JP3246971B2 - Aluminum heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A heat exchanger made of aluminum according to the present invention is used as a radiator or a heater core for an automobile.

[0002]

2. Description of the Related Art As radiators and heater cores, heat exchangers made of aluminum or aluminum alloys (herein, these are referred to as "aluminum materials") are widely used. The aluminum heat exchanger has a core 1 as shown in FIG. This core part 1
A number of flat heat transfer tubes 2 and 2 and corrugated fins 3 and 3, each made of an aluminum plate, are alternately overlapped, and the side surfaces of the heat transfer tubes 2 and 2 and the corrugated fins 3 and 3 Are brazed together. The thickness dimension T of each of the heat transfer tubes 2 and 2 which is generally used is about 1.5 to 3.0 mm, the width dimension (the dimension in the front and back direction in FIG. 1) is about 15 to 45 mm, and the adjacent heat transfer tubes 2 and The pitch P of No. 2 is about 6 to 13 mm. The pitch p of the corrugated fins 3, 3 is usually about 1.0 to 5.0 mm.

Conventionally, a composite material having a three-layer structure in which a skin material 5 and a brazing material 6 are laminated (cladded) on both surfaces of a core material 4 has been used as a composite material for forming the heat transfer tubes 2, 2. Widely used. The skin material 5 functions as a sacrificial corrosion layer, has a lower potential than the core material 4, and prevents the core material 4 from being corroded by sacrificial corrosion when coming into contact with water. . In addition, the brazing material 6 has a lower melting point than the core material 4, and the edge portions of the core material 4 are brazed to each other to form a heat transfer tube,
Alternatively, it is used to braze the obtained heat transfer tubes and fins.

A typical composite material that has been generally used in the past is a JIS 3003 material (0.6% by weight or less of Si, 0.7% by weight or less of Fe,
(Including 0.05 to 0.20% by weight of Cu, 1.0 to 1.5% by weight of Mn, and 0.10% by weight or less of Zn, with the remainder being inevitable impurities and Al) And J as skin material 5
IS7072 material (total 0.7% by weight or less of Si and Fe
And 0.10% by weight or less of Cu and 0.10% by weight or less
Containing Mn, 0.10% by weight or less of Mg, and 0.8 to 1.3% by weight of Zn, with the remainder being inevitable impurities and Al)
JIS 4343 material (6.8 ~
8.2 wt% Si, 0.8 wt% or less Fe, 0.2 wt%
5% by weight or less of Cu, 0.10% by weight or less of Mn,
20% by weight or less of Zn, the remainder being unavoidable impurities and Al
).

The aluminum material constituting the corrugated fins 3, 3 is included in JIS 3003 material.
A material in which Zn is increased to 1.5% by weight is used. By increasing the Zn content in this way, the corrugated fins 3, 3
Is lower than the potential of the core material 4 of the composite material. As a result, the corrugated fins 3, 3 are sacrificed to corrode, thereby preventing the core material 4 from being corroded.

[0006]

The heat exchanger made of aluminum according to the present invention is a heat exchanger made of aluminum material constituting each of the heat transfer tubes 2 and 2 and the corrugated fins 3 while ensuring sufficient durability. The purpose is to reduce the thickness of the heat exchanger and to reduce the weight of the heat exchanger made of aluminum.

[0007] As described above, both sides of JIS3003
The conventional composite material for forming the heat transfer tube 2 obtained by laminating the IS7072 material and the JIS4343 material can obtain practically sufficient performance in terms of corrosion resistance, but the strength of the JIS3003 material is not necessarily sufficient. In order to ensure the strength of the heat transfer tube 2 obtained from the composite material, it is necessary to increase the thickness of the core material 4.

That is, when the above-mentioned conventional composite material is heated for brazing, Zn contained in the JIS7072 material constituting the skin material 5 and Si contained in the JIS4343 material constituting the brazing material 6 JIS3003 that constitutes the core material 4
The core material 4 is diffused into the material, thereby reducing the corrosion resistance and strength of the core material 4. Therefore, it is difficult to reduce the weight of the heat exchanger made of aluminum by reducing the thickness of the core 4.

