JP4641267B2 - Low melting point brazing material for aluminum heat exchanger and method for producing aluminum heat exchanger - Google Patents

Description

  The present invention relates to a low melting point brazing material used for joining between a plurality of members when manufacturing an aluminum heat exchanger constituted by joining members made of a plurality of aluminum alloys, and aluminum heat exchange using the same The present invention relates to a method for manufacturing a container.

Aluminum heat exchangers for transporters such as automobiles and cooling aluminum heat exchangers used for electronic parts are usually manufactured by brazing and joining aluminum alloy parts such as fins and tubes using Al-Si brazing filler metal. is doing.
More specifically, since the heat exchanger made of aluminum alloy has a complicated structure, a brazing sheet clad with an Al-Si alloy brazing material is generally used as a part of the components of the assembly. -It is assembled by heating components up to a temperature of about 600 ° C above the melting point of the Si-based alloy brazing material, and joining the components together by in-furnace brazing such as Nocolok brazing and vacuum brazing. .

In recent years, there has been a demand for lower brazing temperature for the purpose of reducing energy consumption and enabling joining of high-strength aluminum alloy materials having a low melting point. For this reason, studies have been made on low temperature bonding using a Zn alloy brazing material having a melting point lower than that of the Al—Si based brazing material.
The Zn alloy brazing material cannot be clad by rolling because the melting point difference from the Al base material is very large. Therefore, in order to apply to mass production, a technique for supplying a Zn alloy brazing material to a material to be joined at a low cost is required.

  As a technique for supplying a Zn alloy-based brazing material to a material to be joined, hot dipping using ultrasonic waves and flux (Patent Document 1) has been proposed, but requires dedicated equipment and is expensive. Moreover, although plating by mechanical friction (Patent Document 2) has been proposed, the shape is limited and application to a complicated shape is difficult.

  As a method for solving these problems, a method of applying a mixture of brazing filler metal powder and flux powder (Patent Document 3) has been proposed. This method makes it possible to supply a brazing material even in a complicated shape. However, since the specific gravity of Zn is 2.65 times the specific gravity of Al, the weight ratio of the brazing material is significantly increased as compared with the case where a conventional Al-based brazing material is used. For this reason, it has been desired to develop a technique for reducing the amount of use as much as possible while attaining low-temperature treatment using a Zn-based brazing material.

JP-A-5-277787 JP-A-5-320855 JP 2005-111527 A

  The present invention has been made in view of such conventional problems, and can be used for an aluminum heat exchanger in which brazing can be performed at a low temperature and the amount of brazing material used can be reduced as compared with the conventional one. An object of the present invention is to provide a low melting point brazing material and a method for producing an aluminum heat exchanger using the same.

The first invention is a low melting point brazing material used for joining between the plurality of members when manufacturing an aluminum heat exchanger configured by joining a plurality of members made of an aluminum alloy,
A brazing filler metal component comprising zinc alloy particles having an average particle size of 20 μm or less;
A flux component composed of non-corrosive flux particles having an average particle size of 20 μm or less,
The low melting point brazing material for an aluminum heat exchanger, wherein the blending ratio of the brazing filler metal component and the flux component (the flux component weight / the brazing filler metal component weight) is 0.6 to 2.0. 1).

  The low melting point brazing material of the present invention is a brazing material used in producing the aluminum heat exchanger, and both the brazing material component and the flux component contained as the components have a particle size in the specific range. Limited to particles. Furthermore, the blending ratio of the brazing filler metal component and the flux component is limited to the specific range. By satisfying these requirements at the same time, the low melting point brazing material can realize reliable joining with a smaller amount of use than in the conventional case when it is employed in the manufacture of an aluminum heat exchanger.

  When the average particle size of at least one of the zinc alloy particles and the non-corrosive flux particles (hereinafter referred to as flux particles) exceeds 20 μm, unevenness in thickness is likely to occur when adhered to a component made of an aluminum alloy. There's a problem. Therefore, both the zinc alloy particles and the flux particles need to satisfy the requirement that the average particle size is 20 μm or less. Note that the lower limit of these average particle diameters is preferably 1 μm for the reason of an increase in production cost due to fine powdering.

  Moreover, by setting the blending ratio of the zinc alloy particles and the flux particles to 0.6 or more, a stable bonding strength can be obtained as compared with the case of less than that, and 2.0 or less. However, a more stable bonding strength can be obtained than in the case of more than that. Most preferably, it is good to set it as 1.0 vicinity which is a compounding ratio with which the peak of joining strength is obtained.

