JP4401186B2 - Aluminum alloy brazing member - Google Patents

Description

  The present invention relates to an aluminum alloy brazing sheet used for a tube material of an evaporator for an automobile, and more particularly to an aluminum alloy brazing sheet which is improved in corrosion resistance after brazing.

  Generally, an aluminum alloy brazing sheet is used as a material for a heat exchanger for automobiles. An aluminum alloy brazing sheet is one in which a brazing material is disposed on at least one side of a core material made of an aluminum alloy, and the brazing material is melted by brazing additional heat and joined to another member. Such a brazing sheet is required to have corrosion resistance because it is exposed to a corrosive environment when assembled and used in a heat exchanger for automobiles. In particular, intergranular corrosion resistance is required.

  For this reason, much research has been made on the intergranular corrosion of aluminum alloys, and various effects have been investigated on the alloy species and additive elements of the material (see, for example, Non-Patent Documents 1 to 4). Moreover, in order to improve the intergranular corrosion resistance of a brazing sheet, the technique which provides the intermediate | middle layer which suppresses Si diffusion to a core material between a brazing material and a core material is known (for example, refer patent document 1). .)

Light Metal Society 102nd Spring Proceedings, 2002, p. 197-198 Light Metal Society 99th Autumn Proceedings, 2000, p. 275-276 Light metal, 1981, p. 116-121 Basics of aluminum materials and industrial technology, edited by the Association of Light Metals, 1991, p. 201-205) JP 7-179969 A

  However, the conventional techniques described above have the following problems. That is, even with the above technique, the corrosion resistance of the aluminum alloy brazing sheet may be insufficient. In particular, the intergranular corrosion resistance of the core material after brazing may not be sufficiently obtained.

The present invention has been made in view of such problems, and an object of the present invention is to provide an aluminum alloy brazing member that can suppress intergranular corrosion of a core material due to brazing heat and has excellent corrosion resistance.

The aluminum alloy brazing member according to the present invention comprises a core material made of an Al-Mn alloy containing Al and Mn, and an Al-Si alloy containing Al and Si provided on at least one side of the core material. A brazing sheet made of an aluminum alloy, comprising: a brazing material; and a sacrificial material made of 1000 series Al alloy or 7000 series Al-Zn alloy provided between the core material and at least one brazing material and defined by JIS Z3232. In an aluminum alloy brazing member obtained by brazing and heating
In the core material, a Si non-diffusion part having a Si concentration of less than 0.10% by mass and a thickness of 10 μm or more remains,
The aluminum alloy brazing sheet is
The core material contains Mn: 0.3 to 1.8% by mass, Cu: 0.2 to 1.0% by mass, Mg: 0.5% or less, Fe: 0.5% by mass or less, Ti: 0.3% by mass or less, Cr: containing at least one of 0.3% by mass or less, with the balance being composed of Al and inevitable impurities, with a thickness of 0.19 to 0.30 mm Yes,
The sacrificial material has a composition containing Zr: 0.3% by mass or less and has a thickness of 0.055 to 0.12 mm.

  In the present invention, the sacrificial material functions as a barrier layer that suppresses diffusion of Si from the brazing material to the core material, and after the brazing heating, a Si non-diffused portion having a thickness of 10 μm or more remains in the core material. Thereby, the intergranular corrosion of a core material is suppressed and the corrosion resistance of the whole aluminum alloy brazing sheet improves. In addition, a potential difference of a certain value or more is formed between the core material and the sacrificial material, and the corrosion resistance of the core material is improved.

Thus, according to the present invention, after the aluminum alloy brazing sheet and brazing, by Si No diffusion portion remains at more than 10μm thick in the core, the grain boundary corrosion of the core is suppressed, The corrosion resistance of the brazing member can be improved.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an aluminum alloy brazing sheet according to the present embodiment. In FIGS. 2A to 2C, the horizontal axis indicates the position in the thickness direction, and the vertical axis indicates the concentration of each component. FIG. 2 is a graph showing the composition distribution of a brazing sheet made of aluminum alloy after brazing, in which (a) shows a brazing sheet with a sacrificial material thickness of 80 μm before brazing, and (b) shows a brazing sheet before brazing. The sacrificial material has a brazing sheet with a thickness of 60 μm, and (c) shows a brazing sheet with a sacrificial material having a thickness of 50 μm before brazing. In FIGS. 3A to 3C, the horizontal axis represents the distance in the plate thickness direction from the brazed sheet surface, and the vertical axis represents the pitting potential with respect to the reference electrode (Ag / AgCl electrode). It is a graph which shows the electric potential distribution of the brazing sheet | seat made from an aluminum alloy after brazing, (a) shows the brazing sheet | seat whose thickness of the sacrificial material before brazing is 80 micrometers, (b) is before brazing. (C) shows a brazing sheet with a sacrificial material thickness of 50 μm before brazing.

