JPH06285669A - Al alloy brazing sheet for executing low vacuum brazing excellent in brazing quality - Google Patents

Abstract

PURPOSE:To execute excellent brazing of an Al alloy brazing sheet in the low vacuum condition. CONSTITUTION:The brazing filler metal containing 0.2-0.8% Mg and 5-15% Si as the basic components is cladded on one side or both sides of an Al alloy core where 0.2-1.2% Mg is contained as the basic component, and the content of Si and Cu in the inevitable impurities are regulated to <=0.1% and 0.05% respectively. When requested, Mn, Zr, Cr, Ti, V and Fe of the prescribed amount are added as the components of the core, and Bi and Be of the prescribed amount are added as the components of the brazing filler metal. In addition, the peripheral length of the crystalline grain of the core after brazing and heating is regulated to 400-600mum. This constitution allows the excellent brazing under the low vacuum condition, and the reduction in the strength by the pollution in the surface due to the presence of Mg and Mg transpiration can be previously prevented. Moreover, the brazing quality can be further improved by regulating the peripheral length of the crystalline grain of the core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a tube material or a reinforcing material in heat exchangers for automobiles such as radiators and evaporators, for low vacuum brazing which is brazed at a low vacuum of 10 ^-2 torr or more. The present invention relates to an Al alloy brazing sheet.

[0002]

2. Description of the Related Art Most of tube materials and reinforcing materials used in heat exchangers for automobiles such as radiators and evaporators are
It is composed of an aluminum alloy material. Generally, a brazing sheet in which a brazing material is clad in this alloy material
Heat exchangers are manufactured by vacuum brazing under a vacuum of 0 ^-4 to 10 ^-5 torr. In this vacuum brazing, a brazing sheet containing 1 to 2% of Mg in the brazing material is used, and Mg in the brazing material is vigorously evaporated near the melting point of the brazing material to destroy the oxide film of the brazing material. By improving the wetting of the brazing material, and further by the getter action, the oxidizing gas in the atmosphere is trapped to prevent reoxidation of the surface, thus enabling brazing.

However, since the Mg evaporated in the atmosphere pollutes the inside of the vacuum heating furnace and finally deposits a large amount on the wall surface of the vacuum furnace, it is necessary to clean the vacuum furnace regularly, which lowers the work efficiency. There is a problem to let. Further, in the brazing sheet in which Mg is contained in the core material to improve the strength,
There is a problem that Mg of the core material evaporates during brazing and the strength of the material decreases. In contrast, the brazing material which was a small amount of Mg content (e.g., JIS BA4005) and core material of Mg non-containing (e.g., JIS A3003) brazing sheet obtained by cladding a high vacuum (10 ^-5 to 10 ^{- 7}
A method of brazing with a torr) is known.

However, brazing in a high vacuum causes an increase in manufacturing cost, and is not suitable for mass production of industrial products such as heat exchangers for automobiles. From this point of view, brazing sheets that have been brazed under a medium vacuum (10 ⁻⁴ to 10 ⁻⁵ torr) have been brazed in a vacuum having a relatively low vacuum of 10 ⁻² torr or more. Has proposed a so-called low-vacuum brazing method for suppressing the evaporation of Mg in the brazing material.

[0005]

In the above low-vacuum method, the destruction of the oxide film is reduced due to the decrease in the amount of evaporated Mg, so that the Mg content is lower than that of the brazing filler metal used in the conventional medium-vacuum method. It is common knowledge that the Mg content of the brazing filler metal should be increased a little while considering the influence on the transpiration amount. But,
In the conventional medium-vacuum method, Mg, which was actively evaporated from the early stage of the brazing heat, is evaporated only slowly in the low-vacuum brazing method described above. Therefore, Mg contained in the brazing filler metal is retained in the brazing heat. As a result, MgO is generated, and an Al oxide film containing MgO is thickly formed on the surface of the brazing material.

Therefore, in the case of Mg that evaporates gradually,
It is difficult to sufficiently destroy a strong oxide film in combination with a decrease in the amount of transpiration, and there is a problem that good brazing properties cannot be obtained. In addition, there is a problem that since the amount of Mg remaining after brazing is high, the fluidity of the brazing becomes too high and a good fillet cannot be formed. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a brazing sheet capable of solving the problems caused by the evaporation of Mg without impairing the brazing property.

