JP2020100881A - Aluminum alloy clad material for heat exchanger, and heat exchanger - Google Patents

Abstract

To provide an aluminum alloy clad material for a heat exchanger, capable of improving corrosion resistance, and to provide a heat exchanger.SOLUTION: An aluminum alloy clad material for a heat exchanger, comprising an Al-Mn-based core material, and Al-Si-Zn brazing filler metals is such that: the brazing filler metals comprise an aluminum alloy which has a composition of containing by mass%, Si, 2.0% or more and 5.0% or less, and Zn, 0.2% or more and 7.0% or less, and having the balance Al with inevitable impurities; an average crystal grain size of the Al-Mn-based core material quickly chilled after heating the brazing filler metals up to 570°C is 500 μm or more in the major axis direction; an average shape ratio in a cross section parallel to a rolling direction is 4.5 or more; an eutectic Si grain in the brazing filler metals after brazing corresponding heat treatment is 2.0 μm or less at a circle equivalent diameter; a ratio of an area occupied by eutectic brazing filler metals from the boundary face between the brazing filler metals and the Al-Mn-based core material to a plate thickness center part of the brazing filler metals is 10% or less; and a thickness of the remaining brazing filler metals is 45 μm or more.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to an aluminum alloy clad material for a heat exchanger and a heat exchanger used as a part for a heat exchanger of an automobile or the like.

In recent years, with the advent of environment-friendly vehicles typified by electric vehicles and fuel cell vehicles, there is an increasing demand for automobile heat exchangers with higher performance and more complicated shapes than ever before. For this reason, in the heat exchanger cooling water side where a sacrificial material has been conventionally applied to secure corrosion resistance, there are an increasing number of cases where brazing is applied, and it is possible to achieve both jointability and corrosion resistance on the cooling water side. A brazing material is required.

For example, in the heat exchanger manufacturing method described in Patent Document 1, as an aluminum clad plate material, one side of a core material is clad with an Al—Si brazing material, and the other side is Si: 2.5 to 6.0 mass %. When using a clad plate material obtained by clad an aluminum alloy material containing Al, at the time of brazing, in the vicinity of the end of the assembled clad plate material, the molten brazing material from the Al-Si based brazing material clad on one side is clad plate material. The joining portion is formed by flowing from the end portion to the aluminum alloy material surface clad on the other surface. Further, this aluminum alloy material contains Zn in an amount of 1.5 to 6.0% and has a function as a sacrificial anode layer.

The aluminum alloy brazing sheet described in Patent Document 2 includes an aluminum alloy core material and a brazing function imparting sacrificial material that is clad on at least one surface of the core material, and the core material contains Mn and Fe and the balance Al. And the brazing function-providing sacrificial material contains Si, Zn, Fe and the balance Al and inevitable impurities, and the brazing function-providing sacrificial material has a clad ratio of 3 to 25%. As the metallographic structure before applying heat, the core material is a fibrous structure and the brazing function imparting sacrificial material is a recrystallized structure.
Zn is added to the aluminum alloy material and the sacrificial material imparting a brazing function (hereinafter, referred to as a brazing material) described in Patent Documents 1 and 2 in order to improve corrosion resistance. The potential gradient is secured.

JP, 2007-178062, A JP, 2014-114475, A

However, in the configurations described in Patent Documents 1 and 2, since the brazing material flows during the brazing heat treatment, Zn is not uniformly distributed on the material surface, and the brazing material eutectic part is locally corroded. It is difficult to obtain corrosion resistance comparable to that of the sacrificial material as it progresses. Specifically, since the brazing filler metal has a primary crystal (brazing filler metal primary crystal) and a eutectic structure (eutectic brazing filler metal), local corrosion occurs in the core material direction instead of planar corrosion like the sacrificial material. easy.
From the above viewpoints, it is desired to improve the corrosion resistance of the aluminum alloy clad material for heat exchangers having the brazing material on both sides or one side of the core material.

An object of the present invention is to provide an aluminum alloy clad material for a heat exchanger and a heat exchanger that can improve corrosion resistance.

