JP7096638B2 - Pre-coated fins and heat exchangers using them - Google Patents

Description

The present invention relates to, for example, a pre-coated fin material having a brazing sheet and a coating film, and a heat exchanger using the same.

Generally, an all-aluminum heat exchanger has an aluminum tube through which a refrigerant flows and aluminum fins for heat exchange between the air outside the tube, and the tube and fins are joined to each other. ing. Since the hydrophilicity of the fins greatly affects the heat exchange performance of the heat exchanger, fins having a hydrophilic coating film formed on the surface are often used. For joining a fin having such a hydrophilic coating film and a tube, a method of mechanically joining the fin by expanding the tube inserted in the hole provided in the fin is used (patented). See Document 1 and Patent Document 2).

As a joining method, brazing joining is assumed in addition to the above-mentioned mechanical joining. However, since a general resin-based or inorganic coating film deteriorates or decomposes at the heating temperature at the time of brazing, it cannot sufficiently exhibit hydrophilicity after brazing. Further, when flux is used for brazing, the presence of the coating film may hinder the flux action, resulting in insufficient brazing bonding. Therefore, when a heat exchanger is manufactured by brazing, a coating film is generally formed after brazing (see Patent Document 3). However, in this case, there is a problem that the manufacturing cost increases because a dedicated coating film forming facility is required. Further, in this case, it becomes difficult to cope with the increase in size of the heat exchanger.

Therefore, as a fin material in which a coating film is pre-coated before brazing, a fin material having a coating film containing a silicate as a main component has been proposed (see Patent Document 4). Further, in the production of a heat exchanger, a method of producing fins having a coating film containing a support such as xylene and a silicon-based binder such as silicone oil in advance before brazing has been proposed (Patent Document 5). reference).

Japanese Unexamined Patent Publication No. 4-278189 Japanese Unexamined Patent Publication No. 2012-052747 Japanese Unexamined Patent Publication No. 2004-347314 Japanese Unexamined Patent Publication No. 2013-137153 Japanese Patent Publication No. 2008-508103

However, the fin materials to which the coating film or the coating film has been pre-coated so far have insufficient hydrophilicity after brazing and have insufficient brazing function. That is, the conventional fin material does not have both excellent hydrophilicity durability and excellent brazing function. Therefore, it is necessary to separately supply a brazing material when manufacturing a heat exchanger using a fin material, and as a result, it is expected that the manufacturability will decrease due to an increase in the manufacturing process and the manufacturing cost will increase due to the procurement of parts. In addition, the pre-coated coating film or coating film may adversely affect the brazing bonding between the fins using the brazing material and the aluminum tube, resulting in insufficient bondability. Therefore, we have developed a pre-coated fin material that can maintain excellent hydrophilicity and durability, can be joined without using a brazing material, and can manufacture a heat exchanger with excellent bondability between fins and aluminum pipes. Is desired.

The present invention has been made in view of this background, and the fins have excellent hydrophilicity sustainability, the fins can be bonded to the aluminum tube without separately supplying a brazing material, and the heat has excellent bondability. It is an object of the present invention to provide a pre-coated fin material capable of manufacturing an exchanger and a heat exchanger using the pre-coated fin material.

One aspect of the present invention is a brazing sheet having a core material made of an aluminum alloy and a brazing material laminated on the core material.
With a hydrophilic coating film formed on the surface of the brazing sheet,
The brazing filler metal contains Si: 5 to 10% by mass, and the balance has a chemical component consisting of Al and unavoidable impurities.
The coating film contains at least one of silicate and amorphous silica,
The pre-coated fin material has a Si content of 10 to 300 mg / m ² in the coating film.

Another aspect of the present invention is in a heat exchanger having a core portion made of a fin made of the pre-coated fin material and an aluminum tube joined to the fin.

The pre-coated fin material has a brazing sheet having a core material made of an aluminum alloy and a brazing material laminated on the core material, the brazing material contains Si in the above-mentioned specific range, and the balance is Al and unavoidable impurities. It has a chemical component consisting of. Therefore, the precoated fin material can be joined to another member such as an aluminum pipe by the brazing material laminated and formed on the core material. Therefore, it is possible to join without using a separate joining member such as a brazing material, and it is possible to secure sufficient joining properties. Further, since the joining can be performed without separately using a joining member such as a brazing material, it is possible to prevent an increase in the manufacturing process and to meet the demand for cost reduction because it is not necessary to separately procure the joining member. Further, the brazing material having the specific composition can prevent the performance of the coating film formed on the brazing sheet from being impaired.

Further, in the coating film in which the amount of Si is adjusted as described above, the coating film performance is unlikely to deteriorate due to heating or the like. Therefore, the coating film can exhibit excellent hydrophilicity even after heating at the time of joining with another member such as an aluminum tube, and can maintain the initial excellent hydrophilicity for a long period of time. Further, the coating film hardly hinders the bonding between the precoated fin material and another aluminum member such as an aluminum tube. Therefore, although the pre-coated fin material has a coating film, it can be sufficiently bonded to, for example, an aluminum tube.

As described above, in the pre-coated fin material, the components of the coating film and the brazing material are optimized as described above. Therefore, it is possible to manufacture a heat exchanger having excellent hydrophilicity sustainability of the fins, capable of joining the fins to the aluminum tube without separately supplying a brazing material, and having excellent bondability.

Further, the heat exchanger has a core portion made of a fin made of a pre-coated fin material having excellent hydrophilicity durability and bondability as described above, and an aluminum tube bonded to the fin.
Therefore, in the heat exchanger, since the fins exhibit excellent hydrophilicity sustainability, it is possible to suppress an increase in ventilation resistance and stably exhibit good heat exchange performance for a long period of time. Further, in the heat exchanger, for example, since the aluminum tube and the fin are sufficiently joined, the heat exchange performance between the aluminum tube and the fin is improved.

