JPH10175062A - Heat exchanger excellent in brazeability and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an using quantity of a brazing filter metal by using a hyper-eutectic Al, Si, Zn 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, Zn 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, a 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. For the above problems,
According to the study of the present inventors, when a hypereutectic Al-Si alloy powder brazing material is used, the base material erodes (melts) during brazing.
It has been found that a part of the eroded base material acts as a braze together with the applied powder brazing material, so that the amount of brazing powder used and the number of times of application can be reduced while maintaining good brazing properties. doing. However, since this brazing material is an Al—Si (hypereutectic) alloy,
There is a problem that the corrosion resistance of the joints after brazing and the application area of the powdered brazing material is reduced due to local corrosion and pitting corrosion type due to the cathode of the crystallized material. The problem becomes even more pronounced.

[0004] The present invention has been made in view of the above circumstances, and can be satisfactorily brazed by using a small amount of brazing material. It is an object of the present invention to provide a heat exchanger in which the temperature is well maintained and a method for manufacturing the heat exchanger.

[0005]

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. But, in weight%, Si: over 13 ~
Hypereutectic Al-S containing 60% Zn: 5-30%
It is characterized by being formed by fusing an i-Zn-based alloy braze with a base material.

The method of manufacturing a heat exchanger according to the second invention is characterized in that when a tube is joined to a header portion made of aluminum or an aluminum alloy, Si: over 13 to 60% by weight, Z:
It is characterized by brazing using a hypereutectic Al-Si-Zn-based alloy powder brazing material containing n: 5 to 30%.
The method of manufacturing a heat exchanger according to a third aspect of the present invention is the method of manufacturing a heat exchanger, wherein the weight ratio of Si: 13% to 60% and Zn: 5% to 30% is added to the tube joining portion of the aluminum or aluminum alloy header.
A hypereutectic Al-Si-Zn-based alloy powder brazing material containing is attached, a tube is incorporated in the header portion, and the brazing material is heated to join the tube and the header portion. . The method for manufacturing a heat exchanger according to a fourth aspect is the method according to the second or third aspect, wherein the brazing material is
It is characterized by comprising a mixture of Al-Si-Zn alloy powder and flux.

[0007]

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.

The alloy used in the present invention is an Al alloy whose main component is Si: over 13 to 60% and Zn: 5 to 30%, and contains a small amount of additional elements in addition to Si and Zn. There may be. Naturally, it may contain only Si and Zn, and the balance may be made of impurities and Al. The above alloy becomes a hypereutectic alloy when the Si content exceeds 13%, and an effect of melting (eroding) the base material can be obtained. That is, when the Si content is 13% or less, the brazing material becomes an 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 small. It is desirable to exceed 13%. On the other hand, when the Si content exceeds 60%, erosion in the depth direction of the base material is remarkable, and extremely thin portions of the base material are formed, which causes a reduction in the strength of the joining member and generation of through holes due to corrosion. This causes problems in strength and corrosion resistance. In the case of a brazing filler metal having an Si content exceeding 60%, the melting point is 1150 ° C. or higher, and it is difficult to dissolve the powder brazing filler metal during fabrication. For these reasons, the Si content is over 13
60 wt% 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.

[0009] Further, by setting the Zn content to 5 to 30 wt%, a Zn diffusion layer having a Zn concentration gradient from the surface of the member to a deep portion is formed in the joint portion or the portion where the powder brazing material is applied after brazing. With this Zn diffusion layer, the form of corrosion becomes planar, corrosion in the depth direction can be prevented, and corrosion resistance can be improved. Here, if the Zn content is less than 5 wt%, a Zn diffusion layer cannot be formed, and sufficient corrosion resistance cannot be obtained. On the other hand, if the Zn content exceeds 30%, Z
Since n is remarkably oxidized to zinc oxide, no more solid solution is formed in the brazing filler metal. Also, the corrosion resistance is deteriorated. Therefore, the Zn content is set to 5 to 30%. In addition,
For the same reason, it is desirable that the lower limit of the Zn content is 8% and the upper limit is 25%, and the lower limit is 10% and the upper limit is 20%.
% Is more desirable.

[0010] Al-Si-Z whose components are determined from the above viewpoint
The n-based alloy can be pulverized 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 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.

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 above-mentioned powdered brazing material surrounds the periphery of the joining portion 4 of the tube 2 in the header portion 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. On the other hand, Zn contained in the brazing material forms a Zn diffusion layer in the brazed portion, promotes surface corrosion,
Prevent local corrosion and pitting corrosion due to crystallized substances, and as a result, improve corrosion resistance.

In the case of brazing with the powdered brazing material of the present invention, a part of the base material is brazed and the thickness of the base material after brazing is reduced. Although it depends on the thickness of the material and the like, the melting depth of the base material is 0.5
Desirably less than mm. From the above points, it is suitable for brazing to a member having a relatively large thickness (for example, a thickness of 0.5 mm or more).

