JP2019168145A - Tube for heat exchanger and method for manufacturing heat exchanger - Google Patents

Abstract

An object of the present invention is to provide a tube for a heat exchanger, which can make the thickness of a coating film smaller than before and which has excellent corrosion resistance after brazing, and a method for manufacturing a heat exchanger using the tube for a heat exchanger. A tube for a heat exchanger includes a tube body and a coating film applied to a surface of the tube body. The tube main body 11 contains Mn: 0.40 to 1.7% by mass, Si: 0.15% by mass or less, Cu: 0.10% by mass or less, and the remainder contains a chemical component composed of Al and unavoidable impurities. Have. The coating film 2 is composed of 1 g / m 2 or more and 4 g / m 2 or less Si powder having a cumulative 99% particle size on a volume basis of more than 20 μm and 35 μm or less, and 1 g / m 2 or more and 9 g / m 2 or less of a Zn-containing compound. A mixed powder containing the contained flux powder; and a binder. The ratio of the binder in the coating film 2 is 5 to 40% by mass. [Selection diagram] Fig. 1

Description

  The present invention relates to a heat exchanger tube and a method of manufacturing a heat exchanger.

  Generally, aluminum materials (including aluminum and aluminum alloys; the same applies hereinafter) that are lightweight and have high thermal conductivity are used for automotive heat exchangers such as evaporators and condensers. This type of heat exchanger has, for example, a tube called a multi-hole tube, in which a plurality of refrigerant flow paths partitioned by a partition are provided inside the tube. In manufacturing a heat exchanger, after assembling a structure including a tube and other members such as fins, a fluoride system is attached to a portion to be joined between members, that is, a portion to be joined by brazing. A method is adopted in which flux is applied and these members are joined by brazing. Moreover, brazing is normally performed in an inert gas atmosphere.

  In recent years, there has been a demand for further reduction in weight of a heat exchanger for automobiles in order to improve the fuel efficiency of the automobile and reduce the environmental load. From such a viewpoint, it is strongly desired to reduce the thickness of a tube such as a multi-hole tube used in a heat exchanger for automobiles for the purpose of reducing the weight. However, if penetration occurs due to corrosion in the tube during use of the heat exchanger, the function as a heat exchanger cannot be achieved due to refrigerant leakage. Therefore, in order to make the tube thickness thinner, it is necessary to improve the corrosion resistance.

  Conventionally, as a method for improving the corrosion resistance of a tube, a method of previously attaching Zn to the surface of the tube by a method such as thermal spraying has been used. Zn adhering to the surface of the tube diffuses by heating during brazing and forms a Zn diffusion layer on the surface of the tube. When this Zn diffusion layer acts as a sacrificial anode for a portion deeper than the Zn diffusion layer, it is possible to suppress the progress of corrosion in the thickness direction of the tube and to extend the penetration life.

  However, in the above method, it is necessary to perform an operation of applying a fluoride-based flux to a tube or the like after performing an operation of previously attaching Zn to the surface of the tube. In this case, a fin made of a brazing sheet in which a brazing material is clad on the core material is required. Therefore, it is difficult to reduce manufacturing costs and material costs in the above method. In addition, when Zn spraying is performed, there is a problem that the yield is poor, which may further increase the cost. Furthermore, Zn spraying tends to cause variations in the amount of Zn deposited on the surface of the tube. In particular, there is a problem that the amount of Zn deposited in the width direction of the tube is uneven and corrosion resistance tends to vary.

To solve these problems, a technique for forming a flux layer including an Si (silicon) powder, a Zn-containing flux, a Zn-free flux and a binder on the outer surface of the tube has been proposed. As an example of such a technique, Patent Document 1 discloses that the amount of Si powder applied to an Al alloy extruded tube is in the range of 1 g / m ^{2 to} 5 g / m ² and the amount of Zn-containing flux applied is 3 g / m ² or more. A heat exchanger tube with a flux layer in the range of 20 g / m ² or less is described. In the flux layer of Patent Document 1, Si powder having a 99% particle size (D ₉₉ ) of 5 μm or more and 20 μm or less is used.

Japanese Patent No. 5809728

  When brazing using the heat exchanger tube of Patent Document 1, the surface of the aluminum oxide film or Si powder existing on the surface of the tube main body or fin by the Zn-containing flux and the Zn-free flux during brazing It is necessary to remove the silicon oxide film present in the substrate. In order to remove these oxide films, it is necessary to sufficiently increase the contents of the Zn-containing flux and the Zn-free flux.

  Increasing the content of Zn-containing flux or non-Zn-containing flux increases the thickness of the flux layer. However, when a heat exchanger is made using a heat exchanger tube having a thick flux layer, the dimensions of the heat exchanger after brazing are reduced before the brazing because the flux layer melts during brazing. It tends to be smaller than Therefore, there is a possibility that the dimensions of the heat exchanger are likely to deviate from the desired dimensions.

  When the flux layer is thick, a relatively large gap is likely to be formed between the tube and the fin due to melting of the flux layer. As a result, a fillet is not formed between the tube and the fin, and brazing may not be performed.

  The present invention has been made in view of such a background. The thickness of the coating film can be made thinner than before, and the heat exchanger tube excellent in corrosion resistance after brazing and the heat exchanger tube are used. An object of the present invention is to provide a method for manufacturing a heat exchanger.

One aspect of the present invention is a chemistry containing Mn: 0.40 to 1.7% by mass, Si: 0.15% by mass or less, Cu: 0.10% by mass or less, with the balance being Al and inevitable impurities. A tube body having components;
Having a coating applied to the surface of the tube body;
The coating film
Containing 1 g / m ² or more and 9 g / m ² or less of Zn containing 1 g / m ² or more and 4 g / m ² or less of Si powder having a cumulative 99% particle size of 20 μm to 35 μm on a volume basis A mixed powder containing flux powder,
A binder, and
It exists in the tube for heat exchangers whose ratio of the said binder in the said coating film is 5-40 mass%.

