WO2022004460A1

WO2022004460A1 - Aluminum alloy cladding material

Info

Publication number: WO2022004460A1
Application number: PCT/JP2021/023371
Authority: WO
Inventors: 祥基森; 路英吉野; 正和江戸; 祥平岩尾; 秀幸三宅; 陽介内多; 伸洋本間; 詔悟山田
Original assignee: 三菱アルミニウム株式会社; 株式会社デンソー
Priority date: 2020-06-30
Filing date: 2021-06-21
Publication date: 2022-01-06
Also published as: DE112021003472T5; US20230193431A1; CN115867685A; JP7265506B2; JP2022022649A

Abstract

This aluminum alloy cladding material has a sacrificial material disposed on both surfaces of a core material. The composition of the core material contains, in terms of mass%, 0.7-1.8% of Mn, 0.3-1.3% of Si, 0.05-0.7% of Fe and 0.5-3.0% of Zn, with the remainder comprising Al and unavoidable impurities. The composition of the sacrificial material contains, in terms of mass%, 0.005-0.7% of Mn, 0.05-0.3% of Fe and 1.0-4.0% of Zn, with the remainder comprising Al and unavoidable impurities. The Zn content in the sacrificial material is at least 0.2 mass% higher than the Zn content in the core material. The potential of the core material after a brazing heat treatment is -700 to 870 mV.

Description

Aluminum alloy clad material

The present invention relates to an aluminum alloy clad material having an excellent sacrificial anode effect.
This application claims priority based on Japanese Patent Application No. 2020-13168 filed in Japan on June 30, 2020, the contents of which are incorporated herein by reference.

In recent years, there has been an increasing demand for heat exchangers for automobiles for cooling vehicle air conditioning and engine oil. In these heat exchangers, the outside is exposed to a corrosive environment due to salt damage, dew condensation, etc., and the internal cooling water flow path is also easily corroded, so that high corrosion resistance is required.
Furthermore, since heat exchangers for automobiles need to be joined to other members by brazing heat treatment, aluminum alloy clad materials made of sacrificial materials, core materials, and brazing materials are used for this purpose. There are many. However, heat exchangers used in such applications may take various forms and may have a complex structure, for example, by arranging sacrificial fins to prevent corrosion.

Patent Document 1 and Patent Document 2 have been proposed as those having a sacrificial effect on fins.
In Patent Document 1, the strength is increased by containing Mg in the core material. In Patent Document 2, the sacrificial anode effect is enhanced by containing Sn in the sacrificial material.

Japanese Unexamined Patent Publication No. 5-125477 Japanese Patent No. 2607245

By the way, in order to sacrifice and protect the tube with the fin, it is necessary to set the fin to a lower (lower) potential than the tube. On the other hand, if the potential is made too low (low), the corrosion rate of the fins becomes excessively high, the fins are consumed at an early stage, and the sacrificial anode effect disappears.
Furthermore, when a large amount of flux is applied during brazing, or when brazing is performed by vacuum brazing, the Zn in the material evaporates during brazing, which worsens the corrosion form of the fins and causes the fins to become early. The sacrificial anode effect disappears due to wear.

The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide an aluminum alloy clad material that enables appropriate sacrificial anticorrosion by appropriately setting the potential of the material.

In the first form of the aluminum alloy clad material of the present invention, sacrificial materials are arranged on both sides of the core material, and the composition of the core material is mass%, Mn: 0.7 to 1.8%, Si: It contains 0.3 to 1.3%, Fe: 0.05 to 0.7%, Zn: 0.5 to 3.0%, the balance consists of Al and unavoidable impurities, and the composition of the sacrificial material is mass. %, Mn: 0.005 to 0.7%, Fe: 0.05 to 0.3%, Zn: 1.0 to 4.0%, and the balance consists of Al and unavoidable impurities, which is the sacrifice. The Zn content of the material is 0.2% or more in mass% higher than the Zn content of the core material, and the potential of the core material after the brazing heat treatment is in the range of −700 to −870 mV. ..

The invention of the aluminum alloy clad material of the second aspect is characterized in that, in the invention of the said aspect, the potential difference between the sacrificial material and the core material is 20 to 100 mV.