The cross-sectional view of the pre-coated fin material in Example 1. FIG. The perspective view of the core part (specifically, a mini core) of the heat exchanger in Example 1. FIG. FIG. 3 is a cross-sectional view of a core portion (specifically, a mini core) of the heat exchanger in the first embodiment. The enlarged sectional view of the fin of the heat exchanger in Example 1. FIG. FIG. 1 is a partial cross-sectional view of the contact portion between the fin and the aluminum pipe before joining in the first embodiment. The front view of the heat exchanger in Example 2. FIG. The perspective view of the main part of the heat exchanger in Example 3. FIG. FIG. 7 is a partially enlarged cross-sectional view of the vicinity of the contact portion in FIG. 7. FIG. 7 is a cross-sectional view taken along the line III-III.

The pre-coated fin material is used to join the fin made of the pre-coated fin material to an aluminum tube to obtain a heat exchanger. As used herein, the term "aluminum tube" is a concept that includes not only a tube made of pure aluminum but also a tube made of an aluminum alloy. Specifically, A1000-based pure aluminum, A3000-based aluminum alloy, and the like can be used.

The pre-coated fin material has a brazing sheet having a core material made of an aluminum alloy and a brazing material laminated on the core material. The brazing sheet is, for example, a clad material, in which an Al—Si alloy (that is, a brazing material) is clad with an aluminum alloy (that is, a core material). From the viewpoint that the pre-coated fin material is used for fins that require heat exchange performance, the thickness of the brazing sheet is preferably 0.15 mm or less, for example. Further, even if the corrosion rate is high, the volume of the fin material itself is large, so that the fin material remains, and the sacrificial anode effect continues for a certain period of time, so that corrosion resistance is less likely to become a problem. It is preferably 0.05 mm or more.

The chemical composition of the aluminum alloy of the core material is selected from the group consisting of Si, Fe, Mn, Zn, Mg, Cu, In, Sn, Ti, V, Zr, Cr, and Ni in addition to Al and unavoidable impurities. It can further contain at least one additive element.

The chemical composition of the aluminum alloy of the core material contains, for example, Si: 0.05 to 0.8% by mass, Fe: 0.05 to 0.8% by mass, and Mn: 0.8 to 2% by mass, and the balance is It preferably consists of Al and unavoidable impurities. If the Mn content of the core material exceeds the above range, coarse crystallization is generated during casting, the rolling processability is impaired, and the production of the clad material tends to be difficult.

Si in the core material forms fine precipitates with other additive elements such as Mn or Fe to improve the strength of the core material and reduce the amount of solid solution of Mn to reduce thermal conductivity (electrical conductivity). To improve. The Si content of the core material is preferably 0.05 to 0.8% by mass as described above. If the Si content is less than 0.05% by mass, the effect of adding the Si is insufficient, and if it exceeds 0.8% by mass, the melting point of the core material decreases and deformation during brazing and local melting occur. It is easy to occur. The Si content is more preferably 0.1 to 0.8% by mass, still more preferably 0.3 to 0, from the viewpoint of sufficiently obtaining the effect of adding Si and sufficiently preventing deformation and local melting. It is 5.5% by mass.

Fe in the core material coexists with Mn to improve the strength of the fin material before and after brazing. The Fe content of the core material is preferably 0.05 to 0.8% by mass as described above. When the Fe content of the core material is less than 0.05% by mass, the effect of adding the core material is insufficient, and when it exceeds 0.8% by mass, the crystal grains become finer and the molten brazing core material is used. It tends to erode into the inside, the high temperature buckling resistance tends to decrease, and the self-corrosion property tends to increase. The Fe content is more preferably 0.1 to 0. From the viewpoint of sufficiently obtaining the effect of adding Fe, further suppressing the decrease in high temperature buckling resistance, and further suppressing the increase in self-corrosion property. It is 8% by mass, more preferably 0.3 to 0.5% by mass.

Mn in the core material functions to improve the strength of the core material and improve the high temperature buckling resistance. The Mn content of the core material is preferably 0.8 to 2% by mass as described above. If the Mn content of the core material is less than 0.8% by mass, the effect of addition is insufficient, and if it exceeds 2% by mass, coarse crystallization is generated during casting and the rolling workability is improved. It is easily damaged and it becomes difficult to manufacture the clad material. From the viewpoint of sufficiently obtaining the effect of adding Mn and further suppressing the deterioration of rolling processability, the content of Mn is more preferably 0.9 to 2% by mass, still more preferably 1 to 1.7% by mass. Is.

The core material can further contain Zn: 0.3 to 3% by mass. That is, the chemical composition of the aluminum alloy of the core material contains, for example, Si: 0.05 to 0.8% by mass, Fe: 0.05 to 0.8% by mass, and Mn: 0.1 to 2% by mass. Further, Zn: contains 0.3 to 3% by mass, and the balance is Al and unavoidable impurities. Zn in the core material can lower the potential and enhance the sacrificial anode effect, and can improve the corrosion resistance of the precoated fin material. If the Zn content of the core material is less than 0.3% by mass, the effect of addition is insufficient, and if it exceeds 3% by mass, the self-corrosion resistance of the core material itself tends to deteriorate, and intergranular corrosion sensitivity tends to deteriorate. Is also likely to increase. From the viewpoint of sufficiently obtaining the effect of adding Zn and further improving the corrosion resistance, the Zn content of the core material is more preferably 1 to 2.5% by mass, still more preferably 2 to 2.3% by mass.

The core material can further contain at least one of Mg: 1% by mass or less and Cu: 0.5% by mass or less. That is, the chemical components of the aluminum alloy of the core material are, for example, Si: 0.05 to 0.8% by mass, Fe: 0.05 to 0.8% by mass, Mn: 0.1 to 2% by mass, Zn: 0. It contains 3 to 6% by mass, and further contains at least one of Mg: 1% by mass or less and Cu: 0.5% by mass or less, and the balance is Al and unavoidable impurities.

Mg in the core material improves the strength of the fin material before and after brazing by forming a precipitate with Si. The Mg content of the core material is preferably 1% by mass or less as described above. When the Mg content exceeds 1% by mass, the melting point of the core material is lowered, and deformation during brazing and local melting are likely to occur. From the viewpoint of sufficiently obtaining the effect of adding Mg, the Mg content of the core material is more preferably 0.05 to 1% by mass, still more preferably 0.3 to 1% by mass.

