JPH11264042A - Aluminum alloy brazing filler sheet for fluid passage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the corrosion resistance of a brazing filler sheet by controlling a distribution state of Cu, In, after heating for brazing by cladding an Al-Si alloy brazing filter metal on one face or both faces of an Al alloy core material of a specific composition consisting of Cu, In and Al. SOLUTION: On one face or both faces of an Al alloy core material consisting of, by weight, 0.3-1.5% Cu, 0.03-0.3% In, as necessary, at least one kind among <=1.2% Si, <=2.0% Fe, <=2.0% Mn, <=0.3% Ti, <=1.0% Mg, <=0.5 Cr, <=0.5% Zr, <=2.0% Zn and the balance Al with inevitable impurities. This Al-Si alloy brazing filler metal, as necessary, contains 0.03-0.3% In. By this method, In is uniformly diffused in a plate thickness direction, by making an electric potential of a brazing filler metal surface more base, an electric potential difference is enlarged, the corrosion resistance of obtained brazing filler sheet is improved.

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 used for heat exchangers for automobiles and various industries, and more particularly to an aluminum alloy brazing sheet for forming a fluid passage having excellent corrosion resistance.

[0002]

2. Description of the Related Art Brazing is an effective means for producing a complex structure made of aluminum alloy. At present, there is a vacuum brazing method (hereinafter referred to as VB method) which does not require flux, and a non-corrosive flux brazing method (hereinafter referred to as NB method) in which a non-corrosive flux is applied and then heated in a nitrogen atmosphere. .

[0003] The brazing sheet for the heat exchanger is J
It is standardized by IS Z3263 and JIS H4000, and its configuration is JIS3003 as a core material.
(Representative example: Al-0.15 wt% Cu-1.1 wt% Mn alloy), JIS3005 (Representative example: Al-1.1 wt% Mn-
0.4 wt% Mg alloy), JIS3105 (Representative example: Al-
0.6 wt% Mn-0.6 wt% Mg alloy), and JIS4004 (representative example Al-
10wt% Si-1.5wt% Mg alloy), JIS4104
(Representative example: Al-10 wt% Si-1.2 wt% Mg-0.1
wt% Bi alloy), for NB, JIS 4045 (representative example Al-10 wt% Si alloy), JIS4343 (representative example A)
It is usual to use 1-7.5 wt% Si alloy). The brazing sheet has a plate thickness of 0.2 to 1.2 mm, of which the brazing material is clad on one or both sides at a thickness of 5 to 30% of the plate thickness.

As a heat exchanger made of aluminum alloy having a hollow structure using such a brazing sheet, a drone cup type evaporator, an oil cooler, a radiator and the like are manufactured.

[0005] For example, a drone cup type evaporator (8) as shown in FIG. 3 forms a brazing sheet to form a refrigerant passage constituting member (1) shown in FIGS. 1 and 2, and this member (1) is illustrated in FIG. 3, the corrugated fins (2) are disposed between the laminated members (1),
Further, a side plate (5) (5 '), a refrigerant inlet pipe (6), and a refrigerant outlet pipe (7) are arranged and assembled, and this is brazed by a VB method or an NB method.
Heating to 73K is performed.

On the other hand, the radiator has a corrugated fin (10) integrally formed between a plurality of flat tubes (9) (refrigerant passages) as shown in FIG. Opened in the space formed by the header (11) and the tank (12), the high-temperature refrigerant flows from the space on one tank side through the flat tube (9) to the space on the other tank (12) side. And the refrigerant cooled by the heat exchange between the tube (9) and the fin (10) is circulated again. As a tube of such a heat exchanger, for example, JIS3003 alloy is used as a core material, JIS7072 alloy is used as a lining material on the inner side, that is, a side that is always in contact with the refrigerant, and usually, on the outer side of the core material, Using a brazing sheet clad with a brazing material such as JIS 4045 alloy or the like, the tube is formed by electric resistance welding. Then, assembling with the tube and other members such as corrugated fins, about 87
Brazing at 3K by NB method or VB method.

[0007]

In recent years, with the reduction in the weight of automobiles, these heat exchangers have been required to be made thinner. On the other hand, the environment in which the automobile is used varies, but corrosive substances such as Cl ⁻ such as sea salt particles and snow melting salt and SO _x from exhaust gas adhere to the heat exchanger depending on the environment. In particular, the evaporator concentrates corrosive substances due to repeated use of the air conditioner due to repeated use of the air conditioner, and even if chromate treatment is performed, the evaporator material requires a high corrosion resistant material.