The aluminum alloy clad material of the third embodiment is characterized in that, in the invention of the above embodiment, the Mn solid solution amount of the core material after the brazing heat treatment is 0.2% or more higher than the Mn solid solution amount of the sacrificial material. And.

According to the aluminum alloy clad material of the present invention, a good sacrificial anode effect can be obtained by appropriately setting the potential of the material to make the potential difference with the brazing partner material appropriate.

It is a figure which shows the cross section of the aluminum alloy clad material of one Embodiment of this invention. It is a perspective view of the heat exchanger manufactured by using the aluminum alloy clad material of one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described.
In the aluminum alloy clad material of the present embodiment, sacrificial materials are arranged on both sides of the core material, and the composition of the core material is Mn: 0.7 to 1.8%, Si: 0.3 to 1. It contains 3%, Fe: 0.05 to 0.7%, Zn: 0.5 to 3.0%, the balance consists of Al and unavoidable impurities, and the composition of the sacrificial material is mass%, Mn: 0. It contains .005 to 0.7%, Fe: 0.05 to 0.3%, Zn: 1.0 to 4.0%, and the balance consists of Al and unavoidable impurities, and the Zn content of the sacrificial material is It is 0.2% or more in mass% higher than the Zn content of the core material, and the potential of the core material after the brazing heat treatment is in the range of −700 to −870 mV.
Further, it is preferable that the potential difference between the sacrificial material and the core material is 20 to 100 mV.
Further, it is preferable that the Mn solid solution amount of the core material after the brazing heat treatment is 0.2% or more higher than the Mn solid solution amount of the sacrificial material.

The reasons for limiting the technical matters specified in this embodiment will be explained below. The contents of the components contained in the sacrificial material and the core material are shown in% by mass.

[Core material]
Mn: 0.7 to 1.8%
Mn is an element that improves strength. However, if the content is small, the desired effect cannot be sufficiently obtained, and if the content is excessive, the manufacturability (castability, rollability) is deteriorated. For these reasons, the Mn content is within the above range. For the same reason, it is desirable that the lower limit of the Mn content is 0.7% and the upper limit is 1.6%.

Si: 0.3-1.3%
Si is an element that improves strength. However, if the Si content is low, the desired effect cannot be obtained, and if it is excessively contained, the melting point is lowered, so that the fins buckle during the brazing heat treatment and the brazing property is lowered. For these reasons, when Si is contained, the Si content is within the above range. For the same reason, it is desirable that the lower limit is 0.3% and the upper limit is 1.1%.

Fe: 0.05-0.7%
Fe is an element that improves the strength. However, if the content is excessive, a giant intermetallic compound is generated during casting, which deteriorates manufacturability and corrosion resistance. Further, since the lower limit is present as an impurity in the raw material at the time of casting, if it is less than the lower limit, the manufacturing cost increases. For these reasons, the Fe content is within the above range. For the same reason, it is desirable to set the lower limit to 0.05% and the upper limit to 0.4%.

Zn: 0.5-3.0%
Zn is included to increase the sacrificial anode effect. However, if the Zn content is low, the desired effect cannot be obtained, and if the Zn content is excessive, the sacrificial anode effect is lost at an early stage due to the acceleration of the corrosion rate. For the same reason, it is desirable that the lower limit is 1.0% and the upper limit is 2.5%.

[Sacrificial material]
Sacrificial materials are placed on both sides of the core material. The sacrificial material on each surface may have the same composition, or may have different compositions within the range of the following composition.

Mn: 0.005 to 0.7%
Mn is contained to improve the strength. However, if the content is excessive, the manufacturability (castability, rollability) is deteriorated. Further, when the Mn content of the sacrificial material becomes larger than the content of the core material, the difference between the sacrificial material and the Mn solidly dissolved in the core material cannot be taken after the brazing heat treatment, and the core material remains. Corrosion occurs, and the form of corrosion worsens. Further, since the lower limit is present as an impurity in the raw material at the time of casting, if it is less than the lower limit, the manufacturing cost increases. For these reasons, the Mn content is within the above range. For the same reason, it is desirable that the lower limit of the Mn content is 0.005% and the upper limit is 0.5%.

