JP2001105174A - Aluminum alloy brazing sheet, its production and aluminum alloy heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy brazing sheet and its production method, by which good brazing property is obtained under a severe brazing condition of low vacuum, in particular a brazing environment of >=1×10-2 Pa, a production of highly reliable heat exchanger and reduction of a production cost are made possible, a leakage defect rate is reduced, sufficiently pressure- resistant strength is achieved and an external appearance defect is reduced. SOLUTION: In an aluminum alloy brazing sheet in which Al-Si-Mg-Bi ally brazing filler metal is clad on one face or both faces of an Al or Al alloy sheet, either of the following conditions is satisfied; an oxidized film thickness of the surface of a brazing filler metal before brazing is 2-29 nm or a Mg content existing in the most surface layer of the brazing filler metal before brazing is <=25% in an analysis value of the most surface layer or a carbon content existing in the most surface layer of the brazing filler metal before brazing is <=30% in an analysis value of the most surface layer. After final cold rolling or final annealing of the brazing sheet, the brazing sheet is preferably produced by subjecting to pickling cleaning or alkali cleaning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy brazing sheet, more specifically, a heat exchanger member for automobiles such as a radiator, an evaporator or condenser for a car air conditioner, various oil coolers, a heat exchanger member for electric equipment, industrial machinery, and the like. The present invention relates to an aluminum alloy brazing sheet suitably used as a member of an aluminum alloy heat exchanger joined by vacuum brazing, a method for producing the same, and an aluminum alloy heat exchanger using the aluminum alloy brazing sheet.

[0002]

2. Description of the Related Art Conventionally, aluminum alloy brazing sheets for vacuum brazing include 3003 alloy and 3005 alloy.
Alloy, Al-Mn alloy such as 3105 alloy, Al-M
4004 alloy or 4 on a core material made of an n-Cu alloy or an Al-Mn-Cu-Ti alloy on both surfaces or one surface.
A clad brazing material made of an Al-Si-Mg alloy such as alloy 101 is used.

[0003] These aluminum alloy brazing sheets are usually assembled with a brazing material in a core ingot, hot-clad rolled to form a three-layer or two-layer clad material, and then, if necessary, annealed. It is manufactured by cold rolling to a predetermined thickness in a process. Brazing sheets for members requiring formability, such as a laminated evaporator and a radiator header, are subjected to final annealing to obtain an O material.

[0004] The brazing sheet manufactured as described above is press-formed, degreased, and assembled into each part shape, and then placed in a vacuum brazing furnace. Usually, in a high vacuum atmosphere at a level of 10 ^-3 Pa, The brazing is performed by heating to a temperature of 585 to 605 ° C.

[0005] Vacuum brazing uses a brazing material containing Mg as described above, and makes the brazing atmosphere a high vacuum.
By evaporating the Mg in the brazing material, the oxide film on the surface of the aluminum alloy to be brazed is destroyed, and the wettability of the brazing is achieved. During the brazing, the evaporation of Mg is activated from around 500 ° C. Together with the oxide film destruction
Brazing is enabled by the getter action of the evaporated Mg on the oxidizing gas.

[0006] In recent years, the productivity and cost reduction of aluminum alloy heat exchangers have been increasingly promoted. For example, in order to improve productivity, the shortening of the brazing tact time and the increase in the number of products loaded have been performed. As a result, deterioration of the degree of vacuum in the vacuum brazing furnace, a decrease in temperature, a variation in temperature, and the like are likely to occur, and the brazing conditions tend to be severe.

[0007] Under severe brazing conditions, if a problem occurs in the brazing condition, a braze that does not form a sufficient fillet may occur, or the surface may turn brown without giving metallic luster. In addition, poor brazing is likely to occur, which lowers product reliability and yield. Also,
Insufficient brazing causes leakage at the brazed portion and no longer serves as a heat exchanger. Furthermore, due to seasonal fluctuations, especially during heavy rains such as during the rainy season, the humidity increases, and the dew point in the brazing furnace also increases. Insufficient brazing is more likely to occur.

