JP4856846B2 - Resin-coated aluminum flat multi-hole tube for automobile heat exchanger excellent in brazing and method for producing the same - Google Patents

Description

  The present invention relates to an aluminum flat multi-hole pipe coated with a metal powder-containing coating material for brazing an aluminum material used for brazing an aluminum material, that is, a material made of an aluminum alloy. More specifically, resin-coated aluminum flats for automotive heat exchangers coated with a metal powder-containing paint for brazing that is suitable for brazing when heat exchangers such as automotive aluminum alloy evaporators, condensers, and radiators are joined and assembled. The present invention relates to a multi-hole tube and a manufacturing method thereof.

Brazing joining of an aluminum heat exchanger for automobiles such as a condenser is usually performed by assembling an aluminum extruded flat multi-hole tube and a brazing sheet in which an Al-Si brazing material is clad into an aluminum material into a predetermined joining shape. This is done by heating to the brazing temperature.
In this case, in order to perform sufficient bonding, it is necessary to destroy and remove the strong aluminum oxide present on the surface of the brazing filler metal surface of the extruded flat multi-hole tube and the aluminum brazing sheet. Alternatively, a brazing operation is performed after suspending in alcohol and spraying the brazed joint surface to evaporate the solvent.
In recent years, in order to omit the flux application operation immediately before brazing, a method of pre-coating a flux composition or a mixture of flux and brazing material on the surface of the material to be brazed (pre-coating) or pre-coating Patent Documents 1 to 5 and the like have been proposed for the application composition.

In addition, such pre-coating methods include coating methods such as spraying, dipping, and roll transfer methods. In these methods, the metal powder precipitates, so a composition with a constant composition ratio can be applied at high speed. Tend to be difficult. Therefore, in order to pre-coat the flux composition or the mixed composition of the flux and the brazing material continuously and at high speed with the roll transfer method uniformly with good transferability and adhesion, the kind of the synthetic resin in the composition and the composition Patent Document 6 proposes a brazing composition in which the weight ratio of the flux and brazing filler metal to the synthetic resin is specified, and the properties of the organic solvent and the coating viscosity are specified.
However, when such a coating composition and a brazing composition having a coating property are applied by a normal roll transfer method, it cannot be uniformly and continuously precoated at a high transferability and adhesion at a constant composition ratio. A resin-coated aluminum flat multi-hole tube in which the above composition was stably coated was not obtained.
JP-A-3-35870 JP-A-6-285681 JP-A-6-504485 Japanese Patent No. 2681380 Japanese Patent No. 2681389 Japanese Patent Laid-Open No. 11-239867

  The present invention provides a continuous and high-speed roll coating method for coating a paint containing metal powder such as brazing flux and brazing material on the surface of an aluminum extruded flat multi-hole tube used in an aluminum heat exchanger for automobiles such as a condenser. In order to precoat with good uniformity and adhesion, various researches were repeated on the composition, the average particle size and density of the metal powder in the composition, the surface roughness of the aluminum flat multi-hole tube, and the coating method of the roll coater. The object of the present invention is to provide an aluminum flat multi-hole tube for an automobile heat exchanger having good uniformity and adhesion of the coating film and sufficient brazing adhesion, and a method for producing the same. There is.

The features of the resin-coated aluminum flat multi-hole pipe for automobile heat exchangers that are excellent in brazing properties and coating film adhesion after oil immersion according to the present invention are characterized by brazing flux (hereinafter referred to as flux), brazing material, and the like. Metal powder for brazing, acrylic resin and cross-linking agent, and metal powder volume content (volume% of metal powder in the total amount (solid content) of metal powder, acrylic resin and cross-linking agent) 50% to 90% of brazing metal powder-containing resin paint, center line average roughness (Ra) is 0.4 μm or more and ten-point average roughness (Rz) is 3 μm or more for at least one flat surface In other words, the roughened surface of an aluminum flat multi-hole pipe whose surface roughness is adjusted is coated.
In addition, the feature of the method for producing a resin-coated aluminum flat multi-hole tube for an automobile heat exchanger according to the present invention is that, after supplying a coating material containing a metal powder for brazing by a top feed method and coating by a reverse method, It is to dry. The metal powder contained in the brazing metal powder-containing resin coating preferably has an average particle size of 20 μm or less and a density of 4.0 Mg / m ³ or less.