In view of the above problems, the present inventors have optimized the amount of brazing filler metal that flows during brazing heat treatment, increase the thickness of the brazing filler metal that acts as an anticorrosion layer on the material surface after brazing, and use aluminum for heat exchangers. It was found that by increasing the recrystallized grain size during brazing in the core material of the alloy clad material, the eutectic braze can be widely distributed near the surface layer of the material in the brazing material structure after brazing heat treatment. It was

That is, the aluminum alloy clad material for a heat exchanger of the present invention is an aluminum alloy clad material for a heat exchanger, which comprises an Al-Mn-based core material and an Al-Si-Zn brazing material laminated on one surface or both surfaces thereof. The Al-Si-Zn brazing material contains, by mass%, Si: 2.0% or more and 5.0%, Zn: 0.2% or more and 7.0% or less, and the balance from Al and unavoidable impurities. The Al-Mn-based brazing material, which is made of an aluminum alloy having the following composition and is obtained by heating the Al-Si-Zn brazing material to 570[deg.] C. and quenching, has an average crystal grain size of 500 [mu]m or more in the major axis direction and is parallel to the rolling direction. The average shape ratio, which is a value obtained by dividing the major axis in the rolling direction of each crystal grain in the cross section by the minor axis in the plate thickness direction, is 4.5 or more, and the eutectic Si in the Al-Si-Zn brazing material after the heat treatment equivalent to brazing is performed. The particles have a circle equivalent diameter of 2.0 μm or less, and, in a cross-section parallel to the rolling direction, from the interface between the Al—Si—Zn brazing material and the Al—Mn-based core material to the Al—Si—Zn brazing material. The area ratio occupied by the eutectic braze in the region up to the center of the plate thickness is 10% or less, and the thickness of the remaining braze is 45 μm or more.

In the present invention, an Al-Mn-based core material is used as the core material of the aluminum alloy clad material for the heat exchanger, and Mn contained in this core material improves the strength of the core material. Further, an Al—Si—Zn brazing material is used as a brazing material for the aluminum alloy clad material for the heat exchanger, and Si has a function of improving brazing property. If Si is less than 2.0% by mass, the effect is not sufficiently exhibited, and if it exceeds 5.0% by mass, the fluidity of the molten brazing material during brazing becomes too high and remains after brazing. The thickness of the brazing material layer (residual brazing material) is reduced to less than 45 μm. Moreover, the more preferable range of Si is 2.5 mass%-3.5 mass %. Zn has a function of making the brazing material a base electric potential with respect to the core material to prevent corrosion of the core material. If Zn is less than 0.2% by mass, the effect is not sufficiently exerted, and if it exceeds 7.0% by mass, the corrosion rate becomes too fast and the brazing material layer is corroded and consumed at an early stage. Is reduced. Moreover, the more preferable range of Zn is 2.0 mass%-5.0 mass %.

Further, since the eutectic Si particles of the Al—Si—Zn brazing material after the brazing-corresponding heat treatment are as small as 2.0 μm or less, the cathode reaction is suppressed and the corrosion resistance is improved as compared with the case where the eutectic Si particles are large. .. If the eutectic Si particles exceed 2.0 μm, the effect of improving corrosion resistance cannot be exhibited.
Furthermore, the average crystal grain size (recrystallized grain size) of the Al-Mn-based core material obtained by heating the Al-Si-Zn brazing material after the heat treatment equivalent to brazing to 570[deg.] C. and quenching is 500 [mu]m or more in the major axis direction, In addition, since the average shape ratio of each crystal grain in the cross section parallel to the rolling direction is coarsened to 4.5 or more, in the Al-Si-Zn brazing filler metal structure after the equivalent brazing heat treatment, the eutectic brazing material has its surface layer portion. It can be widely distributed in the vicinity. The average crystal grain size of the Al-Mn-based core material immediately before melting of the brazing filler metal is less than 500 μm in the major axis direction, or the average shape ratio of each crystal grain in the cross section parallel to the rolling direction is less than 4.5. In addition to the above cases, if the thickness of the remaining solder is less than 45 μm, the above effect cannot be sufficiently exhibited.

When the brazing heat treatment is performed on the aluminum alloy clad material for a heat exchanger, which is made of the Al-Mn-based core material and the Al-Si-Zn brazing material as described above, the Al-Si-Zn brazing material is formed in the rolling direction parallel cross section. The area ratio of the eutectic braze in the region from the interface between the material and the Al-Mn-based core material to the central portion of the plate thickness of the Al-Si-Zn brazing material is 10% or less. That is, in the brazing material, a structure in which the eutectic brazing material and the brazing material primary crystal have a two-layer structure is obtained, the eutectic brazing material is arranged on the surface layer, and the brazing material primary crystal is arranged on the interface side between the core material and the brazing material. Will be done. As a result, when the brazing filler metal is exposed to the corrosive environment on the cooling water side, after the eutectic brazing filler metal in the surface layer preferentially corrodes, the brazing filler metal primary crystal underneath corrodes uniformly and a general corrosion form is obtained. The corrosion resistance is improved.