In particular, in the case of manufacturing a heat exchanger by vacuum brazing, the corrosion resistance of the core material of the brazing sheet for the heat exchanger is the most important required property for the material because the sacrificial corrosion prevention effect is small due to the restriction of the brazing process. The development of a brazing sheet having corrosion resistance has been eagerly desired, and various studies have been made.

Conventional core materials (JIS 3003, 3005,
When 3105) is used, since the Cu content of the core material is small and diffuses to the brazing material side during brazing, there is no potential difference between the brazing material and the core material, so that the brazing material sacrifices and protects the core material. When pitting corrosion occurs in the core material because of the failure, there is a problem that the material penetrates early. In addition, there is a problem in that Cu diffused in the brazing material becomes a cathode, and corrosion proceeds from the corrosion starting point. Even if the amount of Cu in the core material is increased, Cu diffuses into the brazing material layer and the potential on the surface of the brazing material becomes noble, so that the potential difference between the brazing material and the core material does not become so large. Also, if a large amount of Cu is added to the core material, Cu, Mg, etc. precipitate at the grain boundaries,
There has been a problem that intergranular corrosion is likely to occur in that portion or in the deficient layer near the grain boundary, and the self-corrosion resistance of the core material is rather deteriorated.

[0010]

The present inventors have conducted intensive studies to solve this problem. As a result, in order to provide a large potential difference between the surface of the brazing material and the inside of the core material, a large amount of Cu is added to the core material. , In at the same time is effective.

That is, the aluminum alloy brazing sheet for forming a fluid passage according to the present invention has Cu: 0.3 to 1.5.
wt., In: 0.03 to 0.3 wt.%, with the balance being one or both sides of an aluminum alloy core material consisting of aluminum and unavoidable impurities combined with an Al-Si alloy brazing material. At this time, the aluminum alloy core material further contains Si: 1.2 wt% or less,
e: 2.0 wt% or less, Mn: 2.0 wt% or less, Ti:
0.3 wt% or less, Mg: 1.0 wt% or less, Cr: 0.5
wt% or less, Zr: 0.5 wt% or less, Zn: 2.0 wt% or less.
In: 0.03-0.3 in addition to the l-Si alloy brazing material
It is effective to contain wt%.

The present invention controls the distribution of Cu and In elements from the brazing material after brazing to the core material and improves the corrosion resistance.

First, Cu, In added to the core material is used as the brazing material.
Is diffused, so that the composition of the brazing alloy is completely different from that before brazing. As described above, the corrosion resistance of the brazing alloy containing Cu is poor, but the simultaneous inclusion of In reduces the starting point of the cathode and improves the corrosion resistance of the brazing material itself. Also, since In makes the potential of the alloy base, the potential of the brazing material becomes base to the extent that it contributes to the corrosion resistance more than the core material.
Improves corrosion resistance as a brazing sheet.

Further, since the Cu added to the core material diffuses into the brazing material during brazing, a Cu concentration gradient is generated in a region from the brazing material surface to a depth of about 100 μm in the plate thickness direction. A potential gradient occurs in the material. Here, when In and Cu are simultaneously added to the core material, when the amount of Cu is small, the effect of making the potential lower by In is great.
If the amount of Cu is large, the effect of lowering the potential by In hardly occurs. Therefore, as compared with the conventional material, the brazing sheet containing In and Cu in the core material has a larger potential difference between the brazing material and the inside of the core material, and therefore has a larger potential gradient. Therefore, the brazing material acts as an effective sacrificial anticorrosion layer of the core material, and the corrosion does not become pitting, but becomes a surface corrosion in which the brazing material acts as a sacrificial layer, thereby improving corrosion resistance.

Further, In diffuses into the grain boundary of the core material during the heating by brazing. As described above, the high-Cu core material precipitates a Cu-based compound at the grain boundary, and the potential difference between the Cu-deficient layer in the grain boundary increases, so that the grain boundary corrosion preferentially corrodes the lower part in the grain boundary. Is more likely to occur. Here, the diffused In forms a compound with Cu in the grain boundary, and reduces the potential difference between the Cu-based precipitate and the grain boundary to reduce the intergranular corrosion susceptibility in order to lower the potential of the precipitate. .

