JP2756195B2 - Al-Mg-Si alloy brazing filler metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-Mg-Si alloy brazing material having excellent vacuum brazing properties suitable for manufacturing an aluminum heat exchanger having a hollow structure.

[0002]

2. Description of the Related Art In recent years, a vacuum brazing method that does not require a flux has been developed for brazing an aluminum structure, and has been actively performed from a place where there is no concern about pollution. Was. Vacuum brazing uses an aluminum alloy core material and a brazing sheet clad on one or both sides with an aluminum alloy brazing material as a cladding material, and performs brazing in a vacuum, brazing various structures including heat exchangers. It is used for Various types of aluminum alloys for core materials and aluminum alloy brazing materials for skin materials have been developed for vacuum brazing sheets, and are currently standardized by JIS Z 3263.

[0003] As a vacuum brazing sheet used in a heat exchanger, JIS A 3003, JIS A 3005, JI
Usually, SA 3105 and JIS A 6951 alloys are used, and as a skin material, JIS BA 4004 and AA 4104 alloy brazing materials having compositions shown in Table 1 are generally used. The brazing sheet has a thickness of 0.5 to 1.2 mm and a brazing material cladding ratio of 5 to 15% on one side, and is used as a brazing sheet of a single-sided or double-sided brazing material.

[0004]

[Table 1]

As a heat exchanger made of aluminum having a hollow structure using such a vacuum brazing sheet, a drone cup type evaporator, an oil cooler, a radiator and the like are manufactured. For example, in a drone cup type evaporator, as shown in FIG. 4, members (1) are laminated, and a corrugated fin (2) is placed between the laminated members (1).
And brazing by heating to 600 ° C. in a vacuum of the order of 10 ⁻⁵ to 10 ⁻⁴ Torr. In this vacuum brazing, brazing sheet brazing material (JISBA4004, AA 41
04 alloy etc.) begins to gradually evaporate from around 400 ° C, and the oxidizing gas in the furnace is changed from H ₂ O + Mg → M
gO + H ₂ , O ₂ + 2Mg → Removed by a getter reaction of 2MgO, and at the time of melting the brazing material,
Rapidly evaporates, causing a destructive effect of the oxide film on the surface of the brazing material, enabling brazing. Si also has the effect of lowering the melting point of the brazing material, lowering the brazing temperature and improving the brazing properties.

When a furnace is used for a long time, the degree of vacuum is reduced due to contamination of the furnace. In such a case, the wettability of the wax is reduced, and no fillet of the wax is formed.
Brazing property decreases. That is, a defective phenomenon called a brazing phenomenon occurs.

[0007]

According to the present invention, as a result of various studies to solve this problem, the brazing property and the brazing phenomenon were found to be caused by Mg ₂ Si particles in the metal structure of the brazing material clad on the brazing sheet. And the fact that the content of Fe is related to the formation of an oxide film on the surface of the brazing material during brazing and that this affects the brazing properties. Was. Based on these findings, the brazing material of the present invention has excellent A-vacuum brazing properties.
This is the development of a 1-Mg-Si alloy brazing material.

That is, one of the brazing materials of the present invention is 0.6 to 1.8 wt.
% Mg and 6.0 to 20.0 wt% Si, and
The content of Fe is defined below 0.3 wt%, a brazing material the balance being Al and inevitable impurities, circle Mg ₂ Si particles equivalent diameter 2~5μm is 1000 / mm ² or more in the metal structure And at least 3000 particles / mm ² of Si particles having a size of 6 μm or less.

Another one of the brazing materials of the present invention is 0.6 to 1.
8 wt% Mg, 6.0-20.0 wt% Si and 0.01-0.2
A brazing filler metal containing wt% Bi and a Fe content of 0.3 wt% or less, the balance being Al and unavoidable impurities.
₂ S particles of 1000 particles / mm ² or more and 6 μm or less
It is characterized in that i-particles are present at 3000 or more / mm ² or more.

[0010]

First, the chemical composition of the brazing alloy according to the present invention will be described. The brazing filler metal is 0.6-1.8 wt% Mg and
Contains 6.0 ~ 20.0wt% Si, Fe content is 0.3wt
% Or less, and the balance of A and inevitable impurities
An l-Mg-Si alloy is used.

