JP2008284565A - Paint for brazing aluminum alloy excellent in resistance to peeling of coating film, aluminum alloy sheet for brazing and aluminum alloy member for automotive heat exchanger using the same and automotive heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paint for brazing aluminum alloy excellent in resistance to peeling of a coating film, which prevents a coating film containing brazing filler metal and a flux from being peeled from an aluminum alloy sheet even under any manufacturing condition, and from which a coating film free from the degradation of adhesion and brazing property caused by moisture absorbing action is formed, an aluminum alloy sheet for brazing and an aluminum alloy member for automotive heat exchanger using the same and an automotive heat exchanger. <P>SOLUTION: This paint for brazing the aluminum alloy contains flux powder, an acrylic-resin binder and a silane coupling agent, and the powder of brazing filler metal is mixed as necessary, and the balance is a solvent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used for an automotive heat exchanger manufactured by a brazing method, and is an aluminum alloy brazing paint excellent in coating film peeling resistance, an aluminum alloy plate for brazing, and an aluminum alloy for automotive heat exchangers using the same. The present invention relates to a member and an automobile heat exchanger.

Conventionally, in aluminum members used in water-cooled automobile heat exchangers such as radiators and heater cores, for example, an Al-Si brazing material is provided on one side of a tube material or a header material, and a JIS standard 7072 alloy is provided on the other side. A brazing sheet clad with a sacrificial anode skin material is used, combined with a bare fin material and brazed.
Further, in car air conditioner materials such as capacitors, an extruded multi-hole tube and a so-called clad fin material in which a brazing material is clad on both surfaces are combined and brazed. Such a member for an automobile heat exchanger is molded and assembled into a shape as a heat exchanger, and then a fluoride-based flux (mainly KAlF ₄ ) is applied, and it will be in an inert gas atmosphere such as nitrogen gas. It is attached.

  However, when the conventional brazing method as described above is used, the aluminum alloy clad material is very expensive, and the flux is non-uniform and surplus, resulting in an increase in manufacturing cost. In addition, flux scattering occurs in the coating process, so it is necessary to take environmental measures such as health management for workers, and maintenance costs are required in terms of equipment management, resulting in a significant increase in manufacturing costs. . Furthermore, there is a problem that brazing failure occurs in the joining between members due to the flux falling off.

  For this reason, recently, a technique for brazing without using a clad material as described above has been developed, for example, a composition comprising Si, Cu, Ge and a flux on the surface of aluminum, copper, brass, steel or the like. A technique for applying an object and brazing the metal and an aluminum member has been proposed (for example, Patent Document 1). The technique described in Patent Document 1 is applied to a condenser of a car air conditioner, and a heat exchanger in which a brazing material composition applied to an extruded multi-hole pipe and a bare fin are joined in combination is put into practical use.

  However, the technique described in Patent Document 1 has a problem that, as in the case of using the clad material, the amount of flux applied becomes non-uniform, resulting in excessive flux and an increase in manufacturing cost. In addition, since there are many cases in which a binder is not used when brazing by such a method, a coating film (flux) may be lost in a process treatment performed after coating as described above, and there is a possibility that poor brazing may occur. is there. Further, similarly to the above, since the flux is scattered in the coating process, it is necessary to take environmental measures, and there is a problem that the manufacturing cost increases.

  In addition, a heat exchanger has been proposed in which a brazing filler metal or flux powder is applied to an aluminum alloy base material before processing, and this is formed by a method such as pressing (for example, Patent Document 2). According to the aluminum heat exchanger described in Patent Document 2, it is possible to prevent the flux from being excessively applied without using an expensive aluminum alloy clad material, and to perform a coating process using a binder. Thus, the coating film can be prevented from falling off in the subsequent process, and a heat exchanger can be efficiently obtained by the brazing method.

However, in the heat exchanger described in Patent Document 2, since the adhesion of the coating film to the aluminum alloy base material is not so high, the coating film is peeled off when the aluminum alloy material is processed with a large deformation. May occur. For this reason, although the above-described coating film is used by applying it to an extruded material that is hardly subjected to molding processing, there is no problem, but a material that is subjected to large molding processing such as a plate material. When used by applying to the surface, there is a risk that the adhesion will be insufficient and the coating film will peel off, resulting in poor brazing.
In addition, a film in which a coating film as described in Patent Document 2 is formed on the plate material may be used. In such a case, the coating film is formed only on a portion that does not come into contact with the mold during molding. Therefore, there is a problem that it cannot be applied to a complicated product shape.

  As described above, in the brazing method described in Patent Document 1 in which the coating film is formed on the molded member, the coating film is peeled off when the heat exchanger is assembled, and is made of the above components in advance. In the heat exchanger brazing method described in Patent Document 2 in which a heat exchanger is configured using a pre-coated plate on which a coating film is formed, the coating film is peeled off during the molding process of the member, which is high in any case. There was a problem that the attachment strength could not be obtained.

  In addition, for the purpose of improving coating film adhesion at the time of processing an aluminum alloy material, a structural unit derived from a monoacrylate of ethylene glycol substituted with a specific group and a structural unit derived from an acid group-containing ethylenically unsaturated monomer Brazing binder comprising a binder for brazing made of an acrylate copolymer containing a binder and 0.1 to 50 parts by weight of a crosslinking agent per 100 parts by weight of the brazing binder Compositions have been proposed (for example, Patent Document 3).

