Aluminum member and heat exchanger provided with hydrophilic coating film

Abstract

To provide an aluminum member and a heat exchanger provided with a hydrophilic coating film.SOLUTION: An aluminum member is provided with a hydrophilic coating film, wherein the aluminum member includes, in mass%, Mn: 0.5 to 2.0%, Zn: 0.4 to 4.0%, and Cu: 0.001 to 0.2%, has a base material of an aluminum alloy composed of aluminum and the balance being unavoidable impurities, and has a coating film disposed on one or both surfaces of the base material, the coating film containing a boron compound and a hydrophilic polymer, having a SiO2 content of 49% or less and a surface roughness Rz of 1.5 μm or less. It is preferable that the hydrophilic polymer includes one or more selected from polyvinyl alcohol (PVA), polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, and water-soluble acrylic resins.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an aluminum member provided with a hydrophilic coating film and a heat exchanger.

Background Art

[0002] In building air conditioners and the like, heat exchangers in which a copper tube and an aluminum fin are mechanically joined are widely used. When such a heat exchanger is used as an evaporator, there is a problem that the condensed water adhering to the fins is not drained, the ventilation resistance increases, and the heat transfer performance of the heat exchanger deteriorates.

[0003] For example, as a technique for precoating a hydrophilic film, Patent Document 1 below discloses a precoated fin having a coating film on the surface of an aluminum alloy plate containing 1 to 5% by mass of Si, and the Si amount in the coating film is 1 to 300 mg / m 2 This coating film contains at least one of silicate such as lithium silicate and amorphous silica, and further contains a fluoride flux.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, in order to improve the heat transfer performance, heat exchangers in which an aluminum tube and a fin are metal-bonded by brazing heat treatment have been developed, and in such heat exchangers as well, improvement in the drainage property of condensed water is similarly required. By using water glass for the hydrophilic film, the hydrophilicity after brazing can be maintained. However, when performing brazing heat treatment around 600 °C, water glass may react with the flux and cause discoloration on the fin surface. In addition, when used as a fin material for heat exchangers, peeling due to fin corrosion may occur if the potential is not suitable in terms of corrosion resistance, and problems may occur in terms of formability if the tensile strength is not suitable.

[0006] To solve this problem, the inventor of the present invention forms a hydrophilic film composed of a boron compound and a hydrophilic polymer on the surface of the base material (fin), so that the water contact angle on the fin surface is significantly reduced, and the attached condensed water can be easily drained. It has been found that excellent performance can be exhibited in both corrosion resistance and formability by optimizing the Zn content and Mn content in the base material. In addition, since the boric acid compound constituting the present hydrophilic film is an inorganic material, the film remains even after brazing heat treatment and exhibits excellent hydrophilicity. Therefore, the drainage property of the fins can be improved even in a heat exchanger in which the fins and the tubes are joined by brazing heat treatment.

[0007] An object of the present invention is to provide an aluminum member and a heat exchanger provided with a hydrophilic coating film capable of improving the drainage property of condensed water regardless of whether the copper tube or the aluminum tube described in the previous description is used.

Means for Solving the Problems

[0008] (1) The aluminum member provided with the hydrophilic coating film according to this embodiment contains Mn: 0.5 to 2.0%, Zn: 0.4 to 4.0%, Cu: 0.001 to 0.2% by mass%, and the balance is an inevitable impurity and an aluminum alloy base material made of aluminum, and contains a boron compound and a hydrophilic polymer, and SiO 2 It is characterized in that a coating film having a content of 49% or less and a surface roughness Rz of 1.5 μm or less is provided on one side or both sides of the base material. (2) In the aluminum member provided with the hydrophilic coating film according to this embodiment, it is preferable that the hydrophilic polymer contains one or more of PVA (polyvinyl alcohol), polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, and water-soluble acrylic resin.

[0009] (3) In the aluminum member provided with the hydrophilic coating film according to this embodiment, it is preferable that the antibacterial activity value of the coating film is 2.0 or more. (4) In the aluminum member provided with the hydrophilic coating film according to any one of (1) to (3) of this embodiment, it is preferable that the film thickness of the coating film is 25 nm or more and 2000 nm or less. (5) In the aluminum member provided with the hydrophilic coating film according to any one of (1) to (4) of this embodiment, as a fluxing agent for improving the brazing property, it is preferable that the coating film contains a fluorine compound containing any one or more of alkali metal, boron, aluminum, silicon, zinc, titanium, and zirconium.

[0010] (6) In the aluminum member provided with the hydrophilic coating film according to any one of (1) to (5) of this embodiment, it is preferable that the tensile strength is 170 MPa or more and 200 MPa or less and the formability is excellent. (7) In the aluminum plate provided with the hydrophilic coating film according to any one of (1) to (6) of this embodiment, it is preferable that the potential is -910 mV or more and -730 mV or less and the corrosion resistance is excellent. (8) The heat exchanger according to this embodiment is characterized in that fins are formed from the aluminum member provided with the hydrophilic coating film according to any one of (1) to (7).

Advantages of the Invention

[0011] According to the present invention, it contains a boron compound and a hydrophilic polymer, and SiO 2Since the coating film has a content of 49% or less and a surface roughness Rz of 1.5 μm or less and is provided on a substrate of an aluminum alloy having a specific composition, excellent hydrophilicity can be obtained even after brazing heating at about 600° C. while preventing damage to the coating device, and an aluminum member can be provided that does not cause appearance defects after brazing and does not cause a decrease in productivity. Further, if it is a heat exchanger including fins, tubes, or header manifolds made of the aluminum member, a heat exchanger having excellent hydrophilicity, good productivity, and no appearance defects after brazing heating can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an example of an embodiment of the present invention will be described in detail based on the accompanying drawings. Note that the drawings used in the following description may show, for the sake of clarity, the characteristic parts enlarged for convenience.

