Heat exchanger

Abstract

To provide a heat exchanger.SOLUTION: A heat exchanger according to the present invention is characterized in that a tube to serve as a flow path for a cooling medium is formed from an aluminum alloy brazing sheet having a brazing filler material bonded on one face of a core material and a sacrificing anode material bonded on the other face of the core material. In a relation of σ=A-B×lnNf of a plane flexure fatigue property as a property of an aluminum alloy brazing sheet, A is in a range of 160 to 210, B is in a range of 7.0 to 11.0, and n-value is 0.25 or more. The tube is brazed and bonded to a fin and a header plate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heat exchanger. [Background technology]

[0002] Aluminum alloy heat exchangers are manufactured by brazing tubes made of aluminum alloy brazing sheets, which are formed into plates to ensure a flow path for the cooling medium, to radiating fins for heat exchange and header plates. In order to improve the thermal fatigue properties of aluminum alloy heat exchangers, the structure of the heat exchanger has traditionally been modified. However, as automobiles become more electric (xEV), heat exchangers are also taking on a wide variety of shapes, and there are limits to how much structural modification can be made. Therefore, there is a need to extend the fatigue life of aluminum alloys used as components of heat exchangers.

[0003] For example, fatigue failure occurs due to stress concentration in the tube material caused by the difference in thermal expansion between the header plate and the tube material at its root during thermal cycling. To improve thermal fatigue properties, it is desirable to improve the fatigue properties of the tube material. The aluminum alloy brazing sheet used for the tubes generally has a core material with brazing filler metal bonded to one side for strength, and a sacrificial anode material with sacrificial corrosion protection function bonded to the other side.

[0004] In a conventional technique, Mg is added to an aluminum alloy brazing sheet to increase its strength in order to improve the thermal fatigue properties of the aluminum alloy for heat exchangers. However, when using an aluminum alloy brazing sheet containing magnesium, the magnesium reacts first with the non-corrosive flux used to remove the oxide film during brazing, which can result in an insufficient brazing joint.

[0005] The thermal fatigue characteristics of a typical heat exchanger are such that it breaks after several thousand to several tens of thousands of cycles, but this range is often classified as low-cycle fatigue for aluminum alloys. While improving ductility is known as a countermeasure against low-cycle fatigue in aluminum alloys, the ductility and strength of aluminum alloys are in a trade-off relationship. For example, if a 1000-series alloy with excellent ductility is used, the strength is low, significantly reducing the vibration resistance of the heat exchanger.

[0006] For example, Patent Document 1 below describes a technology for suppressing crack occurrence by making the hardness ratio of the core material to the lining material less than 1.0, but does not mention the n value, and does not specify measures to prevent crack propagation behavior. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-255014 Summary of the Invention [Problem to be solved by the invention]

[0008] To improve the thermal fatigue properties of heat exchangers, it is necessary to improve the fatigue properties of aluminum alloy brazing sheets for tubes while achieving both high strength and a high work hardening index. That is, in addition to improving the fatigue properties of the brazing sheet, high strength is required to suppress strain that occurs during thermal cycling, and a high work hardening index is required to reduce the crack propagation rate of the brazing sheet. As explained above, the prior art has not provided sufficient techniques for improving thermal fatigue properties.

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a heat exchanger with excellent thermal fatigue characteristics. [Means for solving the problem]

[0010] (1) A heat exchanger according to one embodiment of the present invention is an aluminum alloy brazing sheet formed by bonding a brazing material to one surface of a core material and bonding a sacrificial anode material to the other surface of the core material, wherein the aluminum alloy brazing sheet has plane bending fatigue properties in the relationship σ=AB×lnNf, where A is in the range of 160 to 210 and B is in the range of 7.0 to 11.0, and wherein tubes serving as flow paths for a cooling medium are formed from the aluminum alloy brazing sheet having an n value of 0.25 or more, and the tubes are brazed to fins and a header plate.

[0011] (2) In a heat exchanger according to one embodiment of the present invention, in the heat exchanger described in (1), it is preferable that the core material of the aluminum alloy brazing sheet is made of an aluminum alloy containing, by mass%, 1.3 to 1.8% Mn, 0.6 to 1.1% Si, 0.6 to 1.3% Cu, and 0.05 to 0.3% Zr, with the remainder being Al and unavoidable impurities. (3) In a heat exchanger according to one embodiment of the present invention, in the heat exchanger described in (2), the core material of the aluminum alloy brazing sheet further contains, in addition to the above composition, one or more of, by mass%, Fe: 0.1 to 0.7%, Zn: 0.05 to 1.0%, Ti: 0.3% or less, Cr: 0.3% or less, Mg: 0.3% or less, Sc: 0.3% or less, V: 0.3% or less, Co: 0.3% or less, Ni: 0.3% or less, Sr: 0.3% or less, Y: 0.3% or less, Mo: 0.3% or less, In: 0.3% or less, Sn: 0.3% or less, Sb: 0.3% or less, and Bi: 0.3% or less. When any of Ti, Cr, Mg, Sc, V, Co, Ni, Sr, Y, Mo, In, Sn, Sb, or Bi is contained, it is preferable that the total content of these is 1.0% or less.

