JP2019210494A - Fin material for heat exchanger, and heat exchanger - Google Patents

Abstract

To provide a fin material for heat exchanger excellent in corrosion resistance of a fin, large in residual area of a fin even when used for long time, excellent in corrosion resistance of a flat tube, hardly forming open holes in the flat tube, and excellent in brazability, and a heat exchanger.SOLUTION: There are provided a brazing material having a core material and a Zn-containing layer formed on only a single side of the core material, a Mn centration gradient in which Zn concentration is high in a single side in a thickness direction thereof, and low in an opposite surface side after brazing, 30 mV or more potential lower in the high Zn concentration side than low Zn concentration side, and manufactured from a tube for heat exchanger, or a fin material for heat exchanger brazed by a brazing material which is added separately, in which the core material has a composition of Mn:0.5 to 2.0 mass%, Fe:1.0 mass% or less, Si:1.5 mass% or less, Zn:over 0.1 to 3.5 mass%, and the balance inevitable impurities and aluminum.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fin material for a heat exchanger and a heat exchanger.

For aluminum heat exchangers, aluminum flat tubes and corrugated fins are combined with a brazing type heat exchanger that is joined to the metal by brazing, and copper pipes and fins are combined, and then the copper pipes are expanded. An expansion type heat exchanger that mechanically joins tubes is known.
A brazing type heat exchanger is configured to braze and join a corrugated fin from above and below using a flat tube, whereas an expanded pipe type heat exchanger is a fin with a round hole. The structure which joins a fin and a copper pipe by inserting a copper pipe and expanding a copper pipe mechanically after insertion is adopted.

As a plate material for heat exchangers using corrugated fins, aluminum containing a specified amount of Si, Fe, Cu, Mn, Mg and further containing a specified amount of one or more of Cr, Zr, Hf, Ti, B A brazing sheet is known in which a brazing material containing a specified amount or more of Si is clad on one or both surfaces of a core material made of an alloy (see Patent Document 1).
This brazing sheet is characterized by excellent strength after brazing and heating, brazing properties and repeated bendability, as well as pitting corrosion resistance.

Moreover, in the heat exchanger using a corrugated fin, the corrugated fin is composed of an aluminum alloy brazing sheet, and one or more of Mn, Si, Fe, Zn contained in the core material of the brazing sheet There is known a heat exchanger in which the content is defined and the amounts of Si and Zn contained in the brazing material layer are defined (see Patent Document 2).
In this heat exchanger, when a brazing sheet is brazed, a part of Si remains on the surface of the brazing material, and if there is condensed water or the like, 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 brazing material layer and the brazing material layer, and the problem that the corrosion wear amount of the fins is increased is improved.

Japanese Patent Laid-Open No. 02-050934 JP 2014-084521 A

In a flat tube applied to a brazing type heat exchanger, a sacrificial anticorrosion layer such as a zinc sprayed layer is provided on both the upper and lower surfaces of the flat tube in order to suppress the leakage of the refrigerant due to the corrosion holes.
In addition, fins often play a role in maintaining heat exchange performance and sacrificial corrosion prevention of tubes in heat exchangers. However, fins are subject to excessive corrosion and are quickly removed from the heat exchanger to maintain heat exchange performance. As a result, the sacrificial anticorrosive effect on the tube is impaired.
In order to maintain the performance of the heat exchanger for a long period of time, it is necessary to prevent the fins from falling off prematurely due to corrosion and to maintain the sacrificial anticorrosive effect of the tubes by the fins for a long period.

  In view of these backgrounds, the present invention is excellent in the corrosion resistance of the fins, does not cause the fins to fall off even when used for a long period of time, and has excellent heat resistance that allows the tubes brazed to the fins to have excellent corrosion resistance. It aims at providing the fin material for exchangers, and a heat exchanger.

The fin material for a heat exchanger of the present invention has a core material and a Zn-containing layer formed only on one side of the core material. After brazing, the Zn concentration is high on one side in the thickness direction, and the opposite surface side. A Zn concentration gradient is generated at a low Zn concentration, and a potential lower than the core material is generated by 30 mV or more on the high Zn concentration side, and the brazing material provided from the heat exchanger tube or a brazing material added separately. The heat exchanger fin material is attached, and the core material is Mn: 0.5 to 2.0% by mass, Fe: 1.0% by mass or less, Si: 1.5% by mass or less, Zn: 0.00%. It consists of an aluminum alloy having a composition of more than 1 to 3.5% by mass, the balance inevitable impurities and aluminum.
In the fin material for a heat exchanger of the present invention, it is preferable that 0.5 to 5.0% by mass of Zn is present on the surface of the core material on the Zn-containing layer side after brazing.

