CN113453840A

CN113453840A - Brazing sheet for heat exchanger, joining structure of brazing sheet for heat exchanger, joining method of brazing sheet for heat exchanger, and heat exchanger

Info

Publication number: CN113453840A
Application number: CN202080015258.2A
Authority: CN
Inventors: 中岛孝仁; 广田正宣; 山本宪昭
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2019-10-11
Filing date: 2020-10-06
Publication date: 2021-09-28
Also published as: JP7660311B2; WO2021070793A1; JP2021063263A

Abstract

A brazing sheet (10) used for a heat exchanger comprises a core material (11) made of an aluminum alloy, a brazing material layer (12), and a zinc-containing sacrificial anode material layer (13), and has a joint surface (10a) constituting a joint (21) and a non-joint adjacent surface (10b) adjacent to the joint surface (10 a). The bonding surfaces (10a) are all sacrificial anode material layers (13). A fillet (22) is formed at a portion adjacent to the joint surface (10a) between the non-joint adjacent surfaces (10 b). The sacrificial anode material contains 0.5-6.0 mass% of lead and 3.0-11 mass% of silicon, the brazing material and the sacrificial anode material do not contain copper, and the core material contains 0.3-1.2 mass% of copper.

Description

Brazing sheet for heat exchanger, joining structure of brazing sheet for heat exchanger, joining method of brazing sheet for heat exchanger, and heat exchanger

Technical Field

The present invention relates to a brazing sheet used for components constituting a heat exchanger, a joining structure for joining the brazing sheets to each other, a joining method of the brazing sheet for a heat exchanger, and a heat exchanger having the joining structure.

Background

A general heat exchanger generally includes tubes and fins, and has a structure in which a plurality of fins are attached to the outer periphery of the tubes. Copper (Cu) or an alloy thereof (referred to as "copper material" for convenience) can be used as a material of the pipe, and in recent years, aluminum (Al) or an alloy thereof (aluminum material) is also used. As a material of the fins, an aluminum material is generally used.

In the manufacture of heat exchangers, joining by brazing material is generally used to attach fins to tubes. If both the tube and the fin are made of an aluminum material, for example, a brazing sheet is used in which a brazing material layer is coated (covered) on at least one surface of a core material made of an aluminum alloy. In view of the corrosion resistance of the tubes and fins, brazing sheets are used in which a core material is coated on one side with a brazing material and on the other side with a sacrificial anode material layer.

As the brazing material, an aluminum-silicon (Si) -based alloy used for brazing of an aluminum alloy is generally used, and as the sacrificial anode material, a material in which zinc (Zn) is added to an aluminum alloy is generally used in order to make the potential thereof relatively low. As a typical sacrificial anode material, a material in which zinc is added to a brazing material of a general aluminum-silicon alloy can be exemplified. Thereby, the sacrificial anode material can function as a brazing material.

As an example of the brazing sheet coated with the sacrificial anode material layer, for example, a brazing sheet disclosed in patent document 1 is known. Patent document 1 discloses an aluminum alloy brazing sheet used for a heat exchanger for an automobile, particularly for a passage constituent material of a fluid (cooling water, refrigerant, or the like), in which the composition of a core material and a sacrificial anode material is adjusted to achieve good brazeability, excellent strength after brazing, and corrosion resistance.

The brazing sheet is limited to a content of silicon, iron (Fe), and manganese (Mn) of 0.15 mass% or less in the sacrificial anode material. This is to suppress the generation of Al-Mn-Si compounds or Al-Fe-Mn-Si compounds and to suppress the strength reduction after brazing. In addition, the content of silicon in the core material of the brazing sheet is limited to 0.15 mass% or less, and copper is added in the range of 0.40-1.2 wt% in the core material. The reason why copper is added is that the potential difference with the sacrificial anode layer or the like is increased by increasing the potential of the core material to a high level in order to improve the strength of the core material, and the corrosion prevention effect by the sacrificial anode action is improved.

Another example of a brazing sheet coated with a sacrificial anode material layer is disclosed in patent document 2, for example. Patent document 2 also discloses an aluminum alloy brazing sheet used for a heat exchanger for an automobile, particularly for a fluid passage-constituting material. In this brazing sheet, the sacrificial corrosion prevention effect is exhibited on both surfaces, the brazing function is exhibited on one surface, and not only the core material and the sacrificial anode material but also the composition of the brazing material is adjusted in order to prevent preferential corrosion of the joint.

The brazing sheet is formed by adding zinc (Zn) to a sacrificial anode material and a brazing material, further adding copper to the brazing material in a range of 0.1-0.6 mass%, and adding copper to a core material in a range of 0.05-1.2 mass%. The purpose of adding copper to each material is different, and the brazing material is to increase the strength of the core material so that the potential of the brazing material becomes high.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2010-163674

Patent document 2: japanese patent laid-open publication No. 2013-155404

Disclosure of Invention

In the brazing sheet disclosed in patent document 1, the strength is improved and the corrosion prevention effect by the sacrificial anode action is improved by adding copper to the core material. However, in this brazing sheet, the content of silicon in both the sacrificial anode material and the core material is limited to 0.15 mass% or less, and the content of each metal element other than copper is specified in detail for the core material. Therefore, the range of selection of materials that can be used as the core material and the sacrificial anode material becomes small. Furthermore, in the brazing sheet, the silicon content of the sacrificial anode material is limited to a very small amount. Therefore, it is considered that the sacrificial anode material layer does not function as a general brazing material.

In the brazing sheet disclosed in patent document 2, by adding zinc and copper together to the brazing material, not only zinc but also copper is concentrated in the brazed joint portion. Here, by the concentration (inclusion) of copper, it is possible to prevent the potential of the junction from being excessively lowered by zinc. However, if copper and zinc are used in combination, the inventors have conducted extensive studies and have found that the preferential corrosion action of the sacrificial anode material layer is reduced, resulting in a reduction in corrosion resistance.

For example, depending on the type of heat exchanger, when joining the brazing sheets to each other, there is a structure in which the angle formed by the respective joining surfaces becomes an acute angle. For convenience, such a structure is referred to as an "acute angle joining structure" in which a brazing angle is formed between non-joining adjacent surfaces that form an acute angle with each other, and a surface that is adjacent to a joining surface of the brazing sheet but is not joined is referred to as a "non-joining adjacent surface". The fillet is defined as a portion where the brazing material or the sacrificial anode material flowing out from the joining surface is solidified at the time of joining.

In the case where copper and zinc are used in combination in a brazing material as described in patent document 2, copper segregates on the surface of the fillet after brazing. Since segregated copper functions as a cathode in the corrosion reaction, the corrosion priority of the sacrificial anode layer existing in the periphery of segregated copper is lowered, and the corrosion resistance is lowered. Further, the potential of the sacrificial anode layer existing in the periphery of copper segregated on the surface of the brazing corner becomes expensive. This reduces the potential difference between the sacrificial anode layer and the core material, and therefore, the function (preferential etching action) of the sacrificial anode layer is also reduced. Depending on the situation, there is also a risk that penetration occurs early due to grain boundary corrosion of the core material.

The present invention provides a brazing sheet which can effectively suppress or prevent preferential corrosion of a brazing corner even when copper and zinc are contained in the brazing corner formed adjacent to a joint portion between brazing sheets, and which can improve corrosion resistance of a heat exchanger.

The brazing sheet of the present invention is a brazing sheet used in a heat exchanger, comprising: a core material made of an aluminum alloy; a brazing material layer covering one surface of the core material and made of a brazing material of an aluminum alloy containing silicon (Si); and a sacrificial anode material layer covering the other surface of the core material and made of a sacrificial anode material of an aluminum alloy containing zinc (Zn) in a range of 0.5 to 6.0 mass% and silicon (Si) in a range of 3.0 to 11 mass%. The brazing sheet has a joint surface and non-joint adjacent surfaces adjacent to the joint surface, the joint surface is a sacrificial anode material layer, when the joint surfaces are jointed, a brazing horn in which the sacrificial anode material flows out from the joint surface and is solidified is formed at a position adjacent to the joint surface between the non-joint adjacent surfaces, the brazing sheet and the sacrificial anode material do not contain copper (Cu), and the core material contains copper (Cu) in the range of 0.3-1.2 mass%.