On the other hand, Japanese Patent Application Laid-Open No. 4-193925 describes an invention relating to a composite material for a heat exchanger made of an aluminum material, in which the strength of the core material is not reduced by heating by brazing. The composite material described in this publication has a content of 0.1.
3 to 2.0% by weight of Mn and 0.25 to 0.8% by weight of Cu
And 0.2 to 1.0% by weight of Si, and 0.5% by weight or less
A core material containing Mg and the remainder being unavoidable impurities and Al,
1.2-2.5 wt% Mg and 0.2-0.8 wt%
A skin material containing Si and 0.5 to 2.0% by weight of Zn, the remainder being unavoidable impurities and Al, a skin material covering one surface of the core material that comes into contact with water, and a skin material containing Si and containing Al as a main component And a brazing material covering the other surface of the core material. It is also described in the above publication that the skin material contains one or more of In, Sn, and Ga, each of which is 0.2% by weight or less.

[0010] In the case of the composite material described in the above-mentioned publication having such a configuration, the strength of the core material does not decrease by heating, and the thickness of the core material can be reduced. The weight of the aluminum heat exchanger including the heat transfer tube as a constituent element can be reduced.

However, in the case of the composite material for heat exchangers made of aluminum described in the above publication, Mg contained in the skin material
Is relatively large, 1.2 to 2.5% by weight, so that when In is contained in this skin material, intergranular corrosion tends to occur. As a result, the sacrificial corrosion effect of the skin material deteriorates, and when the corrosion conditions become severe, corrosion reaching the core material easily occurs.

The heat exchanger made of aluminum of the present invention has been invented in view of the above situation.

[0013]

The heat exchanger made of aluminum according to the present invention is made of a plate made of aluminum, as shown in FIG. 1, similarly to the above-mentioned conventional heat exchanger made of aluminum. In addition, a core portion 1 is provided in which a number of flat heat transfer tubes 2 and 2 and corrugated fins 3 and 3 are alternately overlapped, and the side surfaces of each heat transfer tube 2 and 2 and the corrugated fins 3 and 3 are brazed to each other. .

In particular, the aluminum heat exchanger of the present invention has the following requirements (a) to (g). (A) The plate material constituting the heat transfer tubes 2, 2 is a core material 4, and a skin material 5 laminated on one surface of the core material 4 that contacts water.
And a brazing material 6 laminated on the other surface of the core material 4. (B) The core material 4 contains 0.8 to 1.5% by weight of Mn,
0.4-0.6 wt% Cu and 0.2-0.8 wt%
It contains Si and Mg in an amount of 0.05% by weight or more and less than 0.2% by weight, and the rest consists of unavoidable impurities and Al. (C) The skin material 5 is 0.8% by weight or more and 1.2% by weight.
Mg, less than 0.2-0.8% by weight of Si,
0.020% by weight of In, and the balance consists of unavoidable impurities and Al. (D) The brazing material 6 contains Si and Al as a main component. (E) The thickness of the entire plate material constituting each heat transfer tube 2 is 0.2 mm.
28 mm or less. (F) The strength of the plate material constituting each of the corrugated fins 3, 3 is 55 MPa or more. (G) Each of the heat transfer tubes 2 and 2 and each corrugated fin 3 and 3
Is performed in an inert gas atmosphere using a fluoride-based flux, and heated at 590 to 620 ° C. for 3 minutes.

[0015]

In the heat exchanger made of aluminum according to the present invention thus constructed, the strength of the core material 4 constituting the heat transfer tubes 2 and 2 of the heat exchanger is sufficient, and the heating during brazing is performed. There is no drop by. For this reason, the thickness of the core material 4 is reduced, the thickness of the plate material constituting each of the heat transfer tubes 2 and 2 is reduced to 0.28 mm or less, as compared with the conventional heat exchanger, and the weight of the aluminum heat exchanger can be reduced. Become. In addition, since the sacrificial corrosion effect of the skin material 5 is sufficient and the corrosion that reaches the core material 4 is hardly generated, the durability of the lightweight aluminum heat exchanger is also sufficient.

Mn, Cu, Si, Mg contained in the core material 4
The amount was determined within the above range for the following reason.