[0012] (4) In a heat exchanger according to one embodiment of the present invention, in the heat exchanger described in (2) or (3), the brazing filler metal preferably comprises an aluminum alloy containing Si or Si and Zn, and when Si is contained, the aluminum alloy contains 6.0 to 13.0% by mass of Si, and when Zn is contained, the aluminum alloy contains 3.5% by mass or less of Zn, with the remainder being Al and unavoidable impurities.

[0013] (5) In a heat exchanger according to one embodiment of the present invention, in the heat exchanger described in (2) or (3), the brazing filler metal preferably contains Si or Si and Zn, and when Si is contained, the brazing filler metal contains 6.0 to 13.0% by mass of Si, and when Zn is contained, the brazing filler metal contains 3.5% by mass or less of Zn, and further contains, by mass, one or more of Fe: 0.1 to 0.7%, Mn: 0.3% or less, Ti: 0.3% or less, Cr: 0.3% or less, and Zr: 0.3% or less, and when any of Mn, Ti, Cr, and Zr is contained, the total of these is 1.0% by mass or less, and the remainder is preferably an aluminum alloy having a composition of Al and unavoidable impurities. (6) In a heat exchanger according to one embodiment of the present invention, in the heat exchanger described in (4), the brazing filler metal preferably contains, in addition to the above composition, one or more of, by mass%, Fe: 0.1 to 0.7%, Mn: 0.3% or less, Ti: 0.3% or less, Cr: 0.3% or less, and Zr: 0.3% or less, and when any of Mn, Ti, Cr, and Zr is contained, the total content of these is 1.0% or less by mass, with the remainder being an aluminum alloy having a composition of Al and unavoidable impurities.

[0014] (7) In a heat exchanger according to one embodiment of the present invention, in the heat exchanger described in (1) or (2), it is preferable that the sacrificial anode material is made of an aluminum alloy containing, by mass%, 1.3 to 1.8% Mn, 0.4 to 0.9% Si, 2.0 to 8.0% Zn, and 0.05 to 0.3% Zr, with the remainder being Al and unavoidable impurities. (8) In a heat exchanger according to one embodiment of the present invention, in the heat exchanger described in (7), the sacrificial anode material preferably comprises an aluminum alloy having the above composition, further containing, by mass%, one or more of Fe: 0.1 to 0.7%, Ti: 0.01 to 0.3%, and Cr: 0.01 to 0.3%, with the remainder being Al and unavoidable impurities. [Effects of the Invention]

[0015] The present invention can provide a heat exchanger that has excellent thermal fatigue properties. In addition, the present invention can provide a heat exchanger that can achieve both high strength and a high work hardening index in addition to improved thermal fatigue properties. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing an example of a heat exchanger according to a first embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view showing an example of a brazing sheet applied to the heat exchanger of the first embodiment. [Figure 3] FIG. 2 is an explanatory diagram showing a test method for measuring plane bending fatigue properties in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an example of an embodiment will be described in detail with reference to the accompanying drawings. Note that the drawings used in the following description may show characteristic portions in an enlarged scale for the sake of convenience in order to make the characteristics easier to understand. 1 shows an aluminum alloy heat exchanger A according to a first embodiment, which is constructed by assembling and brazing fins 5, tubes 6, a reinforcing plate 7, and a header plate 8. This heat exchanger A is an example of a heat exchanger used in automobiles and the like. In the heat exchanger A, the tubes 6 are obtained by processing a brazing sheet 4, which serves as a cladding material shown in Fig. 2, into a tubular shape. As an example, the brazing sheet 4 has a three-layer structure consisting of a core material 1 made of an aluminum alloy, a brazing material (skin material) 2 made of an aluminum alloy attached to one side of the core material 1, and a sacrificial anode material 3 made of an aluminum alloy attached to the other side of the core material 1.

[0018] The brazing sheet 4 may have a multi-layer structure of the core material 1 and the brazing material 2, or may have a four-layer or five-layer structure in which a sacrificial anode material is provided between the core material 1 and the brazing material 2. In the example shown in Fig. 1, the brazing material spreads around the contact areas between the curved portions of the fins 5 and the tubes 6 during brazing heating, forming fillet joints around the contact areas between the fins 5 and the tubes 6. Although fillet joints are not shown in Fig. 1, they are formed not only around the contact areas between the fins 5 and the tubes 6 but also around the portions where the tubes 6 penetrate the header plate 8. The fins 5, the tubes 6, and the header plate 8 are integrated by the brazing joints to form the heat exchanger A.

