JP2000061624A - Aluminum brazing method - Google Patents

Abstract

(57) [Abstract] [Purpose] Regarding the brazing method of aluminum for heat exchangers for various applications, it is necessary to tighten brazing between interposed objects such as corrugated fins (corrugated fins) and flat tube groups. The present invention provides an aluminum brazing method for suppressing buckling of the interposition and brazing effectively. [Structure] A flat tube group coated with a non-corrosive flux and a metal powder is disposed between a header plate or a header pipe, and an interposing member such as a corrugated fin is interposed between the flat tube group and tightened. In a method for producing a body such as a heat exchanger by brazing, the corrugated fin may contain Mn in an amount of 0.8 to 1.7 wt% and Mg in an amount of 0.3 to 0.8.
An aluminum material brazing method comprising an aluminum alloy containing wt%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing method for aluminum materials such as heat exchangers for automobile radiators and condensers using a non-corrosive flux and metal powder, such as corrugated fins. An attempt is made to provide an aluminum material brazing method capable of effectively brazing by suppressing buckling of an interposing material such as the fin when brazing an interposing material such as a flat tube group by tightening. It is a thing.

[0002]

2. Description of the Related Art As shown in FIGS. 1 and 2, a heat exchanger such as a radiator and a condenser for an automobile includes a group of flat tubes 2 made of aluminum, a header plate 3 or a header pipe 5.
Al-Mn- is disposed between the flat tubes 2 group and the reinforcing member 7.
A method of manufacturing a heat exchanger and the like has been announced after assembling with a Zn alloy corrugated fin 1 interposed and then applying non-corrosive flux and metal powder to the entire body and brazing it [A. B.
aldantoni, B. Janeway, D. Lauzon and R. Timsit: SA
E Int, Congr., Technical Paper Series 940502, (199
Four) 〕. Reference numeral 4 in FIG. 2 denotes a tank, which after brazing is caulked with the header plate 3 to form a heat exchanger.

Further, as described above, when brazing,
It is wasteful and uneconomical to apply the flux and metal powder to the entire heat exchanger, and since the fins have holes, the necessary brazing part, that is, the flat tube surface, contains metal powder. JP-A-8-112667 proposes to assemble and braze corrugated fins after applying a non-corrosive flux.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The flux flaking in 12667 was solved by using a binder such as a resin. For example, when a flux mixture of 30 wt% Si powder was applied at about 10 g / m ² , the thickness after drying was about 15 μm. If the number of flat tubes is 30 when melted by brazing, at least 15 μm × 2 (front and back) × 30 in the calculation
(Book) = 0.9 mm gap is generated, and there is a disadvantage that the fin and the flat tube do not come into contact with each other, and there are places where brazing cannot be performed.

When the flat tubes and the fins are tightened and brazed by a tightening jig after assembling to eliminate the above-mentioned disadvantages, the fin plate thickness is thin and the fin is small in width, which tends to be lighter in recent years. However, there is a drawback that the fins buckle. On the other hand, if the tightening force is reduced in order to prevent the buckling of the fins as described above, a part that is not brazed is generated between the fins and the flat tube, and in any case, there is a disadvantage that a preferable result cannot be obtained. There is.

[0006]

The present invention has been made through repeated studies on solving the problems of the prior art as described above. That is, when the present inventors have assembled the flat tube and the fins and then tightened and brazed them with an assembling jig, the amount of displacement until the fins buckled due to the tightening was determined to be positive with respect to the proof stress after brazing and heating. The present invention has been completed by discovering that there is a correlation, and that the higher the yield strength after brazing and heating is, the stronger the tightening force can be and the larger the displacement of the fin can be made. . In other words, the present invention is to apply a non-corrosive flux and metal powder to the surface of a flat tube by using a material having a high yield strength after brazing and heating, and tighten the fin and the flat tube to perform brazing. With this brazing method, the buckling of the fins is eliminated, and the brazing failure between the fins and the flat tubes is solved. An aluminum alloy containing Mg is a material with high yield strength.