However, when the brazing composition described in Patent Document 3 is applied to an aluminum alloy material, sufficient peel resistance can be obtained when subjected to strong processing such as pressing or roll forming. There is no problem.
In addition, it is known that a coating film made of a brazing composition causes a decrease in adhesion and brazing between the coating film and the substrate due to moisture absorption. Even in the composition for attachment, there is a problem that the adhesion of the coating film and the brazing property are lowered by the hygroscopic action. Such a hygroscopic effect has a large influence even in a standing period of about one day in a high humidity environment, and therefore, the humidity management of the heat exchanger member after forming the coating film is important. For this reason, there has been a problem that a great deal of cost is required for member management after the coating film is formed, such as securing a storage place where air-conditioning management is carefully performed, and the manufacturing cost increases.
Japanese National Patent Publication No. 6-504485 Japanese Patent Laid-Open No. 9-029477 JP 2005-028400 A

  As described above, when an aluminum alloy is brazed using a conventional brazing composition, there is a possibility that the coating film peels off and the brazing strength after brazing is lowered, and brazing using a flux is performed. In the process, there is a problem that an environmental measure or the like in the process is required and the manufacturing cost increases. In addition, in order to prevent the peeling of the coating film due to moisture absorption of the brazing composition, member management such as air conditioning is required, which causes a problem that the manufacturing cost further increases. For this reason, in an aluminum alloy brazing paint containing flux, brazing powder, etc., when applied to a pre-coating material before molding, the coating film is not peeled off even in strong processing such as press molding or roll forming. Even if it is applied to a molded part, it has excellent adhesion that does not cause peeling of the coating film in the assembly process of heat exchangers, etc., and improves the moisture resistance of the coating film. There has been a demand for an aluminum alloy brazing coating material capable of forming a coating film that can prevent deterioration of adhesion due to moisture absorption caused by the film and deterioration of brazing properties.

  The present invention has been made in view of the above problems, and can prevent the peeling of the coating material containing the brazing material and the flux from the aluminum alloy material under any manufacturing conditions, and also by the hygroscopic action. Aluminum alloy brazing paint excellent in coating film peeling resistance capable of forming a coating film in which adhesion and brazing are not deteriorated, brazing aluminum alloy plate, and automotive heat exchanger using the same An object of the present invention is to provide an aluminum alloy member and an automobile heat exchanger.

In order to solve the above problems, the present inventors diligently studied the binder used in the aluminum alloy brazing paint, and when the amount of the hydroxyl group in the binder is increased, the effect of improving the adhesion is not related to other functional groups. Although it is small, it has been found that there is a merit that the decrease in brazing property is small compared to the case where the amount of other functional groups is increased. Therefore, an aluminum alloy brazing paint is formed using a binder obtained by reacting a hydroxyl group and a silane coupling agent, and the adhesion between the binder and the aluminum alloy substrate and between the binder and the powder is improved. As a result, it was found that excellent peel resistance was obtained, and the present invention was completed.
That is, the present invention relates to the following.

(1) The invention according to claim 1 is characterized in that it contains a flux powder, an acrylic resin binder, and a silane coupling agent, and if necessary, a brazing filler metal powder is blended, and the remainder is a solvent. An aluminum alloy brazing paint with excellent coating film peel resistance.
(2) Invention of Claim 2 The organic functional group of the said silane coupling agent is any one of amino, diamino, epoxy, vinyl, methacryloxy, acryloxy, isocyanate, or two of these 2. The aluminum alloy brazing paint excellent in coating film peel resistance according to claim 1, wherein the functional groups are combined as described above.
(3) The invention according to claim 3 The acrylic resin binder,
(A) methacrylic acid alkyl ester monomer,
(B) an acrylic acid alkyl ester monomer,
(C) It consists of an acrylic resin obtained by copolymerizing each of ethylenically unsaturated monomers containing a hydroxyl group, and the weight ratio (a) :( b) :( c) of these monomers is 3. The coating composition for brazing of an aluminum alloy excellent in coating film peeling resistance according to claim 1 or 2, wherein the coating ratio is in the range of 93: 2: 5 to 55:15:30.
(4) Invention of Claim 4 Water was added as a hydrolysis accelerator of the said silane coupling agent, The coating-film peeling resistance of any one of Claims 1-3 characterized by the above-mentioned. Excellent aluminum alloy brazing paint.

(5) Invention of Claim 5 The brazing coating film layer which consists of the coating composition for aluminum alloy brazing which is excellent in the coating-film peeling-proof property of any one of Claims 1-4 is an aluminum alloy base material. An aluminum alloy plate for brazing, which is formed on at least one surface.
(6) Invention of Claim 6 The aluminum alloy member for motor vehicle heat exchangers which uses the aluminum alloy plate for brazing of Claim 5.
(7) Invention of Claim 7 The automobile heat exchanger using the aluminum alloy member for automobile heat exchangers of Claim 6.

According to the aluminum alloy brazing coating material having excellent coating film peel resistance according to the present invention, as described above, it contains flux powder, an acrylic resin binder, and a silane coupling agent. Due to the constitution in which the composition is blended, it is possible to form a brazed coating layer having high adhesion and suppressed hygroscopicity on the aluminum alloy plate.
As a result, the peel resistance of the brazing coating layer is improved, and an aluminum alloy plate for brazing excellent in brazing properties and strength properties after brazing is obtained. The aluminum alloy member for motor vehicle heat exchangers used can be comprised.
Therefore, the assembly efficiency when manufacturing the automotive heat exchanger by the brazing method is improved, and the strength of the automotive heat exchanger after assembly can be improved.