  The resin-coated aluminum flat multi-hole tube of the present invention is excellent in adhesion and brazing, and is suitably used for an automotive heat exchanger. Further, according to the method for producing a resin-coated aluminum flat multi-hole tube of the present invention, a resin-coated aluminum flat multi-hole tube having a high content of metal powder, a uniform distribution over the entire surface, and excellent brazing properties. Can be manufactured.

The present invention is described in detail below.
The brazing metal powder-containing resin coating in the present invention contains a flux alone or a mixture of a flux and a brazing material as a brazing metal powder , an acrylic resin and a crosslinking agent as a binder, and water and an organic solvent. The brazing metal powder and the acrylic resin and crosslinking agent as a binder are made into a paint with water and an organic solvent. The content of the acrylic resin in the brazing metal powder-containing resin ( solid content of the paint obtained by adding the brazing metal powder, the acrylic resin, and the crosslinking agent) is preferably 10 to 20% by mass, and contains the crosslinking agent. The amount is preferably 0.3-2% by weight. It is not particularly limited amount of water and an organic solvent agent for paint, preferably 100 to 200 wt% relative to the solids.
The fluxes is reduced a strong aluminum oxide film on the surface of the aluminum member is required to _{remove, KF, AIF 3, KAIF 4} , KAIF 5, K 2 AIF 5, K 3 AIF 5, Fluoride fluxes such as CsF, RbF, LiF, NaF, Ca ₂ F, and KZnF ₃ , or those containing these as main components can be used.

As the brazing material, metals that form a eutectic alloy with aluminum during brazing, such as Si, Zn, Cu, and Ge, can be used. Also, alloys of these metals and aluminum that form a eutectic alloy with aluminum during brazing can be used, and one or more of these metals and alloys can be applied.
As a binder over uses those comprising acrylic resin and a crosslinking agent. As the acrylic resin, there is a polymer such as polymethacrylate. Examples of the crosslinking agent include blocked isocyanate and oxazoline group-containing polymer. These binders volatilize at the brazing temperature.

In the production of the resin-coated aluminum flat multi-hole tube in the present invention, the surface roughness of at least one flat surface of the aluminum flat multi-hole tube is adjusted, and the surface (roughened surface) whose surface roughness is adjusted is brazed. Surface coated with a three-roll roll coating of a brazing metal powder-containing resin coating containing a single powder or a mixture of flux and brazing filler metal (also referred to simply as a metal powder). Is performed by drying.
As for the surface roughness of the flat surface of the aluminum flat multi-hole tube, the center line average roughness (Ra) is 0.4 μm or more, and the ten-point average roughness (Rz) is 3.0 μm or more. Further, the center line average roughness (Ra) is preferably 0.6 μm or more, and the ten-point average roughness (Rz) is preferably 4.0 μm or more. When Ra is less than 0.4 μm or Rz is less than 3.0 μm, the surface roughness is not sufficient, the anchor effect cannot be expected, and the adhesion is poor. The upper limit of the surface roughness is not particularly limited, but when Ra and Rz are excessively large, there is a problem that the applicator roll is easily damaged during roll coater coating, and the frequency of roll replacement becomes high, which is not practical and economical. Occur. Accordingly, although not particularly limited, the upper limit is about 2 μm for (Ra) and about 10 μm for (Rz). As a method for obtaining a desired surface roughness, any method such as a method of roughening the surface of the material by blasting or a method of electrochemical etching may be used.