Another aspect of the present invention is a method of manufacturing a heat exchanger using the heat exchanger tube of the above aspect,
A plurality of the heat exchanger tubes are arranged in parallel via fins, the core in which the heat exchanger tubes and the fins are alternately stacked, and at both ends of the core in the longitudinal direction of the heat exchanger tubes Making an assembly with an arranged header;
A method of manufacturing a heat exchanger, wherein the assembly is heated to braze the heat exchanger tube and the fins, and a heat exchanger is produced by brazing the heat exchanger tube and the header. It is in.

  The heat exchanger tube has a tube main body and a coating film applied to the surface of the tube main body. The coating film contains Si powder having a particle size distribution represented by a cumulative 99% particle size in the specific range and Zn-containing flux powder. The Zn-containing flux powder is composed of a compound containing Zn, and can react with Al in the tube body by heating during brazing to generate a flux component and Zn. By this flux component, the Si oxide film present on the surface of each particle constituting the Si powder and the Al oxide film present on the surface of the tube body can be removed and brazing can be performed.

  Further, Zn generated from the Zn-containing flux powder diffuses into the tube body to form a Zn diffusion layer, and can form a potential gradient from the surface of the tube body to the deep part where the surface is base and the deep part is noble. . As a result, the surface layer portion of the tube body becomes a sacrificial anode, and the corrosion resistance of the deep portion of the tube body can be improved.

  In addition, by making the particle size distribution of the Si powder a distribution represented by a cumulative 99% particle size in the specific range, the Si powder has a larger proportion of finer particles than the case where the Si powder is used. The ratio of the surface area to the mass can be reduced. Therefore, the oxide film of Si contained in the Si powder can be removed with a smaller amount of Zn-containing flux powder, and the tube body and the fin can be brazed.

  As mentioned above, according to the said tube for heat exchangers, the quantity of Zn containing flux powder can be reduced rather than before, without impairing brazing property and the corrosion resistance after brazing. As a result, the heat exchanger tube can be made thinner than the conventional heat exchanger tube.

  And the shrinkage | contraction amount of the dimension of the heat exchanger at the time of brazing can be reduced by using the said tube for heat exchangers. Furthermore, according to the said tube for heat exchangers, the clearance gap between the tube and a fin at the time of brazing can be made small, and the brazing defect of a tube and a fin can be suppressed.

The perspective view of the tube for heat exchangers in an Example. The perspective view of the heat exchanger produced using the tube for heat exchangers in an Example.

  The configuration of the tube will be described in detail below.

(Tube body)
The form of the tube body is not particularly limited, and can be appropriately selected according to the use and required characteristics. For example, the tube body can be an extruded multi-hole tube formed by extrusion and having a plurality of refrigerant channels therein. Further, the tube body may have a simple cylindrical shape. In this case, the tube body may be produced by extrusion, or may be produced by bending the plate material.

  The tube body is made of an aluminum material. The material of the aluminum material can be appropriately selected from known aluminum and aluminum alloys according to desired properties.

  For example, the said tube main body may be comprised from the aluminum alloy which contains Mn: 0.40-1.7 mass%, and the remainder has a chemical component which consists of Al and an unavoidable impurity.

Mn (manganese): 0.40 to 1.7% by mass
Mn has the effect of improving the strength of the tube body by dissolving in the Al matrix. By setting the content of Mn in the tube main body to 0.40 mass% or more, preferably 0.50 mass% or more, the strength of the tube main body can be improved. When the content of Mn in the tube body is less than 0.40% by mass, the strength of the tube body may be lowered.

  On the other hand, when the content of Mn is increased, the workability in the extrusion process is lowered, and the productivity of the tube body may be lowered. By setting the content of Mn in the tube body to 1.7% by mass or less, preferably 1.5% by mass or less, the strength of the tube body can be improved while avoiding this problem.

  Moreover, Al-Mn type | system | group precipitate can be deposited in Al mother phase by making content of Mn in a tube main body into the said specific range. As a result, a sufficient amount of molten brazing is distributed to a plurality of planned joining portions such as a joining portion between the tube main body and the fin and a planned joining portion between the tube main body and the header, thereby suppressing the occurrence of defective brazing. Can do. As this reason, the following reasons can be considered, for example.

  When brazing using the tube, the molten braze flows along the surface of the tube body, and a plurality of joints such as a joint portion between the tube body and the fin and a joint portion between the tube body and the header. It is distributed to the planned part.

  At this time, depending on the size of the gap between the tube main body and the fin and the size of the gap between the tube main body and the header, the molten brazing concentrates on a specific planned joining portion among the plurality of planned joining portions, and other joining plans There may be a lack of melting wax in the part. Such concentration of the molten solder is likely to occur at a portion where the tube main body and the fin are to be joined. On the other hand, when the melting braze moves to the planned joining portion between the tube main body and the fin, the melting brazing is insufficient at the planned joining portion between the tube main body and the header, and a brazing defect is likely to occur.

  When Al—Mn-based precipitates are deposited on the tube body, a part of the Al—Mn-based precipitates is exposed on the surface of the tube body. This Al—Mn-based precipitate has an action of hindering the flow of the molten solder. Therefore, by exposing the Al-Mn-based precipitates on the surface of the tube body, the concentration of the melting brazing to the specific planned joining portion as described above is suppressed, and a sufficient amount of the molten brazing is applied to each scheduled joining portion. Can be distributed. As a result, it is possible to suppress the occurrence of brazing defects due to the concentration of the molten brazing.

-Si (silicon): 0.15 mass% or less The said tube main body may contain Si: 0.15 mass% or less further as an arbitrary component. Si exists as an AlMnSi intermetallic compound in the Al matrix. When the AlMnSi-based intermetallic compound in the Al matrix is sandwiched between the die and the tube body in the extrusion process of the tube body, a groove called a die mark is formed in the tube body.