  Hereinafter, the aluminum alloy brazing coating material (hereinafter sometimes abbreviated as “brazing coating material”) and the brazing aluminum alloy plate (hereinafter abbreviated as “aluminum alloy plate”) having excellent coating film peel resistance according to the present invention. 1), and an aluminum alloy member for an automotive heat exchanger (hereinafter, may be abbreviated as an aluminum alloy member) using the same, and an embodiment of the automotive heat exchanger, refer to FIGS. While explaining.

[Aluminum alloy brazing paint]
The brazing paint of this embodiment (see also the brazing coating layer 3 shown in FIG. 1) contains flux powder, an acrylic resin binder, and a silane coupling agent. It mix | blends, the remainder is made into a solvent, and is comprised roughly.

"Flux powder"
The flux powder is blended with an acrylic resin binder, a silane coupling agent, and a brazing material powder to form a brazing paint.
As the flux powder, a commonly used fluoride flux such as KAlF ₄ , KZnF ₃ , K ₂ SiF _{6 and the} like can be appropriately selected and used without any problem.
As for the flux powder, KAlF ₄ or the like that forms the flux powder is melted when brazing the aluminum alloy plate 1 on which the coating layer 3 for brazing made of a brazing paint as illustrated in FIG. 1 is formed. Then, the aluminum alloy plate 1 and the oxide film of the brazing material powder are destroyed, and the brazing property is improved.

The particle size of the flux powder is limited by the thickness of the brazing coating layer 3 formed by applying the brazing paint of the present embodiment on the aluminum alloy substrate 2 as shown in FIG. In essence, there is no effect on adhesion and coating strength.
Moreover, it is preferable that the average particle diameter of all the particles of the component composition is 1-5 micrometers or less. By setting the particle size of all the particles of the flux powder to the above, the brazing property can be improved.
When the particle size of the flux powder exceeds 5 μm, for example, when the radiator 20 in which a plurality of tubes are aligned as shown in FIG. 3 is assembled, the tubes (aluminum alloy members for automobile heat exchanger) 10 and the fins 22 It will be in the state assembled | attached by the flux powder with a large particle size interposing in a junction part. When the heat brazing process is performed in this state, the flux powder having a large particle size is dissolved, and the tube 10 and the fins 22 are reduced in size and brazed. When the tube 10 and the fins 22 are assembled with, for example, several tens of layers, the reduction in each joint is accumulated, and the dimensions in the radiator core may be greatly shifted by several millimeters, resulting in poor brazing. There is.
In addition, the minimum of the particle size of the flux powder normally used is 1 micrometer.

"Acrylic resin binder"
The acrylic resin-based binder that is blended in the brazing paint of this embodiment has an action of fixing the brazing filler metal powder and the flux powder to the aluminum alloy substrate 2.

As a result of intensive studies on the binder used in the aluminum alloy brazing paint, the present inventors have obtained the following knowledge.
In general, as a binder used for brazing, as a group for imparting adhesion and coating strength to an aluminum alloy substrate of a coating layer for brazing made of a brazing coating, a phosphate group, a carboxylic acid group, Functional groups such as a sulfonic acid group and a hydroxyl group are employed, and the mixing ratio thereof is determined in consideration of the residual carbon property at the time of brazing. However, each functional group described above contributes to the improvement in adhesion as the blending ratio in the binder is increased, but there is also a problem that the brazing property is lowered, and there is a limit to the improvement only by increasing the functional group. There is.

  Here, as for the hydroxyl group in each of the above functional groups, the present inventors have reduced the brazing property although the effect of improving the adhesion when the amount of the hydroxyl group is increased is small compared to other functional groups. It has been found that there is a merit that is small compared to the case where the amount of other functional groups is increased. Therefore, the present inventors pay attention to the hydroxyl group, and react the hydroxyl group with a silane coupling agent, which will be described in detail later, between the acrylic resin binder and the aluminum alloy substrate, and the acrylic resin binder and powder (flux powder). In order to improve the adhesion of the coating film, the experiment was repeated. As a result, it has been clarified that an acrylic resin-based binder having excellent adhesiveness that can withstand strong processing molding can be obtained without relying on the conventional improvement by increasing the amount of the functional group. Furthermore, the moisture resistance of the coating film is greatly improved by such a configuration, and it has become possible to prevent a decrease in adhesion and brazing due to the hygroscopic action that has occurred in conventional coating films.

As one of the factors that can obtain such an effect, the silane coupling agent is disposed in the gap between the acrylic resin binder and the aluminum alloy base material, and the gap between the acrylic resin binder and the powder, so that the moisture intrusion route can be obtained. Can be expected to decrease. From the viewpoint of chemical bonding, the hydroxyl groups in the conventional coating are thought to have been bonded to the aluminum alloy substrate or powder by hydrogen bonding, but the hydrogen bonding is easily peeled off by the intervention of water. Because the bond is weak, the coating film strength tends to decrease due to the hygroscopic action of the coating film, and the moisture due to moisture absorption increases the oxygen concentration during brazing, leading to a decrease in brazing properties. It is done.
The aluminum alloy brazing paint of the present invention uses a binder in which a hydroxyl group and a silane coupling agent are firmly bonded to each other through a covalent bond, so that it is possible to prevent the change with time due to moisture as described above. It becomes.