Cu in the core material improves the strength of the fin material before and after brazing, but lowers the intergranular corrosion resistance. The Cu content of the core material is preferably 0.5% by mass or less as described above. When the Cu content exceeds 0.5% by mass, the potential of the fin material becomes noble and the sacrificial anode effect of the fin material tends to decrease, and the intergranular corrosion resistance also tends to decrease. From the viewpoint of sufficiently obtaining the effect of adding Cu, the Cu content of the core material is more preferably 0.05 to 0.5% by mass.

The core material can further contain at least one of In: 0.3% by mass or less and Sn: 0.3% by mass or less. That is, the chemical components of the aluminum alloy of the core material are, for example, Si: 0.05 to 0.8% by mass, Fe: 0.05 to 0.8% by mass, Mn: 0.1 to 2% by mass, Zn: 0. It contains 3 to 6% by mass, and further contains In: 0.3% by mass or less and Sn: 0.3% by mass, and the balance is Al and unavoidable impurities.

Sn in the core material lowers the surface potential and lowers the potential to enhance the sacrificial anode effect. The Sn content of the core material is preferably 0.3% by mass or less as described above. When the Sn content of the core material exceeds 0.3% by mass, coarse crystallization is easily generated during casting, which tends to impair the rolling processability, and the production of the plate material tends to be difficult. From the viewpoint of sufficiently obtaining the effect of adding Sn, the Sn content of the core material is more preferably 0.005 to 0.3% by mass.

In in the core material lowers the surface potential and lowers the potential to enhance the sacrificial anode effect. The In content of the core material is preferably 0.3% by mass or less as described above. When the content of In exceeds 0.3% by mass, coarse crystallization is generated during casting, which tends to impair the rolling processability, and it tends to be difficult to manufacture a plate material. From the viewpoint of sufficiently obtaining the effect of adding In, the content of In in the core material is more preferably 0.005 to 0.3% by mass.

The core material is further selected from Ti: 0.3% by mass or less, V: 0.3% by mass or less, Zr: 0.3% by mass or less, Cr: 0.3% by mass or less, and Ni: 2% by mass or less. At least one can be contained. That is, the chemical components of the aluminum alloy of the core material are, for example, Si: 0.05 to 0.8% by mass, Fe: 0.05 to 0.8% by mass, Mn: 0.1 to 2% by mass, Zn: 0. .Containing 3 to 6% by mass, Ti: 0.3% by mass or less, V: 0.3% by mass or less, Zr: 0.3% by mass or less, Cr: 0.3% by mass or less, and Ni: It contains at least one selected from 2% by mass or less, and the balance is Al and unavoidable impurities.

Ti in the core material mitigates local corrosion by taking the corrosion of the fin material before and after brazing as a layered corrosion form. Further, Ti improves the strength of the fin material before and after brazing, and also improves the high temperature buckling property. The Ti content of the core material is preferably 0.3% by mass or less as described above. When the Ti content of the core material exceeds 0.3% by mass, coarse crystallization is generated during casting, which tends to impair the rolling processability, and the production of the plate material tends to be difficult. From the viewpoint of sufficiently obtaining the effect of adding Ti, the Ti content of the core material is more preferably 0.01 to 0.3% by mass.

V in the core material dissolves in the matrix of the aluminum alloy structure to improve the strength, and is distributed in layers to prevent the progress of corrosion in the plate thickness direction. Further, V improves the strength of the fin material before and after brazing, and also improves the high temperature buckling property. The V content of the core material is preferably 0.3% by mass or less as described above. When the V content of the core material exceeds 0.3% by mass, coarse crystallization is easily generated during casting, which tends to impair the rolling processability, and the production of the plate material tends to be difficult. From the viewpoint of sufficiently obtaining the effect of adding V, the V content of the core material is more preferably 0.01 to 0.3% by mass.

Zr in the core material improves the strength of the fin material before and after brazing, and also improves the high temperature buckling property. The Zr content of the core material is preferably 0.3% by mass or less as described above. When the Zr content of the core material exceeds 0.3% by mass, coarse crystallization is easily generated during casting, which tends to impair the rolling processability, and the production of the plate material tends to be difficult. From the viewpoint of sufficiently obtaining the effect of adding Zr, the Zr content of the core material is more preferably 0.01 to 0.3% by mass.

Cr in the core material improves the strength of the fin material before and after brazing, and also improves the high temperature buckling property. The Cr content of the core material is preferably 0.3% by mass or less as described above. When the Cr content of the core material exceeds 0.3% by mass, coarse crystallization is easily generated during casting, which tends to impair the rolling processability, and the production of the plate material tends to be difficult. From the viewpoint of sufficiently obtaining the effect of adding Cr, the Cr content of the core material is more preferably 0.01 to 0.3% by mass.

Ni in the core material improves the strength of the fin material before and after brazing. The Ni content of the core material is preferably 2% by mass or less as described above. When the Ni content of the core material exceeds 2% by mass, the crystal grains become finer, the molten wax tends to erode into the core material, the high temperature buckling resistance tends to decrease, and the self-corrosion property tends to increase. Become. From the viewpoint of sufficiently obtaining the effect of adding Ni, the Ni content of the core material is more preferably 0.05 to 2% by mass, still more preferably 0.1 to 2% by mass.

The brazing filler metal contains Si: 5-10% by mass, and the balance has a chemical component consisting of Al and unavoidable impurities. Si in the brazing material enhances the fluidity of the molten brazing material during brazing heating and contributes to joining. If the Si content of the brazing filler metal is less than 5% by mass, the effect of adding the brazing filler metal is insufficient, and if it exceeds 10% by mass, the molten wax is excessive and the coating film is washed away by the molten wax to be hydrophilic. Sustainability is reduced. The Si content of the brazing filler metal is more preferably 7 to 9% by mass from the viewpoint of more sufficiently obtaining the effect of adding Si and further suppressing the decrease in hydrophilicity persistence.

The brazing filler metal can further contain Sr: 0.1% by mass or less. That is, the chemical composition of the aluminum alloy of the brazing material is, for example, Si: 5 to 10% by mass, Sr: 0.1% by mass or less, and the balance is Al and unavoidable impurities.

Sr in the brazing material reduces the Si particle size in the brazing material after brazing. The Sr content of the brazing filler metal is preferably 0.1% by mass or less as described above. When the Sr content of the brazing material exceeds 0.1% by mass, coarse crystallization is generated during casting, which tends to impair the rolling processability, and the production of the plate material tends to be difficult. From the viewpoint of sufficiently obtaining the effect of adding Sr, the Sr content of the brazing filler metal is more preferably 0.001 to 0.1% by mass.