Alternatively, the brazing sheet of the present invention is a brazing sheet for a heat exchanger, comprising: the anode plate comprises a core material made of an aluminum alloy and a sacrificial anode material layer, wherein the sacrificial anode material layer covers two surfaces of the core material and is composed of an aluminum alloy sacrificial anode material containing zinc (Zn) in the range of 0.5-6.0 mass% and silicon (Si) in the range of 3.0-11 mass%. The brazing sheet has a joint surface and non-joint adjacent surfaces adjacent to the joint surface, the joint surface is a sacrificial anode material layer, when the joint surfaces are jointed, a brazing horn formed by the sacrificial anode material flowing out from the joint surface and solidifying is formed at the position adjacent to the joint surface between the non-joint adjacent surfaces, the sacrificial anode material does not contain copper (Cu), and the core material contains copper (Cu) in the range of 0.3-1.2 mass%.

The bonding structure of the brazing sheet of the present invention is constituted as follows: a member for constituting a heat exchanger is a joint structure formed by joining together brazing sheets each having at least one surface of a core material made of an aluminum alloy covered with a sacrificial anode material layer made of a sacrificial anode material, each of the brazing sheets having a joining surface and a non-joining adjacent surface adjacent to the joining surface, each of the joining surfaces being the sacrificial anode material layer, and having a fillet formed by the sacrificial anode material flowing out from the joining surface and solidified at a portion adjacent to the joining surface between the non-joining adjacent surfaces, the fillet having a concentration exceeding that of the core material and the sacrificial anode material layer and containing copper (Cu) at 2.0 mass% or less.

According to the above configuration, in the brazing sheet covered with the brazing material layer and the sacrificial anode material layer or the brazing sheet covered with only the sacrificial anode material layer, only the core material contains copper within a predetermined range, and each layer other than the core material contains substantially no copper. Thus, when the sacrificial anode material layers of the brazing sheet are joined to each other, copper is not segregated as in the prior art but is diffused concentratedly to the fillet formed adjacent to the joined portion so as to have an appropriate concentration, and copper is not substantially diffused to the sacrificial anode material layers other than the fillet.

Thus, excessive degradation of the potential by concentrated zinc is mitigated or counteracted by diffused copper at the bit angle. Thus, a good sacrificial anode effect at the drill angle can be achieved. Further, since copper hardly diffuses into the sacrificial anode material layer other than the brazing corner, copper can be made to exhibit a favorable sacrificial anode action without inhibiting the potential due to zinc to a moderate extent.

As a result, it is possible to avoid the risk of the corrosion-prioritizing action of the sacrificial anode layer existing in the periphery due to the segregation of copper as in the conventional technique being lowered, and it is possible to effectively suppress or prevent the progress of corrosion from the brazing corner to the joint portion, which leads to the lowering of the joint strength of the joint portion. This makes it possible to improve the corrosion resistance of the joint of the heat exchanger.

The present invention also includes a heat exchanger having a joined structure of the brazing sheets of the above-described structure.

Drawings

Fig. 1A is a schematic cross-sectional view showing a schematic structure of a brazing sheet according to a representative embodiment of the present invention.

Fig. 1B is a schematic cross-sectional view showing a schematic structure of a bonding structure of a solder sheet according to a representative embodiment of the present invention.

Fig. 2A is a schematic cross-sectional view showing an example of a header of a plate-fin stacked heat exchanger configured by using the brazing sheet shown in fig. 1A.

Fig. 2B is an enlarged schematic partial sectional view of the joint structure of the brazing sheet of the header shown in fig. 2A.

Fig. 3A is a schematic partial cross-sectional view showing an example of a Parallel Flow Condenser (PFC) configured with the brazing sheet shown in fig. 1A.

Fig. 3B is an enlarged schematic partial sectional view of the bonding structure of the solder sheet of the PFC shown in fig. 3A.

Fig. 4A is a schematic cross-sectional view showing an example of a header of a plate fin stacked heat exchanger configured by using brazing sheets having sacrificial anode material layers on both surfaces.

Fig. 4B is an enlarged schematic partial sectional view of the joint structure of the brazing sheet of the header shown in fig. 4A.

Fig. 5 is a view showing a cross-sectional photograph of a bonding structure of a solder sheet as a representative example of the present invention and a graph of a line analysis result by an Electron Probe Microanalyzer (EPMA) in the bonding structure.

Fig. 6 is a graph showing a cross-sectional photograph of a bonding structure of a brazing sheet as a comparative example of the present invention and a line analysis result of EPMA in the bonding structure.

Fig. 7A is a graph showing the results of a corrosion resistance test of the joined structure of the brazing sheets of example 1.

Fig. 7B is a graph showing the results of a corrosion resistance test of the joined structure of the brazing sheets of the comparative example.

Fig. 8 is a graph showing a comparison between the copper concentration contained in the core material of the brazing sheet of the present invention and the copper concentration contained in the joint portion.

Fig. 9 is a graph showing the results of a corrosion resistance test of the joined structure of the brazing sheets of example 2.

Detailed Description

The brazing sheet may be configured as follows: the core material is a core material obtained by adding copper in the aforementioned range to any of 3000 series, 5000 series, or 6000 series aluminum alloys, and the sacrificial anode material layer is a material layer obtained by adding zinc in the aforementioned range to a 4000 series aluminum alloy.

In the brazing sheet, a structure in which the brazing material layer is a 4000 series aluminum alloy may be adopted.

In the brazing sheet, when the joining surfaces are joined to each other, an angle formed by the respective non-joining adjacent surfaces may be acute.

In the bonding structure of the brazing sheet, the following configuration may be adopted: the sacrificial anode material is an aluminum alloy containing 0.5-6.0 mass% of zinc (Zn) and 3.0-11 mass% of silicon (Si), the core material before bonding contains 0.3-1.2 mass% of copper (Cu), and the sacrificial anode material before bonding contains no copper.

In the bonding structure of the brazing sheet, the following configuration may be adopted: in the case where only one face of the core material is covered with a layer of sacrificial anode material, the other face is covered with a layer of brazing material composed of a brazing material.

In the bonding structure of the brazing sheet, the following configuration may be adopted: the brazing material is an aluminum alloy containing silicon (Si), and the brazing material before joining does not contain copper.

In the bonding structure of the brazing sheet, the following configuration may be adopted: the fillet contains zinc (Zn), and the concentration of copper (Cu) in the fillet is higher than the concentration of zinc.

In the bonding structure of the brazing sheet, the following configuration may be adopted: the angle formed by each non-joining adjacent surface is acute.

The heat exchanger of the present invention has the above-described joining structure of the brazing sheet. Specifically, for example, a plate fin stacked heat exchanger or a Parallel Flow Condenser (PFC) can be cited.

Hereinafter, a representative embodiment of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements in all the drawings are denoted by the same reference numerals, and redundant description thereof will be omitted.

[ brazing sheet ]

The brazing sheet of the present invention is made of an aluminum alloy used in a heat exchanger. Specifically, for example, as shown in fig. 1A, the brazing sheet 10 of the present invention includes a core material 11, a brazing material layer 12, and a sacrificial anode material layer 13. The brazing material layer 12 covers one surface (cladding) of the core material 11, and the sacrificial anode material layer 13 covers the other surface of the core material 11, that is, the surface opposite to the surface covered with the brazing material layer 12. The brazing material constituting the core material 11, the brazing material layer 12, and the sacrificial anode material constituting the sacrificial anode material layer 13 are all aluminum alloys.

Alternatively, although not shown, the brazing sheet 10 of the present invention may have a structure including the core material 11 and the sacrificial anode material layer 13, but not including the brazing material layer 12. In the brazing sheet 10, the sacrificial anode material layers 13 are formed on both surfaces of the core material 11.