[0014] 「First Embodiment」 FIG. 1 is a front view showing an example of a heat exchanger configured using fins formed from an aluminum plate according to the present embodiment. The heat exchanger 30 in this example is an aluminum heat exchanger used for applications such as heat exchangers for indoor and outdoor units of room air conditioners, outdoor units for HVAC (Heating Ventilating Air Conditioning), and heat exchangers for automobiles. The heat exchanger 30 shown in Fig. 1 mainly includes header manifolds 31 and 32 arranged in parallel to the left and right with a gap therebetween, a plurality of tubes 33 arranged in parallel while maintaining a distance from each other between these header manifolds 31 and 32 and joined to the header manifolds 31 and 32 at substantially right angles, and corrugated fins 34 attached to each tube 33. The header manifolds 31 and 32, the tubes 33, and the fins 34 are all made of a base material of aluminum or an aluminum alloy.

[0015] More specifically, a plurality of slits 36 are formed at predetermined intervals in the longitudinal direction of each pipe on the opposing side surfaces of the header manifolds 31 and 32, and the ends of the tubes 33 are inserted into the opposing slits 36 of these header manifolds 31 and 32, and a plurality of tubes 33 are installed between the header manifolds 31 and 32. Also, corrugated fins 34 are arranged between the plurality of tubes 33 and 33 installed at predetermined intervals between the header manifolds 31 and 32, and these fins 34 are brazed to the upper surface 33A side or the lower surface 33B side of the tube 33 as shown in Fig. 2, for example.

[0016] As shown in Fig. 2, in the portion where the end of the tube 33 is inserted into the slit 36 of the header manifold 31, a first fillet 38 is formed by a brazing material so as to fill the gap of the insertion portion, and the tube 33 is brazed to the header manifolds 31 and 32. Also, in the corrugated fin 34, a second fillet 39 is formed by the brazing material generated in the portion between the upper surface 33A or the lower surface 33B of the adjacent tube 33 adjacent to the top of the wave, and the corrugated fins 34 are brazed to the upper surface 33A side and the lower surface 33B side of the tube 33, respectively. The tube 33 is a flat multi-hole tube made of an aluminum alloy, and a plurality of refrigerant passages 33C are formed inside thereof.

[0017] As shown in FIG. 3, the heat exchanger 30 of the present embodiment is manufactured by assembling header manifolds 31 and 32, a plurality of tubes 33 installed between them, and a plurality of fins 34 to form a heat exchanger assembly 41, and heating and brazing this. Note that Zn diffusion layers 42 shown in FIG. 2 are formed on the upper surface 33A side and the lower surface 33B side of the tube 33 by heating during brazing.

[0018] The aluminum alloys constituting the header manifolds 31 and 32 are made of aluminum alloys applied to general heat exchanger header manifolds. For example, an aluminum alloy based on the Al-Mn system is applied. For example, it is preferably contained Mn: 0.05 to 1.50% by mass%, and as other elements, Cu: 0.05 to 0.80% can be contained. In the following description, when ranges such as components and coating amounts are indicated using "~", unless otherwise specified, it means a range including the upper and lower limits. Therefore, for example, 0.05 to 1.50% means 0.05% or more and 1.50% or less, and 1 to 5 g / m 2 means 1 g / m 2 or more and 5 g / m 2 or less. In the present embodiment, the header manifolds 31 and 32 are those in which a brazing material layer is formed on the outer surface of a pipe-shaped core material made of the above-described aluminum alloy. In FIGS. 2 and 3, the core material is indicated by reference numeral 31A, and the brazing material layer is indicated by reference numeral 43.

[0019] The tube 33 is a flat tube having a large ratio of width to thickness, and a plurality (several to several tens) of refrigerant passages 33C are formed adjacent to each other in a state partitioned by partitions in the width direction of the tube 33. The aluminum alloy constituting the tube 33 is not particularly limited as long as it is an aluminum alloy applied to flat multi-hole tubes for heat exchangers or tubes. As an example, it consists of an aluminum alloy containing, by mass%, Mn: 0.1 to 1.50%, Cu: 0.05 to 0.2%, Si: 0.05 to 1.0%, with the balance being inevitable impurities and aluminum. The tube 33 is produced by extruding the aluminum alloy. The number of refrigerant passages 33C formed in the tube 33 may be any number as long as it is one or more, but a structure in which a plurality of refrigerant passages 33C are formed is preferable in terms of improving heat exchange efficiency.

[0020] The aluminum alloy constituting the fin 34 can widely apply general aluminum alloys used for fins of heat exchangers. For example, it consists of an aluminum alloy containing, by mass%, Mn: 0.5 to 2.0%, Zn: 0.4 to 4.0%, Cu: 0.001 to 0.2%, with the balance being inevitable impurities and aluminum. The fin 34 is obtained by melting an aluminum alloy having the above composition by a conventional method, manufacturing a plate-shaped or sheet-shaped fin material (substrate) through a hot rolling process, a cold rolling process, etc., forming a hydrophilic coating film 35 on both the front and back surfaces of the fin material, and then processing it into a target fin shape, such as a corrugated shape. Note that the manufacturing method of the fin 34 is not particularly limited, and known manufacturing methods can be appropriately adopted.

