JP2000212668A - Aluminum alloy extruded tube for heat exchanger excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extruded tube excellent in corrosion resistance to pH in a wide range from weakly acidic to alkaline and used as a tube material for a heat exchanger or the like. SOLUTION: This tube is composed of an Al alloy contg. 0.1 to 3% Zn, 0.01 to 0.5% Ce and 0.05 to 0.2% Mg and moreover added with one or >= two kinds among the following (a) to (d): (a) 0.3 to 1.5% Fe, (b) 0.1 to 1.0% Mn, (c) one or two kinds of 0.05 to 0.7% Cu and 0.1 to 1.0% Si and (d) one or two kinds of 0.01 to 0.25% Ti and 0.01 to 0.25% Zr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy extruded tube used as a structural member for a heat exchanger or the like which has excellent corrosion resistance, particularly in a wide pH range from an alkaline environment to an acidic environment. , Especially L
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy extruded pipe having excellent corrosion resistance and usable as a structural member of a heat exchanger such as a radiator, a heater core, and an oil cooler for automobiles, which uses cooling water containing LC (long life coolant) as a refrigerant.

[0002]

2. Description of the Related Art Conventionally, as a tube of a radiator or a heater core of an automobile, an Al-Si-based or Al-Si-Zn-based brazing material is clad on one side of a core material made of an Al-Mn-based alloy to form a core material. A welded tube obtained by brazing or high-frequency welding a three-layer brazing sheet clad with an Al—Zn-based alloy as a sacrificial anode skin material on one side is used. The welded pipe obtained by brazing or high-frequency welding this brazing sheet is excellent in corrosion resistance because the sacrificial anode skin material is formed inside, but is manufactured by brazing or high-frequency welding the brazing sheet. Therefore, it is difficult to weld a thin plate, and there is a limit to thinning. Further, in these methods, there are problems such as a decrease in strength of the welded portion and leakage of the refrigerant due to corrosion of the welded portion.

[0003] Furthermore, the production of the clad material requires extremely expensive rolling equipment and excellent rolling techniques, and has a problem that the production cost is too high due to the large number of steps up to production. Tubes for automotive heat exchangers are required to improve performance and reduce costs.In particular, when manufacturing new equipment, it is better to weld extruded aluminum alloy to produce extruded tubes. There is an advantage that manufacturing cost is significantly lower than manufacturing.

For an extruded tube having a complicated cross-section having a partition wall inside, it is necessary to give priority to extrudability. Therefore, at present, a pure Al-based alloy represented by JIS 1050 alloy or higher than a pure Al-based alloy is used. JIS 300 of strength
3 alloy (wt%, Mn: 1.0-1.5%, Fe:
0.05 to 0.20%, Si: 0.6% or less, Zr:
An Al-Mn alloy represented by 0.7% or less, Zn: 0.10% or less, and balance: Al and inevitable impurities) is used.

[0005]

However, the pure Al
Since the extruded pipes made of the Al-Mn-based alloy and the Al-Mn-based alloy both have a pitting corrosion type and poor corrosion resistance, the pure Al
Tubes made of extruded tubes made of aluminum alloy and Al-Mn alloy are limited to heat exchangers that use gases or liquids such as chlorofluorocarbon as refrigerant, and contain a small amount of chlorine ions as refrigerant It is not suitable as a component of a tube of a heat exchanger that uses weakly acidic tap water or weakly acidic rainwater caused by acid rain or the like. In recent years,
Cooling water obtained by adding LLC (Long Life Coolant) composed of antifreeze and rust inhibitor to water is used as a coolant. However, if this LLC is a poor product, it has been found that the cooling water becomes alkaline with a pH of 9 or more. Therefore, in an environment where cooling water containing the poor LLC (long life coolant) is used, a through hole is generated early,
Current extruded tubes are not suitable as heat exchanger components.

