JPH07331407A - Production of anticorrosive aluminum material for brazing - Google Patents

Abstract

PURPOSE:To produce an anticorrosive aluminum material for brazing capable of showing excellent brazability while the good adhesion of a thermally sprayed layer to an aluminum material is secured and furthermore excellent in appearance quality. CONSTITUTION:Primary powder for brazing constituted of Al-Si alloy powder and Si powder and secondary powder for anticorrosion constituted of Zn or Zn alloy powder are mixed to form into a powdery mixture and this mixed powder is thermally sprayed on the surface of an aluminum material. The thermal spraying is executed preferably in such a manner that the melting of the primary powder is suppressed while the secondary powder is melted. Moreover, preferably, the coating weight of the Si components in the surface of the aluminum material is regulated to 3 to 20g/m<2>, and the coating weight of the Zn components to 6 to 14g/m<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is preferably used for a method of manufacturing an aluminum material for brazing used as a constituent member of a heat exchanger manufactured according to the brazing specification, and particularly for a member requiring corrosion resistance. The present invention relates to a method for producing an anticorrosion aluminum material for brazing.

[0002] In this specification, the term aluminum is used to include its alloys.

[0003]

2. Description of the Related Art A surface of an aluminum material is sprayed with A
A technique for forming a brazing material layer made of an 1-Si alloy to form a brazing material is already known. However, corrosion resistance cannot be imparted after brazing only by forming the brazing material layer.

Therefore, as a method for producing an aluminum material for brazing which can impart corrosion resistance, first, Zn or Zn alloy is sprayed on the surface of the aluminum material to form an anticorrosion layer prior to the spray formation of the brazing material layer. A method of spraying a brazing filler metal has been proposed (for example, JP-A-1-1577).
94, JP-A-2-46969).

However, in this method, since the corrosion-preventing layer and the brazing material layer are sequentially formed separately, the thermal spraying devices must be arranged in two stages in front and rear, which requires a long production line and a high cost. There was a flaw.

Therefore, the present applicant mixed a first powder for brazing made of Al--Si alloy powder and a second powder for corrosion prevention made of Zn or Zn alloy powder to prepare a mixed powder, and mixing this powder. A method of spraying powder on the surface of an aluminum material has been proposed (Japanese Patent Application No. 5-355017). According to this method, Zn in the sprayed layer diffuses to the surface of the aluminum material at the time of brazing heat and exhibits an anticorrosion effect, and the Al-Si alloy in the sprayed layer functions as a brazing material.
It has become possible to manufacture an anticorrosion aluminum material for brazing while eliminating the need to sequentially form the anticorrosion layer and the brazing material layer separately.

As another method, the present applicant mixes a first powder made of Si powder and a second powder made of Zn or Zn alloy powder into a mixed powder, and the mixed powder is sprayed on the surface of an aluminum material. I proposed a method (Japanese Patent Application No. 5)
-271890). Also by this method, Zn in the sprayed layer diffuses to the surface of the aluminum material during the brazing heat and exerts an anticorrosion effect, and Si in the sprayed layer reacts with Al of the aluminum material during the brazing heat to generate Al--Si. Since a brazing material can be formed and brazing can be performed using this brazing material, it is possible to manufacture an anticorrosion aluminum material for brazing while eliminating the need to sequentially form the anticorrosion layer and the brazing material layer separately. became.

[0008]

However, among the above-mentioned prior proposals, Al-Si is used as the first powder for brazing.
In the method using the system alloy powder, the thickness of the sprayed layer must be increased in order to secure the adhesion amount of the Si component necessary for brazing, and therefore the adhesion between the aluminum material and the sprayed layer is poor. In some cases, the sprayed layer may fall off from the aluminum material, resulting in defective brazing.

On the other hand, in the method using Si powder as the first powder, the thickness of the sprayed layer can be made thin and the adhesion with the aluminum material can be excellent, but it is better than the case of Al--Si alloy powder. In addition to being slightly inferior in brazing property, the appearance of the aluminum material was likely to turn black, which eventually deteriorated the appearance of the brazed product.

The present invention has been made in view of the above technical background, and can exhibit excellent brazing property while ensuring good adhesion of the sprayed layer to the aluminum material, and has excellent appearance quality. Also provides a method for producing an excellent anticorrosion aluminum material for brazing.