  When the Si content in the tube body is increased, the AlMnSi intermetallic compound is coarsened, so that the dice mark is likely to be deepened. If a deep die mark exists on the outer surface of the tube body, excessive brazing solder generated at the header or the like reaches the fins through the die mark during brazing, and the amount of fin melting is excessive. May increase. From the viewpoint of avoiding such a problem, the content of Si in the tube body is preferably 0.15% by mass or less, and more preferably 0.10% by mass or less.

-Cu (copper): 0.10 mass% or less The said tube main body may contain Cu: 0.10 mass% or less further as an arbitrary component. When brazing is performed using the tube, Zn produced by the reaction between the Zn-containing flux powder and Al diffuses in the depth direction, thereby forming a Zn diffusion layer on the surface of the tube body. In the Zn diffusion layer formed in this way, the Zn concentration on the surface is lower than when Zn is directly attached to the surface of the tube body, such as Zn spraying.

  On the other hand, Cu in the tube body has a function of making the potential of the tube body noble. Furthermore, when brazing is performed using the tube, simultaneously with the diffusion of Zn, Si supplied from the Si powder is also diffused in the depth direction to form a Si diffusion layer. This Si diffusion layer also has the effect of making the potential of the tube body noble like Cu.

  In such a situation, when the content of Cu is excessively large, the effect of potential nomination due to the Si diffusion layer and Cu becomes higher than the effect of potential denaturation due to Zn, and the sacrificial anticorrosion effect due to the Zn diffusion layer is obtained. There is a risk of disappearing.

  In order to make the effect of potential lowering due to Zn greater than the effect of potential nomination due to Si diffusion layer and Cu, a method of simply increasing the amount of Zn-containing flux powder in the coating film can be considered. However, in this case, since the thickness of the coating film increases, a large gap is formed between the tube main body and the fin during brazing, resulting in increased brazing failure and increased dimensional change of the heat exchanger. It becomes easy. In this case, the Zn concentration of the fillet formed between the tube body and the fin tends to increase. Therefore, the fillet may corrode early and the fin may peel off from the tube body early.

  Moreover, when the content of Cu in the tube main body is increased, the workability in the extrusion process is lowered, and the productivity of the tube main body may be lowered.

  By making the content of Cu in the tube main body 0.10% by mass or less, preferably 0.050% by mass or less, more preferably less than 0.030% by mass, the above-described problems are avoided, and the Zn diffusion layer is used. A sacrificial anticorrosive effect can be obtained.

-Ti (titanium): 0.30 mass% or less The said tube main body may contain Ti: 0.30 mass% or less further as an arbitrary component. When Ti is contained in the tube body, a high concentration region having a relatively high Ti concentration and a low concentration region having a relatively low concentration are alternately stacked in the thickness direction of the tube body. Since the low concentration region is more easily corroded than the high concentration region, the progress of corrosion in the thickness direction can be suppressed by forming the low concentration region having a relatively low Ti concentration in a layered manner. As a result, the pitting corrosion resistance and intergranular corrosion resistance of the tube body can be further improved.

  Further, when Ti is contained in the tube body, the strength at normal temperature and high temperature can be further improved.

  However, if the Ti content in the tube body is excessively large, giant crystals are produced during casting, which may make it difficult to produce a sound tube body. In this case, the crystallized material described above is sandwiched between the die and the tube body during the extrusion of the tube body, and a deep die mark may be formed in the tube body. By setting the Ti content to 0.30 mass% or less, the above-described effects of Ti can be obtained while avoiding such problems.

-Sr (strontium): 0.10 mass% or less The said tube main body may contain further Sr: 0.10 mass% or less as an arbitrary component. Sr has the effect of refining and uniformly dispersing the eutectic structure that crystallizes when the molten solder solidifies upon cooling. Since this eutectic structure becomes an anode site, the corrosion form can be made planar by dispersing the eutectic structure. As a result, the corrosion resistance of the tube body can be further improved.

  However, if the Sr content in the tube body is excessively large, the Al—Si—Sr compound is crystallized, and thus the eutectic structure may not be sufficiently refined. In this case, in the extrusion process of the tube body, an Al—Si—Sr compound is sandwiched between the die and the tube body, and a deep die mark may be formed in the tube body. By setting the content of Sr to 0.10% by mass or less, such a problem can be avoided and the corrosion resistance can be further improved.

-Zr (zirconium): 0.30 mass% or less The said tube main body may contain Zr: 0.30 mass% or less further as an arbitrary component. Zr has the effect of coarsening the recrystallized grains and lowering the grain boundary density when the aluminum material is recrystallized by heating during brazing. By reducing the grain boundary density on the surface of the tube main body with Zr, it is possible to suppress the penetration of the Al—Si alloy molten brazing generated during brazing into the crystal grain boundary of the base material, thereby preventing the corrosion of the grain boundary. It can suppress more effectively.

  However, when the content of Zr is excessively large, giant crystallized substances are generated during casting, which may make it difficult to produce a sound tube body. In this case, the crystallized material described above is sandwiched between the die and the tube body during the extrusion of the tube body, and a deep die mark may be formed in the tube body. By setting the Zr content to 0.30% by mass or less, it is possible to more effectively suppress the grain boundary corrosion while avoiding these problems.

(Coating)
A coating film is formed on the surface of the tube body. The coating film contains a mixed powder containing Si powder and Zn-containing flux powder, and a binder. The coating film can be formed, for example, by applying a paste obtained by mixing a mixed powder and a binder in a solvent to the tube body and then drying the solvent. The paste can be applied by, for example, a roll coating method.

Si powder: 1 g / m ² or more and 4 g / m ² or less The Si powder reacts with Al in the tube body by heating at the time of brazing to produce a molten brazing composed of an Al—Si alloy. By setting the content of the Si powder in the specific range, a sufficient amount of melting brazing is supplied to the portion to be joined between the tube and the fin, the portion to be joined between the tube and the header, and the tube is connected to the fin and the header. Can be brazed. The content of Si powder is preferably ² g / m ² or more. In this case, it is possible to increase the amount of the molten solder supplied between the tube and the fin, between the tube and the header, and to improve the brazing performance.