In a preferred embodiment of the aluminum alloy clad material for a heat exchanger of the present invention, the Al-Si-Zn brazing material is, by mass%, Sr: 0.01% or more and 0.10% or less, Bi: 0.01% or more. One or two of 0.30% or less, Mn: 0.1% or more and 1.0% or less, and Fe: 0.1% or more and 1.0% or less may be further contained.

By making the eutectic Si particles in the brazing material fine, Sr suppresses the cathode reaction and improves the corrosion resistance as compared with the case where the eutectic Si particles after the brazing heat treatment are large. If Sr is less than 0.01% by mass, the effect is not sufficiently exhibited, and if it exceeds 0.1% by mass, a huge intermetallic compound is likely to be formed during casting, and rolling becomes difficult. For the same reason, the more preferable range is 0.02 mass% or more and 0.05 mass% or less.
Bi has the effect of reducing the surface tension of the molten braze and improving the fluidity of the molten braze, and also improves the bondability even in braze having a low Si concentration. If Bi is less than 0.01% by mass, the effect is not sufficiently exhibited, and if it exceeds 0.3% by mass, a huge intermetallic compound is likely to be formed during casting, and rolling becomes difficult. For the same reason, a more preferable range is 0.10 mass% or more and 0.20 mass% or less.
Mn and Fe suppress the fluidity of the molten wax and improve the corrosion resistance. When Mn and Fe are less than 0.1% by mass, the effect is not sufficiently exhibited, and when Mn and Fe exceed 1.0% by mass, the starting point of the cathode is caused and the corrosion resistance is deteriorated. For the same reason, a more preferable range is 0.2 mass% or more and 0.6 mass% or less.

The heat exchanger of the present invention includes a liquid channel through which a liquid flows, and a cooling water channel that is disposed adjacent to the liquid channel and through which cooling water that cools the liquid flows, the liquid channel Also, the plate for partitioning the cooling water flow path is made of an aluminum alloy clad material for a heat exchanger, which is composed of an Al—Mn-based core material and an Al—Si—Zn brazing material bonded to one surface or both surfaces thereof, The aluminum alloy clad material for an exchanger contains the above Al-Si-Zn brazing material in mass%, contains Si: 2.0% or more and 5.0%, Zn: 0.2% or more and 7.0% or less, and the balance. Is an aluminum alloy having a composition of Al and unavoidable impurities, the Si particles in the Al-Si-Zn brazing material have a circle equivalent diameter of 2.0 μm or less, and the Al-Si-Zn brazing material has a cross section parallel to the rolling direction. Area ratio of the eutectic braze in the region from the interface between the Al-Mn-based core material and the Al-Si-Zn brazing material to the center of the plate thickness is 10% or less, and the thickness of the remaining brazing material is 45 μm. That is all.

In the present invention, since the corrosion resistance of the plates constituting the heat exchanger is improved, the corrosion resistance (durability) of the heat exchanger can be improved.

According to the present invention, the corrosion resistance of the aluminum alloy clad material for a heat exchanger and the heat exchanger can be improved.

It is sectional drawing which shows the heat exchanger using the aluminum alloy clad material for heat exchangers which concerns on embodiment of this invention. It is an enlarged view near the surface of the plate of the aluminum alloy clad material for heat exchangers shown in FIG.

Hereinafter, an embodiment of an aluminum alloy clad material for a heat exchanger and a heat exchanger using the aluminum alloy clad material for a heat exchanger according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, a heat exchanger 1 using an aluminum alloy clad material for a heat exchanger (hereinafter, also simply referred to as a clad material) according to the present invention has a plurality of plates each formed in substantially the same shape. 4, 5, an upper plate 2, a lower plate 3, a cooling water inflow pipe 6, a cooling water outflow pipe 7, and an inner fin 8.

The plates 4 and 5 are alternately laminated to each other to form a space in the center thereof, and the inner fin 8 is arranged in the space. Each of the plates 4 and 5 divides a liquid channel 81 through which a liquid (for example, oil) flows and a cooling water channel 82 through which cooling water flows. Further, in the outer peripheral portion of the plate 4, liquid flow channels 41 through which liquid flows and cooling water flow channels 42 through which cooling water flows are alternately arranged.

Each of the plates 4 and 5 and the inner fins 8 constituting the heat exchanger 1 is made of the aluminum alloy clad material for a heat exchanger according to the present invention, and these are joined by brazing. In addition, in the following description, since the composition is the same, only the plate 4 will be described.