[0011]

[Means for Solving the Problems] The above-mentioned objects are Al-S
A brazing first powder made of an i-based alloy powder and a Si powder and a second anticorrosion powder made of Zn or a Zn alloy powder are mixed to form a mixed powder, and the mixed powder is sprayed onto the surface of an aluminum material. It is achieved by a method for producing an anticorrosive aluminum material for brazing, which comprises:

The composition of the aluminum material used in the present invention is not particularly limited, and various materials required in connection with the application may be used. The method of processing the aluminum material is not particularly limited, and extruded materials, rolled materials, cast materials and various other materials can be used.
Further, the cross-sectional shape of the aluminum material is not limited, and it may be manufactured in any shape determined in relation to the application.

The Al-Si alloy powder in the first powder functions as a brazing filler metal component as it is after thermal spraying. Here, the Al-Si alloy is 5 to 40 wt.
%, And the balance consisting of Al and unavoidable impurities is generally used, but it does not mean only an Al alloy containing only Si, but Al, Si, and a third component added, for example, Al. It may be a -Si-Zn alloy,
It may be a mixture of an Al-Si alloy and an Al-Si-Zn alloy.

Si in the first powder also functions as a brazing material after thermal spraying. That is, Si existing on the surface of the aluminum material after thermal spraying reacts with Al of the aluminum material during the brazing heat to form an Al-Si alloy as the brazing material. The Si powder preferably has a purity of 98% or more in order to form a high quality Al-Si alloy.

The Zn or Zn alloy powder as the second powder imparts corrosion resistance to the aluminum material after brazing. The second powder may be a Zn simple substance powder, a Zn alloy powder such as Zn-Al system powder, or a mixture of Zn powder and Zn-Al system alloy powder. Further, the Zn-Al alloy powder does not mean only the Zn-Al alloy powder containing only Zn and Al,
For example, Zn—Al to which a third component is added in addition to Zn and Al
-Si alloy powder may be used.

The mixing ratio of the Al-Si alloy powder and the Si powder in the first powder is 95: 5 to 50: 5 by weight.
It is desirable to set it to 0. If the weight ratio of the Al-Si alloy powder is less than 50:50, the amount of Si powder increases, the appearance of the aluminum material tends to blacken, and the brazing property becomes poor. On the other hand, when the weight ratio of the Al-Si alloy powder exceeds 95: 5, the thickness of the sprayed layer becomes too thick to secure the amount of Si required for brazing of the aluminum material, and thus the aluminum material is There is a possibility that the adhesion with the sprayed layer will deteriorate. Since the corrosion resistance of the aluminum material largely depends on the amount of Zn component deposited on the surface of the aluminum material after thermal spraying, the Al—Si alloy powder as the first powder and the Si powder and the Zn or Zn alloy as the second powder. The mixing ratio with the powder is not so important. Generally, the mixing ratio of the first powder and the second powder is preferably set to about 50:50 by weight.

By spraying the mixed powder of the first powder and the second powder, a sprayed layer in which the Al—Si alloy and Si and Zn or Zn alloy are mixed and mixed is formed on the surface of the aluminum material. The adhesion amount of Si component in the sprayed layer is 3
It is good to set it to about ²⁰ g / m ² . 3 g / m is less than ² may result in subsequent brazing becomes insufficient, 20 g / m ²
There is a risk that erosion will occur if the value exceeds. More preferably, the adhesion amount of the Si component in the sprayed layer is 4 g / m
^{It is} preferably ² or more, and 7 g / m ² or less. On the other hand, the amount of Zn component deposited is preferably 6 to 14 g / m ² . If it is less than 6 g / m ² , the corrosion resistance after brazing may be insufficient, and if it exceeds 14 g / m ² , initial corrosion may be severe and the corrosion resistance may be poor. More preferably, the deposition amount of Zn component in the sprayed layer is 8 g / m
^{It is} preferably ² or more, and 12 g / m ² or less. The amount of Al deposited on the sprayed layer is not particularly limited.

Such an adhesion amount may be determined by adjusting the thickness of the sprayed layer in consideration of Zn and Si contents in the mixed powder of the first powder and the second powder. Further, the sprayed layer may be formed only on one side of the aluminum material,
As shown in FIG. 1, thermal spraying guns (4) and (4) may be arranged above and below the aluminum material (2) to perform thermal spraying, thereby forming thermal sprayed layers on both upper and lower surfaces.

The conditions of thermal spraying are not particularly limited, but it is desirable to melt the second powder for corrosion prevention (preferably complete melting), while melt the first powder for brazing. It is preferable to suppress and perform it in the solid state or by melting only the surface. The reason for this is as follows.