2nd invention is a manufacturing method of the aluminum heat exchanger comprised by joining the some member which consists of aluminum alloys,
By attaching a low melting point brazing material to at least one member of the plurality of members and heating to a brazing temperature that exceeds the melting point of the brazing material component contained in the low melting point brazing material, In brazing and joining, the low melting point brazing material of the first invention is used as the low melting point brazing material. (Aspect 4)

  The manufacturing method of the present invention performs brazing using the above-described excellent low melting point brazing material. Therefore, the amount of the low melting point brazing material used can be reduced as compared with the conventional one, and reliable brazing can be performed. Therefore, the Zn content remaining in the obtained aluminum heat exchanger can be kept low, and the weight can be reduced.

As the zinc alloy particles of the brazing filler metal component in the first invention, zinc or zinc alloy particles mainly composed of zinc can be applied. That is, the concept of the zinc alloy includes pure zinc and alloys of zinc and other metals.
For example, it is preferable that the zinc alloy particles are composed of Al: 2 to 6% by mass and the balance of Zn and inevitable impurities in mass% (Claim 2). In this case, the melting point with an Al content of 5% is the lowest at 382 ° C., and in the range of 2 to 6%, the flowability of the brazing material becomes very good during brazing.

  As the non-corrosive flux particles, various known particles can be applied as long as they are melted and activated in the melting temperature range of the brazing filler metal component. By activating the non-corrosive flux particles, brazing promoting effects such as removal of the aluminum oxide film and fluidization of the molten brazing material can be achieved.

The non-corrosive flux particles are composed of a mixed composition of CsF and AlF ₃ , and the mixing ratio CsF (mol%) / AlF ₃ (mol%) is preferably 1.0 to 1.2. 3). In the mixing ratio range of 1.0 to 1.2, the melting point of the flux is sufficiently low with respect to the brazing temperature, and the effect that the activity of the flux becomes very good is obtained.

For example, in the case of non-corrosive flux particles having a mixing ratio of 35/65, the melting activity start temperature is 420 ° C., and the melting activity temperature range is 420 ° C. to 480 ° C.
Here, the melting activation start temperature is a temperature at which melting of the flux component is started and the brazing promoting action is activated. The melt activation temperature range refers to a temperature range in which this melt active state is favorably maintained. If the temperature of the flux component exceeds the upper limit of the melting activation temperature range, the flux component is overheated, and flux vaporization increases rapidly, which is not preferable.
Therefore, in the combination of the zinc alloy particles as the brazing filler metal component and the non-corrosive flux particles as the flux component, at least the melting active temperature range of the flux component and the melting temperature of the brazing filler metal component overlap. is required.

  In the method for manufacturing an aluminum heat exchanger according to the second invention, as described above, the low melting point brazing material is adhered to at least one member among the plurality of members. For example, the low melting point brazing material is suspended in an organic solvent and the liquid is applied to a desired member. As a coating method, there are various known methods, for example, a spraying method, a brushing method, a roller method, and the like.

The heat treatment after the low melting point brazing material is adhered to the member is performed after evaporating the solvent and drying, for example, when the organic solvent is used as described above.
And it is preferable that the said brazing temperature is 450 degrees C or less ( Claim 5 ). That is, by adjusting the components of the low melting point brazing material so that it can be sufficiently brazed at a temperature of 450 ° C. or lower, and the actual brazing temperature is set to 450 ° C. or lower, the energy consumption is greatly reduced. Can be achieved.

Example 1
A low melting point brazing material for an aluminum heat exchanger and a method for manufacturing the aluminum heat exchanger according to an embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the low melting point brazing material of this example is formed between the plurality of members 10 to 13 when the aluminum heat exchanger 1 configured by joining a plurality of members 10 to 13 made of an aluminum alloy is manufactured. It is a low melting point brazing material used for joining.

  As shown in the figure, the aluminum heat exchanger 1 is a vehicle heat exchanger, and a tube 10 bent in a meandering shape having a refrigerant passage through which a high-pressure refrigerant flows and a parallel portion of the tubes 10 facing each other. And corrugated fins 11 inserted therebetween. The tube 10 employs a flat multi-hole tube formed by extruding an aluminum alloy material. The corrugated fin 11 is formed by bending a thin aluminum alloy plate into a wave shape. A refrigerant inlet pipe 12 is joined to one end of the tube 10 and a refrigerant outlet pipe 13 is joined to the other end. These refrigerant inlet pipe 12 and refrigerant outlet pipe 13 are also formed of an aluminum alloy material.

In this example, in manufacturing this aluminum heat exchanger 1, each of the above components 11 to 13 is prepared in advance, and an assembly in which all components are assembled so as to have the same arrangement as the finished product is manufactured. Then, an attaching step for attaching a low melting point brazing material is performed.
In this example, the low melting point brazing material contains a brazing filler metal component made of zinc alloy particles having an average particle size of 20 μm and a flux component made of non-corrosive flux particles having an average particle size of 20 μm. The compounding ratio of the component and the flux component (flux component weight / brazing material component weight) was 1.0. As the zinc alloy particles, Zn-5% Al was adopted, and as the non-corrosive flux particles, CsF (mol%) / AlF ₃ (mol%) = 35:65 was adopted.