Mn makes the potential of the core material 4 noble,
Is added to improve the corrosion resistance of Mn.
Is less than 0.8% by weight. On the other hand, if the content of Mn exceeds 1.5% by weight, a coarse compound is generated, which hinders the production of the core material 4 by rolling. Therefore, the content of Mn is limited to the range of 0.8 to 1.5% by weight.

Further, Cu is added to make the potential of the core 4 sufficiently higher than the potential of the sacrificial corrosion layer and to improve the strength of the core 4. That is, Cu in the core material 4 diffuses toward the skin material 5 due to heating during brazing, and the core material 4 creates a noble and skin material 5 having a low temperature gradient, thereby improving the corrosion resistance of the core material 4. Let it. When the content of Cu is less than 0.4% by weight, the effect of improving the strength of the core material 4 is insufficient, and when the content exceeds 0.6% by weight, the melting point of the core material 4 is lowered. This causes the strength of the core material 4 to be significantly reduced during brazing, and also reduces the corrosion resistance. For this reason, the content of Cu should be 0.4 to
The range was limited to 0.6% by weight.

Si is contained to improve the strength of the core material 4, but if the content is less than 0.2% by weight, the effect of improving the strength is insufficient. On the other hand, if the content exceeds 0.8% by weight, the melting point of the core material 4 becomes too low, and a part of the core material 4 may be melted at the time of brazing. For this reason, the content of Si is limited to the range of 0.2 to 0.8% by weight.

Mg is added to improve the strength of the core material 4. When the content is less than 0.05% by weight, the effect of improving the strength is insufficient. On the other hand, when the content is 0.2% by weight or more, it reacts with the fluoride-based flux used at the time of brazing to deteriorate the brazing property. Therefore, the content of Mg is limited to a range of 0.05% by weight or more and less than 0.2% by weight.

The core material 4 may contain other elements such as Fe, Zr, Cr, and Ti as long as the above effects are not impaired.

The reason why the amounts of Mg, Si and In contained in the skin material 5 are set in the above-mentioned range is as follows.

Mg is contained to improve the strength of the skin material 5, but if the content is less than 0.8% by weight, the effect of improving the strength is insufficient. Conversely, when the content is 1.2% by weight or more, intergranular corrosion due to the Mg-In alloy occurs, and the effect as a sacrificial corrosion layer becomes insufficient. Therefore, the content of Mg is limited to a range of 0.8% by weight or more and less than 1.2% by weight.

Si is added to improve the strength of the skin material 5, but if the content is less than 0.2% by weight, the effect of improving the strength is insufficient. On the other hand, when the content exceeds 0.8% by weight, the melting point of the skin material 5 becomes too low, and there is a possibility that a part of the skin material 5 is melted during brazing. For this reason, the content of Si is limited to the range of 0.2 to 0.8% by weight.

In is contained in order to lower (make base) the potential of the skin material 5 and to make the skin material 5 function as a sacrificial corrosion layer, but when the content is less than 0.010% by weight, Lumber 4
And the sacrificial corrosion effect is insufficient. Conversely, if the content exceeds 0.020% by weight, the core material 4
Is too large, the corrosion progress rate of the skin material 5 becomes too high, and the durability of the skin material 5 is insufficient. For this reason, the In content was limited to the range of 0.010 to 0.020% by weight.

The reason why the thickness of the entire plate material constituting the heat transfer tubes 2 and 2 is set to 0.28 mm or less is that if the thickness exceeds 0.28 mm, the conventional product described above has sufficient strength and practically sufficient strength. This is because it is not possible to achieve sufficient weight reduction in exchange for durability.

The strength of the plate material constituting each of the corrugated fins 3, 3 is set to 55 MPa or more because the corrugated fins 3, 3 sufficiently secure the force for suppressing the outer surfaces of the heat transfer tubes 2, 2. This is to reduce the deformation of the heat transfer tubes 2 and 2 side walls and prevent the side walls from being damaged. That is, when the pressure of the liquid in the flat heat transfer tubes 2 and 2 rises, a force for pushing the side wall of each heat transfer tube 2 and 2 outward acts, and when the pressure decreases, this force disappears. Therefore, if the outer surfaces of the heat transfer tubes 2 and 2 are not suppressed, the side wall may bulge outward or return to the original position as the operation and stop of the aluminum heat exchanger are repeated. Repetition of elastic deformation.

