JP2001342532A - Aluminum alloy piping material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aluminum alloy piping material for automobile heat exchanger, having processability in processing, corrosion resistance and bending processability, as mono-layer bear material not clad steel. SOLUTION: The aluminum alloy piping material is composed of Si of 0.05 wt.% over and 0.2 wt.% or below, Fe of 0.1 wt.% over and 0.3 wt.% or below, Cu of 0.1 wt.% and 0.3 wt.% or below, Mn of 0.5 wt.% over and 1.0 wt.% or below, Ti of 0.05 wt.% over and 0.30 wt.% or below, Mg of 0.01 wt.% over and 0.3 wt.% or below, and the balance aluminum with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to aluminum alloy pipes for heat exchangers of automobiles, which are particularly excellent in corrosion resistance among aluminum alloys used for heat exchangers for automobiles and various industries.

[0002]

2. Description of the Related Art Conventionally, JIS has been used as a material for pipes and the like of this type of heat exchanger.
1000 series alloy, JIS 3000 series alloy, JIS 600
Zero-based alloys and the like are often used. For example, JIS60
Japanese Patent Publication No. Sho 61-36577 discloses, as a 00 series alloy, 0.35 to 1.5 wt% of Mg and 0.2 to 1.5 wt% of Si.
0.8wt%, 0.1 ~ 0.3wt% Zn,
Further, Sn is 0.02 to 0.1 wt% and Cu is 0.15%.
There is disclosed an aluminum alloy excellent in grain boundary corrosion resistance and pitting corrosion resistance, characterized by containing up to 0.4 wt%. In addition, JIS3
It is common to use an alloy of 000 series as a core material and clad the inner and outer surfaces or one surface of the tube with JIS7072 alloy or the like. As described above, JIS3003 alloy excellent in strength, workability, weldability, and corrosion resistance is used for conventional automotive piping materials, but the corrosion resistance may be insufficient under severe conditions. Therefore, from the viewpoint of corrosion resistance, a core material such as JIS3003 alloy is used instead of a single layer as described above.
Although the inner and outer surfaces or one surface is clad with an S7072 alloy or the like in general, there is a problem that the manufacturing cost is high. Therefore, there has been a need to develop a material having a single-layer structure and a higher corrosion resistance than the JIS 3003 alloy without cladding. Needless to say, the pipe material is required to have good formability and workability in extrusion processing when manufacturing the same and bending processing when assembling the heat exchanger. However, conventional piping materials are not necessarily sufficient in that they have corrosion resistance, moldability, and workability at the same time.

[0003]

The above objects of the present invention have been attained by the following means. That is, the present invention provides (1)
More than 0.05 wt% and 0.2 wt% or less of Si, 0.1
Fe exceeding 0.3% by weight, Fe exceeding 0.3% by weight, and Cu exceeding 0.3% by weight, and exceeding 0.5% by weight.
Mn of 0 wt% or less, more than 0.05 wt% and 0.30 w
(2) 0.05 w of an aluminum alloy piping material containing not more than t% of Ti, more than 0.01 wt% and not more than 0.3 wt% of Mg, and the balance being aluminum and unavoidable impurities.
Si exceeding t% and 0.2 wt% or less, Fe exceeding 0.1 wt% and 0.3 wt% or less, Si exceeding 0.1 wt% and 0.3 wt% or less.
It contains Cu of less than wt%, Mn of more than 0.5 wt% and less than 1.0 wt%, Ti of more than 0.05 wt% and less than 0.30 wt%, and Mg of more than 0.01 wt% and less than 0.3 wt%. And an aluminum alloy piping material containing more than 0.1 wt% and less than 0.5 wt% Zn, with the balance being aluminum and unavoidable impurities; and (3) the aluminum alloy according to (1) or (2). The ingot is hot-extruded to form an extruded raw tube, and in producing an aluminum alloy pipe material by a draw bench method drawing process or a continuous drawing process and an aging precipitation process, the annealing process is performed at a temperature exceeding 330 ° C. to 450 ° C.
C. for 1 to 10 hours at a temperature lower than
An object of the present invention is to provide a method for producing an aluminum alloy piping material, wherein the method is performed at a temperature of at least C / hour.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION The alloy elements of the aluminum alloy piping material of the present invention will be described below.