  In the attaching step, a solution in which the low melting point brazing material having the above structure is suspended in an organic solvent such as alcohol is used. The concentration of this solution was appropriately adjusted to be suitable for spraying. And the said solution was made to adhere to the surface of said each components 10-13 in an assembly by spraying at room temperature using a sprayer.

Subsequently, the assembly was heated slightly above room temperature (about 60 ° C.) to evaporate the solvent of the solution containing the low melting point brazing material.
Next, a brazing step is performed in which the assembly is charged into a heating furnace and heated to a brazing temperature exceeding the melting point of the brazing filler metal component. The brazing step was performed under the conditions that the brazing temperature (heating temperature) was 450 ° C., the brazing time (heating time) was 1 minute, and the atmosphere in the heating furnace was an air atmosphere.

  As a result of the brazing process, the low melting point brazing material adhering to the surface of the assembly contributes to the joining between the parts 10 to 13, and the aluminum heat exchanger 1 having the configuration shown in FIG. 1 is obtained. It was. The bonding strength of each part was sufficient.

  Thus, in this example, the brazing process can be performed at a temperature as low as 460 ° C. using the low melting point brazing material. That is, the heating temperature can be significantly lowered as compared with a heating temperature of about 600 ° C. in a brazing method using an Al brazing material of a general aluminum heat exchanger. Therefore, it is possible to suppress the strength reduction of the members 10 to 13 of the aluminum heat exchanger 1 due to the thermal history, and it is possible to reduce the amount of energy used for heating.

  Further, the low melting point brazing material in this example was one whose average particle size was controlled to 20 μm as described above. Thereby, even if it reduces the usage-amount in the said adhesion process, a uniform adhesion state can be obtained. Therefore, it is possible to reduce the weight by reducing the amount of low melting point brazing material used.

(Example 2)
In this example, the composition of the low melting point brazing material used in Example 1 was changed, and a test was conducted on the bonding strength when the amount of adhesion was changed.
First, as shown in FIGS. 2 and 3, as the test pieces 21 and 22, an aluminum alloy plate having a material A3003, a thickness T = 5 mm, a width W = 20 mm, and a length L = 80 mm was prepared. Then, as shown in FIG. 2, a low melting point brazing material 5 suspended in an organic solvent was applied to a longitudinal end portion of one test piece 21 in a range of length S = 5 mm by a coating roller.

Next, after evaporating the organic solvent from the low melting point brazing material 5 applied to the test piece 21, as shown in FIG. 3, the end portions of the test piece 21 and the test piece 22 are sandwiched between the low melting point brazing material 5. Overlapping each other. The combined length L2 is 155 mm. And the brazing process which heats the test pieces 21 and 22 to the temperature of 450 degreeC in air | atmosphere for 10 minutes was implemented.
Next, shear strength measurement was performed by a tensile test in which both ends of the obtained joined body were pulled.

The low melting point brazing material includes a brazing filler metal component composed of Zn-5% Al particles having an average particle size of 20 μm or less, and CsF (mol%) / AlF ₃ (mol%) having an average particle size of 20 μm or less. = 35: 65 CsF—AlF ₃ non-corrosive flux particles were used as flux components. And the compounding ratio (flux component weight / brazing material component weight) of the brazing filler metal component and the flux component was changed in the range of 0.5 to 2.0. Moreover, the adhesion amount of the low melting-point brazing material 5 was changed in the range of 30 to 160 μm in terms of Zn.

The test results are shown in FIGS.
In FIG. 4, the horizontal axis represents the amount of low melting point brazing material (Zn equivalent thickness, μm), and the vertical axis represents shear strength (MPa). FIG. 5 shows the mixing ratio of the brazing filler metal component and the flux component (flux component weight / brazing filler component weight) on the horizontal axis and the shear strength (MPa) on the vertical axis.

  As can be seen from FIG. 4, when considering a preferable range of shear strength as about 30 MPa or more, the adhesion amount of the low melting point brazing material is preferably in the range of 60 to 150 μm in the Zn equivalent thickness (μm). I understand. Moreover, it turns out that 1.0 is the most preferable as said compounding ratio. On the other hand, when the blending ratio is reduced to 0.5, the shear strength may be slightly lower than 30 MPa when the adhesion amount is small. From this point, it can be seen that it is preferable to slightly increase the mixing ratio to about 0.6 or more than the mixing ratio of 0.5. It can also be seen that sufficient shear strength can be obtained even if the blending ratio is increased to 2.0.