  In the above description, improvement of moisture resistance is described. However, since there is no gap between the aluminum alloy base material and the powder, for example, the intrusion route of the molding oil used in the molding process into the coating film is reduced. Therefore, it is considered that various resistance improvement effects can be obtained.

  As long as the binder used for the brazing paint of this embodiment is a general acrylic resin, a certain effect can be expected with any resin, but the molecular weight is within the range of about 20,000 to 500,000. In this case, a greater effect can be obtained. Further, as a main skeleton, (a) an alkyl methacrylate monomer, (b) an acrylic acid alkyl ester monomer, and (c) an ethylenically unsaturated monomer containing a hydroxyl group are copolymerized. It is preferable to use the obtained acrylic resin and further use a silane coupling agent described later in order to further improve the adhesion of the coating film.

The weight ratio of each of the monomers (a), (b), and (c) is in the range of (a) :( b) :( c) = 93: 2: 5 to 55:15:30. From the viewpoints of adhesion and brazing, it is more preferable that (a) :( b) :( c) = 90: 5: 5 to 65:15:20.
Here, when the monomer {(b) acrylic acid alkyl ester monomer} is less than 2 by weight, there are few reaction sites with the silane coupling agent, and the effect of filling the gap between the binder and the powder is low. The hygroscopicity reducing effect cannot be obtained. On the other hand, if the monomer (b) exceeds 15 by weight, the reaction with the silane coupling agent is many, contrary to the above, so that the effect of filling the gap between the binder and the powder is enhanced, but brazing. The remaining charcoal at the time increases, which may adversely affect brazing.

  In addition, when the amount of monomer {(c) ethylenically unsaturated monomer containing a hydroxyl group} is large, the thermal decomposability is lowered, and therefore, when monomer (c) of 30 or more by weight is added In this case, the remaining charcoal at the time of brazing increases, which causes poor brazing. At this time, the acrylic resin binder may contain a functional group other than the hydroxyl group as described above as long as the amount of the functional group is suppressed within a range that does not adversely affect the brazing property.

  Examples of the alkyl methacrylate monomer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, 2-methylpropyl methacrylate, normal butyl methacrylate, isobutyl methacrylate, tertiary butyl methacrylate, methacrylic acid 2 -Ethylhexyl, octyl methacrylate, isodecyl methacrylate, tridecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, stearyl methacrylate, tetrahydrofurfuryl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, etc. Can be mentioned.

  Examples of the acrylic acid alkyl ester monomer include methyl acrylate, ethyl acrylate, propyl acrylate, 2-methylpropyl acrylate, normal butyl acrylate, isobutyl acrylate, tertiary butyl acrylate, 2-acrylate. Examples include ethylhexyl, octyl acrylate, isodecyl acrylate, tridecyl acrylate, lauryl acrylate, cyclohexyl acrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, dimethylaminomethyl acrylate, and dimethylaminoethyl acrylate. It is done.

  Examples of the ethylenically unsaturated monomer containing a hydroxyl group include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate. Monohydroxy-containing (meth) acrylates such as 1,2-dihydroxyethyl methacrylate, 1,2-dihydroxypropyl methacrylate, 1,2-dihydroxybutyl methacrylate having 1, 2 or more hydroxyl groups in one molecule, 1,2- Dihydroxy 5-ethylhexyl methacrylate, 1,2,3-trihydroxypropyl methacrylate, 1,2,3-trihydroxybutyl methacrylate, 1,1-dihydroxyethyl methacrylate, 1,1-dihydroxypropyl methacrylate Rate, 1,1-dihydroxy-butyl methacrylate 1,1,2-hydroxypropyl methacrylate, 1,1,2-hydroxybutyl methacrylate and the like.

  In addition, as long as the compounding quantity of a functional group is suppressed in the range which does not exert a bad influence on brazing property, the acrylic resin binder may contain functional groups other than the hydroxyl group mentioned above. In addition, the present inventors separately examined a crosslinking reaction using a hydroxyl group and conducted a blending test of glyoxal, a polyepoxy-based agent, a titanium chelating agent, a urea resin, etc., but when these components were blended Was not as effective as the silane coupling agent described below.

"Silane coupling agent"
For example, the silane coupling agent contained in the brazing paint is applied to the aluminum alloy substrate 2 as shown in FIG. It is arranged between the resin binders and between the flux powder and the brazing filler metal powder and the acrylic resin binder, and contributes to the improvement of the coating film strength and the substrate adhesion.

  In general, an alkoxyl group that causes a dehydration condensation reaction of a silane coupling agent is bonded to an inorganic substance (aluminum alloy base material 2, flux powder, brazing powder), while an organic reactive group is bonded to an acrylic resin binder. In the present invention, if a general silane coupling agent is used, there are effects such as weak bonds between hydrogen bonds and alkyl groups, and all of them have a certain effect, but they react with the hydroxyl groups in the acrylic resin binder. If a silane coupling agent having a functional group to be used is used, a strong chemical bond is generated, so that a high effect can be obtained. In addition, when an amino group, diamino group, epoxy group, vinyl group, methacryloxy group, acryloxy group, or isocyanate group is used as the organic functional group of the silane coupling agent, it bonds firmly to the acrylic resin binder and provides better adhesion. Sex can be obtained. In addition to this, when a methoxy group is used as the inorganic functional group, it is preferable in that a much better adhesion can be obtained.