Under these circumstances, in order to further improve the productivity and reduce the cost of the aluminum alloy heat exchanger, a brazing sheet that can be brazed stably even under severe brazing conditions has been demanded. In order to obtain an aluminum alloy brazing sheet that satisfies this requirement, the inventors reexamined the factors affecting the brazing property in vacuum brazing.

In vacuum brazing, the oxide film on the surface of the brazing material inhibits the evaporation of Mg, and the strong oxide film is not destroyed during heating, causing brazing failure. On the other hand, the rolling oil adhering during the production of the brazing sheet and the press oil adhering during the production process of the heat exchanger cover the surface in the form of a film, which is a factor that impairs the brazing properties. In particular, when these adhered oils are heated to cause seizure or a carbon film, the brazing properties are significantly impaired.

[0010] Even when rolling oil or press oil is attached, or when baking or a carbon film is present, brazing can be performed under brazing conditions under ordinary high vacuum (vacuum degree 5 × 10 ^-3 Pa or less). Often possible. In order to achieve more stable vacuum brazing, in the manufacture of heat exchangers with a hollow structure such as a drone cup type evaporator, brazing properties are improved by promoting the destruction of the surface oxide film inside the hollow structure with poor exhaust characteristics. In order to make the oxide film thinner by performing alkali cleaning or acid cleaning after the rolling step or the annealing step, it has been proposed (Japanese Patent Application Laid-Open No. 62-54091).
JP, JP-A-4-341647).

However, under the strict brazing conditions in which the degree of vacuum is deteriorated, the above-mentioned adhered oil definitely causes a hindrance to brazing properties. In addition, it has been experienced that even when alkali cleaning or acid cleaning is performed, brazing defects may still frequently occur.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to further experiments and studies on the relationship between a surface oxide film in an aluminum alloy brazing sheet, a deposited oil and a carbon film caused by the deposited oil, and the brazing property in vacuum brazing. The purpose is to achieve good brazing properties even under severe vacuum conditions with low vacuum, enabling the production of highly reliable heat exchangers and a reduction in manufacturing costs. An aluminum alloy brazing sheet, a method for producing the same, and an aluminum alloy heat exchanger using the aluminum alloy brazing sheet.

[0013]

In order to achieve the above object, an aluminum alloy brazing sheet according to claim 1 of the present invention is provided on one or both surfaces of Al or an Al alloy, with an Al-Si-Mg alloy brazing material or Al-Si-
In an aluminum alloy brazing sheet clad with a Mg-Bi alloy brazing material, the thickness of the oxide film on the surface of the brazing material before brazing is 2 to 20 nm, and the outermost layer of the brazing material before brazing. The amount of Mg present is not more than 25% by analysis of the outermost layer, and the amount of carbon present in the outermost layer of the brazing material before brazing is not more than 30% by analysis of the outermost layer. Characterized by satisfying any one of the following requirements.

According to a second aspect of the present invention, there is provided the aluminum alloy brazing sheet according to the first aspect, wherein one or both surfaces of Al or an Al alloy are coated with an Al-Si-Mg alloy brazing material or an Al-Si-Mg-Bi alloy. In an aluminum alloy brazing sheet clad with a brazing material, the thickness of the oxide film on the surface of the brazing material before brazing is 2 to 20 nm, and the amount of Mg present in the outermost surface layer of the brazing material before brazing is minimized. 4. The method according to claim 3, wherein the amount of carbon present in the outermost layer of the brazing material before brazing is not more than 30% in the analysis value of the outermost layer.
An aluminum alloy brazing sheet according to claims 1 or 2, wherein the aluminum alloy is an Al-Mn alloy.

The method for manufacturing an aluminum alloy brazing sheet according to the present invention is the method for manufacturing an aluminum alloy brazing sheet according to claim 1 or 2, wherein after the final cold rolling or final annealing of the brazing sheet, acid cleaning or alkali cleaning is performed. It is characterized by washing.