As can be seen from FIG. 5, considering the preferable range of the shear strength as about 30 MPa or more, if the blending ratio is 1.0 or more, it is sufficient even if the adhesion amount is changed in the range of 30 to 160 μm. It can be seen that shear strength can be obtained. On the other hand, when the blending ratio is reduced to 0.5, the shear strength may be slightly lower than 30 MPa when the adhesion amount is 60 μm or less.
Considering the results of FIG. 4 and FIG. 5 as a whole, the blending ratio is not lowered to 0.5, but is within the range of 0.6 or more and 2.0 or less, and most preferably around 1.0. It is also preferable that the adhesion amount is in the range of 60 μm to 150 μm, and most preferably in the vicinity of 100 μm.

(Example 3)
In this example, a test was performed in which the zinc alloy particles and the flux particles in the low melting point brazing material used in Example 1 were changed in size and the coating thickness variation was evaluated.
In the test, as shown in FIG. 6, a solution in which the low melting point brazing material 5 is suspended in an organic solvent is applied on the reference plate 8, and the application variation is measured. The coating thickness (Zn equivalent thickness) was all targeted at 100 μm. The brazing material was applied by a method of applying with a coating roller. In addition, as shown in FIG. 6, the application variation was measured by a procedure of obtaining a difference A between the maximum value and the minimum value using a laser displacement type.

In addition, the particle diameters of the zinc alloy particles and the flux particles in the low melting point brazing material used were a combination of particles having the same particle diameter, and the average particle diameter was changed in the range of 10 μm to 100 μm. The magnitude of the coating variation was indicated by the above-described Zn equivalent thickness.
The test results are shown in Table 1.
Table 1 shows that the coating thickness variation (Zn equivalent thickness) of the low melting point brazing filler metal 5 with respect to the thickness (Zn equivalent thickness) 100 μm is less than 30 μm, pass (circle), and the case where it is 30 μm or more is rejected. (X mark).

  As is known from Table 1, it can be seen that a very uniform adhesion state can be obtained when both the zinc alloy particles and the flux particles contained in the low melting point brazing material have an average particle diameter of 20 μm or less. And by obtaining such a uniform adhesion state of the low melting point brazing material, it is possible to obtain a sufficient bonding strength even if the amount of the low melting point brazing material is reduced.

Explanatory drawing which shows the structure of the aluminum heat exchanger in Example 1. FIG. FIG. 3 is an explanatory view showing a region where a low melting point brazing material is adhered to a test piece in Example 2. FIG. 3 is an explanatory diagram showing a joined state of test pieces in Example 2. FIG. 6 is an explanatory diagram showing the relationship between the amount of low melting point brazing material attached and the shear strength in Example 2. Explanatory drawing which shows the relationship between the compounding ratio of a flux component and a brazing filler metal component, and shear strength in Example 2. FIG. Explanatory drawing which shows the coating thickness dispersion | variation in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum heat exchanger 10 Tube 11 Corrugated fin 12 Refrigerant inlet pipe 13 Refrigerant outlet pipe 21, 22 Test piece

Claims (5)

A low melting point brazing material used for joining between the plurality of members when producing an aluminum heat exchanger configured by joining a plurality of members made of an aluminum alloy,
A brazing filler metal component comprising zinc alloy particles having an average particle size of 20 μm or less;
A flux component composed of non-corrosive flux particles having an average particle size of 20 μm or less,
A low melting point brazing material for an aluminum heat exchanger, wherein a blending ratio (flux component weight / brazing material component weight) of the brazing filler metal component and the flux component is 0.6 to 2.0.   2. The low melting point brazing material for an aluminum heat exchanger according to claim 1, wherein the zinc alloy particles comprise, in mass%, Al: 2 to 6%, the balance being Zn and inevitable impurities. According to claim 1 or 2, the non-corrosive flux particles consist of a mixture composition of CsF and AlF _3, the mixing ratio _{CsF (mol%) / AlF 3} (mol%) is a 1.0 to 1.2 A low melting point brazing material for an aluminum heat exchanger, A method of manufacturing an aluminum heat exchanger configured by joining a plurality of members made of an aluminum alloy,
By attaching a low melting point brazing material to at least one member of the plurality of members and heating to a brazing temperature that exceeds the melting point of the brazing material component contained in the low melting point brazing material, A method for producing an aluminum heat exchanger, wherein the low melting point brazing material according to any one of claims 1 to 3 is used as the low melting point brazing material in brazing and joining.   The method for manufacturing an aluminum heat exchanger according to claim 4, wherein the brazing temperature is 450 ° C or lower.

Images