[0019] "Plane bending fatigue properties of brazing sheet 4" When the stress σ applied and the fracture life Nf in the plane bending fatigue characteristics of the brazing sheet 4 are expressed by the relational expression σ=AB×lnNf, it is preferable that A is in the range of 160 to 210 and B is in the range of 7.0 to 11.0. In addition, when a numerical range described in this specification is expressed using "to," the range includes both the lower and upper limits unless otherwise specified. For example, 160 to 210 means a range of 160 to 210.

[0020] In the above formula, A is a coefficient mainly related to the breaking strength of the tube material after brazing, and B is a coefficient mainly related to the fatigue properties of the tube. If A is less than 160, the desired thermal fatigue properties of the heat exchanger cannot be obtained. If A exceeds 210, it is effective for improving the thermal fatigue properties, but the material strength generally becomes high, making tube molding difficult. Therefore, A is preferably 160 or more and 210 or less. If B is less than 7.0, the desired thermal fatigue properties of the heat exchanger cannot be obtained. If B exceeds 11.0, it is effective in improving the thermal fatigue properties. However, it is difficult for B to exceed 11.0 in the alloy system that constitutes the aluminum alloy brazing sheet. Therefore, B is preferably 7.0 or more and 11.0 or less.

[0021] "n-value" The n value of the brazing sheet 4 must be 0.25 or more. If the n value is less than 0.25, when a crack occurs in the tube 6, the crack will grow too quickly and the desired thermal fatigue characteristics of the heat exchanger cannot be obtained.

[0022] "Range of composition of aluminum alloy for tube construction" "Heartwood" In this embodiment, the core material 1 is made of an aluminum alloy containing, by mass %, 1.3-1.8% Mn, 0.6-1.1% Si, 0.6-1.3% Cu, 0.05-0.3% Zr, and the remainder being Al and unavoidable impurities. In addition to the elements mentioned above, the aluminum alloy constituting the core material 1 further contains, by mass%, one or more of the following: Fe: 0.1-0.7%, Zn: 0.05-1.0%, Ti: 0.3% or less, Cr: 0.3% or less, Mg: 0.3% or less, Sc: 0.3% or less, V: 0.3% or less, Co: 0.3% or less, Ni: 0.3% or less, Sr: 0.3% or less, Y: 0.3% or less, Mo: 0.3% or less, In: 0.3% or less, Sn: 0.3% or less, Sb: 0.3% or less, and Bi: 0.3% or less; and if any of Ti, Cr, Mg, Sc, V, Co, Ni, Sr, Y, Mo, In, Sn, Sb, or Bi is contained, it is preferable that the total content of these be 1.0% or less. The numerical ranges of the alloy composition have the same meaning as the numerical ranges described above, so 1.3 to 1.8% means 1.3% or more and 1.8% or less.

[0023] Mn: 1.3 to 1.8% Mn can be added within the above range to improve the material strength of the core material 1. Mn improves the tensile strength of the core material 1 through solid solution strengthening, and also contributes to the precipitation of intermetallic compounds such as Al-Mn, Al-Mn-Si, and Al-Mn-Fe-Si in the core material 1, improving the tensile strength and n value through dispersion strengthening. If the Mn content is less than 1.3%, the desired strength improvement effect cannot be obtained, while if the Mn content exceeds 1.8%, large intermetallic compounds are formed during casting, which causes fractures due to the intermetallic compounds during rolling of the brazing sheet, making manufacturing difficult. Si: 0.6 to 1.1% Si can be added within the above range to improve the material strength of the core material 1. Si improves tensile strength through solid solution strengthening, and also contributes to the precipitation of intermetallic compounds such as Al-Mn-Si and Al-Mn-Fe-Si in the core material, improving tensile strength and the n value through dispersion strengthening. If the Si content is less than 0.6%, the desired strength improvement effect cannot be obtained. If the Si content exceeds 1.1%, the melting point of the matrix of the core material 1 decreases, which may cause local melting during brazing and result in poor brazing of the heat exchanger.

[0024] Cu: 0.6 to 1.3% Cu can be added within the above range to improve the material strength of the core material 1 through solid solution strengthening. If the Cu content is less than 0.6%, the desired tensile strength cannot be obtained. If the Cu content exceeds 1.3%, the melting point of the matrix of the core material 1 decreases, which may cause local melting during brazing, resulting in poor brazing joints in the heat exchanger A. Furthermore, if the Cu content exceeds 1.3%, the concentration diffusing into the brazing material increases, resulting in concentration in the fillet joints between the tubes 6 and fins 5 and between the tubes 6 and header plate 8, which may reduce the corrosion resistance of the heat exchanger A. Zr: 0.05 to 0.3% Zr can be added within the above range to improve the strength of the core material. Zr improves the strength of the core material through solid solution strengthening, and also contributes to the precipitation of Al-Mn-Si compounds and Al-Zr intermetallic compounds in the core material 1, improving the tensile strength and n value through dispersion strengthening. If the Zr content is less than 0.05%, the desired strength improvement effect cannot be obtained, whereas if the Zr content exceeds 0.3%, large intermetallic compounds are formed during casting, and the rollability of the aluminum alloy brazing sheet 4 decreases.