Further, an aluminum alloy heat exchanger according to the present invention is characterized in that the aluminum alloy brazing sheet according to any one of claims 1 to 3 is formed, assembled and vacuum brazed. I do.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy brazing sheet of the present invention is formed on one or both surfaces of Al or an Al alloy by using an Al-Si-Mg alloy brazing material or Al-Si
-An aluminum alloy brazing sheet clad with an Mg-Bi alloy brazing material, wherein the thickness of the oxide film on the surface of the brazing material before brazing is 2 to 20 nm (2 nm or more and 2 nm or more).
0 nm or less), and the requirement that the amount of Mg present in the outermost layer of the brazing material before brazing is 25% or less in the analysis value of the outermost layer. One of the requirements that the amount of carbon present in the outermost layer of the material is 30% or less in the analysis value of the outermost layer must be provided.

The most preferred form of the brazing sheet is that the thickness of the oxide film on the surface of the brazing material before brazing is 2 to 2 mm.
0 nm, the amount of Mg present in the outermost layer of the brazing material before brazing is 25% or less in the analysis of the outermost layer, and the amount of carbon present in the outermost layer of the brazing material before brazing is This satisfies all the constituent requirements that the analysis value is 30% or less, and according to this embodiment, it is possible to reliably achieve good brazing properties even under severe brazing conditions with a low degree of vacuum.

Various Al alloys can be used as the Al alloy serving as the core material of the brazing sheet. Preferably, an Al—Mn alloy such as 3003 alloy is used. Al-Mn alloys include Mg, Cu, Zn, In, Sn, Ti, Cr, and Zr according to the strength and corrosion resistance requirements.
Etc. can be added. Pure aluminum can also be used as the core material.

As the Al-Si-Mg-based alloy and the Al-Si-Mg-Bi-based alloy constituting the brazing material, 4004 alloy, 4104, which is usually used for vacuum brazing, is used.
A core material standardized to JIS (JIS Z3263) or the like, which is made of an alloy or a material to which the amount of Si or Mg is increased or decreased as necessary, and to which components such as Zn, In, or Sn are added as necessary. A well-known combination of brazing materials can be applied. The brazing sheet of the present invention may be one in which a sacrificial anode material such as 7072 alloy is clad on the opposite side of the brazing material, or one in which an intermediate layer is provided between the core material and the brazing material to form four layers. The cladding ratio of the brazing material to the core material is not particularly limited, but usually a cladding ratio of about 3 to 20% is used.

(Surface Oxide Film) Normally, a natural oxide film having a thickness of about 2 nm exists on the surface of aluminum and aluminum alloy. This natural oxide film is thin and dense in the case of pure aluminum, but in the case of an aluminum alloy containing Mg, the oxide film has defects, and is subjected to hot rolling, annealing, or a vacuum brazing process. At an initial high temperature and in an atmosphere or an oxidizing gas atmosphere containing a large amount of oxygen or water, Mg intensively diffuses into a defective portion of the oxide film to generate magnesium oxide.

Since the generated magnesium oxide is porous, Mg diffuses one after another under heating, and as a result, the oxide film (magnesium oxide) grows and becomes thicker. Since the destruction of the film becomes insufficient, the wettability of the brazing cannot be ensured, resulting in poor brazing. On the other hand, if the oxide film is too thin,
In particular, it has been found that the brazing property is poor under severe brazing conditions with a low degree of vacuum. A preferable oxide film thickness for achieving a sound brazing property even under severe brazing conditions with a low degree of vacuum is 2 to 20 nm, and a more preferable oxide film thickness is 2 to 10 nm.