[0021] Hereinafter, the reasons for limiting the components according to this embodiment will be described. <Elements contained in the aluminum alloy constituting the fin 34> · Mn: 0.5 to 2.0% Mn is added to precipitate Al-Mn-Si-based intermetallic compounds and obtain the strength after brazing by dispersion strengthening. When the amount of Mn is less than 0.5%, the effect of dispersion strengthening by Al-Mn-Si-based compounds is small, and the desired strength after brazing cannot be obtained. Also, when the amount of Mn added exceeds 2.0%, large Al-Mn-based intermetallic compounds crystallize during the casting of the ingot, raising concerns about breakage during rolling. Moreover, the solid solubility in the matrix increases and the solidus temperature (melting point) decreases, and there is a case where the fins melt during brazing, which is not preferable. Therefore, the content of Mn is within the above range.

[0022] ·Zn: 0.4 - 4.0% Zn has the effect of solid-solubilizing in the Al matrix and lowering the potential, and is added to obtain the sacrificial anode effect of the fins. However, when the amount is less than 0.4%, the effect of lowering the potential is small, the desired sacrificial anode effect cannot be obtained, and the erosion depth of the combined tubes increases. On the other hand, when it exceeds 4.0%, the potential becomes excessively low, and the self-corrosion resistance of the fins decreases, which is not preferable. Therefore, the content of Zn is within the above range. ·Cu: 0.001 - 0.2% Cu either solid-solubilizes in the Al matrix or exists as an Al-Cu-based compound. When the amount of Cu is less than 0.001%, the contribution to the strength after brazing by solid solution strengthening is small. On the other hand, when the amount of Cu is 0.2% or more, θ-CuAl2 stable phase or θ'-CuAl2 metastable phase with a nobler potential than the matrix exists as a compound, which serves as a corrosion initiation point and reduces the corrosion resistance, which is not preferable. Therefore, the content of Cu is within the above range.

[0023] <Elements Contained in the Aluminum Alloy Constituting Tube 33> ·Si: 0.01 - 0.5% Si is added to precipitate Al-Mn-Si-based intermetallic compounds and obtain the strength after brazing by dispersion strengthening. If the Si addition is less than 0.01%, the effect of dispersion strengthening by the Al-Mn-Si-based compound is small, and the desired strength after brazing cannot be obtained. Also, if Si is added in excess of 0.5%, the solid solubility in the matrix increases, the solidus temperature (melting point) decreases, and fins may melt during brazing, which is not preferable. Therefore, the content of Si is set within the above range.

[0024] In the present embodiment, as shown in FIG. 3, on the upper and lower surfaces of the tube 33 before brazing, as an example, Si powder: 1 to 5 g / m 2 , Zn-containing flux (KZnF 3 powder, etc.): 3.0 to 20 g / m 2 , and resin: 0.2 to 8.3 g / m 2 are included, and a brazing coating film 37 containing a solvent added thereto is formed.

[0025] The fin (aluminum member) 34 has a plate-like base material 34a made of aluminum or an aluminum alloy, and a hydrophilic film 35a attached to the front and back surfaces (both the front and back surfaces) of the base material 34a. That is, hydrophilic films 35a are provided on both the front and back surfaces of the base material 34a after the brazing heat treatment. Note that the hydrophilic film 35a may be simply referred to as the film 35a for simplicity of description. The base material 34a constituting the fin 34 preferably has a tensile strength of 170 MPa or more and 200 MPa or less. If the tensile strength is less than 170 MPa, there is a risk that the fin may not maintain its shape due to the self-weight of the core when the core is assembled into the heat exchanger. If the tensile strength exceeds 200 MPa, the springback amount becomes large, and there is a possibility of causing problems in formability. Also, the potential of the base material 34a is preferably -910 mV or more and -730 mV or less. With a potential within this range, the fin 34 with excellent corrosion resistance can be obtained.

[0026] <Hydrophilic coating film> In the heat exchanger assembly 41 before brazing heat treatment shown in FIG. 3, a hydrophilic coating film 35 according to the present embodiment is formed on the front and back surfaces (both front and back surfaces) of the fins 34. Note that the hydrophilic coating film 35 may be simply referred to as a coating film 35 for brevity. The heat exchanger assembly 41 corresponds to the heat exchanger before brazing, and is assembled by assembling the left and right header manifolds 31 and 32, the tubes 33, and the fins 34 so as to have the general shape shown in FIG. 1. By heating this heat exchanger assembly 41 to the brazing heat treatment temperature as described later, the heat exchanger 30 shown in FIG. 1 can be obtained. Note that the coating film 35 may be formed on only one of the front and back surfaces of the fins 34, that is, on one side.

[0027] The coating film 35 formed on the fins 34 of the heat exchanger assembly 41 is obtained by applying the hydrophilic paint composition described below to form a paint layer, and drying this paint layer at 200 to 260 ° C., for example, 250 ° C. for about 0.2 to 5 minutes to volatilize the solvent, and having a coating amount of 0.03 to 1.8 g / m 2 This is the coating film obtained in such a manner. When the coating amount after drying of the paint layer is less than 0.03 g / m 2 There is a possibility that sufficient hydrophilicity cannot be obtained in the film 35a after brazing. Further, when the coating amount after drying exceeds 1.8 g / m 2 The brazing property deteriorates, and there is a possibility that a joining failure occurs during brazing.