The brazing filler metal can further contain at least one of Zn: 0.3% by mass or less and Cu: 0.3% by mass or less. That is, the chemical composition of the aluminum alloy of the brazing material contains, for example, Si: 5 to 10% by mass, Sr: 0.1% by mass or less, and further, Zn: 0.3% by mass or less and Cu: 0.3. It contains at least one by mass% or less, and the balance is Al and unavoidable impurities.

Zn in the brazing filler metal functions to enhance the sacrificial anode effect. The Zn content of the brazing filler metal is preferably 0.3% by mass or less as described above. When the Zn content of the brazing filler metal exceeds 0.3% by mass, the processability at the time of manufacturing tends to decrease, the natural potential becomes low, and the self-corrosiveness tends to increase. From the viewpoint of sufficiently obtaining the effect of adding Zn, the Zn content of the brazing filler metal is more preferably 0.05 to 0.3% by mass.

Cu in the brazing material nourishes the potential of the fillet after brazing and improves the corrosion resistance of the joint. The Cu content of the brazing filler metal is preferably 0.3% by mass or less as described above. When the Cu content of the brazing material exceeds 0.3% by mass, the potential of the fin material becomes noble and the sacrificial anode effect of the fin tends to decrease. The Cu content of the brazing filler metal is more preferably 0.05 to 0.3% by mass, still more preferably, from the viewpoint of sufficiently obtaining the effect of adding Cu and further suppressing the decrease in the fin-like anode effect. Is 0.1 to 0.2% by mass.

The thickness of the brazing filler metal is appropriately selected in relation to the Si content in the brazing filler metal, the joint shape between the fin and the aluminum tube, the fin pitch, and the like, and is preferably 7 μm or more, more preferably 7 to 30 μm.

In the brazing sheet, the brazing material may be clad on only one side of the core material or may be clad on both sides. The clad ratio of the brazing filler metal is applicable as long as it is within a common sense range and is appropriately selected, but is preferably 3 to 25%. If the clad ratio of the brazing material is less than the above range, the amount of brazing material melted during brazing heating tends to decrease, and fillets may not be sufficiently formed. On the other hand, if it exceeds the above range, the brazing material melts during brazing heating. The heartwood may melt because there is too much brazing material.

The brazing sheet is obtained by clad a brazing material on one side or both sides of the core material. As a method of clad the brazing material to the core material, an alloy ingot for the core material and an alloy ingot for the brazing material having the same composition as the composition of each element in the core material or the brazing material are cast, and then the alloy for the core material is cast. The ingots are homogenized according to a conventional method, the alloy ingots for brazing filler metal are hot-rolled, and then the alloy ingots for core materials and the alloy ingots for brazing filler metal after homogenization treatment are subjected to hot rolling. Hot-rolled products are superposed and hot-rolled to create a clad plate. Then, cold rolling is performed, intermediate annealing is performed if necessary, and finish cold rolling is performed to obtain a brazing sheet. After finishing cold rolling, it is cut into strips to the width of the product and becomes a brazing sheet as a material for fins. Before or after strip cutting, the coating film described later can be formed on the brazing sheet.

Next, the coating film formed on the surface of the brazing sheet will be described.
The coating film may be formed on one side of the brazing sheet or may be formed on both sides. The coating film is formed of, for example, an oxide containing silicon (Si), a composite oxide, or the like, and contains Si. The amount of Si in the coating film is 10 to 300 mg / m ² . If the amount of Si is less than 10 mg / m ² , the hydrophilicity may decrease. From the viewpoint of further suppressing the decrease in hydrophilicity persistence, the amount of Si in the coating film is more preferably 100 mg / m ² or more. On the other hand, when the amount of Si exceeds 300 mg / m ² , the coating film may impair the bondability at the time of brazing. The amount of Si is the amount per one side of the coating film. Further, when the amount of Si in the coating film is 10 to 300 mg / m ² , the adhesion amount of the coating film is preferably 20 to 800 mg / m ² .

The coating film contains at least one of silicate and amorphous silica. As a result , the hydrophilicity of the coating film is further improved. From the viewpoint of further improving the hydrophilicity persistence, it is more preferable that the coating film contains at least a silicate. The silicate is, for example, sodium silicate, lithium silicate, or the like. The silicate-containing coating film can be formed by applying an aqueous solution containing silicate, such as water glass, to the surface of the brazing sheet and drying it. From the viewpoint of further improving the hydrophilicity persistence, the silicate is more preferably derived from water glass.

Further, as the amorphous silica, for example, there is an agglomerate obtained by drying the amorphous colloidal silica, and the amorphous silica is derived from the amorphous colloidal silica from the viewpoint of further improving the hydrophilicity persistence. Is preferable. The coating film containing amorphous silica can be formed by applying amorphous colloidal silica on the surface of the brazing sheet and drying it. Further, a mixture of amorphous colloidal silica and an aqueous solution containing silicate is applied to the surface of the brazing sheet and dried to form a coating film containing amorphous silica and silicate. Can be done.

The coating film can further contain a fluoride flux. The content of the fluoride flux may be zero. The content of the fluoride flux is preferably 0 or more and 5000 mg / m ² or less. In this case, the flux effect can be obtained and the hydrophilicity sustaining performance can be further improved. If the content of the fluoride flux is too small, the effect of adding the flux may not be sufficiently obtained. Therefore, the content of the fluoride flux is more preferably 40 mg / m ² or more, further preferably 500 mg / m ² or more, and even more preferably 1000 mg / m ² or more. On the other hand, if the content of the fluoride flux is too large, the hydrophilicity may be deteriorated. From the viewpoint of suppressing the decrease in hydrophilicity persistence, the content of the fluoride flux is preferably 5000 mg / m ² or less, more preferably 3000 mg / m ² or less, and 2000 mg / m ² as described above. The following is more preferable. When the coating film contains a fluoride flux in the above range, the adhesion amount of the coating film is preferably 50 to 6000 mg / m ² .