The metal powder in the paint preferably has an average particle size of 20 μm or less and a density of 4.0 Mg / m ³ or less. When the density exceeds 4.0 Mg / m ³ or when the average particle diameter exceeds 20 μm, when the top feed method is applied, relatively heavy particles are evenly applied to the surface of the material. Metal powder precipitates in the paint film. Near the surface of the coating film, the binder component is rich, and near the interface with the material, the metal powder is rich, and the brazing property is lowered. Preferred coating weight of the coating film after drying, when the metal powder contains only flux 3 to 20 g / ^{m 2,} if the metal powder comprises a flux and brazing material is 5 to 30 g / ^{m 2.}
As the three-roll coating method, the top feed method is preferable. FIG. 1 shows a schematic diagram of the top feed system. In the figure, symbol a is an arrow indicating the rotation direction of the roll, and symbol b is an arrow indicating the direction in which the flat multi-hole tube (coil) travels. Note that corresponding parts in other subsequent drawings are denoted by the same reference numerals. In FIG. 1, the coating material 5 supplied from above between the metering roll 1 and the pickup roll 2 is transferred to the applicator roll 3, and roll coated on the flat surface of the flat multi-hole tube 6 with the applicator roll. As shown in the figure, according to the top feed system, a coater pan is not required and the paint is not accumulated, so that the metal powder does not precipitate and the paint containing the metal powder at a high concentration can be stably applied. By applying this method, it is possible to produce a resin-coated aluminum flat multi-hole tube for an automotive heat exchanger that is excellent in brazing, which is an object of the present invention. In addition, this top feed system has natural coating (the rotation direction of the applicator roll is the same as the transfer direction of the flat multi-hole tube) and reverse coating (the rotation direction of the applicator roll is opposite to the transfer direction of the flat multi-hole tube). Although reverse coating is preferred. Natural coating tends to deteriorate the appearance of the coating and as a result, the uniformity of the coating film is impaired and the brazing property tends to decrease. In the present invention, the coating is applied by the above method and then dried by a conventional method. Drying is preferably performed at 100 to 200 ° C., which is the maximum temperature (PMT) that the flat multi-hole tube reaches when passing through the drying facility.

Hereinafter, the present invention will be described in more detail based on examples and comparative examples. However, the present invention is not limited to the examples.
<Invention Examples 1-7 and Comparative Examples 1-4>
One flat plane of a flat multi-hole tube (19 holes, width 16 mm, height 1.8 mm, hole size 1.0 mm × 0.6 mm, wall thickness 0.3 mm) made of A1050 aluminum alloy extruded by the conform extrusion method adjust the surface roughness, in brazing metallic powder-containing resin coating, top feed as shown in Figure 1 - coated flat multihole pipe coil by a reverse 3 roll method. Various conditions at this time are shown in Table 1. Subsequently, a normal baking process is performed (PMT: 150 ° C.), and the coating powder in which the metal powder is only the flux is 5.0 g / m ² of the dry coating film, and the coating powder in which the metal powder includes the flux and the brazing material A metal powder-containing resin layer having a dry coating film adhesion amount of 10.0 g / m ² was formed. As the resin component, a resin component containing 1.5% by mass of an oxazoline group-containing polymer as a crosslinking agent with respect to 98.5% by mass of an acrylic resin was used. The ratio of the metal powder and the resin component in the paint was adjusted so that the metal powder volume content in the solid content would be the amount shown in Table 1 below.

The adhesion and brazing properties of the obtained resin-coated aluminum flat multi-hole tube were evaluated by the following methods. The results are shown in Table 1.
Adhesiveness (1): About the obtained resin-coated aluminum flat multi-hole tube, the pencil hardness at which the coating film peeled was examined based on the pencil scratch test method according to JIS K 5400.
Adhesion (2): The obtained resin-coated aluminum flat multi-hole tube was immersed in a processing oil (Titan Press: Toyoda Chemical Engineering Co., Ltd.) for one week, and a pencil scratch test of JIS K 5400 was performed as described above. Pencil hardness was measured.
Brazing property: The obtained resin-coated aluminum flat multi-hole tube and aluminum brazing sheet (BS. Thickness 70 μm, core material: A3103 alloy, skin material: A4045 alloy) or A3003 aluminum alloy plate are formed in a meandering shape. A corrugated member (corrugated fin) was brought into contact and brazed and held at 600 ° C. for 3 minutes in a nitrogen gas atmosphere to evaluate brazing. The evaluation of brazing was performed by brazing and bonding with corrugated fins, then peeling off the fins and measuring the adhesion rate of the fins.

