JP2006037137A - Highly corrosion resistant aluminum clad material for heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly corrosion resistant aluminum clad material for a heat exchanger suitably used for a tube material of a heat exchanger, particularly of an automobile heat exchanger such as a piping material (extruded clad pipe material) connected with a heat exchanger, a tube material of an automobile heat exchanger made of an aluminum alloy such as an evaporator, a condenser, a radiator, a heater core, an intercooler and an oil cooler joined by vacuum brazing or inert gas atmosphere brazing using fluoride-based flux, and a tube material for a heat exchanger connected by a non-brazing system such as adhesion, welding and soldering. <P>SOLUTION: The aluminum clad material is obtained by cladding at least one side of a core material composed of aluminum with a sacrificial anode material or obtained by cladding one side of a core material with a sacrificial anode material and cladding the other side with a brazing filler metal. The sacrificial anode material is composed of pure aluminum having an aluminum purity of ≥99.9% or an aluminum alloy at least containing Mg, wherein the total content of Al and Mg is ≥99.9%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to aluminum clad materials used in heat exchangers, particularly automobile heat exchangers, in particular piping materials (extruded clad pipe materials) connected to heat exchangers, vacuum brazing, fluoride fluxes and cesium fluoride fluxes. Non-brazing such as tubes, bonding, welding and soldering for aluminum alloy automotive heat exchangers such as evaporators, condensers, radiators, heater cores, intercoolers, oil coolers, etc. joined by brazing in an inert gas atmosphere The present invention relates to a highly corrosion-resistant aluminum clad material for a heat exchanger suitable as a tube material for a heat exchanger to be connected in a system.

  An automobile heat exchanger, for example, a radiator, includes a tube and a header having fins on the outer surface, and the inner surface serving as a passage for a working fluid (antifreeze). As a tube material and header plate material such as an automobile radiator or heater core, an Al-Mn alloy such as JIS A3003 is used as a core material, and an Al-Si alloy brazing material is clad on one side of the core material. Aluminum alloy clad material with a three-layer structure in which a brazing material is clad on one surface of the core material and a sacrificial anode material of Al-Zn alloy or Al-Zn-Mg alloy is clad on the other surface A clad material is used.

  When manufacturing an aluminum alloy heat exchanger, the clad Al-Si brazing material is used when a tube is manufactured by joining a tube and a fin, joining a tube and a header plate, or brazing a clad plate. It is clad for brazing. The sacrificial anode material is used, for example, on the inner surface side of the tube, and exerts a sacrificial anode action in contact with the working fluid, thereby preventing pitting corrosion and crevice corrosion of the core material.

  In recent years, with the demand for lighter automobiles, automobile heat exchangers are also required to be made thinner from the viewpoint of energy saving and resource saving, and the tube materials are also becoming thinner. In order to make the tube material thinner, it is necessary to further increase the strength of the material, and the core material contains a large amount of Cu, Si, Mn, etc., but the inclusion of these elements reduces the corrosion resistance of the core material. Therefore, a material configuration has been proposed in which a large amount of Zn is added to the sacrificial anode material to ensure a potential difference from the core material and to ensure the sacrificial anode effect.

  For example, one surface of a core material of an Al-Mn alloy containing Mn: 0.2 to 1.5% and Si: 0.3 to 1.3% as a tube material of an automotive heat exchanger such as a radiator Clad with an Al—Si alloy brazing material, clad with an Al—Zn alloy containing 5% or less of Zn on the other surface, and the Cu content of the core material is defined as 0.6% or less. Aluminum alloy having a potential difference between the core material after sacrificing and the sacrificial anode material of 30 to 120 mV, and excellent corrosion resistance especially when the heat exchanger is assembled in an inert gas atmosphere brazing using a fluoride-based flux A composite material has been proposed (see Patent Document 1).

  Moreover, about the sacrificial anode material clad by the core material which consists of an Al-Mn type alloy, Zn content (1-5%) of sacrificial anode material and the thickness (5-50 micrometers) of sacrificial anode material are combined, There is also an aluminum clad material suitable as a tube material for automotive heat exchangers that can provide excellent corrosion resistance after brazing while regulating the amount of Cu in the sacrificial anode material to 0.05% or less and enabling thinning. It has been proposed (see Patent Document 2).