  The blending amount of the silane coupling agent in the paint for brazing according to this embodiment is such that the weight ratio of the acrylic resin binder to the silane coupling agent is 100 based on the blending amount of the acrylic resin binder in the brazing coating. : It is preferable that it is the range of 0.5-100: 50. If the blending amount of the silane coupling agent is less than 0.5 in the above weight ratio, the effect of improving the adhesion cannot be obtained, and even if the weight ratio exceeds 50, the effect of adding a large amount cannot be expected.

  Examples of the silane coupling agent used in the present embodiment include 3-acryloxypropyltrimethoxysilane (organic functional group: acryloxy group), 3-aminopropyltrimethoxysilane (the same amino group), N-2- ( Aminoethyl) -3-aminopropyltriethoxysilane (diamino group), 3-isocyanatopropyltriethoxysilane (isocyanate group), 3-glycidoxypropylmethyldiethoxysilane (epoxy group), 3-glycid Xylpropyltrimethoxysilane (same epoxy group), 3-glycidoxypropyltriethoxysilane (same epoxy group), vinyltrimethoxysilane (same vinyl group), 3-methacryloxypropyltrimethoxysilane (same methacryloxy group), p-styryltrimethoxysilane Group), 3-mercaptopropyl trimethoxysilane (the mercapto group).

"Brass powder"
The brazing material powder is a brazing material contained in the brazing paint together with the flux powder and the acrylic resin binder, and forms the brazing by diffusing into the aluminum alloy base material (see reference numeral 2 in FIG. 1) at the time of brazing. To do.
As the brazing filler metal powder, for example, conventionally known ones such as Si powder, Al—Si alloy powder, Al—Cu alloy powder, etc. can be used, and any one of these may be used alone or in combination of two or more. It can be used by mixing, and further contains inevitable impurities.

The particle size of the brazing material powder is limited by the thickness of the coating layer 3 for brazing formed on the aluminum alloy substrate 2 as in the case of the flux powder described above. There is no effect.
When an aluminum alloy base material is used for a radiator tube material or the like and a coating film coating amount is 20 g / m ² or less and a relatively thin film is applied, the particle size of the brazing filler metal powder is 10 μm or less in order to suppress erosion. It is preferable that However, if the main particle size is less than 1 μm, the surface area of the powder increases and it is necessary to increase the flux. Therefore, the particle size of the brazing powder is more preferably in the range of 1 to 10 μm. On the other hand, when an aluminum alloy base material is used for a radiator header plate material or the like and a coating amount is 40 g / m ² or more and a relatively thick film is applied, in order to suppress an increase in oxide film due to the particle size, 10 μm or more It is preferable to use a particle size of 20 μm or more. However, since the allowable erosion depth is limited by the plate thickness of the member, for example, in a header member of 1 mmt or more, the upper limit of the particle size is preferably about 75 μm.

  As described above, according to the coating material for brazing aluminum alloy having excellent coating film peel resistance according to the present embodiment, as described above, containing flux powder, an acrylic resin binder, and a silane coupling agent, A brazing coating powder layer having a high adhesiveness and a suppressed hygroscopicity can be formed on the aluminum alloy base material by the composition in which the brazing filler metal powder is blended as necessary. As a result, it is possible to form a brazing coating layer having excellent resistance to peeling of the coating film on the aluminum alloy substrate, and to construct an aluminum alloy plate for brazing that is excellent in brazing properties and strength properties after brazing. Become.

[Aluminum alloy plate for brazing]
Below, the aluminum alloy plate (aluminum alloy plate) 1 for brazing concerning this invention is demonstrated, referring FIGS. 1-3 suitably.
The aluminum alloy plate 1 of the present embodiment is formed by forming the aluminum alloy brazing paint excellent in coating film peeling resistance according to the present invention as described above on at least one surface of the aluminum alloy substrate 2. . In the aluminum alloy plate 1 of the embodiment shown in FIG. 1, a brazing coating layer 3 made of the above-mentioned brazing paint is formed on the one surface 2 a side of the aluminum alloy substrate 2.

(Aluminum alloy base material)
The aluminum alloy substrate 2 is a substrate of the aluminum alloy plate 1 of the present embodiment, and any conventionally known aluminum alloy material can be used without any problem. For example, Si, Mn, the remaining Al and inevitable impurities can be used. The component composition is contained, and other elements are added as necessary to improve strength characteristics, erosion resistance, and the like.
In the example shown in FIG. 1, the brazing coating layer 3 made of the above-described brazing paint is formed only on one surface 2a of the aluminum alloy substrate 2, but the other surface 2a is also brazed. A configuration in which the film layer 3 is provided may be employed. Moreover, it can also be set as the structure which provided the brazing coating-film layer 3 in the 1st surface 2a side, and provided the sacrificial material coating-film layer containing Zn for improving the corrosion resistance of an aluminum alloy board in the other surface 2b side.