<Invention Examples 8-14 and Comparative Examples 5-10>
An aluminum alloy flat multi-hole tube coil is coated by the method shown in Table 2 and the paint in which the metal powder is only flux consists of a dry coating film of 10.0 g / m ² , and the metal powder is composed of flux and brazing material. The coating material formed the metal powder containing resin layer of the adhesion amount 20.0g / m < ² > of a dry coating film. At this time, the flux added to the paint, the kind and amount of the brazing material, the flux contained in the resin layer and the content of the brazing material are shown in Table 2. The sample was taken at 30 minutes after the start of painting. In this series, the effect of changing the paint transfer method was investigated. The various transfer methods employed are shown in FIGS. 1, 2, 3 and 4. FIG. The adhesion and brazing properties of the resulting resin-coated aluminum flat multi-hole tube were evaluated by the same methods as in Examples 1 to 7 of the present invention. The results are shown in Table 2. As can be seen from the results in Table 2, a resin layer containing a high concentration of flux and brazing material can be stably obtained by top feed-reverse coating, whereas flux can be soldered in a short time by bottom-up-reverse coating. Since the material settles down in the coater pan 4, a resin layer having a stable flux and brazing filler content could not be obtained in the case of long-time coating. In addition, the top feed-natural coating has an effect on the precipitation of the metal powder, but a pattern is seen with respect to the appearance of the coating film, and the distribution of the metal powder is not uniform.

From the above results, the resin-coated aluminum flat multi-hole tube as an example of the present invention is excellent in adhesion and brazing, and according to the production method of the present invention, such adhesion and brazing. It is possible to obtain a resin-coated aluminum flat multi-hole tube with excellent resistance. Inventive Examples 11 to 14 have a relatively large average particle size or density of the metal powder, and therefore have slightly lower brazing properties than Inventive Examples 8 to 10.
In contrast, Comparative Example No. Among Nos. 1 to 10, Nos. 1, 2, 3 and 4 had poorer adhesion than the examples of the present invention because the surface roughness of the flat surface of the aluminum flat multi-hole tube was small. No. 2-a has a metal powder content too low and is inferior in brazability. 2-b is inferior in adhesiveness because the metal powder content is too high. No. 6-8 and no. In No. 10, since the coating was supplied in a bottom-up manner, precipitation of metal powder was observed in the coater pan, the metal powder content in the resin layer was insufficient, and sufficient brazing properties were not obtained. No. Since 5 and 9 were roll-transferred by the natural method, the distribution of the metal powder in the coating film was not uniform, and the brazing property was inferior.

It is a schematic diagram of the 3 roll coating method by a top feed-reverse system. It is a schematic diagram of the 2 roll coating method by a top feed-natural system. It is a schematic diagram of the 2-roll coating method by a bottom-up-reverse system. It is a schematic diagram of the 3 roll coating method by a bottom-up-natural system.

Explanation of symbols

1 Metering roll 2 Pickup roll 3 Applicator roll 4 Coater pan 5 Paint 6 Flat multi-hole tube (coil)
a Arrow indicating the rotation direction of the roll b Arrow indicating the traveling direction of the flat multi-hole tube (coil)

Claims (3)

A brazing metal powder-containing resin coating comprising a brazing metal powder including a flux and a brazing material , an acrylic resin, and a cross-linking agent, and having a metal powder volume content in a solid content of 50% to 90%. The roughened surface of an aluminum flat multi-hole tube whose surface roughness is adjusted so that the center line average roughness (Ra) is 0.4 μm or more and the ten-point average roughness (Rz) is 3 μm or more for at least one flat surface. to characterized in that uncoated cured in brazeability, after oil immersion coating adhesion JIS K 5400 pencil scratch test according to a pencil hardness at which automobile heat exchanger resin-coated aluminum flat multi B~2H by Hole tube. Roughening surfaces of the aluminum flat multihole tube the braze metal powder-containing resin, characterized by being coated with 3 to 30 g / m ² as an adhesion amount after drying, No placement claim 1 Symbol Resin-coated aluminum flat multi-hole tube for automotive heat exchangers with excellent brazing and coating adhesion after oil immersion. The brazing metal powder has an average particle size of 20 μm or less, a density of 4.0 Mg / m ³ or less, and the top of the coating of the brazing metal powder-containing resin formed into a paint with water and an organic solvent. 3. A resin coating for an automotive heat exchanger having excellent brazing and coating adhesion after oil immersion according to claim 1 or 2 , wherein the coating is dried after being fed by a feed method and coated by a reverse method. Manufacturing method of aluminum flat multi-hole tube.

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