Fe: 0.05-0.3%
Fe is contained to improve the strength. However, if the content is excessive, a giant intermetallic compound is generated during casting, which deteriorates manufacturability and corrosion resistance. Further, since the lower limit is present as an impurity in the raw material at the time of casting, if it is less than the lower limit, the manufacturing cost increases. For these reasons, the Fe content is defined in the above range. For the same reason, it is desirable that the upper limit of the Fe content is 0.2%.

Zn: 1.0 to 4.0%
Zn increases the sacrificial anode effect. However, if the content is too small, the desired effect cannot be obtained, pitting corrosion occurs and the core material is corroded with the sacrificial material remaining, and the corrosion form is deteriorated. On the other hand, if the content is excessive, the sacrificial anode effect is lost at an early stage due to the accelerated corrosion rate. In addition, preferential corrosion of fillets occurs. For these reasons, the Zn content is defined in the above range.
For the same reason, it is desirable that the lower limit of the Zn content is 1.5% and the upper limit is 3.5%.

Si, Cu, Mg, Cr, Ti and the like may be contained in the range of 0.05% or less as unavoidable impurities of the sacrificial material. Further, Si may be contained up to 0.1%.

[Relationship between core material and sacrificial material]
The Zn content of the sacrificial material is 0.2% or more in mass% higher than the Zn content of the core material.
By increasing the Zn content of the sacrificial material by 0.2% or more higher than the Zn content of the core material, the sacrificial material is preferentially corroded and the corrosion form of the fins is improved. When the Zn content of the sacrificial material is lower than the Zn content of the core material, corrosion progresses to the core material while the sacrificial material remains, and the corrosion form deteriorates.
The Zn content of the sacrificial material is more preferably 0.5% to 2.5% higher than the Zn content of the core material, and more preferably 1.0% to 1.5% higher.

It is preferable that the Mn solid solution amount of the core material after the brazing heat treatment is 0.2% or more in mass% higher than the Mn solid solution amount of the sacrificial material.
During the brazing heat treatment, the elements in the material diffuse, so the Zn added to the sacrificial material diffuses into the core material. In that case, the potential difference between the sacrificial material and the core material becomes small, and corrosion tends to proceed in the plate thickness direction. On the other hand, since Mn hardly diffuses during brazing heat treatment, even when the potential difference between the sacrificial material and the core material is small, the Mn solid solution amount of the core material is made higher than that of the sacrificial material, so that the interface between the sacrificial material and the core material is formed. The potential difference in the vicinity becomes large, the sacrificial material corrodes preferentially, and the corrosion form of the fins improves. For the above reasons, the amount of Mn solid solution is set in the above range.
It is more preferable that the Mn solid solution amount of the core material after the brazing heat treatment is 0.3% or more higher than the Mn solid solution amount of the sacrificial material.
As an example of the brazing heat treatment, there is a condition that the temperature is raised from room temperature (5 ° C to 40 ° C) to 600 ° C in 20 minutes and held at 600 ° C for 3 minutes. The same applies to the following. However, the brazing conditions are not limited to the above in the present embodiment.

[potential]
The potential of the core material after brazing heat treatment is in the range of −720 mV to −870 mV.
The sacrificial anode effect can be obtained by having a predetermined potential. If the potential is too high, the desired effect cannot be obtained, and if the potential is too low, the sacrificial anode effect is lost early due to the accelerated corrosion rate.
The potential of the core material after the brazing heat treatment is preferably in the range of −730 mV to −870 mV, and more preferably in the range of −770 mV to −840 mV.

The potential difference between the sacrificial material and the core material (core material potential-sacrificial material potential) is preferably 20 mV to 100 mV.
Having the above potential difference improves the corrosion morphology of the fins. If the potential difference is too small, the core material also corrodes while the sacrificial material remains, and the corrosion form deteriorates. If the potential difference is excessive, the sacrificial anode effect is lost at an early stage due to the accelerated corrosion rate.
The potential difference between the sacrificial material and the core material is more preferably in the range of 40 mV to 100 mV.

The following is an example of the method for manufacturing the aluminum alloy clad material of the present embodiment.
An aluminum alloy for a core material and an aluminum alloy for a sacrificial material having the composition of the present embodiment are prepared. These alloys can be produced by a conventional method, and the production method is not particularly limited. For example, it can be manufactured by semi-continuous casting.