[0006] The present invention also allows the use of weakly acidic tap water or rainwater or alkaline cooling water containing poor LLC as a refrigerant (ie, for aqueous solutions in a wide pH range from weakly acidic solutions to alkaline solutions). The purpose of the present invention is to provide an extruded tube for producing a tube of a heat exchanger which exhibits excellent corrosion resistance.

[0007]

Means for Solving the Problems The present inventors have conducted studies to obtain an aluminum alloy extruded tube which is more excellent in corrosion resistance to an aqueous solution in a wide pH range from a weakly acidic solution to an alkaline solution. B) In weight percent, Zn:
0.1-3%, Ce: 0.01-0.5%, Mg: 0.
An Al alloy containing 0.05 to 0.2%, with the balance being Al and unavoidable impurities, can be extruded, and an extruded tube obtained by extruding this Al alloy has a weak acidic solution. Excellent corrosion resistance to aqueous solutions in a wide range of pH from aqueous to alkaline solutions. (B)
An Al alloy having a composition obtained by further adding one or more of the following (a) to (d) to the Al alloy having the composition described in (a) above can also be extruded. An extruded tube obtained by extruding these Al alloys has excellent corrosion resistance to aqueous solutions in a wide pH range from a weakly acidic solution to an alkaline solution. (A) Fe:
0.3-1.5%, (b) Mn: 0.1-1.0%,
(C) Cu: 0.05-0.7%, Si: 0.1-1.
One or two of 0%, (d) Ti: 0.01 to
It was found that one or two of 0.25% and Zr: 0.01 to 0.25%.

The present invention has been made based on this finding, and (1) Zn: 0.1 to 3% by weight.
%, Ce: 0.01-0.5%, Mg: 0.05-0.
An aluminum alloy extruded tube for heat exchangers having excellent corrosion resistance, comprising an Al alloy having a composition of 2% and the balance of Al and unavoidable impurities. (2) By weight%, Zn: 0.1
-3%, Ce: 0.01-0.5%, Mg: 0.05-
A having a composition of 0.2%, further containing Mn: 0.1-1.0%, with the balance being Al and unavoidable impurities.
Aluminum alloy extruded tube for heat exchanger with excellent corrosion resistance, consisting of 1 alloy, (3) wt%, Zn: 0.1-3%,
Ce: 0.01-0.5%, Mg: 0.05-0.2%
, Further containing 0.1 to 1.0% of Si and 0.1 to 0.3% of Cu.
An aluminum alloy extruded tube for heat exchangers having excellent corrosion resistance, comprising an Al alloy having a composition consisting of Al and unavoidable impurities, the aluminum alloy extruded tube containing one or two of the above components from 0.05 to 0.7%; , Zn: 0.1-3%, Ce: 0.
01-0.5%, Mg: 0.05-0.2%,
Further, Mn: 0.1 to 1.0% is contained, and further Si:
0.1 to 1.0%, Cu: 1 of 0.05 to 0.7%
Aluminum alloy extruded tube for heat exchanger, which has excellent corrosion resistance and is made of an Al alloy having a composition consisting of Al and unavoidable impurities, the balance being Z
n: 0.1 to 3%, Ce: 0.01 to 0.5%, Mg:
0.05-0.2%, Fe: 0.3-
An aluminum alloy extruded tube for heat exchangers having an excellent corrosion resistance, comprising an Al alloy having a composition of 1.5%, with the balance being Al and unavoidable impurities. (6)
0.1-3%, Ce: 0.01-0.5%, Mg: 0.
0.05 to 0.2%, and further Fe: 0.3 to 1.5%.
%, Further containing Mn: 0.1-1.0%,
Aluminum alloy extruded tube for heat exchanger with excellent corrosion resistance, made of an Al alloy having a composition consisting of Al and unavoidable impurities, (7) wt%, Zn: 0.1-3%, Ce:
0.01 to 0.5%, Mg: 0.05 to 0.2%, Fe: 0.3 to 1.5%, and S
i: 0.1 to 1.0%, Cu: 0.05 to 0.7%, one or two of which are contained, and the balance is excellent in corrosion resistance made of an Al alloy having a composition of Al and unavoidable impurities. Aluminum alloy extrusion tube for heat exchanger, (8) wt%
Zn: 0.1-3%, Ce: 0.01-0.5%, M
g: 0.05 to 0.2%, and further Fe: 0.3
-1.5%, Mn: 0.1-1.0%, Si: 0.1-1.0%, Cu: 0.0
Containing one or two of 5 to 0.7%,
aluminum alloy extruded tubes for heat exchangers having excellent corrosion resistance comprising an Al alloy having a composition of l and unavoidable impurities,
(9) The above (1), (2), (3), (4), (5),
(6), (7) or (8), in addition to Ti: 0.01 to 0.25%, Zr: 0.01 to 0.2
It is characterized by an aluminum alloy extruded tube for a heat exchanger having excellent corrosion resistance and made of an Al alloy having a composition containing one or two of 5%.