That is, the reason why it is desirable not to melt the first powder is that Al-S is not melted at a high temperature where it is completely melted.
In the case of i-based alloy powder particles, a strong oxide film is likely to be formed on the surface, which not only hinders the brazing property, but when completely melted, it will already reach the inside of the particles when solidified after thermal spraying. This is because the same organizational state as that in which the brazing was performed will occur and the brazing function will no longer be fully exerted during subsequent brazing. Further, if the Si powder particles are completely melted, there is a risk of reacting with Al that is a matrix immediately after thermal spraying.

On the other hand, the reason why the second anticorrosive powder should be melted is that the second powder is melted and liquefied so as to adhere to the periphery of the first powder particles whose solid state or only the surface is melted, or This is because by filling between the first powder particles, the "paste-like effect" is exerted, the first powder particles are held as a binder, and the first powder particles are brought into close contact with the aluminum material. In this way, when the second powder is melted and the first powder is suppressed from being melted and the thermal spraying is performed,
The thermal spray layer formed on the surface of the aluminum material is almost first
A large number of brazing metal particles in the powder state are dispersed in the melt-solidified Zn or Zn alloy of the second powder and are held on the surface of the aluminum material via the Zn or Zn alloy. In addition, a part of the first powder may be completely melted, or a part of the second powder may be unmelted.

As described above, the specific thermal spraying conditions for suppressing the melting of the first powder and for melting the second powder to perform thermal spraying are not high temperature thermal spraying such as plasma arc thermal spraying but thermal spraying temperature. Is preferably 1000 to 4000 ° C. (preferably 2300 to 3500 ° C.). Spraying temperature is 1000 ℃
If it is less than the above range, the melting of the powder surface is insufficient and there is a risk that the adhesion with the aluminum material is deteriorated. On the contrary, if the temperature exceeds 4000 ° C., there is a possibility that the inside of the first powder is completely melted. A flame spraying method can be mentioned as a spraying method for realizing such a spraying temperature range.

The spraying distance is preferably 50 to 500 mm.
If it is less than 50 mm, the powder may be excessively melted and the first powder particles may be oxidized to deteriorate the brazing property. On the other hand, 500m
If it exceeds m, the completely melted second powder particles may be re-solidified before reaching the aluminum material, resulting in deterioration of adhesion yield and deterioration of adhesion of the sprayed layer. A particularly preferable spraying distance is 150 to 300 mm.

Further, if the particle size of the first powder is too small, complete melting is likely to occur, so it is preferable to secure the powder particle size on average of 5 μm or more. On the other hand, if the average particle size exceeds 200 μm, the adhesion tends to deteriorate and the adhesion yield may deteriorate. Particularly preferred particle size of the first powder is 2
It is 0 to 150 μm.

On the other hand, the average particle size of the second powder is 200 μm.
The following is good. When it exceeds 200 μm, it becomes difficult to melt, so that the “paste-like effect” is deteriorated and the adhesion yield is deteriorated. Particularly preferably, it is 150 μm or less.

The first and second powders have a powder content of 1 in order to smoothly pass through the thin nozzle of the spray gun.
It is desirable that 0 wt% or more, preferably 50 wt% or more are spherical particles.

The above thermal spraying is preferably carried out in a non-oxidizing atmosphere such as N ₂ atmosphere in order to prevent the powder particles from being oxidized. Further, for the thermal spraying, it is preferable from the standpoint of production efficiency that the thermal spraying be performed continuously while unwinding the coiled aluminum material, or when the aluminum material is an extruded material, extruding the aluminum material from the extruder.

The aluminum material, on which the mixed powder is sprayed to form the sprayed layer as described above, is then subjected to brazing as a component of a brazed product and heated to a temperature of about 600 ° C. By this heating, Si in the sprayed layer reacts with Al in the aluminum material to form an Al-Si alloy brazing material, and Al-S originally present in the brazing material and the sprayed layer.
The i alloy brazing material is melted to achieve brazing. Further, the Zn component in the sprayed layer starts melting while destroying the oxide film on the surface of the Al material, and diffuses to the surface of the aluminum material to form an anticorrosion layer.

[0029]

As the first powder for brazing, not only Al-Si based alloy powder but also Si powder is used. Therefore, it is necessary for brazing as in the case of thermal spraying using only Al-Si based alloy powder. The inconvenience of having to increase the thickness of the sprayed layer to secure the amount of Si is reduced, and the necessary amount of Si component attached can be secured in the thin sprayed layer. Therefore, the inferior adhesion between the aluminum material and the sprayed layer reduces the inconvenience that the sprayed layer falls off the aluminum material and causes brazing failure. In addition, inconvenience of poor brazing property such as in the case of using only Si powder and inconvenience that the appearance of the brazed product is deteriorated due to blackening of the appearance of the aluminum material are alleviated.