[0011] Mg of the brazing material evaporates during brazing and has an effect of improving the degree of vacuum by a getter function and a function of destroying an oxide film by evaporation. Then the amount is 0.6wt%
If it is less than the above, the above effect does not sufficiently occur and the brazing property is reduced,
If the content exceeds 1.8 wt%, the Mg-based oxide film will increase during the heating for brazing, and the brazing property will decrease.

Si of the brazing material is an additive element that lowers the melting point of the alloy and enables brazing. So the amount added
If it is less than 6.0 wt% or more than 20.0 wt%, the melting point of the braze will increase and the brazeability will decrease. Fe in the brazing material promotes the growth of an oxide film during brazing heating. If the amount of Fe exceeds 0.3 wt%, the amount of film growth increases,
At the time of evaporation of Mg, the film is not sufficiently broken, and the brazing property is reduced.

The above is the composition of the brazing alloy according to the first invention, but the second invention is based on the case where Bi is further added in an amount of 0.01 to 0.2 wt%. In this case, Bi has the function of improving the fluidity of the brazing material, promoting the evaporation of Mg, and facilitating the breakage of the film. If the amount of Bi is less than 0.01% by weight, the above effect is not sufficient. If the amount exceeds 0.2% by weight, the rollability of the brazing material is reduced, and it is difficult to produce a brazing sheet.

Next, a method for measuring the particle size will be described.
Particles present inside the brazing material were observed by a reflected electron image using a scanning electron microscope. In the observed backscattered electron image, those which appear black are Mg ₂ Si particles, and those which appear white are S
The particles were determined to be i-particles, and image analysis was performed to determine the circle-equivalent diameter.

As described above, in the present invention, the number of Mg ₂ Si particles in the metal structure is set to be 1000 / mm ² or more in the range of the circle-equivalent diameter of 2 to 5 μm when the particle diameter exceeds 5 μm. At the initial stage of vacuum brazing heating, the amount of evaporation of Mg is reduced, the function as a getter is reduced, and the expected effect cannot be obtained. On the other hand, if the particle size is smaller than 2 μm, Mg
When evaporating, the destructive power of the oxide film on the brazing filler metal surface is reduced. Therefore, in the present invention, Mg ₂ Si having a particle size of _{2 to} 5 μm is used.
Must have enough particles. That is, if the number of Mg ₂ Si particles is less than 1000 / mm ² with a particle size within the above range, the ability to break down the oxide film on the brazing filler metal surface due to the evaporation of Mg is reduced, and the function as a getter is impaired. Will be enough. Therefore, the number of Mg ₂ Si particles having a particle size of 2 to 5 μm should be limited to 1000 particles / mm ² or more. Note that Mg ₂
The upper limit of the number of Si particles is preferably as large as possible.
The limit is 00 pieces / mm ² or less.

Further, in the present invention, the reason why the number of Si particles present in the brazing material is 3,000 particles / mm ² or more with a circle equivalent diameter of 6 μm or less is that, in the case of Si particles having a particle diameter of more than 6 μm, the melting point of the solder is As a result of requiring a long time, the brazing time must be increased or the brazing temperature must be increased. Therefore, in the present invention, the Si particles must be 6 μm or less. If the number of Si particles having a size in this range is less than 3000 particles / mm ² , the desired effect cannot be obtained in the above operation. Therefore, by limiting the number of Si particles having a particle size of 6 μm or less to 3000 particles / mm ² or more,
Brazing properties are improved.

In the present invention, the number of Mg ₂ Si particles having a particle size of 2 to 5 μm existing in the metal structure inside the brazing filler metal is 1000
By limiting the number of particles / mm ² or more, the destruction of the oxide film on the surface of the brazing material by the vapor of Mg is sufficiently promoted, and the function of improving the discharge of the oxidizing gas as a getter is achieved. The number of Si particles of 6 μm or less is 3000
By limiting the number to pieces / mm ² or more, the brazing time is shortened, and the brazing temperature is lowered to improve the brazing property.

The number of Mg ₂ Si particles having a particle size of 2 to 5 μm and the number of Si particles having a particle size of 6 μm or less in the metal structure of the conventional brazing material were measured in the same manner as described above. As a result, the number of Mg ₂ Si particles was 946 / mm ² , and the number of Si particles was 10528 / mm ² .

