JP6624417B2 - Brazing sheet with excellent corrosion resistance after brazing - Google Patents

Description

  The present invention relates to a brazing sheet used for a heat exchanger and the like, which has excellent corrosion resistance after brazing.

  BACKGROUND ART A heat exchanger for an automobile made of an aluminum alloy has been conventionally known. This heat exchanger is composed of members such as outer fins, tubes, header plates, and side supports. Further, a heat exchanger for automobiles is generally manufactured using a fluoride-based flux by joining the above members by brazing at a temperature of about 600 ° C.

Further, the tubes and the header plate that constitute the heat exchanger may be composed of a brazing sheet.
As this brazing sheet, for example, a brazing material of an Al-Si alloy is attached to one surface of a core material composed of an aluminum alloy containing Mn, Cu, Si, and Fe in a specified range, and the other surface is used. In addition, a configuration is known in which a sacrifice material (lining material) of an aluminum alloy that is electrochemically lower than the core material is bonded to the core material (for example, see Patent Documents 1 and 2).
The sacrificial material used here functions as a sacrificial anode material by using a material that is electrochemically lower than the core material, and can prevent corrosion of the core material.

JP-A-9-295089 JP 2012-117107 A

For the above-mentioned brazing sheet, further reduction in the thickness of the material is required, for example, due to downsizing and high performance of the heat exchanger.
When the thinned material is subjected to the same brazing heat treatment as in the conventional method, the diffusion of Zn added to the sacrificial material into the core material and the diffusion of Cu added to the core material to the sacrificial material and brazing material are performed. Is promoted.
For this reason, there is a problem that the pitting potential difference between the core material on the inner surface side and the outer surface side of the tube is reduced, the corrosion resistance is reduced, and a through-hole is generated in the material at an early stage.

  The present invention has been made in view of the above circumstances, and provides a brazing sheet having high strength and excellent corrosion resistance even when applied to a heat exchanger having a thin brazing structure. The purpose is to:

In order to solve the above-mentioned problem, the present invention is an aluminum alloy brazing sheet in which a sacrificial material is clad on one surface of a core material and a brazing material is clad on the other surface. It consists of an Al-Mn-Si-based aluminum alloy containing 5 to 1.3%, and the sacrificial material is 4.0 to 7.0% Zn, 1.0 to 1.8% Mn, Si in mass%. : 0.2 to 1.2%, the balance being an aluminum alloy consisting of Al and unavoidable impurities, wherein the brazing material is Si: 6.0 to 11.0% and Zn: 0.1 to 3 by mass%. At a pitting potential after a brazing heat treatment of maintaining the target temperature at 590 to 610 ° C. for 1 to 8 minutes at a pitting potential of the brazing sheet in the thickness direction. Pit potential measured along the line Wherein the thickness of the region where the potential difference from the most noble potential of the core material is 100 mV or more is 10% to 50% of the material thickness of the brazing sheet, wherein the thickness is 0.18 mm or less. It relates to an aluminum alloy brazing sheet.

In the present invention, the core material further includes, by mass%, Mn: 0.5 to 1.8%, Si: 0.05 to 1.3%, Fe: 0.05 to 0.5%, and Mg: 0. One or two or more selected from the group consisting of 0.05 to 0.5%, Zr: 0.05 to 0.3%, Ti: 0.05 to 0.3%, and Cr: 0.05 to 0.3%. Further, a composition containing the same can be adopted.
In the present invention, in the pitting potential after the brazing heat treatment, in a region where the potential difference from the most noble potential of the core material is 100 mV or more, the pit sacrificed from the sacrificial material interface in the thickness direction of the core material. When the length of the region is A μm, and the length of the region from the brazing material interface in the thickness direction of the core material is B μm, it is preferable that the relationship of 1 <(A + 1) / (B + 1) <61 be satisfied. .

In the present invention, it is preferable that the potential difference between the pitting potential at the outermost surface of the most noble pitting potential of the core material after brazing heat treatment the sacrificial material is in the range of 160～290MV.
In the present invention, the region having a Zn concentration of 0.2% or less after the brazing heat treatment preferably has a thickness of 20% to 70% of the material plate thickness.

  In the present invention, the chemical composition of the aluminum alloy is made a high corrosion-resistant material corresponding to the thinning of the brazing sheet, and is added to Zn or the core material added to the sacrificial material when a brazing heat treatment suitable for the thin-walled material is performed. The element diffusion state of Cu that has been controlled can be controlled, the pitting potential difference between the sacrificial material and the brazing material and the core material is optimized, and the potential balance between the sacrificial material side and the brazing material side is set to an optimal relationship, thereby making the wall thinner than before. Thus, a brazing sheet having excellent corrosion resistance can be provided.