More specifically, the present invention will be described in more detail. By using an Al-Mn-Mg alloy for the fin, a large displacement (deformation) until the fin buckles even if the tightening force is increased. Fig. 3 (a),
Explaining with (b), first, (a) as an alloy, Al
-1wt% Mn-0.5wt% Mg alloy plate material, as (b) alloy
An Al-1 wt% Mn alloy plate was prepared, and the relationship between the stress and the displacement (deformation amount) until the buckling of the plate occurred. FIG. 3a shows that the alloy plate (a) is used. Since it contains Mg and has a high proof stress, it can be seen that both stress and displacement until the buckling occurs can be made large. On the other hand, FIG. 3b shows that the alloy plate (b) is used, and since Mg is not contained, the yield strength is low, and both stress and displacement until buckling occur are low.

That is, the corrugated fin made of the alloy plate shown in FIG. 3 (a) is interposed between the flat tubes to apply stress (tightening force).
Is added and the displacement of the fin is set large,
Even if the flux on the surface of the flat tube melts at the brazing temperature and a gap is created between the fin and the flat tube, the displacement returns to its original state and the fin and the flat tube come into contact with or come close to each other, and the metal powder in the flux and the flat tube It is clear that the braze alloy formed by reaction with the aluminum of the tube will ensure a braze joint.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The composition of the corrugated fin in the present invention is mainly Mn and Mg, and is as follows. Mn: 0.8 to 1.7 wt% Mn is for imparting strength to the fins. If it is less than the lower limit, it is less effective, and if it exceeds the upper limit, stripnability is deteriorated. Mg: 0.3-0.8wt% Mg is added so that the fins can have a large displacement until they buckle due to tightening force. Below the lower limit, there is no remarkable effect, and the upper limit. If it exceeds, the brazing property will deteriorate.

The other elements are not particularly limited,
The inclusion of Fe is preferable because it can increase the displacement, but if it exceeds 1 wt%, rolling workability is deteriorated, which is not preferable. There is no problem as long as other elements are impurities specified in JIS 3000 series alloy. Ti and B are effective in preventing casting cracks during casting, Ti is 0.05% or less, and when B is used in combination, Ti is 0.0% or less.
5% or less, and B is preferably 0.01 wt% or less. In addition, Si is added Mg and fine Mg ₂ S by cooling during brazing.
Since it has the effect of forming precipitates and increasing the strength after brazing, it is preferable to positively add 1 wt% or less. If it exceeds 1 wt%, the melting point of the fin material is lowered and the fin material tends to soften at the brazing temperature, which is not preferable. When Zn is added, the potential of the fin becomes base, and Zn has a sacrificial corrosion action on the flat tube having a more noble potential.
Up to wt%, it is preferable to positively add. 5
If it exceeds wt%, the melting point of the fin material is lowered and the fin material is easily softened at the brazing temperature, which is not preferable.

The non-corrosive flux used in the present invention is LiF,
NaF, KF, CaF ₂ , AlF ₃ , SiF ₄ etc. fluoride powder mixture,
Alternatively, a powder obtained by melting these powders, or a complex compound of the above-mentioned fluoride, such as KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ ,
A single or mixture of K ₂ SiF ₆ or the like, or one obtained by melting these into powder, etc., and any of these fluoride-based fluxes have a corrosiveness to aluminum such as chloride. Absent. The average size of the powder is about 0.1 to 30 μm, preferably 1 on average.
10 to 10 μm.

As the metal powder which is melted as an alloy with an aluminum material to form a braze, there are zinc powder in addition to silicon powder, and Zn is contained, preferably 10 to 30% Zn.
There is a silicon-zinc alloy powder contained therein. Then, such a metal powder is mixed with the powder of the flux and applied to the surface of the flat tube. In this case, 30% or less of zinc powder or 20% or less of copper powder may be added and mixed and coated in addition to silicon powder. In particular, alloying silicon in advance has the disadvantage of increasing costs, and it is preferable to use a simple substance of metal as powder. Of these, silicon is particularly preferable because it hardly reacts with water when water is used as the medium of the slurry mixture with the flux powder. The average size of the metal powder is 0.5 to 50 μm, preferably 1 to 2 on average.
It is 0 μm.