FIG. 2 is an enlarged sectional view of the vicinity of the surface of the plate 4 after brazing.
The plate 4 corresponds to the aluminum alloy clad material for a heat exchanger of the present invention, and the plate 4 after the brazing heat treatment has an interface between the brazing material 4b and the core material 4a in a cross section in the rolling direction, as shown in FIG. The area ratio of the eutectic braze E3 in the region Ar1 from E1 to the center of the plate thickness of the brazing material 4b is 10% or less. In other words, the area ratio of the brazing filler metal primary crystal E2 in the region Ar1 is 90% or more. Further, the area ratio of the eutectic brazing material E3 in the region Ar2 from the surface of the brazing material 4b to the center of the plate thickness of the brazing material 4b is 30% or less, and the area ratio of the brazing material primary crystal E2 is 70% or less. %, and the eutectic brazing filler metal E3 is widely distributed in the vicinity of the surface layer of the brazing filler metal 4b.

That is, in the brazing filler metal 4b, a structure in which the eutectic brazing filler metal E3 and the brazing filler metal primary crystal E2 have a two-layer structure is obtained, the eutectic brazing filler metal E3 is arranged in the surface layer, and the interface E1 side between the core material 4a and the brazing filler metal 4b is provided. The brazing filler metal primary crystal E2 is to be arranged. As a result, when the brazing filler metal 4b is exposed to the corrosive environment on the cooling water side, after the eutectic brazing filler metal E3 in the surface layer is preferentially corroded, the brazing filler metal primary crystal E2 therebelow is uniformly corroded, and the general corrosion Morphology is obtained and corrosion resistance is improved.

The plate thickness of the core material 4a and the clad ratio of the brazing material 4b are not particularly limited, but when used as a plate material for an aluminum laminated oil cooler, the core material 4a has a plate thickness of 0. It is preferable that the brazing material 4b has a cladding ratio of 3 mm or more and 0.6 mm or less, a cladding rate of 5% or more and 15% or less (one surface), and the brazing material 4b has a thickness of 45 μm or more. This allows the thickness of the remaining brazing material to be 45 μm or more.

[Composition of core material]
In this embodiment, an Al-Mn-based core material is used as the core material 4a, and Mn contained in this core material 4a improves the strength of the core material. Specifically, it is preferable that the aluminum alloy contains Mn in the range of 1.0% by mass or more and 2.0% by mass or less, and the balance of Al and unavoidable impurities. In addition, the core material 4a may contain Cu in the range of 0.3 mass% or more and 1.2 mass% or less, and may further contain Zr in the range of 0.02 mass% or more and 0.20% or less.
In the core material 4a, Cu has a function of improving the strength of the core material similarly to Mn, and Zr has a function of improving the strength of the core material and suppressing erosion due to coarsening of crystal grains.

The core material 4a has an average crystal grain size (recrystallized grain size) of the core material 4a, which is obtained by heating the brazing material 4b after the heat treatment equivalent to brazing to 570° C. and quenching, is 500 μm or more in the major axis direction, and is parallel to the rolling direction. The average shape ratio, which is a value obtained by dividing the major axis in the rolling direction of each crystal grain in the cross section by the minor axis in the plate thickness direction, is set to 4.5 or more. That is, by coarsening the crystal grains of the core material 4a, the eutectic brazing material E3 can be widely distributed in the vicinity of the surface layer portion in the structure of the brazing material 4b after the brazing heat treatment. In addition, when the average crystal grain size of the core material 4a is less than 500 μm in the major axis direction, or when the average shape ratio of each crystal grain in the cross section parallel to the rolling direction is less than 4.5, the brazing after the brazing heat treatment is performed. In material 4b, eutectic braze E3 cannot be distributed in the vicinity of the surface layer portion.

[Composition of brazing material]
In the present embodiment, an Al-Si-Zn brazing material is used as the brazing material 4b, Si is 2.0% by mass or more and 5.0% by mass or less, and Zn is 0.2% by mass or more and 7.0% by mass or less. It is preferable that the aluminum alloy is contained in the range of, and the balance is aluminum alloy having a composition of Al and inevitable impurities.
In the brazing material 4b, when Si is less than 2.0 mass%, the addition amount is small, so that a brazing defect easily occurs, and when Si is more than 5.0 mass%, the molten brazing material during brazing Of the brazing filler metal layer (residual brazing material) remaining after brazing may be reduced to less than 45 μm. Moreover, the more preferable range of Si is 2.5 mass%-3.5 mass %. Further, Zn has a function of making the brazing material 4b a base electric potential with respect to the core material 4a to prevent corrosion of the core material. If Zn is less than 0.2% by mass, the effect is not sufficiently exerted, and if it exceeds 7.0% by mass, the corrosion rate becomes too fast and the brazing material layer is corroded and consumed at an early stage. Is reduced. Further, a more preferable range of Zn is 2.0% by mass to 5.0% by mass.