The brazing sheet 10 of the present invention has a joint surface at least on the sacrificial anode material layer 13 side, and a joint portion is formed by joining the joint surfaces to each other. The structure in which the brazing sheets 10 are joined to each other through the joining surface is the joining structure of the brazing sheets 10 of the present invention. The brazing sheet 10 of the present invention has a non-joining adjacent surface adjacent to the joining surface. When the brazing sheets 10 are joined to each other to form a joined structure, the angle formed by the respective non-joining adjacent surfaces becomes an acute angle.

Specifically, for example, as shown in fig. 1B, the joining structure 20 of the brazing sheet 10 of the present invention is configured such that the joining surfaces 10a of the brazing sheet 10 are joined to each other, and the angle θ 1 formed by the non-joining adjacent surfaces 10B adjacent to the joining surfaces 10a is not particularly limited, but may be an acute angle, i.e., an angle smaller than 90 ° (θ 1 < 90 °). For convenience of description, the angle θ 1 formed by the non-joining adjacent surfaces 10B of the joining structure 20 constituting the brazing sheet is referred to as an "adjacent surface forming angle" and is indicated by a broken line in fig. 1B.

As described above, the preferable range of the adjacent surface forming angle θ 1 is not particularly limited as long as it is an acute angle, that is, a smaller angle than a right angle (smaller than 90 degrees), but may be, for example, in the range of 40 to 80 degrees (40 DEG. ltoreq. θ 1. ltoreq.80 degrees) or in the range of 50 to 70 degrees (50 DEG. ltoreq. θ 1. ltoreq.70 degrees) depending on various conditions such as the type of heat exchanger and the structure of the heat exchanger using the brazing sheet 10. Alternatively, for example, the lower limit may be 15 ° or more (15 ° ≦ θ 1), or may be 20 ° or more (20 ° ≦ θ 1).

In the brazing sheet joining structure 20 of the present invention, when the joining portions 21 are formed by joining the brazing sheets 10 to each other, as shown in fig. 1B, a fillet 22 is formed between the non-joining adjacent surfaces 10B. The heat exchanger includes a member or a structure that forms the brazing angle 22, and the non-joining adjacent surfaces 10b often form an acute angle therebetween. The fillet 22 is defined as a structure in which the brazing material (or the sacrificial anode material) flowing out from the joint surface 10a is solidified at the time of joining.

In the present invention, in the heat exchanger using the brazing sheet 10, the preferential corrosion of the brazing corner 22 can be effectively suppressed or avoided. If the angle θ 1 between adjacent planes is too large, for example, 180 ° or close to horizontal, it is structurally difficult to form the brazing angle 22. If the angle θ 1 between adjacent planes is too small, the adjacent planes 10b are not joined and are parallel to each other, and thus the brazing angle 22 is difficult to form, depending on the structure of the heat exchanger. Accordingly, a preferable example of the adjacent surface forming angle θ 1 is an angle within the range of the upper limit value and the lower limit value or an angle equal to or larger than the lower limit value.

In the brazing sheet 10 of the present invention, the bonding surface 10a may be set at least on the sacrificial anode material layer 13. Therefore, as described later, the sacrificial anode material doubles as a brazing material. That is, the sacrificial anode material layer 13 contributes to the joining of the brazing sheets 10 to each other as a brazing material at the time of joining, and contributes to the corrosion prevention effect of the brazing sheets 10 as a sacrificial anode material after joining.

In the brazing sheet 10 of the present invention, a non-joint adjacent surface 10b is set adjacent to the joint surface 10 a. Therefore, the non-bonding adjacent surface 10b is also the sacrificial anode material layer 13, similarly to the bonding surface 10 a. As described above, the angle (the adjacent faces forming the angle θ 1) formed by the non-joining adjacent faces 10b when joining the brazing sheets 10 to each other is, for example, an acute angle. As such, for example, as shown in fig. 1B, the non-joining adjacent surface 10B may be inclined with respect to the joining surface 10 a.

In the example shown in fig. 1B, the non-joining-adjacent surface 10B is inclined at an angle θ 2 with respect to the joining surface 10 a. Therefore, as long as the joint surfaces 10a are joined to each other to form the joint portion 21, the non-joined adjacent surfaces 10b adjacent to the respective joint surfaces 10a form an acute angle θ 1 with each other, that is, adjacent surfaces. For convenience of explanation, the inclination angle θ 2 of the non-joining adjacent surface 10B with respect to the joining surface 10a is referred to as "adjacent surface inclination angle", and is indicated by a broken line together with the extension line of the joining surface 10a in fig. 1B.

The specific angle of the adjacent surface inclination angle θ 2 is not particularly limited, but for example, as shown in fig. 1B, as long as the shapes of the mutually joined brazing sheets 10 are line-symmetrical with respect to the joining surface 10a, the adjacent surface inclination angle θ 1 is 2 times the adjacent surface inclination angle θ 2(θ 1 — θ 2 × 2). Therefore, if the angle θ 1 between the adjacent planes is an acute angle, the inclination angle θ 2 between the adjacent planes may be smaller than 45 °. However, the shape of the brazing sheet 10 is not necessarily line-symmetrical, and the brazing sheets 10 of various shapes may be joined to each other at the joining surface 10a depending on various conditions such as the type of heat exchanger and the structure of the heat exchanger. Furthermore, the adjacent face angle θ 1 need not be acute. Therefore, the adjacent surface inclination angle θ 2 is not limited to less than 45 °.

For example, the joining structure 20 may be joined in a state where the brazing sheet 10 having a different shape is inclined with respect to the joining surface 10a of the substantially flat brazing sheet 10. In this case, the non-joining adjacent surfaces 10b of the substantially flat brazing sheets 10 are set as different regions on the sacrificial anode material layer 13 without being inclined with respect to the joining surface 10 a. Therefore, the adjacent surface inclination angle θ 2 may be 0 ° (θ 2 ═ 0 °). That is, the non-joining adjacent surface 10b may be a different region of a continuous flat surface that is not inclined with respect to the joining surface 10a (refer to a joining structure of a parallel flow condenser described later).

In the joined structure 20 of the brazing sheet 10 of the present invention, there is a possibility that corrosion proceeds in the directions indicated by the solid arrows C1 and C2 in fig. 1B. The direction of the solid arrow C1 is the etching direction proceeding from the direction of the non-joining adjacent surface 10b with respect to the core material 11. The direction of the solid arrow C2 is the direction of corrosion in the joint portion 21 including the fillet 22, which proceeds in the direction of the joint surface 10 a.

However, corrosion in the corrosion direction C1 is suppressed (avoided or prevented) by the sacrificial anode action by the sacrificial anode material layer 13, and corrosion in the corrosion direction C2 may proceed by concentrating zinc in the fillet 22, and the potential of the joint 21 including the fillet 22 may become too low. In the brazing sheet 10 of the present invention, the core material 11 contains copper within a predetermined range, and the brazing material layer 12 and the sacrificial anode material layer 13 are substantially free of copper, whereby corrosion in the corrosion direction C2 can be effectively suppressed (avoided or prevented).

[ Material of brazing sheet ]

As described above, the brazing sheet 10 of the present invention is made of an aluminum alloy, and the core material 11, the brazing material, and the sacrificial anode material are all made of an aluminum alloy. Specifically, the core material 11 may be made of a known aluminum alloy that can achieve desired physical properties depending on various conditions such as the type and structure of the heat exchanger, and in the present invention, copper (Cu) is added (contained) in a range of 0.3 to 1.2 mass%.

As the aluminum alloy used as the core material 11, for example, in the field of heat exchangers, 3000 series (aluminum-manganese (Al-Mn) based alloy), 5000 series (aluminum-magnesium (Al-Mg) based alloy), 6000 series (aluminum-magnesium-silicon (Al-Mg-Si) based alloy) and the like can be representatively exemplified, but not limited thereto. In the present invention, a material obtained by adding Cu to an aluminum alloy or another aluminum alloy by a known method so as to fall within the above range may be used as the core material 11.

