JP7012529B2 - Single-sided wax fin material for heat exchangers and heat exchangers and their manufacturing methods - Google Patents

Description

The present invention relates to a single-sided wax fin material for a heat exchanger, a heat exchanger, and a method for manufacturing the same.

The aluminum heat exchanger is a brazing type heat exchanger that combines a flat aluminum tube and corrugated fins and joins them with metal by brazing, and a copper tube and fins are combined and then the copper tube is expanded to expand the fins and copper. A tube expansion type heat exchanger that mechanically joins tubes is known.
The brazed type heat exchanger has a configuration in which corrugated fins are brazed and joined so as to sandwich the corrugated fins from above and below using a flat tube, whereas the expanded tube type heat exchanger has a fin provided with a round hole. A structure is adopted in which the fins and the copper tube are joined by inserting the copper tube and mechanically expanding the copper tube after the insertion.

Aluminum containing a specified amount of Si, Fe, Cu, Mn, and Mg as a plate material for a heat exchanger using a corrugated fin, and further containing one or more of Cr, Zr, Hf, Ti, and B in a specified amount. A brazing sheet in which a brazing material containing a specified amount or more of Si is clad on one side or both sides of a core material made of an alloy is known (see Patent Document 1).
This brazing sheet is characterized by being excellent in strength after brazing and heating, brazing property, repeated bending property, and pitting corrosion resistance.

Further, in a heat exchanger using corrugated fins, the corrugated fins are made of a brazing sheet made of an aluminum alloy, and one or more of Mn, Si, Fe, and Zn contained in the core material of the brazing sheet. A heat exchanger that defines the content and the amount of Si and Zn contained in the brazing filler metal layer is known (see Patent Document 2).
In this heat exchanger, when a brazing sheet is brazed, some Si remains on the surface of the brazing material, and if dew condensation water or the like is present here, the surface potential of the brazing material layer becomes noble due to the Si residue, and the core of the fin. A potential difference is generated between the material and the brazing material layer, and the problem that the amount of corrosion and wear of the fins increases is improved.

Japanese Unexamined Patent Publication No. 02-05934 Japanese Unexamined Patent Publication No. 2014-084521

In flat pipes applied to brazing type heat exchangers, sacrificial anticorrosion layers such as zinc sprayed layers are provided on both the upper and lower sides of the flat pipes in order to suppress leakage of refrigerant due to corrosion. Generally, a zinc sprayed layer is not provided on the short side surface of the flat tube.
If the sacrificial anticorrosion layer is not provided on the short side surface side of the flat tube, even if the sacrifice anticorrosion layer is provided on both the upper and lower sides of the flat tube, the sacrifice anticorrosion effect is insufficient depending on the length and width of the short side surface side. Therefore, there is a risk of corrosion on a part of the short side surface.
Further, in order to maintain the performance of the heat exchanger for a long period of time, it is necessary to suppress the falling off of the fins and the decrease in the heat transfer area of the fins due to corrosion.

In view of these backgrounds, the present invention can make the fins excellent in corrosion resistance, have a large remaining area of the fins even after long-term use, and have excellent corrosion resistance of the flat tube brazed to the fins. It is an object of the present invention to provide a single-sided brazing fin material for a heat exchanger, which is difficult to form a through hole in a flat tube and has excellent brazing properties, a heat exchanger, and a method for manufacturing the same.

The single-sided wax fin material for a heat exchanger of the present invention is a single-sided wax fin material applied to a heat exchanger in which a plurality of fins are brazed to a tube, and has a Si concentration gradient layer only on one side in the thickness direction. However, one- sided wax fins having a high Si concentration on one side in the thickness direction, no Si on the other side, or a region having a Si content of 0.15% by mass or less, and a potential difference of 10 mV or more on the front and back surfaces are generated. The fins are made of wood , the tube is a flat tube with short sides, the fins are brazed to the top or bottom of the tube except the short sides, and the fins are Si-free or Si content. The region of 0.15% by mass or less further comprises, in mass %, Mn: 0.7 to 2%, Zn 0.2 to 3%, the balance aluminum and an aluminum alloy having a composition of unavoidable impurities , as described above. It is characterized in that the potential difference between the short side surface side of the tube and the base side of the fin is 10 mV or more, and the heat exchanger is provided with the base side of the fin being baser than the short side surface side.

In the single-sided wax fin material for heat exchanger of the present invention, the tube contains Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: less than 0.1% in mass%. It is preferably made of an aluminum alloy containing, remaining unavoidable impurities and aluminum .
In the single-sided brazed fin material for heat exchangers of the present invention, it is preferable to have a sacrificial anode layer on the upper surface or the lower surface of the tube to which the fins are brazed .