Further, since the eutectic Si particles in the brazing material 4b after the brazing-corresponding heat treatment have a circle equivalent diameter of 2.0 μm or less, the cathodic reaction is suppressed as compared with the case where the brazing-corresponding heat-treating equivalent eutectic Si particles are large. Being improved in corrosion resistance. If the eutectic Si particles exceed 2.0 μm, the effect of improving corrosion resistance cannot be exhibited.

Although the brazing material 4b is made of an Al—Si—Zn brazing material, the brazing material 4b contains 0.01 mass% or more and 0.10 mass% or less of Sr and 0.01 mass% or more and 0% of Bi. 30% by mass or less, 0.1% by mass or more and 1.0% by mass or less of Mn, and 0.1% by mass or more and 1.0% by mass or less of Fe may be further contained. ..
By making the eutectic Si particles in the brazing material fine, Sr suppresses the cathode reaction and improves the corrosion resistance as compared with the case where the eutectic Si particles after the brazing heat treatment are large. If Sr is less than 0.01% by mass, the effect is not sufficiently exhibited, and if it exceeds 0.1% by mass, a huge intermetallic compound is likely to be formed during casting, and rolling becomes difficult. For the same reason, the more preferable range is 0.02 mass% or more and 0.05 mass% or less.

Bi has the effect of reducing the surface tension of the molten braze and improving the fluidity of the molten braze, and also improves the bondability even in braze having a low Si concentration. If Bi is less than 0.01% by mass, the effect is not sufficiently exhibited, and if it exceeds 0.3% by mass, a huge intermetallic compound is likely to be formed during casting, and rolling becomes difficult. For the same reason, a more preferable range is 0.10 mass% or more and 0.20 mass% or less.
Mn and Fe suppress the fluidity of the molten wax and improve the corrosion resistance. When Mn and Fe are less than 0.1% by mass, the effect is not sufficiently exhibited, and when Mn and Fe exceed 1.0% by mass, the starting point of the cathode is caused and the corrosion resistance is deteriorated. For the same reason, a more preferable range is 0.2 mass% or more and 0.6 mass% or less.

[Method for producing aluminum alloy clad material for heat exchanger]
Next, a method for manufacturing the aluminum alloy clad material for heat exchanger will be described.
First, an aluminum alloy for core material (for example, JIS A3003 alloy) and an aluminum alloy for brazing material (Al-Si-Zn alloy) are cast by melt casting, and the obtained ingot is homogenized at a predetermined temperature.
The homogenization treatment of the core material can be selected from the range of 400°C to 600°C for 5 to 15 hours.

The homogenization treatment of the brazing material is performed at 400 to 550° C. for 1 to 5 hours. Usually, in the process of producing aluminum alloy clad material (brazing sheet) for heat exchangers, it is general that the brazing filler metal layer is not subjected to homogenization treatment. There are many Si particles having an equivalent circle diameter of about 1 μm. In order to control the Si particle size in the brazing material layer, homogenization treatment is effective, and can be selected from the range of 400 to 550°C for 1 to 5 hours, and 2 to 4 at 480 to 550°C. More preferably, it is carried out within the range of time.

The ingots of the aluminum alloy for the core material and the aluminum alloy for the brazing material, which have been subjected to the homogenization treatment, are each hot-rolled to be an alloy plate. Alternatively, the alloy sheet may be formed by continuous casting and rolling without dividing the casting step and the rolling step. Since the reduction amount in this hot rolling affects the eutectic Si particle size, the total reduction amount is set to 40% or more.
Then, these alloy plates are clad at an appropriate clad ratio. The clad is generally made by rolling. Then, by further cold rolling, an aluminum alloy clad material for a heat exchanger having a desired thickness can be obtained. Then, the final annealing is performed, for example, at 360° C. for 3 hours to obtain an O-tempered clad material.
The thickness of the aluminum alloy clad material (clad material) for the heat exchanger may be, for example, brazing material layer:core material:sacrificial material layer=10%:70%:20%, but is not limited to this. Alternatively, the brazing material layer may have a clad ratio of 5% or 15%.