[0025] Fe: 0.1 to 0.7% Fe can be added within the above range to improve the material strength of the core material 1. Fe improves the material strength of the core material 1 through solid solution strengthening, and also contributes to the precipitation of intermetallic compounds such as Al-Fe, Al-Fe-Si, and Al-Mn-Fe-Si in the core material 1, improving the tensile strength and n value through dispersion strengthening. If the Fe content is less than 0.1%, high-purity aluminum must be used, which increases costs. If the Fe content exceeds 0.7%, large intermetallic compounds are formed during casting, reducing the rollability of the aluminum alloy brazing sheet 4. However, Fe may be contained in an amount of less than 0.3% as an unavoidable impurity.

[0026] Zn: 0.05 to 1.0% When Zn is added simultaneously with Cu, it can be added in the above range to improve elongation and fatigue life. It is desirable that the Zn content be in the above range. If the Zn content is less than 0.05%, the desired effect cannot be obtained. If the Zn content exceeds 1.0%, there is no problem in improving the fatigue life, but the self-corrosion rate of the brazing sheet increases, and the corrosion resistance of the heat exchanger A decreases. Other elements Additionally, in the aluminum alloy brazing sheet of this embodiment, the core material may contain 0.3% or less of each of Ti, Cr, Mg, Sc, V, Co, Ni, Sr, Y, Mo, In, Sn, Sb, and Bi, and a total of 1.0% or less. The inclusion of these elements effectively improves the desired thermal fatigue life of the heat exchanger. The content of these elements may be 0. Inevitable impurities In addition, the core material of the aluminum alloy brazing sheet of this embodiment may contain other unavoidable impurities, and the content of these impurities is preferably 0.05% or less.

[0027] "Brazing material" In this embodiment, the brazing filler metal 2 is made of an aluminum alloy containing, by mass %, 6.0 to 13.0% Si, with the remainder being Al and unavoidable impurities. The aluminum alloy constituting the brazing filler metal 2 may contain 3.5 mass % or less of Zn in addition to the above-mentioned Si. In addition to the elements mentioned above, the aluminum alloy constituting the brazing filler material 2 further contains, by mass%, one or more of Fe: 0.1 to 0.7%, Mn: 0.3% or less, Ti: 0.3% or less, Cr: 0.3% or less, and Zr: 0.3% or less, and if any of Mn, Ti, Cr, or Zr is contained, it is preferable that the total content of these be 1.0% or less. Si: 6.0 to 13.0% Si is necessary to lower the melting point of Al, allowing the brazing filler metal 2 to melt during brazing and become a brazing filler metal when brazing to other components. If the Si content is less than 6.0%, sufficient molten brazing filler metal is not produced, which may result in brazing defects. If the Si content exceeds 13.0%, brazing filler metal erosion to other components, such as the core material 1 and fins 5 of the brazing sheet, may occur more easily, which may result in brazing defects.

[0028] Zn:3.5% or less Zn makes the potential of the brazing filler metal 2 less noble, and has the effect of protecting the core material 1 from corrosion by acting as a sacrificial anode. If Zn is not added, the brazing filler metal 2 will not be able to sacrificially protect the core material 1 from corrosion. If the brazing filler metal 2 contains more than 3.5% Zn, Zn will concentrate at the fillet joints between the fins 5 and the tubes 6 and at the fillet joints between the header plate 8 and the tubes 6, causing these fillet joints to corrode early, which could reduce the corrosion resistance of the heat exchanger A. Other elements Additionally, the brazing filler metal 2 of this embodiment may contain 0.1 to 0.7% or less of Fe. It may also contain 0.3% or less of each of Mn, Zr, Ti, and Cr, with a total of 1.0% or less. The inclusion of these elements effectively improves the desired thermal fatigue life of the heat exchanger. The content of these elements may be 0. Fe: 0.1 to 0.7% Fe can be added within the above range in order to improve the material strength of the brazing filler metal 2. Fe improves the material strength of the brazing filler metal 2 through solid solution strengthening. If the Fe content is less than 0.1%, high-purity aluminum must be used, which increases costs. If the Fe content exceeds 0.7%, large intermetallic compounds are formed during casting, which reduces the rollability of the aluminum alloy brazing sheet 4. Inevitable impurities In addition, the brazing filler metal of the aluminum alloy brazing sheet in this embodiment may contain other unavoidable impurities, and the content of these impurities is preferably 0.05% or less.

[0029] "Sacrificial anode material" In this embodiment, the sacrificial anode material 3 is made of an aluminum alloy containing, by mass %, 1.3 to 1.8% Mn, 0.4 to 0.9% Si, 2.0 to 8.0% Zn, 0.05 to 0.3% Zr, and the remainder being unavoidable impurities and Al. In addition to the above elements, one or more of the following may be added to the aluminum alloy constituting the sacrificial anode material 3: Fe: 0.1 to 0.7%, Ti: 0.01 to 0.3%, and Cr: 0.01 to 0.3%.