  In the heat exchanger according to the present invention, a Zn concentration gradient is generated on one side of the core in the thickness direction with a high Zn concentration and on the opposite side with a low Zn concentration, and the potential on the high Zn concentration side is on the low Zn concentration side. The heat exchanger fin material whose potential is 30 mV or more lower than the electric potential is Si: 0.05 to 1.0 mass%, Mn: by the brazing material brought from the heat exchanger tube or the brazing material added separately. 0.1 to 1.5% by mass, Cu: a heat exchanger brazed to a heat exchanger tube in which the remainder regulated to 0.05% by mass or less is Al and inevitable impurities, and the core material is Mn: 0.5 to 2.0% by mass, Fe: 1.0% by mass or less, Si: 1.5% by mass or less, Zn: more than 0.1 to 3.5% by mass, the balance of inevitable impurities and aluminum It consists of the aluminum alloy which has this.

  In the heat exchanger according to the present invention, it is preferable that 0.5 to 5.0% by mass of Zn is present on the surface of the core material on the high Zn concentration side.

If it is the fin material for heat exchangers of the present invention, it has a Zn-containing layer only on one side of the core material, and after brazing, the Zn concentration is high on one side in the thickness direction, and the Zn concentration is on the opposite side. A low Zn concentration gradient can be generated, and a potential difference between the front and back surfaces of 30 mV or more can be generated. For this reason, a fin material can be made into a potential base with respect to the electric potential of the tube for heat exchangers brazed to a fin material, and a fin material can be made into surface corrosion. For this reason, the tube brazed to the fin material can be sacrificial and anticorrosive, and the corrosion of the tube is difficult to proceed. Therefore, it is possible to provide a structure in which a through hole is not easily generated in the tube even when used for a long time. Therefore, by using the fin material according to the present invention, it is possible to provide a heat exchanger that hardly causes a refrigerant leak from the tube.
In addition, the core material of the fin can be grounded to have surface 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 be removed. It is possible to provide a heat exchanger that hardly occurs.

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 partial expanded sectional view which shows the state which assembled and brazed the header pipe, the tube, and the fin material in the same heat exchanger. It is a partial expanded sectional view which shows the state which assembled the header pipe, the tube, and the fin material before brazing in the same heat exchanger. In the same heat exchanger, it is the elements on larger scale which show the tube and fin material which were 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 diagram showing a part of the fin installed on the tube after brazing. In the same heat exchanger, it is a simplified diagram showing a part of the fin installed under the tube after brazing.

Hereinafter, the present invention will be described in detail based on a 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. This heat exchanger 100 includes header pipes 1 and 2 that are spaced apart from each other in parallel on the left and right sides, parallel to each other with a space between the header pipes 1 and 2, and to the header pipes 1 and 2. A plurality of flat tubes (flat tubes) 3 joined at right angles to each other and corrugated fins (corrugated fins) 4 brazed to the tubes 3 are mainly used. The header pipes 1 and 2, the tubes 3 and the fins 4 are made of an aluminum alloy which will be described later.

More specifically, a plurality of slits 6 are formed at regular intervals in the length direction of each pipe, as shown in FIG. 2 and FIG. The tube 3 is installed between the header pipes 1 and 2 by inserting the end portions of the tube 3 into the slits 6 facing each other. Further, fins 4 are arranged between a plurality of tubes 3, 3 laid between the header pipes 1, 2 at a predetermined interval, and these fins 4 are brazed to the front side or back side of the tubes 3.
That is, as shown in FIG. 2, a first fillet portion 8 is formed of a brazing material at a portion where the end portion of the tube 3 is inserted into the slit 6 of the header pipes 1 and 2, and 3 is brazed. Further, in the corrugated fins 4, the second fillet portion 9 is formed by the brazing material generated at the portion between the top and bottom surfaces of the adjacent tubes 3 with the top portions of the waves facing each other. Corrugated fins 4 are brazed to the side and back side.

  The heat exchanger 100 of the present embodiment is assembled with the header pipes 1 and 2 and a plurality of tubes 3 and a plurality of fin members 4A installed between them as described in detail in the manufacturing method described later. As shown in FIG. 1, the heat exchanger assembly 101 is formed, and this is manufactured by heating and 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 side and the back side of the tube 3 by heating during brazing. The fin material 4A becomes the fin 4 by brazing.

As shown in FIGS. 3 and 4, the tube 3 before brazing is provided with Si powder: 1 to 5 g / m ² , Zn-containing flux (KZnF ₃ ) on the front side and the back side where the fin material 4A is brought into contact. : 3.0~20g / ^{m 2,} a binder (e.g., acrylic resin): 0.5~8.5g / ^{m 2} for brazing coating 7 made of is applied. Further, the fin material 4A before brazing has a Zn-containing layer 4b formed only on one side of the core material 4a. In the form shown in FIG. 3, the Zn-containing layer 4 b is disposed on the upper end outer surface side of the fin material 4 </ b> A assembled below the tube 3, and the Zn-containing layer is contained on the lower end inner surface side of the fin material 4 </ b> A assembled above the tube 3. Layer 4b is disposed. For this reason, the fin material 4A on the upper surface side of the tube 3 is disposed so that the core material 4a on the lower end side thereof is in contact with the coating film 7 for brazing, and the fin material 4A on the lower surface side of the tube 3 contains Zn on the upper end side. It arrange | positions so that the layer 4b may contact the coating film 7 for brazing.