FIG. 2 is a cross-sectional view of a brazing sheet employed in the heat exchanger according to one embodiment of the present invention. Sectional drawing which shows an example of the tube formed using the brazing sheet shown in FIG. FIG. 2 is a perspective view showing a cross section of a part of a heat exchanger configured using the brazing sheet. 7 is a graph showing the relationship between the distance from the surface of the sacrificial material and the pitting potential in the sample obtained in the example. 9 is a graph showing the relationship between the distance from the surface of the sacrificial material and the pitting potential in the sample obtained in the conventional example. 5 is a graph showing the relationship between the distance from the surface of the sacrificial material and the Zn concentration in the samples obtained in the examples. 7 is a graph showing the relationship between the distance from the surface of a sacrificial material and the Zn concentration in a sample obtained in a conventional example.

Hereinafter, a first embodiment of a brazing sheet according to the present invention will be described with reference to the drawings.
In the drawings used in the following description, in order to emphasize the characteristic portions, the characteristic portions may be enlarged for convenience, and the dimensional ratios of the respective components are not necessarily the same as the actual ones. Absent. In addition, for the same purpose, parts that do not have a characteristic may be omitted in the drawings.

  FIG. 1 is a cross-sectional view of the brazing sheet 1 of the present embodiment. The brazing sheet 1 includes a core material 1a made of an aluminum alloy, a layered brazing material 1b made of an aluminum alloy adhered (cladded and pressed) on one surface of the core material 1a, and a brazing material 1b formed on the other surface of the core material 1a. It is mainly composed of a layered sacrificial material 1c made of an aluminum alloy adhered (cladded and pressed). The brazing sheet 1 shown in FIG. 1 is formed into a B-shape, for example, to form a B-shaped tube 10 shown in FIG. 2, and this tube 10 is assembled, for example, as shown in FIG.

  For example, as shown in FIG. 2, the tube 10 is formed by flattening the brazing sheet 1 with a forming roll into a flat tubular shape so that the sacrificial material 1c is on the inside and the brazing material 1b is on the outside, and the edges of the brazing sheet 1 are butted. A B-shaped tube 10 can be configured as a part.

The heat exchanger 20 has a structure used for, for example, a radiator of an automobile, and generally includes a tube 10, a header 21, an outer fin 22, and a side support 23.
The end of each tube 10 is inserted into a plurality of slots (insertion holes) 21a formed in the header 21 and a plurality of the headers 21 and the tube 10 are connected to each other by using a brazing material 1b disposed around the insertion portion. It is joined by brazing. Further, the tube 10 and the outer fin 22 are joined by brazing each other using a brazing material 1b provided on the brazing sheet 1 constituting the tube 10.
In addition, when forming the tube 10, the brazing of the ends 10A and 10A of the brazing sheet 1 (see FIG. 2), the brazing of the header 21 and the tube 10, and the brazing of the tube 10 and the outer fin 22 are heat exchange. It can be performed at the same time when the container 20 is assembled.

Next, the composition of the core material 1a, the brazing material 1b, and the sacrificial material 1c that constitute the brazing sheet 1 of the present embodiment will be described.
In the brazing sheet 1, the core material 1a is made of an Al-Mn-Si-based aluminum alloy containing 0.5 to 1.3% of Cu by mass%, and the sacrificial material 1c is made of 4.0 to 7% of Zn by mass%. 0.0%, Mn: 1.0 to 1.8%, Si: 0.2 to 1.2%, the balance being an aluminum alloy consisting of Al and unavoidable impurities. It is composed of an aluminum alloy containing 6.0 to 11.0% and Zn: 0.1 to 3.0%, with the balance being Al and unavoidable impurities.
In this specification, when the upper and lower limits of the composition ratio are expressed as 0.5 to 1.3%, the upper and lower limits are included unless otherwise specified. Therefore, 0.5 to 1.3% means a range of 0.5% to 1.3%.

  Regarding the aluminum alloy constituting the core material 1a, in addition to the above composition, Mn: 0.5 to 1.8%, Si: 0.05 to 1.3%, and Fe: 0.05 to 0.5 by mass%. %, Mg: 0.05-0.5%, Zr: 0.05-0.3%, Ti: 0.05-0.3%, Cr: 0.05-0.3% 1 A composition further containing a species or two or more species can be employed.