By the way, combining a potential-low element such as In with Cu is disclosed in, for example,
It is known in, for example, Japanese Patent Publication No. 0455. However, in this case, Cu
The fin material is used as a sacrificial anti-corrosion material for the refrigerant passage material by increasing the strength with In and making the potential of the fin base. On the other hand, in the present invention, a high corrosion resistant material is obtained on the refrigerant passage material side by the above-described action, and thus is fundamentally different from the above-described invention for fins.

[0017]

Hereinafter, the present invention will be described in detail. First, the core material will be described. Cu is necessary to improve the strength, to make the potential of the core material after brazing noble, and to make the brazing material side a sacrificial anticorrosion layer, and is an indispensable element in the present invention. %Added. Below the lower limit, a sufficient potential difference between the inside of the core material and the brazing material cannot be provided. On the other hand, if the upper limit is exceeded, the melting point of the core material is greatly reduced, and furthermore, the intergranular corrosion of the core material tends to occur, and the self-corrosion resistance of the core material also deteriorates. Therefore, the range is 0.
3 to 1.5 wt%, preferably 0.5 to 1.0 wt%
%, More preferably 0.6 to 0.9 wt%.

As described above, In diffuses uniformly in the thickness direction, makes the potential of the brazing material surface lower and increases the potential difference from the core material, and also makes the potential of the eutectic portion of the brazing material base and corrodes. Is added to reduce the intergranular corrosion susceptibility by reducing the starting point of the core material and reducing the potential difference between the grain boundaries of the core material and the vicinity of the grain boundaries. The addition amount is set to 0.03 to 0.3 wt%. However, if the addition amount is less than 0.03 wt%, the effect is small.
If the content exceeds wt%, the cost increases, and edge cracking occurs during hot rolling, making material production difficult, and further, the self-corrosion resistance of the core material decreases.

Since Si precipitates an intermetallic compound with Mn and Fe to increase the strength, it is added in an amount of 1.2 wt% or less as necessary. However, if the content is less than 0.05% by weight, the effect of improving the strength is not sufficient, and if it exceeds 1.0% by weight, the core material may be melted at the time of heating by brazing.
1.0 wt%.

Fe is added as necessary to improve the strength.
Add up to wt%. If the upper limit is exceeded, the corrosion resistance deteriorates due to an increase in the cathode starting point in the core material, and the brazing material deteriorates abnormally due to abnormal diffusion of the brazing material to the core material side in order to reduce the recrystallized grain size of the core material. I do.

Mn is added in an amount of 2.0 wt% or less as needed to improve strength and prevent brazing diffusion. If the upper limit value is exceeded, the amount of brazing material diffused into the core material during brazing heating increases, thereby deteriorating brazing properties and corrosion resistance. Therefore, the addition amount is 2.0 wt% or less, but more preferably 0.4 to 1.5 wt%. If the brazing diffusion is prevented, the corrosion resistance is improved, so the addition of Mn is particularly recommended.

Ti is added in an amount of 0.3 wt% or less as necessary in order to refine the ingot structure and improve corrosion resistance. However, if the added amount exceeds 0.3 wt%, it becomes difficult to produce a material.
In addition, when adding, it is more preferable to be about 0.1-0.2 wt%.

When Mg is produced by the VB method, 1.0 wt% or less is added as necessary to improve the strength.
If it is less than wt%, the effect of improving the strength is small, and if it exceeds the upper limit, the amount of brazing material diffused into the core material during brazing heating increases, and the brazing property and corrosion resistance are reduced. Therefore, the range is more preferably 0.1 to 0.5 wt%.
In the case of a material manufactured by the NB method, the brazing property is reduced.

Since both Cr and Zr have the effect of refining the crystal grains and increasing the strength, 0.5 wt.
% Or less. However, if the content is 0.05 wt% or less, the effect of improving the strength is not sufficient, and if the content is 0.25 wt% or more, the moldability is impaired, so that the content is desirably 0.05 to 0.25 wt%.

Since Zn forms a compound with Cu and increases the strength, Zn is added in an amount of 2.0 wt% or less as necessary. If the content exceeds 2.0 wt%, the potential of the matrix in which Zn is dissolved is made low, so that the effect of adding Cu is negated. Further Zn
Is desirably not added because it has the effect of lowering the self-corrosion resistance of the alloy and reducing the effect of In.

Other unavoidable impurities include Bi,
B, Ca, Ni, Li, etc. are conceivable.
5 wt% or less is preferable from the viewpoint of corrosion resistance and moldability.

