JP2003126986A - Aluminum alloy brazing sheet, brazing method using it, and brazed product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum brazing sheet requiring no costly facility such as a vacuum furnace or an airtight atmospheric furnace, free from wastage of flux or inert gases to achieve lower cost, and enabling a brazing of better work simplification to obtain a highly-corrosion resistant brazed product. SOLUTION: The brazing sheet is structured as an intermediate material between a thin cover material and a core material, wherein a brazing filler metal containing Al-Si base alloy or additional Mg, Bi and/or Zn, Sn, is used for brazing without flux in an inert gas atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum brazing sheet capable of flux-free joining in an inert gas atmosphere, a brazing method using the same, and a product brazed therewith. is there.

[0002]

BACKGROUND OF THE INVENTION Aluminum brazing is used in the production of heat exchangers and panels as an efficient method for producing large area joints and multipoint joints all at once. Further, in this multi-point joint, a brazing sheet is generally used in which a brazing material is clad as a skin material to a core material which is a structural material in view of the efficiency of disposing the brazing material in the joint. As the brazing method, three methods are used: a flux-free method in vacuum, a non-corrosive flux method in an inert gas atmosphere, and a corrosive flux method in the atmosphere. However, among these brazing methods, an expensive vacuum furnace is required, which is cheaper than the vacuum type but still requires an expensive atmosphere-tight atmosphere furnace, a flux coating step, and an expensive inert gas that is consumed, Is excellent in terms of equipment and consumption, but has problems such as a great deal of labor and cost required for treating corrosive flux before and after brazing. For these problems,
For example, as shown in Welding Journal, October 1983, P31-, Al-Si-Mg.
-A method of flux-free brazing in a nitrogen gas atmosphere using a brazing sheet of Bi brazing material has been proposed.

However, these methods have problems that the oxide film on the base plate must be controlled to be thin and that the flow rate of nitrogen gas must be increased to prevent oxidation.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and makes it possible to perform a simple flux-free aluminum alloy brazing in an inert gas atmosphere.
The purpose is to provide a jing sheet.

[0005]

The skeleton of the present invention uses an blazing sheet having a structure in which an Al-Si brazing material is sandwiched as an intermediate material between a thin skin material and a core material in an inert gas atmosphere. In the case of flux-free brazing, the brazing is performed by exuding the molten brazing material on the surface of the skin material when the brazing material is melted.

Specifically, the invention of claim 1 uses an Al—Si alloy brazing material as an intermediate material between the thin skin material and the core material,
An aluminum alloy brazing sheet for brazing without flux in an inert gas atmosphere, characterized in that an aluminum alloy having a solidus temperature higher than the liquidus temperature of the brazing material is used for the thin skin material and the core material. Is.

[0007] The invention of claim 2 is the Al-Si of claim 1.
The system alloy brazing material is characterized by further containing one or two of Mg 0.1 to 5% (same as mass% or less) and Bi 0.01 to 0.5%.

According to a third aspect of the invention, in the first or second aspect, the Al—Si alloy brazing material further comprises ZnO.
1-5%, In0.01-0.1%, Sn0.01-
It is characterized by containing 0.1% of one kind or two or more kinds.

A fourth aspect of the present invention is a brazing method characterized in that the aluminum alloy brazing sheet according to the first to third aspects is brazed without flux in an inert gas atmosphere. The invention of claim 5 is claim 4
It is a brazed product brazed by the method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Here, an Al—Si alloy brazing material is used as an intermediate material between the thin skin material and the core material. Si is an essential alloying element for an aluminum alloy brazing material, and has the function of lowering the melting point of the brazing material and improving the fluidity of the molten brazing material. The amount added is 5.0% to 15.0%.
If it is less than 5.0%, the melting point is not lowered so much that the fluidity of the molten wax is poor. If it exceeds 15.0%, primary crystals of Si are generated, the amount of molten brazing accumulated on the fillet portion is reduced, and the amount of molten corrosion of the core material is increased. It should be noted that Fe, which is an unavoidable impurity generally contained in aluminum, is contained up to about 0.5% or less because it does not adversely affect the characteristics of the brazing material. In the invention of claim 2, the above Al-Si
0.1 to 5% Mg, Bi0.01
~ 0.5% of one or two. Mg promotes the wettability and spreadability of wax in an inert gas atmosphere. Especially, when the oxygen concentration in the inert gas atmosphere is high, this effect by the addition of Mg is effective. Addition amount is 0.1%
~ 5%. If it is less than 0.1%, there is no promoting effect on the wetting and spreading properties of the wax, and if it exceeds 5%, the promoting effect is saturated and it is not economical. Further, in vacuum brazing, most of Mg in the brazing material evaporates and does not contribute to the improvement of strength after brazing, but since the amount of remaining Mg is relatively large in brazing in an inert gas atmosphere, It also contributes to the improvement of strength after brazing. Bi coexists with Mg or alone, and promotes the wettability and spreadability of brazing in an inert gas atmosphere. The addition amount is 0.01 to 0.5%.
If it is less than 0.01%, there is no promoting effect on the wetting and spreading properties of the wax, and if it exceeds 0.5%, the promoting effect is saturated and it is not economical. In the invention of claim 3, the brazing material further contains Zn.
0.1-5%, In0.01-0.1%, Sn0.01
.About.0.1% of one type or two or more types are contained. These elements give the brazing material a sacrificial anticorrosive action and improve the corrosion resistance of the core material. The addition amount of Zn is 0.1 to 5%, I
In the case of n and Sn, it is 0.01 to 0.1%. Below each lower limit, the sacrificial anticorrosive action is insufficient, and above the upper limit, the sacrificial anticorrosive action is saturated, which is not economical.