(Mg in the surface layer) When the ratio of magnesium oxide in the oxide film was increased, the diffusion of Mg generated during the brazing heating was concentrated on the magnesium oxide portion because the magnesium oxide was porous, and was diffused. Mg is concentrated in the surface layer. The diffused Mg is oxidized by the oxidizing gas in the atmosphere, and the oxide film becomes thicker. At the time of brazing, the destruction of the oxide film by Mg becomes insufficient, so that the wettability of the molten solder becomes poor and the solder breaks. It is easy to occur. The ratio of magnesium oxide in the oxide film is determined by the amount of Mg concentrated in the surface layer, and the limit of magnesium oxide for obtaining good brazing properties is that it exists in the outermost layer of the brazing material before brazing. The amount of Mg is 25% in the analysis value of the outermost layer
Or less, and more preferably 20% or less.

(C of Surface Layer) The formation of a carbon film due to the rolling oil adhering during the production of the brazing sheet and the press oil adhering during the production process of the heat exchanger particularly causes the brazing property to be impaired. In vacuum brazing, the limit of the carbon film for providing good brazing properties is that the amount of carbon present in the outermost layer of the brazing material before brazing is set to 30% or less in an analysis value of the outermost layer. Is more preferable, and more preferably 15% or less.

In the aluminum alloy brazing sheet of the present invention, in order to obtain the above-mentioned surface oxide film thickness, surface layer Mg amount and surface layer C amount, after the final cold rolling or the final cold rolling in the brazing sheet manufacturing process. After annealing, it is preferable to perform cleaning with an acid-based or alkali-based cleaning agent. It is particularly effective to perform cleaning after the final cold rolling.

By performing the cleaning treatment, the oxide film which has become thicker in the brazing sheet manufacturing process and the rolling oil adhered in the rolling process are removed. When the cleaning treatment is performed before the final annealing after the final cold rolling, the rolling oil is prevented from burning during the annealing, and the moisture and the hydrate on the surface adhering during the cleaning can be evaporated during the annealing heating. Such adsorbed water and hydrate evaporate from the surface during brazing, but do not evaporate sufficiently in a low-vacuum brazing atmosphere, and oxidize on the surface or near the surface to thicken the oxide film. In addition, the evaporated water may further make the vacuum atmosphere worse.

As the cleaning agent, an acid-based or an alkaline-based cleaning agent is used, and a chemical agent capable of etching the surface of aluminum from fine to small is preferable. Sulfuric acid type, nitric acid type, hydrofluoric acid type, hydrochloric acid type, carbonic acid type simple substance or a mixture thereof can be used as the acid type cleaning agent. Silicic acid type, phosphoric acid type, boric acid can be used as the alkaline type cleaning agent. System, caustic system, carbonate system alone or a mixture thereof can be used. More preferably, a surfactant is added to the detergent.

The aluminum alloy brazing sheet of the present invention is formed into a predetermined shape as a member of an aluminum alloy heat exchanger, degreased, assembled with other members, and charged into a vacuum brazing furnace to form a vacuum. Brazed.

[0029]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples, and the effects thereof will be demonstrated. The present embodiment shows one embodiment of the present invention, and the present invention is not limited to this embodiment.

EXAMPLE 1, COMPARATIVE EXAMPLE 1 A core material which was cast, homogenized and chamfered according to a conventional method was used.
The upper and lower portions of the ingot of the 03 alloy are cast and homogenized according to a conventional method, and hot-rolled to obtain a predetermined thickness of the brazing material.
A 104 alloy sheet material is assembled, hot-rolled to form a double-sided clad brazing sheet having a cladding ratio of 15%, and finally cold-rolled to a sheet thickness of 0.6 mm, and then subjected to a phosphate-based alkali cleaning and cleaning. Thereafter, it was sufficiently washed with water and dried to obtain a test material. In addition, the oxide film thickness of the test material, the Mg amount of the outermost layer, and the C amount were adjusted by changing the cleaning conditions (cleaning temperature and time).

