JPH1158068A - Brazing paste and brazing aluminum material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brazing paste capable of forming a brazing filler metal layer not generating the contamination of a brazing furnace due to the decomposition of a binder during brazing without leaving the residue of the binder after brazing and a brazing aluminum material having a high brazing property without blacking and the reduction of corrosion resistance due to the residue of the binder. SOLUTION: In the brazing aluminum, the brazing paste is composed by dispersing the powder of a brazing filler metal into a medium, using a resin containing the methacrylate resin having the repeating unit expressed by the following formula as binder, the brazing paste is coated on at least one part of the surface and dried, whereby the film of 10-100 g/m<2> in the quantity of brazing filler metal is formed. R in the formula each expresses n-butyl, i-butyl or sec-butyl.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing paste used for brazing when joining and assembling an aluminum alloy heat exchanger and the like, and a brazing aluminum material to which the paste is applied in advance.

[0002]

2. Description of the Related Art Aluminum alloy heat exchangers such as evaporators, condensers and radiators are assembled and manufactured by a brazing method. As an example, a parallel flow condenser is schematically shown in FIG. In the figure, 1
Indicates an extruded multi-hole flat tube, 2 indicates a fin, and 3 indicates a header pipe. For example, the fin 2 is a brazing sheet fin clad with brazing material, and is joined and assembled by brazing. The above is an example of using a brazing sheet clad with a brazing material as the fin 2. However, in recent years, since the heat exchanger has been required to be smaller and lighter, the fin 2 which has a limit in thinning has been replaced with a bare fin to reduce the thickness. A method has been proposed in which a metal powder containing a binder is coated on the outside of the tube 1 instead of the fins 2 by coating to form a brazing material layer, and these are joined by brazing (Japanese Patent Laid-Open No. 9-85483). Acrylic resin and methacrylic resin are mainly used for the binder at this time, but the conventionally used acrylic resin and methacrylic resin have a high decomposition temperature, so that a residue remains after brazing or blackening occurs, There has been a problem that the corrosion resistance of the alloy is adversely affected. In addition, these resins cannot be sufficiently decomposed and evaporated in a preheating furnace before brazing, and there is a problem in that the brazing furnace is contaminated by decomposition components generated during brazing.

[0003]

Accordingly, the present invention provides
It is an object of the present invention to provide a brazing paste capable of forming a brazing material layer in which no residue of a binder remains after brazing and a brazing furnace is not contaminated by decomposition of the binder during brazing. A further object of the present invention is to provide an aluminum material for brazing, which is free from blackening and deterioration in corrosion resistance due to binder residues and has high brazing properties.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above problems, and as a result, when a methacrylic resin having a specific structure is used as a binder resin, the decomposition temperature is maintained while the blocking resistance of the binder resin is maintained. It has been found that the above problem can be solved, and the present invention has been made based on this finding. That is, the present invention
(1) a brazing paste obtained by dispersing a brazing material powder in a medium using a resin containing a methacrylic resin having a repeating unit represented by the formula (I) as a binder;

[0005]

Embedded image

(Wherein, R represents n-butyl, i-butyl or sec-butyl). (2) Per 100 parts by weight of methacrylic resin, 2 to 35 parts by weight of a peroxide is further contained. The brazing paste according to (1) or (3) the brazing paste according to (1) or (2) is applied to at least a part of the surface and dried to obtain a brazing material having an amount of 10 to 10. 100g /
there is provided a brazing aluminum material, characterized in that the formation of the coating of m ^2.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The brazing paste of the present invention comprises:
It comprises a brazing filler metal powder, a methacrylic resin and a solvent. As the brazing filler metal powder used in the present invention, an aluminum alloy powder containing a predetermined amount of Si is preferable.
Aluminum alloy powder containing t% is more preferable. Si
By making the content higher than that of a normal brazing alloy, the amount of brazing material to be applied can be reduced. In addition, elements other than Si, for example, Z
n, Fe, Cu, Mn, In, Sn and the like may be included for the purpose of improving corrosion resistance. Further, a powder of Si alone can also be used. The particle size of the brazing filler metal powder used in the present invention is 5
１００100 μm is preferred. The smaller the particle size, the better from the viewpoint of dispersion stability. However, if the particle size is too small, the production cost of the powder increases, and an oxide film is easily formed, which may impair brazing properties. Also, if the particle size is too large, in the step of coating and drying the paste on the aluminum alloy, the brazing filler metal powder does not stay on the alloy surface and easily falls with the binder, so that it is difficult to achieve a predetermined brazing filler metal amount. May be. In the brazing paste of the present invention, the brazing material layer coated and dried on an aluminum material such as a tube material has a certain amount of brazing material in the paste so that a sufficient amount of brazing material is present for bonding. It is necessary that brazing filler metal exists. The concentration of the brazing material in the paste is usually 10 to 80% by weight, preferably 20 to 80% by weight.
６０60% by weight. In this case, the concentration of the brazing filler metal powder is 1
If it is less than 0% by weight, sufficient joining strength cannot be obtained at the time of brazing. Although the upper limit of the concentration of the brazing filler metal powder in the paste varies depending on the coating method, it is necessary to be about 80% by weight or less in order to secure the dispersibility and fluidity of the aluminum alloy powder required for coating. % By weight or less is preferred.
When the weight of the brazing filler metal powder in the paste exceeds about 80% by weight, the dispersibility and fluidity of the aluminum alloy powder as the brazing filler metal are insufficient, and as a result, the applicability of the paste is reduced. It cannot be applied uniformly on the heat exchanger member.

