JP2009030123A - Aluminum alloy-clad material for heat exchanger, excellent in strength and pitting resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suitable material to a structural member in an aluminum-made heat exchange for automobile having excellent brazing nature and also, excellent pitting resistance in the wide pH range from acidic to alkali atmospheres. <P>SOLUTION: This aluminum alloy clad material is clad as an aluminum alloy brazing material on the one side face of the aluminum alloy core material and clad as a sacrificial anode material on the other side face thereof, and the sacrificial anode material is composed of 0.5-10.0% Zn, 0.8-1.5% Si, 0.005-0.2% Mg, if necessary, one or more kinds among 0.1-1.5% Ni, 0.05-0.3% Ti, 0.05-0.3% Zr, and satisfying the relation of and ratio of Fe and Si in the inevitable impurities to Fe&le;1/4&times;Si. Preferably, Si particles having a circle equivalent diameter of 0.1-1.0 &mu;m in the sacrificial anode material matrix, are distributed from 3&times;10<SP>2</SP>to 3&times;10<SP>5</SP>pieces/mm<SP>2</SP>. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention can be applied as a structural member for aluminum heat exchangers such as radiators for automobiles and heater cores manufactured by inert gas atmosphere brazing and vacuum brazing using flux, and has particularly excellent brazing properties and hole resistance. The present invention relates to an aluminum alloy clad material for a heat exchanger that is excellent in strength and pitting corrosion resistance that can be optimally used as a thin-walled tube material that requires corrosion resistance.

A radiator, which is a type of heat exchanger for automobiles, is generally manufactured by integrating members such as fins, tubes, headers, and side supports by brazing using a fluoride-based flux.
As a tube material, an Al—Si brazing material is clad on one surface of a core material made of an Al—Mn—Cu alloy, and Al—Zn or Al—Mg—Zn alloy is clad as a sacrificial anode material on the other surface. A three-layer aluminum alloy is used. The most commonly used clad alloy is JIS3003 alloy (Mn: 1.0 to 1.5%, Cu: 0.1 to 0.2%, Si: 0.6% or less in mass%). Fe: 0.75% or less, Zn: 0.10% or less, balance: Al—Mn alloy composed of Al and inevitable impurities) as a core material, and a sacrificial anode material composed of JIS7072 alloy on one side of the core material. A clad material (brazing sheet) is known in which an Al—Si or Al—Si—Zn brazing material is bonded to the other surface. The Al-Si brazing material is used for joining the tube material and the fin material, and joining the tube material and the header plate at the time of brazing, and the sacrificial anode material is in contact with the working fluid during use as a heat exchanger and is a core material. The sacrificial anode effect in which the skin material mainly corrodes due to the difference in electrochemical properties with the above has an effect of suppressing pitting corrosion and crevice corrosion of the core material and improving pitting corrosion resistance.

  2. Description of the Related Art In recent years, automotive heat exchangers are required to have thinner components in order to achieve cost reduction and high performance by reducing weight and size. If the tube material is thinned, it becomes difficult to make a tube by high-frequency welding, so that it is considered that a tube that is formed by brazing will become the mainstream in the future (see Patent Documents 1 and 2). An example of the pipe making will be described with reference to FIG. 2. The clad material 10 in which the brazing material 12 and the sacrificial anode material 13 are clad on one side of the core material 11 is bent so that the sacrificial anode material 13 is inside, and both ends are Each is folded inward to abut each other to provide an inner column portion 15, and the tip of the column portion 15 is abutted against the sacrificial anode material 13 and brazed to form a tube.

  However, in this case, due to the difference in tube tube shape and thinning of the material, even if the above brazing sheet is used, joint failure frequently occurs in the vicinity A of the column in the tube, and the expected durability and pressure strength can be obtained. There is no problem. Therefore, a clad material that can obtain good bonding even in the vicinity of the column in the tube is required.

  Moreover, since the surface of an aluminum alloy is usually covered with a natural oxide film and is excellent in corrosion resistance in a neutral aqueous solution environment, it is used as a refrigerant flow path material for a heat exchanger for automobiles. However, when this oxide film is locally broken for some reason, the other part is strong, so that corrosion concentrates on the defective part of the film, resulting in pitting corrosion, and a through hole is formed at an early stage. As a countermeasure, an automobile heat exchanger such as a radiator uses a clad material in which an aluminum alloy that is electrically lower than the core material is bonded to one side of the core material as a sacrificial anode material as described above.