If such elastic deformation is allowed as it is,
With the use over a long period of time, the heat transfer tubes 2 and 2 tend to crack. In the case of an aluminum heat exchanger having a core 1 as shown in FIG.
By suppressing the outer surfaces of the heat transfer tubes 2 and 2 by 3, the elastic deformation is prevented, and the generation of cracks in the side walls is prevented. In order to surely obtain the effect of preventing the heat transfer tubes 2 and 2 from being cracked by the corrugated fins 3 and 3, the compressive strength of each of the corrugated fins 3 and 3 must be at least a certain level.

If the compressive strength is increased by increasing the thickness of the plate material constituting the corrugated fins 3 or reducing the pitch p, the heat transfer tubes 2 can be made thinner. Even if the thickness of the corrugated fins 3 or 3 is increased or the pitch p is made small in order to increase the compressive strength, the weight of the corrugated fins 3 and 3 themselves increases, and the heat generated by the aluminum material is increased. Not only cannot the weight of the entire exchanger be reduced, but also the ventilation resistance of the core part 1 is increased, and the performance of the heat exchanger is reduced. The above-mentioned limit value of the proof stress of 55 MPa is determined from such a viewpoint. That is, if the improvement of the present invention is applied to each of the heat transfer tubes 2 and 2 while ensuring the proof stress of the corrugated fins 3 and 55 MPa or more, the plate material constituting the corrugated fins 3 and 3 can be made thicker or the pitch p can be reduced. It is possible to obtain a lightweight, high-performance aluminum heat exchanger while maintaining sufficient durability without reducing the size.

Further, the brazing of the heat transfer tubes 2 and 2 and the corrugated fins 3 and 3 is performed in an inert gas atmosphere using a fluoride-based flux, and heating is performed at 590 to 620 ° C. for 3 minutes. This eliminates the need to clean the flux residue after brazing, and also ensures that the composition of the aluminum material that makes up each member during brazing is not significantly changed, and that a reliable brazing operation can be performed. is there.

[0031]

Next, an experiment performed by the present inventors will be described. In the first experiment, the brazing properties, tensile strength, and corrosion resistance of the aluminum plate material for forming the heat transfer tubes 2 and 2 were tested. In this first experiment, as the core material 4,
10 having a composition as shown in No. 1 to 10 of Table 1
The second kind of aluminum alloy is used as the skin material 2
Seven types of aluminum alloys having compositions as shown in Tables No. AG were used. Of the 10 types of aluminum alloys shown in Table 1, those of Nos. 1 to 3 belong to the present invention, and Nos. 4 to 10 are aluminum alloys prepared for comparison. Of the seven types of aluminum alloys shown in Table 2, those of NO. AB belong to the present invention, and NO. CG are aluminum alloys prepared for comparison. The column of Al in Tables 1 and 2 contains a small amount of unavoidable impurities in addition to most of Al.

The total of 17 types of aluminum alloys shown in Tables 1 and 2 are provided on one side of the aluminum alloy for the core material shown in Table 1 and the aluminum alloy for the skin material shown in Table 2 Is coated with a thickness of 0.10 mm, and the other surface of the aluminum alloy for the core material is further coated with JIS brazing material.
4343 materials were coated to give a total of 18 as shown in Table 3.
Specimens of various types of aluminum heat exchanger composites were prepared.

When performing the brazing test, a corrugated fin was abutted against the other surface of each test piece, and the corrugated fin and each test piece were brazed. This corrugated fin is made of an aluminum alloy containing 1.0% by weight of Mn and 1.5% by weight of Zn, the remainder being Al and unavoidable impurities, and made of a plate material having a thickness of 0.08 mm.

The heating conditions for brazing each test piece and the above corrugated fin were 590 to 62 in a nitrogen atmosphere.
0 ° C., 3 minutes. The flux used was Nocolok flux (a eutectic flux of K ₃ AlF ₆ and KAlF ₄ , a trade name of a fluoride-based flux widely used for brazing aluminum alloys). The quality of brazing is judged by the adhesive ratio (100 × fillet length of brazing material / length of contact between test piece and corrugated fin). If the adhesive ratio is 95% or more, good brazing characteristics ( ○)
When it was less than 95%, it was regarded as poor brazing property (x).

