JP3434998B2 - Heat exchanger excellent in brazing property and method for manufacturing the heat exchanger - Google Patents

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 to the header portion and having excellent brazability, and a method for 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 header portions 1 and 1 are connected by a plurality of tubes 2 ... Radiating fins 3 are disposed between 2 ... When manufacturing the above heat exchanger, generally, the tube 2 is inserted into the hole 1a of the header portion 1 made of a brazing sheet as shown in FIG. 4, and the tube 2 is made of a brazing sheet. The heat radiating fins 3 are arranged to assemble the heat exchanger members, and by heating them, the tube 2 and the heat radiating fins are brazed, and the header portion 1 and the tube 2 are brazed by a tubular joint. The tubular joint between the header portion 1 and the tube 2 is
The gap is set large so that assembly can be done easily,
It is also practiced to supply brazing filler metal to the joint portion so that this gap can be completely joined without causing refrigerant leakage. It is to be noted that the brazing powder is suitable for the brazing filler metal because it can be easily arranged regardless of the shape of the joint and can be easily prepared.

[0003]

By the way, in order to completely fill the gap between the joint portion between the header portion and the tube, a large amount of powder brazing material must be applied to the joint portion between the header portion 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
You need twice as much. However, when increasing the coating amount of the powdered brazing filler metal, there is a limit to the coating amount that can be coated with one coating (flow coating method, etc.), so multiple coatings are required and the number of coatings increases, leading to an increase in manufacturing cost. There's a problem. In addition, since the powdered brazing material is expensive, the material cost also increases as the amount used increases. Further, when the amount of the brazing filler metal applied increases, the brazing filler metal layer inevitably becomes very thick, and the brazing filler metal is likely to fall off due to friction with other members or vibration during assembly of the heat exchanger. Since the part that has fallen off causes brazing failure, there is a problem in that the handling of the joining member requires attention and the workability is poor. The present invention has been made in view of the above circumstances, and a heat exchanger excellent in brazability that can be brazed favorably with a small amount of brazing filler metal, and is therefore easy to handle during manufacturing. It is an object to provide a method for manufacturing the heat exchanger.

[0004]

In order to solve the above problems, in the present invention, the heat exchanger excellent in brazing property of the first invention is a joint part between a header part made of aluminum or aluminum alloy and a tube. However, Si: over 15-60%
A hypereutectic Al-Si alloy containing Al and the balance Al
It is characterized by being formed by fusing a powdered brazing material and a base material .

In the method of manufacturing the heat exchanger of the second invention, when the tube is joined to the header part made of aluminum or aluminum alloy, Si: 15% to 60% is contained, and the balance is not exceeded.
Brazing is performed using a hypereutectic Al-Si alloy powder brazing filler metal whose part is made of Al . A method for manufacturing a heat exchanger according to a third aspect of the present invention includes : Si: 15
Over eutectic Al containing 60% to 60% and the balance being Al
-Si-based alloy powder brazing material is attached, a tube is incorporated in the header portion, and the brazing material is heated to bond the tube and the header portion. First
The method for manufacturing a heat exchanger as fourth invention, in the second or third invention, the brazing material, characterized by comprising a mixture of Al-Si alloy powder and flux.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The heat exchanger of the present invention can be used in various applications such as for automobiles, and the application is not particularly limited as the present invention. Further, even in its 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.

The hypereutectic Al-Si alloy brazing material 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,
Needless to say, it may contain only Si and the balance consisting of impurities and Al. Although the Si content which becomes the eutectic point varies depending on the other added components, it is usually around 12% by weight, and in the present invention, the range of 13% to 60% is the desirable range of the Si content.

Here, if the Si content is 15 % or less, the brazing material becomes a eutectic or hypoeutectic alloy, the effect of melting the base material is not sufficiently obtained, and the effect of reducing the brazing material amount is obtained. Since it is small, the lower limit is exceeded by 15%. On the other hand, if the Si content exceeds 60%, the corrosion of the base material becomes excessive and problems such as strength reduction occur, and the melting point of the brazing material is 1150 ° C.
As described above, since it becomes difficult to melt the powdered brazing material at the time of manufacture, the Si content is set to 15 to 60 wt% . For the same reason, it is more desirable to set the lower limit to 20% and the upper limit to 30%. In these desirable ranges, appropriate melting to the base material occurs, so that it becomes possible to effectively reduce the amount of brazing material while maintaining good brazing property.