[0030] Mn: 1.3 to 1.8% Mn can be added to the sacrificial anode material 3 within the above range in order to improve the strength of the sacrificial anode material. Mn improves the tensile strength of the core material 1 through solid solution strengthening, and also contributes to the precipitation of intermetallic compounds such as Al-Mn, Al-Mn-Si, and Al-Mn-Fe-Si in the sacrificial anode material, improving the tensile strength and n value through dispersion strengthening. If the Mn content is less than 1.3%, the desired strength improvement effect cannot be achieved in the sacrificial anode material. If the Mn content exceeds 1.8%, large intermetallic compounds are formed during casting, which makes manufacturing difficult, as they can cause breakage due to the intermetallic compounds when the brazing sheet is rolled. Improving the strength of the sacrificial anode material improves the strength of the brazing sheet, and when a tube is made from the brazing sheet, the fatigue strength is improved.

[0031] Si: 0.4 to 0.9% Si can be added within the above range to improve the strength of the sacrificial anode material. Si improves tensile strength through solid solution strengthening, and also contributes to the precipitation of intermetallic compounds such as Al-Mn-Si and Al-Mn-Fe-Si in the sacrificial anode material, improving tensile strength and n value through dispersion strengthening. If the Si content is less than 0.4%, the desired strength improvement effect cannot be obtained in the sacrificial anode material. If the Si content exceeds 0.9%, the melting point of the matrix of the core material 1 decreases, which may cause local melting during brazing and result in poor brazing joints in the heat exchanger. Improving the strength of the sacrificial anode material improves the strength of the brazing sheet, and when a tube is made from the brazing sheet, the fatigue strength is improved. Zn: 2.0 to 8.0% Zn makes the potential of the sacrificial anode material 3 less noble, and acts as a sacrificial anode to protect the core material 1 from corrosion. If the Zn content is less than 2.0%, the desired sacrificial anode effect cannot be obtained, and through-holes will form early, reducing the corrosion resistance of the heat exchanger A. Similarly, if the Zn content exceeds 8.0%, the corrosion rate of the sacrificial anode material 3 will increase, and the core material 1 will be exposed early, which may cause through-holes to form, reducing the corrosion resistance of the heat exchanger.

[0032] Zr: 0.05 to 0.3% Zr can be added within the above range to improve the strength of the sacrificial anode material. Zr improves the strength of the sacrificial anode material through solid solution strengthening, and also contributes to the precipitation of Al-Mn-Si compounds and Al-Zr intermetallic compounds in the sacrificial anode material, improving the tensile strength and n value through dispersion strengthening. If the Zr content is less than 0.05%, the desired strength improvement effect cannot be obtained. If the Zr content exceeds 0.3%, large intermetallic compounds are formed during casting, reducing the rollability of the aluminum alloy brazing sheet 4. Improving the strength of the sacrificial anode material improves the strength of the brazing sheet, and when a tube is made from the brazing sheet, the fatigue strength is improved.

[0033] Fe: 0.1 to 0.7% Fe can be added within the above range to improve the material strength of the sacrificial anode material. Fe improves the material strength of the sacrificial anode material through solid solution strengthening, and also contributes to the precipitation of intermetallic compounds such as Al-Fe, Al-Fe-Si, and Al-Mn-Fe-Si in the sacrificial anode material, improving the tensile strength and n-value through dispersion strengthening. If the Fe content is less than 0.1%, high-purity aluminum must be used, which increases costs. If the Fe content exceeds 0.7%, large intermetallic compounds are formed during casting, reducing the rollability of the aluminum alloy brazing sheet 4. However, it is acceptable for the aluminum alloy brazing sheet 4 to contain less than 0.3% of Fe as an unavoidable impurity.

[0034] Ti, Cr: 0.01 to 0.3% Ti and Cr can be added within the above-mentioned ranges to improve the material strength of the sacrificial anode material. Ti and Cr precipitate as Al-Ti and Al-Cr intermetallic compounds, contributing to improving the strength of the sacrificial anode material through dispersion strengthening. If the Ti and Cr contents are less than 0.01%, the desired strength improvement effect cannot be obtained. If the Ti and Cr contents are more than 0.3%, large intermetallic compounds are formed during casting, reducing the rollability of the aluminum alloy brazing sheet 4.

[0035] "fin" The fins 5 of the aluminum alloy heat exchanger A of this embodiment are made of an aluminum alloy. As shown in Fig. 1, aluminum alloy plates are formed into a fin shape by corrugating. The material of the fins 5 is generally an aluminum alloy containing Zn added to a 3000 series alloy to impart a sacrificial anode effect. Header plate The header plate 8 in the aluminum alloy heat exchanger A of this embodiment is made of an aluminum alloy. An aluminum alloy brazing sheet is produced as needed using the same manufacturing method as the aluminum alloy brazing sheet 4 used for the tubes 6, and then processed into the required shape of the header plate by press molding or the like. "Reinforcing plate" As an example, the reinforcing plate 7 can be a clad material in which a JIS 3000 series alloy plate material is clad with a JIS 4000 series alloy brazing material, but it is not limited to this structure and any general reinforcing material used in heat exchangers can be used as appropriate.