  These aluminum alloy clad materials have excellent sacrificial anode effect when used as a refrigerant flow path material for aluminum heat exchangers such as radiators and heater cores, when the refrigerant is neutral to weakly acidic and contains Cl ions. However, when the refrigerant is an alkaline solution having a pH of 9 or more, the effect of the sacrificial anode material does not work and a through hole is generated in a short period of time, so that the anticorrosion effect is not sufficiently exhibited.

  Therefore, as an aluminum alloy clad material with improved pitting corrosion resistance in an alkaline environment, for example, Si: 0.6% or less, Fe: 0.7% or less, Cu: 0.05-0.20%, Mn: Al-Si alloy brazing material is clad on one side of an aluminum alloy core material containing elements of 1.0 to 1.5%, Zn: 0.10% or less, and the balance being inevitable impurity elements and Al, A three-layer aluminum alloy clad material is proposed in which an aluminum alloy sacrificial anode material containing Fe: 0.7 to 1.2% and Zn: 0.1 to 1.5% is clad on one surface (see Patent Document 3). ).

Also, in an aluminum alloy clad material in which an aluminum alloy brazing material is clad on one surface of a core material made of an aluminum alloy and a sacrificial anode material is clad on the other surface, the sacrificial anode material is bonded to Al and is compared with the matrix of the sacrificial anode material. 5 × 10 ² per 1 mm ^{2 of the} compound containing 1 to 10 μm of a particle diameter (equivalent circle diameter, the same shall apply hereinafter), which is composed of an aluminum alloy containing an element that forms a noble compound and the balance being Al and impurities. aluminum alloy clad material having excellent corrosion resistance, characterized in that there are ^four to 5 × 10 has also been proposed (see Patent Document 4).
JP-A-9-122804 JP 2002-303496 A Japanese Patent Laid-Open No. 10-17967 Japanese Patent Laid-Open No. 11-80871

  However, since the above materials contain many compounds having a higher potential than the matrix in the sacrificial anode material, the corrosion rate of the sacrificial anode material increases due to the formation of local cells, and clogging of the radiator tube due to corrosion products is a problem. Become. Conventionally, only the improvement of the pitting corrosion resistance of the clad material is considered, and it cannot be said that the improvement of brazing is sufficient. Particularly in the case of a thin-walled material, it is necessary to further improve the brazing property in a tube that is formed by brazing.

  The present invention has been made against the background of the above circumstances, and provides a material having excellent brazing resistance even in a thin-walled material and having excellent pitting corrosion resistance in a wide pH range from acidic to alkaline environments. Objective.

  As a result of researches to obtain a clad material having excellent brazing resistance and excellent pitting corrosion resistance in a wide pH range from alkaline to excellent brazing and acidity, the inventors have obtained the following knowledge.

<Brassability>
As for brazing, if the Si particles are finely distributed in the sacrificial anode material, these form oxide film defects on the surface of the sacrificial anode material, so even if the oxide film is not sufficiently removed by the flux, the tube itself The wettability with the brazing filler metal is improved, and a good bonding state is obtained. In addition, the matrix in the vicinity of the Si particles has a low melting point due to Si diffusion during the brazing heat treatment, and it has been found that the bondability with the brazing material is improved. This effect is due to the single precipitation of Si. Since Si easily forms intermetallic compounds with Fe, Mn, etc., the addition amount of these elements is controlled, and the balance of the addition amount at which the single precipitation of Si occurs sufficiently. It is necessary to consider.

<Corrosion resistance>
Conventionally, the generation of deep pitting corrosion has been suppressed by adding Zn to the sacrificial anode material and lowering the potential relative to the core material. However, in the case of thin-walled materials, the potential difference with the core material becomes small due to element diffusion during brazing, and the corrosion form of the sacrificial anode material does not become planar, and partial pitting corrosion may occur. . Therefore, the present invention material suppresses the occurrence of deep pitting corrosion by adding Si to the sacrificial anode material to finely disperse Si particles and increasing the corrosion starting point of the sacrificial anode material.