The Al-Si alloy whose components are determined from the above viewpoint can be pulverized by a conventional method and adjusted to an appropriate particle size (for example, maximum particle size 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. Fluoride, chloride flux or the like can be used as the above flux, but the type is not particularly limited in the present invention.

When the powdered brazing material is attached to the joint, various solvents and binders can be mixed to facilitate the attachment. As the solvent, water, alcohols (particularly, aliphatic alcohol having 1 to 8 carbon atoms) and the like can be used. Further, as the binder, any binder may be used as long as it can fix the powder satisfactorily without deteriorating the characteristics of the joint portion, and examples thereof include a water-soluble polymer compound having a carboxyl group, an acrylic resin, and a methacrylic resin. . The above-mentioned alloy powder is appropriately mixed and attached to the bonding material. The method is not particularly limited in the present invention, and 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 portion 1 and the powdered brazing filler metal is provided so as to surround the portion to be joined 4 of the tube 2 in the header portion 1. The material 5 is attached, and the radiation fins 3 are arranged on these as shown in FIG. 3 to obtain a heat exchanger assembly. After the powdered brazing filler metal 5 is adhered, the brazing filler metal is melted by heating it at a proper temperature in a proper atmosphere. The heating temperature at this time is 580 to 620 ° C.
Is desirable. Below 580 ° C, partial melting of the brazing material and the base metal does not proceed, making good brazing difficult, while at 620 ° C
Above the above range, the above temperature range is desirable because of significant corrosion. In the brazing material of the hypereutectic alloy used in the present invention, since Si is excessive, the Si diffuses and flows into the base material at the time of brazing, lowers the melting point of the base material and partially melts (erodes) it. . A part of the melted base material flows together with the applied powdered brazing material, and as shown in FIG. 2, they are fused to fill the gap between the members 1 and 2 and form a fillet to form the joint portion 6. Form. That is, a part of the base metal also acts as a brazing filler metal and complements the brazing filler metal amount necessary for joining, so that the amount of the powder brazing filler metal applied (required) can be reduced without impairing the brazing property. As a result, it is possible to reduce the cost by reducing the amount of the brazing powder used and the number of times of coating. Further, since the thickness of the brazing filler metal can be reduced, the brazing filler metal is less likely to fall off when the heat exchanger is assembled, the handling is facilitated and the working efficiency is improved.

It is also possible to use pure Si powder instead of the present brazing filler metal. However, when pure Si powder is used, the depth of the base metal is increased before the fillet is formed by eroding a part of the base metal. Corrosion in the direction is significant, and there is a part where the base metal is extremely thin, so through-holes easily occur due to corrosion, and the strength of the joining member decreases, causing problems in corrosion resistance and strength. Therefore, it is difficult to use. Therefore, it is necessary to avoid an Al-Si alloy having an excessive amount of Si for the same reason as above. Here, considering the allowable melting amount of the base material, the melting depth in the base material is less than 0.5 mm from the viewpoint of avoiding a decrease in strength and a decrease in corrosion resistance, although it depends on the plate thickness of the base material and the like. Is desirable. In the case of brazing with the powder brazing material of the present invention, a part of the base material becomes brazing and the base material plate thickness after brazing decreases, so a member having a relatively large plate thickness (for example, plate thickness 0.
Suitable for brazing to 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 using the following test pieces was conducted. That is, as shown in Table 1, aluminum alloy powders having different Si contents (maximum particle size 7
5 μm), a fluoride flux as a flux, and an acrylic resin as a binder were prepared, and these were mixed at a weight ratio of 10: 1: 1 to prepare a powder brazing material. As a comparative example, pure Si was also prepared as a powder brazing material.