(Method of forming a brazed coating layer)
The solvent used when the above-mentioned brazing paint is applied to the one surface 2a of the aluminum alloy substrate 2 to form the brazed coating layer 3 is not particularly limited, and the resin used for the binder is organic. Uses a conventionally known organic solvent, and in the case of a water-soluble resin, water can be used as a solvent. As the organic solvent, 3-methoxy-3-methyl-1-butanol can be suitably used from the viewpoint of ease of handling during work and environmental aspects.

The silane coupling agent compounded in the brazing paint of this embodiment requires hydrolysis on the alkoxyl group side before being applied to the aluminum alloy substrate 2 to form the brazed coating layer 3. Even when an organic solvent is used, hydrolysis proceeds due to moisture contained in the air, so that an effect obtained by adding a silane coupling agent can be obtained without positively adding water. However, the amount of moisture in the air may vary greatly, and sufficient hydrolysis may not always be obtained. Since the alkoxyl group remaining without being hydrolyzed has low reactivity with an inorganic material such as an aluminum alloy base material, it does not sufficiently contribute to the improvement of adhesion. In addition, it is not preferable that the alkoxyl group remains without being hydrolyzed because it may be a source of harmful gas in a brazing atmosphere.
In order to sufficiently hydrolyze the alkoxyl group, the amount of water required for hydrolysis of the silane coupling agent is added to the paint for brazing in advance to suppress the remaining unhydrolyzed alkoxyl group. And excellent coating adhesion can be obtained.

The method for applying the brazing paint to the one surface 2a of the aluminum alloy substrate 2 may be selected as appropriate in consideration of the member to be applied, the amount of application, and the like. For example, roll coating, die coating, flow coating, spraying Various means such as shower, dipping, brush, and bar coat can be selected and used. Due to the difference in the coating methods, there is no difference in the characteristics of the brazed coating layer 3. However, since there is an optimum value such as viscosity in each coating method, it is preferable to optimize the solvent blending ratio as appropriate. Moreover, the material of the aluminum alloy substrate 2 to be used does not affect properties such as coating film adhesion.
The brazed coating layer 3 may be formed on the entire surface 2a of the aluminum alloy substrate 2, but may be configured to be formed only at a location where brazing is performed on the aluminum alloy plate 1, for example. .

(Sacrificial coating layer)
In the aluminum alloy plate 1 of the present embodiment, as described above, a sacrificial material made of a composition containing Zn-containing flux powder and the above-described binder on the other surface 2b side of the aluminum alloy substrate 2. It is good also as a structure provided with the coating-film layer.
Here, as the flux powder containing Zn, for example, a fluoride-based flux such as ZnF ₂ or KZnF ₃ can be used, and KAlF ₄ or the like may be mixed and used.

By providing a sacrificial material coating layer containing Zn on the other surface 2b side of the aluminum alloy substrate 2, the corrosion resistance on the other surface 1b (the other surface 2b of the aluminum alloy substrate 2) side of the aluminum alloy plate 1 is improved. It becomes possible.
Moreover, when forming the tube 10 (aluminum alloy member for brazing) which consists of the aluminum alloy board 1 like the example shown in FIG. 2, the other surface 1b (other surface 2b) in which a sacrificial material coating film layer is provided. By forming the tube so that the side is on the inside, the corrosion resistance of the inner surface of the flow hole 10a formed on the inner side of the tube 10 is improved, and the progress of corrosion due to the coolant flowing in the flow hole 10a can be prevented.

[Aluminum alloy member for brazing for automobile heat exchanger and automobile heat exchanger]
The brazing aluminum alloy plate 1 of the present embodiment as described above is an alloy that forms, for example, a radiator tube (aluminum alloy member for automobile heat exchanger: hereinafter sometimes abbreviated as a tube) 10 as shown in FIG. It can be used as a plate material, and the tube 10 is used by being incorporated in a radiator (heat exchanger) 20 as shown in FIG.
The tube 10 is formed as a hollow flat tube material having a flow hole 10a inside by bending the aluminum alloy plate 1 so that the other surface 1b side is inside and joining both ends (not shown). can get.

A radiator 20 shown in FIG. 3 is used, for example, in a radiator of an automobile, and is generally configured by a tube 10, a header 21, fins 22, and side supports 23. The radiator 20 is manufactured by integrating the tube 10, the header 21, and the fins 22 by brazing and further attaching a resin tank by mechanical joining (caulking).
In the radiator 20, the header 21 and the tube 10 are arranged around the insertion portion by inserting the end portion of each tube 10 into a plurality of slots (insertion holes) 21 a formed on the lower surface of the header 21. The tubes 10 and the fins 22 are brazed to each other using a material, and the composition applied to the surface of the tube 10, that is, one surface 1 a side of the aluminum alloy plate 1 (one surface 2 a of the aluminum alloy substrate 2). It is assembled by brazing each other using the brazed coating layer 3 provided on the side).

[Brazing method]
As shown in FIG. 3, when assembling and brazing the radiator 20 including the tube 10 made of the aluminum alloy plate 1 of the present embodiment, the brazing coating layer 3 was provided on the surface of the header 21. After assembling the tube 10 and the fins 22, the brazing material is dissolved by heating to an appropriate temperature in an appropriate atmosphere such as a nitrogen atmosphere.
The brazing heat treatment is preferably performed at about 580 ° C. to 610 ° C., and the holding time is preferably about 1 minute to 10 minutes.
If the temperature during brazing is less than 580 ° C., partial melting of the brazing material and the aluminum alloy base material will not proceed, and it will be difficult to perform good brazing.
When the temperature at the time of brazing exceeds 610 ° C., there is a risk of significant erosion.