The heat exchanger of the present invention has a plurality of fins and a tube to which the plurality of fins are brazed, has a Si concentration gradient layer only on one side in the thickness direction, and Si on one side in the thickness direction. The fin is composed of a single-sided wax fin material having a high concentration , containing no Si on the opposite surface side, or having a region having a Si content of 0.15% by mass or less, and having a potential difference of 10 mV or more on the front and back surfaces. The tube is a flat tube having a short side surface, the fins are brazed to the upper surface or the lower surface excluding the short side surface, the potential difference between the short side surface side of the tube and the base side of the fin is 10 mV or more, and the short side surface side. The base side of the fin is more base than the fin, and the region of the fin containing no Si or having a Si content of 0.15% by mass or less is further mass%, Mn: 0.7 to 2%, Zn0.2. It is characterized by being composed of an aluminum alloy containing up to 3% and having a composition of residual aluminum and unavoidable impurities.
In the heat exchanger of the present invention, the tube contains Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: less than 0.1% in mass%, and the balance. It is preferably made of an aluminum alloy consisting of unavoidable impurities and aluminum.
In the heat exchanger of the present invention, it is preferable to have a sacrificial anode layer on the upper surface or the lower surface of the tube to which the fins are brazed.

The method for manufacturing a heat exchanger according to the present invention is one side of a core material made of an aluminum alloy having a composition of Mn: 0.7 to 2%, Zn 0.2 to 3%, balance aluminum and unavoidable impurities in% by mass. Only a single-sided wax fin material for heat exchangers having a Si-containing layer containing Si: 2 to 12%, Zn: 0.3% or less, and Sr: 0.01 to 0.1% in mass% is used and short. A method for manufacturing a heat exchanger in which the one-sided brazing filler metal is brazed to the upper surface or the lower surface excluding the short side surface of a flat tube having a side surface, and the thickness of the one-sided brazing filler metal after brazing. It is characterized in that a concentration gradient of Si having a high Si concentration on one side in the longitudinal direction and a low Si concentration on the opposite side is generated, and a potential difference between the front and back surfaces of the one-sided wax fin material is generated by 10 mV or more .
In the method for manufacturing a heat exchanger according to the present invention, the tube is made of Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: less than 0.1% in mass%. It is characterized by using a tube containing an aluminum alloy containing unavoidable impurities and aluminum.
In the method for manufacturing a heat exchanger according to the present invention, it is preferable to form a sacrificial anode layer on the upper surface or the lower surface of the tube to which the fins are brazed.

In the case of the fin material for heat exchanger of the present invention, the Si-containing layer is provided only on one side of the core material, and after brazing, the Si concentration is high on one side in the thickness direction and the Si concentration is high on the opposite side. Since a low Si concentration gradient can be generated and a potential difference between the front and back surfaces is generated by 10 mV or more, the fin material can be potentially based with respect to the potential of the heat exchanger tube brazed to the fin material. Can be surface corrosion. Therefore, the tube brazed to the fin material can be prevented from corroding, and corrosion of the tube is less likely to proceed. Therefore, it is possible to provide a structure in which through holes are less likely to be formed in the tube due to corrosion even after long-term use. Therefore, it is possible to provide a heat exchanger that is less likely to cause refrigerant leakage from the tube.
In addition, the core material of the fin can be potentially based to cause planar corrosion, the heat transfer area of the fin can be maintained for a long period of time, excellent heat exchange performance can be maintained for a long period of time, and the fin can also fall off. It is possible to provide a heat exchanger that is unlikely to occur.

When a heat exchanger in which a flat tube is brazed to fins is configured, the anticorrosion effect on the front and back sides of the flat tube can be obtained by adopting a configuration in which a sacrificial anode layer is provided on the front and back surfaces of the flat tube. If the sacrificial anode layer is not provided on the short side surface side of the flat tube, the sacrificial anticorrosion effect of the sacrificial anticorrosion layer on the front and back sides of the flat tube may not reach the entire short side surface side of the flat tube. Here, since the core material surface of the fins around it is potentially lower than the potential on the short side surface side of the flat tube, the fin core material corrodes in a planar manner, causing corrosion on the short side surface side of the flat tube. Can be suppressed. Therefore, it is possible to provide a heat exchanger capable of maintaining excellent heat exchange performance for a long period of time.

It is a front view which shows an example of the heat exchanger obtained by brazing the fin material which concerns on this invention to a tube. It is a partially enlarged sectional view which shows the state which the header pipe, the tube and the fin material were assembled and brazed in the same heat exchanger. It is a partially enlarged sectional view which shows the state which the header pipe, the tube and the fin material were assembled in the same heat exchanger before brazing. It is a partially enlarged view which shows the tube and fin material assembled before brazing in the same heat exchanger. It is a perspective view which shows the tube and fin material which were assembled before brazing in the same heat exchanger. It is a simplified figure which shows a part of the fins installed on the tube after brazing in the same heat exchanger. It is a simplified figure which shows a part of the fins installed under the tube after brazing in the heat exchanger. It is a graph which shows the concentration distribution of Si, Zn and Mn in the thickness direction in the fin for a heat exchanger which concerns on an Example. It is a graph which shows the concentration distribution of Si, Zn and Mn in the thickness direction in the fin for a heat exchanger which concerns on a comparative example.