As shown in FIG. 1, in the brazing sheet 1 made of aluminum alloy according to this embodiment, a core material 2 is provided. The core material 2 is made of an Al—Mn alloy, and the composition thereof is, for example, that the Mn content is 0.3 to 1.8 mass%, the Cu content is 0.2 to 1.0 mass%, and the Mg content is The amount is 0.5% or less, and contains 0.5% by mass or less of Fe, 0.3% by mass or less of Ti, and 0.3% by mass or less of Cr, with the balance being Al. And inevitable impurities. The thickness of the core material 2 is, for example, 0.19 to 0.30 mm.

A sacrificial material 3 is provided on one side of the core material 2. The sacrificial material 3 is made of, for example, a 1000 series Al alloy or a 7000 series Al—Zn alloy defined by JIS Z3232, and includes at least one of, for example, 3 mass% or less of Zn and 0.3 mass% or less of Zr. Made of aluminum alloy. The thickness of the sacrificial material 3 is, for example, 0.055 to 0.12 mm, and the clad rate of the sacrificial material 3 is, for example, 10 to 30%.

  Further, the brazing material 4 is provided on the surface of the core material 2 on which the sacrificial material 3 is not provided, and the brazing material 5 is provided on the surface of the sacrificial material 3 on the side not in contact with the core material 2. . That is, the brazing sheet 1 is a four-layer material in which a brazing material 5, a sacrificial material 3, a core material 2, and a brazing material 4 are clad in this order. The brazing materials 4 and 5 are made of an Al—Si alloy, for example, an Al—Si alloy containing 11% by mass of Si and 1.5% by mass of Mg, with the balance being Al and inevitable impurities. Is, for example, 0.04 to 0.06 mm, respectively, and the cladding ratio is, for example, 11 to 13%. Moreover, the thickness of the whole brazing sheet 1 is 0.4 mm, for example.

  Next, a method for manufacturing the brazing sheet 1 configured as described above will be described. First, an Al-Mn alloy ingot for the core material 2, an Al alloy ingot for the sacrificial material 3, an Al-Si alloy ingot for the brazing material 4, and an Al-Si alloy ingot for the brazing material 5 Each lump is made. Next, each of these ingots is rolled to a predetermined plate thickness to obtain a plate material. Next, each plate material is made of an Al—Si alloy plate material for the brazing material 5, an Al alloy plate material for the sacrificial material 3, an Al—Mn alloy plate material for the core material 2, and an Al—Si alloy material for the brazing material 4. The plates are stacked in order and welded together. Next, the laminated plate material is subjected to heat treatment. This heat treatment is, for example, a treatment that is held at a temperature of 420 ° C. for 1 hour. Next, this stacked plate material is hot-rolled to a thickness of, for example, 5 mm, and then cold-rolled to a thickness of, for example, 0.4 mm. Next, for example, annealing is performed at a temperature of 400 ° C. for 3 hours. Thereby, the brazing sheet 1 according to the present embodiment is manufactured.

  Next, a brazing method using the brazing sheet 1 will be described. First, a non-corrosive flux is applied to the surface of the brazing sheet 1. Next, the brazing sheet 1 is pressed against another member (not shown) to be joined through this non-corrosive flux. Then, the brazing sheet 1 and the other members are subjected to brazing heat treatment. The brazing heat treatment may be performed under conventional general conditions. For example, the brazing heat treatment is performed in a non-oxidizing atmosphere at a temperature of 590 to 610 ° C. for 3 to 5 minutes. Thereby, the brazing material is melted, and the core material 2 or the sacrificial material 3 of the brazing sheet 1 and the other members are brazed to each other.

