JP6976041B2 - Heat exchanger - Google Patents

Description

The present invention relates to a heat exchanger that can prevent the fins from prematurely detaching from the tube due to the effects of corrosion.

Aluminum alloy heat exchangers manufactured by brazing these with tubes, fins and header pipes as the main components have so far clad extruded tubes Zn-sprayed on the surface and Al-Si alloy brazing material on both sides. Combinations with fins made of brazing sheets (three-layer laminated) have been widely used. However, in recent years, by combining extruded tubes and fins with a brazing coating film consisting of Si powder, Zn-containing flux, and binder on the surface, it has become possible to globally manufacture inexpensive, high-quality, high-performance products. became.

In the above-mentioned heat exchanger, Zn contained in the flux of the coating film for brazing diffuses at the time of brazing and forms a sacrificial anode layer on the surface of the tube, so that the progress of corrosion generated in the tube is suppressed and the tube is used. Prevents flux leakage due to corrosion.
Further, during brazing, the liquid phase brazing formed by the reaction between the brazing coating film and the tube flows to the joint between the fin and the tube to form a fillet and join the two, so that high heat exchange performance can be obtained. ..

In the above technical background, the present inventors propose a brazing composition containing aluminum powder, Si powder, and Zn powder in Patent Document 1, and in Patent Document 2, the Si powder is formed on the outer surface of the tube. the coating amount was proposed heat exchanger tubes to form a 1 to 5 g ^/ m 2, the Zn-containing flux coating for brazing contained coating amount of the 5 to 20 g / ^{m 2} and the Si powder and the Zn-containing flux was of ..
According to the technique described in the patent document, since the Si powder and the Zn-containing flux are mixed in the coating film, the Si powder melts into a brazing liquid at the time of brazing, and the Zn in the flux is added to the brazing liquid. Spreads evenly and spreads evenly on the surface of the tube. Since the diffusion rate of Zn in a liquid phase such as a brazing solution is significantly higher than the diffusion rate in a solid phase, the Zn concentration on the tube surface becomes substantially uniform. As a result, a uniform sacrificial anode layer is formed on the surface of the tube, and the corrosion resistance of the heat exchanger tube can be improved.

Japanese Unexamined Patent Publication No. 7-88689 Japanese Unexamined Patent Publication No. 2004-330233

However, in the heat exchanger having the above-mentioned structure, a part of Zn contained in the flux of the coating film for brazing flows to the joint portion with the fin together with the liquid phase brazing formed at the time of brazing. Therefore, the fillet formed at the joint between the tube and the fin contains diffused Zn.
As a result, when the heat exchanger is used in an area where the corroded environment is extremely severe, the fillet at the fin joint may be preferentially corroded, and the fin and the tube may be separated, resulting in peeling of the fin. ..
For the performance of this type of heat exchanger, it is important to maintain high heat exchange performance for a long period of time. For that purpose, it is necessary to prevent refrigerant leakage due to corrosion and to maintain the connection between the fin and the tube for a long period of time.
If the fins are peeled off in the heat exchanger, the heat exchange performance is deteriorated, and the corrosion resistance life of the heat exchanger (tube) is shortened due to the deterioration of the sacrificial anticorrosion effect of the fins, which may cause a problem in the performance of the heat exchanger. ..
Therefore, in heat exchangers, it is important that the tube has excellent corrosion resistance, has a long corrosion resistance, and is less likely to cause fin peeling. However, it also has excellent characteristics in terms of improving the corrosion resistance of the tube and preventing fin peeling. It was a difficult task to do.

In view of these backgrounds, the present invention provides a heat exchanger provided with an aluminum alloy tube for a heat exchanger, which can satisfactorily bond fins and tubes, and has excellent corrosion resistance, fin peeling resistance, and extrudability. The purpose.

In the heat exchanger of the present invention , an organic copper compound or a part thereof is supplied with a metallic Cu powder, and a coating film for brazing is formed on the surface thereof, which is composed of a Cu component, Si powder, and a Zn-containing flux and a binder. A heat exchanger having a dexterous aluminum alloy tube and fins formed into fillets by brazing and bonded to the tube, wherein the aluminum alloy tube has Si: 0.05 to 1.0% by mass, Mn: It is composed of an extruded tube of an aluminum alloy having a composition of 0.1 to 1.5% by mass, Cu: 0.05% by mass or less, residual unavoidable impurities and aluminum, and the brazing coating film is an organic copper compound or one thereof. Cu content of the section as Cu component supplied with a metal Cu powder: 0.01~0.5g ^/ m 2, Si powder: 1~5g ^/ m 2, Zn-containing flux: 2 to 10 g / ^{m 2,} binder: It is a coating film for brazing consisting of 0.5 to 3.5 g / m ² , and the fins are Zn: 0.3 to 5.0% by mass, Mn: 0.5 to 2.0% by mass, Fe: It is characterized by being composed of an aluminum alloy having a composition of 1.0% by mass or less, Si: 1.5% by mass or less, residual unavoidable impurities and aluminum.
In the heat exchanger of the present invention, it is preferable that the fillet contains 0.015% by mass or more and 1.5% by mass or less of Cu.
In the heat exchanger of the present invention, the Al-Cu brazing, Al-Cu-Zn brazing, Al-Si-Cu brazing, or Al-Si-Cu-Zn brazing generated on the surface of the aluminum alloy tube during the brazing. It is preferable to have a Cu enrichment portion by aggregation with respect to the fillet.
In the heat exchanger of the present invention, it is preferable to have a sacrificial anode layer by diffusion of Si and Zn on the surface by brazing.
In the heat exchanger of the present invention, the Cu concentration on the outermost surface of the tube after brazing is preferably less than 0.5% by mass.