Hereinafter, the present invention will be described in detail based on the first embodiment shown in the accompanying drawings.
FIG. 1 shows an example of a heat exchanger to which a fin material according to the present invention is applied. The heat exchanger 100 is parallel to the header pipes 1 and 2 arranged in parallel to the left and right, and the header pipes 1 and 2 are spaced apart from each other and parallel to the header pipes 1 and 2. It is mainly composed of a plurality of flat tubes (flat tubes) 3 joined at right angles and corrugated fins (corrugated fins) 4 brazed 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, as shown in FIGS. 2 and 3, a plurality of slits 6 are formed on the opposite side surfaces of the header pipes 1 and 2 at regular intervals in the length direction of each pipe, and the header pipes 1 and 2 have a plurality of slits 6. The tube 3 is erected between the header pipes 1 and 2 by inserting the end portion of the tube 3 into the slits 6 facing each other. 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, the first fillet portion 8 is formed by the brazing material at the 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 is formed with respect to the header pipes 1 and 2. 3 is brazed. Further, in the corrugated fin 4, the apex portion of the wave is opposed to the front surface or the back surface of the adjacent tube 3, and the brazing material generated in the portion between them forms the second fillet portion 9, and the surface of the tube 3 is formed. Corrugated fins 4 are brazed on the side and the back surface side.

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 erected between them and a plurality of fin materials 4A are assembled in FIG. 3 As shown in the above, the heat exchanger assembly 101 is formed, and the heat exchanger assembly 101 is heated and brazed to obtain the heat exchanger assembly 101. By heating during brazing, a sacrificial anode layer 3E made of a Zn melt diffusion layer, which will be described in detail later, is formed on the front surface side and the back surface side of the tube 3. Further, the fin material 4A becomes a fin 4 by brazing.

As shown in FIGS. 3 and 4, the tube 3 before brazing has Si powder: 1 to 5 g / m ² and a Zn-containing flux (KZnF ₃ ) on the front surface side and the back surface side where the fin material 4A is abutted. A brazing coating film 7 composed of: 3.0 to 20 g / m ² and a binder (for example, acrylic resin): 0.5 to 8.5 g / m ² is applied. Further, in the fin material 4A before brazing, the Si-containing layer 4b is formed only on one side of the core material 4a. In the form shown in FIG. 3, the Si-containing layer 4b is arranged at the upper end of the fin material 4A assembled below the tube 3, and the Si-containing layer 4b is arranged at the lower end of the fin material 4A assembled above the tube 3. Is placed. Therefore, the core material 4a at the lower end of the fin material 4 on the upper surface side of the tube 3 is arranged so as to be in contact with the brazing coating film 7, and the fin material 4 on the lower surface side of the tube 3 contains Si at the upper end. The layer 4b is arranged so as to be in contact with the brazing coating film 7.

As shown in FIG. 5, the tube 3 of the present embodiment has a flat tube shape having a small height (thickness) with respect to the width, a plurality of refrigerant passages 3C are formed therein, and a flat surface (a flat surface). It is a flat multi-hole tube including an upper surface) 3A and a back surface (lower surface) 3B, and a short side surface 3D adjacent to the front surface 3A and the back surface 3B. In the tube 3, the refrigerant passages 3C adjacent to the left and right are partitioned by a partition wall 3F. In the present embodiment, the brazing coating film 7 is applied to the front surface 3A and the back surface 3B of the tube 3 before brazing, but the brazing coating film 7 is not applied to the short side surface 3D. ..

Hereinafter, the composition constituting the brazing coating film 7 will be described.
<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 the uniform Zn melt diffusion layer (sacrificial anode layer) 3E. Is formed, and the corrosion resistance of the tube 3 can be improved.

"Si powder coating amount: 1 to 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, non-Zn-containing flux>
The Zn-containing flux has the effect of forming a sacrificial anode layer 3E 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 and wetting of the brazing, 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 non-Zn-containing flux has a composition of K ₃ AlF ₆ + KAlF ₄ , or a fluoride system such as LiF, KF, CaF ₂ , AlF ₃ , K ₂ SiF ₆ , and chlorides such as KCl, BaCl, and NaCl. There is a system. Commercially available products (products) include, for example, a fluoride-based flux or a potassium fluoroaluminate-based flux, which is a flux containing potassium tetrafluoroaluminum as a main component and has various compositions to which additives are added. It is known, and examples thereof include those having a composition of K ₃ AlF ₆ + KAlF ₄ and Cs _(x) K _(y) F _(z) . In addition, a fluoride-based flux or a potassium fluoroaluminate-based flux to which a fluoride such as LiF, KF, CaF ₂ , AlF ₃ , K ₂ AlF _{5.5H 2} O or the like is added can also be used.
By using a Zn-containing flux or adding these non-Zn-containing fluxes in addition to the Zn-containing flux, it contributes to the improvement of brazing property.