[0007]

In order to solve the above problems, the inventors of the present invention have conducted extensive studies and as a result, by combining a brazing material having a low Mg content and a core material containing an appropriate amount of Mg, Overturning common sense, we found that brazing can be performed well even in a low vacuum. As a result of further research, they found that the brazing property was further improved by controlling the contents of Si and Cu, which are impurities in the core material, and the present invention was accomplished. That is, the Al alloy brazing sheet for low vacuum brazing having excellent brazing property of the present invention contains Mg: 0.2 to 1.2% by weight, and the balance is Al and inevitable impurities, In the unavoidable impurities, the Si content is 0.1% or less, and the Cu content is regulated to 0.05%. %, Si: 5 to 1
It is characterized in that it comprises a brazing material containing 5% and the balance being Al and unavoidable impurities.

In a second aspect of the present invention, in addition to Mg as a core material component in the first aspect, Mn: 0.1% by weight is further added.
.About.1.5%, Zr: 0.05 to 0.25%, Cr: 0.
05-0.25%, Ti: 0.05-0.25%, V:
It is characterized by containing one or more of 0.05 to 0.25% and Fe: 0.2 to 1.2%. 3rd invention is a 1st or 2nd invention, and also as a brazing filler metal component, by weight%, Bi: 0.01-0.2%, B
e: It is characterized by containing 0.0001 to 0.005% of 1 type or 2 types. A fourth invention is characterized in that, in the first to third inventions, the peripheral length of the crystal grains of the core material after the brazing heat is 400 to 600 μm.

The brazing sheet of the present invention is
The brazing material is clad on one side or both sides of the core material, but when clad on both sides, the brazing material does not have to be the same material, and any one of the brazing materials shown in the present invention is combined and clad. Things are naturally included. When the brazing material is clad on one surface of the core material, it is possible to clad another material, for example, a sacrificial anode skin material on the other surface. The clad ratio of the brazing material and the sacrificial anode skin material is not particularly limited, but is preferably 5 to 15%. Further, in the case of controlling the peripheral length of the crystal grains of the core material, it is desirable that all the crystal grains are included in the range, but it is not limited to this, and most of the crystal grains are It may be included in the range.

[0010]

In other words, according to the present invention, since the brazing material in the brazing sheet has a relatively small amount of Mg, the amount of MgO generated during the brazing heat is small, and the surface of the brazing material contains MgO. The contained oxide film is not thickly formed. Further, it is well known that when the brazing material has a low Mg content, the effect of destroying the oxide film on the surface of the brazing material cannot be sufficiently obtained by vacuum brazing, and good brazing cannot be performed. In the invention, the lack of Mg on the brazing filler metal side is compensated by the diffusion of Mg from the core material side.

By the way, the Al alloy inevitably contains impurities due to reasons such as the manufacturing process and selection of raw materials. Among them, Si contained in a few percent of commas and 1 or 2% in commas. The generated Cu reacts with the component element Mg to form a compound. Since these compounds improve the strength, they have not been particularly problematic in the past. However, in the operation intended by the present invention, if Mg in the core material is trapped as a compound, the amount of diffusion of Mg to the brazing material side is reduced, so that the oxide film cannot be sufficiently destroyed. The phenomenon that the brazing property is deteriorated occurs. Therefore, in the present invention, the content of impurities Si and Cu in the core material is regulated to a predetermined amount or less to smooth the diffusion of Mg and prevent the deterioration of brazing property.

That is, in the brazing sheet of the present invention, as the heat treatment progresses, Mg in the core material diffuses and penetrates into the brazing material, and this Mg evaporates in the high temperature vacuum atmosphere, so that the oxide film on the surface of the brazing material is securely formed. Can be destroyed. Further, when the amount of Mg in the brazing filler metal decreases due to evaporation of Mg, Mg is continuously supplied from the core side, so that the brazing filler metal contains an appropriate amount of Mg corresponding to the amount of evaporation, and the brazing ends. Afterwards, a large amount of Mg in the brazing material
Does not remain.