  As shown in FIG. 5, the tube 3 of the present embodiment has a flat tube shape whose height (thickness) is small with respect to the width, and a plurality of refrigerant passages 3 </ b> C are formed therein and a flat surface ( The flat multi-hole tube includes 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 3 </ b> C adjacent to the left and right are partitioned by a partition wall 3 </ b> F. In this 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 which comprises the coating film 7 for brazing is demonstrated.
<Si powder>
The Si powder reacts with Al constituting the tube 3 to form a braze that joins the fins 4 and the tube 3, but the Si powder melts into a brazing liquid during brazing. Zn in the flux diffuses into the brazing solution and spreads uniformly on the surface of the tube 3. Since the diffusion rate of Zn in the liquid brazing liquid is remarkably higher than the diffusion rate in the solid phase, the Zn concentration on the surface of the tube 3 becomes substantially uniform, whereby a uniform Zn melt diffusion layer (sacrificial anode layer) 3E. Thus, the corrosion resistance of the tube 3 can be improved.

“Si powder coating amount: 1 to 5 g / m ² ”
Brazing property will fall that the application quantity of Si powder is less than 1 g / m < ² >. On the other hand, when the coating amount of Si powder exceeds 5 g / m ² , Zn is easily concentrated in the fillet due to excessive brazing, unreacted Si residue is generated, and the corrosion depth of the tube is increased. The intended effect of preventing separation cannot be obtained. For this reason, content of Si powder in a coating film shall be 1-5 g / m < ² >. Preferably, the content of 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 . As an example, the particle size of the Si powder used here is 15 μm or less in D (99). D (99) is the diameter at which the volume-based cumulative particle size distribution from the small-diameter side becomes 99%.

<Zn-containing flux, non-Zn-containing flux>
The Zn-containing flux has an effect of forming a sacrificial anode layer 3E on the surface of the tube 3 during brazing and improving pitting corrosion resistance. Moreover, it has the effect | action which removes the oxide of the surface of the tube 3 at the time of brazing, and promotes the spreading | diffusion and the wetting of a brazing, and improves brazing property. Since this Zn-containing flux has a higher activity than a flux not containing Zn, good brazing properties can be obtained even when a relatively fine Si powder is used.
Non-Zn-containing fluxes include K ₃ AlF ₆ + KAlF ₄ and fluorides 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, a flux mainly composed of potassium aluminum tetrafluoride, and various compositions including additives. Examples of the known composition include 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 is added can also be used.
Use of a Zn-containing flux or addition of these non-Zn-containing fluxes in addition to the Zn-containing flux contributes to improvement of brazing properties.

“Zn-containing flux application amount: 3.0 to 20 g / m ² ”
When 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 decreases, and fin separation is accelerated. For this reason, the application quantity of Zn containing flux shall be 3.0-20 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, _KF, may be used mixed flux mixed with a flux containing no Zn such as K 2 SiF _6. The coating amount may be such that the Zn-containing flux is in the range of 3.0 to 20 g / m ² .
In addition, in order to display a numerical range in this specification, when an upper limit value and a lower limit value are continuously described using “to”, the upper limit value and the lower limit value are included unless otherwise specified. Therefore, 3.0~20g / ^{m 2} refers to 3.0 g / ^{m 2} or more 20 g / ^{m 2} or less.

“Non-Zn content flux application amount: 1-10 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 brazing fluidity is excessive. As a result of this improvement, more than expected Zn is concentrated in the fillet, which leads to fin peeling.

<Binder>
The coating film 7 for brazing contains a binder in addition to Si powder, Zn-containing flux, and non-Zn-containing flux. Further, the non-Zn-containing flux may be omitted. An example of the binder is preferably an acrylic resin.
“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 coating film hardness decreases, and the workability (coating film resistance) decreases. On the other hand, when the coating amount of the binder exceeds 8.3 g / m ² , the brazing property is deteriorated due to the effect of the fillet not being formed due to the unreacted film. For this reason, it is preferable that the application quantity of a binder shall be 0.2-8.3 g / m < ² >. The binder usually evaporates by heating during brazing.

  The coating method of the Si powder, the Zn powder, the Zn-containing flux and the binder, or the brazing composition in which the non-Zn-containing flux is added thereto is not particularly limited in the present invention, and the spray method, the shower method, the flow coater. It can be performed by an appropriate method such as a method, a roll coater method, a brush coating method, a dipping method, or an electrostatic coating method. The brazing composition may be applied to the entire surface of the tube 3 or may be the partial surface or the back surface of the tube 3. In short, at least the fins 4 are brazed. What is necessary is just to apply | coat to the surface area | region or back surface area | region of the tube 3 required for this. In order to apply the brazing composition to the tube 3, the viscosity is adjusted by appropriately adding a solvent such as 3-methoxy-3-methyl-1-butanol or isopropyl alcohol to the brazing composition, It is preferable to enable application by the above-described application method.