Fluoride flux includes KAlF ₄ , K ₂ AlF ₅ , K ₂ AlF ₅ · H ₂ O, K ₃ AlF ₆ , AlF ₃ , KZnF ₃ , K ₂ SiF ₆ , Cs ₃ AlF ₆ , Cs AlF _{4.2 H 2 O.} , Cs ₂ AlF ₅ · H ₂ O and the like. When the coating film contains a fluoride flux, the coating film has a Si content of 10 to 300 mg / m ² , and may be formed by a single layer containing the fluoride flux, or may have a Si content. It may be formed by a laminate of a layer having a concentration of 10 to 300 mg / m ² and a layer containing a fluoride flux as a main component. Specifically, in the case of a single layer, the coating is formed by, for example, a layer containing at least one of silicate and amorphous silica and a fluoride flux. In the case of a two-layer structure laminate, the coating film is formed of, for example, a layer containing at least one of silicate and amorphous silica as a main component and a layer containing a fluoride flux as a main component.

Further, the coating film can further contain an organic resin. In this case, the coatability at the time of forming the coating film is improved. In addition, it is possible to prevent Si components such as silicate and amorphous silica from falling off from the coating film.

The organic resin is preferably made of a water-soluble acrylic resin and / or polyoxyethylene alkylene glycol (PAE). In this case, the organic resin is easily decomposed by heating at the time of joining, for example, and the organic resin can be eliminated from the coating film. As a result, the amount of organic resin in the coating film after bonding is reduced, so that it is possible to prevent the bonding property from being impaired by the organic resin.

Further, the pre-coated fin material may have a base treatment layer made of a chemical conversion film formed between the brazing sheet and the coating film. The base treatment layer made of a chemical conversion film can be formed by, for example, phosphoric acid chromate treatment, zirconium phosphate treatment, boehmite treatment or the like. The base treatment layer may be formed by other treatments as long as the adhesion between the brazing sheet and the coating film can be improved.

In the heat exchanger, as the fin made of the pre-coated fin material, a shape such as an insertion fin or a corrugated fin can be adopted. The fin material may have a slit in order to improve the heat exchange performance.

The shape of the aluminum pipe is not particularly limited as long as it is a refrigerant passage pipe through which the refrigerant flows, and a round pipe, a flat pipe, or the like can be adopted. An inner pillar may be formed in the pipe to divide the inside into a plurality of passages. More specifically, as the aluminum tube, for example, a flat multi-hole tube can be adopted. The aluminum tube may or may not have a brazing material clad on the surface.

Next, a method of joining the fin made of the pre-coated fin material and the aluminum pipe will be described. In joining, it is possible to utilize the joining ability of the brazing material laminated and formed on the core material in the brazing sheet without using the brazing material separately. Considering the use of the heat exchanger as fins, it is desired to avoid deformation of the fin material itself, and therefore the joining heating conditions can be controlled. The brazing heating temperature is, for example, 590 ° C to 605 ° C, and the brazing heating time is, for example, 1 to 10 minutes. The atmosphere during brazing heating is an inert gas atmosphere such as a nitrogen gas atmosphere, a helium gas atmosphere, and an argon gas atmosphere.

As described above, the pre-coated fin material has a brazing material and a coating film on the core material. As described above, the coating film can be formed on the core material or on the brazing material. At the time of brazing heating, at least a part of the brazing material may be softened or melted to form a fillet that contributes to the bonding at the contact portion with the aluminum tube. At this time, even if the coating film is formed on the brazing material, the fins of the heat exchanger can exhibit excellent hydrophilicity sustainability. It is considered that this is because the Si component (silicate, amorphous silica, etc.) in the coating film is retained on the fins even if the brazing filler metal is softened or melted.

The heat exchanger has a core portion composed of a fin made of a precoated fin material and an aluminum tube joined to the fin. Specific examples of the heat exchanger will be described with reference to the following examples, but the heat exchanger is manufactured by assembling a header, a side support, an entrance / exit pipe, and the like to the core portion.

The heat exchanger can be used, for example, in an air conditioner or a refrigerator. It can also be used in automobile capacitors, evaporators, radiators, heaters, intercoolers, oil coolers, and the like. Further, it can also be used as a cooling device for cooling a heating element such as an IGBT (Insulated Gate Bipolar Transistor) provided in an inverter unit that controls a drive motor of a hybrid vehicle or an electric vehicle.

(Example 1)
This example is an example in which a plurality of pre-coated fin materials according to Examples and Comparative Examples are produced and their performances are compared. In this example, as shown in Tables 1 to 11 described later, a plurality of precoated fin materials (Samples E1-1 to E9-2, which have different core alloy composition, brazing alloy composition, and coating film composition). Samples C1-1 to C9-2) are prepared. Then, using each of these pre-coated fin materials, a core portion for a heat exchanger is produced, and hydrophilicity persistence and bondability are compared and evaluated. In this example, a test mini-core is manufactured as a core portion.

As illustrated in FIG. 1, the pre-coated fin material 1 has a brazing sheet 11 and a coating film 12 formed on the surface thereof. The brazing sheet 11 has a core material 111 made of an aluminum alloy and a brazing material 112 formed on both sides of the core material 111. The coating film 12 is formed on both sides of the brazing sheet 11. Specifically, the coating film 12 is laminated on the brazing material 112 via a base treatment layer made of a chemical conversion film (not shown). There is. The formation of the base treatment layer is optional and may not be formed.

The brazing filler metal 112 contains an additive component (element) shown in Table 1 described later, and has a chemical component whose balance is Al and unavoidable impurities. In this example, the brazing filler metal of Sample A1 to Sample A10 having different compositions shown in Table 1 is used. The core material 111 contains an additive component (element) shown in Table 2 described later, and has a chemical component whose balance is Al and unavoidable impurities. In this example, the core materials of the samples B1 to B34 having different compositions shown in Table 2 are used. The coating film 12 contains Si derived from lithium silicate at the content shown in Tables 3 to 11 described later, and further contains a water-soluble acrylic resin in an amount capable of improving coatability. Further, in a part of the pre-coated fin material 1 produced in this example, the coating film 12 further contains flux in the amount shown in the table below.