Of course, since the mixed powder of the first powder for brazing and the second powder for anticorrosion is sprayed, it is not necessary to separately form the anticorrosion layer and the brazing material layer.

When the second powder is melted while the first powder is sprayed while suppressing the melting, the "paste-like effect" by the melting of the second powder causes the brazing as the first powder. The metal particles for use are held on the surface of the aluminum material with good adhesion. And, it is prevented that the first powder is in a high temperature state such that the first powder is completely melted, the oxidation of the particles is suppressed, and at least the core portion of the first powder particles is not melted,
The structure state before thermal spraying is maintained as it is, the entire Al—Si first powder particles are prevented from having the same solidified structure as that already brazed, or the Si particles are completely melted. The reaction with Al that is the matrix immediately after thermal spraying is prevented.

[0032]

Example: Width 16 mm made of JIS1100 Al alloy
× 3 mm high × 0.5 mm thick porous flat extruded material (2)
1 was extruded from the extruder (1), cooled in a cooling water tank (3), and then continuously wound around a coil (6) as shown in FIGS. Then, on the exit side of the cooling water tank (3), the spray guns (4) and (4) were arranged above and below the extruded material (2) in a state of being inclined in the coil direction. As the spray gun (4), a frame type gun having a nozzle portion as shown in FIG. 3 was used. In this spray gun, a mixed fuel gas of combustion gas and oxygen supplied through a fuel feed pipe (41) is ejected from a tip of a nozzle portion and ignited to form a cylindrical frame, and a powder feed pipe (42 The raw material powder (43) fed into the flame together with the carrier gas is heated. Then, the heated powder is atomized by a jet of compressed air supplied from the compressed air supply pipe (44) and is blown forward to be attached to the surface of the extruded material (2). (45) in FIG. 3 shows an air flow. In the spray gun of the present embodiment, O ₂ as the fuel gas of 700 liters / min, propylene: using 68 l / min gas mixture, the amount of compressed air 800 l /
Minutes The flame temperature (spraying temperature) is about 2700
° C, the spraying distance was 300 mm.

In the above-mentioned constitution, the kind of powder to be sprayed is changed to various kinds as shown in Table 1, the melting of the first powder is suppressed and the second powder is melted and sprayed, and the extruded material (2) is sprayed. Thermal sprayed layers (5) and (5) were formed on both upper and lower surfaces by coating.

Then, with respect to the obtained brazing aluminum material, Al component, Si component, Zn in the sprayed layer
The ingredients were measured. The results are shown in Table 1.

Next, each of the brazing aluminum materials produced as described above was used for a heat exchange tube and assembled into a so-called multi-flow type aluminum heat exchanger core shown in FIGS. 4 and 5. Note that FIG. 4 and FIG.
The heat exchanger core shown in (1) is composed of a large number of tubes (11) made of the aluminum material for brazing and arranged horizontally in parallel in the horizontal state, and corrugated fins ( 12) and side plates (13) (13) located outside the outermost corrugated fins
With a length of 350 mm × width of 550 mm × depth of 16 mm. The corrugated fins (12)
As for the length 530 made of JIS3003 Al alloy
mm × width 16 mm × height 8 mm × wall thickness 0.12 mm was used. Also, as the side plate (13), J
530 mm length x width 16 made of IS1100 Al alloy
mm × wall thickness 0.8 mm was used.

Next, in each of the above heat exchanger core assemblies,
A suspension (concentration 10%) in which a flux of 82 wt% AlF ₄ +18 wt% K ₃ AlF ₆ having an average particle diameter of 80 μm is suspended in water is applied and dried, and then O ₂ concentration: 50 pp
m, dew point: 600 ° C. in N ₂ gas atmosphere of −60 ° C.
After heating for 3 minutes, each component was brazed.

The tubes (11) of each heat exchanger core
For the above, the brazing property was evaluated by visually observing the joint state with the corrugated fin (12). The results are shown in Table 1.

[0038]

[Table 1] In addition, sample Nos. 2, 3, 5, which had good brazing properties,
Each of the heat exchanger cores 6, 8 to 10 was subjected to a CCT corrosion test (composite corrosion test), and the corrosion state of the tube after 180 cycles was examined. The results are shown in Table 1.