For convenience, when the aluminum alloy before Cu is added is used as the "base material", Cu may be contained as an inevitable impurity in the base material. Cu is contained as an inevitable impurity, and the concentration thereof may be, for example, 0.2 mass% or less. However, an aluminum alloy such as a 2000-based alloy, which contains Cu in advance at a concentration exceeding 1.2 mass%, cannot be used as the base material of the core material 11.

In the brazing sheet 10 of the present invention, if the content (concentration) of Cu in the core material 11 is less than 0.3 mass%, as described later, there is a fear that Cu cannot diffuse from the core material 11 to the fillet 22 at a sufficient concentration. If the Cu content in the core material 11 exceeds 1.2 mass%, the strength of the sacrificial anode action of the sacrificial anode material may affect the Cu content, but the grain boundary corrosion of the core material 11 is highly sensitive, and the progress of corrosion may not be effectively suppressed.

The Cu content in the core material 11 may be in the range of 0.3 to 1.2 mass%, but a preferable example thereof is in the range of 0.3 to 0.7 mass%. That is, the upper limit of the Cu content may be 1.2 mass% or less, but may be 0.7 mass% or less depending on various conditions. When the Cu content is 0.7 mass% or less, the grain boundary corrosion susceptibility of core material 11 can be effectively suppressed from increasing even when the sacrificial anode action of the sacrificial anode material is relatively weak.

In the present invention, the aluminum alloy used as the brazing material may be an alloy containing Silicon (Si), that is, an aluminum-Silicon (Al-Si) alloy. The Si content (concentration) in the brazing material is not particularly limited, and may be within a range that can be suitably used as a brazing material. Specifically, the content of Si in the brazing material may be, for example, in the range of 2.5 to 13 mass%, or 3.5 to 12 mass%. If the Si content is too low, the Al — Si alloy may not function sufficiently as a brazing material. On the other hand, if the Si content is too high, Si may diffuse into the core material 11 or the target material and melt the brazing sheet 10 itself.

The Al — Si alloy as the brazing material may contain an element other than Si in a range that does not affect the function as the brazing material. In addition, the Al — Si-based alloy as the brazing material may contain various elements as inevitable impurities. However, the Al — Si based alloy as the brazing material does not substantially contain Cu. Substantially free of Cu means that Cu is not contained in a concentration exceeding unavoidable impurities. The upper limit of the allowable concentration of the inevitable impurities varies depending on various conditions, but is generally less than 0.1 mass% of the total Al — Si alloy.

In order to exhibit the sacrificial anode function, an aluminum alloy used as a sacrificial anode material contains zinc (Zn) in an amount of 0.5 to 6.0 mass%. In the present invention, as described above, the sacrificial anode material also serves as the brazing material, and therefore contains Si in the same manner as the brazing material. The sacrificial anode material may contain Si in an amount of 3.0 to 11 mass%. Therefore, the aluminum alloy used as the sacrificial anode material may be an aluminum-silicon-zinc (Al-Si-Zn) alloy.

In the Al-Si-Zn alloy as the sacrificial anode material, if the Zn content (concentration) is less than 0.5 mass%, the good sacrificial anode effect cannot be exhibited. On the other hand, if the Zn content exceeds 6.0 mass%, there is a fear that the sacrificial anode function is exerted too early, the sacrificial anode material layer 13 disappears from the brazing sheet 10 early, and the corrosion resistance of the brazing sheet 10 is lowered.

In addition, if the content of Si in the Al — Si — Zn alloy as the sacrificial anode material is too small or too large, it cannot be suitably used as a brazing material as described above. In particular, in the present invention, when the Si content is in the range of 3.0 to 11 mass%, the function as a brazing material can be favorably imparted to the sacrificial anode material layer 13 without substantially affecting the sacrificial anode action.

In addition, the Al — Si — Zn alloy as the sacrificial anode material may contain elements other than Si and Zn within a range that does not affect the function as the sacrificial anode or the function of the brazing material. Further, the Al — Si — Zn alloy as the sacrificial anode material may contain various elements as inevitable impurities. However, the Al-Si-Zn alloy as the sacrificial anode material does not substantially contain Cu. Substantially no Cu means: like the Al — Si-based alloy as the brazing material, Cu containing a concentration exceeding the concentration of the inevitable impurities may be generally less than 0.1 mass% of the total Al — Si — Zn-based alloy. Alternatively, the upper limit of the concentration of the inevitable impurities may be based on the alloy composition defined in a known standard such as JIS.

Specifically, the type of aluminum alloy used as the brazing material and the sacrificial anode material is not particularly limited, and as a representative example, 4000 series (aluminum-silicon (Al-Si) alloy) can be used. In the sacrificial anode material, an alloy obtained by adding Zn to a 4000-series aluminum alloy by a known method so that the content thereof is in the range of 0.5 to 6.0 mass% may be used.

In the brazing sheet 10 of the present invention, the coating rate of the brazing material and the sacrificial anode material is not particularly limited, and can be in a normal range. The normal coating rate may be, for example, in the range of 2 to 30 mass%, or in the range of 3 to 20 mass%. The thickness of the brazing sheet 10 and the thicknesses of the core material 11, the brazing material layer 12, and the sacrificial anode material layer 13 are not particularly limited, and may be appropriately set according to the structure of the brazing sheet 10, the type of heat exchanger to be manufactured, the components, and the like.

In the present invention, a plurality of the brazing sheets 10 are overlapped with each other at the joint surface 10a, and the brazing material and the sacrificial anode material are melted and welded at a high temperature (580 ℃ or higher) to join the brazing sheets 10 to each other. In the joined structure 20 of the brazing sheet 10 manufactured in this way, as shown in fig. 1B, the sacrificial anode material flowing out of the sacrificial anode material layer 13 of the joining surface 10a is solidified to form a fillet 22 at a portion adjacent to the joining surface 10a (joining portion 21) between the non-joining adjacent surfaces 10B.

The fillet 22 is formed of the sacrificial anode material flowing out from the joint surface 10a, and contains Zn, but also contains Cu diffused from the core material 11. The Cu concentration in the fillet 22 (joint 21) exceeds the concentrations of the core material 11, the brazing material layer 12, and the sacrificial anode material layer 13, and Cu substantially exhibits a concentration distribution such that Cu locally exists in the fillet 22. As is apparent from the results of examples and comparative examples described below, when the Cu concentration in the core material 11 is within a predetermined range and the brazing material layer 12 and the sacrificial anode material layer 13 do not substantially contain Cu, Cu exhibits a behavior of locally and intensively diffusing from the core material 11 toward the fillet 22 (joint portion 21) at the time of joining at a high temperature.

In the process of melting the sacrificial anode material (brazing material) from the sacrificial anode material layer 13 to form the fillet 22, Zn acts to diffuse into the joint portion 21 (fillet 22). Therefore, the Zn concentration of the fillet 22 is highest at the joint portion 21, but Zn remains in the sacrificial anode material layer 13. Therefore, in a cross section in the thickness direction of the joint 21 including the fillet 22, the Zn concentration exhibits a parabolic distribution having the fillet 22 as the maximum value (see the example and the comparative example described later). On the other hand, Cu does not exhibit such behavior as Zn and tends to diffuse so as to be locally concentrated with the formation of the fillet 22, and it is not confirmed whether Cu is significantly smaller than Zn in both the sacrificial anode material layer 13 and the core material 11 (see examples described later).

In the joint structure 20 of the brazing sheet 10 of the present invention, the Cu concentration and the Zn concentration in the fillet 22 are not particularly limited, but the Cu concentration may be 2.0 mass% or less, and the Zn concentration may be smaller than the Cu concentration. If the Cu concentration in the fillet 22 exceeds 2.0 mass%, the aging precipitation of the Cu-containing intermediate compound phase occurs in a short time compared with the life of the heat exchanger. Since such precipitates function as a cathode in the corrosion reaction, there is a concern that the corrosion current density in the fillet 22 increases, and the corrosion resistance around the fillet 22 is greatly deteriorated.