Hereinafter, each component will be described.
<Core component>
[Cu: 0.5 to 1.3% by mass]
Cu dissolves in the matrix and has the effect of increasing the strength of the aluminum alloy. However, when the Cu content is less than 0.5% by mass, the strength is insufficient, and when the Cu content exceeds 1.3% by mass. Decreases corrosion resistance. For this reason, the Cu content is desirably 0.5 to 1.3% by mass, and more preferably 0.8 to 1.2% by mass.
[Mn: 0.5 to 1.8% by mass]
Mn has the effect of forming Al-Mn-Si-based, Al-Mn-Fe-based, and Al-Mn-Fe-Si-based intermetallic compounds finely in the matrix to increase the material strength. However, if the amount of Mn is less than 0.5% by mass, the effect is not sufficiently exhibited, and if it exceeds 1.8% by mass, a huge intermetallic compound is generated at the time of casting, so that the formability of the material is reduced. For the same reason, the Mn content is more preferably set to 1.0 to 1.75% by mass.

[Si: 0.05 to 1.3% by mass]
Si has the effect of forming an Al-Mn-Si-based or Al-Mn-Fe-Si-based intermetallic compound finely in the matrix and increasing the material strength. However, if the Si content is less than 0.05% by mass, the effect is not sufficiently exhibited, and if it exceeds 1.3% by mass, the melting point of the material is lowered. For the same reason, the Si content is more desirably 0.5 to 1.1% by mass.

[Fe: 0.05 to 0.5% by mass]
Fe forms an Al-Mn-Fe-based or Al-Mn-Fe-Si-based intermetallic compound finely in a matrix, and has the effect of increasing the material strength. However, if the Fe content is less than 0.05% by mass, the castability decreases, and if it exceeds 0.5% by mass, a huge intermetallic compound is generated during casting, and the material formability decreases. For the same reason, the Fe content is more preferably set to 0.2 to 0.4% by mass.

[Mg: 0.05-0.5% by mass]
Mg has an effect of increasing the material strength. However, if the amount of Mg is less than 0.05% by mass, the effect is not sufficiently exhibited, and if it exceeds 0.5% by mass, the brazing property is reduced. For the same reason, the Mg content is more preferably set to 0.1 to 0.4% by mass.
[Zr: 0.05 to 0.3% by mass, Ti: 0.05 to 0.3% by mass, Cr: 0.05 to 0.3% by mass]
Zr, Ti, and Cr contribute to the enhancement of the strength of the aluminum alloy. However, the addition of less than 0.05% by mass individually results in insufficient strength, and the addition of more than 0.3% by mass deteriorates the formability. Become like

<Braze filler ingredient>
The brazing material 1b of the tube 10 contains 6.0 to 11.0% by mass of Si and 0.1 to 3.0% by mass of Zn, and the remainder is made of aluminum and an unavoidable impurity aluminum alloy.
[Si: 6.0 to 11.0 mass%]
Si contained in the brazing filler metal 1b is a component that lowers the melting point and imparts fluidity. If the content is less than 6% by mass, the desired effect is insufficient, and if the content exceeds 11% by mass, On the contrary, it is not preferable because the fluidity is lowered. Therefore, the content of Si in the brazing material 1b is preferably in the range of 6.0 to 11.0% by mass.

[Zn: 0.1 to 3.0% by mass]
Zn has the effect of making the potential of an aluminum alloy base, and when added to the brazing material 1b, the potential difference from the core material 1a increases, and a potential gradient effective for corrosion resistance is formed, thereby improving corrosion resistance and improving corrosion depth. This has the effect of reducing the size. However, if the Zn content is less than 0.1% by mass, the effect is not sufficiently exhibited, and if it exceeds 3.0% by mass, the potential of the brazing material 1b becomes too low.