The above (1), (2), (3), (4),
(5), (6), (7), (8) or (9), the outer surface of the extruded aluminum alloy tube described above is sprayed with Zn to produce a cladding tube, and the cladding tube is used as a tube material for a heat exchanger. Can be used as Therefore, the present invention provides (1)
0) The above (1), (2), (3), (4), (5),
(6), (7), (8) or (9), characterized in that the aluminum alloy extruded tube for a heat exchanger, which is excellent in corrosion resistance, is obtained by spraying Zn on the outer surface of the extruded aluminum alloy tube. .

The above (1), (2), (3), (4),
(5), (6), (7), (8) or (9), an aluminum alloy extruded tube described in (9), a brazing powder is applied to the outer surface of the extruded tube to prepare a cladding tube. It can be used as a tube material. Therefore, the present invention provides (11) the above (1), (2), (3), (4),
(5), (6), (7), (8) or (9), an aluminum alloy extruded tube for a heat exchanger having excellent corrosion resistance obtained by applying a brazing powder to the outer surface of the extruded aluminum alloy tube. It has features.

[0011] The aluminum alloy extruded tube for heat exchangers, which is formed by coating Zn on the outer surface of the aluminum alloy extruded tube according to the above (10) and has excellent corrosion resistance, or the aluminum alloy extruded tube according to the above (11). Any of the aluminum alloy extruded pipes for heat exchangers having excellent corrosion resistance formed by applying powdered brazing material can be joined to the fins and the header plate by brazing to produce a heat exchanger having excellent corrosion resistance.

The reason why the composition of the extruded aluminum alloy tube for a heat exchanger having excellent corrosion resistance of the present invention is limited as described above will be described. Zn: Zn forms an Mg-Zn intermetallic compound with Mg to improve the strength, and the fine precipitates of the Mg-Zn intermetallic compound become a source of pitting corrosion and become a form of surface corrosion. Although it is a component that improves corrosion resistance, if its content is less than 0.1%, the desired effect cannot be obtained.
If the content exceeds the above range, the corrosion resistance is undesirably reduced. Therefore, the content of Mn is set to 0.1 to 3%. A more preferred range for the Zn content is 0.2-1%.

Ce: Ce has a function of improving strength in order to make crystallized substances at the time of casting finer and further promote precipitation of a solute element which is supersaturated during brazing. Causes a large number of origins of pits to be generated, which has the effect of suppressing the generation of huge pits due to the form of corrosion of the surface pits, and greatly improves the corrosion resistance particularly in an alkaline environment. However, if the content is less than 0.01%, the desired effect cannot be obtained.
If it exceeds 0.5%, the self-corrosion property is increased, the corrosion resistance is lowered, and the extrusion processability is lowered, which is not preferable.
Therefore, the content of Ce is set to 0.01 to 0.5%. A more preferred range for the content of Ce is 0.03 to
0.2%.