According to the heat exchanger provided with the aluminum alloy tube for the heat exchanger of the present invention, the amount of Cu, the amount of Zn, and the amount of Si in the organic copper compound contained in the brazing coating film formed on the tube are appropriately set. By controlling to, an appropriate amount of Cu and Zn can be diffused into the fillet generated after brazing. As a result, it is possible to provide a heat exchanger provided with an aluminum alloy tube for a heat exchanger in which the progress of corrosion is small in the fillet and the fins are less likely to peel off even when the fillet is used for a long period of time in a corroded environment.

Further, according to the heat exchanger provided with the aluminum alloy tube for the heat exchanger of the present invention, since the fins are difficult to separate even in a corrosive environment, the sacrificial anticorrosion effect of the tube by the fins can be obtained for a longer period of time. As a result, the corrosion life of the tube can be extended as compared with the conventional one, the fin peelability can be improved, and two characteristics that are difficult to achieve at the same time can be satisfied.

It is a front view which shows an example of the structure of the heat exchanger which concerns on this invention. FIG. 3 is a partially enlarged cross-sectional view showing a state in which a header pipe, a tube and fins are assembled and brazed in the heat exchanger according to the present invention. FIG. 3 is a partially enlarged cross-sectional view showing a state in which a header pipe, a tube and fins are assembled before brazing in the heat exchanger according to the present invention.

In the aluminum alloy tube for a heat exchanger of the present embodiment, a brazing coating film composed of a Cu component, Si powder, a Zn-containing flux and a binder, in which an organic copper compound or a part thereof is supplied as a metallic Cu powder, is formed on the surface thereof. Can be adopted.
More specifically, in the aluminum alloy tube for a heat exchanger of the present embodiment, the amount of Cu as a Cu component in which an organic copper compound or a part thereof is supplied as a metallic Cu powder: 0.01 to 0.5 g / m ² , Si. A brazing coating film consisting of powder: 1 to 5 g / m ² , Zn-containing flux: ^{2 to} 10 g / m 2, and binder: 0.5 to 3.5 g / m ² is formed on the surface.
In the brazing coating film, the amount of Cu as a Cu component to which an organic copper compound or a part thereof is supplied as a metallic Cu powder: 0.01 to 0.5 g / m ² , and Si powder: 1 to 5 g / m ² , Zn-containing flux: ^{2 to} 10 g / m 2, Zn-free flux: 1 to 10 g / m ² , and binder: 0.5 to 3.5 g / m ² , a brazing coating film may be used.
The inventors have studied the corrosion mechanism of the joints of the components in aluminum alloy heat exchangers manufactured by brazing, with tubes, fins and header pipes as the main components. As a result, in order to prevent the fillets at the fin joints from corroding preferentially and the fins from separating from the tube, the relationship between the amount of Cu and the amount of Zn in the brazing coating film was studied and these were appropriate. We have found that the above problems can be solved by prescribing the relationship.
It is believed that the preferential corrosion of the fillet is caused by the potential of the fillet being lower (base) than the potential of the sacrificial anode fin. Therefore, as a result of repeated studies on the composition of the coating film forming the fillet, the present invention was reached.

Hereinafter, the present invention will be described in detail based on the embodiments shown in the accompanying drawings.
FIG. 1 shows an example of a heat exchanger according to the present invention. The heat exchanger 100 is parallel to the header pipes 1 and 2 arranged in parallel to the left and right, and is parallel to each other with a distance between the header pipes 1 and 2, and with respect to the header pipes 1 and 2. It is mainly composed of a plurality of flat tubes 3 joined at right angles to each other and corrugated fins 4 attached to each tube 3. The header pipes 1 and 2, the tube 3 and the fin 4 are made of an aluminum alloy described later.