The methacrylic resin used in the present invention comprises:
The brazing filler metal acts on the aluminum alloy surface to form a uniform brazing filler metal layer. The methacrylic resin used in the present invention has an adhesion that cannot be peeled off by rolling or the like, and has a glass transition point (Tg) at an appropriate temperature, so that the brazing material surfaces do not stick to each other even during coiling under high temperature and high humidity. And volatile decomposition at as low a temperature as possible. The methacrylic resin having a specific structure represented by the formula (I) used in the present invention has this action. In the above formula (I), R represents n-butyl, i-butyl or sec-butyl. When the carbon number of R is 3 or less or 5 or more, the decomposition temperature of the binder increases, and a decomposition gas is generated during brazing. The methacrylic resin used in the present invention is T
g is preferably 50 to 150 ° C.,
The molecular weight is not particularly limited.

In order to further reduce the decomposition temperature, it is preferable to use a peroxide together with a methacrylic resin in the brazing paste of the present invention. In the present invention, a peroxide that does not decompose at about room temperature, does not adversely affect the aluminum alloy, and has a radical decomposition effect on the resin during brazing preheating is preferably used. The peroxide that can be used in the present invention can be represented by the following formula (II). Formula (II) X—O—O—X ′ (wherein X and X ′ represent an alkyl group, an aryl group, and an acyl group.) In the formula (II), the alkyl group represented by X and X ′ is a straight chain. Or branched, preferably having 1 to 1 carbon atoms
5 The aryl group represented by X and X 'preferably has 6 to 9 carbon atoms, and the acyl group preferably has 2 to 7 carbon atoms. Specific examples of the peroxide used in the present invention include dibutyl peroxide, dipropyl peroxide, diphenyl peroxide and the like. The use amount of the peroxide is preferably from 2 to 35 parts by weight, more preferably from 5 to 15 parts by weight, based on 100 parts by weight of the methacrylic resin. If the peroxide is too small, the effect of radical decomposition cannot be obtained. On the other hand, if the amount is too large, the stability of the brazing paste deteriorates, a decomposition reaction may occur even at room temperature, the binder may not function, and the blocking resistance may deteriorate. The decomposition temperature of the binder in the present invention is the temperature in the furnace of the brazing preheating furnace, and is 100 ° C. or more, preferably 150 to 250 ° C.

The dispersing medium for the brazing filler metal powder used in the present invention is not particularly limited as long as it disperses and dissolves the brazing filler metal powder and the above-mentioned methacrylic resin and gives appropriate properties as a paste suitable for coating. Specific examples include organic solvents such as xylene and toluene.
Alternatively, they can be used as a mixture. In the present invention, the ratio of such a medium to the methacrylic resin is from 0.03 to 0.2, preferably from 0.05 to 0.15, by weight ratio of the solvent to 1 solvent. The viscosity of the brazing paste to the present invention is not too high, and it is necessary that not too low, preferably about 10 to 10 ³ cp
(Measured at 25 ° C.. Hereinafter the same), more preferably about 10 to 10 ² cp.

[0011] The brazing paste of the present invention further comprises:
For adjusting the viscosity of the paste, a thickener such as various cellulose solutions can be added as needed. Further, if necessary, an appropriate amount of brazing flux may be added, so that the flux application step can be omitted. Examples of the flux at this time include a flux based on fluoride or cesium usually used for brazing. As long as the properties of the brazing paste of the present invention are not impaired, components other than those described above which are usually used for the brazing paste (slurry) can be added without any particular limitation.

Next, the brazing aluminum material having the brazing material layer of the present invention will be described. The brazing aluminum material of the present invention is obtained by forming a brazing material layer on an aluminum alloy material using the brazing paste of the present invention. The aluminum alloy material is not particularly limited in alloy composition and shape as long as it can perform brazing, and this is appropriately determined according to the use of the aluminum material for brazing. For example, when the application is an extruded tube, it is preferable to select an alloy having high extrudability, and when using a heat exchanger, it is preferable to select an alloy having high corrosion resistance. It also improves the adhesion and adhesion of the film,
The surface of the aluminum alloy preferably has irregularities in order to prevent the formation of locally unattached portions after brazing due to variations in the thickness of the painted plate, and 10 to 60 μm
Are more preferable.