As shown in FIGS. 2 and 3, the mini core 2 has a fin 3 made of a precoated fin material 1 and an aluminum tube 4, and a corrugated fin 3 is sandwiched between the aluminum tubes 4. In FIG. 2, one of the two aluminum tubes 4 sandwiching the fin 3 is shown by a broken line in order to clearly indicate the corrugated shape of the fin 2.

The fin 3 is made of a pre-coated fin material 1 formed in a corrugated shape. More specifically, as shown in FIG. 4, the fin 3 has a brazing sheet 11 composed of a core material 111, a brazing material 112 formed on both sides thereof, and a coating film 12 formed on both sides thereof.

As shown in FIGS. 2 and 3, the aluminum tube 4 is made of a flat multi-hole tube made of an aluminum alloy. The aluminum pipe 4 has a large number of refrigerant flow paths 411 for circulating the refrigerant. In the mini-core 2, the corrugated fins 3 are joined to the aluminum pipe 4 at each apex 30.

Hereinafter, a method for manufacturing the mini core 1 of this example will be described. Specifically, first, an aluminum alloy for a core material having the composition shown in Table 2 and an aluminum alloy for a brazing material having the composition shown in Table 1 are ingot by continuous casting, and homogenized according to a conventional method. The aluminum alloy ingot for brazing material is further hot-rolled, clad on one side of the aluminum alloy ingot for core material at a ratio of 10% brazing, hot-rolled, and then cold-rolled. After performing intermediate annealing, the brazing sheet 11 was manufactured through final cold rolling. The components other than the additive components shown in each table, that is, the balance, are Al and unavoidable impurities.

Next, by performing a base treatment, a base treatment layer made of a chemical conversion film (not shown) was formed on both sides of the brazing sheet 11. As the base treatment, a phosphoric acid chromate treatment was performed. The thickness of the base treatment layer is, for example, about 1 μm.

Next, using a bar coater, a predetermined amount of a paint containing water glass, a water-soluble acrylic resin, and KAlF ₄ , which is a fluoride flux added as needed, is applied onto the base treatment layer, and the temperature is 200 ° C. The coating film 12 was formed by drying with (see FIG. 1). In this way, the pre-coated fin material 1 having the coating film 12 containing Si derived from water glass at the content shown in Tables 3 to 11 on the brazing sheet 11 was produced. The coating film 12 was formed on both sides of the brazing sheet 11.

The amount of Si in the coating film 12 was measured by fluorescent X-ray analysis. X-ray fluorescence analysis was performed using ZSXPrimus II manufactured by Rigaku under the conditions of atmosphere: vacuum, tube: Rh, and output: 50 kV-60 mA. The quantification of Si in the coating film was performed by a calibration curve method using a standard Si sample.

Next, the pre-coated fin material 1 was processed into a corrugated shape. In this way, a corrugated fin 3 having a coating film 12 formed on both sides of the brazing sheet 11 was obtained (see FIGS. 2 to 4). Each of these fins 3 is used in the production of the mini core 1.

Next, as the aluminum tube 4, a flat multi-hole tube made of a 3000 series aluminum alloy was produced by extrusion processing (see FIGS. 2 and 3). A corrugated fin 3 was sandwiched between the two aluminum tubes 4 to prepare an assembly (see FIGS. 2 and 3). At this time, as shown in FIG. 5, each apex 30 of the corrugated fin 3 was brought into contact with the aluminum tube 4. Then, the assembly was held in a furnace at a temperature of 600 ° C. for 3 minutes in a nitrogen gas atmosphere, and then cooled to room temperature (25 ° C.). The brazing filler metal 112 of the fin 3 softens or melts during heating in the furnace, and the brazing filler metal solidifies during cooling. By softening, melting, and solidifying the brazing filler metal, each apex 30 of the corrugated fin 3 and the aluminum tube 4 are joined at the contact portion (not shown). In this way, as illustrated in FIGS. 2 and 3, a mini core 2 to which the fin 3 and the aluminum tube 4 are joined is obtained.

Next, the pre-coated fin material 1 and the mini-core 2 of each sample obtained as described above were evaluated for hydrophilicity persistence, bondability, strength, corrosion resistance, deformation rate, and manufacturability as follows. The results are shown in Tables 3 to 11.

<Persistence of hydrophilicity>
The evaluation of hydrophilicity persistence was performed using the pre-coated fin material of each sample. Each sample is heated assuming that the fins are joined after the coating film is formed. Specifically, the precoated fin material was heated in a nitrogen gas atmosphere in a furnace at a temperature of 600 ° C. for 3 minutes. Then, the pre-coated fin material was immersed in pure water for 2 minutes and then air-dried for 6 minutes. The cycle of immersion in pure water and air drying was repeated 300 times. Next, the contact angle of water droplets on the coating film of each test plate was measured. The contact angle was measured using a FACE automatic contact angle meter "CA-Z" manufactured by Kyowa Surface Chemistry Co., Ltd. Specifically, water droplets were dropped onto the coating film at room temperature, and the contact angle of the water droplets after 30 seconds was measured. When the contact angle is less than 10 °, it is evaluated as "A", when it is 10 ° or more and less than 20 °, it is evaluated as "B", and when it is 20 ° or more and less than 30 °, it is evaluated as "C". The case of 30 ° or more was evaluated as “D”.

<Joinability>
The joint portion of each mini-core after joining is cut with a utility knife, and the joint length L ₁ of the fin is divided by the sum of the length L ₂ of the peak portion of the fin and expressed as a fraction (L ₁ /). L ₂ × 100) was defined as the bonding ratio (%). A case where the joining rate is 90% or more is evaluated as "A", a case where the joining rate is 80% or more and less than 90% is evaluated as "B", and a case where the joining rate is 70% or more and less than 80% is "". It was evaluated as "C", and when it was less than 70%, it was evaluated as "D".

<Strength>
The strength was measured by a tensile test using the pre-coated fin material of each sample. Each sample is heated assuming that the fins are joined after the coating film is formed. Specifically, the precoated fin material was heated in a nitrogen gas atmosphere in a furnace at a temperature of 600 ° C. for 3 minutes. The tensile test was carried out for each sample at room temperature in accordance with JIS Z2241 (2011) under the conditions of a tensile speed of 10 mm / min and a gauge length of 50 mm.