  According to the structure of the radiator 20 described above, since the tube 10 is joined to the header 21 provided with the slot 21a for inserting the tube 10 on the lower surface, the strength of the entire assembly after brazing can be increased. it can.

  As described above, according to the brazing aluminum alloy plate 1 of the present embodiment, the brazing coating layer 3 made of the brazing paint according to the present invention is provided. The peel resistance of the coating layer 3 is improved, and the brazing aluminum alloy plate 1 having excellent brazing properties and strength properties after brazing is obtained. Further, a tube (aluminum alloy member for an automobile heat exchanger) 10 can be configured using the aluminum alloy plate 1 for brazing of the present embodiment, and further, a radiator (an automobile heat exchanger) 20 can be formed using the tube 10. When configured, the assembly efficiency when the radiator 20 is manufactured by the brazing method is improved, and the strength after the radiator 20 is assembled can be improved.

Hereinafter, although an Example is shown and the coating material for aluminum alloy brazing excellent in the coating-film peeling resistance of this invention is demonstrated in more detail, this invention is not limited to this Example.
Below, the preparation process and evaluation test item of an aluminum alloy plate are demonstrated.

[Production process]
First, 3003-H14 was used as an aluminum alloy material, and an aluminum alloy base material having a plate thickness of 0.25 mmt was produced.
Moreover, as a brazing coating material to be applied as a brazing coating layer, a coating composition having a composition ratio shown in Table 1 below was prepared.
And as shown in FIG. 1, after apply | coating the composition which makes the brazing coating-film layer of each component composition on the one surface side of an aluminum alloy base material in the quantity of about 10 g / m < ² >, The brazed coating layer 3 was formed by drying at a temperature of 150 ° C. for 5 minutes, and the aluminum alloy plate 1 according to the present invention and the conventional aluminum alloy plate were obtained for each production condition shown in Table 1.
The acrylic resin binder shown in Table 1 below is an ethylenically unsaturated monomer containing (a) an alkyl methacrylate monomer, (b) an alkyl alkyl monomer, and (c) a hydroxyl group. There are methyl methacrylate or propyl methacrylate as the methacrylic acid alkyl ester monomer, methyl acrylate or butyl acrylate as the acrylic acid alkyl ester monomer, and methacrylic acid as the ethylenically unsaturated monomer containing a hydroxyl group. 2-hydroxyethyl acid or 2-hydroxybutyl methacrylate was used, respectively.
Moreover, as a silane coupling agent used in each Example, the thing of AK shown in following Table 2 was used, respectively, and it showed with the code | symbol in following Table 1. FIG.
Moreover, as an additive used in each comparative example, the thing of L and M which occupy in the following Table 3 was used, respectively, and it showed with the code | symbol in the following Table 1.

[Evaluation test]
About the aluminum alloy plate obtained by the said preparation process, three items, "adhesion", "humidity resistance", and "brazing property" demonstrated below, were evaluated and determined.

(Adhesion)
A test piece of 50 mm × 50 mm × 0.25 mmt (excluding the brazed coating film) was prepared from the samples of the aluminum alloy plates of the above examples and comparative examples, and a bending portion rubbing test as described below was performed. .
First, the test piece was bent at an angle of 180 ° so that the surface on the brazing coating layer side was the outside and the bending portion inner diameter was 1 mm, and then bent with a volatile oil-impregnated felt at a load of about 1 kg. The part vertex was subjected to 10 reciprocating rubbing treatments.
And, by visually observing the peeling state of the brazed coating layer from the aluminum alloy base material in the bent portion, and confirming the length of the peeled portion relative to the length of the rubbing target portion, it was determined according to the following evaluation criteria. .
(1) ○: No peeling was observed at the rubbing target portion of the bent portion.
(2) Δ: Peeling was observed at a part of the rubbing target portion of the bent portion.
(3) x: Peeling was observed in the entire portion to be rubbed in the bent portion.

(Moisture resistance)
A test piece of 50 mm × 50 mm × 0.25 mmt (excluding the brazed coating film) was prepared from the samples of the aluminum alloy plates of the above examples and comparative examples, and a bending portion rubbing test as described below was performed. .
First, the test piece was left to stand in an environment of 30 ° C. × 90% relative humidity for 24 hours, and then bent at an angle of 180 ° so that the brazed coating layer side was the outside and the bending portion inner diameter was 1 mm. Using a volatile oil impregnated felt, the apex of the bent portion was subjected to 10 reciprocating rubbing treatments with a load of about 1 kg.
And, similarly to the above-mentioned evaluation of adhesion, the peeling state of the brazed coating layer from the aluminum alloy base material in the bent portion is visually observed, and the length of the peeling portion relative to the length of the rubbing target portion is confirmed. In addition, the following evaluation criteria were used.
(1) ○: No peeling was observed at the rubbing target portion of the bent portion.
(2) Δ: Peeling was observed at a part of the rubbing target portion of the bent portion.
(3) x: Peeling was observed in the entire portion to be rubbed in the bent portion.