[0036] Heat exchanger A is a device that is used repeatedly for long periods of time to exchange heat by flowing refrigerant through tubes 6 and sending high-temperature air to fins 5, so each time it is used, stress concentration due to differences in thermal expansion acts on tubes 6. 1, the tubes 6 are formed from brazing sheets 4 in which, when the average bending fatigue characteristics are expressed by the relational expression σ=AB×lnNf, A is in the range of 160 to 210 and B is in the range of 7.0 to 11.0. Therefore, even if stress concentration due to the difference in thermal expansion acts repeatedly on the tubes 6, it is possible to provide a heat exchanger A in which the risk of fatigue fracture of the brazed joints of the heat exchanger A is low. Furthermore, since the n value of the brazing sheet 4 is 0.25 or more, even if a crack occurs in the tube 6, the crack will not propagate at a slow rate, and the heat exchanger A can be provided with excellent durability. [Example]

[0037] Brazing sheets Nos. 1 to 20 were produced by combining core materials made of aluminum alloys with compositions shown in A1 to A11 in Tables 1 and 2, brazing filler materials made of aluminum alloys with compositions shown in B1 to B8 in Table 3, and sacrificial anode materials made of aluminum alloys with compositions shown in C1 to C6 in Table 4 as shown in Table 5. These brazing sheets were configured with brazing filler material placed on one side of a plate-shaped core material and sacrificial anode material placed on the other side of the core material. For each aluminum alloy that constitutes the core material shown in Tables 1 and 2, the brazing filler metal shown in Table 3, and the sacrificial anode material shown in Table 4, only the main components are listed, and the contents of inevitable impurities and aluminum that make up the remainder are omitted in each table.

[0038] Aluminum alloys with the compositions shown in Tables 1 and 2 were melted using semi-continuous casting, and the core materials were homogenized at 580°C for 10 hours. The homogenization conditions described above ensure that the intermetallic compounds are dispersed in an appropriate state to achieve the desired plane bending fatigue properties. The brazing filler metal and sacrificial anode material were not homogenized.

[0039] Brazing filler metal and sacrificial anode material with a thickness according to the cladding ratio for the core material are prepared by hot rolling, and the core material, brazing filler metal, and sacrificial anode material are clad rolled together. The core material, brazing filler metal, and sacrificial material are hot rolled and cold rolled as described below, and the final thickness is prepared to achieve a cladding ratio of brazing filler metal:core material:sacrificial material = 10%:75%:15%. The conditions for the clad rolling were not particularly specified, but the clad rolling was carried out by heating a combination of the core material, brazing material, and sacrificial material to 500° C. and then hot rolling. After hot rolling, the steel is subjected to multiple passes of cold rolling with a total reduction of 50 to 99%, and intermediate annealing is performed during the cold rolling. The intermediate annealing was carried out by increasing the temperature at 50°C / h, heating at 350°C for 5 hours, and then slowly cooling. After intermediate annealing, the final reduction rate was set to 30%, and the sheet was reduced to a thickness of 0.2 mm to obtain an aluminum alloy brazing sheet with a temper grade of H14. The heating conditions during clad rolling, the rolling conditions during hot rolling, and the intermediate annealing conditions described above are just examples adopted in this example, and the present invention is not limited to these conditions.

[0040] For each of the brazing sheets Nos. 1 to 20 shown in Table 5, various properties were measured using the evaluation methods described below. "Plane bending fatigue properties" The obtained aluminum alloy brazing sheet with temper H14 was subjected to a heat treatment equivalent to brazing at 600°C for 3 minutes. After brazing, the aluminum alloy brazing sheet was processed into a test piece so that the longitudinal direction was parallel to the rolling direction, and both ends of the test piece were fixed in the chucks of the testing machine. A bending test was then performed in which the test piece was repeatedly bent along a metal pulley (described later) to impart a specified bending strain. The bending test was carried out as a pulsating fatigue test in which only one brazing filler metal of the aluminum alloy brazing sheet was subjected to repeated tension.

[0041] As shown in FIG. 3, the upper side of the aluminum alloy brazing sheet 4 is inserted between metal pulleys 10 and 11 arranged on the left and right with a gap between them, and the aluminum alloy brazing sheet 4 is sandwiched between the metal pulleys 10 and 11. The test involved repeatedly bending the upper side of the aluminum alloy brazing sheet 4, which protruded above the metal pulleys 10 and 11, along the outer circumferential surface of the pulley 10 on the left side of Figure 3. In order to conduct a bending test in which the brazing material side was subjected to tension, the brazing material 2 was placed on the right side of the figure, with the core material 1 at the center, and the sacrificial anode material 3 was placed on the left side of the brazing sheet 4, which had a three-layer structure, and the bending test was performed using this sheet.