When the content of the Si powder is less than 1 g / m ² , the amount of the brazing filler is insufficient, so that brazing defects are likely to occur. On the other hand, when the content of Si powder exceeds 4 g / m ² , the amount of flux component generated from the Zn-containing flux powder and the amount of Zn diffusing into the tube body may be insufficient. For this reason, the oxide film in the Si powder cannot be sufficiently removed, and the brazing property may be lowered. Moreover, there exists a possibility of causing a fall of corrosion resistance.

The cumulative 99% particle size (that is, D ₉₉ ) on a volume basis of the Si powder contained in the coating film is more than 20 μm and not more than 35 μm. By making the particle size distribution of the Si powder a particle size distribution represented by a cumulative 99% particle size in the specified range, the proportion of particles having a relatively large particle size is increased in the particle size distribution of the Si particles. Can do. Therefore, according to the Si powder, the proportion of the Si oxide film contained in the unit mass of the Si powder can be reduced.

  And by reducing the ratio of the Si oxide film contained in the Si powder, the amount of the flux component consumed for removing the Si oxide film is reduced, and consequently the content of the Zn-containing flux powder. Can be reduced. As a result, the thickness of the coating film can be further reduced. Further, in this case, the flowability of the molten brazing generated during the brazing addition heat can be further improved as compared with the case where Si powder having a cumulative 99% particle size of 20 μm or less is used.

  From the viewpoint of reducing the thickness of the coating film, it is preferable to increase the proportion of particles having a relatively large particle size in the particle size distribution of the Si particles. However, if the value of the cumulative 99% particle size becomes excessively large, coarse particles of Si are likely to be included in the coating film. In this case, in a portion where coarse particles are present, there is a possibility that a melting hole due to local Al—Si eutectic melting occurs during brazing. By setting the cumulative 99% particle size of the Si powder to 35 μm or less, preferably 30 μm or less, such a problem can be avoided, and formation of molten holes in the tube body can be suppressed.

  The cumulative 99% particle size and the cumulative 50% particle size of the Si powder are values calculated based on the volume-based particle size distribution obtained by the laser diffraction method.

Zn-containing flux powder: 1 g / m ² or more and 9 g / m ² or less The mixed powder contains Zn and is composed of a compound capable of reducing aluminum oxide and zinc oxide. Is included. As Zn-containing flux powder, for example, KZnF ₃ can be used.

  The Zn-containing flux powder reacts with Al in the tube main body by brazing heat and generates a flux component and Zn. By setting the content of the Zn-containing flux powder within the specific range, the effect of improving corrosion resistance by Zn can be obtained. Furthermore, by setting the content of the Zn-containing flux powder within the above specific range, the oxide film in the Si powder and the oxide film present on the surface of the tube body are removed by the flux component, and the tube and fin are brazed. Attaching can be done.

When the content of the Zn-containing flux powder is less than 1 g / m ² , the Zn concentration on the surface of the tube main body after brazing becomes low, and the corrosion resistance of the tube main body may be lowered. In this case, since the amount of flux component generated from the Zn-containing flux powder is insufficient, there is a possibility that the brazing property is deteriorated. From the viewpoint of improving the sacrificial protection effect of Zn, the Zn content containing flux powder is preferably adjusted to 2 g / m ² or more, and more preferably set to 3 g / m ² or more.

On the other hand, when the content of the Zn-containing flux powder increases, the Zn concentration of the fillet formed between the tube body and the fin tends to increase. In this case, the fillet may corrode earlier than the tube main body and the fin, and the fin may be easily peeled off from the tube main body. By making the content of the Zn-containing flux powder 9 g / m ² or less, the sacrificial anticorrosive effect by Zn can be obtained while avoiding this problem. From the same viewpoint, the content of the Zn-containing flux powder is preferably 8 g / m ² or less, and more preferably 7 g / m ² or less.

  The particle size distribution of the Zn-containing flux powder is not particularly limited. For example, a Zn-containing flux powder having a cumulative 50% particle size on the basis of volume of about 5 μm can be used. The cumulative 50% particle size of the Zn-containing flux powder is a value calculated based on a volume-based particle size distribution obtained by a laser diffraction method. The same applies to the Zn-free flux powder described later.

Zn-free flux powder: 9 g / m ² or less The mixed powder may contain a Zn-free flux powder in addition to the Si powder and the Zn-containing flux powder as essential components. The Zn-free flux powder is made of a compound that does not contain Zn and can reduce aluminum oxide and zinc oxide. As the Zn-free flux powder, for example, K—Al—F-based compounds such as KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ can be used. These compounds may be used alone or in combination.

  The Zn-free flux powder in the mixed powder is melted by heating during brazing. The melt of this Zn-free flux powder supplements the flux components generated from the Zn-containing flux powder, and the brazing properties are further improved by removing the oxide film in the Si powder and the oxide film on the tube body. Can do.

  Moreover, the Zn density | concentration in mixed powder can be moderately reduced by adding Zn non-containing flux powder in mixed powder. Therefore, in this case, an excessive increase in the Zn concentration of the fillet formed between the tube body and the fin can be suppressed, and the progress of the corrosion of the fillet can be delayed. As a result, the peeling of the fin from the tube body can be suppressed for a longer period.

From the viewpoint of sufficiently obtaining the above-described effects by the Zn-free flux powder, the content of the Zn-free flux powder is preferably 1 g / m ² or more, and more preferably 2 g / m ² or more.

The Zn-free flux powder is preferably 9 g / m ² or less, more preferably 8 g / m ² or less, and even more preferably 7 g / m ² or less. In this case, it is possible to further improve the brazing property while ensuring the corrosion resistance of the tube body. When the content of the Zn-free flux powder exceeds 9 g / m ² , the Zn concentration in the Zn diffusion layer formed on the tube body becomes excessively low, which may reduce the corrosion resistance of the tube body.