[0028] The hydrophilic paint composition used in the present embodiment is a hydrophilic paint composition containing a boron compound and a hydrophilic polymer (compound) in a solvent.

[0029] "Hydrophilicity-imparting component" In this embodiment, the hydrophilic paint composition contains a boron compound as a hydrophilic imparting component. The boron compound is one or more of lithium borate, sodium borate, potassium borate, calcium borate, barium borate, ammonium borate, lithium metaborate, sodium metaborate, calcium metaborate, barium metaborate, ammonium metaborate, lithium tetraborate, sodium tetraborate, calcium tetraborate, barium tetraborate, and ammonium tetraborate. In this embodiment, the hydrophilic paint composition contains, in addition to the boron compound as a hydrophilic imparting component, the following hydrophilic polymer (compound). The hydrophilic polymer (compound) preferably contains one or more of PVA (polyvinyl alcohol), PEG (polyethylene glycol), CMC (carboxymethyl cellulose), HEC (hydroxyethyl cellulose), HPMC (hydroxypropyl methylcellulose), MC (methylcellulose), polyacrylic acid, polyacrylate, polyamic acid, polyamic acid salt, polymethacrylic acid, polymethacrylate, and water-soluble acrylic resin. In the hydrophilic paint composition, the hydrophilic imparting component is contained, for example, in an amount of about 0.1 to 5% by mass in the hydrophilic paint composition as a solid content. When the content of the hydrophilic polymer is small, sufficient hydrophilicity maintenance cannot be obtained.

[0030] "Rheology modifier" The hydrophilic paint composition can contain, for example, a rheology modifier in an amount of about 0.02 to 3% by mass. Specifically, as the rheology modifier, one or more of synthetic or natural swellable layered mineral particles (hectorite, vermiculite, halloysite, swellable mica, etc.), ultrafine oxide particles (alumina, titania, zirconia, etc.), PVP, water-soluble cellulose derivatives, and cellulose nanofibers can be selected and used.

[0031] "Surfactant" The hydrophilic paint composition can contain, for example, a surfactant in an amount of about 0.01 to 1% by mass. As surfactants, specifically, as anionic surfactants, one or more selected from carboxylates, sulfonates, sulfate esters, and phosphate esters can be applied. LAS known as alkylbenzene sulfonate, MES known as α-sulfo fatty acid methyl ester salt, or AOS known as α-olefin sulfonate can also be used. As the sulfate ester salt, AS of alkyl sulfate ester salt, or AES known as polyoxyethylene alkyl sulfate ester salt can also be used.

[0032] In addition, as cationic surfactants, benzalkonium salts, quaternary ammonium salts, or imidazoline compounds can be used. In addition, as nonionic surfactants, glycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, or polyoxyethylene polyoxypropylene glycols can also be used. Also, as amphoteric surfactants, alkyl betaines, fatty acid amide propyl betaines, or alkyl amine oxides can also be used. One or more of the above surfactants can be selected and used. The surfactant improves the wettability during coating and coating defects.

[0033] "Fluxing agent" The hydrophilic coating composition can contain, for example, about 0.01 to 1% by mass of a fluxing agent. The fluxing agent contains any one or more of fluorine compounds containing any one or more of alkali metals, alkaline earth metals, boron, aluminum, silicon, zinc, titanium, zirconium, and cesium. The fluorine compound is K 1-3 AlF 4-6 , Cs 1-3 AlF 4-6 , Cs 0.02 K 1-2 AlF 4-5 AlF3 , KF, KZnF 3 , K 2 SiF 6 , Li 3 AlF 6 , NaF, NaSiF 6 , KSiF 6 , MgF 2 , CaF 2 , CsF, NaBF 4 , KBF 4 , K 2 TiF 6 , and K 2 ZrF 6 Preferably, it is any one or more of them. Including a fluxing agent contributes to improving soldering properties, improving coating film adhesion, improving corrosion resistance, etc.

[0034] "Organic solvent or organic solvent + water" In the hydrophilic coating composition, the above-mentioned various components are contained in a solvent mainly composed of an organic solvent or an organic solvent + water. In this embodiment, the organic solvent is an alcohol or polyhydric alcohol-based organic solvent such as 4-methyl-2-pentanol, α-terpineol, 2-ethyl-1,3-hexanediol, an ether-based organic solvent such as 1,2-diethoxyethane, dibutyl ether, 1,2-dibutoxyethane, diphenyl ether, a ketone-based organic solvent such as acetone, 4-pentanone, cyclohexanone, diisobutyl ketone, methylcyclohexanone, an ester-based organic solvent such as butyl acetate, butyl propionate, dimethyl maleate, ethyl benzoate, a hydrocarbon-based organic solvent such as toluene, ethylcyclohexane, turpentine oil, n-dodecane, or an organic solvent having two or more functional groups such as 1-ethoxy-2-propanol, 2-phenoxyethanol. One or more of them can be used. In addition, as organic solvents that can be used even when water is added, ethanol, 1-propanol, 2-propanol, 1,4-dioxane, tert-butanol, hexanol, octanol, decanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, 1,4-butanediol, ethylene glycol dimethyl ether, dimethoxyethane, acetonitrile, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, 2-ethoxyethanol, 1-butanol, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, ethylene glycol monoisopropyl ether, 2-ethoxyethyl acetate, 2-methoxyethyl acetate, propylene glycol monopropyl ether, diacetone alcohol, dimethylaminoethanol, N,N-dimethylformamide, triethylene glycol dimethyl ether, 3-methoxy-1-butanol, ethylene glycol monoisobutyl ether, γ-butyrolactone, diethylene glycol methyl ethyl ether, 2-butoxyethanol, ethylene glycol monobutyl ether, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoisopropyl ether, ethylene glycol, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, tripropylene glycol monomethyl ether, glycerin, 2-aminoethanol, one or more of them can be used.