"Zn-containing flux coating amount: 3.0 to 20 g / m ² "
If the coating amount of the Zn-containing flux is less than 3.0 g / m ² , the formation of the sacrificial anode layer becomes insufficient, and the corrosion resistance of the first fillet portion 8 is lowered. On the other hand, when the coating amount exceeds 20 g / m ² , Zn concentration in the fillet portion becomes remarkable, the corrosion resistance of the fillet portion is lowered, and fin separation is accelerated. Therefore, the coating amount of the Zn-containing flux is set to 3.0 to 20 g / m ² .
It is preferable to use KZnF _{3 as the main component of the Zn-containing flux, but KZnF 3 can} be used as _K1-3 AlF _4-6 , Cs _{0.02 K1-2} AlF _4-5 , AlF ₃ , if necessary. A mixed type flux in which a Zn-free flux 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 3.0 to 20 g / m ² .
In addition, in order to display the numerical range in the present specification, when the upper limit value and the lower limit value are continuously expressed by using "-", the upper limit value and the lower limit value are included unless otherwise specified. Therefore, 3.0 to 20 g / m ² means 3.0 g / m ² or more and 20 g / m ² or less.

"Non-Zn-containing flux coating amount: 1 to 10 g / m ² "
If the non-Zn-containing flux coating amount is less than 1 g / m ² , the effect of adding the non-Zn-containing flux cannot be obtained, and if the non-Zn-containing flux coating amount exceeds 10 g / m ² , the fluidity of the wax is 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 brazing coating film 7 contains a binder in addition to Si powder, a Zn-containing flux, and a non-Zn-containing flux. Further, the non-Zn-containing flux may be omitted. As an example of the binder, an acrylic resin can be preferably mentioned.
"Binder coating amount: 0.2 to 8.3 g / m ² "
When the coating amount of the binder is less than 0.2 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 8.3 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 coating amount of the binder is preferably 0.2 to 8.3 g / m ² . The binder is usually transpired by heating during brazing.

The method for applying the brazed composition obtained by adding Si powder, Zn powder, Zn-containing flux and binder, or non-Zn-containing flux to these is not particularly limited in the present invention, and the spray method, shower method, and flow coater are not particularly limited. It can be carried out by an appropriate method such as a method, a roll coater method, a brush coating method, a dipping method, or 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 front surface region or the back surface region of the tube 3 required for the above. Further, in order to apply the brazing composition to the tube 3, a solvent such as 3-methoxy-3-methyl-1-butanol or isopropyl alcohol is appropriately added to the brazing composition to adjust the viscosity. It is preferable to enable coating by the above-mentioned coating method.

The tube 3 is an aluminum alloy containing Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: less than 0.1% by mass, and the balance is unavoidable impurities and aluminum. And so on. 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: 0.05-1.0%>
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: 0.1-1.5%>
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: less than 0.1%>
Cu is an element that affects the corrosion resistance of the tube 3, and if it is less than 0.1%, there is no problem, but if it is contained in 0.1% or more, the corrosion resistance decreases due to the increase in the self-corrosion rate, and a sacrificial anode layer on the tube surface is prepared. Tends to be difficult.

Next, the fin material 4A will be described. The fin material 4A before brazing is composed of a core material 4a and a Si-containing layer 4b laminated only on one side of the core material 4a.
The core material 4a preferably contains Mn: 0.7 to 2% in mass% and is formed of an aluminum alloy composed of the balance unavoidable impurities and aluminum. Further, the core material 4a may be formed of an aluminum alloy containing Mn: 0.7 to 2% and Zn: 0.2 to 3% in mass%, and the balance is unavoidable impurities and aluminum. In the aluminum alloy, Fe: 0.2% or less, or Si: 0.15% or less is preferable.
Hereinafter, the content of each constituent element of the aluminum alloy constituting the core material 4a and the reasons for their limitation will be individually described.

<Mn: 0.7-2%>
Mn affects the strength of the aluminum alloy constituting the fin 3, and if it is less than 0.7%, the strength is lowered and the press formability is inferior. Prone to problems.
<Zn: 0.2 to 3%>
Zn affects the corrosion resistance (sacrificial anticorrosion effect) of the aluminum alloy constituting the fin 3. If the content is less than 0.2%, the sacrificial anticorrosion effect is insufficient, and if the content exceeds 3%, the self-corrosion rate deteriorates. There is a problem that the effect tends to be insufficient.

<Fe: 0.2% or less>
Fe has an effect on the self-corrosion resistance of the aluminum alloy constituting the fin 3, and if the content exceeds 0.2%, the self-corrosion rate deteriorates, and the sacrificial anticorrosion effect tends to be insufficient.
<Si: 0.15% or less>
Si affects the strength of the aluminum alloy constituting the fin 3, and if the content exceeds 0.15%, there is a problem in that it becomes difficult to obtain a potential difference from the core material.