<Sacrificial material component>
The sacrificial material 1c of the tube 10 contains 4.0 to 7.0% by mass of Zn, 1.0 to 1.8% by mass of Mn, and 0.2 to 1.2% by mass of Si, with the balance being aluminum and It is preferable to use an aluminum alloy having a composition of unavoidable impurities.
[Zn: 4.0 to 7.0% by mass]
Zn has the effect of making the potential of the aluminum alloy base, and when added to the sacrificial material 1c, the potential difference from the core material 1a increases, and a potential gradient effective for corrosion resistance is formed, so that the brazing sheet 1 (that is, the tube 10) is formed. Has the effect of improving the corrosion resistance and reducing the corrosion depth.
However, if the Zn content is less than 4.0% by mass, the effect is not sufficiently exhibited. If the Zn content exceeds 7.0% by mass, the corrosion rate becomes too fast, so that the sacrificial material 1c disappears early, and the corrosion depth is reduced. To increase. For the same reason, the Zn content is more preferably set to 4.5 to 6.5% by mass.
[Mn: 1.0 to 1.8% by mass]
Mn has the effect of forming Al-Mn-Si-based, Al-Mn-Fe-based, and Al-Mn-Fe-Si-based intermetallic compounds finely in the matrix to increase the material strength. However, if the Mn content is less than 1.0% by mass, the effect is not sufficiently exhibited, and if it exceeds 1.8% by mass, a huge intermetallic compound is generated at the time of casting, so that the formability of the material is reduced. For the same reason, the Mn content is more preferably set to 1.1 to 1.75% by mass.

[Si: 0.2 to 1.2 mass%]
Si has the effect of improving the strength of the material by forming a fine Mg-Si compound with Mg. However, if the amount of Si is less than 0.2% by mass, the effect is not sufficiently exhibited, and if it exceeds 1.2% by mass, the melting point of the material decreases. For the same reason, the Si content is more preferably set to 0.4 to 1.0% by mass.

<Permutation of potential>
In the brazing sheet 1 of the present embodiment, the region where the potential difference from the most noble potential of the core material 1 is 100 mV or more in the pitting potential after the brazing heat treatment is 10% to 10% of the material thickness of the brazing sheet 1. It is 50%.
Further, in a region in which the potential difference from the most noble potential of the core material 1a in the pitting potential after the brazing heat treatment is 100 mV or more, a region from the outermost surface of the sacrificial material 1c toward the thickness direction of the core material 1a. Where the length (thickness) is A μm and the length (thickness) of the region from the outermost surface of the brazing material 1b in the plate thickness direction is B μm, the relationship of 1 <(A + 1) / (B + 1) <61 is satisfied. It has been.

FIG. 4 shows an outline of these relationships. FIG. 4 shows a case where the distance from the outermost surface of the brazing sheet 1 is plotted on the horizontal axis and the pitting potential is plotted on the vertical axis, that is, the core material 1a of the brazing sheet 1 and the brazing material along the cross section of the brazing sheet 1. The pitting potential at each position in the thickness direction including the entirety of 1b and the sacrificial material 1c is shown.
The position of the most noble potential of the core 1a is the position of the peak of the curve indicating the pitting potential, and is indicated by a chain line a in FIG. 4, and the position where the potential difference from the noble potential of the core 1a is 100 mV is indicated by a chain line. Indicated by b.
FIG. 4 shows the length (thickness) of the region from the outermost surface of the sacrificial material 1c in the thickness direction of the core 1a in the region where the potential difference from the most noble potential of the core 1a is 100 mV or more. 4, the length (thickness) of the region from the outermost surface of the brazing material 1b toward the plate thickness direction in the region where the potential difference from the most noble potential of the core material 1a is 100 mV or more is shown in FIG. Indicated by In FIG. 4, the left end position of the horizontal axis indicates the outer surface position of the sacrificial material 1c, and the right end position of the curve indicates the outer surface position of the brazing material 1b.
Moreover, the scope of pitting potential difference between the core 1a after the brazing heat treatment the sacrificial material 1b is 160~290mV indicates a range between chain lines a and chain line c in FIG.

The potential gradient of the pitting potential is generated because the element contained in the sacrificial material 1c at the time of brazing is diffused, and in particular, Zn is diffused to generate a potential gradient according to the Zn concentration in the core material 1a. It depends.
The potential gradient shown in FIG. 4 is caused by adjusting the brazing conditions and the like in addition to using the aluminum alloy composition for the core material and the aluminum alloy composition for the sacrificial material described above in the present embodiment. It depends on what you are doing.
By having the potential balance of the pitting potential as described above, the corrosion resistance of the brazing sheet 1 can be improved, and generation of through holes can be prevented.