  The average particle size of the non-Zn-containing flux powder is not particularly limited, and for example, a non-Zn-containing flux powder having a cumulative 50% particle size of about 5 μm on a volume basis can be used.

-Total amount of mixed powder The total amount of the mixed powder, that is, the total mass of the Si powder, the Zn-containing flux powder, and the Zn-free flux powder is, for example, appropriately within the range of 3 g / m ² or more and 20 g / m ² or less. Can be set. By setting the total amount of the mixed powder to 3 g / m ² or more, a sufficient amount of molten brazing is supplied to the portion to be joined between the tube body and the fin and the portion to be joined between the tube body and the header. It can be performed. Moreover, it can avoid that the thickness of a coating film becomes thick too much by the total amount of mixed powder being 20 g / m < ² > or less.

・ Binder: 5-40% by mass
As the binder, for example, an acrylic resin or a urethane resin can be used. The content of the binder is 5 to 40% by mass when the entire coating film, that is, the total of the mixed powder and the binder is 100% by mass. When the content of the binder is less than 5% by mass, the coating film is easily peeled off. On the other hand, when the content of the binder exceeds 40% by mass, the thermal decomposition of the binder becomes insufficient, and there is a possibility that an undecomposed binder or the like may remain during brazing. As a result, there is a risk of reducing brazing properties.

(Heat exchanger)
In producing a heat exchanger using the tube, for example, the following method can be employed. First, a plurality of tubes, fins made of an aluminum alloy, and a header made of an aluminum alloy and distributing a refrigerant to the plurality of tubes are prepared. Next, the tubes and the fins are alternately laminated so that the fins come into contact with the coating film provided on the outer surface of the tube, and a core in which a plurality of heat exchanger tubes are arranged in parallel via the fins is formed. assemble. Furthermore, a header is arrange | positioned at the both ends of the core in the longitudinal direction of a tube, and the several tube for heat exchangers is connected through a header.

  A heat exchanger can be manufactured by brazing the tube and the header while heating the assembly assembled in this way to braze the tube and the fin. The atmosphere, heating temperature, and time for brazing are not particularly limited, and the brazing method is not particularly limited.

  As the aluminum alloy used for the fin and the header, a known alloy can be used as long as it has sufficient strength and corrosion resistance for a heat exchanger.

  For example, the fin may include a chemical component including Mn: 0.10 to 1.8 mass%, Zn: 0.80 to 3.0 mass%, and the balance being Al and inevitable impurities.

  Mn in the fin has an effect of increasing the strength of the fin. By setting the content of Mn in the fin to 0.10% by mass or more, more preferably 0.80% by mass or more, the strength of the fin can be further improved, and consequently the strength of the heat exchanger can be further improved. .

  However, if the Mn content in the fin is excessively large, a strong crystallized product is likely to be formed in the fin manufacturing process. By setting the Mn content to 1.8% by mass or less, more preferably 1.7% by mass or less, formation of huge crystallized substances can be avoided and a sound fin can be produced.

  Zn in the fin has an action of lowering the potential of the fin. By setting the Zn content in the fin to 0.80% by mass or more, more preferably 1.0% by mass or more, the potential of the fin is made lower than the tube body and the fillet between the fin and the tube body. be able to. As a result, the corrosion resistance of the tube body can be further improved by the sacrificial anticorrosive effect of the fins.

  However, when the Zn content in the fin is excessively large, the self-corrosion resistance of the fin is lowered, and the fin may be corroded early. In this case, the potential difference between the tube body and the fin and the potential difference between the fillet and the fin are increased. Therefore, when a liquid having high conductivity such as condensed water adheres to the surface of the fin or the like, a local battery is formed between the tube main body and the fin or between the fillet and the fin, and becomes an anode. Fins may corrode early. These problems can be avoided by setting the Zn content in the fin to 3.0 mass% or less, more preferably 2.5 mass% or less.

  The fin may further contain 0.10 to 1.2% by mass of Si as an optional component. By setting the content of Si in the fin to 0.10% by mass or more, more preferably 0.20% by mass or more, the strength of the fin can be further improved. In addition, the content of Si in the fin is 1.2% by mass or less, more preferably 0.60% by mass or less, thereby suppressing a decrease in the melting point of the fin and avoiding local melting of the fin during brazing. can do.

  The fin may further contain 0.010 to 0.80% by mass of Fe (iron) as an optional component. By making the content of Fe in the fin 0.010% by mass or more, more preferably 0.10% by mass or more, the strength of the fin can be further improved. Further, by making the content of Fe in the fin 0.80% by mass or less, more preferably 0.70% by mass or less, formation of an Al—Fe-based compound having a noble potential as compared with the Al matrix is formed. Can be suppressed. As a result, a decrease in the self-corrosion resistance of the fin can be avoided.

  The fin may further contain 0.050 to 0.50% by mass of Mg (magnesium) as an optional component. By setting the Mg content in the fin to 0.050 mass% or more, the strength of the fin can be further improved.

  However, when the content of Mg in the fin is excessively large, Mg and flux react during brazing, and Mg fluoride is easily formed. When the amount of the Mg fluoride is excessively large, there is a possibility that the brazing property is deteriorated and the appearance after brazing is deteriorated. These problems can be avoided by setting the Mg content in the fin to 0.50 mass% or less, more preferably 0.30 mass% or less, and even more preferably 0.15 mass% or less.

  The fin may further contain 0.30% by mass or less of Cu as an optional component. By setting the Cu content in the fin to 0.30 mass% or more, the strength of the fin can be further improved. In this case, the corrosion resistance of the tube body can be further improved by the sacrificial anticorrosion effect while adjusting the potential of the fin to an appropriate range and avoiding the deterioration of the self-corrosion resistance of the fin. Further, in this case, the progress of the corrosion of the fillet between the tube body and the fin can be further delayed, and the peeling of the fin from the tube body can be suppressed.