  However, when a large amount of Zn is added to the sacrificial anode material, the sacrificial anode effect is achieved, but the sacrificial anode material has a high self-corrosion rate, and the sacrificial anode material may be consumed quickly. In the sacrificial anode material, Fe, Si and the like contained as impurities in the sacrificial anode material are dispersed as Al-Si compounds and Al-Fe compounds, and these compounds are exposed on the surface. These compounds become defects in the oxide film to maintain corrosion resistance, and these defects become the starting point of corrosion, causing corrosion. After corrosion occurs, these compounds become cathodes and the surroundings of the compounds are preferentially used. Corrodes and increases the corrosion rate.

The above phenomenon becomes particularly remarkable in the sacrificial anode material having a reduced thickness. Therefore, when the sacrificial anode material is reduced in order to reduce the thickness of the clad material, the sacrificial anode material is consumed in a short time due to the above phenomenon. When the cladding material is thinned, if the sacrificial anode material is not thinned and only the core material is thinned, it is difficult to maintain the rigidity of the cladding material.
Japanese Patent Laid-Open No. 6-23535 Japanese Patent No. 2572495

  The inventors tested the configuration of an aluminum clad material for a tube material that improves the self-corrosion resistance of the sacrificial anode material and also provides the sacrificial anode effect in order to eliminate the above-mentioned conventional problems in the tube material of the heat exchanger. As a result of repeated studies, the core material is composed of an aluminum alloy containing Mg, and Mg content in the core material is diffused into the sacrificial anode material during brazing heating due to the inclusion of Mg. Forming a uniform MgO oxide film and reducing the concentration of Fe and Si in the sacrificial anode material to reduce the formation of Al-Fe compounds and Al-Si compounds, thereby reducing the thickness of the cladding material Accordingly, it has been found that even when the thickness of the sacrificial anode material is reduced, both the self-corrosion resistance and the sacrificial anode effect of the sacrificial anode material can be maintained.

  The present invention has been made as a result of further investigation based on the above-described knowledge, and the object thereof is a tube material of a heat exchanger, particularly an automobile heat exchanger, for example, a pipe connected to the heat exchanger. Aluminum alloys such as evaporators, condensers, radiators, heater cores, intercoolers and oil coolers that are joined by brazing materials (extruded clad pipe materials), vacuum brazing, and inert gas atmosphere brazing using fluoride or cesium fluxes To provide a highly corrosion-resistant aluminum clad material for a heat exchanger that is suitably used as a tube material for a heat exchanger connected by a non-brazing method such as a tube material of an automobile heat exchanger, bonding, welding, soldering, etc. .

  A high corrosion resistance aluminum clad material for a heat exchanger according to claim 1 for achieving the above object is an aluminum clad material in which a sacrificial anode material is clad on at least one surface of a core material, and the core material contains at least Mg. The sacrificial anode material is made of pure aluminum having an aluminum purity of 99.9%.

  A highly corrosion-resistant aluminum clad material for a heat exchanger according to claim 2 is composed of an aluminum alloy according to claim 1, wherein the sacrificial anode material contains at least Mg, and the total content of Al and Mg is 99.9% or more. It is characterized by being.

  A highly corrosion-resistant aluminum clad material for a heat exchanger according to claim 3 is an aluminum clad material in which a sacrificial anode material is clad on one surface of a core material and a brazing material is clad on the other surface, and the core material contains at least Mg. The sacrificial anode material is made of pure aluminum having an aluminum purity of 99.9% or more.

  A highly corrosion-resistant aluminum clad material for a heat exchanger according to claim 4 is composed of an aluminum alloy according to claim 3, wherein the sacrificial anode material contains at least Mg, and the total content of Al and Mg is 99.9% or more. It is characterized by being.

  The highly corrosion-resistant aluminum clad material for heat exchanger according to claim 5 is characterized in that, in claim 2 or 4, the Mg content of the aluminum alloy constituting the sacrificial anode material is 0.01 to 5.0%. .