<Manufacture of brazing sheet>
In order to manufacture the brazing sheet 1 having the above-described configuration, for example, an aluminum alloy ingot for a core material, an aluminum alloy ingot for a sacrificial material, and an aluminum alloy Prepare a lump.
These aluminum alloy ingots can be subjected to, for example, a homogenization treatment of heating at 530 to 600 ° C. for 8 to 16 hours. The ingot is formed into an alloy plate through hot rolling. Further, the alloy plate may be formed through continuous casting and rolling.
These aluminum alloy plates are usually assembled into a clad and clad at an appropriate cladding ratio. Cladding is generally performed by rolling. Thereafter, the aluminum alloy brazing sheet having a desired thickness is obtained by further performing cold rolling. The configuration of the clad material can be, for example, sacrifice material: core material: brazing material = 15%: 75%: 10%. However, the configuration of the clad material is not limited to this. For example, the clad ratio of the sacrificial material may be 17% or 20%.
In the above manufacturing process, intermediate annealing can be interposed in cold rolling. The intermediate annealing can be performed, for example, by heating at 200 to 400 ° C. for about 1 to 6 hours. In the final rolling after the intermediate annealing, rolling is performed at a cold rolling reduction of 10 to 50%. The prepared clad material is subjected to a heat treatment equivalent to brazing in a high purity nitrogen gas atmosphere by a drop method. The heat treatment equivalent to brazing is performed, for example, by heating at a heating rate such that the time required to reach the target temperature from room temperature to 1 to 15 minutes is maintained at the target temperature of 590 to 610 ° C. for 1 to 8 minutes. Can be.

In the brazing sheet 1 having the above-described structure, Zn, Mn, and Si are also specified for the sacrificial material 1c while the core 1a is made of a high-strength material corresponding to a reduction in the thickness, including Mn and Si, with the Cu content being in a specific range. In addition to making the sacrificial material 1c a high-strength material corresponding to a reduction in thickness, the pitting potential balance of the core material is set to a specific relationship based on the relationship between the core material and the sacrificial material. Can also provide a brazing sheet having excellent corrosion resistance.
For this reason, when a heat exchanger is configured using the above-described brazing sheet, a heat exchanger that is thin, lightweight, and excellent in corrosion resistance can be provided.
In the configuration described above, the potential balance as shown in FIG. 4 can be achieved by optimizing the brazing heat treatment conditions. Specifically, by raising the temperature and cooling during the brazing heat treatment in a shorter time than in the past, it is possible to suppress the heat input applied to the material and to suppress the diffusion of elements, as shown in FIG. Such a prescribed potential balance can be realized.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
<Preparation of test material>
An aluminum alloy for a core material, an aluminum alloy for a sacrificial material, and an aluminum alloy for a brazing material were cast by semi-continuous casting. The composition of the aluminum alloy for the core material and the test material No. are shown in Table 1, the composition of the aluminum alloy for the sacrificial material and the test material No. are shown in Table 2, and the composition of the aluminum alloy for the brazing material is shown in Table 3. Shown in

  The obtained core material was homogenized at 580 ° C. for 8 hours. The conditions for this homogenization treatment are merely examples, and can be selected from the range of a temperature of 530 to 600 ° C. and a holding time of 8 to 16 hours. Further, the sacrificial material and the brazing material were not subjected to the homogenizing treatment.

  Next, a sacrificial material was combined on one surface of the core material, and a brazing material was combined on the other surface, followed by hot rolling to form a clad material, and then cold rolling was performed. Then, intermediate annealing was performed at 330 ° C. for 4 hours, and a 0.18 mm-thick H14 tempered clad material (test material) was prepared by final cold rolling at a predetermined rolling reduction. The configuration of the clad material was as follows: sacrificial material: core material: brazing material (thickness) = 15%: 75%: 10%. In the clad material, the material thickness of the core material before the heat treatment equivalent to brazing is 135 μm, the thickness of the brazing material is 18 μm, and the thickness of the sacrificial material is 27 μm. However, the intermediate annealing can be selected from the range of temperature: 200 to 380 ° C. and holding time: 1 to 6 hours.

  For the clad material, the arrival time from room temperature to 400 ° C. is 1 minute 30 seconds to 2 minutes 30 seconds, the arrival time from 400 ° C. to 550 ° C. is 30 seconds to 1 minute 30 seconds, and the arrival time from 550 to the target temperature is 30 minutes. Heating at a heating rate such that the heating time is from 1 second to 1 minute and 30 seconds, holding at a target temperature of 600 ° C. for 1 minute, then cooling to 300 ° C. at about 100 ° C./min, and then air cooling to room temperature. A considerable heat treatment was applied. At this time, when the brazing time is t and the diffusion coefficient of Zn is D, the heat input given by ΔDt is 13 to 23. By this heat treatment, the brazing material receives a considerable amount of heat at the time of brazing and melts, and at the same time, the element is diffused from the sacrificial layer, and the element mainly composed of Zn is diffused to the core material side.