[0035] <Water-soluble lubricating layer> A water-soluble lubricating layer can be formed as a layer formed on the coating film of the hydrophilic paint composition. Examples of the water-soluble lubricant include nonionic polymers obtained by adding ethylene oxide to a compound selected from the group consisting of acrylic resins, epoxy resins, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl fatty acid amides, polyoxyethylene alkyl stearates, polyoxyethylene alkyl fatty acid esters, polyoxyethylene-12-hydroxystearate, polyoxyethylene trimethylolpropane alkyl fatty acid mono- or diesters, polyoxyethylene pentaerythritol alkyl fatty acid mono- or diesters, and polyoxyethylene polyoxyalkyl ethers.

[0036] It is desirable that a water-soluble lubricating layer is formed on the surface of the coating film 35. The coating amount of this water-soluble lubricating layer is desirably 0.05 to 1 g / m 2 . When the coating amount of the water-soluble lubricating layer is less than 0.05 g / m 2 , when the plate material is processed into corrugated fins, due to the friction with the mold, the fins are likely to be partially cracked. Also, when the coating amount exceeds 1 g / m 2 , during fin processing, cutting and feeding defects are likely to occur, and there is a risk of reduced brazing property. In the coating film 35, when the antibacterial activity value is less than 2.0, it cannot be regarded as having antibacterial properties.

[0037] In the heat exchanger assembly 41 shown in FIG. 3, brazing coating films 37 are formed on the upper surface 33A and the lower surface 33B of the tube 33, and the brazing coating films 37 can be melted by heating the heat exchanger assembly 41 at a temperature of about 580 to 620 °C for several minutes to several tens of minutes. After the heat treatment and cooling, as shown in FIG. 2, the tube 33 and the fins 34 are brazed by the first fillet 38 and the second fillet 39, and a heat exchanger 30 in which the tube 33 is brazed to the header manifolds 31 and 32 by the first fillet 38 can be obtained. The hydrophilic coating film 35 formed on the fin 34 before brazing becomes a hydrophilic film 35a after the brazing heat treatment and remains on the front and back surfaces of the fin 34.

[0038] When the brazing coating film 37 contains a Zn-containing flux, Zn diffuses into the upper surface 33A and the lower surface 33B of the tube 33 during the brazing heat treatment to form a Zn diffusion layer 42, and this Zn diffusion layer 42 exhibits a corrosion prevention effect. The brazing coating film 37 may be composed of other generally known brazing paints or a general brazing material layer applied to a clad material such as a brazing sheet. Also, a configuration in which the brazing material layer is formed on the fin 34 side and the brazing coating film 37 is not formed on the tube 33 can also be used. At this time, a Zn spraying layer or a flux layer may be formed on the front and back surfaces of the tube 33. The content of the flux agent contained in the flux layer is set to 0.1 mass% or more so as not to be less than 0.1 mass%. If the content of the flux agent is less than 0.1 mass%, the brazing property may be reduced.

[0039] Since the hydrophilic coating film 35 of the present embodiment has the above composition before brazing, after the brazing heat treatment, after the rheology modifier composed of the organic component, the surfactant, and the organic matter is removed, the remaining components aggregate to form the hydrophilic film 35a, thereby expressing hydrophilicity.

[0040] In particular, the coating film 35 containing the boron compound and the hydrophilic polymer exhibits excellent hydrophilicity even after being heated to the above-described brazing heat treatment temperature to become the film 35a. By containing the above substances, the adhesion to the surface of the aluminum alloy is ensured, the adhesion of the film 35a is improved, and the peeling of the film 35a is prevented. In addition, since the coating film 35 does not contain a glass component, the load on the coating device is small, and damage to the coating device can be prevented. For this reason, the coating film 35 can be formed with high productivity, and an aluminum plate excellent in productivity can be provided.

[0041] The coating film 35 is SiO 2Since the content is suppressed to 49% or less, even after it becomes the film 35a by brazing heating, it does not change color to brown or the like, and the appearance having the metallic luster originally possessed by the aluminum fin 34 can be maintained. Since the coating film 35 has a surface roughness Rz of 1.5 μm or less, there are few irregularities on the surface. For this reason, even if the process of applying the hydrophilic paint composition with a coating device such as a bar coater or a roll coater to the base material 34a and forming a paint layer is repeated, the load on the coating device is small, and damage to the coating device can be suppressed. Here, if boric acid-based glass particles or the like are added to the hydrophilic paint composition in order to improve hydrophilicity, the surface roughness of the coating film 35 becomes rough, and it is necessary to carry out the coating operation while worrying about damage to the coating device, so it does not contribute to productivity improvement. When the amorphous ratio in the film 35a after brazing heating is 50% or more, the hydrophilicity-imparting component hardly flows out into water, and the hydrophilic performance can be maintained for a long time. The film thickness of the coating film 35 is preferably 25 nm or more and 2000 nm or less. When the film thickness of the coating film 35 is less than 25 nm, sufficient hydrophilicity cannot be obtained, and when the film thickness exceeds 2500 nm, the brazing property deteriorates.