Hereinafter, the content of each constituent element of the aluminum alloy constituting the Si-containing layer 4b and the reason for their limitation will be described.
The Si-containing layer 4b is preferably made of an aluminum alloy containing Si: 2 to 12% by mass and having a composition of the balance aluminum and unavoidable impurities. Further, in this aluminum alloy, Zn: 0.3% or less, or Sr: 0.01 to 0.1% may be contained.
<Si: 2-12%>
Si is contained as Si particles in the Si-containing layer 4b. The reason why Si is contained in the Si-containing layer 4b at 2 to 12% is that Si lowers the melting point of the Si-containing layer 4b, enhances the fluidity to be melted, and is the Si-containing layer melted at the heating temperature at the time of brazing. This is because Si is diffused in the thickness direction of the core material 4a to generate an inclination of the Si concentration in the thickness direction of the brazed fin 4. By generating the inclination of the Si concentration, the potential difference between the surface of the fin 4 on the side provided with the Si-containing layer 4b and the surface of the fin 4 on the side not provided with the Si-containing layer 4b can be generated by 10 mV or more.

<Zn: 0.3% or less>
The reason why the Zn content is set to 0.3% or less is that the potential difference from the Si-containing layer can be easily taken and the effect of planar corrosion can be obtained.
<Sr: 0.01-0.1%>
Sr has the effect of miniaturizing Si particles by adding it to the Si-containing layer 4b. Further, since Sr increases the amount of Si solid solution in the matrix, the potential can be increased. This makes it easy to provide a potential difference between the fin 4 and the tube 3.

In the fin material 4A, an aluminum alloy for the core material 4a and an aluminum alloy for the Si-containing layer 4b having the above composition are individually melted by a conventional method, and laminated through a hot rolling step, a cold rolling step, and the like. , It is obtained by cutting the laminated plate to the required width and then processing it into a corrugated shape. The method for producing the fin material 4A is not particularly limited in the present invention, and a known production method can be appropriately adopted.

"Header pipe"
The aluminum alloy constituting the header pipes 1 and 2 is preferably an aluminum alloy based on an Al—Mn system.
For example, it is preferable to contain Mn: 0.05 to 1.50%, and as other elements, Cu: 0.05 to 0.8% and Zr: 0.05 to 0.15% may be contained. can.

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 showing a state in which the header pipes 1, 2 and the tube 3 and the fin material 4A are assembled using the tube 3 in which the brazing coating film 7 is applied to the joint surface with the fin material 4A. It is a partially enlarged view of 101, and shows the state before 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. Further, a brazing material layer 13 is provided on the surface side of the core material 11 of the header pipes 1 and 2.

When the heat exchanger assembly 101 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 and the brazing coating film 7 are melted and then solidified. As shown in FIG. 2, the header pipe 1 and the tube 3, the tube 3 and the fin 4 are joined to each other, and the heat exchanger 100 having the structures shown in FIGS. 1 and 2 is obtained. From the Si-containing layer 4b, Si mainly diffuses to the core material 4a side at the time of brazing.

At the time of brazing, the brazing material layer 13 on the inner peripheral surface of the header pipes 1 and 2 melts and flows in the vicinity of the slit 6 to form the first fillet portion 8 and the header pipes 1 and 2 and the tube 3 are joined to each other. Will be done. Further, the brazing coating film 7 on the front and back surfaces of the tube 3 melts into Al-Si brazing or Al-Si-Zn brazing, which flows in the vicinity of the fin material 4A due to the capillary force to form the second fillet portion 9. The tube 3 and the fin 4 are joined together. Further, the brazing material layer 13 provided on the surfaces of the header pipes 1 and 2 slightly remains on the surface after brazing.

At the time of brazing, the brazing coating film 7 and the brazing material layer 13 are melted by heating at an appropriate temperature in an appropriate atmosphere such as an inert atmosphere. Then, the activity of the flux increases, and Zn in the flux diffuses to the front surface side or the lower surface side of the tube 3 and diffuses to their wall thicknesses, and in addition, the surfaces of both the brazing 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 higher, and maintained at the brazing temperature for a required time. , It suffices to cool from the brazing temperature to normal temperature.

On the upper surface side and the lower surface side of the tube 3, Zn in the flux is diffused by brazing to form a sacrificial anode layer 3E made of a Zn melt diffusion layer on the front surface side or the lower surface side of the tube 3, and on the surface side or the lower surface side of the tube. The region where Zn is diffused becomes lower than the inner side (region where Zn is not diffused) in the wall thickness direction of the tube 3. Here, the inner side of the tube 3 in the wall thickness direction indicates a region deeper in the wall thickness direction of the tube 3 than the front surface region or the back surface region of the tube 3 in which the sacrificial anode layer 3E is formed.
The Si contained in the Si-containing layer 4b is diffused to the core material 4a side by heating during brazing.

The amount of Zn contained in the second fillet portion 9 varies depending on the amount of Zn contained in the brazing coating film 7 and the amount of Zn contained in the tube 3, and the diffusion of Zn from the coating film 7 and the amount of Zn from the tube 3 It is affected by the diffusion of Zn. Since the fin 4 contains a large amount of Zn, the potential is lower than that of the tube 3. Further, Si and Zn are diffused from the Si-containing layer 4b into the core material 4a of the fin 4, and a concentration gradient of Si is formed in the core material 4a in the thickness direction thereof.
That is, a high concentration of Si is contained on the side where the Si-containing layer 4b was formed in the thickness direction of the core material 4a, and almost all on the side where the Si-containing layer 4b is not formed in the thickness direction of the core material 4a. Si is not diffused and has almost no Si, or Si originally contained in the core material 4a is present. As an example, as shown in FIG. 8 regarding the Si concentration gradient obtained in the examples described later, a Si diffusion layer having a Si concentration gradient in a region of about half the thickness of only one side in the thickness direction of the core material 4a. Is formed.