The tube 3 contains, by mass%, Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Cu: 1.0% or less, and an aluminum alloy composed of the balance unavoidable impurities and aluminum. Etc. The tube 3 is produced by extruding these aluminum alloys.
Hereinafter, the reasons for limiting the constituent elements of the aluminum alloy constituting the tube 3 will be described.

<Si: 0.05-1.0%>
Si, like Mn, is an element having an effect of improving the strength.
If the Si content is less than 0.05%, the effect of improving the strength is insufficient. On the other hand, when Si is contained exceeding 1.0%, the extrudability is lowered. Accordingly, 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 improves the mechanical strength. Mn also has the effect of improving extrudability during extrusion molding. Furthermore, Mn has the effect of suppressing the flowability of the wax and reducing the Zn concentration difference between the fillet and the tube surface.
If the Mn content is less than 0.1%, the effect of improving the corrosion resistance and strength is insufficient, and the effect of suppressing the fluidity of the wax is also lowered. On the other hand, when Mn is contained exceeding 1.5%, the extrudability decreases due to an increase in extrusion pressure. Therefore, the Mn content in the present invention is preferably 0.1 to 1.5%.

<Cu: 1.0% or less>
Cu is an element that affects the corrosion resistance of the tube 3. If it is less than 1.0%, there is no problem, but if it exceeds 1.0%, the corrosion resistance decreases due to an increase in self-corrosion rate, and the sacrificial anode layer on the tube surface Production tends to be difficult.

Next, the fin material 4A will be described. The fin material 4A before brazing includes a core material 4a and a Zn-containing layer 4b laminated only on one side of the core material 4a.
The core material 4a is preferably formed of an aluminum alloy containing, in mass%, Mn: 0.5 to 2.0%, and the balance of inevitable impurities and aluminum. Further, the core material 4a is formed of an aluminum alloy containing, in mass%, Mn: 0.5 to 2.0%, Zn: more than 0.1 to 3.5 mass%, and the balance unavoidable impurities and aluminum. May be. In the aluminum alloy, it is preferable that Fe: 1.0% or less, or Si: 1.5% or less.
Hereinafter, each constituent element content of the aluminum alloy constituting the core material 4a and the reasons for limitation thereof will be described individually.

<Mn: 0.5 to 2.0%>
Mn has an effect on the corrosion resistance and strength of the aluminum alloy constituting the core material 4a. If it is less than 0.5%, it is inferior in press formability due to strength reduction, and if it exceeds 2.0%, the strength is high and press formability is poor. Inferior and prone to problems with productivity.
<Zn: more than 0.1 to 3.5% by mass>
Zn has an effect on the corrosion resistance (sacrificial anticorrosive effect) of the aluminum alloy constituting the core material 4a. If it is 0.1% or less, the sacrificial anticorrosive effect is insufficient. If the content exceeds 3.5%, the self-corrosion rate is deteriorated. There is a problem that the sacrificial anticorrosive effect tends to be insufficient.

<Fe: 1.0% or less>
Fe has an influence on the self-corrosion resistance of the aluminum alloy constituting the core 4a. If the content exceeds 1.0%, the sacrificial anticorrosion effect tends to be insufficient due to the deterioration of the self-corrosion rate.
<Si: 1.5% or less>
Si has an influence on the strength of the aluminum alloy constituting the core material 4a. If the content exceeds 1.5%, there is a problem in that the workability deteriorates due to excessively high strength.

<Zn-containing layer>
Hereinafter, the contents of each constituent element of the aluminum alloy constituting the Zn-containing layer 4b and the reasons for limitation thereof will be described.
The Zn-containing layer 4b is preferably made of an aluminum alloy containing Zn: 0.5 to 5.0% by mass.
As an aluminum alloy constituting the Zn-containing layer 4b, an alloy in which Zn in the above range is contained in a JIS 1000 series aluminum alloy, an alloy in which Zn in the above range is contained in a JIS 3000 series aluminum alloy, or other contained components An Al—Zn alloy containing inevitable impurities can be used. The aluminum alloy constituting the Zn-containing layer 4b is not limited to the type described above as long as it is an aluminum alloy containing Zn in the above-described range, and may be any other composition, and can be laminated on the core material 4a. As long as it is an aluminum alloy that can be formed, an aluminum alloy having any composition may be used.

  The fin material 4A is prepared by individually melting an aluminum alloy for the core material 4a having the above composition and an aluminum alloy for the Zn-containing layer 4b by a conventional method, and laminating them through a hot rolling process, a cold rolling process, and the like. The laminate is obtained by cutting the laminated plate into a required width and then processing it into a corrugated shape. In addition, the manufacturing method of 4 A of fin materials is not specifically limited as this invention, A well-known manufacturing method can be employ | adopted suitably.

"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%, Zr: 0.05 to 0.15% may be contained. it can.