  The fin may further contain one or two of 0.30% by mass or less of Cr (chromium) and 0.30% by mass or less of Zr as optional components. In this case, when the aluminum material is recrystallized by heating at the time of brazing, the recrystallized grains are coarsened, and a decrease in strength of the fins during brazing can be suppressed. As a result, occurrence of buckling of the fin during brazing can be more effectively suppressed. In addition, when the Cr and Zr contents are each 0.30% by mass or less, the formation of giant crystals in the fin production process can be suppressed, and a sound fin can be produced.

  The fin may further contain 0.30% by mass or less of Ti as an optional component. Ti in the fin can suppress the progress of corrosion in the thickness direction of the fin, similarly to Ti in the tube body. Therefore, the pitting corrosion resistance and intergranular corrosion resistance of the fin can be further improved by setting the content of Ti in the fin to 0.30% by mass or less. Furthermore, in this case, the strength of the fin at normal temperature and high temperature can be further improved. In addition, when the Ti content is 0.30% by mass or less, the formation of giant crystals in the fin production process can be suppressed, and a sound fin can be produced.

  The fin may further contain one or two of 0.0010 to 0.10% by mass of In (indium) and 0.0010 to 0.10% by mass of Sn (tin) as an optional component. Good. These elements have the effect of lowering the potential of the fin, similar to Zn. By setting the contents of In and Sn in the fins within the specific ranges, the corrosion resistance of the tube body can be further improved while ensuring the self-corrosion resistance of the fins.

  Examples of the heat exchanger tube and the heat exchanger manufacturing method using the heat exchanger tube will be described below. In addition, the specific aspect of the manufacturing method of the tube for heat exchangers and heat exchangers concerning this invention is not limited to the aspect of the Example shown below, It comprises suitably in the range which does not impair the meaning of this invention. Can be changed.

  As shown in FIG. 1, the heat exchanger tube 1 of this example includes an extruded multi-hole tube 110 as a tube body 11 and a coating film 2 provided on the outer surface of the extruded multi-hole tube 110. Yes. The extruded multi-hole tube 110 of this example contains Mn: 0.70% by mass, Si: 0.050% by mass, Fe: 0.15% by mass, and the balance having chemical components composed of Al and inevitable impurities. It is composed of an aluminum alloy. The extruded multi-hole tube 110 can be produced, for example, by subjecting an ingot produced by a method such as continuous casting, semi-continuous casting, or DC casting to homogenization and then performing hot extrusion.

  As shown in FIG. 1, the extruded multi-hole tube 110 is arranged with an outer periphery 111 having an oval shape in a cross section perpendicular to the extrusion direction (that is, the ST-LT surface) and an inner side of the outer periphery. And a plurality of partition walls 112. Inside the extruded multi-hole tube 110, there are provided a plurality of refrigerant channels 113 that are partitioned by the outer peripheral portion 111 and the partition wall portion 112 and extend in the longitudinal direction of the extruded multi-hole tube 110 (that is, the extrusion direction). ing. The plurality of refrigerant channels 113 are arranged side by side in the width direction of the extruded multi-hole tube 110. In the extruded multi-hole tube 110 of this example, the thickness of the flat portion 114 of the outer peripheral portion 111 is 0.3 mm.

A coating film 2 is provided on the outer surface of the flat portion 114 in the extruded multi-hole tube 110. The coating film 2 contains Si powder, Zn-containing flux powder, Zn-free flux powder and binder. The content of each component in the coating film 2 is as shown in Table 1, for example. Further, the cumulative 99% particle size (that is, D ₉₉ ) of the Si powder on a volume basis is as shown in Table 2.

  For example, the coating film 2 is applied by applying a paste containing Si powder, Zn-containing flux powder, Zn-free flux powder, and a binder to the flat portion 114 of the extruded multi-hole tube 110 using a roll coater, and then drying the paste. Can be formed. By forming the coating film 2 in the amount shown in Table 1 on the flat portion 114 of the extruded multi-hole tube 110, the heat exchanger tubes 1 (test bodies A1 to A21) shown in Table 1 and Table 2 can be produced. .

  The assembly 3 shown in FIG. 2 is manufactured by combining the test bodies A1 to A21 with the fins 31 and the header 32 having the following configurations, and the assembly 3 is heated and brazed to manufacture a heat exchanger. be able to. In addition, about test body A20 among test bodies A1-A21, the binder amount in the coating film 2 is insufficient, and the coating film 2 peels easily from the extrusion multi-hole pipe 110. Therefore, the specimen A20 cannot be brazed with the fin 31 and the header 32.

<Fin 31>
As shown in FIG. 2, the fin 31 of this example is a so-called corrugated fin in which a plate material is curved in a wave shape. The fin 31 is made of an Al-1.2 mass% Mn-1.5 mass% Zn-based alloy. The plate thickness of the fins 31 is 0.1 mm, the pitch between the top portions 311 in the corrugated shape is 3 mm, and the height of the fins 31 is 7 mm.

<Header 32>
As shown in FIG. 2, the header 32 of this example has a cylindrical shape, and has a plurality of through holes 321 for inserting the tube 1 on its side surface. Although not shown in the drawing, the header 4 is composed of a brazing sheet including a core material and a brazing material clad on one side of the core material. The brazing material is disposed on the inner surface of the header 4.

<Heat exchanger>
First, the core 30 is manufactured by alternately stacking the tubes 1 and the fins 31 so that the fins 31 are in contact with the coating film 2 of the tube 1. Next, the both ends of the tube 1 in the core 30 are inserted into the through holes 321 of the header 32 to produce the assembly 3 shown in FIG. The assembly 3 is heated to braze the extruded multi-hole tube 110 and the fins 31 and braze the extruded multi-hole tube 110 and the header 32 together. Thus, a heat exchanger can be obtained.

  The assembly 3 can be brazed in a nitrogen gas atmosphere. Although the heating conditions at the time of brazing are not particularly limited, for example, the tube 1, the fin 31 and the header 32 are heated to 600 ° C. at a temperature rising rate of 50 ° C./min on average, and the temperature of 600 ° C. is maintained for 3 minutes. The temperature may be lowered to room temperature.