  As shown in FIGS. 2 (a) to 2 (c), in the brazing sheet 1 after brazing heating, the Si content is 0.10% by mass or less and the thickness is 10 μm or more inside the core material 2. A certain Si non-diffusion part 6 exists. Thereby, the corrosion resistance of the brazing sheet 1 after brazing is ensured. Further, as shown in FIGS. 3A to 3C, in the brazing sheet 1 after brazing heating, the pitting potential with respect to the reference electrode (Ag / AgCl electrode) is different between the core material 2 and the sacrificial material 3. There is a certain potential difference between the two materials. Thereby, the corrosion resistance of the brazing sheet 1 after brazing is further improved.

  Hereinafter, the reason for the numerical limitation in each constituent requirement of the present invention will be described.

Thickness of Si non-diffusion part (Si: less than 0.10% by mass) after brazing heat : 10 μm or more The diffusion state of Si accompanying brazing heating is determined by the value of each parameter of the brazing sheet . For example, in a brazing sheet provided with a sacrificial material as an intermediate layer, the Si content in the core material, the Si content in the brazing material, the plate thickness ratio (cladding ratio) of the core material in the total plate thickness, The Si content and cladding ratio, as well as the temperature and time during brazing are affected.

  However, in the present invention, in the brazing sheet after brazing and heating, at least 10 μm or more of the Si non-diffusion part, that is, the layer in which the Si content is less than 0.10% by mass is required in the core material. If the thickness of the Si non-diffused portion is less than 10 μm, the core material cannot secure a difference in pitting potential between the intermediate layer or the brazing material layer and the intergranular corrosion sensitivity is increased. Is significantly reduced. Therefore, the thickness of the Si non-diffusion part after the brazing heat needs to be 10 μm or more.

  Further, in the present invention, the composition of the core material and the sacrificial material is not particularly limited, but when a heat exchanger is produced using the brazing sheet of the present invention, a suitable range as the composition of the core material and the sacrificial material. Is shown below.

Mn content in core material: 0.3 to 1.8% by mass
Addition of Mn to the core material has an effect of improving the corrosion resistance and strength of the core material. However, if the Mn content in the core exceeds 1.8% by mass, coarse crystallized matter is formed in the core, and the workability of the core decreases. On the other hand, if the Mn content is less than 0.3% by mass, the effect of improving the strength is insufficient. Accordingly, the Mn content in the core material is preferably 0.3 to 1.8% by mass.

Cu content in core material: 0.2 to 1.0 mass%
The addition of Cu to the core material has the effect of improving the corrosion resistance and strength of the core material. However, if the Cu content in the core material exceeds 1.0 mass%, the melting point of the core material is lowered, and melting of the core material occurs during brazing. On the other hand, if the Cu content is less than 0.2% by mass, the effect of improving the strength is insufficient. Accordingly, the Cu content in the core material is preferably 0.2 to 1.0 mass%, more preferably 0.3 to 1.0 mass%.

Mg content in core material: 0.5% by mass or less Addition of Mg to the core material has the effect of improving the strength of the core material, but if the Mg content in the core material exceeds 0.5% by mass, the brazing sheet Mg diffuses on the surface of the steel and reduces brazing. Therefore, the Mg content in the core material is preferably 0.5% by mass or less, and more preferably 0.3% by mass or less.

Fe content in core material: 0.5% by mass or less Addition of Fe to the core material has the effect of reducing the crystal grains of the core material and improving the strength of the core material. However, when the Fe content in the core material exceeds 0.5 mass%, the corrosion resistance decreases. Therefore, the Fe content in the core material is preferably 0.5% by mass or less, and more preferably 0.3% by mass or less.

Cr content in the core material: 0.3% by mass or less Addition of Cr to the core material has an effect of improving the corrosion resistance, strength and brazing properties of the core material. However, if the Cr content in the core exceeds 0.3% by mass, the above-described effects are saturated and a coarse compound is formed, thereby lowering the workability and corrosion resistance of the core. Therefore, the Cr content in the core material is preferably 0.3% by mass or less.

Ti content in core material: 0.3 mass% or less The addition of Ti to the core material has the effect of further improving the corrosion resistance of the core material. However, if the Ti content in the core exceeds 0.3% by mass, the above effects are saturated and a coarse compound is formed, thereby reducing the workability and corrosion resistance of the core. Therefore, the Ti content in the core material is preferably 0.3% by mass or less.

