JPH10175061A - Heat exchanger excellent in brazeability and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an using quantity of a brazing filler metal by using a hyper-eutectic Al, Si alloy brazing filler metal when producing an aluminum or aluminum alloy heat exchanger. SOLUTION: A tube 2 is inserted into a hole 1a of a header part 1, a brazing filler metal consisting of a hyper-eutectic Al, Si alloy powder containing 13-60wt.% Si and flux is stuck to the surrounding of a joining part between the header 1 and the tube 2 so as to encircle and brazing is conducted. In brazing, it is desirable to heat in an appropriate atomosphere at 580-620 deg.C. By this method, an excessive Si in the brazing filler metal is diffused/intruded into a base metal to reduce a melting temp. of the base metal, further to melt part of the base metal, the molten base metal is flowed together with the powder brazing filler metal 5 coated to fill a clearance between the header 1 and tube 2, further to form a fillet. Thus, part of the base metal is used for a brazing filler metal for joining, an using quantity of the brazing filler metal is decreased without impairing brazeability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger having a header portion made of aluminum or aluminum alloy and a tube connected thereto and having excellent brazing properties, and a method of manufacturing the heat exchanger. .

[0002]

2. Description of the Related Art As an example of the structure of a generally known heat exchanger, as shown in FIG. 3, two pipe-shaped headers 1, 1 are connected by a plurality of tubes 2,. Radiation fins 3, 3 are arranged between 2 and 2. When manufacturing the heat exchanger, generally, the tube 2 is inserted into the hole 1a of the header portion 1 formed of a brazing sheet as shown in FIG. The heat radiating fins 3 are arranged to assemble a heat exchanger member, and by heating these members, the tube 2 and the heat radiating fin are brazed. Further, the header 1 and the tube 2 are brazed with a tubular joint. The tubular joint between the header 1 and the tube 2 is
The gap is set large so that assembly can be done easily,
In order to be able to completely join the gap without causing refrigerant leakage, a solder is supplied at the joint portion. It is to be noted that a powder brazing material that can be easily arranged regardless of the shape of the joint and that can be easily prepared is suitable for the above-mentioned brazing.

[0003]

In order to completely fill the gap between the joint between the header and the tube, a large amount of powdered brazing material must be applied to the joint between the header and the tube. However, for example, when the tube and the fin are joined with the powder brazing material, the application amount is about 5 to 8
About twice as much is needed. However, when increasing the amount of powder brazing material to be applied, there is a limit to the amount of coating that can be applied by a single coat (flow coating method or the like), so that repeated coating is required, and the number of applications 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. In addition, when the amount of the brazing material applied increases, the brazing material layer inevitably becomes very thick, and the brazing material easily falls off due to rubbing with other members, vibration, or the like during assembly of the heat exchanger. Since the dropped portion causes brazing failure, attention must be paid to the handling of the joining member, and there has been a problem that workability is poor. The present invention has been made in view of the above circumstances, and a heat exchanger having excellent brazing properties that can be favorably brazed with a small amount of brazing material and that facilitates handling of members during manufacture. It is an object to provide a method for manufacturing the heat exchanger.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, a heat exchanger excellent in brazing properties according to the first invention of the present invention is a joint between an aluminum or aluminum alloy header portion and a tube. Are formed by fusion of a hypereutectic Al-Si alloy braze and a base material. The heat exchanger having excellent brazing properties according to the second aspect of the present invention is the heat exchanger according to the first aspect, wherein the Al—Si alloy is S% by weight%.
i: It is characterized by containing 13 to 60%.