  Through the above steps, the brazing sheets of Sample Nos. 1 to 22 were produced. Table 4 shows the core material type, sacrificial material type, and brazing material type of the brazing sheets of Sample Nos. 1 to 22. In Tables 1 to 3, the balance of the elements described is Al and unavoidable impurities. Table 4 below summarizes the results of evaluating the internal corrosion resistance, external corrosion resistance, and moldability of each test material.

"Internal corrosion resistance"
A 30 × 50 mm sample was cut out from the test material after the heat treatment equivalent to brazing, and on the sacrificial material side, in an aqueous solution containing Cl ⁻ : 195 ppm, SO ₄ ²⁻ : 60 ppm, Cu ²⁺ : 1 ppm, and Fe ³⁺ : 30 ppm An immersion test was performed for 8 weeks with a cycle of 80 ° C. × 8 hours → room temperature × 16 hours. After the corrosion test, the sample was immersed in a boiling chromic acid mixed solution to remove corrosion products, the cross-section of the maximum corroded portion was observed, and the corrosion depth was measured. The result was taken as the internal corrosion resistance. Those having a corrosion depth of 35 μm or less were evaluated as ◎, those having a corrosion depth of more than 35 μm and 50 μm or less were evaluated as 、, those having a corrosion depth of more than 50 μm and 90 μm or less were evaluated as Δ, and those with a depth of more than 90 μm were evaluated as x did.

"External corrosion resistance"
The external corrosion resistance was determined by cutting a 30 × 100 mm sample from the test material after the heat treatment equivalent to brazing, and performing a SWAAT test defined by ASTM G85-A3 on the brazing material side for 500 hours. After the corrosion test, the sample is immersed in a boiling chromic phosphate mixed solution to remove corrosion products, the cross section of the maximum corroded portion is observed, and the corrosion depth is measured. The result is defined as external corrosion resistance. Those having a corrosion depth of 35 μm or less were evaluated as ◎, those having a corrosion depth of more than 35 μm and 50 μm or less were evaluated as 、, those having a corrosion depth of more than 50 μm and 90 μm or less were evaluated as Δ, and those with a depth of more than 90 μm were evaluated as x did.
"Moldability"
The test material before the heat treatment equivalent to brazing was processed into a B-shaped tube shape with the sacrificial material on the inside. The cross section of the processed tube was embedded in resin, the shape of the inner column was observed with an optical microscope, and the deviation from the intended shape (dimension) was measured. Those whose deviation from the intended size was 10 μm or less were evaluated as ◎, those which were more than 10 μm and 15 μm or less were evaluated as ○, those which were more than 15 μm and 20 μm or less were evaluated as Δ, Those having a diameter of more than 20 μm were evaluated as x.

Hereinafter, characteristics of each sample of the brazing sheet shown in Table 4 will be described.
Sample No. Nos. 1 to 19 are test materials in which the potential difference balance in the thickness direction of the brazing sheet is within the range targeted by the present invention.
That is, in the pitting potential after the brazing heat treatment, when the pitting potential is measured along the thickness direction of the brazing sheet, the thickness of the region where the potential difference from the most noble potential of the core material is 100 mV or more, It is 10% to 50% of the material thickness of the brazing sheet.

Further, the core material is 0.5% to 1.3%, Mn: 0.5% to 1.8%, Si: 0.05% to 1.3%, and Fe: 0.05% to 0.5% by mass%. %, Mg: 0.05-0.5%, Zr: 0.05-0.3%, Ti: 0.05-0.3%, Cr: 0.05-0.3% 1 Consisting of an Al-Mn-Si-based aluminum alloy further containing one or more species, wherein the sacrificial material is 4.0% to 7.0% Zn, 1.0% to 1.8% Mn, and Si: An aluminum alloy containing 0.2 to 1.2%, with the balance being Al and unavoidable impurities. The brazing filler metal is 6.0 to 11.0% by mass and Zn: 0.1 to 3.0 by mass%. %, With the balance being an aluminum alloy consisting of Al and unavoidable impurities.
In a region where the potential difference from the most noble potential of the core material in the pitting potential after the heat treatment equivalent to brazing is 100 mV or more, the length of the region from the outermost surface of the sacrificial material toward the thickness direction of the core material is considered. When the length is A μm and the length of the region from the outermost surface of the brazing material in the thickness direction of the core material is B μm, the relationship of 1 <(A + 1) / (B + 1) <61 is maintained.
Further, the pitting potential difference between the core material and the sacrificial material after the heat treatment equivalent to brazing is set in the range of 160 to 290 mV.
In the brazing sheet after the heat treatment equivalent to brazing, the region with a Zn concentration of 0.2% or less is in the range of 20% to 70% of the material plate thickness of the brazing sheet.
A brazing sheet that satisfies these potential balances is, for example, a potential balance having an upwardly convex curve shown in FIG. 4, and a curve in which the pitting potential at both ends of the convex curve suddenly decreases. It has become.

