JPH10175065A - Aluminum alloy powder brazing filler metal excellent in brazeability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good brazeability with a small quantity of a brazing filler metal by locally fusing a joining member with using a hyper-eutectic Al-Si alloy powder essentially consisting of Si for a brazing filler metal when brazing aluminum or aluminum alloy. SOLUTION: An eutectic Al-Si alloy used contains <13-60wt.% Si as well as a small quantity of a adding element except Si. This alloy is pulverized by a conventional method, after adjusting to about a max particle size 75μm, is appropriately mixed with flux to be made to a brazing filler metal. Further, when coating the brazing filler metal on a joining part, the brazing filler metal is mixed with a solvent and a binder to make adhesion easy. After the brazing filler metal is stuck to a joining part, by heating to 580-620 deg.C, an excessive Si in the brazing filler metal is diffused/intruded into a base metal to lower a melting temp. of the base metal, further to melt part of the base metal, the molten base metal flows together with the brazing filler metal to fill a joining part clearance and forms a fillet. In this method part of the base metal is melted to supplement the brazing filler metal, a required quantity of the brazing filler metal can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum alloy powder brazing material used for brazing a joining member made of aluminum or an aluminum alloy.

[0002]

2. Description of the Related Art There is a brazing method as a method of joining aluminum members. In this brazing method, a brazing material is clad on a core material and provided as a brazing sheet,
It is provided as a wire or plate. In addition, a powdered brazing material has also been developed in which the brazing material is powdered and applied to the joint surface and brazed. The above-mentioned powdered brazing material has attracted attention as it has a small restriction on the shape of the joint portion and the like, and can be easily applied to places where the conventional brazing material is difficult to dispose, such as a complicated-shaped product.

[0003]

However, when brazing with a powdered brazing material obtained by pulverizing a brazing material, the brazing amount of the brazing sheet must be reduced in order to obtain brazing properties equivalent to those of a conventional brazing sheet. It is necessary to apply the same amount of powder brazing material. For this reason, joints with large gaps (for example, joints between heat exchanger tubes and headers) and joints that require the formation of large fillets are required because the amount of brazing material required for brazing is significantly increased. Will also increase. However, when the application amount of the brazing powder is increased, there is a limit to the application amount that can be applied by one coat (flow coating method or the like), so that repeated coating is required, and the number of application times increases, leading to an increase in manufacturing cost. There's a problem. In addition, since the powder brazing material is expensive, if the usage amount increases, the material cost also increases. Therefore, the conventional powder brazing has a drawback in that these are problems and the advantages of the powder brazing material cannot be fully obtained. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a powder brazing material that can be satisfactorily brazed with a small amount of brazing material used.

[0004]

Means for Solving the Problems Conventionally, in brazing aluminum or an aluminum alloy, not only a powder brazing material but also an Al-Si alloy is used as an alloy for the brazing material. Al-Si alloys are eutectic alloys having excellent melting points, corrosion resistance, and the like.
What contains Si around the eutectic point, that is, around several to 12% is used. When the content of Si increases, the base material (joining material) is eroded, so the maximum Si content is 13% (for example, JIS BA4047).
However, the present inventors have contradicted that the hypereutectic Al-S
The present inventors have found that the use of an i-type alloy as a powdered brazing material causes local melting of the base material, thereby enabling reliable brazing with a small amount of brazing material, leading to the present invention. However, if this hypereutectic brazing material is used as a brazing sheet or a plate brazing material other than powder brazing material, the hypereutectic alloy forms a huge and strong Si crystallized substance, so that it is extremely rollable. However, the hypereutectic Al-Si alloy is useful when used as a powdered brazing material because it is poor in shape and cannot be processed into a plate shape.

[0005] That is, the first of the brazing powders of the present invention.
The invention is characterized by comprising a powdery hypereutectic Al-Si alloy. Further, the second invention is the first invention, wherein the Al—Si-based alloy contains Si: 13% by weight or more.
It is characterized by containing 60%. A third invention is characterized in that, in the first or second invention, a flux and an aluminum alloy powder are mixed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hypereutectic Al-Si of the present invention
The system alloy is an Al alloy containing Si as a main component, and may contain a small amount of additional elements in addition to Si. Naturally, only Si is contained, and the remainder is impurities and Al.
May be used. Although the Si content that becomes the eutectic point varies depending on other added components, it is usually about 12% by weight, and the present invention exceeds 13% to 60%.
% Is a desirable range of the Si content.

Here, if the Si content is 13% or less, the brazing material becomes a eutectic or hypoeutectic alloy, and the effect of dissolving the base material cannot be sufficiently obtained, and the effect of reducing the amount of the brazing material is not obtained. Because of the small size, the lower limit is desirably 13%. On the other hand, if the Si content exceeds 60%, excessive erosion of the base material occurs, causing problems such as a decrease in strength. In addition, the melting point of the brazing material becomes 1150 ° C. or more, and it is difficult to melt the powdered brazing material during production. Therefore, the Si content should be 13 to 60 watts.
t% was made desirable. For the same reason, it is more desirable to set the lower limit to exceed 15% and to set the upper limit to 45%, and it is even more preferable to set the lower limit to 20% and the upper limit to 30%. In these desirable ranges, appropriate dissolution in the base material occurs, so that it is possible to effectively reduce the amount of the brazing material while maintaining good brazing properties.

[0008] The Al-Si alloy whose components are determined from the above viewpoint can be powdered by a conventional method, but is adjusted to an appropriate particle size (for example, a maximum particle size of 75 µm). This aluminum alloy powder can be mixed with a flux to form a powder brazing material, if desired, and these are mixed at an appropriate mixing ratio. As the flux, a fluoride or chloride flux can be used, but the type of the present invention is not particularly limited.