In a third aspect of the invention, a method of manufacturing a heat exchanger comprises brazing a hypereutectic Al-Si alloy powder brazing material when joining a tube to an aluminum or aluminum alloy header. It is characterized by. A method of manufacturing a heat exchanger according to a fourth aspect of the present invention is to provide a method for manufacturing a heat exchanger, comprising: attaching a hypereutectic Al-Si alloy powder brazing material to a tube joining scheduled portion of an aluminum or aluminum alloy header portion; It is characterized in that the tube is joined to the header by heating the brazing material. A method for manufacturing a heat exchanger according to a fifth invention is characterized in that, in the third or fourth invention, the brazing material comprises a mixture of an Al—Si alloy powder and a flux.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The heat exchanger of the present invention can be used for various uses such as for automobiles, and the present invention is not particularly limited in use. Also, in the specific structure, it is necessary to have a joint portion between the header portion and the tube, but the joint form and other structures are not particularly limited.

[0007] The hypereutectic Al-Si alloy braze of the present invention is an Al alloy containing Si as a main component, and may contain a small amount of additional elements in addition to Si. Also,
Naturally, it may contain only Si, and the balance may consist of impurities and Al. Although the Si content that becomes the eutectic point varies depending on the other added components, it is usually about 12% by weight, and the preferred range of the Si content is over 13% to 60% in the present invention.

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.

The Al-Si alloy whose components are determined from the above viewpoints can be powdered by a conventional method, and 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 powder brazing material is adhered to the joint, various 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.

In the manufacturing method of the present invention, as shown in FIG. 1, the tube 2 is inserted into the hole 1a of the header 1 and the above-mentioned powdered brazing material surrounds the periphery of the joining portion 4 of the tube 2 in the header 1. The material 5 is adhered, and the radiating fins 3 are arranged thereon as shown in FIG. 3 to obtain a heat exchanger assembly. After the powder brazing material 5 is adhered, the brazing material is heated by heating to an appropriate temperature in an appropriate atmosphere. The heating temperature at this time is 580 to 620 ° C.
Is desirable. At 580 ° C. or lower, partial dissolution of the brazing filler metal and the base material does not proceed, and good brazing is difficult.
Above this temperature range is desirable because of significant erosion. Since the hypereutectic alloy brazing material used in the present invention has excessive Si, 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 molten base material flows together with the applied powder braze, and as shown in FIG. 2, they are fused to form a gap between the two members 1 and 2 and to form a fillet to form the joint 6. Form. That is, since a part of the base material also acts as a brazing material to supplement the amount of brazing material necessary for joining, the application (required) amount of the powder brazing material can be reduced without impairing the brazing properties. As a result, the cost can be reduced by reducing the amount of the brazing powder used and the number of times of application. Further, since the thickness of the brazing material adhered can be reduced, the falling off of the brazing material at the time of assembling the heat exchanger is reduced, the handling becomes easy, and the working efficiency is improved.

It is to be noted that pure Si powder may be used in place of the present brazing material. 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. Here, when considering the allowable melting amount of the base material, the melting depth in the base material is less than 0.5 mm, although it depends on the thickness of the base material and the like, from the viewpoint of avoiding a decrease in strength and a decrease in corrosion resistance. It is desirable. 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 is reduced.
(5 mm or more).

[0013]

EXAMPLE In order to evaluate the brazing property between the header portion and the tube in the heat exchanger, a simulation test was performed using the following test pieces. That is, as shown in Table 1, an aluminum alloy powder having a different amount of Si (maximum particle size 7
5 μm), a fluoride flux as a flux and an acrylic resin as a binder were mixed at a weight ratio of 10: 1: 1 to prepare a powder brazing filler metal. As a comparative example, pure Si was similarly prepared as a powder brazing material.