The measurement of the tensile strength and the corrosion test are as follows.
Corrugated fins were not brazed to the test piece, and the test piece was used as it was. However, prior to measurement and test, heating was performed under the same conditions as for brazing. The result of the tensile test was 16
A value of 0 MPa or more was regarded as good.

Further, in the corrosion test, chlorine ion (Cl ⁻ ) was 195 ppm, sulfate ion (SO ₄ ²⁻ ) was 60 ppm, copper ion (Cu ²⁺ ) was 1 ppm, and ferric ion (Fe ³⁺ ) was 30 ppm.
The test pieces were immersed for 8 hours in a circulating corrosive solution heated to 88 ° C. at 30 l / min.
The operation of leaving for a time was performed for 2 weeks (a total of 14 cycles). In determining the test results, it was determined that the maximum pitting depth was good if the maximum pitting depth was 0.1 mm or less, which is the thickness of the sacrificial corrosion layer.

As a result of each of the above tests and measurements, the tensile strength of the aluminum plate constituting the aluminum heat exchanger of the present invention was 160 MPa or more in any case, which was sufficient for manufacturing the heat exchanger. High strength.
Also, the maximum pitting depth is 0.07 mm, which is smaller than the thickness of the sacrificial corrosion layer even at the deepest,
Excellent results were obtained.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

Next, in the second experiment, five combinations as shown in Table 4 below were prepared in order to examine the effect of the strength of the corrugated fins 3, 3 on the durability of the heat transfer tubes 2, 2. did.

[0042]

[Table 4]

The heat transfer tubes 2 and 2 and the corrugated fins 3 made of the aluminum material shown in Table 4 were
As shown in FIG. 1, a work of releasing the pressure after applying a pressure of 1 kg / cm ² to each of the heat transfer tubes 2 and 2 is performed by heating to 120 ° C. The durability of the heat exchanger made of aluminum was determined based on whether or not cracks were generated in the heat transfer tubes 2 and 2 by 600,000 repetitions.

In order to make the conditions other than those shown in Table 4 the same, the thickness of the plate material constituting the heat transfer tubes 2 is 0.25 mm.
And a skin material 5 and a brazing material 6 (JIS 434)
3) were laminated at a cladding ratio of 10% (the ratio of the thickness of the skin material 5 or the brazing material 6 to the total plate thickness). The thickness T of each of the heat transfer tubes 2, 2 is 2 mm, the width is 27 mm, the pitch P of the heat transfer tubes 2, 2 is 10 mm, and the thickness of the plate material constituting the corrugated fins 3, 3 is 0.08 mm. The pitch p of the corrugated fins 3 was 3 mm. or,
The brazing of the heat transfer tubes 2 and 2 to the corrugated fins 3 and 3 was performed by heating both members 2 and 3 at 590 to 620 ° C. for 3 minutes in a nitrogen atmosphere. The used flux was the Nocolok flux described above.

When the above-mentioned repetition test was carried out on the five kinds of samples shown in Table 4, the proof stress of the aluminum alloy plates constituting the corrugated fins 3, 3 was 5%.
No cracks were generated in the heat transfer tubes 2 and 2 until the completion of the repetition of 600,000 times in each of the samples of NO. On the other hand, the proof stress of the plate material is 41MP
As for the sample No. 5 which was a, cracks occurred in the heat transfer tubes 2 and 2 after approximately 500,000 repetitions.

Next, a third experiment conducted to confirm the effect of the present invention on the thinning of the heat transfer tubes 2 and 2 and the corrugated fins 3 and 3 will be described. In the third experiment, a combination of two kinds of aluminum materials as shown in Table 5 below was used as the core material 4 and the skin material 5 of the plate materials constituting the heat transfer tubes 2 and 2, and the corrugated fins 3 and 3 were also used. As the aluminum material constituting the aluminum alloy, 2 as shown in the following Table 6
Each type of aluminum material was prepared.