The test material of No. 14 is an example in which only the length of the region having a potential difference of 100 μm or more from the core material is slightly smaller than the desired range (16 to 90 μm), but the internal corrosion resistance is slightly reduced, but the external corrosion resistance is good. The moldability was excellent.
In the test material of No. 15, since the value of A + 1 / B + 1 was slightly smaller than the desirable range (1-61), the internal corrosion resistance tended to slightly decrease, but the external corrosion resistance and moldability were good.
The test material of No. 16 was an example in which the pitting potential difference between the core material and the sacrificial material was slightly smaller than the desired range (160 to 290 mV), but the internal corrosion resistance and the external corrosion resistance were good, and the moldability was excellent. .
The test material of No. 17 had a region with a Zn concentration of 0.2% or less slightly shorter than the desired range (36 to 16 μm), but had excellent external corrosion resistance and moldability, and also had good internal corrosion resistance.
In the sample of No. 18, only the length of the region where the potential difference from the core material was 100 μm or more was a desirable range, but the value of A + 1 / B + 1 was slightly smaller than the desirable range, and the pitting potential difference between the core material and the sacrificial material was less than the desirable range. Although the length was slightly smaller and the length of the region with a Zn concentration of 0.2% or less was slightly shorter than the desired range, the moldability was good although the internal corrosion resistance and external corrosion resistance were slightly reduced.
In the test material of No. 19, the length of the region having a potential difference of 100 μm or more from the core material and the value of A + 1 / B + 1 are within a desirable range, but the pitting potential difference between the core material and the sacrificial material is slightly smaller than the desirable range. Although the length of the region having a concentration of 0.2% or less was slightly shorter than the preferred range, the external corrosion resistance and moldability were good, and the internal corrosion resistance tended to slightly decrease.

In contrast to these test materials, in the test material of No. 20, the Mn content of the core material was too low below the desired range, the Mn content of the sacrificial material was too low below the desired range, and the Zn content of the brazing material was low. The amount was too high above the desired range, resulting in poor external corrosion resistance.
In the test material of No. 21, the Mn content of the core material was too high than the desired range, the Mn content of the sacrificial material was too high than the desired range, and the Zn content of the brazing material was too low below the desired range. Therefore, the result was inferior in moldability.
In the test material of No. 22, the Si content of the core material was too high than the desired range, the Si content of the sacrificial material was too low of the desired range, and the Si content of the brazing material was too high of the desired range. Therefore, the core material was melted during the heat treatment equivalent to brazing.

In the test material of No. 23, the Fe content of the core material was too high than desired, the Si content of the sacrificial material was too high, and the Si content of the brazing material was too low. Therefore, the sacrificial material melted during the heat treatment equivalent to brazing.
In the test material of No. 24, the Mg content of the core material was too high than the desired range, the Mn content of the sacrificial material was too low below the desired range, and the Si content of the brazing material was too low below the desired range. Therefore, the result was inferior in moldability.
In the test material of No. 25, the Zr, Ti, and Cr contents of the core material were too high than the desired range, the Zn content of the sacrificial material was too low than the desired range, and the Si content of the brazing material was the desired range. It was too high, resulting in poor internal corrosion resistance.

For the test material of No. 26, the Cu content of the core material was too low below the desired range, and the Mn content of the sacrificial material was too high of the desired range, resulting in poor internal and external corrosion resistance. Was.
In the test material of No. 27, the Cu content of the core material was too high than the desired range, and the Mn content of the sacrificial material was too low than the desired range, resulting in poor internal and external corrosion resistance. Was.
The test material of No. 28 is thinner, since the thickness of the region where the potential difference from the most noble potential of the core material is 100 mV or more is out of the range of 10% to 50% of the material thickness of the core material. Too much, and too much Mn content resulted in poor internal corrosion resistance and moldability.