Si: Si forms an extremely fine intermetallic compound, Mg ₂ Si, by artificial aging together with Mg, and contributes to improvement in strength. The reason why the content of Si is set to be more than 0.05 wt% and 0.2 wt% or less is 0.05 w
If the amount is less than t%, the effect cannot be sufficiently obtained.
When the number exceeds, the work hardening of the raw tube becomes large when performing the drawing process a plurality of times, and it becomes necessary to perform intermediate annealing in the middle of the drawing process, thereby deteriorating the productivity. The content of Si is preferably 0.05 to 0.1 wt%.

Fe: Fe is dissolved in the material, or Al-F
Precipitates an e-type intermetallic compound and contributes to improvement in strength. If the added amount is less than 0.1 wt%, the effect cannot be sufficiently obtained, and if it exceeds 0.3 wt%, the Al-Fe-based intermetallic compound increases and becomes a starting point of cracking during forming. The content of Fe is preferably 0.1 to 0.25 wt%.
It is.

[0007] Cu; Cu has the effect of forming a solid solution in the material to improve the strength of the material, and also prevents the crystal grains from becoming coarse when brazing the piping material at a high temperature. The addition amount is 0.1
If the content is less than 0.3 wt%, the effect cannot be sufficiently obtained.
%, The coarse compound is reduced in crystallization processability and the corrosion resistance is deteriorated. The content of Cu is preferably 0.05 to 0.2 wt%.

Mn: Mn has the effect of forming a solid solution in the material and improving the material strength. If the amount is less than 0.5 wt%, the effect cannot be sufficiently obtained, and if it exceeds 1.0 wt%, the moldability is poor. The content of Mn is preferably 0.6 to 0.8 wt%.

Ti: Ti has the effect of refining the cast structure and, when extruded, forms a component in the thickness direction of the tube, so that the concentrated portion of Ti is noble and the periphery thereof becomes base, and corrosion occurs. The layered structure has an effect of improving the corrosion resistance of the aluminum tube in order to suppress the progress of corrosion in the thickness direction. If the added amount is less than 0.05 wt%, the effect cannot be sufficiently obtained, and if it exceeds 0.30 wt%, a coarse compound of Ti is generated, and the moldability is reduced. The content of Ti is preferably 0.01 to 0.2 w
t%.

Mg: Mg forms a solid solution in the matrix and precipitates fine intermetallic compounds by the effect of increasing strength and the effect of aging precipitation, contributing to the improvement of strength. When the amount added is 0.01
When the content is less than 0.3 wt%, the effect is not obtained. When the content is more than 0.3 wt%, the work hardening of the raw tube becomes large when performing the drawing process a plurality of times, and the intermediate annealing is required during the drawing process, thereby increasing the productivity. This is because the extrudability and the formability (bendability) decrease. The content of Mg is preferably 0.05 to 0.2 wt%.

Zn: Zn is uniformly dissolved in the matrix, has an effect of improving the corrosion resistance by making the potential difference between the grain boundaries and the grains uniform and preventing the grain boundary corrosion. If the addition amount is less than 0.1 wt%, there is no effect, and if it exceeds 0.5 wt%, Zn becomes excessive and the corrosion resistance is impaired. Zn
Is preferably 0.2 to 0.4% by weight.