The flux powder and the metal powder as described above are suspended in a dry powder or a volatile liquid such as water or alcohol to prepare a mixture slurry. The mixture is mixed in a weight ratio of about 0.5: 1 to 10: 1, and when the metal is silicon, it is preferably 1: 1 to 4: 1. The mixture ratio of the mixture and the volatile liquid when suspended in the volatile liquid may be appropriately selected depending on the type of the metal powder or the volatile liquid and the coating method, but the weight ratio is generally 0.1: 1 to 3: 1. It is a degree.

The method of applying the mixture of the flux powder and the metal powder to the flat tube is not particularly specified in the present invention. When the mixture is a dry powder, the electrostatic or air spray method is used, and when the mixture is a slurry, the spray or spray method is used. The dipping method can be applied and can be carried out efficiently. As the coating amount of the mixture,
It is about 3 to 50 g / m ^{2 with} respect to the tube area, and 10 to 30 g / m ² is preferable for a mixture of about 30% silicon powder.

As described above, the brazing of the heat exchanger obtained by applying the mixture of the flux powder and the metal powder on the surface of the flat tube and assembling and tightening the corrugated fins is the conventional non-corrosive flux braze. The conditions are similar to those of the Appendices. The brazing temperature when using silicon powder is 580 to 580.
At 620 ° C, the holding time is about 0 to 10 minutes.

The composition of the member such as the flat tube in the present invention is not particularly limited, but it is preferable to set Mg to 0.1 wt% or less because the brazing property does not decrease.
A member such as a corrugated fin, which is another member of the present invention, can effectively solve various problems caused by reducing the plate thickness of the fin and narrowing the fin width due to the tendency toward weight reduction. The corrugated fin has a fin thickness of 0.06 to 0.12 mm, a fin width of 14 to 24 mm, and a fin height of 6 to 12 mm.
The fin pitch of the corrugated fin (1/2 of one wavelength) is
When it is within the range of 0.8 to 1.2 mm, the effect can be properly exhibited.

[0017]

EXAMPLE A concrete example of the present invention will be described. Fin materials having the compositions shown in Table 1 below were prepared, and the fin materials of alloy numbers 1 to 5 were prepared by a conventional method to obtain a plate thickness of 0. A fin material of 0.07 mm-H14 was prepared, heated under a brazing temperature of 600 ° C. for 3 minutes under a brazing condition, and a tensile test was performed at room temperature to measure a 0.2% proof stress.
The results are shown in Table 2 below. In addition, Ti in Table 1 is Al-5
% Ti-1% B alloy was added.

[0018]

[Table 1]

Corrugated fins having the following shapes were separately manufactured from the fin material having the composition shown in Table 1 above. Fin width 21mm, fin height 8mm, fin pitch 1.
3mm (1/2 of 1 wavelength), radius of curvature of fin mountain is 0.60mm. Fin width 16mm, fin height 8mm, fin pitch 1.
0 mm (1/2 of 1 wavelength), radius of curvature of fin mountain 0.40 mm. Also, with this and corrugated fin,
(A) Brazing property evaluation test and (B) heat exchanger prototype test were conducted.

The non-corrosive flux used for brazing, the metal powder, the coating method, and the brazing conditions are as described above. Under the above conditions, the brazing is carried out at a flux / silicon powder weight ratio of 2: 1. The mixture prepared by suspending 100 g of the mixture in 400 g of water was spray-coated on the surface of the flat tube and dried by heating at 150 ° C. for 5 minutes, and the adhering state of the mixture in the test body after drying was visually observed. Upon observation, a uniform attachment state was confirmed.

The brazing test piece prepared as described above was heated to about 600 ° C. at a heating rate of 50 ° C./min in a nitrogen gas atmosphere and kept at that temperature condition for about 3 minutes to obtain a desired brazing test piece. The obtained brazing test pieces were subjected to the following brazing property evaluation test and heat exchanger trial test.

(A) Brazing property evaluation test. The test was performed using a fin having a shape having the composition shown in Table 1 above. That is, the fin length at this time was 60 mm, while the flat tube used was a JIS 1050 alloy extruded 12-hole flat tube having a width of 19 mm and a length of 80 mm, to which flux was applied at 10 g / m ² . As for the test body, five fins were prepared by sandwiching the two fins between the three flat tubes, and each was tightened with the same force using a jig. The brazing conditions were such that heating was held at 600 ° C. for 3 minutes in a nitrogen gas atmosphere as described above.