Mg: Mg forms an Mg-Zn intermetallic compound with Zn, and when Si is present, Mg-Si
While forming an intermetallic compound to improve the strength, fine Mg-Zn intermetallic compound has the effect of improving the corrosion resistance because it has the effect of precipitating the form of corrosion because it precipitates on the entire material surface. If the content is less than 0.05%, the desired effect cannot be obtained. On the other hand, if the content exceeds 0.2%, it reacts with the flux at the time of brazing to form a high-melting-point film, so that the brazing property deteriorates. Is not preferred. Therefore, the Mg content is set to 0.05 to 0.2%.

Fe: Fe is an Al-Fe intermetallic compound in the base material, or Al-Mn-Fe intermetallic compound or Al-M when Mn or Mn or Si coexists.
In order to improve the strength after brazing by crystallization or precipitation as an n-Fe-Si intermetallic compound, and to disperse these intermetallic compounds finely and uniformly, they become a source of pitting corrosion, In order to improve the corrosion resistance by forming a corrosive form, it is added as necessary. If the content is less than 0.3%, the desired effect cannot be obtained.
%, The corrosion resistance and the extrudability deteriorate, and furthermore, the surface is roughened and the shape is poor at the time of extrusion, which is not preferable. Therefore, the content of Fe is 0.3 to
It was set to 1.5%. A more preferred range of the Fe content is 0.5 to 1.0%.

Mn: Mn is crystallized or precipitated as an intermetallic compound to improve the strength after brazing. When Si coexists, Mn is crystallized or precipitated as an Al-Mn-Si intermetallic compound and brazed. In order to improve the strength afterwards and further increase the potential difference from the fins to make the potential of the tube noble, the corrosion prevention effect of the fins is made more effective, and it has the effect of improving the external corrosion resistance, so it is added as necessary. ,
If the content is less than 0.1%, the desired effect cannot be obtained,
On the other hand, if the content exceeds 1.0%, it becomes a coarse Al-Mn intermetallic compound and is dispersed in the base material, and the extrudability is remarkably reduced in order to increase the deformation resistance at high temperatures, which is not preferable. Therefore, the content of Mn is set to 0.1 to 1.
It was set to 0%. A more preferred range of the Mn content is 0.1.
3 to 0.8%.

Si, Cu: These components have a function of improving the strength after brazing by forming a solid solution in the matrix, and Si further improves the extrudability by reducing the deformation resistance at the extrusion processing temperature. It has an effect, and Cu is added as necessary because it improves the external corrosion resistance by taking a large potential difference from the fins to make the potential of the tube noble and making the corrosion prevention effect of the fins more effective, S
i content is less than 0.1%, Cu content is 0.05%
If the Si content is less than 1.0%, the desired effect cannot be obtained.On the other hand, if the Si content exceeds 1.0%, the melting point is lowered to cause melting of the material at the time of brazing, and further, extrudability and corrosion resistance are reduced, and If the content of Cu exceeds 0.7%, the corrosion rate is increased, and pitting corrosion tends to grow in the depth direction, and the corrosion resistance is undesirably reduced. Therefore, the content of Si was set to 0.1 to 1.0%, and the content of Cu was set to 0.05 to 0.7%. A more preferable range of the Cu content is 0.05 to 0.5%, and a more preferable range of the Si content is 0.3 to 0.7%.