The aluminum alloy piping material referred to in the present invention is:
It can be manufactured by processing the above-described aluminum alloy by the following steps. Melting casting of aluminum alloy → Homogenization treatment → Hot extrusion → Draw bench method drawing or continuous drawing → Annealing The processing process itself of this piping material is known, but it is characterized by its annealing process and subsequent cooling process There is. here,
As a method of manufacturing an aluminum alloy pipe material, the reason why the annealing treatment is performed at a temperature exceeding 330 ° C., at a temperature of 450 ° C. or less for 1 to 10 hours, and at a cooling rate of 100 ° C./hour or more will be described. If the annealing temperature is lower than 330 ° C., the elongation of the material is reduced, and the bending workability when assembling to a heat exchanger is poor. When the annealing temperature exceeds 450 ° C., among the components added to the pipe material, Al-Mn
Precipitates of the system precipitate at grain boundaries, promote intergranular corrosion, and impair corrosion resistance. The conditions under which the Al-Mn-based precipitates are deposited also depend on the cooling rate.
If the time is less than the time, the frequency of precipitation at the grain boundary increases,
As a result, it promotes intergranular corrosion and impairs corrosion resistance.

[0013]

Next, the present invention will be described in more detail with reference to examples. (1) Aluminum alloy pipe material An aluminum alloy having a composition specified in the present invention shown in Table 1 was melt-cast to form an ingot having a circular cross section.
After homogenization treatment at 0 ° C for 4 hours, it is cut into a length of 1000 mm to form an extruded billet, reheated to 510 to 540 ° C, hot extruded into a 47 mm outer diameter tube, and then continuously drawn. Is performed several times in the cold, and the outer diameter is 8.0 m.
m, a tube material having a wall thickness of 1.0 mm. Then 360
Annealing was performed at 2 ° C. for 2 hours, and after cooling, a test piece was obtained. Using aluminum alloys of the comparative composition and the conventional composition shown in Table 1, pipe materials were obtained in the same manner as the alloys of the present invention. The piping of these test materials was connected to a commercially available aqueous coolant using a circulation test device, and a cycle test of 88 ° C., 8 hours → room temperature, 16 hours was performed for one year. The corrosion state of the material was evaluated by removing surface corrosion products of the test material. Evaluation is to measure the maximum pit depth by the optical microscope by the depth of focus method,
The results are shown in Table 1. Extrusion workability was evaluated comprehensively by judging whether or not an extrusion force and an extrusion speed at the time of extrusion and a sufficient shape were obtained, and evaluated as good and poor. The bending workability was evaluated on the tube after drawing and annealing by a tensile bending (stretch bend) method used in actual bending. Bending conditions: bending radius 30mmΦ, bending angle 6
0 °. A tube without any abnormality after bending was judged as good, and a tube with broken or rough skin was judged as bad.

As can be seen from Table 1, Comparative Examples 1 to 6 could not be manufactured as products because they deviated from the specified range of the present invention. That is, Comparative Examples 1 and 6 cannot be drawn, and Comparative Example 2 cannot be formed (cracks occurred during bending).
Comparative Example 3 was inferior in corrosion resistance and poor in bending workability because Cu deviated from the example of the present invention. In Comparative Examples 4 and 5, although the corrosion resistance was good, the bending workability was poor, and a defect occurred as a product. Comparative Examples 7 to
Sample No. 9 deviated from the scope of the present invention, and thus was inferior in corrosion resistance as compared with the present invention. From Table 1, the present invention example
It can be seen that the corrosion resistance is better than the comparative example and the conventional example.