Pitting corrosion in an alkaline environment preferentially corrodes film defects on the material surface, resulting in deep pitting corrosion. Therefore, in order to improve the pitting corrosion resistance in an alkaline environment, it is necessary to prevent the coating defects from being concentrated locally and to disperse the starting point of corrosion over the entire material surface. Therefore, in the present invention material, an appropriate amount of Si was added to the sacrificial anode material, and the pitting corrosion resistance was improved by fine precipitation of Si particles in the sacrificial anode material matrix after brazing. The Si precipitate forms a defective portion of the film, and the same site serves as a starting point of corrosion, so that local corrosion is suppressed and the corrosion form is planarized.
Even when Fe or Ni is added to the sacrificial anode material, Al—Fe and Al—Ni based intermetallic compounds are produced, and an effect of improving pitting corrosion resistance is seen in an alkaline environment, but the size is determined by precipitation of Si alone. It is very coarse compared to the case. It is important to optimize the balance of Si and Fe addition amounts so that the coarse intermetallic compound is not formed because the starting point of corrosion increases and the corrosion form becomes planar when the size of the dispersed particles is as small as possible. is there.

  Further, since the Si precipitate is a semiconductor and hardly forms a matrix and local cells, the action of increasing the corrosion rate is very small compared to an intermetallic compound with Al, and clogging of the tube is suppressed. Furthermore, since the Si-dispersed particles do not dissolve in an alkaline solution, when corrosion progresses, they are incorporated into the film formed on the surface of the material and have an effect of making the film dense and uniform, and the adhesion of the film is improved. It has the effect of preventing the intrusion of the corrosive liquid into the surface and remarkably suppressing the progress of corrosion.

  As described above, the present inventors have found the superiority of fine dispersion of Si particles in the sacrificial anode material from the viewpoint of improving brazeability and pitting corrosion resistance, and the balance between the additive components and the addition amount of the sacrificial anode material. By defining the particle size and distribution state, brazing and pitting corrosion resistance are remarkably improved.

  That is, among the aluminum alloy clad materials excellent in strength and pitting corrosion resistance of the present invention, the first present invention is such that an aluminum alloy brazing material is clad on one surface of the aluminum alloy core material and the other surface of the core material is sacrificed. In the aluminum alloy clad in which the anode material is clad, the sacrificial anode material is in mass%: Zn: 0.5 to 10.0%, Si: 0.8 to 1.5%, Mg: 0.005 to 0 .2%, the balance is made of Al and inevitable impurities, and the proportion of Fe and Si in the inevitable impurities satisfies the relationship of Fe amount (wt%) ≦ ¼ × Si amount (wt%). It is characterized by doing.

The aluminum alloy clad material having excellent strength and pitting corrosion resistance according to the second aspect of the present invention is the same as the first aspect of the present invention, wherein the sacrificial anode material is a Si particle having an equivalent circle diameter of 0.1 to 1.0 μm in the matrix. Are distributed 3 × 10 ^{2 to} 3 × 10 ⁵ per mm ² .

  The aluminum alloy clad material excellent in strength and pitting corrosion resistance of the third aspect of the present invention is the sacrificial anode material in the first or second aspect of the present invention. % Is included.

  The aluminum alloy clad material having excellent strength and pitting corrosion resistance according to the fourth aspect of the present invention is the sacrificial anode material according to any one of the first to third aspects, wherein the sacrificial anode material is further in mass%, and Ti: 0.05 to One or more of 0.3% and Zr: 0.05 to 0.3% are included.

  In the present invention, as described above, the content and ratio of each element of the sacrificial anode material, the size and distribution of the Si particles are controlled, and the Si particles are precipitated alone in the sacrificial anode material, thereby achieving excellent brazing and resistance. Ensures pitting corrosion. The significance of the alloy component in the sacrificial anode material and the reason for limiting the component range are described below. In addition, all the following contents are shown by the mass%.

Zn: 0.5 to 10.0%
Zn lowers the potential of the sacrificial anode material and makes the sacrificial anode effect on the core material effective, thus preventing the corrosion of the core material. It also has the effect of making the oxide film on the surface of the sacrificial anode material brittle and increasing the starting point of corrosion to make the corrosion form planar. If the content is less than 0.5%, the desired effect cannot be obtained in the acidic region. On the other hand, if the content exceeds 10.0%, the self-corrosion resistance is excessively increased, which is not preferable. Therefore, the Zn content is set to 0.5 to 10.0%. The more preferable lower limit of the Zn content is 1.0%, and the upper limit is 5.0%.