In the heat exchanger 100 having the above-described configuration, when used in a corrosive environment, corrosion progresses from a lesser part to a noble part.
In the heat exchanger 100 configured by brazing, if the tube 3 and fin 4 and the sacrificial anode layer 3E having the above composition are used, as an example, the surface potential of the core material 4a is -767 mV to -770 mV, and the tube. The surface potential of the sacrificial anode layer 3E on the surface of No. 3 can be set to -900 mV, and the surface potential on the short side surface side of the tube 3 can be set to a potential relationship of -710 mV to -740 mV.

In the structure of the present embodiment, the surface potential of the fin 4 obtained after brazing (the surface potential on the side where the Si-containing layer 4b is not provided in the thickness direction of the fin 4) and the surface potential on the short side surface side of the tube 3 are used. It is preferable to have a potential balance in which the difference between the two is 10 mV or more.
By having such a potential balance, the heat exchanger 100 having excellent corrosion resistance can be obtained. Specifically, in a corroded environment, the fins 4 become planarly corroded, so that the short side surface side of the tube 3 located near the fins 4 can be protected from corrosion.
If the difference between the surface potential of the fin 4 and the surface potential of the short side surface of the tube 3 is less than 10 mV, the effect of corroding the fin 3 in a planar manner is insufficient, which may lead to pitting corrosion on the short side surface of the tube 3. ..

Further, by making the brazed portion of the fin 4 the same as or slightly lower than that of the fin 4 by the above-mentioned structure, the sacrificial anode layer of the portion not covered by the fin 4 is enriched, and the corrosion resistance target is achieved at this portion. It is possible to suppress the opening of a through hole in the front. For example, the surface of the short side wall of the tube 3 can be protected from corrosion.
FIG. 6 shows the position of the fin 4 brazed on the upper surface side of the tube 3 on the side where the Si-containing layer 4b is provided, and FIG. 7 shows the fin 4 brazed on the lower surface side of the tube 3. The position on the side where the Si-containing layer 4b was provided is indicated by a chain line.
In the structure shown in FIG. 6, since the brazed coating film 7 is not formed on the short side surface 3D side of the tube 3 before brazing, the sacrificial anode layer 3E is not formed on the short side surface 3D side of the tube 3. Therefore, the potential on the short side surface side of the tube 3 is noble than the potential of the nearby fin 4.
Even in the structure shown in FIG. 7, since the sacrificial anode layer 3E is not formed on the short side surface 3D side of the tube 3, the potential on the short side surface 3D side of the tube 3 is higher than the potential of the nearby fins 4.
Therefore, in both the structure shown in FIG. 6 and the structure shown in FIG. 7, the fins 4 in the vicinity of the short side surface 3D side of the tube 3 can be subjected to planar corrosion, and the short side surface 3D side of the tube 3 is corroded. It is possible to provide a structure in which it is difficult to form a through hole. Therefore, it is possible to provide a heat exchanger 100 in which through holes are less likely to be formed in the tube 3 and refrigerant leakage is less likely to occur even if the tube 3 is used for a long period of time in a corrosive environment.

In the heat exchanger 100 having the configuration shown in FIG. 1, the Si-containing layer 4b is provided only on one side of the fin material 4A before brazing. When the fin material 4A is processed to a predetermined width by punching or cutting with a die, the structure provided on only one side of the fin material 4A is better than the structure provided with the Si-containing layers 4b on both sides of the fin material 4A. Mold wear can be suppressed.
The Si-containing layer 4b contains Si particles in a state before brazing, and the Si particles have high hardness. Therefore, assuming punching with a die, a structure in which the Si-containing layer 4b containing Si particles is formed on both sides of the fin material 4A is more likely to suppress wear of the die than a structure in which the Si-containing layer 4b is formed on only one side. Can be done.

By mass%, it contains Si: 0.35%, Fe 0.25%, Mn: 0.30%, Mg: 0.01%, Zn: 0.01%, Ti: 0.02%, and the balance is Al and From an aluminum alloy (referred to as a test material) made of unavoidable impurities, a thickness of 4 mm, an outer wall thickness of 0.5 mm, an inner column thickness of 0.5 mm, a hole width of 2 mm, a hole height of 3 mm, and a number of holes of 6 are extruded. A tube (flat tube) was manufactured.
A plurality of corrugated fins having a thickness of 0.13 mm and a width of 17 mm made of an aluminum alloy having the composition shown in Table 1 were prepared. Further, a Si-containing layer (aluminum alloy layer) having the composition shown in Table 1 was bonded to one side of the corrugated fin as a clad layer.

A mini-core test piece of a heat exchanger was prepared by assembling a corrugated fin with a Si-containing layer and a tube in six stages so as to be alternately overlapped on the upper and lower sides in the same manner as in the structures shown in FIGS. 1 and 3.