In the present invention, the brazing material layer is formed by applying the brazing paste of the present invention on the above-mentioned aluminum alloy by a usual coating method such as pull-up coating, roll coater coating, spray coating and drying. Can be. The coating of the brazing material layer may be formed on at least a part of the surface of the alloy, and may be appropriately selected depending on the application and shape, for example, the outer surface of the aluminum alloy tube, one or both surfaces of the aluminum alloy strip. The amount of brazing material in the coating formed as described above is 10 to 100.
g / m ² . If the amount of brazing material in the coating is too small, the brazing properties will be poor, and if it is too large, the brazing properties will be saturated, but the coating thickness will increase and the gap will not be brazed to a part of the core after brazing. May occur.

[0014]

Next, the present invention will be described in more detail with reference to examples. Example 1 A cylindrical billet of an aluminum alloy (JIS A1050) was placed in a multi-hole flat tube (height 1.8 mm, width 16 mm,
After extruding into 9 holes, the surface was subjected to a blast treatment, and then a weak alkali etching treatment was performed to obtain a tube material. On the other hand, aluminum alloy powder (average particle diameter 40 μm, composition: 10 wt% of Si, Zn 15
wt%, balance Al), in the formula (I), the R group is n-
Butyl methacrylic resin (Tg 90 ° C.), toluene was used as a solvent, and the mixture was mixed so that the weight ratio of the brazing filler metal powder: methacrylic resin (powder): solvent was 30: 7: 63, and the resin was dissolved to obtain a viscosity of 50 cp. (Measured at 25 ° C .; the same applies hereinafter) was prepared. After immersing the above tube material in this brazing paste,
Baking and drying was performed at 0 ° C. for 30 seconds to form a film containing brazing powder on the surface of the tube material to obtain a brazing tube material. The amount of brazing material in the coating was 30 g / m ² .

Example 2 Brazing with a viscosity of 50 cp was carried out in exactly the same manner as in Example 1 except that a methacrylic resin (Tg 80 ° C.) in which R group was i-butyl in the formula (I) was used as the organic binder resin. Paste was prepared. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material. The amount of brazing material in the coating was 30 g / m ² .

Example 3 The same procedure as in Example 1 was carried out except that the peroxide ((CH ₃ ) ₃ CO—O—C (CH ₃ ) ₃ ) was further added to the brazing paste prepared in Example 1. Similarly, a brazing paste having a viscosity of 60 cp was prepared. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material.
The weight ratio of the brazing filler metal powder: the methacrylic resin: the peroxide: the solvent was adjusted to be 30: 7: 1: 62. The amount of brazing material in the coating was 40 g / m ² . Example 4 Example 3 except that the weight ratio of brazing filler metal powder: methacrylic resin: peroxide: solvent was 30: 7: 2: 61.
A brazing paste having a viscosity of 60 cp was prepared in exactly the same manner as described above. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material. The amount of brazing material in the coating was 40 g / m ² .

Example 5 The same procedure as in Example 2 was carried out except that the peroxide ((CH ₃ ) ₃ CO—O—C (CH ₃ ) ₃ ) was further added to the brazing paste prepared in Example 2. Similarly, a brazing paste having a viscosity of 60 cp was prepared. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material.
The weight ratio of the brazing filler metal powder: the methacrylic resin: the peroxide: the solvent was adjusted to be 30: 7: 1: 62. The amount of brazing material in the coating was 40 g / m ² . Example 6 Example 5 except that the weight ratio of brazing filler metal powder: methacrylic resin: peroxide: solvent was 30: 7: 2: 61.
A brazing paste having a viscosity of 60 cp was prepared in exactly the same manner as described above. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material. The amount of brazing material in the coating was 40 g / m ² .

Comparative Example 1 Example 3 except that the weight ratio of brazing filler metal powder: methacrylic resin: peroxide: solvent was 30: 7: 3: 60.
A brazing paste having a viscosity of 65 cp was prepared in exactly the same manner as described above. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material. The amount of brazing material in the coating was 45 g / m ² . Comparative Example 2 Example 5 except that the weight ratio of brazing powder: methacrylic resin: peroxide: solvent was 30: 7: 3: 60.
A brazing paste having a viscosity of 65 cp was prepared in exactly the same manner as described above. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material. The amount of brazing material in the coating was 45 g / m ² .

Comparative Example 3 A brazing paste having a viscosity of 55 cp was prepared in exactly the same manner as in Example 1 except that a methacrylic resin in which the R group was n-propyl in the formula (I) was used. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material. The amount of brazing material in the coating was 40 g / m ² . Comparative Example 4 A brazing paste having a viscosity of 65 cp was prepared in exactly the same manner as in Example 1 except that a methacrylic resin in which the R group was n-octyl in the formula (I) was used. This was applied on a tube material in the same manner as in Example 1 to obtain a brazing tube material. The amount of brazing material in the coating was 45 g / m ² .