Hot rolling, cold rolling, and final annealing may be performed by a conventional method, but it is also possible to intervene intermediate annealing during the cold rolling process. In that case, the intermediate annealing can be performed, for example, by heating at 200 to 400° C. for 1 to 6 hours. In the final rolling after the intermediate annealing, rolling is performed at a cold rolling rate of 10 to 50%.

The components including the plates 4 and 5 and the inner fins 8 made of the aluminum alloy clad material for the heat exchanger described above are assembled into the state shown in FIG. 1 and the whole is inserted into a high temperature furnace and cooled. As a result, the brazing material 4b is melted, and the contact portions of the respective members are brazed and joined together to form the heat exchanger 1. The brazing conditions in this case are executed in a drop form in a high-purity nitrogen gas atmosphere, and heating is performed at a temperature rising rate such that the arrival time from room temperature to the target temperature is 1 to 20 minutes, and the temperature is 590 to 610°C. This is a process of holding the target temperature for 1 to 8 minutes and then performing air cooling to room temperature.
Note that the above-described member configuration of the heat exchanger, brazing conditions, and the like are merely examples of the embodiment, and are not particularly limited thereto.

In the present embodiment, in the cross section parallel to the rolling direction, the common area Ar2 from the interface between the Al-Si-Zn brazing material 4b and the Al-Mn-based brazing material 4a to the central portion of the plate thickness of the Al-Si-Zn brazing material 4b. The area ratio occupied by the crystal brazing filler metal E3 is 10% or less, that is, in the brazing filler metal 4b, a structure in which the eutectic brazing filler metal E3 and the brazing filler metal primary crystal E2 have a two-layer structure is obtained, and the eutectic brazing filler metal E3 is arranged on the surface layer. Since the brazing material primary crystal E2 is arranged on the interface E1 side between the core material 4a and the brazing material 4b, when the brazing material 4b is exposed to the corrosive environment on the cooling water side, the eutectic brazing material on the surface layer portion is formed. After E3 is preferentially corroded, the brazing filler metal primary crystal E2 thereunder is uniformly corroded, and a mode of general corrosion is obtained, so that the corrosion resistance can be improved.
Further, since the plates 4 and 5 and the inner fin 8 are made of the above aluminum alloy for heat exchanger, the durability of the heat exchanger 1 can be improved.

The present invention is not limited to the configurations of the above-described embodiments, and various modifications can be made in the detailed configuration without departing from the spirit of the present invention.
For example, the aluminum alloy clad material for a heat exchanger of the present invention is not limited to a configuration in which a cooling target (liquid) is cooled by cooling water, and may be a configuration in which a cooling target is cooled by cooling air or the like. Further, the cooling target (liquid) is not limited to oil.

Although the brazing material 4b is clad on one surface of the core material 4a and the sacrificial material is clad on the other surface in the above embodiment, the invention is not limited to this, and the brazing material 4b is provided on both surfaces of the core material 4a. It may be clad.

An aluminum alloy for a core material and an aluminum alloy for a brazing material were cast by semi-continuous casting. As the aluminum alloy for the core material, JIS A3003 alloy was used, and as the aluminum alloy for the brazing material, the alloy shown in Table 1 (the balance Al and unavoidable impurities) was used. The material for the core material was homogenized under the conditions shown in Table 1. The material for the brazing material was homogenized at 450° C. for 10 hours.
Next, a brazing material was combined with one surface of the core material, hot-rolled under predetermined conditions to obtain a clad material, and further cold-rolled. After that, the plate thickness was set to 0.5 mm by cold rolling at a predetermined rolling rate, and final annealing was performed at 400° C. for 3 hours to produce an O-tempered aluminum alloy material (test material). The structure of this test material was as follows: core thickness: brazing material thickness=90%:10%. In this test material, the material thickness of the core material before heat treatment equivalent to brazing was 450 μm and the material thickness of the brazing material was 50 μm.

And about each sample material (cladding material), the arrival time from room temperature to 400°C is 4 minutes to 9 minutes, the arrival time from 400°C to 550°C is 1 minute to 2 minutes, and the arrival time from 550°C to the target temperature. Is heated at a temperature rising rate of 3 to 5 minutes, kept at a target temperature of 600° C. for 3 minutes, then cooled to 300° C. at about 100° C./minute, and then air-cooled to room temperature. Corresponding heat treatment was performed to calculate the size of the eutectic Si particles of the brazing material, the average crystal grain size of the core material, the average crystal grain shape ratio, and the area of the eutectic brazing material, and the corrosion resistance test was performed. It was shown to.