More specifically, a plurality of slits 6 are formed on the facing side surfaces of the header pipes 1 and 2 at regular intervals in the length direction of each pipe, and the tube 3 is formed in the facing slits 6 of the header pipes 1 and 2. A tube 3 is erected between the header pipes 1 and 2 through the end portion. Further, fins 4 are arranged between a plurality of tubes 3 and 3 erected between the header pipes 1 and 2 at predetermined intervals, and these fins 4 are brazed to the front surface side or the back surface side of the tubes 3.
That is, as shown in FIG. 2, a fillet 8 is formed by a brazing material at a portion where the end portion of the tube 3 is inserted through the slit 6 of the header pipes 1 and 2, and the tube 3 is brazed to the header pipes 1 and 2. Has been done. Further, in the corrugated fin 4, the fillet 9 is formed by the brazing material generated in the portion between the front surface or the back surface of the adjacent tube 3 with the apex portion of the wave facing each other, and the front surface side and the back surface side of the tube 3 are formed. The corrugated fin 4 is brazed to the surface.
In the heat exchanger 100 of the present embodiment, as described in detail in the manufacturing method described later, the header pipes 1 and 2 and a plurality of tubes 3 and a plurality of fins 4 erected between them are assembled in FIG. As shown, it is manufactured by forming a heat exchanger assembly 101, heating it and brazing it.

In the tube 3 before brazing, the amount of Cu as a Cu component supplied as an organic copper compound or a metal Cu powder in addition to the front surface and the back surface to which the fin 4 is bonded: 0.01 to 0.5 g / m. ² , Si powder: 1 to 5 g / m ² , Zn-containing flux (KZnF ₃ ^{): 2 to} 10 g / m 2, binder (for example, acrylic resin): 0.5 to 3.5 g / m ² with brazing The coating film 7 is formed. Further, on the front surface and the back surface of the tube 3, the amount of Cu as a Cu component supplied as an organic copper compound or a metallic Cu powder in addition to the organic copper compound: 0.01 to 0.5 g / m ² , Si powder: 1 to 5 g / m. ^2. Zn-containing flux (KZnF ₃ ^{): 2 to} 10 g / m 2, Zn-free flux: 1 to 10 g / m ² , binder (for example, acrylic resin): 0.5 to 3.5 g / m ^2. The brazing coating film 7 may be formed.
The tube 3 of the present embodiment has a plurality of passages 3c formed therein, and includes a flat front surface (upper surface) 3A and a back surface (lower surface) 3B, and side surfaces adjacent to the front surface 3A and the back surface 3B. It is configured as a flat multi-hole tube. As an example, in the present embodiment, the brazing coating film 7 is formed on the front surface 3A and the back surface 3B of the tube 3 before brazing.

Hereinafter, the composition constituting the brazing coating film will be described.
<Organocopper compound powder, Cu powder>
Cu in the organic copper compound powder or Cu as a Cu component in the Cu powder is concentrated in the fillet 9 by heat treatment at the time of brazing, and the potential of the fillet 9 is more noble than in the case where Cu is not contained. The corrosion resistance is improved to improve the peelability of the fin 4 in a corrosive environment.
Specifically, copper naphthenate powder, oxine copper powder, hydroxynoline copper powder and the like can be used as the organic copper compound powder.
Cu amount as Cu component when organic copper compound powder or metallic Cu powder is added in addition to it: 0.01 to 0.5 g / m ²
When the amount of Cu as a Cu component when the organic copper compound powder or the metal Cu powder is added ^{is less than 0.01 g / m 2} , the effect of improving the fin peeling resistance by the fillet 9 is small, and the organic copper compound powder If the amount of Cu in the ^{tube exceeds 0.5 g / m 2} , it becomes difficult to prepare a sacrificial anode layer on the tube surface.

<Si powder>
The Si powder reacts with Al constituting the tube 3 to form a wax that joins the fin 4 and the tube 3, but the Si powder melts into a brazing liquid at the time of brazing. Zn in the flux diffuses in this waxy liquid and spreads uniformly on the surface of the tube 3. Since the diffusion rate of Zn in the brazing solution, which is the liquid phase, is significantly higher than the diffusion rate in the solid phase, the Zn concentration on the surface of the tube 3 becomes almost uniform, whereby a uniform Zn diffusion layer is formed, and the tube 3 is formed. Corrosion resistance can be improved.

Si powder coating amount: 1-5 g / m ²
If the coating amount of Si powder ^{is less than 1 g / m 2} , the brazing property is lowered. On the other hand, when the coating amount of Si powder ^{exceeds 5 g / m 2} , Zn is likely to be concentrated in the fillet due to excessive brazing, unreacted Si residue is generated, the corrosion depth of the tube is increased, and the fins are formed. The desired effect of trying to prevent separation cannot be obtained. Therefore, the content of Si powder in the coating film is set to 1 to 5 g / m ² . Preferably, the content of the Si powder in the coating film is 1.5 to 4.5 g / m ² , more preferably 2.0 to 4.0 g / m ² . The particle size of the Si powder used here is, for example, D (99) of 15 μm or less. D (99) is a diameter at which the volume-based integrated particle size distribution from the small diameter grain side is 99%.