Comparative Examples 5 and 6 -COOC ₃ H ₇ (n) was added to the side chain in place of the methacrylic resin.
In the same manner as in Example 1 except that an acrylic resin (molecular weight: about 100,000) or polyethylene glycol (molecular weight: 6,000) having
A cp brazing paste was prepared. Example 1
Was applied onto the tube material in the same manner as in Example 1 to obtain a brazing tube material. The amount of brazing material in the coating is 30 g / m
² , 15 g / m ² .

Test Examples The brazing tubes obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were tested and evaluated for brazing properties, volatile decomposition properties, and blocking resistance by the following methods. The results are shown in Table 1. (Brazing property) Bare fins (0.07 mm thick Al alloy, composition: Si 0.5 wt.) Cut out of each tube material obtained in Examples and Comparative Examples by 60 mm and corrugated
%, Fe1wt%, Ni 0.5wt%, Zn 2wt
%) And 20 mountains were combined to make a mini core. A fluoride-based flux was applied to the core in advance, and brazing heating was performed at 590 ° C. for 3.5 minutes in a nitrogen atmosphere. When the adhesion ratio of the fin after brazing was 100%, it was evaluated as ○, and when it was not 100%, it was evaluated as X. However,
The adhesion ratio is determined by peeling the fins from the mini-core tube for 20 hills and multiplying (the length of the bonded portion) / (the length of the bonded portion + the length of the non-bonded portion) by 100. It is the value obtained.

(Volatile Decomposition) Using a thermal analyzer, the 80% weight loss temperature of the obtained tube was measured. When the temperature was 250 ° C. or less, it was evaluated as ○, when it exceeded 250 ° C. and 350 ° C. or less, and when it exceeded 350 ° C., it was evaluated as x. (Blocking resistance) Two brazing material surfaces of the obtained tube material were overlapped with each other, and a pressure of 1 N / cm ² was applied.
This sample was placed in an atmosphere of 50 ° C. and 98% RH for 24 hours.
Leave it for a while and let the brazing material surfaces sticky and do not stick to each other. ○, the brazing material surfaces sticky but the brazing material surfaces do not stick together. did.

[0023]

[Table 1]

As can be seen from the results in Table 1, Examples 1 to
Each brazing tube material using the brazing paste obtained in 6 is excellent in brazing properties, has a low volatile decomposition temperature, and the brazing material layer adheres to each other even in coiling in a high-temperature and high-humidity environment. It has blocking resistance that will not be lost. The tube materials of Comparative Examples 1 and 2 contained too much peroxide to affect the brazing properties, and the Tg decreased, so that the blocking resistance deteriorated. In Comparative Examples 3 and 4 in which the R group in the formula (I) was n-propyl or n-octyl, the volatile decomposability was worse than in each of the examples, and the 80% weight loss temperature of the tube material was 350 ° C. or more. Was. Moreover, in the case of the tube materials of Comparative Examples 5 and 6 using the conventionally used acrylic resin or polyethylene glycol, the brazing properties were poor and the volatile decomposition temperature was high as compared with the tube materials obtained in the examples. Was.

[0025]

According to the brazing paste of the present invention,
The binder resin sufficiently decomposes and evaporates in a preheating furnace before brazing, and a brazing material layer having high brazing properties without stickiness even in a high-temperature and high-humidity environment can be formed. Therefore, the brazing aluminum material using the brazing paste of the present invention does not contaminate the brazing furnace, has little blackening or deterioration of corrosion resistance due to the residue of the binder resin, and has a low sticky brazing material surface during coiling. The brazing material surfaces do not stick together even under high temperature and high humidity. In addition, the brazing properties are high, the reliability of brazing and the efficiency of the brazing process are enhanced, and an excellent effect of enabling a high-quality aluminum alloy heat exchanger to be assembled is achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a parallel flow condenser.

[Explanation of symbols]

 1 Extruded multi-hole flat tube 2 Fin 3 Header pipe

Claims (3)

[Claims] 1. A brazing paste obtained by dispersing a brazing filler metal powder in a medium using a resin containing a methacrylic resin having a repeating unit represented by the formula (I) as a binder. Embedded image (In the formula, R represents n-butyl, i-butyl or sec-butyl.) 2. 2 to 100 parts by weight of methacrylic resin
The brazing paste of claim 1, further comprising 35 parts by weight of peroxide. 3. The method according to claim 1, wherein at least a part of the surface is provided.
An aluminum material for brazing, characterized in that a coating having a brazing material amount of 10 to 100 g / m < ² > was formed by applying and drying the above-mentioned brazing paste.