Si: 0.8 to 1.5%
Si is dispersed as Si particles in the sacrificial anode material, and the site where the Si particles are present suppresses the formation of an oxide film, resulting in a film defect, thereby improving the wettability, that is, the bondability with the brazing material during brazing. . Moreover, since it is finely dispersed in the substrate after brazing and the starting point of corrosion increases, the pitting corrosion resistance is improved. Furthermore, it has the effect of improving the strength by solid solution in fine precipitation or matrix, and contributes to the strength improvement of the sacrificial anode material. When Si is less than 0.8%, the desired effect cannot be obtained because the number of precipitated dispersed particles is small. On the other hand, when it exceeds 1.5%, the melting point is lowered and the sacrificial anode material is locally melted during brazing. In addition, the size and number of Si precipitates increase, and the corrosion resistance decreases. Therefore, the Si content is set to 0.8 to 1.5%. The more preferable lower limit of the Si content is 0.9%, and the upper limit is 1.2%.

Mg: 0.005-0.2%
Mg dissolves during brazing and improves material strength. In addition, Zn, Si, MgZn ₂ , and Mg ₂ Si in the sacrificial anode material are formed after brazing and contribute to further strength improvement by age hardening. If the content of Mg is less than 0.005%, the desired effect cannot be obtained, and if it exceeds 0.2%, the brazing property decreases. Therefore, the Mg addition amount is set in the range of 0.005 to 0.2%. The more preferable lower limit of the Mg content is 0.03%, and the upper limit is 0.15%.

Fe amount ≦ 1/4 × Si amount Fe generates Si and Al—Fe—Si based compounds, and in an alkaline environment, pits are generated starting from these metal opening compounds, thereby increasing the starting point of pitting corrosion. There is. However, since a coarser compound is formed as compared with Si-dispersed particles, large pitting corrosion is likely to occur, and since a matrix and local cells are easily formed, the corrosion rate is also increased. In the present invention, the precipitation of Si is inhibited, and the pitting corrosion resistance is lowered. Therefore, the Fe amount is regulated by the balance with the Si content.

  That is, as described above, it is important to precipitate Si single particles in the sacrificial anode material in the present invention, but since Si easily generates an intermetallic compound with Fe, it is necessary to limit the amount of Fe added to the amount of Si added. In the present invention, Fe amount (wt%) ≦ 1/4 × Si amount (wt%) is defined. When the amount of Fe in the sacrificial anode material is more than 1/4 of the amount of added Si, an Al—Fe—Si based compound is generated and the amount of precipitated Si alone is reduced, so that a sufficient effect cannot be obtained.

Ni: 0.1 to 1.5%
Ni forms an Al—Ni-based compound in the substrate. Therefore, pits are generated on the material surface starting from the Ni-Ni compound, and the starting point of pitting corrosion is increased to suppress deep pitting corrosion. In particular, in an alkaline environment, the concentration of cathode spots is suppressed, contributing to improvement in corrosion resistance. It also contributes to the improvement of strength. Al—Ni-based compounds are coarser than Si particles, but compared to Al—Fe-based compounds and Al—Fe—Si-based compounds, their size is small and evenly distributed, so that they have a great effect on improving corrosion resistance. In addition, there is an effect of finely distributing Si precipitates. If the Ni content is less than 0.1%, the desired effect cannot be obtained. On the other hand, if it exceeds 1.5%, the self-corrosion property of the sacrificial anode skin material is increased, which is not preferable. Therefore, when Ni is contained as desired, the content is set in the range of 0.1% to 1.5%. The more preferable lower limit of the Ni content is 0.3%, and the upper limit is 0.7%.

Ti: 0.05-0.3%
Zr: 0.05-0.3%
When Ti is added, a portion having a high Ti concentration (solid solubility) and a portion having a low Ti content are produced during casting, and this is extended during rolling to form a layered Ti concentration distribution in the material. The portion where the Ti concentration is low has a lower potential than the portion where the Ti concentration is high, and corrosion progresses preferentially, so that the corrosion form becomes layered and the corrosion resistance is improved. In addition, when Zr is added, Al—Zr-based intermetallic compounds are finely precipitated, which serve as starting points for corrosion in an alkaline environment, increase the number of pitting corrosion, and suppress deep pitting corrosion. Zr has the effect of promoting the layered corrosion of Ti, and when Ti and Zr are added simultaneously, it has the effect of further improving the pitting corrosion resistance.