<Corrosion resistance>
A CASS test was carried out for 500 hours to confirm the corrosion state of the fins. When the residual amount of fins is 70% or more in the cross-sectional observation with an optical microscope, it is evaluated as "A", when it is 50% or more and less than 70%, it is evaluated as "B", and when it is 30% or more and less than 50%. Was evaluated as "C", and when it was less than 30%, it was evaluated as "D".

<Deformation rate>
The fin height of the mini core before and after joining was measured to evaluate the deformation rate due to fin buckling. That is, when the ratio of the fin height change before and after joining to the fin height before joining is 5% or less, it is evaluated as "A", and when it exceeds 5% and is 10% or less, it is evaluated as "B". A case of more than 10% and 15% or less was evaluated as "C", and a case of more than 15% was evaluated as "D".

<Manufacturability>
During the rolling process of the aluminum alloy, for example, the case where a good plate material could not be produced due to surface cracking was evaluated as “x”, and the case where a good plate material could be produced was evaluated as “◯”. When the manufacturability is "x", the other evaluations described above are omitted.

As shown in Tables 1 to 3, Sample E1-1 and Sample E1-2 are superior in hydrophilicity persistence and high bonding ratio as compared with Sample C1-1 and Sample C1-2. Therefore, in the precoated fin material 1 having the brazing sheet 11 and the coating film 12, the brazing material 112 of the brazing sheet 11 contains 5 to 10% by mass of Si, and the balance is a chemical component composed of Al and unavoidable impurities. It turns out that it is preferable to have. Further, Sample E1-3 and Sample E1-4 have excellent hydrophilicity sustainability and a high bonding ratio as compared with Sample C1-3 and Sample C1-4. Therefore, it can be seen that the amount of Si in the coating film 12 is preferably 10 to 300 mg / m ² .

Further, as can be seen by comparing Samples E2-1 and E-2 in Table 4 with Samples E2-3 and E-4, the coating film can contain a fluoride flux, and the fluoride flux can be contained. By adjusting the content of the above to 40 to 5000 mg / m ² , the hydrophilicity persistence can be further improved.

Further, as is known from Tables 1, 2 and 5, Si: 0.05 to 0.8% by mass, Fe: 0.05 to 0.8% by mass, and Mn: 0 in the aluminum alloy of the core material. Samples E3-1 to E3-6 containing 8 to 2% by mass have higher strength or corrosion resistance than Samples C3-1 to C3-6 in which the content of these additive components is out of the above range, respectively. Was better.

Further, as is known from Tables 1, 2 and 6, the sample E4-1 and the sample 4-2 containing Zn: 0.3 to 3% by mass in the aluminum alloy of the core material have a Zn content. Corrosion resistance was more excellent than that of Samples C4-1 to C4-2 outside the above range.

Further, as is known from Tables 1, 2 and 7, the aluminum alloy of the core material contains at least one of Mg: 1% by mass or less and Cu of 0.5% by mass or less, Sample E5-1 and Sample 5-2. Was more excellent in corrosion resistance and bonding property as compared with Samples C5-1 to C5-2 in which the content of these additive components was out of the above range.

Further, as is known from Tables 1, 2 and 8, the sample E6-1 and the sample E6-1 containing at least one of In: 0.3% by mass or less and Sn: 0.3% by mass or less in the aluminum alloy of the core material. Sample 6-2 has improved corrosion resistance. On the other hand, when the content of these additive components is out of the above range, the manufacturability is impaired.

Further, as is known from Tables 1, 2 and 9, Ti: 0.3% by mass or less, V: 0.3% by mass or less, Zr: 0.3% by mass or less, Cr in the aluminum alloy of the core material. Samples E7-1 to 7-5 containing at least one selected from: 0.3% by mass or less and Ni: 2% by mass or less were improved with a reduced deformation rate. On the other hand, when the content of these additive components is out of the above range, the manufacturability is impaired or the deformation rate is rather increased.

Further, as is known from Tables 1, 2 and 10, the sample E8-1 containing Sr: 0.1% by mass or less in the aluminum alloy of the brazing material was improved with a low deformation rate. On the other hand, when the Sr content exceeds the above range, the manufacturability is impaired.

Further, as is known from Tables 1, 2 and 11, the sample E9-1 containing at least one of Zn: 0.3% by mass or less and Cu: 0.3% by mass or less in the aluminum alloy of the brazing material. And the sample E9-2 had improved corrosion resistance as compared with the sample C9-1 and the sample C9-2 in which the content of these additive components was out of the above range, respectively.

(Example 2)
Next, an example of a heat exchanger having a core portion using the pre-coated fin material shown in Example 1 will be described. As shown in FIG. 6, the heat exchanger 5 has a core portion 2 having a large number of configurations similar to those of the mini core of the first embodiment. Specifically, the core portion 2 is formed by alternately laminating a large number of fins 3 made of corrugated precoated fin material 1 and aluminum tubes 4, and the fins 3 and aluminum tubes 4 are the mini cores of the first embodiment. They are joined in the same way.

Headers 51 are attached to both ends of the aluminum tube 4, and side plates 52 are attached to both ends (outermost) of the core portion 2 in the stacking direction. Further, a tank 53 is assembled to the header 51. These header 51, side plate 52, and tank 53 can be joined, for example, by brazing.

In the heat exchanger 5, the same precoated fin material 1 as the samples E1-1 to E9-2 shown in Tables 3 to 11 described above can be used. That is, the heat exchanger 5 has a core portion 2 composed of a fin 3 made of the pre-coated fin material 1 having excellent hydrophilicity sustainability and bondability as described above, and an aluminum tube 4 bonded to the fin 3. Therefore, in the heat exchanger 5, since the fins 3 exhibit excellent hydrophilic durability, it is possible to suppress an increase in ventilation resistance and stably exhibit good heat exchange performance for a long period of time. Further, in the heat exchanger 5, for example, the aluminum tube 4 and the fin 3 are sufficiently joined to each other, so that the heat exchange performance between the aluminum tube 4 and the fin 3 is improved.

