JP2007070699A - Extruded aluminum alloy tube for heat exchanger, heat exchanger and method for manufacturing the tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a lightweight extruded aluminum alloy tube for heat exchanger having superior proof stress at ordinary and high temperatures and also excellent in extrusion property. <P>SOLUTION: The extruded aluminum alloy tube for heat exchanger has a composition consisting of, by mass, 0.31 to 0.7% Si, 0.3 to 0.6% Fe, 0.01 to 0.4% Mn and the balance Al with inevitable impurities and further containing, if necessary, one or more kinds among 0.01 to 0.3% Ti, 0.05 to 0.3% Zr and 0.05 to 0.3% Cr. Satisfactory strength (proof stress) can be secured without deteriorating extrusion property, and weight reduction in the heat exchanger is made possible. By adopting the heat exchanger, the heat exchanger can be used as an air conditioner using e.g. gaseous CO<SP>2</SP>as a refrigerant without any problem. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat exchanger used for a car air conditioner and the like, and an aluminum alloy extruded tube for a heat exchanger which is a constituent member of the heat exchanger.

A heat exchanger used in a car air conditioner or the like is often made of an aluminum alloy that is lightweight and has good corrosion resistance, and an aluminum alloy extruded tube is usually used as a tube serving as a passage for the heat medium (for example, Patent Document 1).
Recently, from the viewpoint of the global environment, the refrigerant of a heat exchanger for a car air conditioner is being replaced from CFC gas to CO ₂ gas. When this CO ₂ gas is used, not only the gas pressure in the heat exchanger is remarkably increased, but also the temperature of the heat exchanger (condenser) during use increases, so that The material needs to have sufficient strength (proof strength) even at high temperatures.
JP 2000-8130 A

  Therefore, it is necessary to use a high-strength material as the material for the heat exchanger. However, a relatively strong alloy such as the conventional JISA3003 alloy is extrudable when manufacturing a heat exchanger tube having a relatively small cross-sectional area. Therefore, there is a problem that not only a predetermined extruded material shape cannot be formed but also productivity is lowered. For this reason, in order to ensure the strength with the conventional material, it is necessary to select a material with good extrudability and then to increase the thickness of the extruded tube, so that the weight of the entire heat exchanger is remarkably increased. There's a problem.

  The present invention has been made against the background of the above circumstances, and has excellent extrudability and high strength, and thus heat that can increase the strength of the heat exchanger without increasing the weight of the heat exchanger. An object of the present invention is to provide an aluminum alloy extruded tube for an exchanger and a heat exchanger including the tube.

That is, among the aluminum alloy extruded tubes for heat exchangers of the present invention, the invention according to claim 1 is mass%,
Si: 0.31 to 0.7%,
Fe: 0.3 to 0.6%,
Mn: 0.01 to 0.4% is contained, and the balance consists of Al and inevitable impurities.

  The invention of the aluminum alloy extruded tube for a heat exchanger according to claim 2 is the invention according to claim 1, further comprising, in mass%, Ti: 0.01 to 0.3%, Zr: 0.05 to 0.3%. , Cr: One or more of 0.05 to 0.3% are contained.

The invention of the aluminum alloy extruded tube for a heat exchanger according to claim 3 is the invention according to claim 1 or 2, wherein the extruded material is provided with a Zn or Zn-containing layer on an outer surface thereof. The amount of Zn is ² to 20 g / m ² .

  The heat exchanger according to claim 4 is manufactured using the aluminum alloy extruded tube for heat exchanger according to any one of claims 1 to 3.

  The manufacturing method of the aluminum alloy extruded tube for heat exchangers of Claim 5 is a manufacturing method of the aluminum alloy extruded tube for heat exchangers of any one of Claims 1-3, Comprising: It obtained by extrusion Prior to brazing, the aluminum alloy extruded tube for heat exchanger is subjected to strain processing with a strain rate of 2 to 15%.

An appropriate amount of non-recrystallized structure formed by the strain processing remains even after brazing, and the proof stress can be further improved.
However, if the strain rate is less than 2% or more than 15%, a sufficient unrecrystallized structure does not remain after brazing and the above effect cannot be obtained sufficiently, so 2-15% is specified. The strain processing can be performed by rolling, tension, bending, or the like.