[0042] The stress σ (MPa) applied to each brazing sheet and the repeated fracture life Nf were obtained by plane bending fatigue tests and organized using the relational expression σ = AB × lnNf. The longer Nf is relative to the stress σ applied to the brazing sheet (i.e., if A and B are in the appropriate range), the better the thermal fatigue environment that can be achieved in the heat exchanger.

[0043] "Measurement of n value" The n-value was measured by measuring the 0.2% yield strength using a method conforming to JIS Z2241, and calculating the n-value between nominal strains of 1% and 2% using a method conforming to JIS Z2253, and then calculating the average value. "Heat exchanger cold and heat cycle performance" A heat exchanger having the configuration shown in Figure 1 was assembled using the brazing sheet described above, and after brazing, the number of times until the tube broke in a thermal cycle of 20°C x 1 min - 80°C x 1 min was evaluated. The test was stopped at 10,000 cycles, and the test samples in which no leakage was observed from the heat exchanger tubes were evaluated as ◯, and the test samples in which leakage was observed from the heat exchanger tubes in less than 10,000 cycles were evaluated as ×.

[0044] "Dispersion state of intermetallic compounds after brazing" The obtained aluminum alloy brazing sheet with temper H14 was subjected to a brazing-equivalent heat treatment of 600°C for 3 minutes. After brazing, the aluminum alloy brazing sheet was subjected to cross-section polishing on a cross section parallel to the rolling direction, and the number of intermetallic compounds was observed. Ten secondary electron images of the processed cross section were taken with a field emission scanning electron microscope (FE-SEM) at a magnification of 20,000. The circle-equivalent diameter and distribution density of the intermetallic compound particles were calculated from the acquired images. The presence of Al-Mn-Si intermetallic compounds was determined based on the elements detected by elemental analysis using EDS. After brazing, the Al-Mn-Si intermetallic compound had a diameter equivalent to a circle of 0.01 x 10 -3 mm or more 1.0×10 -3 The distribution density of compounds with diameters of mm or less is 0.30×10 6 pieces / mm 2 ~1.0×10 6 pieces / mm 2 It was. The distribution density of intermetallic compounds is 0.30×10 6 pieces / mm 2 If the distribution density of the intermetallic compounds is less than 0.30×10, the mechanical properties after brazing will be reduced and the life of the heat exchanger will be shortened. 6 pieces / mm 2 It is preferable that this is equal to or greater than this.

[0045] The core material compositions explained above are shown in Tables 1 and 2, the brazing material compositions in Table 3, the sacrificial material compositions in Table 4, and the values ​​of A, B, n, Nf values ​​at σ = 100 MPa, Nf values ​​at σ = 120 MPa, and performance evaluation results (fatigue property measurement results) in Table 5. The fatigue properties were measured under the following conditions (procedures). The strain value is read when the brazing sheet is completely aligned with the metal pulley of the fatigue testing machine. A fatigue test is conducted and the fracture life is read. The brazing sheet that has been fatigue tested up to 10% of its fracture life is processed into a tensile test piece and a tensile test is conducted. (10% of fracture life: the value at which the work hardening of the brazing sheet during the fatigue test becomes saturated.) Based on the stress-strain diagram obtained as described above, the stress corresponding to the strain value when the material is completely aligned along the metal pulley is defined as σ.

[0046] [Table 1]

[0047] [Table 2]

[0048] [Table 3]

[0049] [Table 4]

[0050] [Table 5]

[0051] Examples No. 1 to 14 shown in Table 5 show the results of evaluating the performance of brazing sheets using core materials A1 to A9, brazing materials B1 to B6, and sacrificial materials C1 to C4, as well as heat exchangers constructed using these brazing sheets. Examples Nos. 1 to 14 are aluminum alloy brazing sheets formed by bonding a brazing filler metal to one surface of a core material and a sacrificial anode material to the other surface of the core material, and the aluminum alloy brazing sheets have plane bending fatigue properties characterized by A being in the range of 160 to 210 and B being in the range of 7.0 to 11.0 in the relationship σ = AB × lnNf, and the aluminum alloy brazing sheets have an n value of 0.25 or more, and tubes that serve as cooling medium flow paths are formed from the aluminum alloy brazing sheets, and the tubes are brazed to fins and a header plate. The heat exchangers of the examples showed excellent performance with excellent fatigue resistance.

[0052] Comparative example No. 15 shown in Table 5 was determined to have reduced heat exchanger performance because the Mn, Si, and Cu contents were below the desired range and the plane bending fatigue properties (A value) of the brazing sheet did not meet the desired range. In the comparative example No. 16 shown in Table 5, the contents of Mn, Si, and Cu exceeded the desired range, and coarse compounds were formed in the core material of the brazing sheet, so a normal tube shape could not be obtained. In the comparative example No. 17 shown in Table 5, the Si content of the brazing material was low, and it was determined that the insufficient molten brazing material reduced the adhesive strength, shortening the fracture life and reducing the performance as a heat exchanger.