In the present invention, the predetermined distribution of Mg ₂ Si particles and the distribution of Si particles can be obtained by controlling the conditions of casting, soaking, hot rolling, and intermediate annealing of the brazing filler metal.

[0020]

Next, the present invention will be described in more detail with reference to examples. As the core material and the brazing material, the brazing materials A and B having the composition according to the present invention as shown in Table 2 and the brazing materials C and D having the conventional composition were used.
Brazing sheets No. 1 to No. 12 shown in Table 3 (with a cladding ratio of 15%) were produced.

At this time, the conventional brazing sheet No. 12
First, after casting a brazing material (skin material), the brazing material is subjected to soaking at 485 ° C. for 3 hours, and the Al alloy core material and the skin material are heated together (485 ° C. × 3 hours) and then heated. Cold-rolling, intermediate annealing (360 ° C. × 2 hours), and further cold rolling were performed to a sheet thickness of 0.6 mm, followed by finish annealing at 360 ° C. × 2 hours to produce an annealed material having a thickness of 0.6 mm.

Other brazing sheets No. 1 to No.
No. 11 was manufactured by changing the conditions of the Mg ₂ Si particles and the Si particles in the brazing material by changing the conditions of the soaking treatment of the brazing material, the conditions of the combined heating, the conditions of the hot rolling and the annealing conditions. That is, these brazing sheets No. 1 to N
In o.11, first, a brazing material (skin material) is cast and this brazing material is
After soaking at 0 ° C or more for 3 hours, the aluminum alloy core material and the skin material are heated together at 520 ° C or more for 3 hours, then hot-rolled and cold-rolled to a sheet thickness of 0.6 mm, and then 330 Finish annealing was performed at 2 ° C. × 2 hours to produce an annealed material having a thickness of 0.6 mm.

Next, the brazing sheet is press-formed to form a cup shown in FIG. 1 (plan view) and FIG. 2 (cross-sectional view).
(3) was produced. (4) in the figure is an exhaust port. The test hollow structure (5) shown in FIG. 3 was prepared by vacuum brazing and the cups formed by press-forming the brazing sheet in this manner were stacked and tested. In the figure, (3) is a cup with an exhaust port, (6) is a cup without an exhaust port, and (7) is an exhaust pipe.

The brazing test condition is 5 × 10 ^-5 To
10 min after reaching 600 ° C at a rate of 30 ° C / min in a vacuum of rr
Held. The evaluation was performed according to the degree of fillet formation after brazing on the mating surface of the cup, and the rate of occurrence of brazing was determined for 100 tests. The results are shown in Table 3.

[0025]

[Table 2]

[0026]

[Table 3]

From Table 3, it can be seen that the examples of the present invention have significantly improved fillet forming ability as compared with the results of the conventional example and the comparative example.
It can be seen that the brazing properties are stable.

[0028]

As described above, according to the present invention, Al-Mg-
The brazing property of the Si-based alloy brazing material can be improved, thereby making it possible to remarkably reduce the rejection rate and to achieve a remarkable industrial effect such as stable operation.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a heat exchanger cup.

FIG. 2 is a sectional view of the same.

FIG. 3 is a side sectional view showing a test hollow structure in which cups are stacked.

FIG. 4 is a perspective view showing an example of a drone cup type evaporator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Component 2 Corrugated fin 3 Cup 4 Exhaust port 5 Test hollow structure 6 Cup without exhaust port 7 Exhaust cylinder

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-264188 (JP, A) JP-A-4-220194 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 35/28

Claims (2)

(57) [Claims] (1) 0.6 to 1.8 wt% of Mg and 6.0 to 20.0 wt.
A brazing filler metal containing wt% Si and a Fe content of 0.3 wt% or less, the balance being Al and unavoidable impurities.
₂ S particles of 1000 particles / mm ² or more and 6 μm or less
A wherein at least 3,000 i-particles / mm ² are present
l-Mg-Si alloy brazing material. 2. Mg of 0.6-1.8 wt%, 6.0-20.0 wt%
Of Si and 0.01 to 0.2 wt% Bi, and
The content of the e defined below 0.3 wt%, a brazing material the balance being Al and inevitable impurities, circle Mg ₂ Si particles equivalent diameter 2~5μm is 1000 / mm ² or more in the metal structure An Al-Mg-Si alloy brazing material characterized in that there are 3000 particles / mm ² or more of Si particles having a size of 6 µm or less.