Next, the manufacturing method of the heat exchanger 100 which uses the header pipe 1, 2 tube 3, and the fin 4 demonstrated above as main components is demonstrated.
FIG. 3 shows a state in which the header pipes 1 and 2, the tube 3, and the fin material 4 </ b> A are assembled using the tube 3 in which the coating film 7 for brazing is applied to the joint surface with the fin material 4 </ b> A. It is the elements on larger scale of 101, Comprising: The state before brazing is shown.
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. A brazing filler metal layer 13 is provided on the surface side of the core 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 in a heating furnace and cooled after heating, the brazing material layer 13 and the brazing coating film 7 are melted. As shown in FIG. 2, the header pipe 1 and the tube 3, and the tube 3 and the fin 4 are joined together to obtain the heat exchanger 100 having the structure shown in FIGS. 1 and 2. In the fin material 4A, Zn diffuses mainly from the Zn-containing layer 4b to the core material 4a side by heating during brazing.

  During brazing, the brazing filler metal 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 so that the header pipes 1 and 2 and the tube 3 are joined. Is done. Also, the brazing coating 7 on the front and back surfaces of the tube 3 melts to become Al—Si brazing or Al—Si—Zn brazing, and flows near the fin material 4A by capillary force to form the second fillet portion 9. Thus, the tube 3 and the fin 4 are joined. 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 to an appropriate temperature in an appropriate atmosphere such as an inert atmosphere. Then, the activity of the flux is increased, and Zn in the flux diffuses to the surface side or the lower surface side of the tube 3 and diffuses in the thickness direction of the tube 3, and the surfaces of both the brazing material and the brazing material This promotes the wetting between the brazing material and the brazing material by destroying the oxide film.
The conditions for brazing are not particularly limited. As an example, the inside of the furnace is set to a nitrogen atmosphere, and the heat exchanger assembly 101 is heated to a brazing temperature (substance attainment temperature) of 580 to 620 ° C. at a heating rate of 5 ° C./min or more, and held at the brazing temperature for a necessary time. Cooling from the brazing temperature to room temperature.

  Zn in the flux is diffused by brazing on the upper surface side and the lower surface side of the tube 3 to form a sacrificial anode layer 3E made of a Zn fusion diffusion layer on the surface side or lower surface side of the tube 3, and on the tube surface side or lower surface side. The region that has undergone Zn diffusion is lower than the inner side of the tube 3 in the thickness direction (the region that has not undergone Zn diffusion). Here, the inner side in the thickness direction of the tube 3 indicates a region deeper in the thickness direction of the tube 3 than the surface region or the back surface region of the tube 3 where the sacrificial anode layer 3E is formed.

The amount of Zn contained in the second fillet portion 9 varies depending on the amount of Zn contained in the brazing coating 7 and the amount of Zn contained in the core material 4a of the fin 4 or the Zn-containing layer 4b. The Zn diffusion from the fin 4 and the Zn diffusion from the fin 4 are affected. Since the fin 4 or the Zn-containing layer 4 b contains a large amount of Zn, the potential of the second fillet portion 9 is lower than that of the tube 3. Further, Zn is diffused from the Zn-containing layer 4b into the core material 4a of the fin 4, and a Zn concentration gradient is formed in the core material 4a in the thickness direction.
That is, in the thickness direction of the core material 4a of the fin 4, Zn having a high concentration is contained on the side where the Zn-containing layer 4b has been formed, so that a high Zn-containing region (high Zn concentration side) is formed. In the vertical direction, Zn is hardly diffused on the side where the Zn-containing layer 4b is not formed, and there is almost no Zn, or a low Zn-containing region where Zn originally contained in the core material 4a is present (low Zn concentration side).

In the heat exchanger 100 having the above-described configuration, when it is used in a corrosive environment, the corrosion progresses from a lower part to a noble part.
In the heat exchanger 100 configured by brazing, if the tube 3 and the fin 4 have the above composition, as an example, the potential difference between the potential on the high Zn concentration side and the potential on the low Zn concentration side in the fin 4 is as follows. , 30 mV or more is generated.
For example, in the case of the fin 4 having the above composition, if the potential in the low Zn concentration region is −740 to −920 mV (vs SCE), the potential in the high Zn concentration region is −770 to −950 mV (vs SCE). The potential difference between the potential on the high Zn concentration side and the potential on the low Zn concentration side is about 30 to 210 mV.
Further, in the case of the tube 3 having the above-described composition, the potential is −700 to −730 mV (vs SCE), the potential difference from the low Zn concentration region of the fin 3 is about 30 to 210 mV, and the high Zn concentration region of the fin 3 Is generated about 60 to 250 mV.