(Example 3)
This example is an example of a heat exchanger having an aluminum tube made of a flat multi-hole tube inserted in an assembly hole formed in a fin. As illustrated in FIG. 7, the heat exchanger 6 has an aluminum tube 7 and fins 8. As illustrated in FIGS. 7 and 9, the fin 8 has an assembly hole 81 into which the aluminum tube 7 is inserted. As illustrated in FIGS. 7 and 8, the aluminum tube 7 is in contact with the fin 8 at the contact portion 61. As illustrated in FIGS. 7 to 9, in the contact portion 61, a fillet 600 for joining the aluminum pipe 7 and the fin 8 is formed.

As illustrated in FIG. 7, the heat exchanger 6 of this example has a large number of fins 8 arranged at intervals in the plate thickness direction and a plurality of aluminum tubes 7 extending in the plate thickness direction of the fins 8. And have. The fin 8 has a substantially rectangular shape in a plan view viewed from the plate thickness direction.

As illustrated in FIGS. 8 and 9, the fin 8 is composed of a pre-coated fin material 1 having a brazing sheet 11 similar to that in the first embodiment and a coating film 12 formed on both sides thereof, but the brazing sheet 11 The brazing filler metal 112 is formed on one side of the core wood 111. More specifically, the brazing filler metal 112 is formed on the side of the contact portion 61 with the aluminum pipe 7, and the brazing filler metal 112 is not formed on the opposite side. The coating film 12 is laminated and formed on the brazing filler metal 112 on the forming surface side of the brazing filler metal 112, and is laminated and formed on the core material 111 on the non-forming surface side of the brazing filler metal. The method for forming the brazing filler metal and the coating film is the same as in Example 1.

The assembly hole 81 in the fin 8 is a notch 811 provided in the outer peripheral edge portion of the fin 8. The notch 811 extends from the outer peripheral edge portion of the fin 8 in the plate width direction, and has a U-shape in a plan view. Further, the notch 811 is configured so that the aluminum pipe 7 can be press-fitted from the open portion 812 provided on the outer peripheral edge portion of the fin 8.

Further, as shown in FIGS. 7 and 9, the fin 8 has a collar portion 82 protruding from the peripheral edge of the assembly hole 81. The height of the collar portion 82 is not particularly limited, but may be, for example, 200 μm or more.

As illustrated in FIG. 7, the aluminum tube 7 is a flat multi-hole tube having an oval cross section in the longitudinal direction and having a plurality of flow paths 711 formed therein. The flat multi-hole tube is arranged so that the width direction thereof and the plate width direction of the fin plate are parallel to each other. Further, as illustrated in FIGS. 7 and 8, the aluminum tube 7 made of a flat multi-hole tube has a collar portion 82 at one end portion 712 in the width direction thereof, that is, a portion whose surface has a curved surface shape. Is in contact with. Then, one end portion 712 of the aluminum tube 7 and the tip portion 821 of the collar portion 82 in the U shape form the contact portion 61. Although not shown, in the contact portion 61, the brazing filler metal 112 of the fin 8 joins the fin 8 and the aluminum pipe 7 by heating and cooling at the time of joining, which will be described later.

The heat exchanger 6 of this example can be manufactured, for example, as follows. First, the precoated fin material 1 is produced in the same manner as in Example 1 except that the brazing material 112 is formed on one side of the core material 111, and the fin 8 is produced by a conventional method using this fin material. Then, the plurality of fins 8 are arranged at intervals in the plate thickness direction. Next, an aluminum tube 7 made of a flat multi-hole tube prepared by a conventional method is press-fitted into the assembly hole 81 of the fin 8, and at least one end portion 712 of the aluminum tube 7 and the tip end portion 821 of the collar portion 82 are contacted. Get in touch. Then, for example, it is heated at a temperature of 600 ° C. for 3 minutes in a nitrogen gas atmosphere and then cooled. The brazing filler metal 112 of the fin 8 is softened or melted by heating, and the brazing filler metal is condensed by cooling, so that the fin 8 and the aluminum tube 7 are joined at the contact portion 61. In this way, the heat exchanger 6 having a core portion in which the aluminum tube 7 and the fin 8 are joined can be manufactured. The heat exchanger of this example can also have the same effect as that of the second embodiment.

As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without impairing the gist of the present invention. ..

1 Pre-coated fin material 11 Brazing sheet 111 Core material 112 Wax material 12 Coating film 5, 6 Heat exchanger 3, 8 Fin 4, 7 Aluminum tube

Claims (11)

A brazing sheet having a core material made of an aluminum alloy and a brazing material laminated on the core material,
With a hydrophilic coating film formed on the surface of the brazing sheet,
The brazing filler metal contains Si: 5 to 10% by mass, and the balance has a chemical component consisting of Al and unavoidable impurities.
The coating film contains at least one of silicate and amorphous silica,
A pre-coated fin material having a Si content of 10 to 300 mg / m ² in the coating film. The precoated fin material according to claim 1 , wherein the coating film contains lithium silicate. The precoated fin material according to claim 1 or 2 , wherein the coating film further contains 40 to 5000 mg / m ² of fluoride flux. The core material contains Si: 0.05 to 0.8% by mass, Fe: 0.05 to 0.8% by mass, and Mn: 0.8 to 2% by mass, and the balance is from Al and unavoidable impurities. The precoated fin material according to any one of claims 1 to 3 , which has a chemical component. The precoated fin material according to claim 4 , wherein the core material further contains Zn: 0.3 to 3% by mass. The precoated fin material according to claim 4 or 5 , wherein the core material further contains at least one of Mg: 1% by mass or less and Cu of 0.5% by mass or less. The precoated fin material according to any one of claims 4 to 6 , wherein the core material further contains at least one of In: 0.3% by mass or less and Sn: 0.3% by mass or less. The core material is further selected from Ti: 0.3% by mass or less, V: 0.3% by mass or less, Zr: 0.3% by mass or less, Cr: 0.3% by mass or less, and Ni: 2% by mass or less. The precoated fin material according to any one of claims 4 to 7 , which contains at least one of the above. The precoated fin material according to any one of claims 1 to 8 , wherein the brazing material further contains Sr: 0.1% by mass or less. The precoated fin material according to any one of claims 1 to 9 , wherein the brazing material further contains at least one of Zn: 0.3% by mass or less and Cu: 0.3% by mass or less. A heat exchanger having a core portion made of a fin made of the precoated fin material according to any one of claims 1 to 10 and an aluminum tube joined to the fin.

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