For the aluminum alloy for the core material, Mn: 0.7 to 1.8%, Si: 0.3 to 1.3%, Fe: 0.05 to 0.7%, Zn: 0.5 to% by mass%. An alloy containing 3.0% and having a composition in which the balance consists of Al and unavoidable impurities is used.
The aluminum alloy for sacrificial materials contains Mn: 0.005 to 0.7%, Fe: 0.05 to 0.3%, Zn: 1.0 to 4.0% in mass%, and the balance is An alloy having a composition consisting of Al and unavoidable impurities is used.
In selecting the composition, it is desirable to set the Zn content of the sacrificial material to be 0.2% or more in mass% higher than the Zn content of the core material.

The aluminum alloy for the core material or the aluminum alloy for the sacrificial material can be subjected to a homogenization treatment, if desired, after being melted. In the homogenization treatment, Mn that is supersaturated and solid-solved in the matrix during casting is precipitated as an intermetallic compound. Since the size and the amount of dispersion of the precipitated intermetallic compound are affected by the temperature and time of the homogenization treatment, it is necessary to select appropriate heat treatment conditions.
Generally, high-temperature heat treatment promotes the precipitation and growth of intermetallic compounds and lowers the Mn solid solubility. Conversely, high-temperature heat treatment suppresses the precipitation and growth of intermetallic compounds and Mn solid solubility. Will be higher. Further, when the intermetallic compound precipitated by the homogenization treatment is made finer, the precipitate is melted again by the brazing heat treatment and solid-solved in the material, so that the amount of Mn solid solution after the brazing heat treatment increases. On the other hand, when the intermetallic compound precipitated by the homogenization treatment is coarsened, a part of the compound is melted during the brazing heat treatment, but it is not completely melted, so that the amount of Mn solid dissolved after the brazing heat treatment is reduced.
In the present embodiment, the corrosion morphology of the fins is improved by increasing the Mn solid solution amount of the core material by 0.2% or more in mass% from the Mn solid solution amount of the sacrificial material, so that the homogenization treatment and hotness are performed. It is necessary to control the amount of Mn solid solution by appropriately combining rolling and annealing temperature conditions.

In the present embodiment, in order to improve the corrosion form of the fin material by the difference in the amount of Mn solid solution between the core material and the sacrificial material, the core material is homogenized at 400 ° C. to 500 ° C. for 4 to 16 hours. , Precipitate finely. On the other hand, the sacrificial material is basically not homogenized, but is homogenized at 500 ° C. to 600 ° C., which is higher than the core material, for 4 to 16 hours, and the sacrificial material is deposited on the core material. By making the material coarse, the amount of Mn that dissolves in the sacrificial material is reduced and the corrosion form is improved.

The aluminum alloy for the core material and the aluminum alloy for the sacrificial material are made into a plate material through hot rolling. Further, it may be made into a plate material through continuous casting and rolling.
In hot rolling, the finishing temperature can be set.
Normally, hot rolling is loaded at a high temperature of around 500 ° C., but after the rolling is completed, it is coiled and cooled to room temperature. In this case, the time held at a high temperature changes depending on the finishing temperature of hot rolling, which affects the precipitation behavior of the intermetallic compound.

The plate material is hot-rolled and then cold-rolled to obtain an aluminum alloy clad material having a desired thickness.
In the present embodiment, the clad ratio of the clad material is not particularly limited, but for example, a thickness of one side of the sacrificial material of 5 to 25%, a thickness of the core material of 50 to 90%, or the like is used.
In the above description, the sacrificial material is directly superimposed on the core material, but another layer may intervene.

The clad material is, for example, 0.05 to 0.20 mm thick by cold rolling. In the middle of cold rolling, intermediate annealing may be performed. The conditions for intermediate annealing can be selected from, for example, 150 to 400 ° C. and 1 to 10 hours. However, when the intermediate annealing temperature becomes high, the precipitation and growth of intermetallic compounds are promoted during annealing, and the difference in the amount of Mn solid solution between the sacrificial material and the core material becomes small. Things are desirable.

As shown in FIG. 1, these plate materials have a sacrificial material 3a on one side of the core material 2 and a sacrificial material 3b on the other side, and are clad with an appropriate clad ratio in a superposed state to form an aluminum alloy clad material 1. It is said that. The

sacrificial materials

3a and 3b may have the same composition, or may have different compositions within the range of the above-mentioned composition.

