JP3097642B2 - Aluminum alloy for heat exchanger extruded tube with microstructure cross section and method for producing heat exchanger extruded tube with microstructure cross section - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for a heat exchanger extruded tube having a microstructured cross section, which is excellent in corrosion resistance and efficiently and stably forms an extruded material for a heat exchanger extruded tube having a microstructured cross section. It is an object of the present invention to provide a method for manufacturing an aluminum alloy and a heat exchanger extruded tube having a microstructure cross section which can be manufactured at a low temperature.

[0002]

2. Description of the Related Art Extrusion molding is an application of an aluminum alloy material, and is often used as a heat exchanger or a member for a vehicle-mounted device by utilizing the heat conductivity and light weight characteristics of the aluminum material. However, as a tube material in such a heat exchanger for a car air conditioner, conventionally, a pure aluminum material such as A1050 or an Al-Mn-based alloy, or the pure aluminum material contains 0.4 to 0.6% of Cu. The improved modified alloys are mainly used.

On the other hand, the present applicant has disclosed in Japanese Patent Laid-Open Publication No. Sho 6 (1994) that the occurrence of pitting corrosion can be suppressed even under severe corrosive conditions.
A pitting-resistant aluminum alloy such as 0-238438 (Japanese Patent Publication No. 3-44137) has been proposed.

[0004]

However, recently, for the purpose of improving the heat exchange action in the heat exchanger tube or the like, the shape shown in FIG. 1 has a major axis of 20 to 30 mm and a minor axis of 3 to 6 mm. , 0.3-0.7m thick
m, a precise cross-sectional structure such that the diameter of the fine ridges of the through holes is 0.1 to 0.2 mm and the number of through holes is plural, and furthermore, a thinner, smaller, and more corrosion-resistant are required. However, it is difficult to realize such a demand with high productivity in the general technology. JIS1050 (S
i: 0.10, Fe: 0.24, Cu: 0.00, Zn: 0.00, Z
r: 0.00, Ti: 0.006), such as pure aluminum materials conventionally used, are liable to cause orange peel,
In addition, it is inferior in corrosion resistance and further has a definite disadvantage for a heat exchanger extruded tube, for example, due to bending after extrusion molding, micro cracks and deterioration due to coarsening of surface crystal grains become remarkable.

In Japanese Unexamined Patent Publication No. Sho 60-238438 (JP-B-3-44137), extrudability is not always preferable even though corrosion resistance is excellent.
An extruded material having a precise sectional structure as described above cannot be stably obtained with favorable productivity. Further, if the extrusion speed is increased, extrusion defects are generated as such.

[0006]

The present invention has been studied for overcoming the technical problems of the prior art as described above.
Improvements were made on the basis of 238438, and by using an aluminum alloy having a specific component composition, it was possible to obtain appropriate corrosion resistance and successfully realize the above-described micro-section structure for a heat exchanger extruded tube with favorable productivity. It is as follows.

(1) In wt%, Fe: 0.15 to 0.35%, Si: 0.15% or less, Zn: less than 0.03%, Cu: 0.35 to 0.55%, Zr: 0.02 to less than 0.05%, Ti: 0.003 to 0.010%, Fe / Si ≧ 2.5, the balance being Al and unavoidable impurities, heat exchanger extruded tube Aluminum alloy for heat exchanger extruded tubes with a microstructured cross section, characterized by being used for.

(2) In wt%, Fe: 0.15 to 0.35%, Si: 0.15% or less, Zn: less than 0.03%, Cu: 0.35 to 0.55%, Zr: A semi-continuous cast billet containing 0.02 to less than 0.05%, Ti: 0.003 to 0.010%, Fe / Si ≧ 2.5, and the balance being Al and inevitable impurities is 50.
The temperature is raised at a heating rate of ~ 300 ° C / hr and 500 ~ 610 ° C
And then cooled at a cooling rate of 200 to 500 ° C./hr to precipitate finely the intermetallic compound containing Zr and Fe, extrude the billet after preheating, and extrude the billet. A method for producing a heat-extruded extruded tube having a microstructured cross section, wherein the recrystallized grains are controlled to be 30 μm or less.

[0009]

[Action]

Fe: 0.15 to 0.35%. Fe improves the strength of such an aluminum alloy, and obtains appropriate strength by containing 0.15% or more. On the other hand, if it exceeds 0.35%, the corrosion resistance is reduced. . Especially 0.1
When the content is 5 to 0.22%, the occurrence of surface roughness or large peeling and high-quality defects in high-speed extrusion are prevented.

Si: 0.15% or less. Si is combined with Fe and Al
Crystallization of intermetallic compounds such as Fe-Si to reduce the extrudability, so that it is preferably less as an impurity;
Must be the upper limit.