By having the potential balance as described above, the heat exchanger 100 having excellent corrosion resistance can be obtained.
In a normal heat exchanger, in order to fulfill sacrificial protection of the tube, the potential of the fin itself is made lower than that of the tube. However, even if the potential relationship is adjusted, if the corrosion generated in the fin is a corrosion form that causes pitting corrosion in the cross-sectional direction of the fin indefinitely, the strength of the fin decreases early and the fin falls off. May result in
In contrast, if the potential difference between the high Zn concentration side potential and the low Zn concentration side potential of the fin 4 is 30 mV or more as described above, the effect that the fin 4 performs sacrificial corrosion protection of the tube 3 is maintained. By controlling the corrosion form of the fin 4 itself, it becomes a structure which can prevent the early separation of the fin 4.
That is, rather than causing corrosion to occur in the cross-sectional direction of the fin 4 indefinitely and laterally, the high Zn concentration side can be made into surface corrosion, and at the same time, the high Zn concentration side can sacrificially prevent the low Zn concentration side. In addition, even if pitting corrosion is about to occur on the low Zn concentration side, corrosion is pulled on the high Zn concentration side, and as a result, the corrosion form in which pitting corrosion occurs in the crosswise direction of the fin 4 can be suppressed.
Specifically, in a corrosive environment, surface corrosion is likely to occur on the high Zn concentration side, but it is not a corrosive form in which pitting corrosion occurs in the vertical and horizontal directions in the cross-sectional direction of the fin 4.

  Further, by using Zn so as to form a Zn concentration gradient by forming a high Zn concentration side in the fin 4, the potential on one side of the fin 4 is lowered to a potential lower than that of a fin that exhibits a normal sacrificial anode effect. Since the electric potential can be adjusted, the electric potential difference between the tube 3 and the fin 4 can be made larger than before. Thereby, the sacrificial anode effect with respect to the tube 3 can be enlarged conventionally.

Moreover, since the fin 4 becomes surface corrosion, the drop-off of the fin 4 can be suppressed for a long period of time, and the short side surface side of the tube 3 located near the fin 4 can be prevented from being corroded.
By making the brazed portion of the fin 4 the same as or slightly lower than that of the fin 4 by the above-described structure, the sacrificial anode layer not covered by the fin 4 is enriched, and before this corrosion resistance target The presence of through holes can be suppressed. For example, the surface of the short side wall of the tube 3 can be anticorrosive.

6 shows the position of the fin 4 brazed to the upper surface side of the tube 3 on the side where the Zn-containing layer 4b was provided by a chain line, and FIG. 7 shows the fin 4 brazed to the lower surface side of the tube 3. The position on the side where the Zn-containing layer 4b was provided is indicated by a chain line.
In the structure of FIG. 6, the brazing coating film 7 is not formed on the short side surface 3D side of the tube 3 before brazing, and therefore the sacrificial anode layer 3E is not formed on the short side surface 3D side of the tube 3. For this reason, the potential on the short side surface of the tube 3 is nobler than the potential of the nearby fin 4.
Also 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 becomes higher than the potential of the nearby fins 4.

Therefore, in either of the structure shown in FIG. 6 or the structure shown in FIG. 7, sacrificial corrosion protection can be performed with the fin 4 in the vicinity of the short side surface 3D side of the tube 3. It is possible to provide a structure that is difficult to generate. That is, sacrificial corrosion prevention can be performed on the short side surface 3D side by the fins 4 due to the potential difference.
For this reason, even if it uses for a long period of time in a corrosive environment, it is hard to produce a through-hole in the tube 3, and it is possible to provide the heat exchanger 100 in which refrigerant leakage from the tube 3 hardly occurs.

In the embodiment described above, the brazing coating film 7 having the above-described composition is used for brazing the tube 3 and the fin 4, but the means for brazing is limited to the brazing coating film 7. A brazing sheet or a brazing braze for brazing may be used instead.
In the case of a brazing sheet, for example, a configuration in which an Al—Si alloy layer represented by JIS 4343 alloy or 4045 alloy is bonded to a thickness of 3 to 15 μm can be used. An alloy powder adjusted with 4045 alloy and a flux may be mixed and used as a liquid with a viscous liquid.

A tube (flat tube: width 18 mm, height 1.3 mm, number of holes 19) was manufactured from an aluminum alloy having each composition shown in Table 1 by extrusion.
A plurality of corrugated fins having a thickness of 0.13 mm and a width of 18 mm were formed from an aluminum alloy plate having each composition shown in Table 1 by punching and forming using a mold. Further, a Zn-containing layer having the composition shown in Table 1 (an aluminum alloy layer containing Zn corresponding to the Zn concentration on the high Zn concentration side shown in Table 1) was bonded to one side of the corrugated fin as a cladding layer.

A corrugated fin with a Zn-containing layer and six tubes were used and assembled so as to overlap each other in the same manner as in the structures shown in FIGS. 1 and 3 to produce a mini-core test body of a heat exchanger.
On the upper and lower surfaces of the tube, Si powder (particle diameter D (99): 15 μm or less): 3.0 g / m ² , Zn-containing flux (KZnF ₃ ): 6.0 g / m ² , acrylic resin binder: 2 A coating film for brazing of 0.0 g / m ² was applied.