As the aluminum alloy used for the thin skin material and the core material, an aluminum alloy having a solidus temperature higher than the liquidus temperature of the brazing material is used. The aluminum alloy to be used may have any composition as long as this condition is satisfied. Considering necessary product strength and corrosion resistance, etc., JIS A 107
0,1050,1100,1200,3003,320
3, 3004, 5005, 5N01, 6951, 606
The alloy can be selected from standard alloys such as 1,6063, 6N01, etc., or alloys obtained by adding various alloying elements thereto. Note that in brazing using flux, the amount of Mg in the joining partner material (base material) or core material is strictly regulated because a reaction with the flux occurs, but since the present invention does not use flux, the joining partner material (base material) Material) or the amount of Mg in the core material is not strictly regulated, and as a result, an alloy having high strength after brazing can be used. Further, if Mg is contained in the thin skin material, an oxide film on the surface of the thin skin material tends to grow during the temperature rising process of brazing, and therefore it is preferable that the thin skin material does not contain Mg.

The thickness of the blazing sheet as a whole is usually in the range of 0.05 to 2.0 mm. If the plate thickness is less than 0.05 mm, it will be difficult to manufacture, or the brazing material will be insufficient and the brazing property will deteriorate. Further, if it exceeds 2.0 mm, the thickness is unnecessarily and it is not economical. 0.05-0.2m
The plate thickness of m is used as a fin material, and is 1.0 to 1.6.
A plate thickness of mm is used for a tank material of a radiator or the like, and an intermediate plate thickness is used for a plate material of an evaporator or the like.

The thin skin material clad ratio (thickness ratio of one thin skin material layer to the total plate thickness) is 0.1 to 10%, and the intermediate brazing material clad ratio (thickness ratio of one intermediate brazing material layer to the whole plate thickness) is 5
-20%. The reason is as follows. If the thin skin clad ratio is less than 0.1%, it is difficult to control and control the thickness, and the skin material may peel off during rolling.
If it exceeds%, leaching becomes difficult when the wax is melted. If the intermediate brazing material clad ratio is less than 5%, the brazing ability is deteriorated due to insufficient brazing material, and if it exceeds 20%, the brazing material becomes excessive and melt erosion of the core material occurs, which is not preferable.

Typical examples of the arrangement of these thin skin material, intermediate brazing material and core material are shown in FIGS. 1 (a) (b) (c). The thin skin material and the intermediate brazing material may be arranged on both surfaces of the core material or on only one surface side. At this time, the thin skin material and the intermediate brazing material may be arranged as a set. In the case of double-sided brazing filler metal clad, there are 5 layers including the core material [Fig. 1 (a)], and in the case of single-sided brazing filler metal clad, there are 3 layers including the core material [Fig. 1 (b)]. Furthermore, a sacrificial anode layer or the like may be provided on the other surface of the core material with the brazing filler metal on one surface to improve the corrosion resistance. In this case, a four-layer [FIG. 1 (c)] structure is obtained.