Next, the brazing material will be described. The brazing material used in the present invention is JIS400 in the case of the VB method.
Al-Si-Mg based alloys such as JIS4104 alloy and JIS4104 alloy, JIS4045 alloy and JIS43 in case of NB method
An Al-Si alloy such as 43 alloy is used. Of course, any of these general alloys may be used, but it is preferable to add In to further increase the corrosion resistance. In makes the potential of the brazing filler metal lower and reduces the corrosion starting point of the brazing filler metal. For this purpose, the amount of In is desirably set to 0.03 to 0.3% by weight. If the amount is less than 0.03% by weight, the effect is small. Edge cracks occur in the inside, making the production of the material difficult, and the self-corrosion resistance of the brazing material also decreases. The cladding ratio of the brazing material is in the range of 5 to 30% with respect to the total thickness, and is clad on one or both surfaces of the core material.

Further, the method of manufacturing the aluminum alloy brazing sheet according to the present invention can be manufactured according to a conventional method as in the conventional method. That is, predetermined aluminum alloy materials such as a core material and a brazing material are melt-cast, respectively, and these ingots are homogenized (soaking), and if necessary, rolled to a predetermined thickness. It can be manufactured by rolling, followed by cold rolling (annealing if necessary). The final thickness is 0.2-1.2 mm.

When the brazing sheet is used as a member of an evaporator, it generally has a three-layer structure of brazing material-core material-brazing material, and when it is used as a member of a radiator or a heater, it generally has a three-layer structure. It has a three-layer structure of brazing material-core material-lining material or a two-layer structure of brazing material-core material.

The brazing sheet of the present invention can be used particularly for forming a fluid passage of a heat exchanger (evaporator, radiator, heater, oil cooler, etc.). Here, the term “for the fluid passage configuration” refers to a tube plate material and a tank material through which Freon gas as a working refrigerant flows in the case of an evaporator, and a tube material, a header plate material, and a tank material through which cooling water flows in the case of a radiator.
In any case, the material itself is required to have high corrosion resistance.

The heat exchanger using the brazing sheet of the present invention is manufactured by brazing. Here, the brazing method is a conventionally used method such as VB method and NB method. Since the heat at the time of brazing causes diffusion of In and Cu, brazing heating is indispensable for using the brazing sheet of the present invention. The present invention is particularly applied to VB
It has a remarkable effect in the law.

[0032]

Next, an embodiment of the present invention will be described in detail in comparison with a comparative example.

Example 1 An aluminum alloy plate for a brazing material (JIS 4104 alloy or an alloy obtained by adding In to a 4104 alloy) was used for each of the aluminum alloy plates for the core material shown in Tables 1 and 2 with a total thickness of one side. Cladding was performed on both sides at 20% to produce a three-layer brazing sheet for aluminum alloy tube material. That is, the thickness is 0.4 mm, the thickness of the brazing material is 80 μm, and the tempering is the O material. Specifically, after the core material alloy is DC-cast to a thickness of 400 mm, homogenization treatment is performed in a temperature range of 450 to 600 ° C., and both surfaces are chamfered by 10 mm each. Hot-rolling rolling was performed. Those which could not be manufactured due to cracks generated by hot rolling were indicated by x in the column of rollability in the table. The steps after obtaining the hot-rolled coil were performed as usual (cold rolling / annealing). A sample was cut out from the obtained three-layer brazing sheet and subjected to vacuum brazing and heating at 873 K for 3 minutes in a vacuum of 6.7 × 10 ⁻³ Pa to obtain a test material.

The natural potential difference (5% NaCl) between the surface of the brazing material of these test materials and a position 100 μm from the surface of the brazing material.
Middle). In addition, a corrosion test (CASS test) was performed by coating one side of the test material with a resin, and after 750 hours had elapsed since the start of the test, the test material was taken out and the surface corrosion products were removed to check the corrosion state of the material. evaluated. For the evaluation, the pit depth of the maximum pit was measured by the depth of focus method using an optical microscope. JIS No. 5 TP was prepared from these test materials, and the tensile strength was measured. These results are shown in Tables 3 and 4.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

As is clear from Tables 3 and 4, the brazing sheet according to the present invention has excellent corrosion resistance because the potential difference between the inside of the core material and the surface of the brazing material is sufficiently large as compared with the comparative example and the conventional example. It can be seen that there is no problem in rollability and strength. On the other hand, in the comparative example and the conventional example, through pitting occurred, and in Comparative Example No. 26, the sheet broke during hot rolling, and a brazing sheet could not be produced.