As described later, a proportional relationship can be observed between the Cu concentration of core material 11 (initial Cu concentration) and the Cu concentration of joint portion 21 (fillet 22) in joint structure 20 of brazing sheet. Therefore, it is considered that when the Cu concentration of core material 11 is 1.2 mass% or less, the Cu concentration of fillet 22 is 2.0 mass% or less. On the other hand, the Cu concentration of the core material 11 may be 0.3 mass% or more, but it is considered that the Cu concentration of the fillet 22 in the bonding structure 20 of the brazing sheet at this time is 0.5 mass% or more. Therefore, the lower limit of the Cu concentration of the fillet 22 in the bonded structure 20 of the brazing sheet may be equal to or higher than the Zn concentration, but is preferably equal to or higher than 0.5 mass%.

As described above, in the conventional brazing sheet disclosed in patent document 2, Cu is contained in the range of 0.05 to 1.2 mass% in the core material, but the brazing material is contained in the range of 0.1 to 0.6 mass% in the brazing sheet. Therefore, in the brazing sheet disclosed in patent document 2, it is considered that Cu does not act so as to locally concentrate from the core material toward the fillet at the time of joining at a high temperature as in the present invention.

In the present invention, it is considered that Cu is concentrated on the fillet 22 in the process in which Cu of the core material 11 diffuses into the sacrificial anode material due to high heat at the time of bonding, and the molten sacrificial anode material (functioning as a brazing material) flows into the bonding portion 21 to form the fillet 22. By Cu being concentrated on the fillet 22 in this manner, the potential of the joint 21 around the fillet 22 is higher than that around. However, according to the present invention, the potential of the joint portion 21 is not excessively increased by Cu as in the case of the conventional brazing sheet, and the lowering of the sacrificial anode action by Zn can be suppressed or avoided. As a result, the corrosion resistance of the joint portion 21 including the brazing corner 22 can be prevented or avoided from being lowered, and the corrosion resistance life of the heat exchanger having the joint structure 20 of the brazing sheet can be improved.

In addition, Cu remains in core 11 except for joint portion 21. Since the core material 11 contains Cu in a predetermined range, the potential of the core material 11 is increased, and thus the potential difference with the sacrificial anode material layer 13 can be enlarged. This makes it possible to more satisfactorily exhibit the sacrificial anode function of the sacrificial anode material layer 13. Further, by adding Cu to the core material 11, the strength of the core material 11 can be improved. Therefore, it is advantageously possible to facilitate the thinning of the brazing sheet 10 and to improve the pressure resistance of the heat exchanger.

In addition, as a method for suppressing or avoiding the preferential corrosion of the joint portion without containing Cu, it is conceivable to shield the joint portion from the surrounding by coating or partially removing the sacrificial anode material layer. However, in such a method, since a step of applying or partially removing the sacrificial anode material layer is required, there are problems such as an increase in production cost, complexity and complication of the whole production process, and peeling and scattering of the coating film during application. In contrast, in the present invention, Cu can be appropriately concentrated in the fillet 22 only by bonding the core material 11 containing Cu, and therefore, the manufacturing can be easily performed without an additional process.

Note that the method for evaluating the potential of the joint 21 including the fillet 22, the sacrificial anode material layer 13, and the like is not particularly limited, and a known method can be appropriately used. A typical method is a method in which a sample for measuring potential (for example, a solder sheet 10, or a core material 11, a solder material, a sacrificial anode material, a fillet 22, a joint 21, or an alloy simulating the composition thereof) is connected to a potentiostat/galvanostat, a counter electrode, and a reference electrode (for example, a silver/silver chloride (Ag/AgCl) electrode) are immersed in an electrolyte (for example, a 5 wt% sodium chloride (NaCl) solution), and the potential difference between the sample and the reference electrode is measured.

The method for producing the brazing sheet 10 of the present invention is not particularly limited, and a known production method can be suitably used. Specifically, for example, an aluminum alloy containing Cu in a range of 0.3 to 1.2 mass% may be formed into a plate shape by a known method to form the core 11, one surface of the core 11 may be coated with a brazing material of an aluminum alloy containing Si by a known method, and the other surface of the core 11 may be coated with a sacrificial anode material of an aluminum alloy containing Zn in a range of 0.5 to 6.0 mass% and Si in a range of 3.0 to 11 mass% by a known method. In the present invention, various conditions in the manufacture of the brazing sheet 10 can be set as appropriate depending on the structure of the brazing sheet 10, the type of heat exchanger to be manufactured, the components, and the like.

[ joining Structure of brazing sheet and Heat exchanger ]

As previously mentioned, the brazing sheet 10 of the present invention can be suitably used in particular in the manufacture of heat exchangers. As described above, the joining structure 20 of the brazing sheet formed when the brazing sheet 10 of the present invention is applied to a heat exchanger has a structure as illustrated in fig. 1B. More specifically, examples of the heat exchanger include a plate fin stacked heat exchanger having a structure as shown in fig. 2A and 2B, a Parallel Flow Condenser (PFC) having a structure as shown in fig. 3A and 3B, and a stacked heat exchanger for an Air To Water heat pump having a structure as shown in fig. 4A and 4B.

Although not shown, the plate-fin stacked heat exchanger is configured such that, in a plate-fin stacked body having a flow path through which a refrigerant as a 1 st fluid flows, air as a first fluid flows between the respective plate-fin stacked bodies, and heat is exchanged between the 1 st fluid and a 2 nd fluid. The heat exchanger has plate fins comprising: a flow path region having a plurality of 1 st fluid flow paths in which the 1 st fluid flows in parallel; and a header region having a header flow path communicating with each of the 1 st fluid flow paths in the flow path region.

In the plate-fin stacked heat exchanger, end plates having substantially the same shape as the plate fins in plan view are provided on both sides in the stacking direction of the plate-fin stacked body, and the pair of end plates and the plurality of plate fins interposed therebetween are joined and integrated by brazing in a stacked state. Fig. 2A shows a schematic structure of a header portion of the plate fin laminate 30 as a partial cross section, and a plurality of plate fins 32 are laminated on an end plate 31 positioned at the uppermost portion in the drawing.

The end plate 31 and the plate fins 32 are provided with openings, respectively, and the plate fin laminated body 30 is formed by laminating these plates, thereby forming the header openings 33. In the structure shown in fig. 2A, the refrigerant as the 1 st fluid flows in from the outside of the header opening 33 in the direction indicated by the solid arrow in the drawing, and further flows into between the plate fins 32. Since the 1 st fluid flow path is provided in each plate fin 32 as described above, the refrigerant flowing between the plate fins 32 flows through the 1 st fluid flow path. In addition, air as the 2 nd fluid flows so as to intersect the flow direction of the refrigerant (the direction of the 1 st fluid flow path) in the space formed between the plate fins 32. Thereby, the air is cooled by the refrigerant.

Fig. 2B is a partially enlarged view of the plate-fin stacked body 30 shown in fig. 2A, schematically showing an example of the joining structure 20 of the brazing sheet 10 of the present invention. In the example shown in fig. 2A and 2B, the plate fin 32 is the brazing sheet 10 of the present invention, and the joining structure 20 of the brazing sheet of the present invention is the joining portion 21 located on the header opening 33 side. In fig. 2B, the sacrificial anode material layer 13 is shown emphasized by hatching and the brazing angle 22 is also shown emphasized by hatching with respect to the plate fin 32 as the brazing sheet 10.