Examples

[0042] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. <Preparation of Samples> Based on the compositions shown in Tables 2 to 6 below (the balance being Al and inevitable impurities), an aluminum alloy was cast by semi-continuous casting. Next, a homogenization treatment was performed with a heating rate of 25 to 75 ° C / hour, a holding temperature of 350 to 480 ° C, a holding time of 1 to 10 hours, and a cooling rate of 20 to 50 ° C / hour, followed by hot rolling. During cold rolling, after the rolling rate reached 60% or more, an intermediate annealing was carried out by holding at 200 to 300 ° C for 6 hours, and a fin material of quality H14 was produced by rolling to a plate thickness of 0.1 mm by cold rolling. Thereafter, the fin material was cut to prepare a plurality of strip-shaped substrates, and these substrates were degreased. After the substrate degreasing treatment, the following hydrophilic paint composition for bar coater coating was prepared.

[0043] <Adjustment of hydrophilic coating composition> Table 1 below lists the types of boron compounds, hydrophilic polymers, rheology modifiers, surfactants, fluxing agents, and water-soluble lubricants used in the adjustment of the hydrophilic coating composition, and the types of water-soluble lubricating layers formed on the surface of the hydrophilic coating film.

[0044]

Table 1

[0045] As shown in Tables 2 to 6 below, the hydrophilic coating composition containing each component was applied to the surface of the aforementioned substrate by bar coater coating to form a coating layer. Thereafter, the coating layer was dried by heating at 250 °C for about 0.5 minutes, and an aluminum plate having a hydrophilic coating film with the dried coating film amount adjusted as shown in Tables 2 to 6 was obtained. Further, a water-soluble lubricant layer adjusted to the coating film amounts shown in Tables 2 to 6 below was formed on the previous hydrophilic coating film by bar coater coating.

[0046] Next, an aluminum alloy for tubes containing 1.0% Mn, 0.1% Cu, and 0.2% Si by mass% and the balance Al and inevitable impurities was melted, and an aluminum alloy tube for heat exchangers having a flat cross-sectional shape (thickness 0.26 mm × width 17.0 mm × height 1.5 mm) was formed from this alloy by extrusion molding. Furthermore, a coating film of a brazing material layer was formed on the flat upper and lower surfaces of these tubes. The coating film of the brazing material layer was formed by applying, by a bar coater, a solution consisting of 3 g of Si powder (D(99) particle size 10 μm), 6 g of Zn-containing flux (KZnF 3 powder: D(50) particle size 2.0 μm), and 1 g of an acrylic resin binder and 16 g of a mixture of 3-methoxy-3-methyl-1-butanol and isopropyl alcohol as a solvent, and drying (heating in an atmosphere of 150 °C for 5 minutes).

[0047] The aluminum plate was formed into a corrugated shape by corrugating to obtain aluminum fins with a total length of 100 mm. For 10 pieces of these aluminum fins, 11 tubes were combined to assemble a 10-stage mini-core test body similar to the heat exchanger shape shown in Fig. 1. These mini-core test bodies were subjected to brazing heat treatment under the condition of holding at 600 °C for 3 minutes in a nitrogen atmosphere furnace. By this brazing heat treatment, a sacrificial anode layer was formed on the upper and lower surfaces of the tubes on which the brazing coating film was formed, and a heat exchanger test body in which the fins provided with a hydrophilic film and the tubes were brazed and joined was obtained.

[0048] As evaluations before brazing, regarding paintability, press workability, fin formability, and coating film thickness, and as evaluations after brazing, regarding discoloration of the fins, hydrophilicity evaluation, brazability evaluation, pitting potential measurement, corrosion resistance test, and antibacterial property, measurements or evaluations were carried out based on the following conditions. These measurement results or evaluation results were described in Tables 7 to 11 described later.

[0049] [Paintability evaluation] In the painted state (state of the coating film) after applying the aforementioned hydrophilic paint composition to the surface of the aforementioned substrate and performing heat baking, the paintability was evaluated visually. If the paint composition was severely repelled and painting was impossible, it was judged as ×. If there was some repelling of the paint composition or streak-like unevenness but there was no problem in visual appearance, it was judged as 〇. If there was no repelling of the paint composition at all and there was no streak-like unevenness, it was judged as ◎. [Surface roughness] When the surface roughness is large, it is not preferable because scratches will occur on the roll during roll coating. Regarding the coating film on the surface of the substrate after baking, the surface roughness was measured with a laser microscope, and it was judged that if the surface roughness Rz was 1.5 μm or less, it was good, and if it was larger than 1.5 μm, it was not good.

[0050] [Press workability] The aforementioned hydrophilic coating composition was applied to the substrate surface and dried at 250°C for 0.5 minutes to form a coating film. Then, for the coating film on which a water-soluble lubricant layer was further formed, the kinetic friction coefficient of the surface was measured by a Bauden-type kinetic friction coefficient test. Samples with a kinetic friction coefficient exceeding 0.3 were judged as samples with significant damage to the mold during press working and were marked as ×. Samples with a kinetic friction coefficient of more than 0.2 and less than or equal to 0.3 were judged as △, and samples with a kinetic friction coefficient of 0.2 or less were judged as 〇. [Fin formability] A test piece of JIS No. 13 B shape was prepared by cutting out a fin material before brazing heat treatment parallel to the rolling direction, and the strength was measured by a tensile test. When the strength is higher than 200 MPa, springback becomes stronger during corrugation processing, making it difficult to perform corrugation processing and resulting in poor formability. When the strength is lower than 170 MPa, the fin end face sags during pressing, resulting in poor formability. Samples with a strength in the range of 170 - 200 MPa were judged as 〇, and samples outside this range were judged as ×.