  The characteristics of each specimen can be evaluated by the following evaluation items.

<Core shrinkage>
The outer dimension of the core 30 before brazing in the stacking direction of the tube 1 and the fin 31 is compared with the outer dimension of the core 30 after brazing in the stacking direction, and whether or not the core 30 contracts before and after brazing. To evaluate. The presence or absence of contraction of the core 30 in each test specimen is as shown in the “core contraction” column of Table 2.

  In the evaluation of the dimensional change of the core, the case where the core 30 does not shrink due to brazing is judged as acceptable, and the case where the core 30 after brazing shrinks more than the core 30 before brazing is judged as unacceptable. .

<Brassability>
The area of the fillet formed between the extruded multi-hole tube 110 and the fin 31 is measured, and the brazing property is evaluated. The brazing properties when using each specimen are as shown in the “brazing properties” column of Table 2. In the same column, the symbol “A” is used when the area of the fillet when using each specimen is equal to or larger than the area of the reference fillet based on the area of the fillet when using the specimen A1. In the case where it is narrower than the reference, the symbol “B” is described. For the reference specimen A1, the symbol “-” is described.

  In the evaluation of brazing, in the case of the symbol “A” in which the area of the fillet after brazing is equal to or larger than the standard fillet area, it is judged as acceptable because the brazing property is good. The case of the symbol “B” in which the area of the fillet is less than the reference fillet area is determined to be unacceptable because of poor brazing.

<Erosion of molten solder into extruded multi-hole tube 110>
The degree of erosion of the molten brazing into the extruded multi-hole tube 110 is evaluated based on the presence or absence of molten holes in the extruded multi-hole tube 110 after brazing. The presence / absence of a melting hole when each specimen is used is as shown in the “Presence / absence of melting hole” column of Table 2.

  In the evaluation of the molten solder erosion into the extruded multi-hole tube 110, the case where the molten multi-hole tube 110 does not have a molten hole after brazing is suppressed to the extent that there is no practical problem. It is determined to be acceptable, and a case in which a molten hole is formed after brazing is determined to be unacceptable because the molten solder has excessively eroded the extruded multi-hole tube 110.

<Erosion of molten wax into fin 31>
Based on the melting amount of the fin 31 at the time of brazing, the degree of erosion of the molten brazing into the fin 31 is evaluated. The amount of melting of the fin 31 when each specimen is used is as shown in the “Minning amount of fin” column of Table 2. In the same column, the symbol “A” is indicated when the amount of melting of the fin 31 by brazing is less than half the plate thickness of the fin 31 before brazing, and the symbol “B” is indicated when it is more than half. Described.

  In the evaluation of the erosion of the brazing filler metal to the fin 31, in the case of the symbol A in which the melting amount of the fin 31 by brazing is less than half of the plate thickness of the fin 31 before brazing, the erosion of the molten solder to the fin 31 is performed. Is determined to be acceptable because it is suppressed to a level that does not cause any practical problems. Further, in the case of the symbol B in which the amount of melting of the fins 31 by brazing is more than half of the plate thickness of the fins 31 before brazing, it is determined to be rejected because the molten brazing excessively erodes the fins 31.

<Corrosion resistance>
The SWAAT test specified in ASTM-G85-Annex A3 is performed on the heat exchanger after brazing for 1000 hours, and the maximum corrosion depth of the extruded multi-hole tube 110 after the test is completed is measured. The presence or absence of peeling is determined. Based on the maximum corrosion depth of the extruded multi-hole tube 110, the corrosion resistance of the extruded multi-hole tube 110 can be evaluated. Further, the Zn concentration of the fillet between the extruded multi-hole tube 110 and the fin 31 can be evaluated based on whether or not the fin 31 is peeled after the SWAAT test.

  The maximum corrosion depth of the extruded multi-hole tube 110 when each test specimen is used is as shown in the “maximum corrosion depth” column of Table 2. In the same column, symbol “A” is described when the maximum corrosion depth is shallower than the depth of the Zn diffusion layer, and symbol “B” is described when the maximum corrosion depth is deeper than the depth of the Zn diffusion layer. The depth of the Zn diffusion layer is the thickness of the region where the Zn concentration measured by EDX (energy dispersive X-ray spectroscopy) is higher than that of the extruded multi-hole tube 110 in the cross section of the extruded multi-hole tube 110.

  In the evaluation of the corrosion resistance of the extruded multi-hole tube 110, the case where the maximum corrosion depth is “A”, which is shallower than the depth of the Zn diffusion layer, is determined to be acceptable because the corrosion can be suppressed, and the maximum corrosion depth is The case of symbol “B” deeper than the depth of the Zn diffusion layer is determined to be rejected because the sacrificial anticorrosive effect is low.

  Further, the presence / absence of peeling of the fin 31 after the SWAAT test is as shown in the “Presence / absence of fin peeling” column of Table 2. In the evaluation of the Zn concentration of the fillet, the case where the fin 31 does not peel from the extruded multi-hole tube 110 after the SWAAT test is determined to be acceptable because the Zn concentration of the fillet is in an appropriate range, and the fin 31 is the extruded multi-hole tube 110. Is peeled off because the Zn concentration in the fillet is high and the progress of corrosion is fast.

  As shown in Table 1, the specimens A1 to A9 have the coating film 2 having the specific composition. Therefore, the heat exchanger using these specimens passes all the characteristics.

  The content of Si powder in the specimen A10 is less than the specific range. For this reason, when the specimen A10 is used, the amount of molten brazing generated during brazing is insufficient, and the brazing property is likely to deteriorate.

  The content of Si powder in the specimen A11 is larger than the specific range. Therefore, when the test body A11 is used, the fins 31 are excessively eroded by the molten solder, and are likely to be poorly brazed. In this case, the extruded multi-hole tube 110 is excessively eroded by the melting wax, and the amount of the extruded multi-hole tube 110 is likely to increase. Therefore, it becomes difficult to form a Zn diffusion layer in the extruded multi-hole tube 110 after brazing, and the corrosion resistance of the extruded multi-hole tube 110 may be reduced. In this case, the fins 31 are easily peeled off from the extruded multi-hole tube 110 at an early stage.