Zr content in the sacrificial material: 0.3 mass% or less Zr has the effect of suppressing recrystallization during brazing and coarsening the grain size. Therefore, when an appropriate amount of Zr is added to the sacrificial material, Intrusion of eutectic Si in the part is suppressed, and the corrosion resistance can be further improved. However, if the Zr content in the sacrificial material exceeds 0.3% by mass, a coarse compound is formed and the moldability is lowered. Therefore, the Zr content in the sacrificial material is preferably 0.3% by mass or less.

  In the above-described embodiment of the present invention, the brazing sheet has an example of a four-layer structure of brazing material-core material-sacrificial material-brazing material, but the present invention is not limited to this. The structure of the brazing sheet may be, for example, a three-layer structure of core material-sacrificial material-brazing material, or a five-layer structure of brazing material-sacrificial material-heart material-sacrificial material-brazing material.

  Hereinafter, the effect of the present invention will be specifically described in comparison with a comparative example that is out of the scope of the claims. First, an aluminum alloy brazing sheet was prepared by the same method as in the above-described embodiment. That is, as shown in FIG. 1, an Al—Mn alloy ingot for the core material 2, an Al alloy ingot for the sacrificial material 3, an Al—Si alloy ingot for the brazing material 4, and the brazing material 5 Each of the ingots of Al-Si alloy was melted and rolled to a predetermined plate thickness to obtain a plate material. Note that two types of ingots (sacrificial material A and sacrificial material B) having different compositions were prepared as the ingots of the Al alloy for the sacrificial material 3.

  The plate material produced in this way is made of an Al—Si alloy plate material for the brazing material 5, an Al alloy plate material (sacrificial material A or sacrificial material B) for the sacrificial material 3, and an Al—Mn alloy plate material for the core material 2. Then, the Al—Si alloy plate materials for the brazing material 4 were stacked in this order, and welded together to produce a four-layer laminated material. At this time, the clad rate of the brazing material was 10%, the clad rate of the sacrificial material was 10 to 30%, and five kinds of laminated materials having different clad rates of the sacrificial material were produced. Next, these laminated materials were subjected to a heat treatment that was held at a temperature of 420 ° C. for 1 hour, hot-rolled to a thickness of 5 mm, and cold-rolled to a thickness of 0.4 mm. . Then, the final annealing which hold | maintains for 3 hours at the temperature of 400 degreeC was performed, and five types of clad materials were produced. Table 1 shows the compositions of the core material, the sacrificial material, and the brazing material. In addition, the unit of the numerical value shown in Table 1 is mass%.

Next, the obtained clad material was cut into a plate material having a width of 200 mm and a length of 220 mm. Next, a commercially available non-corrosive flux was applied to the entire surface of the plate material so that the coating amount was 5 g / m ² . Next, this plate material is suspended so that its longitudinal direction is vertical, and brazing is performed by maintaining the temperature at a temperature of 595 ° C. for 5 minutes in an atmosphere having an oxygen concentration of 200 ppm or less. A material was prepared. Thereafter, the brazing heat treatment material was cut out to prepare a sample, and a Si diffusion distance measurement, a corrosion resistance test, and a corrosion potential (pitting corrosion potential) measurement were performed.

  The Si diffusion distance was measured by X-ray microanalysis (EPMA: Electron Probe Micro-analysis) line analysis. Table 2 shows the thickness of the Si non-diffusion part having a Si concentration of less than 0.10% by mass.

  Regarding the corrosion resistance test, first, a rectangular test piece having a width of 50 mm and a length of 60 mm was cut out from the brazing heat treatment material. Next, the area | region and width | variety whole surface of the outer peripheral part (four sides) of the corrosion-resistant test surface in this test piece were sealed with the sealing tape, and the sample for corrosion resistance tests was produced. And the SWAAT test prescribed | regulated by ASTM G85-A3 was performed with respect to this sample for a corrosion test for 500 hours, the corrosion depth in the test piece after a test was measured, and corrosion resistance was evaluated. The evaluation results are shown in Table 2. In addition, “NG: penetration” shown in “Corrosion depth” in Table 2 indicates that the corroded portion has penetrated the brazing sheet. In this case, the corrosion depth is the thickness of the brazing sheet, that is, 0. 4 mm.