The obtained test material was analyzed for oxygen content by Auger electron spectroscopy (AES), and Ar ion sputtering was performed in the depth direction to measure the thickness of the oxide film. These conditions were implemented in accordance with ASTM. Here, the thickness of the oxide film was calculated by converting the thickness of the oxide film on the surface of the test material from the sputtering rate of SiO ₂ . In terms of conversion, the sputtering time per unit time is determined by measuring the time required for Ar ions to sputter the SiO ₂ plate, which is known in advance, and this sputter rate is used as the sputter rate of the oxide film. Is performed by converting Further, the amount of Mg and the amount of C in the outermost layer were analyzed by Auger electron spectroscopy (AES). Further, the obtained test material was cut into a width of 55 mm and a length of 25 mm, and a brazing property test described below was performed to evaluate the brazing property, and the discoloration due to oxidation of the surface after brazing was observed. The results are shown in Tables 1 and 2. In addition, in Table 2, the values out of the conditions of the present invention are underlined.

(1) Brazing test (standard LWS-T8001 by the Japan Light Metal Welding Structure Association): As shown in FIG. 1, test materials (0.6 mm thick, 55 mm wide, 25 m long)
m) 1 is vertical, horizontal material (JIS3003 alloy) 2
After one side of the test material 1 is brought into contact with the horizontal material 2 and assembled on the other side with the spacer rod 3 (diameter 3 mm) interposed therebetween, 585 is set in a vacuum furnace having a different ultimate pressure level.
C. (no holding time), and after this brazing heating, as shown in FIG. 2, the gap filling length L of the brazing filler metal filled in the gap between the clad material and the test material was measured. It is determined that those having a gap filling length L of 10 mm or more have been joined, the number of joining in ten tests is counted, and the brazing property is evaluated. (2) Observation of surface discoloration after brazing: After brazing, a good surface without surface discoloration shows metallic luster, but an oxidatively discolored surface exhibits brown to black.

The evaluation of the brazing property and the surface discoloration are as follows. Brazing property evaluation ：: 10 joints, ：: 8 to 9 joints,
Δ: 5 to 7 junctions, ×: less than 5 junctions Surface discoloration evaluation ：: 10 good, ○: 8 to 9 good,
Δ: 5 to 7 pieces good, ×: less than 5 pieces good

[0034]

[Table 1]

[0035]

[Table 2]

As can be seen from Table 1, the test materials according to the present invention were all excellent in brazing properties, and no discoloration of the surface after brazing was observed. On the other hand, as shown in Table 2, test materials (test materials Nos. 19 to 27) in which the thickness of the oxide film, which is an essential component of the present invention, was outside the limited range of the present invention.
And even if the thickness of the oxide film is within the scope of the present invention,
When the amount of Mg or C in the outermost layer was out of the range of the present invention (test materials Nos. 17 to 18), good brazing properties were obtained in the case of high vacuum, but the degree of vacuum was low. Under severe brazing conditions, brazing properties were poor and surface discoloration was observed. The degree of vacuum of 5 × 10 ⁻³ Pa is a normal high vacuum state, 3 × 10 ⁻² Pa is a state considered to be near the critical pressure at which brazing is possible, and 1 × 10 ⁻² Pa is a low vacuum state.

Example 2, Comparative Example 2 In the same process as in Example 1, the final cold-rolled sheet having a thickness of 0.1 mm was used.
A 6 mm brazing sheet was prepared and 400
The final annealing was performed at a temperature of 5 ° C. for 5 hours, followed by a phosphoric acid-based alkali cleaning, followed by sufficient washing with water and drying to obtain a test material. In addition, the oxide film thickness of the test material, the Mg amount of the outermost layer,
The C amount was adjusted by changing the washing conditions (washing temperature, time).