Each mini-core specimen was heated at 600 ° C. for 3 minutes in a heating furnace filled with 100% nitrogen, and then subjected to brazing treatment for cooling to obtain a heat exchanger having a brazed structure.
Each of the obtained heat exchangers was subjected to potential measurement (2.67% AlCl ₃ aqueous solution) with a vs calomel saturated electrode, tested for corrosion resistance (corrosion form of fins, resistance to fin peeling), fin strength measurement, fins Evaluation of processability, measurement of tube strength, and evaluation of extrudability were performed.
The results are summarized in Tables 1 and 2 below. Details of each test as well as measurement and evaluation will be described later.

In each sample shown in Table 1, the coating film for brazing forms a fillet by brazing during brazing, and Zn diffuses from the coating film on the front and back surfaces of the tube and is sacrificed as shown in FIG. An anode layer is produced.
The tube potential (vs SCE) shown in Table 1 is a potential in a region where the sacrificial anode layer is not generated. The Zn low concentration side in the column described as the potential difference with the fin in the tube is the potential difference between the region where the sacrificial anode layer is not generated in the tube and the Zn low concentration region of the fin, and the Zn high concentration side is the tube 2 is a potential difference between a region where the sacrificial anode layer is not formed and a Zn high concentration region of the fin.

"Fin workability"
Fin workability was evaluated by die wear when processing fins. A plate material (thickness 0.13 mm) made of JIS standard 3403 alloy and JIS standard 3009 alloy was compared with the case of punching with a die. When punching the fins of the above examples, if the workability is equal to or better than that of 3403 alloy, it is judged as ◎. It was judged as Δ, and when it was less than 3009 alloy, it was judged as ×. As evaluation of workability, it can be judged that ◎ is very good, ○ is good, Δ is slightly good, and × is bad.
"Fin peeling resistance"
For each of the mini-core specimens, the peel strength after the SWAAT test (40 days) was evaluated by “(SWAAT 40 days / before SWAAT) × 100” as compared with the peel strength before the SWAAT test.
Regarding the contrasted values, it was judged that 100 to 75% of the samples were ◎, 74 to 50% of the samples were ○, 49 to 25% of the samples were Δ, and 14 to 0% of the samples were ×.

"Extrudability"
When extruding a tube from an aluminum alloy having each composition shown in Table 1, the extrusion pressure, the extrusion speed, and the tube surface state were comprehensively observed and evaluated. Samples that cannot be extruded because the extrusion pressure is too high, and samples that have a large number of surface defects such as pickups are evaluated as x in the extrudability, almost no surface defects are found, the value of extrusion pressure, the value of extrusion speed (target) The lower the extrusion pressure with respect to the extrusion speed, the better the extrudability. Specifically, the extrusion pressure and the extrusion speed when using JIS stipulated aluminum alloys, 3102, and 3003 are compared. If the extrusion pressure is equal to or less than that of the 3102 alloy, it is judged as ◎, and the extrusion pressure is 3102. If it was larger than the alloy but smaller than 3003 alloy, it was judged as “good”. If the extrusion pressure was equivalent to 3003 alloy, it was judged as Δ.
As evaluation of extrudability, it can be judged that ◎ is very good, ○ is good, Δ is slightly good, and × is bad.

“Tube strength”
The tube strength is a result obtained by a tensile test on a flat tube having a width of 18 mm, a height of 1.3 mm, and a number of holes of 19 after brazing heat treatment.
"Tube maximum corrosion depth"
The maximum corrosion depth of the tube was evaluated according to the following criteria according to the value of the maximum corrosion depth (μm) generated in the corrosion test (SWAAT 40 days) on the tube joined to the fin by brazing heat treatment.
A: Maximum corrosion depth 0 to 40 μm, ○: Maximum corrosion depth 41 to 80 μm, Δ: Maximum corrosion depth 81 to 120 μm, ×: Maximum corrosion depth 121 μm to penetration.

Samples of Examples 1 to 17 shown in Tables 1 and 2 are Mn: 0.5 to 2.0% by mass, Fe: 1.0% by mass or less, Si: 1.5% by mass or less, Zn: The fin core material is composed of an aluminum alloy having a composition of more than 0.1 to 3.5% by mass, the balance unavoidable impurities and aluminum, and after brazing, the potential difference between the high Zn concentration side and the low Zn concentration side is 30 mV. This is the sample that has been generated.
As shown in the results shown in Table 2, the samples of Examples 1 to 17 have high fin strength, excellent fin workability, and the fin corrosion form is surface corrosion, and the fin peeling resistance is high. The tube strength is high and the extrudability of the tube is also excellent.
That is, if it is a heat exchanger of Example 1- Example 17, it is excellent in the corrosion resistance of a fin, and even if it uses for a long period of time, it does not drop out to a fin, and is excellent in the corrosion resistance of the tube brazed to a fin. Heat exchanger can be provided.
Moreover, if it is a fin used in Example 1- Example 17, when manufacturing a heat exchanger by brazing to a tube, fin strength is high, it is excellent in fin workability, and the corrosion form of a fin is planar. It can be seen that fins having corrosion resistance and high fin peel resistance can be obtained.