Further, as described above, in the diffusion and evaporation of Mg, there is a correlation between the Mg content of the core material and the Mg content of the brazing material. In addition, brazing material Mg content −0.3% ≦ core material Mg
It is desirable to satisfy the relationship of content ≤ brazing material Mg content + 0.3%. Further, the brazing material Mg content −0.2% ≦
It is more desirable to satisfy the relationship of Mg content of core material ≦ Mg content of brazing material + 0.2%.

Next, the reasons for limiting the components and the like in the present invention will be described. (Core material) Mg: 0.2 to 1.2% Mg of the core material diffuses into the brazing material during brazing and replenishes Mg of the brazing material lost by evaporation. If the Mg content is less than 0.2%, the above effect is insufficient and 1.2%
If it exceeds 1.0, a large amount of diffusive invasion into the brazing filler metal side occurs at the initial stage of heating to increase the production of MgO, which lowers the brazing property and the corrosion resistance of the core material. Si: 0.1% or less, Cu: 0.05% or less Si and Cu in the impurities form a compound with the component element Mg to inhibit the diffusion of Mg from the core material to the brazing material, and therefore are contained as much as possible. A small amount is desirable. But,
Due to manufacturing restrictions, the upper limit was set as above.

Mn: 0.1 to 1.5% Zr: 0.
05-0.25% Cr: 0.05-0.25% Ti: 0.05-0.2
5% V: 0.05 to 0.25% Fe: 0.2 to 1.2% Since these elements are dispersed in the core material as precipitates to improve the strength, they are selectively contained. If it is less than the respective lower limits, the above-mentioned action is insufficient, and if it exceeds the upper limit, the workability is deteriorated.

(Brazing material) Mg: 0.2 to 0.8% Mg destroys the oxide film on the surface of the brazing material and traps the oxidizing gas in the atmosphere to prevent surface oxidation.
If the Mg content is less than 0.2%, this effect is insufficient, and if it exceeds 0.8%, the fluidity of the brazing filler becomes too high, the fillet is not formed well, and brazing failure occurs. The above range was set.

Si: 5 to 15% Si lowers the melting point of the wax and improves the fluidity. If the content is less than 5%, the fluidity of the wax is insufficient. On the other hand, if it exceeds 15%, the fluidity of the wax is rather reduced due to the formation of coarse Si crystallized products. Bi: 0.01 to 0.2%, Be: 0.0001 to 0.
005% Bi and Be are selectively contained in order to improve the fluidity and filling property of the brazing material and improve the brazing property. If the content of these components is less than the lower limit, the above-mentioned action is insufficient, if Bi exceeds the upper limit, erosion occurs, and if Be exceeds the upper limit, no further effect can be expected.

(Crystal grain length of the core material) 400 to 600 μm The grain boundaries of the crystal are aligned with the inside of the grain, and Mg from the core material to the brazing material is formed.
It becomes a diffusion route. Particularly, in the region where the temperature is low, grain boundary diffusion is the main. In normal manufacturing, the perimeter is 1000 to 3
The crystal grain size is about 000 μm, and especially when the grain size is reduced, the crystal grain size is about several tens μm. By controlling this, diffusion of Mg is promoted. However, if the crystal grain size is less than 400 μm, the number of grain boundaries decreases, and
The diffusion route decreases, while when it exceeds 600 μm,
When the brazing material melts, the brazing material is likely to erode into the core material, causing local melting.

[0019]

EXAMPLE A brazing material shown in Table 2 was clad on both surfaces of a core material having a composition shown in Table 1 to a thickness of 10% to form a rectangular plate-shaped brazing sheet having a plate thickness of 0.5 mm and a size of 50 mm × 25 mm. . However, the brazing sheet No. For 4,
The brazing material is clad only on one side, and JIS A on the other side.
A sacrificial anode skin material having a composition of 1050 was clad. In addition, as a comparative material, the test material No. e (J
(Equivalent to IS A3003), the test material f, and the brazing material are the test material No. An Al alloy of E (corresponding to JIS BA4004) was prepared. In the test material f, Mg and Fe are within the scope of the invention, but the contents of Si and Cu are not regulated.