  A highly corrosion-resistant aluminum clad material for a heat exchanger according to claim 6 is characterized in that in any one of claims 1 to 5, the core material is composed of an aluminum alloy containing Mg: 0.01 to 5.0%. And

  According to the present invention, a tube material of a heat exchanger, in particular, an automotive heat exchanger, for example, a piping material (extruded clad tube material) connected to the heat exchanger, vacuum brazing, fluoride-based flux, or cesium-based flux is used. Non-brazing methods such as tubes, bonding, welding, and soldering for aluminum alloy automotive heat exchangers such as evaporators, condensers, radiators, heater cores, intercoolers, and oil coolers that are joined by brazing using inert gas atmosphere A highly corrosion-resistant aluminum clad material for a heat exchanger that is suitably used as a tube material for a heat exchanger that is connected in the above is provided.

Hereinafter, the structure of the aluminum alloy clad material of the present invention will be described.
(Sacrificial anode material)
The first embodiment is made of pure aluminum having an aluminum purity of 99.9% or higher. According to this embodiment, the generation of Al—Fe-based compounds and Al—Si-based compounds that are the starting point of corrosion is reduced, and the surface oxide film (protective film) is stably maintained with almost no film defects. Therefore, the occurrence of corrosion is suppressed. Even if corrosion occurs once, since there are few Al—Fe compounds and Al—Si compounds in the matrix acting as a cathode, the self-corrosion rate is slow, and the sacrificial anode effect of the sacrificial anode material lasts for a long time. If the aluminum purity is less than 99.9%, the effect is not sufficient and the corrosion resistance is lowered. A more preferable aluminum purity is 99.99% or more, and a further preferable aluminum purity is 99.999% or more.

In the second embodiment, the sacrificial anode material is composed of an aluminum alloy containing at least Mg and a total content of Mg and Al of 99.9% or more. For example, the sacrificial anode material is made of an Al—Mg alloy containing Mg, and the total content of Mg and Al is 99.9% or more. By containing Mg, a uniform oxide film (MgO) is formed on the surface of the sacrificial anode material, and by making the total content of Mg and Al 99.9% or more, the concentration of Fe and Si is lowered. Thus, the production of Al-Fe-based compounds and Al-Si-based compounds is reduced, and the MgO film has a better anticorrosive effect than the Al ₂ O ₃ film formed on the surface of ordinary aluminum alloys, and the surface oxide film Since it becomes a protective film and is stably held, there are almost no surface defects that become the starting point of corrosion, and the occurrence of corrosion is suppressed. Even if corrosion occurs once, the self-corrosion rate becomes slow because there are few Al-Fe compounds and Al-Si compounds in the matrix acting as the cathode.

  In addition, since the Fe and Si concentrations that lower the potential are low and Mg that lowers the potential is added, the potential of the sacrificial anode material is maintained at a lower level, and the sacrificial anode effect lasts for a long time. If the total content of Mg and Al is less than 99.9%, the effect is not sufficient and the corrosion resistance is lowered. A more preferable total content of Mg and Al is 99.99% or more, and a more preferable total content of Mg and Al is 99.999% or more.

  Mg in the sacrificial anode material functions to form a uniform oxide film (MgO) having an anticorrosive action on the surface of the sacrificial anode material and suppress the occurrence of corrosion. Further, the potential of the sacrificial anode material is made lower, the sacrificial anode effect on the core material is exhibited, and pitting corrosion and crevice corrosion of the core material are prevented. The preferred Mg content is in the range of 0.01 to 5.0%. If it is less than 0.01%, MgO formation tends to be insufficient, and if it exceeds 5.0%, the rollability is inferior and the clad material is sound. Is difficult to manufacture.

(Core material)
Aluminum or aluminum alloy containing at least Mg is applied as the core material, and the aluminum or aluminum alloy for the core material is selected according to the strength required in the heat exchanger. Generally, a 3000 series (Al-Mn series) alloy, 2000 series (Al-Cu series) alloy, 5000 series (Al-Mg series) alloy, 6000 series (Al-Mg series) when higher strength is required. -Si-based) alloys can be applied, and Mg is added to these aluminum alloys to form a core alloy. An 8000 series alloy containing Mg can also be used.