(Example 2) An aluminum alloy plate for brazing material (JIS 4045 alloy or an alloy obtained by adding In to 4045 alloy) was used on one side of the aluminum alloy plates for various core materials shown in Tables 5 and 6, and other aluminum alloy plates. An aluminum alloy (Al-3% Zn alloy) plate for a lining material was combined on one side to produce a three-layer brazing sheet for an aluminum alloy tube material. That is, the plate thickness is 0.2 mm and the brazing material thickness is 30.
μm, lining material thickness 30 μm, tempering is H14 material.
Specifically, after the core material alloy is DC cast to a thickness of 400 mm,
After homogenizing in a temperature range of ~ 600 ° C and chamfering both sides by 10 mm each, it is combined with a brazing alloy plate prepared in advance (the plate thickness is set to a thickness that can obtain a product of the target brazing material thickness). Hot rolling was performed. Those which could not be manufactured due to cracks generated by hot rolling were indicated by x in the column of rollability in the table. The steps after obtaining the hot-rolled coil were performed as usual (cold rolling / annealing). A sample was cut out from the obtained three-layer brazing sheet, flux was applied at 10 g / m ² , and 873K was applied in a nitrogen gas atmosphere.
For 3 minutes to obtain a test material.

The natural potential difference between the surface of the brazing filler metal and the position 50 μm from the surface of the brazing filler metal (in 5% NaCl)
I asked. In addition, a corrosion test (CASS test) was performed by coating one side of the test material with a resin, and after 750 hours had elapsed since the start of the test, the test material was taken out and the surface corrosion products were removed to check the corrosion state of the material. evaluated. For the evaluation, the pit depth of the maximum pit was measured by the depth of focus method using an optical microscope. JIS No. 5 TP was prepared from these test materials, and the tensile strength was measured. These results are shown in Tables 7 and 8.

[0042]

[Table 5]

[0043]

[Table 6]

[0044]

[Table 7]

[0045]

[Table 8]

As is clear from Table 2, the brazing sheet according to the present invention has a sufficient potential difference between the inside of the core material and the surface of the brazing material as compared with the comparative example and the conventional example, and thus has excellent corrosion resistance. It can be seen that there is no problem in rollability and strength. On the other hand, in the comparative example and the conventional example, through pitting occurred, and in Comparative Example No. 54, it was broken at the time of hot rolling, so that a brazing sheet could not be produced.

[0047]

As described in detail above, the present invention can greatly improve the corrosion resistance of an aluminum alloy brazing sheet. Therefore, when this is used for a heat exchanger, the corrosion resistance life of the heat exchanger is remarkably increased. Thus, it is possible to improve the effect, which brings about an industrially remarkable effect.

[Brief description of the drawings]

FIG. 1 is a plan view showing a refrigerant passage constituting member for a drone cup evaporator.

FIG. 2 is a sectional view taken along the line BB 'in FIG.

FIG. 3 is an explanatory view showing an example of a heat exchanger (Drone cup evaporator), and is a schematic sectional view thereof.

FIG. 4 is a schematic diagram of a heat exchanger (radiator).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigerant passage constituent member for Dron cup evaporator 2 Fin 3 Brazing material layer 4 Core material layer 5 Side plate 6 Refrigerant inlet pipe 7 Refrigerant outlet pipe 8 Heat exchanger (Drone cup evaporator) 9 Flat tube 10 Fin 11 Header 12 Tank

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B23K 35/22 310 B23K 35/22 310E F28F 19/06 F28F 19/06 A 21/08 21/08 A (72) Inventor Yamada Chiritsu Furukawa Electric Co., Ltd. 2-6-1 Marunouchi, Chiyoda-ku, Tokyo

Claims (3)

[Claims] 1. Cu: 0.3-1.5 wt%, In: 0.
An aluminum alloy for forming a fluid passage, comprising an aluminum alloy core material containing 0.3 to 0.3 wt% and the balance being Al and unavoidable impurities, on one or both sides of which an Al-Si alloy brazing material is combined. Brazing sheet. 2. An aluminum alloy core material further comprising Si:
1.2 wt% or less, Fe: 2.0 wt% or less, Mn: 2.0
wt% or less, Ti: 0.3 wt% or less, Mg: 1.0 wt% or less, Cr: 0.5 wt% or less, Zr: 0.5 wt% or less, Z
The aluminum alloy brazing sheet according to claim 1, wherein at least one of n: 2.0 wt% or less is contained. 3. An Al-Si alloy brazing material further comprising:
n: 0.03 to 0.3 wt%.
4. The aluminum alloy brazing sheet for fluid passage configuration according to item 1.