<Zn-containing flux, Zn-free flux>
The Zn-containing flux has the effect of forming a Zn diffusion layer on the surface of the tube 3 during brazing and improving pitting corrosion resistance. Further, it has an effect of removing oxides on the surface of the tube 3 at the time of brazing, promoting the spread of the filter and wetting, and improving the brazing property. Since this Zn-containing flux has higher activity than the Zn-free flux, good brazing property can be obtained even if a relatively fine Si powder is used.
The Zn-free flux is composed of K ₃ AlF ₃ + KAlF ₄ , or fluoride-based such as LiF, KF, CaF ₂ , AlF ₃ , SiF ₄ , and chloride-based such as KCl, BaCl, and NaCl. be. Commercially available products (products) include, for example, NOCOLOK FLUX (NOCOLOK FLUX is a registered trademark of Solvay Fluol), which is a flux containing potassium tetrafluoride aluminum as a main component and has various additives. are known composition _is intended and the K ₃ AlF ₃ + KAlF becomes ₄ composition, Nocolok Sil flux (KAlF ₄ + Si powder), it can be exemplified such as Nocolok Cs flux. In addition, nocoloc flux added with fluoride such as LiF, KF, CaF ₂ , AlF ₃ , and SiF _{4 can also be used.}
By using a Zn-containing flux or adding these Zn-free fluxes in addition to the Zn-containing flux, it contributes to the improvement of brazing property.

"Zn-containing flux coating amount: ^{2 to} 10 g / m 2"
If the coating amount of the Zn-containing flux ^{is less than 2 g / m 2} , the formation of the Zn diffusion layer becomes insufficient, and the corrosion resistance of the tube 3 is lowered. In addition, insufficient destruction and removal of the surface oxide film of the brazing material (tube 3) causes poor brazing. On the other hand, when the coating amount ^{exceeds 10 g / m 2} , Zn concentration in the fillet becomes remarkable, the corrosion resistance of the fillet decreases, and fin separation is accelerated. Therefore, the coating amount of the Zn-containing flux is set to ^{2 to 10 g / m 2.}
Zn-containing flux, it is preferable to use a KZnF ₃ mainly, in KZnF _3, if _{necessary, K 1-3 AlF 4-6, Cs 0.02} K 1-2 AlF 4-5, AlF 3, A mixed type flux in which a flux containing no Zn such as KF or K ₂ SiF _{6 is mixed may be used.} The coating amount may be as long as the Zn-containing flux is in the range of ^{2 to 10 g / m 2.}
"Zn-free flux coating amount: 1 to 10 g / m ² "
If the amount of Zn-free flux applied is ^{less than 1 g / m 2} , the effect of adding Zn-free flux cannot be obtained, and if the amount of Zn-free flux applied exceeds 10 g / m ² , the fluidity of the wax becomes excessive. There is a problem that Zn is concentrated in the fillet more than expected due to the improvement to the above, which leads to fin peeling.

<Binder>
The coating film contains an organic copper compound powder or a mixed powder in which a metal Cu powder is added in addition to the powder, Si powder, a Zn-containing flux, and a binder. Further, the coating film may contain a binder in addition to the organic copper compound powder or a powder obtained by substituting a part thereof with the metal Cu powder, Si powder, Zn-containing flux, and Zn-free flux. As an example of the binder, an acrylic resin can be preferably mentioned.
Binder application amount: 0.5-3.5 g / m ²
When the coating amount of the binder ^{is less than 0.5 g / m 2} , the hardness of the coating film is lowered and the processability (peeling resistance of the coating film) is lowered. On the other hand, when the coating amount of the binder ^{exceeds 3.5 g / m 2} , the brazing property is lowered due to the influence of the fillet not formed due to the unreacted coating film. Therefore, the amount of the binder applied is preferably ^{0.5 to 3.5 g / m 2.} The binder is usually transpired by heating during brazing.

The method for applying a brazed composition obtained by adding an organic copper compound powder or a metallic Cu powder, a Si powder, a Zn powder, a Zn-containing flux and a binder, or a non-Zn-containing flux to these is particularly limited in the present invention. It can be carried out by an appropriate method such as a spray method, a shower method, a flow coater method, a roll coater method, a brush coating method, a dipping method, and an electrostatic coating method. Further, the coating region of the brazing composition may be the entire front surface of the tube 3 or a partial front surface or back surface of the tube 3, and the point is that at least the fins 4 are brazed. It suffices if it is applied to the surface area of the tube 3 required for the above. Further, in order to apply the brazing composition to the tube 3, a solvent such as isopropyl alcohol is appropriately added to the brazing composition to adjust the viscosity so that the brazing composition can be applied by the above-mentioned coating method. Is preferable.

The tube 3 is an aluminum alloy containing Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: 0.05% or less in mass%, and the balance is unavoidable impurities and aluminum. It is preferably composed of. The tube 3 is made by extruding these aluminum alloys.
Hereinafter, the reasons for limiting each constituent element of the aluminum alloy constituting the tube 3 will be described.