The oxygen concentration in the inert gas atmosphere is 100.
It should be 0 ppm or less. Further, the lower the oxygen concentration is, the more preferable for brazing property, but a large amount of inert gas is required to reduce the oxygen concentration to 30 ppm or less, resulting in an increase in cost. As described above, when the Al-Si alloy brazing material further contains one or two of Mg 0.1 to 5% and Bi 0.01 to 0.5%, brazing up to an oxygen concentration of about 1000 ppm is possible. Possible, but Mg 0.1-5%, Bi
When 0.01 to 0.5% of 1 type or 2 types is not contained, brazing can be performed only up to an oxygen concentration of about 500 ppm. Further, nitrogen is usually preferable as the inert gas from the viewpoint of cost, but a rare gas such as Ar may be used. The brazing heating temperature of the aluminum plate should be a temperature at which the brazing material melts and the thin skin material does not melt alone, that is, a temperature higher than the liquidus temperature of the brazing material and lower than the solidus temperature of the thin skin material. Adopt a brazing temperature of ~ 620 ° C.

The reason why fluxless brazing can be performed in an inert atmosphere by the brazing method of the present invention is presumed to be as follows.

That is, in general, in order to enable brazing of aluminum, it is essential to cause the wetting of the molten brazing material. To satisfy this condition, the brazing material and the joining partner material during the brazing heating. It is necessary to have an antioxidant action and an oxide film destruction action for the (base material). In this case, the sensitivity of both of these actions is particularly high in the brazing material, and it is considered that the control of the brazing material needs to be more strict with respect to the joining partner material (base material). Therefore, in the current brazing method, as described above, in order to prevent the oxidation and the destruction of the oxide film, the Mg evaporation phenomenon is utilized at the same time as the heating in the vacuum (vacuum brazing), or in the non-oxidizing atmosphere. Utilization of flux (a non-corrosive flux brazing method in a non-oxidizing atmosphere) is performed.

On the other hand, in the present invention, the brazing material in the intermediate layer melts as the temperature rises during brazing, but the surface of the brazing material is covered with a thin skin material that remains solid, so the surface of the brazing material is not oxidized. It won't happen. When the temperature further rises, a portion having a low melting point such as a segregated portion of the thin skin material which is in contact with the molten brazing material is locally melted, and when the thin skin material is penetrated, the brazing material seeps into the surface due to volume expansion and spreads. At this time, the surface of the brazing material becomes a new surface without an oxide film, and since it is an inert gas atmosphere, new strong oxidation does not proceed. Flux used in conventional brazing in air or in an inert gas atmosphere and Mg for vacuum brazing are originally generated on the plate surface, or the thick oxide film generated during brazing is destroyed to melt the brazing filler metal. In the present invention, since the thick oxide film does not exist, the molten brazing material spreads even without flux or Mg. When the temperature further rises, the melting further progresses, and many parts of the thin skin material melt and the number of places where the brazing material seeps out increases. The molten brazing filler metal that has leached spreads over the upper surface of the oxide film on the surface of the thin skin material one after another, and the thin skin material below the oxide film is largely eroded by the molten brazing material, causing the plate thickness to decrease in a large amount. To melt. Due to both of these (the molten brazing filler metal that has spread on the upper surface of the oxide film on the surface of the thin skin material and the progress of melting of the thin skin material from under the oxide film on the surface of the thin skin material), the oxide film originally present on the surface of the thin skin material Are separated, and the molten brazing filler metal and the melted thin skin material are dispersed in a single body, and the adverse effect as an oxide film disappears. This mechanism is schematically shown in FIG.

If an appropriate amount of Mg or Bi is present in the brazing material, in addition to the above action, oxygen in the nearby atmosphere is further consumed and the surface of the molten brazing material or thin skin material is prevented from being oxidized. The oxygen concentration in the atmosphere is increased to some extent to promote the wetting and spreading of the brazing wax and maintain good brazing properties.

[0020]

Example A book mold ingot of the alloy for core material (No. A) shown in Table 1 was subjected to both-side surface grinding to a thickness of 40 mm, and then 60
A homogenizing treatment was performed at 0 ° C. for 10 hours to prepare a core material. Also, alloys for thin skin materials (No. B) and alloys for intermediate brazing materials (N
o. (C to M) book mold ingots are both surface-milled to a thickness of 40 mm, and then hot-rolled and cold-rolled in order to obtain a thickness of 1.9 mm (cladding ratio 3%) and 9.4 mm, respectively.
A thin skin material and an intermediate brazing material having a clad ratio of 15% were prepared. Next, the thin skin material, the intermediate brazing material, and the core material are laminated in the combination shown in Table 2, and this is hot rolled at a starting temperature of 500 ° C. to form a clad material having a thickness of 4 mm, which is cold rolled to 0.5 mm. Then, it was annealed at 400 ° C. for 2 hours to obtain a tempered O material. The thus prepared 5-layer or 3-layer brazing sheet (0.5 mm thickness x 30 mm x 60 m)
m) was combined with a JIS A 3003 joining partner material (base material) plate (1.0 mm thickness × 30 mm × 60 mm) to assemble a T-joint test piece as shown in FIG.