As can be seen from the results in Table 1, a comparative product using only Al--Si alloy powder as the brazing filler metal component (Sample N
In the case of o10), the total deposition amount for obtaining the predetermined deposition amount of Si component is large, and therefore, the film thickness of the thermal spray layer is large and the adhesion of the thermal spray layer to the aluminum material is poor. On the other hand, since the Si powder is mixed in the product of the present invention, it can be seen that the Si component deposition amount is large despite the small total deposition amount. Also, from the comparison of sample Nos. 2 and 6, Al-
It can also be seen that by changing the compounding ratio of the Si alloy powder and the Si powder, the Si component deposition amount can be increased with a smaller total deposition amount. Also, from the comparison of sample Nos. 6, 8, and 9,
It can also be seen that by changing the amount of Si in the Al-Si alloy powder as the first powder, the amount of Si component attached can be increased with a smaller total amount attached.

Further, visual observation of the appearance color tone of each tube after brazing revealed that no remarkable blackening occurred, but a slight tendency of blackening was observed in part of Sample No. 7.

In addition, practical products (Nos. 2, 6, 8;
It can also be seen that 9) shows excellent brazing property and corrosion resistance.

[0042]

According to the present invention, since the first powder for brazing is composed of the Al--Si alloy powder and the Si powder, only the Al--Si alloy powder is used as the first powder. As in the case, there is no choice but to increase the thickness of the thermal spray layer in order to secure the amount of Si component necessary for brazing, and therefore the inconvenience that the adhesion between the aluminum material and the thermal spray layer is poor, As in the case of using Si powder as the first powder, the brazing property is slightly inferior to that in the case of Al-Si alloy powder, and the appearance of the aluminum material is easily blackened, which in turn deteriorates the appearance of the brazed product. The inconvenience of doing can be reduced. As a result, a large amount of Si component can be secured even if the thickness of the sprayed layer is small, and thus it can be excellent in adhesion with an aluminum material, and can exhibit excellent brazing properties and also in appearance quality. Excellent aluminum materials can be manufactured.

Moreover, Zn is added to the above first brazing powder.
Alternatively, since the second powder for corrosion protection made of Zn alloy powder is mixed and sprayed, the Zn component in the sprayed layer can exert an anticorrosion function, and an aluminum material for brazing excellent in corrosion resistance can be formed. Needless to say, it is not necessary to sequentially form the anticorrosion layer and the brazing material layer separately, and only one thermal spraying device is required, and it is possible to prevent the manufacturing line from becoming longer and the cost to be increased due to the installation of a plurality of thermal spraying devices.

When the second powder is melted and the first powder is sprayed while suppressing the melting, the melted Zn or Zn alloy during the spraying adheres to the periphery of the first powder particles, or Al-as the first powder particles, even if the first powder is not melted, because it acts as a binder that is filled between the first powder particles and holds the particles, and adheres well to the surface of the aluminum material. Si-based alloy particles and Si particles can be stably retained on the surface of the aluminum material, and the adhesiveness of the sprayed layer can be further improved.

The amount of Si component deposited on the surface of the aluminum material is 3 to 20 g / m ² , and the amount of Zn component deposited is 6 to 14.
When it is g / m ² , further excellent brazing property and corrosion resistance can be surely realized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a thermal spraying process in an example.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is an enlarged cross-sectional view of a thermal spray gun used in an example.

FIG. 4 is a front view of a multi-flow type aluminum heat exchanger core manufactured in an example.

5 is a perspective view showing a tube and a corrugated fin of the heat exchanger core of FIG. 4 separately.

[Explanation of symbols]

 2 ... Aluminum material (aluminum extruded material) 5 ... Thermal sprayed layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Kojima 6224, Kaiyamacho, Sakai City Showa Aluminum Co., Ltd.

Claims (3)

[Claims] 1. A brazing first powder composed of an Al—Si alloy powder and a Si powder and a second anticorrosion powder composed of Zn or a Zn alloy powder are mixed to prepare a mixed powder, and the mixed powder is prepared. A method for producing an anticorrosion aluminum material for brazing, characterized in that the surface of the aluminum material is sprayed. 2. The method for producing an anticorrosion aluminum material for brazing according to claim 1, wherein the second powder is melted while the melting of the first powder is suppressed to perform thermal spraying. 3. The amount of Si component deposited on the surface of the aluminum material is 3 to 20 g / m ² , and the amount of Zn component deposited is 6 to 14 g / m ² .
The method for producing an anticorrosion aluminum material for brazing according to claim 1 or 2, which is m ² .