  These components are dispersed in the substrate as a fine intermetallic compound after brazing and have an effect of improving the strength, so that they are added as necessary, but Ti: less than 0.05%, Zr: 0.05% If it is less than the range, the desired effect cannot be obtained. On the other hand, if it exceeds Ti: 0.3% and Zr: 0.3%, the workability is lowered, which is not preferable. Therefore, Ti: 0.05 to 0.3% and Zr: 0.05 to 0.3% were set.

<Defining the size and number of Si particles>
0.1~1.0μm of Si ^{particles: 3 × 10 2 ~3 × 10} 5 cells / mm ²
The part where the Si particles exist on the surface of the sacrificial anode material suppresses the formation of an oxide film, resulting in a film defect, and at the brazing temperature, the matrix near the Si particles has a low melting point due to Si diffusion, and the wettability with the brazing material Is improved, and the bondability of the inner column portion of the tube is improved. Further, since the Si particles generate a defective portion of the oxide film, the surrounding area becomes a starting point of corrosion, and the corrosion form becomes planar. Within the scope of the present invention, these dispersed particles serve as a starting point of corrosion, and the generation of through holes due to local pitting corrosion is suppressed, and excellent pitting corrosion resistance is obtained.

  However, when the size of the Si particles is less than 0.1 μm in the equivalent circle diameter, the effect of generating a defective portion of the film cannot be obtained, and when the equivalent circle diameter is greater than 1.0 μm, the periphery of these particles is corroded. As a result, the pitting size increases and deep pitting occurs. Therefore, it is necessary to pay attention to the distribution density of Si particles having an equivalent circle diameter of 0.1 to 1.0 μm.

If the number of Si particles of the size is less than 3 × 10 ² cells in 1 mm ² per, the corrosion form because less starting point of corrosion does not become planar, deep pitting occurs. On the other hand, when the number of Si particles per 1 mm ² is more than 3 × 10 ⁵ , the corrosion rate increases, so that the self-corrosion property of the sacrificial anode material increases, and the action of the sacrificial anode material is lost early. Therefore, it is desirable that the distribution density of the Si particles of the above size is 3 × 10 ^{2 to} 3 × 10 ⁵ particles / mm ² . Incidentally, the distribution density is preferably the lower limit 5 × 10 ² cells / mm ^2, even more preferably set to a 1 × 10 ⁵ cells / mm ² limit.

That is, according to the aluminum alloy clad material excellent in strength and pitting corrosion resistance of the present invention, the aluminum alloy brazing material is clad on one side of the aluminum alloy core material, and the sacrificial anode material is clad on the other side of the core material. In the aluminum alloy clad, the sacrificial anode material includes, in mass%, Zn: 0.5 to 10.0%, Si: 0.8 to 1.5%, Mg: 0.005 to 0.2%, If desired, Ni: 0.1 to 1.5%, optionally Ti: 0.05 to 0.3%, Zr: 0.05 to 0.3% of one or two or more, The balance is made of Al and inevitable impurities, and the proportion of Fe and Si in the inevitable impurities satisfies the relationship of Fe amount (wt%) ≦ 1/4 × Si amount (wt%), and more preferably The equivalent circle diameter in the matrix is 0. Since Si particles ~1.0μm is 1 mm ² per 3 × ¹⁰ 2 ~3 × ^{10 5} cells distributed in the brazing property and pitting corrosion resistance is remarkably superior, automobile radiators, tube such as a heater core It can be suitably applied to materials and header plate materials, and has the effect of greatly contributing to the improvement of the life of the heat exchanger.

  The aluminum alloy clad material for a heat exchanger according to the present invention is typically formed by ingot-making aluminum alloy constituting the core material, the sacrificial anode material and the brazing material by semi-continuous casting, and the core material and the sacrificial anode material are homogenized. Then, each is hot rolled to a predetermined thickness. Each plate material can be obtained by continuous casting and rolling. As the sacrificial anode material, an aluminum alloy prepared in the above-described composition is used. In addition, the composition of the core material is not limited to a specific one in the present invention, and usually an Al-Mn-Cu alloy or Al-Mn-Cu-Si alloy having excellent strength characteristics is used. It is done. Further, the composition of the brazing material is not limited to a specific one in the present invention, but an Al—Si based alloy or an Al—Si—Zn based alloy generally used as a brazing material can be used. .