In the joint portion 21 on the header opening 33 side, the joint surfaces 10a of the plate fins 32 are joined to each other, and the brazing angle 22 is formed between the non-joint adjacent surfaces 10b adjacent to the joint surfaces 10 a. In the present invention, the core material 11 of the plate fin 32 contains Cu in the range of 0.3 to 1.2 mass%, and the brazing material layer 12 and the sacrificial anode material layer 13 of the plate fin 32 do not substantially contain Cu. Therefore, the fillet 22 has a concentration exceeding the concentration of the core material 11, the brazing material layer 12, and the sacrificial anode material layer 13, and contains 2.0 mass% or less of Cu. This can favorably suppress (avoid or prevent) preferential corrosion of the joint portion 21, and therefore can improve the corrosion-resistant life of the plate-fin stacked heat exchanger.

Specific examples of such a plate-fin stacked heat exchanger are disclosed in, for example, japanese patent laid-open nos. 2017-180856, 2018-066531, 2018-066532, 2018-066533, 2018-066534, 2018-066535, 2018-066536, and the contents of these publications are incorporated herein by reference.

In the joining structure 20 of the brazing sheet shown in fig. 2B, the plate fin 32 as the brazing sheet 10 has a bent portion having a 2-step level. That is, the non-joining adjacent surface 10b is inclined with respect to the joining surface 10a on the right side in the drawing so as to form an adjacent surface inclination angle θ 2 of an acute angle, and further, a non-joining surface parallel to the joining surface 10a exists on the left side of the non-joining adjacent surface 10 b. However, the specific shape of the brazing sheet 10 is not limited to the shape having the bent portion with the 2-step, and may be a flat shape without the bent portion, may be a shape having the bent portion with the 1-step schematically shown in fig. 1B, may be a shape having the bent portion with the 3-step or more, or may be a shape having another three-dimensional structure such as a bent portion. The specific shape of the brazing sheet 10 is appropriately set according to various conditions such as the type and structure of the heat exchanger.

A Parallel Flow Condenser (PFC) is a heat exchanger widely used in an automobile air conditioner (air conditioner for an automobile), and has a plurality of flat tubes disposed between a pair of headers and corrugated fins for heat dissipation disposed between the flat tubes. These headers, flat tubes, corrugated fins, and the like are joined by brazing. Fig. 3A shows a schematic structure of a connection portion between the header 41 and the flat tubes 42 in the PFC40 as a partial cross section. Corrugated fins 43 are provided between the flat tubes 42 and they are also joined by brazing, and the joining structure 20 of brazing sheet of the present invention is a joint portion between the header 41 and the flat tubes 42 as shown in an enlarged view of fig. 3B.

In the example shown in fig. 3B, the header 41 and the flat tubes 42 are both the brazing sheet 10, and the sacrificial anode material layer 13 is shown with hatching in emphasis with respect to the header 41 and the flat tubes 42. The angle 22 is also shown with a hatching. Since the sacrificial anode material layer 13 of the flat tube 42 is flat, it is set as a different region in a single surface (surface of the sacrificial anode material layer 13) where the joint surface 10a is continuous with the non-joint adjacent surface 10 b. Therefore, the flat tube 42 is a flat tube having no bent portion as the brazing sheet 10.

The header 41 has an opening portion through which the flat tube 42 is inserted, and the joint surface 10a and the non-joint adjacent surface 10b are provided in the opening portion. In fig. 3B, the joint surfaces 10a of the header 41 are illustrated as surfaces parallel to the joint surfaces 10a (outer surfaces) of the flat tubes 42, but the present invention is not limited thereto, and surfaces that are not parallel to the outer surfaces of the flat tubes 42 may be used. The opening of the header 41 is a tube having a shape with a single bent portion as the brazing sheet 10.

In the brazing sheet joining structure 20 shown in fig. 3B, a brazing angle 22 is formed between a non-joining adjacent surface 10B adjacent to the joining surface 10a of the header 41 and a non-joining adjacent surface 10B adjacent to the joining surface 10a of the flat tubes 42. In the present invention, the core material 11 of the header 41 and the flat tubes 42 contains Cu in the range of 0.3 to 1.2 mass%, and the brazing material layer 12 and the sacrificial anode material layer 13 of the header 41 and the flat tubes 42 do not substantially contain Cu. Therefore, the fillet 22 has a concentration exceeding the concentration of the core material 11, the brazing material layer 12, and the sacrificial anode material layer 13, and contains 2.0 mass% or less of Cu. This can favorably suppress (avoid or prevent) preferential corrosion of the joint portion 21, and therefore can improve the corrosion-resistant life of the plate-fin stacked heat exchanger.

The method of manufacturing the joining structure 20 of the brazing sheet 10 is not limited to this, and a known brazing method or the like can be appropriately used. For example, a method of applying a known flux to the bonding surface 10a of the brazing sheet 10 and then heating the same in a nitrogen atmosphere furnace at a temperature of, for example, about 600 ℃. In particular, in the joined structure 20 of the brazing sheet of the present invention, the Cu content in the fillet 22 (and the joint portion 21) is not substantially affected by the detailed joining conditions.

As shown in fig. 4A, the basic structure of the plate fin laminate 34 constituting the laminated heat exchanger for Air To Water heat pumps is the same as that of the plate fin laminate 30 of a general plate fin laminated heat exchanger. However, as shown in fig. 4B, the plate fins 35 (the brazing sheet 10 of the present invention) constituting the plate-fin laminated body 34 have a structure in which the sacrificial anode material layers 13 are provided on both surfaces thereof. Therefore, as shown in fig. 4A and 4B, the brazing angle 22 is formed not only at the joint portion 21 located on the header opening 33 side (inner side) but also at the joint portion 21 located on the opposite side (outer side) to the header opening 33 side.

In the present invention, the core material 11 of the plate fin 35 contains Cu in the range of 0.3 to 1.2 mass%, and the sacrificial anode material layer 13 of the plate fin 35 contains substantially no Cu. Therefore, the fillet 22 has a concentration exceeding the concentration of the core material 11 and the sacrificial anode material layer 13, and contains 2.0 mass% or less of Cu. This can favorably suppress (avoid or prevent) preferential corrosion of the joint portion 21, and therefore can improve the corrosion-resistant life of the plate-fin stacked heat exchanger. The structure shown in fig. 4A and 4B is the same as the structure shown in fig. 2A and 2B except for the positions where the plate fins 35 and the fillet 22 are formed, and therefore, the description thereof is omitted.

As described above, the brazing sheet of the present invention is used for a heat exchanger, and includes: a core material made of an aluminum alloy; a brazing material layer of an aluminum alloy containing silicon (Si) covering one surface of the core material; and a sacrificial anode material layer of an aluminum alloy containing zinc (Zn) in a range of 0.5 to 6.0 mass% and silicon (Si) in a range of 3.0 to 11 mass% covering the other surface of the core material, or both surfaces of the core material are covered with the sacrificial anode material layer.

The brazing sheet has a joint surface and non-joint adjacent surfaces, the joint surface is joined to each other to form a joint portion, the non-joint adjacent surfaces are adjacent to the joint surface, the joint surface is a sacrificial anode material layer, and when the joint surfaces are joined to each other, the sacrificial anode material flows out from the joint surface at a portion between the non-joint adjacent surfaces adjacent to the joint surface and is solidified to form a fillet. The brazing material and the sacrificial anode material both do not contain Cu, and the core material contains Cu in the range of 0.3-1.2 mass%.

The joint structure of the brazing sheet according to the present invention is a joint structure in which brazing sheets each having a sacrificial anode material layer coated on at least one surface of an aluminum alloy core material (the sacrificial anode material layer may be coated on both surfaces or the brazing material layer may be coated on the other surface) are joined to each other. The brazing sheet has a joining surface and non-joining adjacent surfaces adjacent to the joining surface, each joining surface is a sacrificial anode material layer, an angle formed by each non-joining adjacent surface is an acute angle, and a brazing angle formed by the sacrificial anode material flowing out from the joining surface and solidified is provided at a portion between the non-joining adjacent surfaces adjacent to the joining surface. The fillet has a concentration exceeding that of the core material, the brazing material layer, and the sacrificial anode material layer, and contains 2.0 mass% or less of Cu.