[0047]

[Table 5]

[0048]

[Table 6]

A core portion 1 as shown in FIG. 1 was produced by appropriately combining a plurality of types of plate materials made of aluminum materials shown in Tables 5 and 6 and having various thicknesses. Then, an endurance test was performed on the heat transfer tubes 2 and 2 of each core portion 1 in which pressurization of 1 kg / cm ² and release thereof were performed once, and after repeating this test 600,000 times, whether or not cracks occurred was determined. The durability was determined. The conditions other than those described in Tables 5 and 6, such as the type of brazing material used, dimensions of each part, and brazing conditions, were the same as those in the first and second experiments. The results of this third experiment are shown in Table 7 below and in FIG.

[0050]

[Table 7]

In Table 7, "1 + A" means the alloy No. 1 in Table 5 belonging to the present invention in terms of composition and the alloy A in Table 6 also belonging to the present invention in terms of proof stress. The combination "2 + B" refers to the combination of the alloy No. 2 in Table 5 which deviates from the present invention in terms of composition and the alloy B in Table 6 which also deviates from the present invention in terms of proof stress. Things are represented respectively.

In Table 7 and FIG. 2, ◎ indicates that aluminum materials belonging to the present invention were combined and passed the above durability test, and Δ indicates that aluminum materials belonging to the present invention were combined. However, those that failed the endurance test because the plate thickness was too small
Indicates that aluminum materials deviating from the present invention are combined, but those that passed the above-mentioned durability test because of a large plate thickness, and x indicates that aluminum materials deviating from the present invention are combined and that the above-mentioned durability test was failed. Are represented respectively.

The solid line a in FIG. 2 indicates that when the alloy No. 1 in Table 5 and the alloy A in Table 6 were combined (1 + A),
The relationship (lower limit value) between the thickness of the heat transfer tube and the thickness of the corrugated fin that can pass the above-mentioned durability test, and the broken line b shows the case where the alloy No. 2 in Table 5 and the alloy B in Table 6 are combined ( 2 + B) shows the relationship between the thickness of the heat transfer tube and the thickness of the corrugated fin that can pass the durability test, respectively.

As is apparent from Table 7 and FIG. 2, according to the present invention, when the durability is the same, the heat transfer tubes 2, 2 and the corrugated fins 3, 3,
Thickness can be reduced.

[0055]

As described above, the heat exchanger made of aluminum according to the present invention is lightweight and has sufficient durability because it can be made thin while maintaining strength. You can get a bowl.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view of an aluminum heat exchanger to which the present invention is applied.

FIG. 2 is a diagram showing the effect of the material of the aluminum material forming the heat transfer tube and the proof stress of the aluminum material forming the corrugated fin on the respective thicknesses.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core part 2 Heat transfer tube 3 Corrugated fin 4 Core material 5 Skin material 6 Brazing material

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-193926 (JP, A) JP-A-5-230576 (JP, A) JP-A-53-96557 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C22C 21/00-21/18

Claims (1)

(57) [Claims] 1. A core portion comprising a number of flat heat transfer tubes and corrugated fins, each of which is made of an aluminum plate material, alternately overlapped, and a side surface of each heat transfer tube and a corrugated fin are brazed to each other. Aluminum heat exchanger having the following requirements (a) to (g). (A) The plate material constituting the heat transfer tube includes a core material, a skin material laminated on one surface of the core material that comes into contact with water, and a brazing material laminated on the other surface of the core material. (B) The core material contains 0.8 to 1.5% by weight of Mn and 0.1% by weight.
4 to 0.6% by weight of Cu and 0.2 to 0.8% by weight of Si
And 0.05% by weight or more and less than 0.2% by weight of Mg, with the balance being unavoidable impurities and Al. (C) The skin material is at least 0.8% by weight and less than 1.2% by weight of Mg, 0.2 to 0.8% by weight of Si,
Containing 0.020% by weight of In and the remainder being inevitable impurities
Consists of Al. (D) The brazing material contains Si and contains Al as a main component. (E) The thickness of the entire plate constituting each heat transfer tube is 0.28 mm
It is as follows. (F) The strength of the plate material constituting each of the corrugated fins is 55 MPa or more. (G) Brazing of each heat transfer tube and each corrugated fin
This is performed in an inert gas atmosphere using a fluoride-based flux, and heated at 590 to 620 ° C. for 3 minutes.