Each of these brazing sheets is
The brazing sheet and the alloy plate were assembled vertically in an inverted T shape on a JIS A3003 Al alloy plate having a plate thickness of 2 mm. These assembled bodies are put in a vacuum heating furnace, and N
Brazing was performed by using ₂ carrier gases under a vacuum of 3 × 10 ^-1 torr and holding at a predetermined temperature for 10 minutes.
In order to evaluate the brazing property of the obtained brazed product, the thickness of the fillet formed between the brazing sheet and the Al alloy plate was measured. Furthermore, the brazing sheet after brazing was subjected to a tensile test to investigate the influence of brazing on the strength. The results of these tests are shown in Table 3.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

As is apparent from Table 3, the brazed product using the brazing sheet of the present invention is excellent in brazing property and corrosion resistance. On the other hand, brazing sheet No. prepared as a comparative example. No. 5 had a very small fillet throat, and it was difficult to braze it well. Also, Table 3
Although not shown in FIG. 5
Was brazed under a vacuum of 10 ^-5 torr as in the conventional case, and the contamination in the vacuum furnace was remarkable. In addition, the brazing sheet No. of the comparative example. No. 6 was inferior in brazing property due to the influence of Si and Cu.

Further, the brazing sheet No. For No. 3, the crystal grain size was adjusted by controlling the homogenization treatment conditions, tempering, and brazing heat, and 3 × 1
Brazing was performed under a vacuum of 0 ^-1 torr. The peripheral length of the crystal grain size of the core part of the obtained brazed product was measured, and the throat thickness of the fillet between the brazing sheet and the Al alloy was measured in the same manner as in the above example, and the results are shown in Table 4.
It was shown to. The peripheral length of the crystal grain size is shown as an average value. As is clear from Table 4, the brazed product in which the crystal grain size of the core material is within the range of the present invention ensures good brazing property. On the other hand, it has been found that in the case of a brazed product outside the scope of the invention, if the particle size is too small, fillets are not sufficiently formed. When the particle size was too large, local melting was observed in the core material.

[0026]

[Table 4]

[0027]

As described above, according to the brazing sheet of the present invention, the basic component is Mg: 0.2 to
It contains 1.2%, and the Si content in the unavoidable impurities is 0.
1% or less, on one or both sides of the Al alloy core material in which the Cu content is regulated to 0.05%, Mg: 0.
Since a brazing material containing 2 to 0.8% and Si: 5 to 15% is clad, it is possible to braze an Al alloy in a low vacuum without impairing the brazing property. It is possible to prevent contamination and strength reduction due to Mg evaporation. Furthermore, if the peripheral length of the crystal grains of the core material after the brazing heat is regulated to 400 to 600 μm, the diffusion of Mg in the core material is smoothed, and the brazing property is further improved.

Claims (4)

[Claims] 1. An Mg content of 0.2 to 1.2% by weight, the balance consisting of Al and unavoidable impurities, wherein the unavoidable impurities have a Si content of 0.1% or less and a Cu content. %: Mg: 0.2-0.8%, Si: 5-1 on one side or both sides of the Al alloy core material whose amount is regulated to 0.05%.
An Al alloy brazing sheet for low vacuum brazing, which is excellent in brazability and is characterized by comprising a brazing material containing 5% and the balance being Al and inevitable impurities. 2. As a core material component, M in% by weight is further included.
n: 0.1 to 1.5%, Zr: 0.05 to 0.25%,
Cr: 0.05 to 0.25%, Ti: 0.05 to 0.2
5%, V: 0.05 to 0.25%, Fe: 0.2 to 1.
2. Low vacuum brazing A with excellent brazing properties according to claim 1, characterized in that it contains one or more of 2%.
l alloy brazing sheet 3. A brazing filler metal component further comprising B in a weight percentage.
i: 0.01 to 0.2%, Be: 0.0001 to 0.0
The Al alloy brazing sheet for low-vacuum brazing having excellent brazing property according to claim 1 or 2, characterized in that the brazing sheet contains 05% of 1 type or 2 types. 4. The low-vacuum brazing material having excellent brazing property according to claim 1, wherein the peripheral length of the crystal grains of the core material after the brazing heat is 400 to 600 μm. Al alloy brazing sheet for attachment