When the powdered brazing material is adhered to the joint, various kinds of solvents and binders can be mixed to facilitate the adhesion. As the solvent, water, alcohols (particularly, aliphatic alcohols having 1 to 8 carbon atoms) and the like can be used. As the binder, any binder can be used as long as it can fix the powder satisfactorily without deteriorating the properties of the joint, and examples thereof include a water-soluble polymer compound having a carboxyl group or an acrylic or methacrylic resin. . The above-mentioned alloy powder is appropriately mixed and adhered to the joining material. The method is not particularly limited as the present invention, but, for example, means such as a spray method, a shower method, a flow coater method, a roll coater method, a brush coating method, and a dipping method can be used.

After the powder brazing material is attached, the brazing material is heated to an appropriate temperature in an appropriate atmosphere to dissolve the brazing material. The heating temperature at this time is desirably 580 to 620 ° C. 580 ° C
In the following, partial melting of the brazing material and the base material does not proceed, and good brazing is difficult. On the other hand, if the temperature exceeds 620 ° C., significant erosion occurs, so the above temperature range is desirable. In the hypereutectic alloy brazing material of the present invention, since Si is excessive, the Si diffuses and flows into the base material during brazing, lowering the melting point of the base material and melting (eroding) a part thereof. A part of the melted base material flows together with the applied powdered braze, filling gaps in the joints and forming fillets. That is, a part of the base material also acts as a brazing material to supplement the amount of brazing material necessary for joining, so that the amount of powder brazing material to be applied (required) can be reduced. As a result, the cost can be reduced by reducing the amount of the brazing powder used and the number of times of application.

It is to be noted that pure Si powder may be used in place of the present brazing powder. However, when pure Si powder is used, the base material is eroded in a part of the base material before forming a fillet. The erosion in the direction is remarkable, and there is a place where the thickness of the base material is extremely thin, so that a through hole is easily generated due to corrosion, or the strength of the joining member is reduced, thereby causing a problem in corrosion resistance and strength. Therefore, it is difficult to use. Therefore, it is necessary to avoid Al-Si based alloys having excessive amounts of Si for the same reason as described above. In the case of brazing with the powdered brazing material of the present invention, a part of the base material becomes brazed and the base material plate thickness after brazing decreases, so that a member having a relatively large plate thickness (for example, a plate thickness of 0.5 mm or more) Suitable for brazing to).

[0012]

EXAMPLE As shown in Table 1, the Si content was 7.5 to 65%.
Aluminum alloy powder (maximum particle size 75μ)
m) was prepared, and a fluoride flux was prepared as a flux, and an acrylic resin was prepared as a binder. These were mixed at a weight ratio of 10: 1: 1 to prepare a brazing powder. As a comparative example, pure Si was similarly prepared as a powder brazing material. An inverse T-shaped gap filling test shown in FIG. Specifically, the JIS A3003 alloy is placed horizontally as a mating material 1, and the powdered brazing material is coated on both surfaces of the JIS A3003 alloy as a base material 2 by a flow coating method. And a bar-shaped spacer 3 is arranged at one end of the installation surface to form a mating member 1.
A small gap 4 was formed between the substrate 2 and the base material 2. These are 600
When the brazing using flux is performed in an inert atmosphere by heating at a temperature of 5 ° C. × 5 minutes, the brazing material, the base material and a part of the mating material are dissolved, and the brazing portion 5 is formed in the small gap 4. Was. After brazing, as shown in FIGS.
And the maximum erosion depth D were measured, and the results are shown in Table 1.

[0013]

[Table 1]

As is clear from the table, in the test piece having a brazing filler metal Si content of 15 wt% or more, a good brazing property (gap filling property) was obtained with a small amount of coating and a number of times of coating. The amount of dissolution (maximum erosion depth) is also moderately obtained. In particular, when the Si content is 20 to 30 wt%, the maximum erosion depth is relatively shallow, and a good brazed joint can be obtained. On the other hand, in the case where the Si content exceeds 60 wt% or pure Si, the maximum erosion depth is deep, indicating that the base material is excessively eroded.

[0015]

As described above, according to the aluminum alloy powder of the present invention, since a hypereutectic aluminum alloy is used, the amount of the brazing material is equal to or greater than that of the conventionally known brazing material with a much smaller amount of brazing material. Can be obtained. Therefore, the usage amount and the number of times of application of the powder brazing material can be reduced, and the manufacturing cost can be significantly reduced without impairing the brazing property. Further, the amount of Si in the above aluminum alloy exceeds 13% by weight to 60%.
%, The above-mentioned action is reliably obtained, and excessive dissolution of the joining material is prevented, and good brazing is ensured.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an assembled state of a test material in a brazing test according to an embodiment of the present invention.

FIG. 2 is an enlarged front view of the brazing portion after brazing.

FIG. 3 is an enlarged side view of the brazing portion after brazing.

[Explanation of symbols]

 1 mating material 2 base material 4 small gap 5 brazing part

Claims (3)

[Claims] An aluminum alloy powder brazing material having excellent brazing properties, comprising a powdered hypereutectic Al-Si alloy. 2. The Al—Si based alloy contains Si:
The aluminum alloy powder brazing material having excellent brazing properties according to claim 1, wherein the brazing material contains 13 to 60%. 3. The brazing material according to claim 1, wherein the flux and the aluminum alloy powder are mixed.