The obtained test material was subjected to depth analysis by Ar ion sputtering as in Example 1, and the thickness of the oxide film was measured in accordance with the definition of ASTM. Here, the thickness of the oxide film on the surface of the brazing sheet was calculated from the sputtering speed of SiO ₂ . In addition, Mg of the outermost layer
The amount and C amount were analyzed by Auger electron spectroscopy (AES). Further, the obtained test material was cut into a length of 55 mm and a width of 25 mm, and the same brazing property test as in Example 1 was performed to evaluate the brazing property, and to observe whether discoloration due to oxidation of the surface after brazing was observed. did. The results are shown in Tables 3 and 4. In Table 4, those that are outside the conditions of the present invention are underlined.

[0039]

[Table 3]

[0040]

[Table 4]

As shown in Table 3, all of the test materials according to the present invention showed some discoloration, but were excellent in brazing properties. In contrast, as shown in Table 4,
Test materials (test materials Nos. 46 to 54) in which the thickness of the oxide film, which is an essential component of the present invention, is out of the limited range of the present invention, and even if the thickness of the oxide film is within the limited range of the present invention. When the amount of Mg or the amount of C in the outermost layer was out of the range of the present invention (test materials Nos. 44 to 45), good brazing properties were obtained in the case of high vacuum. Under low severe brazing conditions, poor brazing properties and surface discoloration were observed.

[0042]

According to the present invention, good brazing properties can be obtained under a severe brazing condition with a low degree of vacuum, especially in a brazing atmosphere of 1 × 10 ⁻² Pa or more, and a highly reliable heat exchange can be achieved. Alloy brazing sheet, a method of manufacturing the same, and a method of manufacturing an aluminum alloy capable of reducing the cost of leaks in a heat exchanger, achieving a sufficient pressure resistance, and reducing the appearance defect, thereby enabling reduction in the production cost of the heat exchanger. An exchanger is provided.

[Brief description of the drawings]

FIG. 1 is a side view showing an arrangement of test materials before a brazing property test in the present invention.

FIG. 2 is a side view showing a flow state of the brazing material after the test of FIG. 1;

[Explanation of symbols]

 1 Test material 2 Horizontal material 3 Spacer rod

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Maeda 5-1-1-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries Co., Ltd. F-term (reference) 4K053 PA10 PA13 QA01 QA05 QA07 RA15 RA16 RA17 RA18 RA19 RA22 RA23 RA25 RA27 RA28 TA03 TA04 TA06 TA12

Claims (5)

[Claims] 1. An Al—Si—Mg alloy brazing material or Al—Si—alloy on one or both sides of Al or an Al alloy.
In an aluminum alloy brazing sheet clad with a Mg-Bi alloy brazing material, the thickness of the oxide film on the surface of the brazing material before brazing is 2 to 20 nm, and the outermost layer of the brazing material before brazing. The amount of Mg present is not more than 25% (% by weight, the same applies hereinafter) in the analysis value of the outermost layer, and the amount of carbon present in the outermost layer of the brazing material before brazing is the analysis value of the outermost layer. At 30% (wt%, same hereafter)
An aluminum alloy brazing sheet characterized by satisfying one of the following requirements. 2. An Al—Si—Mg alloy brazing material or Al—Si—alloy on one or both sides of Al or an Al alloy.
In an aluminum alloy brazing sheet clad with a Mg-Bi-based alloy brazing material, the thickness of the oxide film on the surface of the brazing material before brazing is 2 to 20 nm, and Mg present in the outermost layer of the brazing material before brazing. The amount of carbon present in the outermost layer of the brazing material before brazing is less than or equal to 30% by analysis of the outermost layer. 2. The aluminum alloy brazing sheet according to 1. 3. The aluminum alloy brazing sheet according to claim 1, wherein the aluminum alloy is an Al—Mn alloy. 4. The method for producing an aluminum alloy brazing sheet according to claim 1, wherein after the final cold rolling or the final annealing of the brazing sheet,
A method for producing an aluminum alloy brazing sheet, comprising performing acid cleaning or alkali cleaning. 5. An aluminum alloy heat exchanger, wherein the aluminum alloy brazing sheet according to claim 1 is formed, assembled and vacuum brazed.