[0053] In the comparative example No. 18 shown in Table 5, the Si content of the brazing filler metal was too high, and the excess molten brazing filler caused braze erosion of the components, shortening the fracture life and reducing the performance as a heat exchanger. In the comparative example No. 19 shown in Table 5, the Mn, Si, and Zn contents of the sacrificial material were below the desired range, and the values ​​of Nf100 and Nf120 were low, which was judged to have reduced the performance of the heat exchanger. In the comparative example No. 20 shown in Table 4, the Mn, Si, and Zn contents of the sacrificial material exceeded the desired range, resulting in the formation of coarse compounds in the sacrificial material of the brazing sheet, making it impossible to obtain a normal tube shape. [Explanation of symbols]

[0054] A...heat exchanger, 1...core material, 2...filling material, 3...sacrificial anode material, 4...brazing sheet, 5...fin, 6...tube, 7...reinforcing plate, 8...header plate, 10, 11...metal pulleys.

Claims

1. An aluminum alloy brazing sheet having a brazing material bonded to one surface of a core material and a sacrificial anode material bonded to the other surface of the core material, Characteristics of aluminum alloy brazing sheet In the plane bending fatigue property, the relationship is σ=A-B×lnNf, A is in the range of 160 to 210, B is in the range of 7.0 to 11.0, and a tube serving as a flow path for a cooling medium is formed from an aluminum alloy brazing sheet having an n value of 0.25 or more, A heat exchanger in which the tubes are brazed to the fins and header plate.

2. The core material of the aluminum alloy brazing sheet is made of an aluminum alloy having a composition containing, by mass%, 1.3 to 1.8% Mn, 0.6 to 1.1% Si, 0.6 to 1.3% Cu, and 0.05 to 0.3% Zr, with the balance being Al and unavoidable impurities. The heat exchanger of claim 1 .

3. the core material of the aluminum alloy brazing sheet further contains, in addition to the above composition, one or more of, by mass%, Fe: 0.1 to 0.7%, Zn: 0.05 to 1.0%, Ti: 0.3% or less, Cr: 0.3% or less, Mg: 0.3% or less, Sc: 0.3% or less, V: 0.3% or less, Co: 0.3% or less, Ni: 0.3% or less, Sr: 0.3% or less, Y: 0.3% or less, Mo: 0.3% or less, In: 0.3% or less, Sn: 0.3% or less, Sb: 0.3% or less, and Bi: 0.3% or less; When any of Ti, Cr, Mg, Sc, V, Co, Ni, Sr, Y, Mo, In, Sn, Sb, and Bi is contained, the total content of these elements is 1.0% or less.

3. The heat exchanger of claim 2.

4. The brazing filler metal contains Si or Si and Zn, and when Si is contained, the Si content is 6.0 to 13.0% by mass, and when Zn is contained, the Zn content is 3.5% by mass or less, with the remainder being an aluminum alloy containing Al and inevitable impurities. The heat exchanger according to claim 2 or 3.

5. 4. The heat exchanger according to claim 2 or 3, wherein the brazing filler metal contains Si or Si and Zn, and when Si is contained, the Si content is 6.0 to 13.0% by mass, and when Zn is contained, the Zn content is 3.5% by mass or less, and further contains, by mass, one or more of Fe: 0.1 to 0.7%, Mn: 0.3% or less, Ti: 0.3% or less, Cr: 0.3% or less, and Zr: 0.3% or less, and when any of Mn, Ti, Cr, and Zr is contained, the total content of these elements is 1.0% by mass or less, and the remainder is an aluminum alloy having a composition of Al and unavoidable impurities.

6. 5. The heat exchanger according to claim 4, wherein the brazing filler metal further contains, in addition to the above composition, one or more of, by mass%, Fe: 0.1 to 0.7%, Mn: 0.3% or less, Ti: 0.3% or less, Cr: 0.3% or less, and Zr: 0.3% or less, and when any of Mn, Ti, Cr, and Zr is contained, the total content of these elements is 1.0% or less by mass, and the balance is Al and unavoidable impurities.

7. The sacrificial anode material contains, in mass%, Mn: 1.3 to 1.8%, Si: 0.4 to 0.9%, Zn: 2.0 to 8.0%, and Zr: 0.05 to 0.3%, The balance is an aluminum alloy having a composition of Al and unavoidable impurities. The heat exchanger according to claim 1 or 2.

8. The sacrificial anode material is an aluminum alloy having the above composition and further containing, in mass %, one or more of Fe: 0.1 to 0.7%, Ti: 0.01 to 0.3%, and Cr: 0.01 to 0.3%, with the remainder being Al and unavoidable impurities.

6. The heat exchanger according to claim 5.

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