Evaluation method: The results of measuring the fillet length under the following conditions are shown in Table 2 described later. That is, as to the fillet length, as shown in FIG. 4, the flat tube cross section (center in the width direction) at the center of the test body was polished, and the shortest distance between the left and right fillets formed on both surfaces was measured. In FIG. 4, 1 is a corrugated fin, 2 is a flat tube, and 6 is a fillet.

[0024]

[Table 2]

(B) The heat exchanger prototype was tested using a fin having the shape of the test, and the fin length was 3
The flat tube used was a JIS 1050 alloy extruded 12-hole flat tube having a width of 16 mm and a length of 340 mm coated with flux at 10 g / m ² . The test body was composed of 31 rows of the fins and 30 of the flat tubes, and was composed of a header pipe and a reinforcing material, and the reinforcing material, the fins and the flat tubes were tightened with the same tightening force with a tightening jig. The brazing conditions were such that heating was held at 600 ° C. for 3 minutes in a nitrogen gas atmosphere as described above.

Evaluation method: The presence or absence of fin buckling and the presence or absence of fin separation were visually determined, and the results are as shown in Table 2. For sample No. 1, since the fins buckled during the above tightening, the tightening force was weakened in the retest (6
After the brazing, the fins did not buckle, but after brazing, the fins facing the reinforcing material were continuously separated from each other (see Fig. 5), and it was found that the tightening force could not be weakened. It was

According to the results of Table 2 as described above,
Examples of the present invention (Sample Nos. 2, 3 and 4) having high yield strength after brazing satisfying the conditions of the present invention have no fin buckling, a fillet length of the conventional example, and no fin separation.
It is clear that it is brazed well. On the other hand, in the conventional example (Sample No. 1) having a low yield strength after brazing that deviates from the conditions of the present invention, it is found that fin buckling occurs and fin separation occurs. Further, it is clear that the sample No. 5, which is a comparative example having a high Mg content, does not produce a brazing alloy in the brazing test A, and the brazing property is deteriorated.

[0028]

As described above, since the present invention uses the corrugated fin made of Al-Mn-Mg alloy having a high yield strength containing Mg, the flux containing the metal powder in the flat tube in advance is used. After the application of the fin, the fin is assembled, and even if the tightening force is increased, buckling does not occur, and preferable brazing with no fin separation can be accurately obtained, which is an industrially great invention. .

[Brief description of drawings]

FIG. 1 is a front view showing an example of a heat exchanger to which the present invention is applied.

FIG. 2 is a partially partially cutaway perspective view showing another example thereof.

FIG. 3 is a chart showing a comparison between buckling occurrence states of a conventional fin material and a fin material of the present invention.

FIG. 4 is an explanatory diagram of fillet length.

FIG. 5 is a plan view showing how the corrugated fins are attached to the flat tube.

[Explanation of symbols]

1 corrugated fin 2 Flat tube 3 header plate 4 tanks 5 header pipe 6 fillets 7 Reinforcement material

Continued front page    (72) Inventor Yusuke Ichikawa             1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture             Nippon Light Metal Co., Ltd. Group Technology Center             Within

Claims (4)

[Claims] 1. A flat tube group coated with a non-corrosive flux and metal powder is disposed between header plates or header pipes, and an interposing member such as a corrugated fin is interposed between the flat tube groups. In a method of manufacturing a body such as a heat exchanger by tightening and then brazing, the corrugated fin has Mn of 0.8 to 1.7 wt% and Mg of 0.3 to.
A brazing method for an aluminum material, which comprises an aluminum alloy containing 0.8 wt%. 2. The method for brazing an aluminum material according to claim 1, wherein the corrugated fin further contains Si in an amount of 1 wt% or less. 3. The method for brazing an aluminum material according to claim 1, wherein the corrugated fin further contains Zn in an amount of 5 wt% or less. 4. The corrugated fin has a plate thickness of 0.06 to
0.12mm, fin width 14-24mm, fin height 6-1
The aluminum material brazing method according to any one of claims 1 to 3, wherein the fin pitch of the corrugated fins is within a range of 0.8 to 1.2 mm when the corrugated fins are within a range of 2 mm.