Zn: less than 0.03%. Although Zn enhances the corrosion resistance and appropriately maintains the pitting potential, the inclusion of 0.03% or more impairs the extrudability and makes it difficult to appropriately extrude the micro-section structural material. In the present application in which emphasis is placed on the amount of impurities, the smaller the amount of impurities mixed from the scrap, the better. Therefore, the content needs to be less than 0.03%.

Cu: 0.35 to 0.55%. Cu is 8 in the extruded material
It is added to give a strength of 0 N / mm ² or more. Also Zn
Is an element that contributes to maintaining the pitting potential in the same manner as described above. As described above, in order to ensure a preferable pitting potential under limited conditions with Zn being less than 0.03%, 0.35% or more is contained. It is necessary. However, when this amount of Cu becomes large,
As in the case of Si, an intermetallic compound is generated, and the extrusion pressure is required to be increased. As a result, the extrusion speed is reduced. Therefore, it is necessary to limit the extrusion rate to 0.55% or less.

Zr: 0.02 to less than 0.05%. Zr is intended to obtain effective material strength under high temperature conditions and to obtain fine recrystallized grains as fine as 30 μm or less during extrusion, and to prevent extrudability, especially surface roughness during extrusion at high speed. It has an effect and is a very important element for improving the extrusion speed. For this purpose, 0.02% or more is required. On the other hand, by setting the upper limit to 0.05%, the generation of intermetallic compounds with other elements can be accurately controlled, and the pushing force can be prevented from increasing to obtain a thin and complicated micro-section structure material, such as a defective portion such as a pickup. In particular, when the content is less than 0.05%, a product suitable as a heat exchanger extruded tube can be obtained.

Ti: 0.003 to 0.010%. Ti is important in minimizing the crystal grains of the cast structure and stabilizing the structure, and is preferably contained at 0.003% or more. Since the effect is saturated and an intermetallic compound is generated, it is necessary to set this as an upper limit.

Fe / Si ≧ 2.5. As described above, the upper limit of Si is limited to 0.15% within the range of the undesired impurities.
-Si-based intermetallic compounds are formed, in which β-Al.Fe.Si is particularly difficult to dissolve in the matrix during the billet homogenization treatment. That is, such β-Al-Fe-Si
Is easily generated under the condition that Fe / Si is less than 2.5, which impairs the extrudability of the fine sectional structure.
It is necessary to be 5 or more.

In the present invention, a billet obtained by semi-continuous casting is generally used in a temperature range of 500 to 610 ° C. to a temperature of 0.5 to 500 ° C. in order to effectively use a metal body having the above-mentioned composition. In heating and homogenizing for about 8 hours, the temperature was raised to the target temperature at a heating rate of 50 to 300 ° C./hr, and Zr and Fe-based intermetallic compounds were finely precipitated to remove Cu, Si, etc. After maintaining in a temperature range of 500 to 610 ° C. to form a solid solution, cooling is performed at 200 to 500 ° C./hr in order to suppress precipitation of intermetallic compounds as much as possible. In other words, it is possible to obtain sufficient billet quality under such conditions, but it is further necessary to maintain the billet at the aforementioned temperature of 500 to 610 ° C. for 0.5 hour at 400 to 450 ° C. during heating, and then to return to the predetermined temperature rapidly. By heating, the intermetallic compound containing Zr and Fe and other transition elements is further finely precipitated, and even if the extruded material is extruded by the billet, the recrystallized grains are refined and the extrusion speed is increased. Improve surface condition and quality.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention as described above will be described. In terms of wt%, Si: 0.07%, F
e: 0.22%, Cu: 0.40%, Zn: 0.02%, Zr: 0.0
4%, Ti: 0.008%, the balance being Al and unavoidable impurities, and a semi-continuous casting of an aluminum alloy melt having a composition of 3.1 Fe / Si, 178 mmφ × 500 mmL
Of the present invention was obtained.

As a comparative material, the corrosion resistance and the extrudability should be sufficiently considered in the composition range shown in JP-A-60-238438.
Si: 0.07%, Fe: 0.22%, Cu: 0.40%, Ti: 0.0
08%, both of which are within the range of the present invention, with Zn being 0.07% and Zr: 0.15%, respectively, higher contents than the material of the present invention, and the balance being Al and unavoidable impurities. I prepared things. The comparative material was manufactured with the same dimensions as the billet according to the present invention.