These materials are manufactured through a process of combining the core material, the sacrificial anode material, and the brazing material, forming a clad material by hot rolling, and finally cold rolling to a predetermined thickness.
The Si precipitates are formed in the sacrificial anode material in the manufacturing process of the clad material, but the size and distribution of the precipitates are mainly determined by the heat treatment conditions at the time of manufacture. Is preferred.

  The homogenization treatment of the sacrificial anode material is desirably held at a temperature of 350 to 550 ° C, more preferably 400 to 500 ° C for 2 hours or more. When the homogenization treatment is less than 350 ° C., precipitation of Si particles of 0.1 μm or less, which has a low contribution to the improvement of corrosion resistance, is promoted, and when it exceeds 500 ° C., coarse compounds of 1 μm or more are precipitated and deep from the same site. Pitting corrosion tends to occur. On the other hand, when the homogenization time is less than 2 hours, the precipitation of Si particles becomes insufficient and the effect is hardly obtained.

  Also, the distribution of Si precipitates changes during brazing heat treatment, but if normal brazing heat treatment (holding at 600 ° C. for 0.5 to 15 minutes and then cooling at a cooling rate of 100 ° C./min or less) is performed. Since Si precipitation occurs during brazing cooling and thereafter as a heat exchanger, a distribution state in the range described in the present invention can be obtained.

  The clad material 1 obtained above has an aluminum alloy brazing material 3 clad on one surface of the core material 2 and a sacrificial anode material 4 clad on the other surface of the core material 2 as shown in FIG. Yes. This aluminum alloy clad material 1 is bent into a tubular shape so that the sacrificial anode material 4 becomes the inner surface of the tube. In the form shown in FIG. 1, as shown in FIG. 1 (b), both end sides of the aluminum alloy clad material 1 are in close contact with the center portion of the inner surface to form the inner pillar portion 1 a, and the refrigerant path 5 is formed on both sides thereof. 5 is secured. Further, the aluminum alloy brazing material 3 located on the outer surface side of the pipe is subjected to brazing heating by bringing a fin (not shown) into close contact therewith. The heating conditions, atmosphere, and flux type in brazing are not particularly limited as the present invention. At the time of brazing, the sacrificial anode material 4 exhibits good wettability with the brazing, and the inner surface of the tube and the end of the aluminum alloy clad material 1 are well bonded by the formation of the fillets 6 and 6.

Invention materials and comparative materials were produced as aluminum alloy clad materials for heat exchangers by the following manufacturing process. Core material (JIS 3003 alloy: Al-1.0% Mn-0.15% Cu, balance Al and inevitable impurities), sacrificial anode material having the components shown in Table 1, and brazing material (JIS 4343 alloy: Al-7.5) % Si, balance Al and unavoidable impurities) are each agglomerated by semi-continuous casting, and homogenized by a condition of 600 ° C. × 6 hr for the core material and the conditions shown in Table 2 for the sacrificial anode material. Hot rolled to thickness.
After that, the sacrificial anode material, the core material, and the brazing material are combined with each other so that the cladding ratios are 15%, 75%, and 10%, respectively, to form a three-layer material by hot rolling, and hot to a thickness of about 6 mm. After rolling, a clad material having a thickness of 0.20 mm and a tempered H14 was prepared by cold rolling while appropriately performing intermediate annealing.

[Measurement of size and number of Si precipitates in sacrificial anode material]
The prepared clad material was subjected to a brazing heat treatment in which the clad material was held at 600 ° C. for 3 minutes in a high-purity nitrogen gas atmosphere, and then Si precipitates in the sacrificial anode material were measured by the following method.
After mechanically polishing the surface of the sacrificial anode material until the rolling marks disappear, electrolytic polishing was performed, and a composition image of the sacrificial anode material was photographed at a magnification of 2000 using EPMA (JXA-8900RL) manufactured by JEOL Ltd. Numbers and equivalent circle diameters were measured. Next, the components of the dispersed particles measured by particle analysis were identified. The number of Si precipitates with an equivalent circle diameter of 0.1 to 1.0 μm per 1 mm ² was 2000 times and 20 fields of view (total 0.05 mm ² ) were measured and calculated. The results are shown in Table 2.