<Si: 0.05 to 1.0%>
Si is an element having a strength improving effect like Mn.
If the Si content is less than 0.05%, the effect of improving the strength is insufficient. On the other hand, if Si is contained in an amount of more than 1.0%, the extrudability is lowered. Therefore, the Si content of the tube 3 in the present invention is preferably set to 0.05 to 1.0%.
<Mn: 0.1 to 1.5%>
Mn is an element that improves the corrosion resistance of the tube 3 and also improves the mechanical strength. Mn also has the effect of improving the extrudability during extrusion molding. Further, Mn has the effect of suppressing the fluidity of wax and reducing the difference in Zn concentration between the fillet and the tube surface.
If the Mn content is less than 0.1%, the effect of improving corrosion resistance and strength is insufficient, and the effect of suppressing the fluidity of wax is also reduced. On the other hand, if Mn is contained in an amount of more than 1.5%, the extrudability is lowered due to the increase in extrusion pressure. Therefore, the Mn content in the present invention is preferably 0.1 to 1.5%.

<Cu: 0.05% or less>
Cu is an element that affects the corrosion resistance of the tube 3. If it is 0.05% or less, there is no problem, but if it is contained in excess of 0.05%, the corrosion resistance decreases due to the increase in the self-corrosion rate, and the sacrificial anode on the tube surface. Layer formation tends to be difficult.

Next, the fin 4 will be described.
The fins 4 bonded to the tube 3 are in mass%, Zn: 0.3 to 5.0%, Mn: 0.5 to 2.0%, Fe: 1.0% or less, Si: 1.5%. It is preferably composed of an aluminum alloy containing the following, with the balance unavoidable impurities and aluminum.
The fin 4 is formed into a corrugated shape by melting an aluminum alloy having the above composition by a conventional method and passing through a hot rolling step, a cold rolling step and the like. The method for manufacturing the fin 4 is not particularly limited in the present invention, and a known manufacturing method can be appropriately adopted. Hereinafter, the reasons for limiting each constituent element of the aluminum alloy constituting the fin 4 will be described.

<Zn: 0.3 to 5.0%>
By containing Zn in the fin 4, the potential of the fin 4 can be lowered to impart a sacrificial anticorrosion effect to the fin 4.
The Zn content in the fin 4 needs to be 0.3% or more and 5.0% or less in terms of mass%. If the Zn content in the fin 4 is less than 0.5%, the sacrificial anticorrosion effect is reduced, and if the Zn content is more than 5%, the self-corrosion resistance tends to be lowered.
<Mn: 0.5 to 2.0%>
Mn improves the strength of the fin 4 and also improves the corrosion resistance.
If the Mn content is less than 0.5%, the effect of improving the strength at high temperature and room temperature is insufficient, while if the Mn content exceeds 2.0%, the processability is insufficient when producing the fin 4. do. Therefore, the Mn content in the alloy constituting the fin is set to 0.5 to 2.0%.

<Si: 1.5% or less>
By containing Si, a compound with Mn is formed so that the strength improving effect can be exhibited. When the Si content is out of the above range, fin separation is likely to occur.
<Fe: 1.0% or less>
Fe improves the corrosion resistance, but when the Fe content exceeds 1.0%, the self-corrosion rate of the fin 4 itself increases, so that the corrosion resistance decreases.

Next, a method of manufacturing the heat exchanger 100 having the header pipes 1, 2 tubes 3 and fins 4 as the main components described above will be described.
FIG. 3 shows a heat exchanger assembly 101 showing a state in which the header pipes 1, 2, the tube 3 and the fin 4 are assembled by using the tube 3 in which the brazing coating film 7 is applied to the joint surface with the fin 4. It is a partially enlarged view of, and shows the state before heating brazing. In the heat exchanger assembly 101 shown in FIG. 3, the tube 3 is attached by inserting one end thereof into a slit 6 provided in the header pipe 1.

When the heat exchanger assembly 101 composed of the header pipes 1, 2, tubes 3 and fins 4 assembled as shown in FIG. 3 is heated to a temperature equal to or higher than the melting point of the brazing material and cooled after heating, the brazing material layer 13, The brazing coating film 7 is melted and the header pipe 1 and the tube 3 and the tube 3 and the fin 4 are joined as shown in FIG. 2, respectively, to obtain a heat exchanger 100 having the structures shown in FIGS. 1 and 2. At this time, the brazing filler metal layer 13 on the inner peripheral surface of the header pipe 1 melts and flows in the vicinity of the slit 6 to form a fillet 8 and the header pipe 1 and the tube 3 are joined to each other. Further, the brazing coating film 7 on the surface of the tube 3 melts into Al-Cu wax or Al-Si-Cu wax, which flows in the vicinity of the fin 4 due to the capillary force to form a fillet 9, and the tube 3 and the fin 4 are formed. Is joined.