Each mini-core test piece was heated to 600 ° C. for 3 minutes in a heating furnace filled with 100% nitrogen, and then cooled by brazing to obtain a heat exchanger having a brazed structure.
The obtained heat exchanger was tested for potential measurement (2.67% AlCl ₃ aqueous solution) using a vs. caromel saturated electrode, corrosion resistance, through-hole generation time, mold wear, and brazing property.
"Fin material area reduction rate"
Evaluation was performed after the SWAAT test (40 days). The residual rate of the fin material area due to corrosion is evaluated by the projection area, and it can be judged that the residual rate of 90% or more after 40 days of the SWAAT test is acceptable.

"Days of through hole occurrence"
The number of days when a through hole was generated in the flat tube (flat tube made of the above-mentioned test material) was measured by the SWAAT test. If it is 200 days or more, it can be judged as passing.
"Mold wear resistance"
Since the right-angled part of the cutting die is worn and rounded after 100,000 shot cutting, the rounded shape of any part is measured with the surface roughness diameter and compared with the shape before 100,000 shots to obtain the worn area. .. A1200 (JIS) was measured as a comparative material, and when the wear amount of A1200 was 100 and the wear area of the test material) was 80 or more, it was judged that the mold wearability was good.
"Brazing"
Each brazed fin was peeled off from the tube, and the fin joint trace remaining on the tube surface was observed. Then, the number of unjoined parts (places where brazing was performed but no joint traces remained) was counted. 100 observations were made on one test piece, and those in which 90 or more (90% or more) were normally bonded were judged to have good brazing property.
"Press formability"
In corrugated fin molding, it was evaluated whether a predetermined fin pitch was obtained, and if it was within ± 3% of the set value, it was judged as ◯, and if it exceeded ± 3%, it was judged as ×.

The No. 1 sample in Table 1 is a sample in which the Si content of the Si-containing layer is low, but since the potential difference between the front and back surfaces of the fins cannot be 10 mV or more, the remaining fin area is small, the number of days until penetration is short, and corrosion resistance is achieved. I had a problem.
The sample No. 7 in Table 1 is a sample in which the Si content of the Si-containing layer is increased, but the mold wear is increased.

The sample No. 9 in Table 1 is a sample in which the Zn content of the Si-containing layer is increased, but since the potential difference between the front and back surfaces of the fins cannot be 10 mV or more, the remaining fin area is small, the number of days until penetration is short, and the corrosion resistance. Caused a problem.
The sample No. 9 in Table 1 is a sample in which the Sr content of the Si-containing layer is reduced, but since the potential difference between the front and back surfaces of the fins cannot be 10 mV or more, the remaining fin area is small, the number of days until penetration is short, and the corrosion resistance. Caused a problem.

The sample No. 16 in Table 1 was a sample in which the Sr content of the Si-containing layer was increased, but the number of days until penetration was short, which caused a problem in corrosion resistance.
The sample No. 17 in Table 1 was a sample in which the Mn content of the core material was reduced, but the strength was low and the press moldability was inferior.

The sample of No. 22 in Table 2 is a sample in which the Mn content of the core material is increased, but the strength is increased due to the excessive addition of Mn, and the result is that the press moldability is inferior.
The sample No. 23 in Table 2 is a sample in which the Zn content of the core material is low, but the potential difference between the front and back surfaces of the fins cannot be 10 mV or more, and the potential difference between the flat tube and the fins cannot be 10 mV or more. The area was small, the number of days to penetrate was short, and there was a problem with corrosion resistance.
The sample No. 31 in Table 2 is a sample in which the Zn content of the core material is increased, but the remaining fin area is small, the number of days until penetration is short, and there is a problem in corrosion resistance.
The sample No. 32 in Table 2 is an example in which Si-containing layers are formed on both sides. In this example, mold wear increased.

With respect to these samples, the samples of Nos. 2 to 6 shown in Tables 1 and 2 and the samples of Nos. 8, Nos. 11 to 15, 18 to 21, and 24 to 30 were placed on only one side of the core material. This is a heat exchanger in which a Si-containing layer containing an appropriate amount of Si, Zn, and Sr is provided, an appropriate amount of Mn is contained in the core material, and the potential difference between the front and back surfaces of the core material is adjusted to 10 mV or more after brazing. Therefore, it is possible to provide a heat exchanger having excellent brazing property of the brazed portion, excellent corrosion resistance, a long number of days to reach the through hole, and less mold wear at the time of forming the groove.

FIG. 8 shows the results of examining the concentration distributions of Si, Zn, and Mn in the thickness direction of the core material in the fin of the sample of No. 4 shown in Table 1.
Regarding the thickness direction of the core material of the No. 4 sample, a Si concentration gradient layer having a peak concentration of about 2.0%, a peak width of about 20 μm, and a Si distribution width of about 40 μm is formed on the side close to the Si-containing layer. I understand. Further, it can be seen that the Zn concentration contained in the core material of this sample is around 0.5% by mass, and the Mn content is around 1.5% by mass.