(Brazing)
Using the brazing paint of each composition shown in Table 1 below, using the same method as in the above production process, aluminum alloy sheets having the following specifications were produced in the Examples and Comparative Examples shown in Table 1. Obtained for each condition.
(A) Alloy: A3003 / A4343
(B) Plate thickness: 0.25 mm
(C) Cladding ratio: Brazing paint (brazing coating layer) ... 10% (both sides), core material (aluminum alloy base material) ... 80%
(D) Tempering: H14

Thus, as shown in FIG. 2, the aluminum alloy plate was bent and processed by joining both ends, and a hollow flat tube was produced for each aluminum alloy plate condition shown in Table 1.
And the tube material obtained by the said method was attached to the radiator (heat exchanger) as shown in FIG. 3, the brazing process was performed, and the fin joining rate to a tube was investigated. At this time, A3003 bare material (0.1 mmt) was used as the fin.
Further, the fin bonding rate (%) was obtained by the following equation (1).
(Wax formation area / Installation area of tubes and fins) × 100 (1)
The brazeability of each sample was evaluated from the fin joint rate obtained by the above equation (1). Generally, the joining rate is good at 90% or more, and it is judged as bad when it is 80% or less.

  A list of production conditions and evaluation test results for each example and comparative example is shown in Table 1, the components of the silane coupling agent are shown in Table 2, and the components of the additive are shown in Table 3.

  As shown in Table 1, the aluminum alloy brazing coating material obtained by applying the aluminum alloy brazing coating material having the component composition defined in the present invention to the aluminum alloy material has a good adhesion evaluation of ◯ or Δ ( Examples 11 and 19), which showed good adhesion. Moreover, the evaluation of brazing property shows very good brazing properties as 73 to 99%, and the evaluation of moisture resistance is all excellent or good (Examples 11, 16 and 19). showed that.

On the other hand, in Comparative Example 1 in which no silane coupling agent was added, the evaluation of brazing was as good as 99%, but both the adhesion and moisture resistance were evaluated as x.
Further, in Comparative Example 2 in which a silane coupling agent was not added and a cross-linking agent mainly composed of dialdehyde was added, the evaluation of brazing was relatively good at 95%, but the adhesion and moisture resistance. The evaluation of was both x.
Moreover, in Comparative Example 3 in which an organic titanium coupling agent mainly composed of titanium acetylacetonate was added without adding a silane coupling agent, the evaluation of adhesion and moisture resistance was good with ○, The evaluation of brazability was as extremely low as 63%.

  Based on the above results, the brazing aluminum alloy plate formed with the brazing coating layer made of the aluminum alloy brazing coating material having excellent coating film peel resistance according to the present invention can be used in any brazing material or flux. It has been clarified that the brazing coating layer containing can be prevented from peeling from the aluminum alloy base material and is excellent in brazing properties.

It is sectional drawing which shows an example of the aluminum alloy board for brazing to which the coating material for aluminum alloy brazing excellent in the coating-film peeling resistance of this invention was apply | coated, and the brazing coating-film layer was formed. 1 shows an example of a tube (aluminum alloy member for an automobile heat exchanger) made of an aluminum alloy plate for brazing, to which an aluminum alloy brazing paint excellent in peel resistance of the present invention is applied and a brazing coating layer is formed. It is a perspective view. It is a perspective view which shows an example of the radiator (automobile heat exchanger) using the tube (aluminum alloy member for motor vehicle heat exchangers) which consists of an aluminum alloy plate for brazing of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Aluminum alloy plate for brazing, 1a ... One side, 1b ... Other side, 2 ... Aluminum alloy base material, 2a ... One side, 2b ... Other side, 3 ... Brazing coating layer (aluminum alloy brazing coating material), DESCRIPTION OF SYMBOLS 10 ... Tube, 10a ... Distribution hole, 20 ... Radiator (automobile heat exchanger), 21 ... Header, 22 ... Fin

Claims (7)

  Aluminum alloy excellent in coating film peeling resistance characterized by containing flux powder, acrylic resin binder and silane coupling agent, blending brazing material powder as required, and the balance being solvent Brazing paint.   The organic functional group of the silane coupling agent is any one of amino, diamino, epoxy, vinyl, methacryloxy, acryloxy, isocyanate, or a functional group in which two or more of these are combined. The paint for brazing an aluminum alloy having excellent peel resistance according to claim 1. The acrylic resin binder is
(A) methacrylic acid alkyl ester monomer,
(B) an acrylic acid alkyl ester monomer,
(C) It consists of an acrylic resin obtained by copolymerizing each of ethylenically unsaturated monomers containing a hydroxyl group, and the weight ratio (a) :( b) :( c) of these monomers is 3. The coating composition for brazing of an aluminum alloy excellent in coating film peeling resistance according to claim 1 or 2, wherein the coating ratio is in the range of 93: 2: 5 to 55:15:30.   4. The aluminum alloy brazing paint excellent in coating film peel resistance according to claim 1, wherein water is added as a hydrolysis accelerator for the silane coupling agent.   A brazed coating layer made of an aluminum alloy brazing coating material having excellent coating film peel resistance according to any one of claims 1 to 4 is formed on at least one surface of an aluminum alloy substrate. An aluminum alloy plate for brazing characterized by the above.   The aluminum alloy member for motor vehicle heat exchangers using the aluminum alloy plate for brazing of Claim 5.   An automobile heat exchanger using the aluminum alloy member for an automobile heat exchanger according to claim 6.

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