At the time of brazing, the brazing coating film 7 and the brazing material layer 13 are melted by heating to an appropriate temperature in an appropriate atmosphere such as an inert atmosphere. Then, the activity of the flux increases, Zn in the flux precipitates on the surface of the brazed material (tube 3) and diffuses in the thickness direction thereof, and in addition, the surfaces of both the brazed material and the brazed material are surfaced. It destroys the oxide film of the wax and promotes wetting between the brazing material and the brazed material.
The conditions for brazing are not particularly limited. As an example, the inside of the furnace is set to a nitrogen atmosphere, the heat exchanger assembly 101 is heated to a brazing temperature (substantial reaching temperature) of 580 to 620 ° C at a heating rate of 5 ° C./min or more, and held at the brazing temperature for 30 seconds or more. Then, the cooling may be performed by setting the cooling rate from the brazing temperature to 400 ° C. to 10 ° C./min or more.

Upon brazing, a part of the matrix of the aluminum alloy constituting the tube 3 and the fin 4 reacts with the composition of the brazing coating film 7 applied to the tube 3 (Al-Cu wax, Al-Cu-Zn). It spreads as one or more of brazing, Al-Si-Cu brazing, and Al-Si-Cu-Zn brazing), and the tube 3 and the fin 4 are brazed. On the surface of the tube 3, the Zn in the flux is diffused by brazing and becomes more base than the inside of the tube 3. Further, in the fillet 9, Cu in the organic copper compound powder existing in the coating film becomes wax, and then the wax is concentrated by collecting the wax to form a Cu enrichment portion, which is more fillet than in the case where Cu is not contained. The potential of 9 is noble. Therefore, the fillet 9 is less likely to be corroded.
The amount of Cu contained in the fillet 9 varies depending on the amount of Cu contained in the brazing coating film 7 and the amount of Cu contained in the tube 3, and the diffusion of Cu from the coating film 7 and the diffusion of Cu from the tube 3 Affected by. Considering that the minimum value of the amount of Cu contained in the coating film 7 is 0.01 g / m ² and the amount of Cu contained in the tube 3 is 0.01 to 0.05% by mass, the following Examples will be used. Considering the amount of Cu in the fillet, the amount of Cu in the fillet should be in the range of 0.015% by mass or more and 1.5% by mass or less in order to balance corrosion resistance, brazing resistance, and fin peeling resistance. Is preferable.

According to this embodiment, at the time of brazing, there is no residue of Si powder, good brazing is performed, a fillet 9 is surely formed between the tube 3 and the fin 4, and the fillet 9 is also less likely to be corroded. ..
In the obtained heat exchanger 100, an appropriate Zn layer is formed on the surface of the tube 3 to prevent pitting corrosion, and corrosion of the fillet 9 is suppressed by concentrating Cu from the organic copper compound, so that the fillet 9 has a heat exchanger 100. Since it is unlikely to fall off, the tube 3 and the fin 4 remain securely bonded for a long period of time, and good heat exchange performance is maintained. That is, it is possible to provide a heat exchanger 100 in which pitting corrosion is less likely to occur in the tube 3, the tube 3 itself is excellent in corrosion resistance, and the fillet 9 is less likely to fall off due to the suppression of corrosion of the fillet 9.

Tubes were prepared by extrusion from Al alloys having the compositions shown in Tables 1, 2 and 3, and fins were prepared from the Al alloys having the compositions shown in Tables 1, 2 and 3. In the Al alloy constituting the tube and fin, the components contained in addition to the compositions shown in Tables 1 and 2 are unavoidable impurity elements and the balance of Al.
After homogenizing the heat treatment of the Al alloy for the tube, a tube (thickness t: 0.3 mm × width W: 18 mm × total thickness T: 1.3 mm, 19-hole flat extruded porous tube was produced by hot extrusion.
The Al alloy for fins was homogenically heat-treated and then hot-rolled and cold-rolled to obtain a plate material having a thickness of 0.08 mm. Fins were produced by corrugating this plate material.
Next, the brazing filler metal composition was rolled and dried on the surface of the tube at 150 ° C. for 3 minutes.

The brazing filler metal composition is an organic copper compound (added in the form of a liquid in which copper naphthenate is dissolved in a mineral spirit (gasoline-based solvent)), Si powder (D (99) particle size 15 μm: D (99) is small particles. It is a paint composed of a volume-based integrated particle size distribution from the diameter side of 99%), a Zn flux (KZnF ₃ ), a binder (acrylic resin), and a solvent (including alcohol such as isopropyl alcohol). As this brazing composition, the composition ratio shown in Table 1 was used. Regarding the organic copper compound, the liquid substance used was analyzed, the amount of Cu actually contained was grasped, and the amount of Cu was converted and described in the table described later. Further, in some samples, in addition to the amount of Cu contained in the organic copper compound, a part of the amount of Cu was added in the state of metallic Cu powder.