Using the above powdered brazing material, an inverted T-shaped gap filling property test shown in FIG. 5 was conducted while changing the coating amount. Specifically, the JIS A3003 alloy is placed horizontally as the mating material 10, the JIS A3003 alloy is also used as the base material 11, and the powdered brazing material is applied to both surfaces by the flow coating method. And a rod-shaped spacer 12 is 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 to perform brazing using a flux in an inert atmosphere, the brazing material melted and a brazing portion (joint portion) 14 was formed in the small gap 13.
The brazing portion 14 was formed by melting the powder brazing material, the base material 11 and a part of 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 brazing material as the above is applied to the heat exchanger of the actual machine composed of JIS A3003 alloy for both the header part and the tube, and the brazing test is performed under the same conditions as the above. The joint state between the tube and the tube was observed. As a result, it was judged that there was no leakage at the joint and that brazing was good, and that there was leakage was poor brazing, and these results are also shown in Table 1.

[0015]

[Table 1]

As apparent from Table, the test piece of the brazing material Si content is 15 wt% Yue, small coating amount, and good brazing properties (gap filling property) is obtained at the number of applications,
The amount of dissolved base metal (maximum erosion depth) is also obtained appropriately.
Particularly, 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, if the Si content exceeds 60 wt% or pure S
At i, the maximum erosion depth is deep, and it is shown that the base metal is excessively eroded.

[0017]

As described above, according to the heat exchanger of the present invention, the joint portion between the header portion and the tube is formed by fusing the hypereutectic Al-Si alloy braze and the base material. Therefore, the amount of the brazing material used can be relatively reduced, and the joint portion is brazed securely and firmly. The wax, by mass%, Si: 15 one containing Yue 60%
As a result , excessive melting of the base material is prevented and the amount of the base material melted becomes appropriate, so that good brazing properties can be obtained without inviting a decrease in strength and a decrease in corrosion resistance due to the melting of the base material. it can.

Further, according to the method for manufacturing a heat exchanger of the present invention, when a tube is joined to a header portion made of aluminum or aluminum alloy, 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 brazing material amount much smaller than that of the conventionally known brazing material. Therefore, the amount of powder brazing material used and the number of times of application can be reduced, and the manufacturing cost can be greatly reduced without impairing the brazing property. At the time of the above production, the tube-to-be-joined portion is adhered with a hypereutectic Al-Si alloy powder brazing material, the tube is incorporated into the header portion, and the brazing material is heated to form 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-mentioned action is further ensured. Also,
If a brazing material made of a mixture of Al-Si alloy powder and flux is used, the flux applying step in the brazing step can be omitted, and the surface oxide film of the alloy powder is effective during brazing. To facilitate good brazing.

[Brief description of drawings]

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

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

FIG. 3 is a perspective view of the heat exchanger during assembly or production.

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

FIG. 5 is a perspective view showing an assembled state of a test material in a brazing test in an example 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]

1 header 2 tubes 3 radiating fins 4 joint planned part 5 brazing powder 6 joints 10 Counterpart material 11 Base material 13 small gap 14 Brazing part

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-6-200344 (JP, A) JP-A-7-314177 (JP, A) JP-A-5-305492 (JP, A) JP-A-57- 1590 (JP, A) JP 58-93852 (JP, A) JP 6-58214 (JP, A) JP 6-254695 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 35/28 B23K 1/00-1/19

Claims (4)

(57) [Claims] 1. The joint between the aluminum or aluminum alloy header portion and the tube is made of Si: 15 to 6
Hypereutectic Al-Si containing 0% and the balance Al
A heat exchanger having excellent brazing property, which is formed by fusing a base alloy powder brazing material and a base material. 2. When joining a tube to a header part made of aluminum or aluminum alloy, Si: 15 or more
Hypereutectic Al-S containing 60% with the balance being Al
A method for manufacturing a heat exchanger, which comprises brazing using an i-based alloy powder brazing material. 3. Si: 15 over 6 at the tube joining scheduled portion of the header portion made of aluminum or aluminum alloy.
Hypereutectic Al-Si containing 0% and the balance Al
A method for manufacturing a heat exchanger, characterized in that a brazing alloy powder is attached, a tube is incorporated in the header, and the brazing material is heated to bond the tube and the header. 4. A brazing material according to claim, characterized by comprising a mixture of Al-Si alloy powder and a flux 2 or
Or the method for manufacturing a heat exchanger according to item 3 .