In the test material of No. 29, the value of A + 1 / B + 1 was slightly smaller than the desired range, and the Mn content was too large, resulting in poor internal corrosion resistance and moldability.
The test material of No. 30 had the pitting potential difference between the core material and the sacrificial material after the brazing heat treatment was not in the range of 160 to 290 mV, and was too small, and the Mn content was too large, so that the internal corrosion resistance was high. And inferior moldability.
The test material of No. 31 was inferior in both the internal corrosion resistance and the external corrosion resistance because the thickness of the region where the Zn concentration was 0.2% or less was small. FIG. 7 shows an example of a region having a Zn concentration of 0.2% or less as in this test material. As shown in FIG. It preferably occupies a range of 20 to 70% of the thickness.

The test material of No. 32 is a conventional brazing sheet, but the thickness of the region where the potential difference from the most noble potential of the core material is 100 mV or more is insufficient, and the pitting potential difference between the core material and the sacrificial material is low. Since the thickness is not within the range of 160 to 290 mV, which is too small, and the thickness of the region having a Zn concentration of 0.2% or less is small, both the internal corrosion resistance and the external corrosion are inferior.
FIG. 5 shows the distribution of the pitting potential of this test material. The difference from the distribution of the pitting potential of the test material according to the present invention shown in FIG. 4 is apparent.
The test material of No. 33 was a sample in which the Cu content of the core material was low, and the test material of No. 34 was a sample in which the Zn content of the sacrificial material was low, but all samples had poor internal corrosion resistance. The result was. Although the test material of No. 35 was a sample in which the Zn content of the brazing material was small, the result was inferior in external corrosion resistance.

  DESCRIPTION OF SYMBOLS 1 ... Brazing sheet, 1a ... Core material, 1b ... Brazing material, 1c ... Sacrificial material, 10 ... Tube, 20 ... Heat exchanger, 21 ... Header, 22 ... Outer fin, 23 ... Side support.

Claims (5)

An aluminum alloy brazing sheet in which a sacrificial material is clad on one surface of a core material and a brazing material is clad on the other surface, wherein the core material contains 0.5 to 1.3% by mass of Cu. The sacrificial material is composed of a Mn-Si-based aluminum alloy and contains 4.0 to 7.0% of Zn, 1.0 to 1.8% of Mn, and 0.2 to 1.2% of Si in mass%. The balance is made of an aluminum alloy consisting of Al and inevitable impurities. The brazing material contains Si: 6.0 to 11.0% and Zn: 0.1 to 3.0% by mass, and the balance is Al and inevitable. Made of aluminum alloy consisting of impurities,
When the pitting potential is measured along the thickness direction of the brazing sheet at the pitting potential after the brazing heat treatment held at the target temperature of 590 to 610 ° C for 1 to 8 minutes , the most noble potential of the core material and Wherein the thickness of the region where the potential difference is 100 mV or more is 10% to 50% of the material thickness of the brazing sheet, wherein the thickness of the aluminum alloy brazing sheet is 0.18 mm or less.   The core material further contains, by mass%, Mn: 0.5 to 1.8%, Si: 0.05 to 1.3%, Fe: 0.05 to 0.5%, and Mg: 0.05 to 0. Aluminum further containing one or more selected from 5%, Zr: 0.05 to 0.3%, Ti: 0.05 to 0.3%, Cr: 0.05 to 0.3% The aluminum alloy brazing sheet according to claim 1, comprising an alloy.   In the pitting potential after the brazing heat treatment, in the region where the potential difference from the most noble potential of the core material is 100 mV or more, the length of the region from the outermost surface of the sacrificial material toward the thickness direction of the core material 3. The relationship of 1 <(A + 1) / (B + 1) <61 when the length of the region from the outermost surface of the brazing material in the thickness direction of the core material is B μm. The aluminum alloy brazing sheet according to 1. Any of claims 1 to 3 in which the potential difference between the pitting potential at the outermost surface of the most noble pitting potential of the core material after brazing heat treatment the sacrificial material is characterized in that in the range of 160~290mV An aluminum alloy brazing sheet according to any one of the preceding claims.   5. The aluminum according to claim 1, wherein a region having a Zn concentration of 0.2% or less after the brazing heat treatment is 20% to 70% of a material thickness of the brazing sheet. 6. Alloy brazing sheet.

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