The obtained clad material can be used, for example, as a tube material for a heat exchanger, fins, or the like. The

sacrificial materials

3a and 3b and the core material 2 have a potential difference of 20 to 100 mV.
The fin material for the heat exchanger is brazed and joined to an appropriate brazed member such as a tube.
The material and shape of the brazed member are not particularly limited as in this embodiment, and an appropriate aluminum material can be used.

The heat treatment conditions at the time of brazing are not particularly limited except that the temperature is raised to 590 to 615 ° C., for example, heating is performed at a heating rate such that the arrival time from 550 ° C. to the target temperature is 1 minute to 10 minutes. The heat treatment can be carried out under the condition that the temperature is maintained at a target temperature of 590 to 615 ° C. for 1 minute to 20 minutes, then cooled to 300 ° C. at 50 to 100 ° C./min, and then air-cooled to room temperature.
After the brazing heat treatment, it is desirable that the Mn solid solution amount of the core material is 0.2% or more in mass% higher than the Mn solid solution amount of the sacrificial material.

Further, after brazing, the potential of the core material is in the range of −720 to −870 mV.
Since the potential of the core material of the brazing mating member, which is the corrosion-protected member, takes into consideration the commonly used Al—Mn-based alloy, only the potential of the core material is specified.
The potential is adjusted according to the composition of the material and the production conditions.

FIG. 2 shows an aluminum automobile heat exchanger 4 in which fins 5 are formed using the aluminum alloy clad material and an aluminum alloy tube 6 is used as a brazing target material. The fins 5 and the tube 6 are incorporated with the reinforcing material 7 and the header plate 8 to obtain an aluminum heat exchanger 4 for automobiles by brazing.

Based on the compositions shown in Tables 1 and 2 (the balance is Al and unavoidable impurities), aluminum alloys for sacrificial materials and core materials were cast by semi-continuous casting. As the aluminum alloy for the sacrificial material and the core material, alloys having the compositions shown in Tables 1 and 2 (remaining Al and unavoidable impurities) were used. The sacrificial material contains Si as an unavoidable impurity having the compositions shown in Tables 1 and 2. Next, homogenization treatment is performed under the conditions shown in Tables 3 and 4, hot rolling and cold rolling are performed, then intermediate annealing is performed, and cold rolling is performed to roll to a plate thickness of 0.2 mm. As a result, a plate material (clad material) of quality H14 was produced. The clad material was prepared so that the clad ratio on one side of the sacrificial material was 10%.

The following evaluation methods were carried out for the test materials using the clad materials of Examples 1 to 33 and Comparative Examples 1 to 16 obtained. The evaluation results are shown in Tables 3 and 4.

[Corrosion evaluation of the test material alone]
A test material having a plate thickness of 0.20 mm after the final rolling was subjected to brazing heat treatment to prepare a material to be subjected to a corrosion test.

[Evaluation of sacrificial protection]
A corrugated test material with a plate thickness of 0.20 mm is used as a brazing sheet with a plate thickness of 0.3 mm (clad composition: brazing material (10%) / core material (75%) / sacrificial material (15%), brazing material. : JIS A4045 alloy, core material: Al-1.0Mn-0.5Cu alloy, sacrificial material: JIS A7072 alloy) was assembled on the brazing material surface and subjected to brazing heat treatment.

As brazing conditions, the samples of _K 1-3 _{AlF 4-6} 10g / ^{m 2} was coated as a flux, the temperature was raised in 20 minutes up to 600 ° C. from room temperature (20 ° C.) with a high purity nitrogen gas atmosphere, 600 ° C. After holding for 3 minutes at 60 ° C./min, a heat treatment equivalent to brazing was performed to cool to 300 ° C. at 60 ° C./min.

Thereafter, masking the sacrificial anode material surface of the test material, with the brazing material surfaces of the test piece and the brazing sheet is exposed, OY water ^{_{^{(Cl -: 195ppm, SO 4}}} 2-: 60ppm, Cu 2+: 1ppm, Fe ^{A dipping test with 3+} : 30 ppm residual pure water) was carried out. The test conditions were room temperature (20 ° C.) × 16 h + 88 ° C. × 8 h (without stirring) as a daily cycle, and the fins were immersed for 2 weeks in the corrosion evaluation and for 8 weeks in the sacrificial corrosion protection evaluation. Then, the corrosion product was removed with chromic phosphate, and the corrosion form of the test material and the depth of the corroded part of the brazing sheet were evaluated.