[Size of eutectic Si particles of brazing material]
The equivalent circle diameter of the eutectic Si particles of the brazing material was measured by a scanning electron microscope (FE-SEM). The measurement method was to prepare a sample in which the plate material cross section (cross section parallel to the rolling direction) was exposed by mechanical polishing and cross section polisher (CP) processing to each test material before brazing heat treatment, and 10,000 to 50000 was obtained by FE-SEM. I took a picture at twice. Photographs were taken for 10 fields of view, and the equivalent circle diameter of the eutectic Si particles was measured by image analysis.

[Average crystal grain size and average crystal grain shape ratio of core material]
Using each test material that was heated to 570°C and rapidly cooled to room temperature at a cooling rate of 300°C/min, after filling the cross section parallel to the rolling direction with resin and polishing to a mirror surface, an etching solution (for example, Keller's solution at room temperature) was used. (1 to 3 minutes of immersion) to reveal the crystal grains of the core material, and photographs were taken at 5 times on each of the test materials using an optical microscope at a magnification of 200 times. From the photographed photograph, the crystal grain size was measured by the cutting method in the rolling direction, and the average crystal grain size was calculated. For all the obtained crystal grains, the shape ratio of the crystal grains was calculated from the image data, and the average crystal grain shape ratio was obtained.

[Area rate of eutectic wax]
In the cross section of the residual brazing filler metal after brazing heat treatment of each test material, the area ratio (area occupation) of the eutectic brazing filler metal in the region from the interface between the residual brazing filler metal and the core material to the center in the thickness direction of the residual brazing filler metal. Rate) was calculated. This area ratio was calculated by measuring the eutectic brazing rate per 1 cm ^{2 of} the brazing filler metal by binarizing the sectional structure with an electron beam microanalyzer (EPMA).

[Evaluation of the corrosion resistance of the steady part]
A sample of 30×50 mm was cut out from each sample after heat treatment equivalent to brazing, and in the brazing material layer side, in an aqueous solution containing Cl ⁻ : 195 ppm, SO ₄ ^{2 −} : 60 ppm, Cu ²⁺ : 1 ppm, Fe ³⁺ : 30 ppm. The immersion test was carried out for 4 weeks at a cycle of 80° C.×8 hours and room temperature×16 hours. After the corrosion test sample is dipped in the boiling phosphoric chromic acid mixed solution to remove the corrosion product, the cross-section of the maximum corrosion part is observed to measure the corrosion depth. The corrosion resistance was evaluated. Those having a corrosion depth of 50 μm or less were evaluated as good “A”, those having a corrosion depth of more than 50 μm and not more than 150 μm were evaluated as “B”, and those exceeding 150 μm were evaluated as “C”. evaluated.

[Evaluation of corrosion resistance of joints]
Each test material after the heat treatment equivalent to brazing was cut out into a predetermined plate thickness and then formed into a cup shape. The two sets of molded cups were brazed in such a manner that their brazing material sides were in contact with each other to prepare a corrosion test sample having a joint. Masking the portions other than the joint portion of these samples to expose only the joint portion, and in an aqueous solution containing Cl ⁻ : 195 ppm, SO ₄ ²⁻ : 60 ppm, Cu ²⁺ :1 ppm, Fe ³⁺ :30 ppm, 80° C.×8 The immersion test was carried out for 4 weeks with a cycle between 1 hour and room temperature x 16 hours. The sample after the corrosion test was immersed in a boiling chromic acid phosphoric acid mixed solution to remove the corrosion product, and then the cross-section was observed to measure the corrosion depth of the joint. When the corrosion depth from the surface of the fillet formed on the joint was 1/3 or less of the total length of the fillet, it was evaluated as good "A", and when 1/2 or less was evaluated as "B". Those exceeding 1/2 were evaluated as "C".
The measurement results and evaluations described above are as shown in Table 2.