[Corrosion test 1]
The clad material thus prepared was brazed and heat-treated at 600 ° C. for 3 minutes in a high-purity nitrogen gas atmosphere, and then cut into 50 mm length × 40 mm width to provide a test material for corrosion test. An acidic aqueous solution (pH 3.0) containing Cl ⁻ : 195 ppm, SO ₄ ²⁻ : 60 ppm, Fe ³⁺ : 30 ppm, Cu ²⁺ : 1 ppm is assumed as a corrosive liquid, and the test material is assumed to be cooling water for an automotive heat exchanger. After the immersion test was conducted for 4 weeks, the maximum pitting corrosion depth on the sacrificial anode material side was measured under an acidic environment. The pitting corrosion resistance of was evaluated. The results are shown in Table 2.

[Corrosion test 2]
The clad material thus prepared was brazed and heat-treated at 600 ° C. for 3 minutes in a high-purity nitrogen gas atmosphere, and then cut into 50 mm length × 40 mm width to provide a test material for corrosion test. Commercially available long-life coolant is added to tap water to a concentration of 10 vol%, and an alkaline solution adjusted to pH 11 with NaOH is used as a corrosive liquid, assuming a cooling water for an automobile heat exchanger at 80 ° C. for 8 hours. After holding, after performing the immersion test for 4 weeks while adding a temperature cycle of holding at room temperature for 16 hours, the maximum pitting corrosion depth on the sacrificial anode skin material side is measured, and the pitting corrosion resistance in an acidic environment is measured. evaluated. The results are shown in Table 2.

[Brassability]
The produced clad material is formed into a brazed tube tube having the cross-sectional shape shown in FIG. 1, and this tube is combined with a fin and a header plate, and a noclock flux is applied at about 3 g / m ^2, and then a high purity nitrogen gas atmosphere Brazing heat treatment was performed therein to produce a heat exchanger (tube width: 16 mm, number of tube stages: 32 stages, core size: 320 mm × 350 mmw).
Thereafter, a repeated pressurization test of 0.5 to 150 kPa was performed on the manufactured radiator, and the number of times until the tube was broken was measured. In the case where there is a joint failure even at one place in the tube column, the number of times until breakage is remarkably reduced, so that the brazing property can be evaluated by this test.

  As is apparent from Table 2, the material of the present invention exhibited excellent corrosion resistance in a wide pH range from acidic to alkaline environments, and also exhibited excellent characteristics in brazing.

It is a figure which shows the manufacture flow of the pipe | tube using the aluminum alloy clad material of one Embodiment of this invention. Similarly, it is sectional drawing which shows the pipe | tube manufactured using the conventional aluminum alloy clad material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum alloy clad material 2 Core material 3 Aluminum alloy brazing material 4 Sacrificial anode material

Claims (4)

  In an aluminum alloy clad in which an aluminum alloy brazing material is clad on one surface of an aluminum alloy core material and a sacrificial anode material is clad on the other surface of the core material, the sacrificial anode material is Zn in mass%. -10.0%, Si: 0.8-1.5%, Mg: 0.005-0.2%, the balance is made of Al and unavoidable impurities, and the amount of Fe and Si in the unavoidable impurities An aluminum alloy clad material excellent in strength and pitting corrosion resistance, characterized in that the ratio satisfies the relationship of Fe amount (wt%) ≦ 1/4 × Si amount (wt%). 2. The sacrificial anode material is characterized in that 3 × 10 ^{2 to} 3 × 10 ⁵ Si particles having an equivalent circle diameter of 0.1 to 1.0 μm are distributed per 1 mm ² in a matrix. Aluminum alloy clad material with excellent strength and pitting corrosion resistance.   The aluminum alloy clad material having excellent strength and pitting corrosion resistance according to claim 1 or 2, wherein the sacrificial anode material further contains 0.1% to 1.5% by mass of Ni.   The sacrificial anode material further includes one or more of Ti: 0.05 to 0.3% and Zr: 0.05 to 0.3% in mass%. An aluminum alloy clad material having excellent strength and pitting corrosion resistance according to any one of.

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