Next, the tubes and fins are assembled as part of the heat exchanger assembly as shown in FIG. 3, and the assembly is brazed under the conditions of heating to 600 ° C. in a heating furnace, holding for 2 minutes, and then cooling. Went. In each case, brazing was performed in a furnace in a nitrogen gas atmosphere.
The brazed tubes and fins were subjected to a SWAAT 40-day corrosion test, and the maximum corrosion depth generated in the tubes after the test was measured. The results are shown in the columns of corrosion resistance (* ^{1) in Tables 4 to 6.}

In the evaluation of brazing property, the reactivity of the coating film after brazing was visually evaluated. Examples of complete reaction are marked with ◎, examples of slight residue being seen at the end of the tube but not affecting performance are marked with ○, examples of partial reaction are marked with △, and unreacted examples are marked with ×. It was certified as, and it is shown in the column ^{of brazing property (* 2) in Tables 4 to 6.}
The fin peeling resistance was evaluated by subjecting the brazed tube and fins to a corrosion test on SWAAT 40 days and measuring the peeling strength after the test. The peel strength was evaluated by a value of (strength after 40 days of SWAAT / strength before SWAAT test) × 100.
The evaluation criteria are as follows: 100 to 75% examples are marked with ◎, 74 to 50% are marked with ○, 49 to 25% are marked with △, and 24 to 0% are marked with ×. It is shown in the column of fin peeling resistance (* ^{3) in Table 6.}

Regarding extrudability, the extrusion pressure, extrusion speed, and tube surface condition during extrusion molding of the tube were comprehensively evaluated, and examples where the extrusion pressure was too high to extrude were generated, and a large number of surface defects such as pickups were generated. Examples are indicated by x, with almost no surface defects, and extrusion pressure and extrusion speed values (if the extrusion pressure is lower than the target extrusion speed, the lower the extrusion pressure, the better the extrusion performance). Gender was evaluated.
Compared with AA standard 3102 and 3003 alloys, which are well-known as aluminum alloys, if the extrudability is equal to or higher than the 3102 alloy, it is marked with ◎, if it is inferior to the 3102 alloy but better than the 3003 alloy, it is marked with ○, which is equivalent to the 3003 alloy. If it is, it is recognized as a Δ mark, and if it is inferior to the 3003 alloy, it is recognized as a × mark, and it is shown in the column ^{of extrudability (* 4) in Tables 4 to 6.}

The coating film hardness was described in the column ^{of coating film hardness (* 5} ) in Tables 4 to 6 after the coating film was applied and dried, and the coating film hardness was measured by a pencil scratch test.
Regarding fin workability, the mold wearability is used as an evaluation standard, and if the workability is equal to or higher than that of the 3403 alloy and 3009 alloy, it is ◎, and if it is inferior to the 3403 alloy but better than the 3009 alloy, it is marked with ○. , If it is equivalent to the 3009 alloy, it is marked with a Δ, and if it is inferior to the 3009 alloy, it is marked with a cross, and it is described in the column ^{of coating hardness (* 6) in Tables 4 to 6.}
The amount of Cu in the fillet is described in the column of the amount of Cu in the fillet (* ^{7) in Tables 4 to 6.} The above results are shown in Tables 1 to 6 below.

The following results were obtained from the test results shown in Tables 1 to 6.
Cu amount in organic copper compound powder (some samples have a part of Cu amount added as metallic Cu powder): 0.01 to 0.5 g / m ² , Si powder: 1 to 5 g / m ² , Zn contained A tube having a coating film for brazing having a flux: ^{2 to} 10 g / m 2 and a binder: 0.5 to 3.5 g / m ² formed on the surface is combined with fins and heated by brazing. We were able to form a fillet that joins the fins and tubes. It was confirmed that Cu diffused from the Cu powder was concentrated in the fillet, and Si and Zn were diffused on the tube surface to form a sacrificial anode layer.
Further, it was found that the samples of Examples 51 to 56 to which Cu was added in the state of metallic Cu powder in addition to Cu supplied as the organic copper compound powder also obtained excellent effects as in the other examples. ..

Using the brazing coating film having the above composition, the composition of the tube was Si: 0.05 to 1.0% by mass, Mn: 0.1 to 1.5% by mass, Cu: 0.5% by mass or less, and the balance. It has an unavoidable impurity and aluminum composition, and the fin composition is Zn: 0.2 to 5.0% by mass, Mn: 0.5 to 2.0% by mass, Fe: 1.0% by mass or less, Si: A combination having 1.5% by mass or less, residual unavoidable impurities and a composition of aluminum is excellent in corrosion resistance, brazing resistance, fin peeling resistance and extrusion property, high coating film hardness, tube strength, fin strength and fin processing. It has become clear that it is possible to provide a heat exchanger with excellent properties.
Further, in Examples 14, 40, 42, 44, 46 and Comparative Example 13, a large amount of Cu is contained in the tube, and the amount of Cu is concentrated in the fillet, so that the amount of Cu in the fillet (% by mass) is increased. ..