In such a configuration, when the sacrificial anode material layer is bonded by the brazing sheet, Cu diffuses intensively to a fillet formed adjacent to the bonding portion so as to have an appropriate concentration, but Cu does not substantially diffuse to the sacrificial anode material layer other than the fillet. Therefore, excessive potential degradation due to the concentrated zinc at the brazing corners is reduced or cancelled by Cu, and thus a favorable sacrificial anode effect by the brazing corners can be achieved. Further, since Cu hardly diffuses into the sacrificial anode material layer other than the brazing corner, it is possible to realize a favorable sacrificial anode action without the Cu interfering with an appropriate change in the potential due to zinc. As a result, it is possible to effectively suppress or prevent corrosion from advancing from the brazing corner to the joint portion and reducing the joint strength of the joint portion, and therefore, it is possible to improve the corrosion resistance of the joint portion of the heat exchanger.

The present invention may also include a joining method for joining brazing sheets, which are used for components constituting a heat exchanger and each have a core made of an aluminum alloy and a brazing material layer made of a brazing material on one surface of the core, and a sacrificial anode material layer made of a sacrificial anode material on the other surface of the core. In the joining method, the brazing material is an aluminum alloy containing silicon (Si), the sacrificial anode material is an aluminum alloy containing zinc (Zn) in a range of 0.5 to 6.0 mass% and silicon (Si) in a range of 3.0 to 11 mass%, the core material before joining contains copper (Cu) in a range of 0.3 to 1.2 mass%, the brazing material before joining and the sacrificial anode material do not contain copper, the brazing sheet has a joining surface and non-joining adjacent surfaces adjacent to the joining surface, each joining surface is a sacrificial anode material layer, and the joining surfaces of the brazing sheet are brought into contact with each other and heated, whereby the sacrificial anode material flows out from the joining surface and is solidified at a portion adjacent to the joining surface between the non-joining adjacent surfaces to form a fillet.

(examples)

The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited thereto. Those skilled in the art can make various alterations, modifications and changes without departing from the scope of the invention. The methods for evaluating physical properties in the following examples and comparative examples were performed as follows.

(evaluation method, etc.)

[ bonding surface and non-bonding surface of brazing sheet ]

As the brazing sheet, a 3-layer brazing sheet having a thickness of 200 μm and having one surface as a sacrificial anode material layer and the other surface as a brazing material layer was used. Or the joint surface and the non-joint adjacent surface of the brazing sheet are both used as the surface of the sacrificial anode material layer. The angle of the non-joining adjacent surfaces to the joining surfaces is somewhat different depending on the brazing sheet, but is basically about 30 ° ± 5 ° (in the range of 25 to 35 °), and when joining the joining surfaces to each other, the angle formed by the non-joining adjacent surfaces is about 60 ° ± 10 ° (in the range of 50 to 70 °).

[ elemental concentration analysis of the bonding site ]

As an Electron Probe Microanalyzer (EPMA), a product name EMPA-1600 type manufactured by shimadzu corporation was used, and a side portion of a non-joining adjacent surface side of a joining portion between solder sheets (a joining structure of solder sheets) was subjected to a voltage acceleration: 15kV, beam diameter: 2 μm, cumulative time: 1 second, step interval: the concentrations of Cu and Zn were analyzed under the analysis conditions of 2 μm and a sample current of 0.15. mu.A.

[ Corrosion resistance test ]

The corrosion resistance of the joined structure of the brazing sheet was evaluated based on the SWAAT Test (Sea Water identified Test) specified in ASTM G85-A3.

(example 1)

In the brazing sheet of example 1, an aluminum alloy (Al-1.30% Mn-0.46% Cu) containing 1.30 mass% of manganese (Mn), 0.46 mass% of copper (Cu), and the balance being aluminum (Al) was used as the core material, and an aluminum alloy (Al-7.49% Si-1.00% Zn) containing 7.49 mass% of silicon (Si), 1.00 mass% of zinc (Zn), and the balance being aluminum (Al) was used as the sacrificial anode material, and an aluminum alloy (Al-7.40% Si) containing 7.40 mass% of silicon (Si) and the balance being aluminum (Al) was used as the brazing material. In addition, the sacrificial anode material also functions as a brazing material because it contains 7.49 mass% of silicon.

A joining structure of the brazing sheets of example 1 was manufactured by brazing 2 pieces of brazing sheets at the joining surfaces to form a joined portion. In addition, the brazing conditions were 610 ℃. As shown in the sectional photograph of the upper part of fig. 5, the element concentration of the portion of the joined portion on the non-joined adjacent surface side, i.e., the brazing angle, was analyzed by the EPMA as described above along the cross-sectional direction of the arrow in the figure.

As a result, as shown in the line element analysis result of the lower graph of fig. 5, the concentration of Zn exhibited a parabolic concentration distribution in which the concentration gradually increased from the core material side toward the joint surface side in the fillet cross section and became maximum (about 0.4 wt%) in the vicinity of the joint surface (region of 200 μm ± 40 μm). On the other hand, the Cu concentration was hardly detected on the brazing material layer and core material side (regions of 0 to 140 μm and 260 to 400 μm), and was detected as a strong peak (not less than 1% by weight at the maximum, and also more than 0.4% by weight at the minimum (about 0.44% by weight)) rapidly exceeding the concentration of zinc in the vicinity of the joining surface of the fillet (region of 200 μm. + -. 40 μm).

In the color map, which is the surface analysis result obtained by EPMA, although not shown, the distribution of the entire Zn at a low concentration around the brazing angle was confirmed, but the presence of Cu at a high concentration in the vicinity of the brazing angle was confirmed.

Next, the corrosion resistance of the joint portion between the brazing sheets was evaluated by the corrosion test. As a result, as shown in the cross-sectional photograph of fig. 7A, no substantial corrosion was observed.

Comparative example

In the brazing sheet of the comparative example, the sacrificial anode material and the brazing material were the same aluminum alloy as in the brazing sheet of example 1, but an aluminum alloy (Al-1.10% Mn-0.14% Cu) in which 1.10% by mass of manganese (Mn), 0.14% by mass of copper (Cu), and the balance of aluminum were used as the core material. Since the Cu concentration is 0.2 mass% or less, it corresponds to the content of impurities in the core material.

Then, in the same manner as in example 1, 2 pieces of brazing sheets were joined to form a joint, thereby manufacturing a joined structure of brazing sheets of comparative example. As shown in the cross-sectional photograph of the upper view of fig. 6, the element concentration of the portion of the bonded portion on the non-bonded adjacent surface side was analyzed by EPMA as described above along the cross-sectional direction of the arrow in the figure.

As a result, as shown in the line element analysis result of the lower graph of fig. 6, the Zn concentration showed a parabolic concentration distribution as in the joint portion of example 1, and only two peaks smaller than the zinc concentration (about 0.2 wt% peak near 220 μm and about 0.3 wt% peak near 230 μm) were observed on the joint portion side (region of 220 to 240 μm) of one core material with respect to Cu, and no substantial Cu concentration was detected except for these peaks.

In addition, although not shown, in the color map as a result of the surface analysis by EPMA, it was confirmed that Zn was distributed at a low concentration as a whole centering on the fillet angle in the same manner as in example 1, and Cu was not basically confirmed.

Next, the corrosion resistance of the joint portion between the brazing sheets was evaluated by the corrosion test. As a result, as shown in the cross-sectional photograph of fig. 7B, corrosion occurred at the joint portion at the portion on the side of the joined adjacent surfaces.

(example 2)

The brazing sheet of example 2 was the same as the brazing sheet of example 1, except that the core material was provided with a sacrificial anode material layer on both sides and without a brazing material layer. Then, 2 pieces of brazing sheets were joined to form a joint in the same manner as in example 1, thereby manufacturing a joined structure of the brazing sheets of example 2. In this joined structure, the corrosion resistance of the joined portion of the brazing sheets was evaluated by the corrosion test. As a result, as shown in the cross-sectional photograph of fig. 9, substantial corrosion was not observed.