An inverse T-shaped gap filling test shown in FIG. 5 was conducted by using the above-mentioned brazing powder and changing the coating amount. Specifically, the JIS A3003 alloy is placed horizontally as a mating material 10, and the powdered brazing material is applied to both surfaces of the JIS A3003 alloy as a base material 11 by a flow coating method. And a bar-shaped spacer 12 was arranged at one end of the installation surface to form a small gap 13 between the mating material 10 and the base material 11.
When these were heated at 600 ° C. for 5 minutes and brazing was performed using a flux in an inert atmosphere, the brazing material was dissolved and a brazing portion (joining portion) 14 was formed in the small gap 13.
In addition, the brazing part 14 was formed by melting a part of the powder brazing material, the base material 11 and the mating material 10. After brazing,
As shown in FIGS. 6 and 7, the filling length L and the maximum erosion depth D of the brazing portion 14 were measured, and the results are shown in Table 1. In addition, the same amount of the same brazing material as described above was applied to the planned joints on the actual heat exchanger composed of JIS A3003 alloy for both the header and tube, and a brazing test was performed under the same conditions as above. The joined state between the part and the tube was observed. As a result, no brazing was judged to be good at the joint portion, and good brazing was judged to have a leak at the joint. The results are also shown in Table 1.

[0015]

[Table 1]

As is clear from the table, in the test piece having a brazing filler metal Si content of 15 wt% or more, good brazing properties (gap filling properties) were obtained with a small amount of application and the number of times of application. 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.

[0017]

As described above, according to the heat exchanger of the present invention, the joint between the header and the tube is formed by the fusion of the hypereutectic Al-Si alloy solder and the base material. Therefore, the amount of the brazing material used can be relatively reduced, and the joining portion is securely and firmly brazed. In addition,
If the brazing material contains Si: 13 to 60% by weight, excessive melting of the base material is prevented and the amount of melting of the base material becomes appropriate. Good brazing properties can be obtained without lowering or lowering the corrosion resistance.

Further, according to the heat exchanger manufacturing method of the present invention, when joining the tube to the aluminum or aluminum alloy header portion, brazing is performed using a hypereutectic Al-Si alloy powder brazing material. Therefore, it is possible to obtain a good brazing property at the joint portion between the header portion and the tube with a much smaller amount of brazing material than conventionally known brazing materials. 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. At the time of the production, a hypereutectic Al-Si alloy powder brazing material was adhered to the portion to be joined to the tube, a tube was incorporated into the header portion, and the brazing material was heated to separate the tube and the header portion. By joining, a part of the base material to which the brazing material is adhered is effectively and appropriately melted, and the above-described operation is further ensured. Also,
If a brazing material made of a mixture of an Al-Si alloy powder and a flux is used, the flux application step in the brazing step can be omitted, and the surface oxide film of the alloy powder is effectively used during brazing. To make good brazing easier.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a joint portion between a header portion and a tube before brazing according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the same after brazing.

FIG. 3 is a perspective view of the heat exchanger at the time of assembly or product.

FIG. 4 is an enlarged cross-sectional view showing a state where a tube is inserted into the header portion.

FIG. 5 is a perspective view showing an assembled state of a test material in a brazing test according to the embodiment of the present invention.

FIG. 6 is an enlarged front view of the brazing portion after brazing.

FIG. 7 is an enlarged side view of the brazing portion after brazing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Header part 2 Tube 3 Heat radiation fin 4 Planned joining part 5 Powder brazing material 6 Joining part 10 Counterpart material 11 Base material 13 Small gap 14 Brazing part

Claims (5)

[Claims] The joint between the aluminum or aluminum alloy header and the tube is made of hypereutectic Al-S.
A heat exchanger excellent in brazing properties, characterized by being formed by fusing an i-based alloy braze with a base material. 2. The Al—Si based alloy contains Si:
The heat exchanger having excellent brazing properties according to claim 1, wherein the heat exchanger contains 13 to 60%. 3. A method for joining a tube to an aluminum or aluminum alloy header portion, wherein the hypereutectic Al-
A method for manufacturing a heat exchanger, comprising brazing using a Si-based alloy powder brazing material. 4. A hypereutectic Al-S is formed at a tube joining portion of an aluminum or aluminum alloy header portion.
A method of manufacturing a heat exchanger, comprising attaching a brazing material to an i-type alloy powder, incorporating a tube into the header portion, and heating the brazing material to join the tube and the header portion. 5. The method for manufacturing a heat exchanger according to claim 3, wherein the brazing material is made of a mixture of an Al—Si alloy powder and a flux.