Ti, Zr: These components reduce the deformation resistance at the extrusion temperature, improve the extrudability, and are dispersed in the matrix as fine intermetallic compounds after brazing,
Since it has the effect of improving the strength, it is added as needed. However, if its content is less than 0.01%, the desired effect cannot be obtained, while if it exceeds 0.25%, no further effect can be expected. . Therefore, Ti: 0.01 to 0.25%
(More preferably 0.05 to 0.2%), Zr: 0.0
1 to 0.25 (more preferably 0.05 to 0.2%)%
Determined.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Al having the component composition shown in Tables 1 to 6
The alloy is melted and cast to produce a billet having a diameter of 400 mm. The billet is subjected to homogenization at 500 ° C. for 12 hours, and the homogenized billet is extruded at a temperature of 450 ° C. It has seven holes for refrigerant passages by processing, and the cross-sectional dimensions are 16 mm wide and 2 m high
m, a flat extruded tube 1 of the present invention having a wall thickness of 0.5 mm.
~ 42, comparative extruded tubes 1-4 and conventional extruded tubes. As a result of extrusion under the above conditions, it was found that all of the extrusion tubes 1 to 42 of the present invention have approximately the same extrudability as a conventional extrusion tube made of JIS 3003.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

[Table 6]

Using the extruded tubes 1 to 42 of the present invention, the comparative extruded tubes 1 to 4 and the conventional extruded tubes having the component compositions shown in Tables 1 to 6, tubes for a heat exchanger were prepared. C. for 3 minutes, then cooling rate: 100 ° C./min. , A heat treatment was performed assuming brazing to cool to room temperature, and then a corrosion test under the following conditions was performed.

The corrosion test _{^{1 Cl -: 170ppm, SO 4}} 2-: 50ppm, F
pH including e ³⁺ : 20 ppm and Cu ²⁺ : 1 ppm: 3.
0, and assuming that the aqueous solution is cooling water for a heat exchanger for an automobile, the extruded tubes 1 to 42 of the present invention, the comparative extruded tubes 1 to 4 and the tubes produced by the conventional extruded tubes are subjected to temperature: The aqueous solution at 80 ° C. was flowed at a flow rate of 1 m / sec.
After circulating for 8 hours at room temperature, a temperature cycling operation of maintaining at room temperature for 16 hours was performed for 30 days, and the maximum corrosion depth of pitting corrosion generated inside the tube after 30 days had elapsed was measured. The results are shown in Table 11.

The corrosion test _{^{2 Cl -: 170ppm, SO 4}} 2-: 50ppm, F
An aqueous solution containing e ³⁺ : 20 ppm and Cu ²⁺ : 1 ppm
An aqueous solution adjusted to pH 11 with aOH is prepared, and this aqueous solution is assumed to be cooling water for a heat exchanger for an automobile, and the extruded tubes 1 to 42 of the present invention, the comparative extruded tubes 1 to 4, and the tubes manufactured with the conventionally extruded tubes. And the aqueous solution at a temperature of 80 ° C. at a flow rate of 1 m / sec. After circulating for 8 hours at room temperature and maintaining at room temperature for 16 hours, a temperature cycling operation was performed for 60 days, and the maximum corrosion depth of pitting corrosion generated inside the tube after 60 days had elapsed was measured. The results are shown in Table 11.

[0029]

[Table 7]

[0030]

[Table 8]

[0031]

[Table 9]

[0032]

[Table 10]

[0033]

[Table 11]

The results shown in Tables 7 to 11 indicate that the extruded tubes 1 to 42 of the present invention have excellent corrosion resistance because the maximum corrosion depth from the surface is extremely small as compared with the conventional extruded tubes. I understand. It can also be seen that the comparative extruded tubes 1-4 in which the content of at least one of the constituents is outside the scope of the present invention are inferior in corrosion resistance or other properties.

[0035]

As described above, since the extruded pipe of the present invention is excellent in corrosion resistance, the heat exchanger manufactured using the extruded pipe of the present invention cannot penetrate even if cooling water having a wide range of pH is used. It can be used for a long time without performing, and brings about an industrially superior effect.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Tatemi Toma 85-Hiramatsu, Susono-shi, Shizuoka Pref. F-term in the Technology Development Center of Mitsubishi Aluminum Corporation (reference)

Claims (11)