However, the billets of the present invention material and the comparative material as described above were heated at a heating rate of 200 ° C./hr,
After the homogenization treatment at 80 ° C. × 5 hours, the mixture was cooled to room temperature at a cooling rate of 300 ° C./hr. Thereafter, flat tubes for a heat exchanger as shown in FIG. 1 of the accompanying drawings were extruded respectively. That is, the major axis is 22 mm, the minor axis is 5 mm, and the wall thickness is 0.6.
A flat tube 1 having a thickness of 0.6 mm, and five partition walls 2 each having a thickness of 0.6 mm are arranged in the middle of the flat tube 1 at intervals of 2.7 mm to divide the inside of the flat tube 1 into six. Small ridges 4 on the inner surface of the through hole 3
Is provided to increase the surface area.

FIG. 2 is an enlarged view showing a specific structure of the fine ridges 4. The radius between the relatively large grooves 41 having a radius of 0.15 mm is 0.05 mm. The protrusions 42 having a small target diameter are arranged at a pitch of 0.5 mm.

Using the above-described billets of the present invention material and the comparative material, the flat tube having a small cross section as shown in FIGS. 1 and 2 was extruded at a billet preheating temperature of 400.degree. The extrusion pressure of each test material when extruded at min was measured. The results are shown in Table 1 below. That is, of course, Zr,
The material of the present invention having a small alloying element such as Zn has a low extrusion pressure.
Then, the limit extrusion speed which affects productivity was measured.

[0022]

[Table 1]

That is, the test material was extruded at a billet preheating temperature of 400 ° C., and the maximum extrusion speed (extrusion limit speed) at which no extrusion defects occurred was measured. The results are shown in Table 1. From these results, the material of the present invention has a high extrusion limit speed,
It turns out that it is excellent in productivity. That is, when the alloy material of the present invention, which satisfies the mechanical properties as a heat exchange tube, is compared with the comparative material, the extrusion speed is found to be improved by 57%.

Extrusion defects that occur when the extrusion speed reaches the above-described extrusion speed are defects as shown in Table 1, and a product having this defect cannot be used as a heat exchange tube.
Regarding the corrosion resistance by the Cass test, the material of the present invention and the comparative material have a pit depth of 0.07 mm or 0.06 mm in 5 days. Therefore, the extrusion speed of the product of the present invention is substantially maintained while maintaining the corrosion resistance. It can be seen that it has been greatly improved.

[0025]

According to the present invention as described above, a heat exchange tube having a microstructure cross section and excellent in mechanical properties and corrosion resistance can be formed with higher productivity than in the prior art. This is an invention which is industrially highly effective because it can stably produce and provide a product which is excellent in terms of use and which has excellent use characteristics for a heat exchanger extrusion tube.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one example of a microstructure cross-section extruded material to be obtained by the present invention.

FIG. 2 is an enlarged sectional view of a part thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat tube body 2 Partition wall 3 Through-hole 4 Micro ridge 41 Groove part with a comparatively large diameter 42 Ribbon with a comparatively small diameter

────────────────────────────────────────────────── ─── front page continued (51) Int.Cl. ⁷ identifications FI C22F 1/00 612 C22F 1/00 612 626 626 640 640A 651 651A 682 682 683 683 691 691A 691B 691C 692 692A F28F 21/08 F28F 21 / 08 A (56) References JP-A-60-238438 (JP, A) JP-A-57-70254 (JP, A) JP-A-58-141358 (JP, A) JP-A-4-353 (JP, A) A) JP-A-5-169133 (JP, A) JP-A-5-9672 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 21/00-21/18 C22F 1 / 04-1/057

Claims (2)

(57) [Claims] (1) In wt%, Fe: 0.15 to 0.35%, Si: 0.15% or less, Zn: less than 0.03%, Cu: 0.35 to 0.55%, Zr: 0 0.02 to less than 0.05%, Ti: 0.003 to 0.010%, Fe / Si ≧ 2.5, the balance being Al and unavoidable impurities, for heat exchanger extruded tubes An aluminum alloy for a heat exchanger extruded tube having a microstructured cross section. 2. In wt%, Fe: 0.15 to 0.35%, Si: 0.15% or less, Zn: less than 0.03%, Cu: 0.35 to 0.55%, Zr: 0 0.02 to less than 0.05%, Ti: 0.003 to 0.010%, Fe / Si ≧ 2.5, the balance being Al and 50 parts of an aluminum semi-continuous cast billet which is an unavoidable impurity.
The temperature is raised at a heating rate of ~ 300 ° C / hr and 500 ~ 610 ° C
And then cooled at a cooling rate of 200 to 500 ° C./hr to precipitate finely the intermetallic compound containing Zr and Fe, extrude the billet after preheating, and extrude the billet. A method for producing a heat-extruded extruded tube having a microstructured cross section, wherein the recrystallized grains are controlled to be 30 μm or less.