[0051] "Coating film thickness" The vicinity of the surface including the brazed hydrophilic film of the fin material cut out to 10 mm × 10 mm from the heat exchanger test body was processed by FIB (Focused Ion Beam), and the processed cross-section was photographed at a magnification of 50,000 times with a FE-SEM (Field Emission-Scanning Electron Microscope), and the thickness of the hydrophilic coating film was actually measured. If the coating film thickness is less than 25 nm, the hydrophilicity after brazing is not satisfied. If the coating film thickness exceeds 2000 nm, it has an adverse effect on the brazing joint property.

[0052] [Discoloration of fins] After brazing heating, the discolored part of the aluminum plate was measured with a color difference meter, and the color difference value L * a * b * If the b value is between -3 and +12, it is judged as 〇. If the value exceeds the range, it is judged as ×. The color difference value L * a * b *If the b value is within the aforementioned range, it is possible to provide fins with less film discoloration after brazing and exhibiting the metallic luster inherent to aluminum. [Hydrophilicity evaluation: Measurement of water contact angle after water washing] After applying the aforementioned hydrophilic coating composition to the fin surface and baking it at 250°C for 0.5 minutes to form a coating film, for an aluminum plate having a hydrophilic film obtained by the above-described brazing heat treatment (600°C × 3 minutes), after immersing it in running water for 8 hours and then drying it for 16 hours, one cycle was defined as this process, and the water contact angle of the sample surface after performing 14 cycles was measured. In these measurement results, if the water contact angle was 30° or less, it was determined that the hydrophilicity was ○.

[0053] [Brazing property evaluation] For each fin brazed to the tube, the fin was peeled off from the tube, and the fin bonding trace remaining on the tube surface was observed. The number of unbonded locations (locations where brazing was performed but no bonding trace remained) was counted. For one sample, 100 bonding locations were counted, and a sample with 80 or more normal locations (locations where a bonding trace remained after brazing) was determined to be a sample with good brazing property.

[0054] [Corrosion resistance: Pitting potential measurement] The pitting potential after brazing was measured by anodic polarization measurement. A sample for polarization measurement was cut out from the fin material subjected to heat treatment equivalent to brazing, heated to 50°C, and immersed in a 5% NaOH solution for 30 seconds. Then, it was immersed in a 30% HNO 3 solution for 60 seconds, further washed with tap water and ion-exchanged water, and then degassed sufficiently by blowing high-purity N 2 gas. The pitting potential (reference electrode: saturated calomel electrode) was measured at room temperature in a 2.67% AlCl 3 solution at 40°C under the condition of a potential sweep rate of 0.5 mV / s. The pitting potential was defined as the potential at which the current density rapidly increased in the current density - potential diagram. However, when no distinct rapid increase in the current density was observed, the potential at a current density of 0.1 mA / cm 2 was measured as the pitting potential.

[0055] [Corrosion resistance test] For each fin brazed to the tube, an accelerated corrosion test in acidic seawater (SWAAT) was conducted for 5 days. After the test specimens were washed in boiling phosphoric acid chromic acid solution for 5 minutes, the fin joint marks remaining on the tube surface were observed. The number of peeling locations (locations where no joint marks remained after the corrosion resistance test) was measured. For one sample, 100 joints were measured, and a sample with 80 or more normal locations (locations where the joint remained after the corrosion resistance test) was determined to be a sample with good corrosion resistance.

[0056] [Antibacterial property] For each of the obtained samples, an antibacterial property test defined in JIS Z 2801:2010 was conducted to obtain the antibacterial activity value. If the obtained antibacterial activity value was 2.0 or more, it was judged as qualified. The above measurement results and evaluation results are shown in Tables 2 to 11 below.

[0057] [Table 2]

[0058] [Table 3]

[0059] [Table 4]

[0060] [Table 5]

[0061] [Table 6]

[0062] [Table 7]

[0063]

Table 8

[0064]

Table 9

[0065]

Table 10

[0066]

Table 11

[0067] Examples 1 to 90 contain, by mass%, Mn: 0.5 to 2.0%, Zn: 0.4 to 4.0%, and Cu: 0.001 to 0.2% on a substrate of an aluminum alloy, and are provided with a hydrophilic coating film containing a boron compound and a hydrophilic polymer, with the SiO 2 content being 49% or less. In the heat exchanger manufactured by brazing the fins provided with the coating films of these examples to the tubes, it has excellent characteristics in terms of paintability, press formability, and fin formability. Also, these examples were excellent in antibacterial properties, had no discoloration of the fins after heat treatment, were excellent in hydrophilicity, and were also excellent in brazing properties and corrosion resistance.

[0068] For these examples, Comparative Example 1 with a high Mn content was inferior in fin formability due to the precipitation of crystallized substances, and Comparative Example 2 with a low Mn content had a reduced strength. Comparative Example 3 with a high Zn content exceeded the desirable potential range and was inferior in corrosion resistance, and Comparative Example 4 with a low Zn content fell below the desirable potential range and resulted in inferior corrosion resistance. Comparative Example 5 with a high Cu content and Comparative Example 6 without Cu were outside the desirable range of strength. Comparative Example 7 with a high Si content was inferior in fin formability due to the precipitation of crystallized substances, and Comparative Example 8 without Si had problems with corrosion resistance. Comparative Examples 9 to 12 do not contain a hydrophilic polymer, so they are inferior in paintability or the water contact angle deteriorates after brazing. In Comparative Examples 13 and 14, since the hydrophilic polymer is polytetrafluoroethylene, the water contact angle after brazing is poor and the hydrophilicity is reduced. Comparative Examples 15 and 16 2 have poor antibacterial properties and cause discoloration of the fins because the SiO content is too high.