(comparison of examples and comparative examples)

As is apparent from a comparison between fig. 5 and 6 and a comparison between fig. 7A and 7B, when a core material containing Cu only to the extent of impurities is used (comparative example), Cu does not diffuse so as to concentrate at the fillet angle, but when a core material containing Cu within a predetermined range is used (example 1), Cu diffuses so as to concentrate at the fillet angle, so that preferential corrosion of the joint portion can be effectively suppressed (avoided or prevented).

Further, as shown in fig. 8, it is understood that a proportional relationship is established when the Cu concentrations of example 1 and comparative example are plotted with the horizontal axis as the initial Cu concentration of the core material and the vertical axis as the Cu concentration of the joint portion.

Further, as shown in fig. 9, it is found that even when both surfaces of the brazing sheet are the sacrificial anode material layers (example 2), the preferential corrosion of the joint portion can be effectively suppressed (avoided or prevented) in the same manner as in the structure in which the brazing material layer is formed on one surface of the brazing sheet and the sacrificial anode layer is formed on the other surface (example 1).

The present invention is not limited to the description of the above embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining the disclosed technical means with different embodiments or a plurality of modifications are also included in the technical scope of the present invention.

Industrial applicability of the invention

The present invention can effectively suppress or prevent the preferential corrosion of the brazing angle even when copper and zinc are contained in the brazing angle generated adjacent to the joint portion between the brazing sheets, and can improve the corrosion resistance of the heat exchanger. Therefore, the brazing sheet can be applied not only to the field of brazing sheets for heat exchangers having a sacrificial anode material layer, but also to the field of heat exchangers using the brazing sheet in a wide range.

Description of the reference numerals

10 brazing sheet

10a bonding surface

10b non-joining adjacent faces

11 core material

12 brazing material layer

13 sacrificial anode material layer

20 joining structure of brazing sheet

21 joint part

22 drill rod angle

30-plate fin laminate

31 end plate

32 plate fin

33 header opening

34-plate fin laminate

35 plate fin

40 Parallel Flow Condenser (PFC)

41 header pipe

42 flat tube

43 corrugated fins.

Claims

1. A brazing sheet for a heat exchanger, comprising:

a core material made of an aluminum alloy;

a brazing material layer covering one surface of the core material and made of a brazing material of an aluminum alloy containing silicon (Si); and

a sacrificial anode material layer covering the other surface of the core material and made of a sacrificial anode material of an aluminum alloy containing zinc (Zn) in a range of 0.5 to 6.0 mass% and silicon (Si) in a range of 3.0 to 11 mass%,

the brazing sheet has: a joint surface which is formed by joining 2 brazing sheets to each other; and a non-engagement adjacent surface adjacent to the engagement surface,

the bonding surface is the sacrificial anode material layer,

wherein a brazing angle at which the sacrificial anode material flows out from the joining surface and is solidified is formed at a portion adjacent to the joining surface between the non-joining adjacent surfaces of the 2 brazing sheets when the joining surfaces of the 2 brazing sheets are joined to each other,

the brazing material and the sacrificial anode material are free of copper (Cu),

the core material contains copper (Cu) in an amount of 0.3 to 1.2 mass%.

2. A brazing sheet for a heat exchanger, comprising:

a core material made of an aluminum alloy;

a sacrificial anode material layer covering both surfaces of the core material and made of an aluminum alloy sacrificial anode material containing zinc (Zn) in a range of 0.5 to 6.0 mass% and silicon (Si) in a range of 3.0 to 11 mass%,

the bonding surface is the sacrificial anode material layer,

a brazing angle at which the sacrificial anode material flows out from the joining surface and is solidified is formed at a portion adjacent to the joining surface between the non-joining adjacent surfaces of the 2 brazing sheets when the joining surfaces of the 2 brazing sheets are joined to each other,

the sacrificial anode material is free of copper (Cu),

the core material contains copper (Cu) in an amount of 0.3 to 1.2 mass%.

3. Brazing sheet according to claim 1 or 2, wherein:

the core material is a material obtained by adding the copper in the range of 0.3 to 1.2 mass% to any of 3000 series, 5000 series, or 6000 series aluminum alloys,

the sacrificial anode material layer is formed by adding zinc in the range of 0.5-6.0 mass% to 4000 series aluminum alloy.

4. Brazing sheet according to claim 1, wherein:

the brazing material layer is 4000 series aluminum alloy.

5. Brazing sheet according to any one of claims 1 to 4, wherein:

an angle formed by the non-joining adjacent surfaces of the 2 pieces of brazing sheet when the joining surfaces of the 2 pieces of brazing sheet are joined to each other is an acute angle.

6. A structure for joining brazing sheets, which is a structure for joining 2 pieces of brazing sheets, each of which is formed by covering at least one surface of a core material made of an aluminum alloy with a sacrificial anode material layer made of a sacrificial anode material, and which is used for constituting a component of a heat exchanger, to each other, wherein the structure for joining brazing sheets is characterized in that:

the 2 brazing sheets each have a joining face and a non-joining adjacent face adjacent to the joining face,

the bonding surface is the sacrificial anode material layer,

a brazing angle formed by the sacrificial anode material flowing out from the joining surface and solidified is provided at a portion adjacent to the joining surface between the non-joining adjacent surfaces of each of the 2 brazing sheets,

the fillet contains copper (Cu) of 2.0 mass% or less in a concentration exceeding the concentration of copper (Cu) in the core material and the sacrificial anode material layer.

7. The bonding structure of brazing sheet according to claim 6, wherein:

the sacrificial anode material is an aluminum alloy containing zinc (Zn) in the range of 0.5 to 6.0 mass% and silicon (Si) in the range of 3.0 to 11 mass%,

the core material before bonding contains copper (Cu) in a range of 0.3 to 1.2 mass%,

the sacrificial anode material before bonding is copper free.

8. The bonding structure of brazing sheet according to claim 7, wherein:

in the case where only one surface of the core material is covered with the sacrificial anode material layer, the other surface is covered with a brazing material layer made of a brazing material.

9. The bonding structure of brazing sheet according to claim 8, wherein:

the brazing material is an aluminum alloy containing silicon (Si), and the brazing material before joining does not contain copper.

10. The bonding structure of brazing sheet according to claim 7 or 9, wherein:

the fillet contains zinc (Zn), and the concentration of copper (Cu) in the fillet is higher than the concentration of zinc.

11. The bonding structure of brazing sheet according to any one of claims 6 to 10, wherein:

the angle formed by the non-joining adjacent faces of each of the 2 brazing sheets is an acute angle.

12. A heat exchanger, characterized by:

a joining structure having the brazing sheet as recited in any one of claims 6 to 11.

13. The heat exchanger of claim 12, wherein:

the heat exchanger is a plate fin stack type heat exchanger or a Parallel Flow Condenser (PFC).

14. A method of joining brazing sheets, characterized by comprising:

the method for joining 2 brazing sheets for a heat exchanger, the 2 brazing sheets each comprising:

a core material made of an aluminum alloy and containing copper (Cu) in an amount of 0.3 to 1.2 mass%;

a brazing material layer covering one surface of the core material and made of a brazing material of an aluminum alloy containing silicon (Si) and containing no copper (Cu); and

and a sacrificial anode material layer covering the other surface of the core member and made of a sacrificial anode material of an aluminum alloy containing zinc (Zn) in an amount of 0.5 to 6.0 mass% and silicon (Si) in an amount of 3.0 to 11 mass% and containing no copper (Cu), wherein the method for bonding the brazing sheet comprises:

a step of heating the bonding surfaces of the 2 pieces of brazing sheets, which are part of the sacrificial anode material layers, while abutting against each other; and

and forming a fillet by flowing out the sacrificial anode material from the joint surface and solidifying the sacrificial anode material at a portion between the 2 brazing sheets, the portion being adjacent to the joint surface and the sacrificial anode material layers not abutting each other.