[0021]

[Table 1]

[0022]

[Table 2]

This test piece was placed in a nitrogen atmosphere brazing furnace (temperature 600 ° C.) having various oxygen concentrations shown in Table 3, held for 5 minutes after reaching the maximum temperature, and taken out from the furnace. As a comparison, a test piece was prepared in the same manner as above except that two kinds of ordinary double-sided clad brazing sheets were used on the surface of the brazing material without using the skin material of the present invention. It was brazed without application.

The result of the brazing property is the fillet formation rate,
That is, the ratio of fillet formation length to braze joint length (100% is full length fillet formation) was evaluated and shown in Table 3.

[0025]

[Table 3] From the results of Table 3, Comparative Examples 12 and 13 having no surface skin material have a low fillet formation rate, and particularly, Comparative Example 12 in which the brazing material does not contain Mg does not form any fillet. Among the invention examples, invention examples 1, 5 in which the brazing material does not contain Mg or Bi
6 and 7 have an oxygen concentration of 500 pp in the nitrogen atmosphere brazing furnace
It was confirmed that the fillet formation rate was 100% and good bondability was exhibited within the range of m, but the oxygen concentration was 500.
If it exceeds ppm, the fillet formation rate becomes low. on the other hand,
Among the invention examples, invention examples 2, 3, 4, 8, 9, 10, 11 in which the brazing material contains a predetermined amount of either Mg or Bi are fillets even if the oxygen concentration in the nitrogen atmosphere brazing furnace exceeds 500 ppm. A good bondability is shown at a formation rate of 100%.

The corrosion resistance was evaluated by using a brazing sheet of 5 layers or 3 layers (0.5 mmt × 70 mm × 150 m).
oxygen concentration of 50 ppm as external corrosion resistance evaluation using m)
A CASS test for one month according to JIS H 8681 was carried out on the single plate after brazing and heating. This is to evaluate the sacrificial anticorrosion effect on the core material. After the test was completed, the corrosion products were removed, and the pitting depth generated in the core material was measured by the depth of focus method. The results are shown in Table 4.

[0027]

[Table 4]

From the results of Table 4, among the blazing sheets of the present invention, invention examples 5, 6, 7 corresponding to claim 3,
Since 8, 9, 10, and 11 contain Zn, Sn, and In, it was confirmed that the sacrificial anticorrosion effect works and the pitting depth is shallow.
In the invention examples corresponding to claim 3, S in the brazing material
If the contents of i and Mg are constant, the pitting depth tends to become shallower as the contents of Zn, Sn and In increase.

[0029]

According to the present invention, no expensive equipment such as a vacuum furnace or a highly airtight atmosphere furnace is required, and since no flux is required and the consumption of inert gas is small, the cost is low, and at the time of brazing and assembling. Brazing with excellent workability by just sandwiching is possible. It is also possible to obtain a brazed product having even better corrosion resistance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an arrangement of layers of an aluminum brazing sheet according to the present invention. Figure 1 (a) shows the configuration of the double-sided brazing material clad,
FIG. 1B shows the case of layers, and FIG. 1C shows the case of four layers of single-sided brazing filler metal clad.

FIG. 2 is a schematic diagram showing a mechanism of leaching of a brazing material and wetting and spreading of molten brazing material.

FIG. 3 is an external view of a T-joint test piece used for brazing property evaluation in Examples.

[Explanation of symbols]

1 brazing material 2 Thin skin material 3 core material 4 oxide film 5 brazing sheet 6 Joint partner material (base material)

Claims (5)

[Claims] 1. Al-S as an intermediate material between a thin skin material and a core material.
An i-based alloy brazing material is used, and an aluminum alloy having a solidus temperature higher than the liquidus temperature of the brazing material is used for the thin skin material and the core material, and brazing without flux in an inert gas atmosphere. Aluminum alloy brazing sheet. 2. The Al—Si alloy brazing material further comprises Mg.
0.1-5% (same as mass% or less), Bi0.01-
The aluminum alloy brazing sheet according to claim 1, which contains 0.5% of one or two kinds. 3. The Al—Si alloy brazing material further comprises Zn.
0.1-5%, In0.01-0.1%, Sn0.01
The aluminum alloy brazing sheet according to claim 1 or 2, wherein the aluminum alloy brazing sheet contains 0.1 to 0.1% of one or more. 4. The aluminum alloy braces according to claims 1 to 3.
A brazing method characterized by brazing without flux in an inert gas atmosphere using a singing sheet. 5. A brazed product brazed by the method of claim 4.