[0069] In Comparative Examples 17 and 18, due to the large surface roughness, the fin formability and antibacterial properties are inferior. Comparative Examples 19 and 20 do not contain a boron compound, so they are inferior in hydrophilicity after brazing and also have problems with antibacterial properties. Comparative Examples 21 and 22 2 have poor antibacterial properties and cause discoloration of the fins because the SiO content is too high. In Comparative Example 23, the application amount of the water-soluble lubricant is too large, causing problems in press workability.

Explanation of Reference Numerals

[0070] 30... Heat exchanger, 31, 32... Header manifolds, 33... Tubes, 33A... Upper surface, 33B... Lower surface, 33C... Refrigerant passage, 34... Fins, 35... Hydrophilic coating film (before brazing heat treatment), 35a... Hydrophilic film (after brazing heat treatment), 37... Coating film for brazing, 38... First fillet, 39... Second fillet, 41... Heat exchanger assembly.

Claims

1. It has a substrate of an aluminum alloy containing, by mass%, 0.5 to 2.0% of Mn, 0.4 to 4.0% of Zn, and 0.001 to 0.2% of Cu, with the balance being inevitable impurities and aluminum. A boron compound, a hydrophilic polymer, and SiO ２ An aluminum member provided with a hydrophilic coating film, characterized in that a coating film having a content of 49% or less and a surface roughness Rz of 1.5 µm or less is provided on one or both sides of the base material.

2. The hydrophilic polymer contains one or more of PVA (polyvinyl alcohol), polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, and water-soluble acrylic resin. The aluminum member provided with the hydrophilic coating film according to Claim 1.

3. The antibacterial activity value of the coating film is 2.0 or more. The aluminum member provided with the hydrophilic coating film according to Claim 1 or Claim 2.

4. The thickness of the coating film is 25 nm or more and 2000 nm or less. The aluminum member provided with the hydrophilic coating film according to Claim 1 or Claim 2.

5. The thickness of the coating film is 25 nm or more and 2000 nm or less. The aluminum member provided with the hydrophilic coating film according to Claim 3.

6. As a fluxing agent for improving brazing property, the coating film contains a fluorine compound containing any one or more of alkali metals, boron, aluminum, silicon, zinc, titanium, and zirconium. The aluminum member provided with the hydrophilic coating film according to Claim 1 or Claim 2.

7. As a fluxing agent for improving brazing property, the coating film contains a fluorine compound containing any one or more of alkali metals, boron, aluminum, silicon, zinc, titanium, and zirconium. The aluminum member provided with the hydrophilic coating film according to Claim 3.

8. As a fluxing agent for improving brazing property, the coating film contains a fluorine compound containing any one or more of alkali metals, boron, aluminum, silicon, zinc, titanium, and zirconium. The aluminum member provided with the hydrophilic coating film according to Claim 4.

9. The tensile strength is 170 MPa or more and 200 MPa or less, and it is excellent in formability. The aluminum member provided with the hydrophilic coating film according to Claim 1 or Claim 2.

10. The tensile strength is 170 MPa or more and 200 MPa or less, and it is excellent in formability. The aluminum member provided with the hydrophilic coating film according to Claim 3.

11. An aluminum member provided with the hydrophilic coating film according to claim 4, characterized in that the tensile strength is 170 MPa or more and 200 MPa or less, and the formability is excellent.

12. An aluminum member provided with the hydrophilic coating film according to claim 6, characterized in that the tensile strength is 170 MPa or more and 200 MPa or less, and the formability is excellent.

13. An aluminum member provided with the hydrophilic coating film according to claim 1 or claim 2, characterized in that the potential is -910 mV or more and -730 mV or less, and the corrosion resistance is excellent.

14. An aluminum member provided with the hydrophilic coating film according to claim 3, characterized in that the potential is -910 mV or more and -730 mV or less, and the corrosion resistance is excellent.

15. An aluminum member provided with the hydrophilic coating film according to claim 4, characterized in that the potential is -910 mV or more and -730 mV or less, and the corrosion resistance is excellent.

16. An aluminum member provided with the hydrophilic coating film according to claim 6, characterized in that the potential is -910 mV or more and -730 mV or less, and the corrosion resistance is excellent.

17. An aluminum member provided with the hydrophilic coating film according to claim 9, characterized in that the potential is -910 mV or more and -730 mV or less, and the corrosion resistance is excellent.

18. A heat exchanger characterized in that fins are formed from the aluminum member provided with the hydrophilic coating film according to claim 1 or claim 2.

19. A heat exchanger characterized in that fins are formed from the aluminum member provided with the hydrophilic coating film according to claim 3.

20. A heat exchanger characterized in that fins are formed from the aluminum member provided with the hydrophilic coating film according to claim 4.

21. A heat exchanger characterized in that fins are formed from the aluminum member provided with the hydrophilic coating film according to claim 6.

22. A heat exchanger characterized in that fins are formed from the aluminum member provided with the hydrophilic coating film according to claim 9.

23. A heat exchanger characterized in that fins are formed from the aluminum member provided with the hydrophilic coating film according to claim 13.

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