  In the present invention, Mg or aluminum alloy containing Mg is applied as a core material to diffuse Mg in the core material into the sacrificial anode material during brazing heating, thereby forming an MgO film on the surface of the sacrificial anode material. Let Since the concentration of Fe and Si contained as impurities in the sacrificial anode material is extremely low, there are few Al—Fe compounds and Al—Si compounds, and there are almost no surface defects that can cause corrosion. Is maintained in a uniform state, and the protective action of the film delays the occurrence of corrosion. Even if corrosion occurs once, since the sacrificial anode material contains few Al—Fe compounds and Al—Si compounds, the progress of corrosion is slow and corrosion resistance can be maintained.

In order to diffuse Mg in the core material into the sacrificial anode material and form a uniform MgO film on the surface of the sacrificial anode material, the heat pattern during brazing heating is expressed as the time integral of the diffusion coefficient of Mg, ∫D ( t) dt (D (t) = D ₀ e × p {−Q / RT (t)}, D ₀ : frequency term (1.24 × 10 ⁻⁴ m ² / s), Q: activation energy ( 131000 J / mol), R: gas constant (8.3145 J / mol · K), T: temperature (K), t: time (s)) are controlled to be 9.0 × 10 ⁻¹² (m ² ) or more. In addition, it is desirable that the maximum temperature achieved during brazing is 773 K or higher.

When bonding is not performed by brazing, but by bonding, welding, soldering, or the like, the heat pattern during the final heat treatment of the aluminum clad material is set to 9.0 × 10 ⁻¹² (time integral of the diffusion coefficient of Mg) It is desirable that the temperature is controlled so as to be m ² ) or higher, and the maximum temperature achieved during heat treatment is 473 K or higher.

  A preferred core material in the present invention contains at least Mg, Mn: more than 1.5% and 2.0% or less, Cu: more than 0.5% and 1.0% or less, Si: 0.00. An Mg-containing Al—Mn alloy containing one or two of more than 6% and not more than 1.5%. In this composition, the strength of the core material can be further improved and the thickness can be reduced. Therefore, the corrosion resistance can be obtained more stably and better. Ti of 0.3% or less, Zr of 0.3% or less, and Cr of 0.2% or less may be contained.

(Brazing material)
As the brazing material, a commonly used Al—Si based brazing material, for example, an Al—Si based brazing material containing 6 to 13% of Si is used. When the heat exchanger is joined by vacuum brazing, an Al—Si—Mg alloy brazing material containing Mg is applied. These Al—Si based alloy brazing material and Al—Si—Mg based brazing material include, for example, 0.005 to 0.1% Sr, 0.2% or less Bi, 0.1% or less Be, One or two of 0.001 to 0.05% In, 0.001 to 0.05% Sn, 1 to 100 ppm Na, 2% or less Fe, 8% or less Zn, 5% or less Cu More than one species may be contained.

  The aluminum clad material of the present invention is formed by agglomerating the aluminum material constituting the core material, the sacrificial anode material and the brazing material, for example, by continuous casting, and after homogenizing treatment as necessary, casting of the sacrificial anode material and the brazing material. Each ingot is hot-rolled to a predetermined thickness, and then the ingot of the core material and the hot-rolled material of the sacrificial anode material are combined, or the ingot of the core material, hot-rolled material of the sacrificial anode material, brazing material These hot-rolled materials are combined into a clad material by hot rolling according to a conventional method, and then made into a predetermined thickness by cold rolling, intermediate annealing, and cold rolling.

  Examples of the present invention will be described below in comparison with comparative examples. These examples show one embodiment of the present invention, and the present invention is not limited to these examples.

Example 1
The core alloy having the composition shown in Table 1 and the sacrificial anode material alloy having the composition shown in Table 2 were ingoted by continuous casting, and the resulting ingot was homogenized.