FIG. 9 shows the results of examining the concentration distributions of Si, Zn, and Mn in the thickness direction of the core material in the fin of the sample of No. 32 shown in Table 2.
Regarding the thickness direction of the core material of the sample of No. 32, Si is contained so as to show a peak concentration on both the side near the brazing material layer and the side away from the brazing material layer, and Zn contained in the core material. It can be seen that the concentration is around 0.5% by mass and the Mn content is around 1.5% by mass.
As is clear from these comparisons, when brazing filler metal layers are provided on both sides of the core material, Si is diffused from both brazing filler metal layers to the core material side, and peaks of Si concentration are generated on both the front and back surfaces of the core material. Therefore, it can be seen that a potential difference of 10 mV or more cannot be secured on the front and back surfaces of the core material.

100 ... heat exchanger, 3 ... tube (flat tube), 3A ... top surface, 3B ... bottom surface, 3C ... refrigerant passage, 3D ... short side surface, 3E ... sacrificial anode layer, 4 ... fins, 4A ... fin material, 4a ... core Material, 4b ... Si-containing layer, 7 ... Brazing coating, 8 ... First fillet part, 9 ... Second fillet part, 13 ... Wax material layer, 101 ... Heat exchanger assembly.

Claims (9)

A single-sided brazed fin material applied to heat exchangers with multiple fins brazed to the tube.
It has a Si concentration gradient layer only on one side in the thickness direction, has a high Si concentration on one side in the thickness direction, and has a region containing no Si or a Si content of 0.15% by mass or less on the opposite side. The fin is composed of a single-sided wax fin material having a potential difference of 10 mV or more on the front and back surfaces.
The tube is a flat tube having a short side surface, and the fins are brazed to the upper surface or the lower surface of the tube excluding the short side surface.
In the fin, the region containing no Si or having a Si content of 0.15% by mass or less further contains Mn: 0.7 to 2% and Zn 0.2 to 3% in mass %, and the balance aluminum and unavoidable impurities. It consists of an aluminum alloy with the composition of
One-sided heat exchanger wax provided in a heat exchanger in which the potential difference between the short side surface side of the tube and the base side of the fin is 10 mV or more, and the base side of the fin is baser than the short side surface side. Fin material. The tube is an aluminum alloy containing Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: less than 0.1% by mass, and the balance is unavoidable impurities and aluminum. The single-sided wax fin material for a heat exchanger according to claim 1, which comprises. The single-sided wax fin material for a heat exchanger according to claim 1 or 2, which has a sacrificial anode layer on the upper surface or the lower surface of the tube to which the fins are brazed. It has a plurality of fins and a tube to which these multiple fins are brazed.
It has a Si concentration gradient layer only on one side in the thickness direction, has a high Si concentration on one side in the thickness direction, and has a region containing no Si or a Si content of 0.15% by mass or less on the opposite side. The fin is composed of a single-sided wax fin material having a potential difference of 10 mV or more on the front and back surfaces.
The tube is a flat tube having a short side surface, and the fins are brazed to the upper surface or the lower surface excluding the short side surface.
The potential difference between the short side surface side of the tube and the base side of the fin is 10 mV or more, and the base side of the fin is baser than the short side surface side.
In the fin, the region containing no Si or having a Si content of 0.15% by mass or less further contains Mn: 0.7 to 2% and Zn 0.2 to 3% in mass %, and the balance aluminum and unavoidable impurities. A heat exchanger characterized by being made of an aluminum alloy having the composition of. The tube is an aluminum alloy containing Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: less than 0.1% by mass, and the balance is unavoidable impurities and aluminum. The heat exchanger according to claim 4, wherein the heat exchanger comprises. The heat exchanger according to claim 4 or 5, which has a sacrificial anode layer on the upper surface or the lower surface of the tube to which the fins are brazed. By mass%, Mn: 0.7 to 2%, Zn 0.2 to 3%, and Si: 2 to 12 by mass% only on one side of the core material made of an aluminum alloy having the composition of the balance aluminum and unavoidable impurities. Using a single-sided wax fin material for heat exchangers having a Si-containing layer containing%, Zn: 0.3% or less and Sr: 0.01 to 0.1%.
A method for manufacturing a heat exchanger in which a single-sided brazing fin material is brazed to an upper surface or a lower surface excluding the short side surface of a flat tube having a short side surface.
After brazing, a concentration gradient of Si having a high Si concentration on one side in the thickness direction of the single-sided brazing fin material and a low Si concentration on the opposite side is generated, and the potential difference between the front and back surfaces of the single-sided brazing fin material is 10 mV. A method for manufacturing a heat exchanger, which comprises producing the above. The tube is an aluminum alloy containing Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: less than 0.1% in mass%, and the balance is unavoidable impurities and aluminum. The method for manufacturing a heat exchanger according to claim 7, wherein a tube made of the same material is used. The method for manufacturing a heat exchanger according to claim 8, wherein a sacrificial anode layer is formed on the upper surface or the lower surface of the tube to which the fins are brazed.

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