For measuring the corrosion potential, first, a rectangular test piece having a width of 20 mm and a length of 70 mm was cut out from the brazing heat treatment material. Next, the test piece was immersed in an aqueous NaOH solution having a concentration of 5%, and the test piece was etched to reduce the plate thickness so that the position where the corrosion potential was to be measured was exposed. Next, a sample for corrosion potential measurement was prepared by sealing the other region and the entire back surface, leaving a square region having a length of 10 mm and a width of 10 mm on the test surface. At this time, the square-shaped exposed region on the test surface serves as a potential measurement window. On the other hand, an AlCl ₃ aqueous solution having a concentration of 2.67% was prepared, and deaeration was performed by blowing nitrogen gas for 60 minutes or more. Then, the corrosion potential measurement sample and the Ag / AgCl electrode as the reference electrode are immersed in the AlCl ₃ aqueous solution after deaeration at a predetermined distance from each other, and the sweep rate is set to 0.33 mV / second. Eating potential was measured. And the electric potential difference of a core material and a sacrificial material was calculated | required. The results are shown in Table 2. The distance from the surface of the brazing sheet at the measurement position was confirmed by observing the test specimen after etching with a microscope.

  Of the Examples and Comparative Examples shown in Table 2, Example No. In Nos. 1 to 4, since the thickness of the Si non-diffused portion after brazing heating, that is, the thickness of the portion where the Si concentration is less than 0.10% by mass was 10 μm or more, the corrosion potential between the core material and the sacrificial material The potential difference was 50 mV or more, the corrosion depth was as small as 60 μm, and the corrosion resistance was good. In contrast, Comparative Example No. In Nos. 5 and 6, the thickness of the Si non-diffusion part was less than 10 μm, the potential difference of the corrosion potential between the core material and the sacrificial material was small, and corrosion penetrating the test piece occurred in the corrosion test. Thus, Comparative Example No. 5 and 6 were inferior in corrosion resistance.

It is sectional drawing which shows the brazing sheet made from an aluminum alloy which concerns on embodiment of this invention. (A) thru | or (c) is a graph which shows the composition distribution of the brazing sheet | seat made from aluminum alloy after brazing, taking the position of a plate | board thickness direction on a horizontal axis, and taking each component density | concentration on a vertical axis | shaft, a) shows a brazing sheet with a sacrificial material thickness of 80 μm before brazing, (b) shows a brazing sheet with a sacrificial material thickness of 60 μm before brazing, and (c) shows a sacrificial material before brazing. A brazing sheet having a thickness of 50 μm is shown. In (a) to (c), the horizontal axis represents the distance in the plate thickness direction from the surface after brazing of the brazing sheet, and the vertical axis represents the pitting corrosion potential with respect to the reference electrode (Ag / AgCl electrode). It is a graph which shows the electric potential distribution of the brazing sheet made from an aluminum alloy after brazing, (a) shows the brazing sheet whose thickness of the sacrificial material before brazing is 80 μm, and (b) shows the sacrificial material before brazing. A brazing sheet with a thickness of 60 μm is shown, and (c) shows a brazing sheet with a sacrificial material thickness of 50 μm before brazing.

Explanation of symbols

1; brazing sheet made of aluminum alloy 2; core material 3; sacrificial material 4, 5; brazing material 6;

Claims (1)

A core material made of an Al—Mn alloy containing Al and Mn; a brazing material made of an Al—Si alloy containing Al and Si provided on at least one side of the core material; and the core material and at least one of the aforementioned An aluminum alloy braze obtained by brazing and heating a brazing sheet made of an aluminum alloy having a sacrificial material made of 1000 series Al alloy or 7000 series Al-Zn alloy provided between the brazing material and defined by JIS Z3232 In the attachment member,
In the core material, a Si non-diffusion part having a Si concentration of less than 0.10% by mass and a thickness of 10 μm or more remains,
The aluminum alloy brazing sheet is
The core material contains Mn: 0.3 to 1.8% by mass, Cu: 0.2 to 1.0% by mass, Mg: 0.5% or less, Fe: 0.5% by mass or less, Ti: 0.3% by mass or less, Cr: containing at least one of 0.3% by mass or less, with the balance being composed of Al and inevitable impurities, with a thickness of 0.19 to 0.30 mm Yes,
An aluminum alloy brazing member, wherein the sacrificial material has a composition containing Zr: 0.3% by mass or less and has a thickness of 0.055 to 0.12 mm.

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