  Next, the ingot of the sacrificial anode material alloy is hot-rolled to a predetermined thickness, and the obtained hot-rolled sheet and the core alloy ingot are hot-rolled in combination, followed by cold rolling and intermediate annealing. Then, a clad material (tempered H14) having a thickness of 0.20 mm was obtained by cold rolling. The structure of the clad material was 0.010 to 0.020 mm thick for the sacrificial anode material.

  Using the obtained clad material as a test material, the corrosion resistance of the sacrificial anode material was evaluated by the following method. The results are shown in Tables 3-6.

Corrosion resistance of sacrificial anode material: The obtained clad material (test material) was applied as a single plate with fluoride-based flux and heated to a brazing temperature of 600 ° C. (material temperature) in a nitrogen gas atmosphere. A corrosion test was performed on the anode material surface under the following conditions.
Corrosion solution: Cl ⁻ : 300 ppm, SO ₄ ²⁻ : 100 ppm, Cu ²⁺ : 10 pm
Specific liquid volume: 5 mL / cm ²
Seal: The core material surface and end surface were sealed with silicon resin.
Test method: After immersing in a caustic solution heated to 88 ° C. for 8 hours, a cycle of cooling and holding at 25 ° C. for 16 hours was repeated for 2 months, the maximum corrosion depth was measured, and the maximum corrosion depth was 0. The corrosion resistance was good at 03 mm or less.

  As seen in Tables 3-6, the test material No. All of Nos. 1 to 65 have a maximum corrosion depth of 0.025 mm or less in the corrosion test of the sacrificial anode material, and have excellent corrosion resistance.

Comparative Example 1
An alloy for a sacrificial anode material having a composition shown in Table 7 was formed by continuous casting, and the resulting ingot was homogenized.

  Subsequently, the ingot of the alloy for sacrificial anode material was hot-rolled to a predetermined thickness, and the obtained hot-rolled plate of the sacrificial anode material and No. 1 in Table 1 were used. A hot-rolling was performed by combining ingots of the core material alloy of A2, and then a clad material (tempered H14) having a thickness of 0.20 mm was obtained by cold rolling, intermediate annealing, and cold rolling. The structure of the clad material was such that the sacrificial anode material was 0.020 mm thick. In Table 7, those outside the conditions of the present invention are underlined.

  The corrosion resistance of the sacrificial anode material was evaluated by the same method as in Example 1 using the obtained clad material as a test material. The results are shown in Table 8.

  As shown in Table 8, the test material No. No. 66 has a low total content of Mg and Al in the sacrificial anode material. In No. 67, since the sacrificial anode material contains 2% Zn and the total content of Mg and Al is low, the sacrificial anode material is inferior in corrosion resistance.

Claims (6)

An aluminum clad material in which a sacrificial anode material is clad on at least one surface of a core material, the core material is made of an aluminum alloy containing at least Mg, and the sacrificial anode material has an aluminum purity of 99.9% (mass%, below) High corrosion-resistant aluminum clad material for heat exchangers, characterized in that it is made of pure aluminum. 2. The highly corrosion-resistant aluminum clad for heat exchanger according to claim 1, wherein the sacrificial anode material is composed of an aluminum alloy containing at least Mg and a total content of Al and Mg of 99.9% or more. Wood. An aluminum clad material in which a sacrificial anode material is clad on one surface of a core material and a brazing material is clad on the other surface, and the core material is composed of an aluminum alloy containing at least Mg, and the sacrificial anode material has an aluminum purity A highly corrosion-resistant aluminum clad material for heat exchangers, characterized by being composed of 99.9% or more pure aluminum. 4. The highly corrosion-resistant aluminum clad for heat exchanger according to claim 3, wherein the sacrificial anode material is composed of an aluminum alloy containing at least Mg and a total content of Al and Mg of 99.9% or more. Wood. The highly corrosion-resistant aluminum clad material for heat exchanger according to claim 2 or 4, wherein Mg content of the aluminum alloy constituting the sacrificial anode material is 0.01 to 5.0%. The high corrosion-resistant aluminum clad material for heat exchanger according to any one of claims 1 to 5, wherein the core material is made of an aluminum alloy containing Mg: 0.01 to 5.0%.