As is clear from Table 1 and Table 2, the composition of the Al—Si—Zn brazing material (composition of the brazing material alloy) is, in mass %, Si: 2.0% or more and 5.0%, Zn: 0.2. % Or more and 7.0% or less, with the balance being an aluminum alloy having a composition of Al and unavoidable impurities, the average crystal grain size of the core material being 500 μm or more in the major axis direction, and each crystal in the cross section parallel to the rolling direction. The average shape ratio (crystal grain shape ratio), which is the value obtained by dividing the major axis in the rolling direction of the grain by the minor axis in the plate thickness direction, is 4.5 or more, and the eutectic Si particles after the heat treatment equivalent to brazing have an equivalent circle diameter of 2 Example 1 in which the area ratio of the eutectic braze (area ratio of the eutectic braze) in the cross section parallel to the rolling direction (area ratio of the eutectic braze) is 10% or less, and the thickness of the remaining braze is 45 μm or more. Nos. 14 to 14 were "B" or more in both the steady portion and the joint portion in the corrosion resistance test. Among them, in Examples 2, 3 and 6, the average crystal grain of the core material is as large as 700 μm or more and the crystal grain shape ratio is as large as 7.0 or more. Therefore, in the corrosion resistance test, in both the steady portion and the joint portion. Was also "A". In addition, in Example 11, although both the average crystal grain and the crystal grain shape ratio of the core material are small, since the brazing alloy contains Mn, in the corrosion resistance test, "A" "Met.

On the other hand, in Comparative Examples 1 and 2, Si of the brazing alloy is outside the above range, and in Comparative Examples 3 and 4 of Zn of the brazing alloy is outside the above range, " C", and the corrosion resistance was reduced. Particularly in Comparative Example 1, since the amount of Si was as small as 1.9, the joining at the joining portion was insufficient. Further, in Comparative Examples 5 to 8, since the area ratio of the eutectic braze exceeded 10%, the corrosion resistance in the steady part was "C".

1 heat exchanger 2 upper plate 3 lower plate 4 plate (aluminum alloy clad material for heat exchanger)
4a Core material (Al-Mn-based core material)
4b Brazing material (Al-Si-Zn brazing material)
41 liquid channel 42 cooling water channel 5 plate 6 cooling water inflow pipe 7 cooling water outflow pipe 8 inner fin 81 liquid channel 82 cooling water channel

Claims (3)

An aluminum alloy clad material for a heat exchanger, comprising an Al-Mn-based core material and an Al-Si-Zn brazing material bonded to one or both surfaces thereof,
The Al-Si-Zn brazing material contains, by mass %, Si: 2.0% or more and 5.0%, Zn: 0.2% or more and 7.0% or less, and the balance of Al and unavoidable impurities. Made of aluminum alloy of composition,
The average crystal grain size of the Al-Mn-based core material obtained by heating the Al-Si-Zn brazing material to 570[deg.] C. and quenching is 500 [mu]m or more in the major axis direction, and the rolling direction of each crystal grain in the rolling direction parallel cross section. The average shape ratio, which is a value obtained by dividing the major axis by the minor axis in the plate thickness direction, is 4.5 or more,
The eutectic Si particles in the Al—Si—Zn brazing material after the heat treatment equivalent to brazing have a circle equivalent diameter of 2.0 μm or less, and in the cross section parallel to the rolling direction, the Al—Si—Zn brazing material and the Al The area ratio of the eutectic braze in the region from the interface with the —Mn-based core material to the plate thickness center of the Al—Si—Zn brazing material is 10% or less, and the thickness of the remaining brazing material is 45 μm or more. An aluminum alloy clad material for a heat exchanger, which is characterized. The Al-Si-Zn brazing material is, in mass %, Sr: 0.01% or more and 0.10% or less, Bi: 0.01% or more and 0.30% or less, and Mn: 0.1% or more and 1.0. %, Fe: 0.1% or more and 1.0% or less, and further contains one or two kinds. The aluminum alloy clad material for a heat exchanger according to claim 1. A liquid flow path through which the liquid flows, and a cooling water flow path that is disposed adjacent to the liquid flow path and through which cooling water that cools the liquid flows,
The plate for partitioning the liquid flow path and the cooling water flow path is composed of an aluminum alloy clad material for a heat exchanger, which is composed of an Al-Mn-based core material and an Al-Si-Zn brazing material bonded to one surface or both surfaces thereof. Is
The aluminum alloy clad material for a heat exchanger contains the Al-Si-Zn brazing material in mass% and contains Si: 2.0% or more and 5.0% or less and Zn: 0.2% or more and 7.0% or less. The balance is made of an aluminum alloy having a composition of Al and unavoidable impurities, and the Si particles in the Al—Si—Zn brazing material have a circle equivalent diameter of 2.0 μm or less,
In a cross section parallel to the rolling direction, the area ratio occupied by the eutectic braze in the region from the interface between the Al-Si-Zn brazing material and the Al-Mn-based brazing material to the plate thickness center portion of the Al-Si-Zn brazing material is A heat exchanger characterized in that the thickness is 10% or less and the thickness of the remaining wax is 45 μm or more.

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