The sample of Comparative Example 1 is a sample in which the potential difference between the potential on the low Zn concentration side of the fin and the potential of the tube is 20 mV, but in terms of fin strength, fin corrosion form, fin peel resistance, tube strength, and extrudability. There was no problem, but the maximum corrosion depth of the tube was increased.
In the sample of Comparative Example 2, since the potential difference between the low Zn concentration side and the high Zn concentration side of the fin was 20 mV, which is small, the corrosion form of the fin was pitting corrosion, resulting in poor fin peel resistance.

Since the sample of Comparative Example 3 had a low Si content in the aluminum alloy constituting the tube, the tube strength was insufficient.
Since the sample of Comparative Example 4 had a high Si content in the aluminum alloy constituting the tube, the tube strength was too high, causing a problem in extrudability.

Since the sample of Comparative Example 5 had a low Mn content in the aluminum alloy constituting the tube, the tube strength was insufficient.
Since the sample of Comparative Example 6 had a high Mn content in the aluminum alloy constituting the tube, the tube strength was too high, causing a problem in extrudability.

Since the sample of Comparative Example 7 had a low Mn content in the aluminum alloy constituting the fin, the result was inferior in the fin peel resistance.
Since the sample of Comparative Example 8 had a high Mn content in the aluminum alloy constituting the fin, the fin strength was too high, causing a problem in fin workability.
Since the sample of Comparative Example 9 had a high Si content in the aluminum alloy constituting the fin, the fin strength was too high, causing a problem in fin workability.

  DESCRIPTION OF SYMBOLS 100 ... Heat exchanger, 3 ... Tube (flat tube), 3A ... Upper surface, 3B ... Lower surface, 3C ... Refrigerant passage, 3D ... Short side surface, 3E ... Sacrificial anode layer, 4 ... Fin, 4A ... Fin material, 4a ... Core Material: 4b: Zn-containing layer, 7: Brazing coating film, 8 ... First fillet part, 9 ... Second fillet part, 13 ... Brazing material layer, 101 ... Heat exchanger assembly.

The fin material for a heat exchanger of the present invention has a core material and a Zn-containing layer formed only on one side of the core material. After brazing, the Zn concentration is high on one side in the thickness direction, and the opposite surface side. A Zn concentration gradient with a low Zn concentration is generated, and a potential lower than the low Zn concentration side by 30 mV or more is generated on the high Zn concentration side, and the brazing material provided from the heat exchanger tube or separately added brazing material It is the fin material for heat exchangers to be brazed, and the core material is Mn: 0.5 to 2.0 mass%, Fe: 1.0 mass% or less, Si: 1.5 mass% or less, Zn: 0 It is characterized by comprising an aluminum alloy having a composition of more than .1 to 3.5% by mass, the balance inevitable impurities and aluminum.
In the fin material for a heat exchanger of the present invention, it is preferable that 0.5 to 5.0% by mass of Zn is present on the surface of the core material on the Zn-containing layer side after brazing.

Claims (4)

There is a Zn-containing layer formed only on one side of the core and the core, and after brazing, there is a Zn concentration gradient with a high Zn concentration on one side in the thickness direction and a low Zn concentration on the opposite side. A heat exchanger fin material that is generated and has a potential lower than that of the core material on the high Zn concentration side by 30 mV or more and is brazed from a heat exchanger tube or brazed by a separately added brazing material. ,
The core material is Mn: 0.5 to 2.0% by mass, Fe: 1.0% by mass or less, Si: 1.5% by mass or less, Zn: more than 0.1 to 3.5% by mass, the remainder is inevitable A fin material for a heat exchanger comprising an aluminum alloy having a composition of impurities and aluminum.   2. The fin material for a heat exchanger according to claim 1, wherein 0.5 to 5.0 mass% of Zn is present on the surface of the core material on the Zn-containing layer side after brazing. A Zn concentration gradient is generated with a high Zn concentration on one side in the thickness direction of the core material and a low Zn concentration on the opposite side, and the potential on the high Zn concentration side is lower by 30 mV or more than the potential on the low Zn concentration side. The heat-exchanger fin material is made of brazing material introduced from the heat-exchanger tube, or separately added brazing material, Si: 0.05 to 1.0 mass%, Mn: 0.1 to 1.5 mass %, Cu: a heat exchanger brazed to a heat exchanger tube in which the balance regulated to 0.05% by mass or less is Al and inevitable impurities,
The core material is Mn: 0.5 to 2.0% by mass, Fe: 1.0% by mass or less, Si: 1.5% by mass or less, Zn: more than 0.1 to 3.5% by mass, the remainder is inevitable Made of an aluminum alloy having a composition of impurities and aluminum,
The heat exchanger characterized in that the potential on the low Zn concentration side of the fin material is set to a potential lower by 30 mV or more than the potential of the tube.   The heat exchanger according to claim 3, wherein 0.5 to 5.0 mass% of Zn is present on the surface of the core material on the high Zn concentration side.

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