidus temperature of Al and to enhance the fluidity of the brazing material. However, the Si content is 6.
If it is less than 5%, the above effect is insufficient, and 1
If it exceeds 1.5%, the liquidus temperature rather rises and the fluidity decreases, so the above range is set. In addition, this brazing material contains an appropriate amount of Mg necessary for vacuum brazing. As an example of the content, Mg: 0.3 to 2.5% can be mentioned. Further, the brazing material may contain other components, for example, if necessary, Bi: 0.01-.
One or more of 0.3% and Be: 0.0002 to 0.0015% may be added. The above Bi and Be are added to improve the fluidity of the wax.

[0017]

EXAMPLE An Al alloy of the present invention having the composition shown in Tables 1 to 3 and a comparative Al alloy were melted by a usual method, and were hot-rolled and cold-rolled respectively for a core material, a sacrificial anode layer and a brazing material. I got a thin plate of. By laminating and clad these thin plates in the combinations shown in Table 4, 3 to 5 layers with a thickness of 1 mm can be obtained.
A layer of composite brazing sheet was obtained.

Next, the brazing sheet was simulated under vacuum of 10 ^-4 Torr by simulating vacuum brazing to 600
Heating was performed at 5 ° C for 5 minutes. Then, a tensile test piece was cut out from each of the brazing sheets to measure the tensile strength. Furthermore, as a corrosion test, a 500-hour CASS test, an aqueous solution spray test, and an alternating immersion test were performed on the brazing material surface side of each brazing sheet, and then the local corrosion number and the maximum erosion depth were measured for each test. . The results of the above tensile test and corrosion test are shown in Table 4.

As is clear from Table 4, the brazing sheet of the present invention has the results that the number of local corrosions is small and the erosion depth is shallow, and the erosion is effectively prevented and excellent brazing resistance is exhibited. ing. On the other hand, the brazing sheet of the comparative material has a large number of localized corrosion and reaches a deep erosion position, and is clearly inferior in local corrosion resistance. Further, the brazing sheet of the present invention has excellent local corrosion resistance, and in addition, all have high strength, whereas the comparative material does not have sufficient strength, Is also excellent in strength.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

As described above, according to the composite brazing sheet of the present invention, Si: 0.4 to 1.2%, M
g: 0.2 to 0.6%, further Cu: 0.05
On one or both sides of an Al alloy core material containing one or two of 0.4% and Mn: 0.1 to 1.2%.
0.01-0.3%, Mo: 0.01-0.2%, N
b: 0.01 to 0.2%, Ta: 0.01 to 0.2%,
Ti: 0.01 to 0.3%, V: 0.01 to 0.2%,
W: 0.01 to 0.1%, one or more, Zn:
0.01-3.0%, In: 0.01-0.05% 1
Al alloy sacrificial anode layer containing one or two kinds, optionally Zr: 0.01 to 0.2%, and at least Si: 6.5 to 1 on one or both surfaces of this sacrificial anode layer.
Since the Al-Si-Mg-based brazing material containing 1.5% is coated, the diffusion of Si from the brazing material to the sacrificial anode layer is prevented and the function of the sacrificial anode layer is not hindered. Corrosion is laterally diffused to prevent erosion of the core and improve local corrosion resistance of the heat exchanger. Also,
Since the strength of the sacrificial anode layer is improved, it is not necessary to reinforce the sacrificial anode layer by increasing the plate thickness, and the reduction in thickness and weight can be prevented.

Further, in addition to the above components, Hf:
0.01-0.3%, Mo: 0.01-0.2%, N
b: 0.01 to 0.2%, Ta: 0.01 to 0.2%,
Ti: 0.01 to 0.3%, V: 0.01 to 0.2%,
By containing one or two or more of W: 0.01 to 0.1% and Zr: 0.01 to 0.2%, an effect of preventing corrosion by the core material itself is obtained, and local corrosion resistance is improved. The strength of the core material is improved as well.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F28F 19/06 A

Claims (4)

[Claims] 1. By weight%, Si: 0.4 to 1.2%, Mg: 0.2 to 0.6% are contained, and further Cu: 0.01 to 0.4% and Mn: 0. Hf: 0.01 to 0.3%, Mo: 0.01 to 1% on one side of an Al alloy core material containing 1 to 1.2% of one or two kinds and the balance of Al and unavoidable impurities. 0.2
%, Nb: 0.01 to 0.2%, Ta: 0.01 to 0.2
%, Ti: 0.01 to 0.3%, V: 0.01 to 0.2
%, W: 0.01 to 0.1% of one or more kinds, and Zn: 0.01 to 3.0%, In: 0.01 to 0.05.
%, And a sacrificial anode layer made of an Al alloy containing Al and unavoidable impurities and the rest contains at least Si: 6.5 to 11.5%. Al-Si-Mg
Composite brazing sheet for heat exchanger made of aluminum alloy characterized by being coated with a brazing filler metal 2. By weight%, Si: 0.4 to 1.2%, Mg: 0.2 to 0.6% are contained, and further Cu: 0.01 to 0.4% and Mn: 0. Hf: 0.01 to 0.3%, Mo: 0.01 on both surfaces of an Al alloy core material containing 1 or 2 of 1 to 1.2% and the balance of Al and unavoidable impurities. ~ 0.2
%, Nb: 0.01 to 0.2%, Ta: 0.01 to 0.2
%, Ti: 0.01 to 0.3%, V: 0.01 to 0.2
%, W: 0.01 to 0.1% of one or more kinds, and Zn: 0.01 to 3.0%, In: 0.01 to 0.05.
%, And a sacrificial anode layer of an Al alloy containing Al and unavoidable impurities, the balance of which is at least Si: 6.5. Al-Si-Mg containing 11.5%
Composite brazing sheet for heat exchanger made of aluminum alloy characterized by being coated with a brazing filler metal 3. The core material component further comprises, by weight%, Hf: 0.01 to 0.3% and Mo: 0.01 to 0.2.
%, Nb: 0.01 to 0.2%, Ta: 0.01 to 0.2
%, Ti: 0.01 to 0.3%, V: 0.01 to 0.2
%, W: 0.01 to 0.1%, Zr: 0.01 to 0.2%
3. The composite brazing sheet for an aluminum alloy heat exchanger according to claim 1 or 2, containing one or more of 4. The aluminum alloy heat exchange according to claim 1, wherein the sacrificial anode layer component further contains Zr: 0.01 to 0.2% by weight. Composite brazing sheet