[0015]

[Table 1]

(2) Manufacturing method of aluminum alloy piping material An aluminum alloy having the composition of the present invention shown in Table 2 and an alloy of a comparative example deviating from the components of the present invention were melt-cast to form an ingot having a circular cross section. Ingot at 610 ° C 4
After the homogenization treatment for a time, the extruded billet is cut to a length of 1000 mm to be extruded, and this is reheated to 510 to 540 ° C., and is hot-extruded into a base tube having an outer diameter of 47 mm. This was performed a plurality of times to obtain a tube material having an outer diameter of 8.0 mm and a wall thickness of 1.0 mm. Thereafter, an artificial aging treatment shown in Table 3 was performed, and the test material was cooled at a cooling rate shown in Table 3 to obtain a test piece. The pipes of these test materials were connected to a commercially available water-based coolant using a circulation tester, and 88 ° C., 8
A cycle test from time to room temperature for 16 hours was performed for one year.
The corrosion state of the material was evaluated by removing surface corrosion products of the test material. For evaluation, the maximum pitting depth was measured by an optical microscope by the depth of focus method, and the results are shown in Table 3. Further, a bending workability test was performed on the piping material in the same manner as described above. Table 3 shows the results.

As shown in Table 3, those having alloy compositions, heat treatments and cooling rates within the range of the present invention exhibited good corrosion resistance.
In contrast, Comparative Example 1 in which the alloy composition was within the scope of the present invention
In Comparative Examples 1 to 3, the heat treatment temperature and the cooling rate of Comparative Example 1 were lower than the specified ranges of the present invention, so that the corrosion resistance was poor and the bending workability was also low. In Comparative Example 2, although the heat treatment temperature was within the range of the present invention, the corrosion rate was inferior because the cooling rate deviated from the present invention. Comparative Example 3 is inferior in corrosion resistance because the heat treatment temperature is out of the range of the present invention, even though the cooling rate is in the range of the present invention. In Comparative Examples 4 to 6, the alloy components are out of the range specified in the present invention. In Comparative Example 4, since the alloy components and the heat treatment temperature deviated from those of the present invention, the corrosion resistance was poor and the bending workability was also poor. In Comparative Example 5, since the alloy components and the cooling rate were outside the ranges specified in the present invention, the corrosion resistance was poor and the bending workability was also poor. In Comparative Example 6, since the alloy components deviated from the specified ranges of the present invention, even if the heat treatment temperature and the cooling rate were within the ranges of the present invention, the corrosion resistance was poor and the bending workability was poor.

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

As described above, according to the present invention, even if a single-layer bare material is used instead of a clad material as an aluminum alloy piping material for a heat exchanger for an automobile, workability during production and excellent corrosion resistance and A heat exchanger piping material having all of the bending properties can be obtained, and industrially remarkable effects can be obtained, such as reduction in cost of the heat exchanger.

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Claims (3)

[Claims] 1. Si exceeding 0.05 wt% and 0.2 wt% or less, Fe exceeding 0.1 wt% and 0.3 wt% or less,
Cu of more than 0.1 wt% and 0.3 wt% or less, 0.5 w
It contains Mn of more than t% and 1.0 wt% or less, Ti of more than 0.05 wt% and 0.30 wt%, Mg of more than 0.01 wt% and 0.3 wt% or less, with the balance being aluminum and inevitable impurities. Aluminum alloy piping material consisting of. 2. The composition according to claim 2, wherein the content of Si is more than 0.05 wt% and less than 0.2 wt%, the content of Fe is more than 0.1 wt% and less than 0.3 wt%,
Cu of more than 0.1 wt% and 0.3 wt% or less, 0.5 w
Mn containing more than t% and not more than 1.0 wt%, Ti containing more than 0.05 wt% and not more than 0.30 wt%, Mg containing more than 0.01 wt% and not more than 0.3 wt% and further containing 0.1 wt%.
Aluminum alloy piping material containing Zn in an amount exceeding 0.5 wt% and the balance being aluminum and unavoidable impurities. 3. An aluminum alloy ingot according to claim 1 or 2 is hot-extruded to form an extruded raw tube, and an aluminum alloy tube is manufactured by a draw bench method drawing process or a continuous drawing process and an aging precipitation process. A method for producing an aluminum alloy pipe material, wherein an annealing treatment is carried out at a temperature of not less than 330 ° C. and not more than 450 ° C. for 1 to 10 hours, and a cooling rate is not less than 100 ° C./hour.