[Claims] 1. The composition contains Zn: 0.1 to 3%, Ce: 0.01 to 0.5%, and Mg: 0.05 to 0.2% by weight, with the balance being Al and inevitable impurities. An extruded aluminum alloy tube for a heat exchanger having excellent corrosion resistance, comprising an Al alloy having a composition of 2. The composition contains Zn: 0.1 to 3%, Ce: 0.01 to 0.5%, and Mg: 0.05 to 0.2% by weight. An aluminum alloy extruded tube for a heat exchanger having excellent corrosion resistance, comprising an Al alloy having a composition of 1 to 1.0%, with the balance being Al and unavoidable impurities. 3. The composition according to claim 1, further comprising: Zn: 0.1 to 3%, Ce: 0.01 to 0.5%, and Mg: 0.05 to 0.2% by weight. 1-1.0%, Cu: 0.05-0.7%, containing one or two of the following, and the remainder having a composition of Al and unavoidable impurities.
An extruded aluminum alloy tube for a heat exchanger having excellent corrosion resistance, comprising an aluminum alloy. 4. The composition according to claim 1, further comprising: Zn: 0.1 to 3%, Ce: 0.01 to 0.5%, and Mg: 0.05 to 0.2% by weight. 1 to 1.0%, and further contains one or two of Si: 0.1 to 1.0%, Cu: 0.05 to 0.7%, and the rest is Al And composition A consisting of unavoidable impurities
An extruded aluminum alloy tube for a heat exchanger having excellent corrosion resistance, comprising an aluminum alloy. 5. The composition contains, by weight%, Zn: 0.1 to 3%, Ce: 0.01 to 0.5%, and Mg: 0.05 to 0.2%. An aluminum alloy extruded tube for a heat exchanger having excellent corrosion resistance, characterized in that the aluminum alloy contains 3 to 1.5%, and the balance is an Al alloy having a composition of Al and inevitable impurities. 6. The composition contains, by weight%, Zn: 0.1 to 3%, Ce: 0.01 to 0.5%, and Mg: 0.05 to 0.2%. 3 to 1.5%, and further contains Mn: 0.1 to 1.0%, with the balance being an Al alloy having a composition comprising Al and unavoidable impurities, and having excellent corrosion resistance. Extruded aluminum alloy tube for heat exchanger. 7. The composition contains Zn: 0.1 to 3%, Ce: 0.01 to 0.5%, and Mg: 0.05 to 0.2% by weight. 3 to 1.5%, and further contains one or two of Si: 0.1 to 1.0%, Cu: 0.05 to 0.7%, and the rest is Al And composition A consisting of unavoidable impurities
An extruded aluminum alloy tube for a heat exchanger having excellent corrosion resistance, comprising an aluminum alloy. 8. The composition contains, by weight%, 0.1 to 3% of Zn, 0.01 to 0.5% of Ce, and 0.05 to 0.2% of Mg. 3 to 1.5%, further contains Mn: 0.1 to 1.0%, and further contains Si: 0.1 to 1.0%, Cu: 0.05 to 0.7. % Of the composition containing one or two of the above, and the balance consisting of Al and unavoidable impurities.
An extruded aluminum alloy tube for a heat exchanger having excellent corrosion resistance, comprising an aluminum alloy. 9. The Al alloy according to claim 1, further comprising: Ti: 0.01 to 0.25%; Zr: 0.01 to 0.25. %. An aluminum alloy extruded tube for a heat exchanger having excellent corrosion resistance, comprising an Al alloy having a composition containing one or two of the above. 10. The method of claim 1, 2, 3, 4, 5, 6, 7,
10. An extruded aluminum alloy tube for a heat exchanger having excellent corrosion resistance, wherein Zn is sprayed on an outer surface of the extruded aluminum alloy tube according to 8 or 9. 11. The method of claim 1, 2, 3, 4, 5, 6, 7,
10. An extruded aluminum alloy tube for a heat exchanger having excellent corrosion resistance, wherein a powder brazing material is applied to an outer surface of the extruded aluminum alloy tube according to 8 or 9.