Comparative Example 1 has a small amount of Cu in the fillet and is inferior in fin peeling resistance, Comparative Example 2 has an excessive amount of Cu in the paint and causes a problem in corrosion resistance, and Comparative Example 3 has a small amount of Si powder and is inferior in fin peeling resistance. In Comparative Example 4, the amount of Si powder was too large, which caused a problem in brazing property.
In Comparative Example 5, the Zn-containing flux content was as ^{small as 1.0 g / m 2} , which caused a problem in corrosion resistance, and in Comparative Example 6, the Zn-containing flux content was as high as 11.0 g / m ² , which caused a problem in fin peeling resistance. ..
Comparative Example 7 was a sample having an excessively small amount of binder and had a low coating film hardness, and Comparative Example 8 was a sample having an excessive amount of binder and had problems in brazing property and fin peeling resistance.

Comparative Example 9 is a sample having a low Si content in the tube and the tube strength is slightly low, and Comparative Example 10 is a sample having a high Si content in the tube, which is inferior in extrudability and the tube strength is too high.
Comparative Example 11 is a sample having a low Mn content in the tube and is inferior in corrosion resistance and the tube strength is slightly low, and Comparative Example 12 is a sample having a high Mn content in the tube and is inferior in extrudability and the tube strength is too high. ..
Comparative Example 13 was a sample having a high Cu content in the tube and tended to be inferior in corrosion resistance.
Comparative Example 14 was a sample having a low Zn content of fins and was inferior in corrosion resistance, and Comparative Example 15 was a sample having a high Zn content of fins and had deteriorated fin peeling resistance.
Comparative Example 16 is a sample having a low Mn content of fins and is inferior in fin peeling resistance and has a low fin strength. Comparative Example 17 is a sample having a high Mn content of fins and the fin strength has increased too much. The sex has deteriorated.
In Comparative Example 18, since the Fe content of the fins was high, the fin peeling resistance was inferior, and in Comparative Example 19, since the Si content of the fins was too high, the fin strength became too high and the fin processability deteriorated.

Further, it is considered that as the amount of Cu in the coating film increases, the amount of Cu concentrated in the fillet after brazing also increases. Table In the embodiment shown in 1, Cu content in the coating film contains Cu of 0.1 wt% to fillet in the case of 0.05 g / ^{m 2,} Cu amount is 0.5 g / ^{m 2} in the coating In the case of, the fillet contains 1.5% by mass of Cu, and when the amount of Cu in the coating film is 0.01 g / m ² , the fillet contains 0.015% by mass of Cu. Further, the amount of Cu contained in the tube is 0.05% by mass or less in consideration of self-corrosion resistance.
From these facts, it can be estimated that the amount of Cu contained in the fillet is more preferably in the range of 0.015% by mass or more and 1.5% by mass or less.

According to the present invention, it is possible to provide a heat exchanger having excellent corrosion resistance because the fins are difficult to separate from the tube even in a corrosive environment.

Claims (5)

Brazing with an aluminum alloy tube for a heat exchanger in which a coating film for brazing consisting of a Cu component, Si powder, and a Zn-containing flux and a binder, in which an organic copper compound or a part thereof is supplied as a metallic Cu powder, is formed on the surface. A heat exchanger having fins that form a fillet and are joined to the tube.
The aluminum alloy tube is an aluminum alloy having a composition of Si: 0.05 to 1.0% by mass, Mn: 0.1 to 1.5% by mass, Cu: 0.05% by mass or less, residual unavoidable impurities, and aluminum. Consists of extruded pipe
The brazing coating has an amount of Cu as a Cu component to which an organic copper compound or a part thereof is supplied as a metallic Cu powder: 0.01 to 0.5 g / m ² , and Si powder: 1 to 5 g / m ^2. , Zn-containing flux: ^{2 to} 10 g / m 2, binder: 0.5 to 3.5 g / m ² for brazing coating.
The fins are Zn: 0.3 to 5.0% by mass, Mn: 0.5 to 2.0% by mass, Fe: 1.0% by mass or less, Si: 1.5% by mass or less, the balance of unavoidable impurities and A heat exchanger characterized by being made of an aluminum alloy having a composition of aluminum. The heat exchanger according to claim 1, wherein the fillet contains 0.015% by mass or more and 1.5% by mass or less of Cu. Cu enrichment part by aggregation of Al-Cu wax, Al-Cu-Zn wax, Al-Si-Cu wax, or Al-Si-Cu-Zn wax generated on the surface of the aluminum alloy tube during the brazing with respect to the fillet. The heat exchanger according to claim 2, wherein the heat exchanger is characterized by having. A heat exchanger according to any one of claims 1 to 3, characterized in that it comprises a sacrificial anode layer due to the diffusion of Si and Zn on the surface by brazing. Heat exchanger excellent in corrosion resistance and fin peelability according to any one of claims 1 to 4 in which the Cu concentration of the tube outermost surface after the brazing and less than 0.5 wt% vessel.

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