[0014]

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 (maximum particle size: 75 μm) with different amounts of Si and Zn was prepared, a fluoride-based flux was prepared as a flux, and an acrylic resin was prepared as a binder. A powdered brazing material was prepared by mixing at a weight ratio of 10: 1: 1. Further, as a comparative example, an Al-Si based alloy or an Al-Si-Zn based alloy powder brazing material outside the scope of the present invention was prepared.

An inverse T-shaped gap filling test shown in FIG. 5 was carried out using the powdered brazing material 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 to perform Nocoloc brazing, 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
The powder brazing material and a part of the base material 11 and the counterpart material 10 were formed by melting. 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 SWAAT test (period 20 days) was performed on the test piece after the above brazing under the conditions of a test cycle, spraying (50 ° C. × 30 min), wet (50 ° C. × 30 min) test solution artificial seawater and acetic acid, and the corrosion depth was measured. And the form of corrosion was investigated, and the results are shown in Table 2.
JIS A3003 for both header and tube
The same amount of the same brazing material as above is applied to the joint to be joined to the actual heat exchanger made of the alloy, and a brazing test is performed under the same conditions as above, and the joint between the header and the tube is observed. did. As a result, good brazing without leakage at the joint,
The presence of a leak was determined to be a brazing failure, and these results are also shown in Table 2.

[0016]

[Table 1]

[0017]

[Table 2]

As is clear from Table 2, the test pieces with a brazing filler metal Si content of 15 wt% or more have a small coating amount,
Good brazing properties (gap filling properties) are obtained with the number of applications, and the amount of base metal dissolved (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, when the Si content is 60 wt%
In the case of exceeding, the maximum erosion depth is deep, which indicates that the base material is excessively eroded. In addition, even if the above characteristics are obtained, if Zn is not contained at all or contains a small amount of Zn, pitting corrosion is observed and the corrosion is deeply advanced. On the other hand, those containing an appropriate amount of Zn have a remarkably shallow corrosion depth. Incidentally, those containing Zn in excess of more than 30% were deeply eroded in the form of planar corrosion. Therefore, only in the case of using the powdered brazing material containing an appropriate amount of Si and Zn according to the above example, it is possible to braze well without impairing corrosion resistance with a small amount of brazing material, and to obtain good bonding and corrosion resistance at the joint. It became clear that was obtained.

[0019]

As described above, according to the heat exchanger of the present invention, the joint between the header portion and the tube is reduced to the weight%.
Is formed by fusion of a hypereutectic Al-Si-Zn-based alloy braze containing Si: 13% to 60% and Zn: 5 to 30% with the base material. And the joining portion is securely and firmly brazed. In addition, the inclusion of Zn in the joint makes the form of the corrosion planar, so that the progress of the corrosion in the depth direction can be prevented.

Further, according to the heat exchanger manufacturing method of the present invention, when the tube is joined to the aluminum or aluminum alloy header portion, Si: 13 to 6% by weight is used.
Hypereutectic Al-Si containing 0%, Zn: 5-30%
Since the brazing is performed using the system alloy powder brazing material, a good brazing property at the joint between the header portion and the tube can be obtained with a much smaller brazing material amount 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. In addition, Zn
Is formed to suppress the occurrence of pitting corrosion. Therefore,
ADVANTAGE OF THE INVENTION According to the manufacturing method of this invention, the usage-amount (application amount) of powder brazing material can be reduced, without impairing brazing property, and the brazing product excellent in corrosion resistance can be obtained at low cost. It becomes possible.

Further, in the above-mentioned manufacturing, Si: 13% to 60% by weight and Zn: 5 to 30% by weight
%, A hypereutectic Al-Si alloy powder brazing material is attached, a tube is incorporated into the header portion, and the brazing material is heated to join the tube and the header portion. A part of the prepared base material is effectively and appropriately melted, and the above-mentioned action is further ensured. Further, if a brazing material composed of a mixture of an Al-Si-Zn alloy powder and a flux is used, the flux application step in the brazing step can be omitted, and the surface oxidation of the alloy powder during brazing can be omitted. The coating is effectively removed, making 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 (4)

[Claims] The joint between the aluminum or aluminum alloy header and the tube is made of Si: 1 by weight%.
Hypereutectic A containing 3 to 60%, Zn: 5 to 30%
A heat exchanger excellent in brazing properties, characterized by being formed by fusing an l-Si-Zn alloy braze with a base material. 2. When joining a tube to an aluminum or aluminum alloy header portion, the weight percentage of Si:
A method for producing a heat exchanger, comprising brazing using a hypereutectic Al-Si-Zn-based alloy powder brazing material containing 13 to 60% and Zn: 5 to 30%. 3. An aluminum or aluminum alloy header portion to be joined to a tube at a portion to be joined to a tube is made of Si:
Hypereutectic A containing 3 to 60%, Zn: 5 to 30%
A method of manufacturing a heat exchanger, comprising attaching a l-Si-Zn-based alloy powder brazing material, incorporating a tube into the header portion, and heating the brazing material to join the tube and the header portion. 4. The method for manufacturing a heat exchanger according to claim 2, wherein the brazing filler metal comprises a mixture of an Al—Si—Zn-based alloy powder and a flux.