[Corrosion evaluation criteria for simple substances]
D: Priority corrosion of the core material occurs (core material: only the central part of the plate thickness is preferentially corroded)
C; Partial pitting corrosion is seen (partially, the sacrificial material remains undissolved and the core material corrodes).
B; Mostly planar corrosion, but only a small part of pitting corrosion is seen.
A; Surface corrosion on the entire surface

[Evaluation criteria for sacrificial protection]
D; A through hole is generated in the brazing sheet.
C; Corrosion depth generated in the brazing sheet is more than half the plate thickness (0.125 mm) and less than penetration B; Corrosion depth generated in the brazing sheet is less than half the plate thickness (0.125 mm) A; The resulting corrosion depth is less than 1/4 (0.06 mm) of the plate thickness

[Measurement of natural potential]
The natural potentials of the fin core and sacrificial material were measured using a silver-silver chloride electrode in a 5% NaCl solution whose pH was adjusted to 3.0 with acetic acid.

[Evaluation of strength after brazing heat treatment]
The material after the heat treatment equivalent to brazing was milled into the shape of a JIS No. 5 test piece, and the strength was measured by a tensile test.

[Evaluation criteria for strength after brazing heat treatment]
D; Tensile strength after brazing heat treatment is less than 90 MPa C; Tensile strength after brazing heat treatment is 90 MPa or more and less than 120 MPa B; Tensile strength after brazing heat treatment is 120 MPa or more

[Measurement of Mn solid solubility]
The fin material after the brazing heat treatment was etched with a 10% NaOH solution to prepare a sample of only the core material and the sacrificial material. Then, the core material and the sacrificial material were each dissolved by the hot phenol method, and the obtained solution was subjected to ICP emission spectroscopic analysis to measure the solid solution amount of Mn.

In this embodiment, a combination of a fin corresponding to the clad material of the present invention and a tube as a mating material is assumed, and the tube is sacrificed by making it possible to set the potential of the fin in an appropriate range with respect to the potential of the tube. It was clarified that it protects against corrosion and suppresses the early consumption of fins. In addition, by applying sacrificial material to both sides of the fin and setting the potentials of the fin core material and the sacrificial material within an appropriate range, the sacrificial material is preferentially corroded to suppress corrosion in the plate thickness direction. It has the effect of improving the form of corrosion.
Although the present specification describes the problem and effect by using the outer fin as a representative, the present invention is not limited to the outer fin, and the same applies to fins other than the outer fin and other uses. The effect of can be obtained.

Although the present invention has been described above based on the above embodiments and examples, the present invention is not limited to the contents of these explanations, and is appropriate for the above embodiments as long as it does not deviate from the scope of the present invention. It can be changed.

1 Clad material 2 Core material 3a Sacrificial material 3b Sacrificial material 4 Heat exchanger 5 Fins 6 Tube

Claims

Sacrificial materials are arranged on both sides of the core material, and the composition of the core material is Mn: 0.7 to 1.8%, Si: 0.3 to 1.3%, Fe: 0.05 to 0. It contains 0.7%, Zn: 0.5 to 3.0%, the balance is Al and unavoidable impurities, and the composition of the sacrificial material is mass%, Mn: 0.005 to 0.7%, Fe: It contains 0.05 to 0.3%, Zn: 1.0 to 4.0%, the balance consists of Al and unavoidable impurities, and the Zn content of the sacrificial material is larger than the Zn content of the core material. % Is higher by 0.2% or more, and the potential of the core material after the brazing heat treatment is in the range of −700 to −870 mV.
The aluminum alloy clad material according to claim 1, wherein the potential difference between the sacrificial material and the core material (core material potential-sacrificial material potential) is 20 to 100 mV after the brazing heat treatment.
The aluminum alloy clad according to claim 1 or 2, wherein the amount of Mn solid solution after the brazing heat treatment of the core material is 0.2% or more in mass% higher than the amount of Mn solid solution of the sacrificial material. Material.