  Since the cumulative 99% particle size of the Si powder in the specimen A12 is smaller than the specific range, the proportion of the oxide film contained in the Si powder is large. Therefore, when using the test body A12, the amount of the flux component is insufficient, and the brazing property is likely to deteriorate. In this case, the size of the fillet formed between the extruded multi-hole tube 110 and the fins 31 tends to be small. Therefore, the fin 31 is easily peeled off from the extruded multi-hole tube 110 at an early stage due to the corrosion of the fillet.

The cumulative 99% particle size of the Si powder in the specimen A13 is larger than the specific range. Therefore, when the specimen A13 is used, the extruded multi-hole tube 110 is locally eroded by the coarse particles of Si present in the coating film 2, and a molten hole is formed in the extruded multi-hole tube 110 after brazing. Easy to be.
Regarding the test specimen A14, the cumulative 99% particle size of the Si powder is larger than that of the specific range as compared with the test specimen A13. Therefore, in the case of using the test body A14, not only the melted holes are formed in the extruded multi-hole tube 110 after brazing but also the corrosion resistance of the extruded multi-hole tube 110 is deteriorated and the fins 31 are easily peeled off at an early stage. .

  The content of Zn-containing flux powder in the specimen A15 is less than the specific range. Therefore, when using test body A15, the quantity of the flux component produced at the time of brazing is insufficient, and the brazing property tends to deteriorate. Moreover, when using test body A15, since the quantity of Zn produced at the time of brazing is also insufficient, the corrosion resistance of the extruded multi-hole tube 110 is lowered and the fins 31 are easily peeled off at an early stage.

  The content of the Zn-containing flux powder in the specimen A16 is larger than the specific range. Therefore, the Zn concentration in the fillet between the extruded multi-hole tube 110 and the fin 31 is increased. Therefore, when the specimen A16 is used, the Zn concentration in the fillet between the extruded multi-hole tube 110 and the fin 31 increases, and the fillet corrodes earlier than the extruded multi-hole tube 110 and the fin 31. As a result, the fin 31 is easily peeled off from the extruded multi-hole tube 110 at an early stage.

  The content of the Zn-free flux powder in the specimen A17 is larger than the specific range. Therefore, when using the test body A17, the Zn concentration of the Zn diffusion layer in the extruded multi-hole tube 110 after brazing becomes low, and the corrosion resistance of the extruded multi-hole tube 110 tends to decrease.

  The content of the mixed powder in the specimen A18 is less than the specific range. Therefore, when using test body A18, the quantity of the flux component produced at the time of brazing is insufficient, and the brazing property tends to deteriorate. Further, when the specimen A18 is used, the amount of Zn generated at the time of brazing is also insufficient, so that the corrosion resistance of the extruded multi-hole tube 110 is reduced and the fins 31 are easily peeled off at an early stage.

  The content of the mixed powder in the specimen A19 is larger than the specific range. Therefore, when using test body A19, the core 200 tends to shrink by melting of the coating film 2 at the time of brazing.

  As described above, the specimen A20 cannot maintain the state in which the coating film 2 is adhered to the surface of the extruded multi-hole tube 110 because the binder content is less than the specific range. Therefore, it is difficult to produce a heat exchanger using the specimen A20.

  Specimen A21 has a binder content larger than the specific range, and it is difficult to completely thermally decompose the binder by heating during brazing. Therefore, when using the specimen A21, the eutectic melting reaction between the Si powder and the extruded multi-hole tube 110 and the reaction between the Zn-containing flux powder and the extruded multi-hole tube 110 are hindered by the binder residue, and the heat exchanger Is difficult to produce.

DESCRIPTION OF SYMBOLS 1 Heat exchanger tube 11 Tube body 110 Extruded multi-hole tube 2 Coating film 3 Assembly 20 Core 31 Fin 32 Header

Claims (7)

A tube body made of an aluminum material;
Having a coating applied to the surface of the tube body;
The coating film
Containing 1 g / m ² or more and 9 g / m ² or less of Zn containing 1 g / m ² or more and 4 g / m ² or less of Si powder having a cumulative 99% particle size of 20 μm to 35 μm on a volume basis A mixed powder containing flux powder,
A binder, and
The ratio of the binder in the coating film is 5 to 40% by mass,
Tube for heat exchanger.   The tube main body contains Mn: 0.40 to 1.7% by mass, Si: 0.15% by mass or less, Cu: 0.10% by mass or less, and the balance is a chemical component composed of Al and inevitable impurities. The tube for heat exchangers according to claim 1, comprising:   The tube main body further contains one or more of Ti: 0.30% by mass or less, Sr: 0.10% by mass or less, Zr: 0.30% by mass or less, Item 3. A heat exchanger tube according to Item 2. The tube for heat exchangers according to any one of claims 1 to ₃ , wherein the compound constituting the Zn-containing flux powder is KZnF3. The heat exchanger tube according to any one of claims 1 to 4, wherein the mixed powder further contains 9 g / m ² or less of Zn-free flux powder made of a compound not containing Zn. .   The tube for a heat exchanger according to claim 5, wherein the compound constituting the Zn-free flux powder is a K-Al-F compound. It is a manufacturing method of the heat exchanger using the tube for heat exchangers of any one of Claims 1-6,
A plurality of the heat exchanger tubes are arranged in parallel via fins, the core in which the heat exchanger tubes and the fins are alternately stacked, and at both ends of the core in the longitudinal direction of the heat exchanger tubes Making an assembly with an arranged header;
A method of manufacturing a heat exchanger, wherein the assembly is heated to braze the heat exchanger tube and the fins, and a heat exchanger is produced by brazing the heat exchanger tube and the header. .

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