The action of each element and the reason for limitation will be described below.
Si: 0.31 to 0.7%
Si improves the strength by a solid solution effect. However, the effect cannot be expected below the specified value. On the other hand, if the content exceeds the specified value, remarkable erosion occurs at the time of brazing and the brazing property is lowered. Therefore, the Si content is set to 0.31% to 0.7%. For the same reason, it is desirable to set the lower limit to 0.4% and the upper limit to 0.6%.

Fe: 0.3-0.6%
Fe refines crystal grains and improves strength. However, if it is less than 0.3%, the effect cannot be expected. On the other hand, if it exceeds 0.6, the extrudability is lowered, so the Fe content is limited to 0.3 to 0.6%. For the same reason, it is desirable to set the lower limit to 0.4% and the upper limit to 0.5%.

Mn: 0.01 to 0.4%
Mn forms an intermetallic compound and improves the strength. However, if it is less than 0.01%, an effect cannot be expected. On the other hand, if it exceeds 0.4%, the extrudability is lowered, so the Mn content is limited to 0.01 to 0.4%. For the same reason, it is desirable to set the lower limit to 0.25% and the upper limit to 0.35%.

Ti: 0.01 to 0.3%
Zr: 0.05-0.3%
Cr: 0.05-0.3%
Ti, Zr, and Cr form a fine intermetallic compound and improve the strength, so that one or more of them are contained as desired. However, if Ti is less than 0.01% and Zr and Cr are less than 0.05%, the effect cannot be expected. On the other hand, if each exceeds 0.35, the extrudability is reduced, so Ti: 0.01 to 0.3%, Zr: 0.05 to 0.3%, Cr: 0.05 to 0.3% limit. For the same reason, Ti has a lower limit of 0.15% and an upper limit of 0.25%, Zr has a lower limit of 0.15%, an upper limit of 0.25%, and Cr has a lower limit of 0.10% and an upper limit of 0.15%. It is desirable that the content be 0.28%.

As described above, according to the aluminum alloy extruded tube for a heat exchanger of the present invention, in mass%, Si: 0.31 to 0.7%, Fe: 0.3 to 0.6%, Mn: 0.00. 1 to 0.4%, and optionally one of Ti: 0.01 to 0.3%, Zr: 0.05 to 0.3%, Cr: 0.05 to 0.3% Since the remainder is made of Al and inevitable impurities, a sufficient strength can be ensured without deteriorating the extrudability, and an extruded tube that can reduce the weight of the heat exchanger can be obtained.
Since the heat exchanger of the present invention is manufactured using the above-described aluminum alloy extruded tube for heat exchanger, a heat exchanger having excellent strength (proof strength) even at high temperatures can be obtained without causing an increase in weight. For example, there is an effect that it can be used without any trouble as an air conditioner using CO ₂ gas as a refrigerant.

  In the aluminum alloy extruded tube for a heat exchanger of the present invention, an alloy melted by a conventional method in the composition specified above can be used. When an extruded tube is obtained using this alloy, desirably, the extrusion is performed by applying a homogenization treatment at 450 to 620 ° C. for 3 to 24 hours. Extrusion can be formed into an appropriate shape except for the tube shape. In addition, the conditions and extrusion method at the time of extrusion are not specifically limited as this invention.

As shown in FIG. 1, the extruded tube 1 has holes 2 through which a coolant passes in the longitudinal direction, and a Zn or Zn-containing sprayed layer 3 is provided on the surface as desired. The formation of Zn or a Zn-containing sprayed layer provides a sacrificial anodic action and improves the corrosion resistance of the extruded tube. A Zn-containing flux is exemplified as the Zn-containing layer. Examples of the Zn-containing flux include ZnF ₂ , ZnCl ₂ , KZnF _{3 and the} like. In the Zn or Zn-containing sprayed layer, the Zn content in the sprayed layer is desirably ² to 20 g / m ² . This is because if the Zn content is less than 2 g / m ² , the above effect in the sprayed layer cannot be sufficiently obtained, while if it exceeds 20 g / m ² , the sacrificial anodic action becomes excessive, and on the contrary, the corrosion resistance of the extruded tube. This is because of a decrease.

  The extruded tube 1 is provided with the sprayed layer 3 if desired, and is combined with fins 4 as other members. By joining the members of this combined body to each other by brazing or the like, a heat exchanger that is lightweight and excellent in strength (proof strength) at normal temperature and high temperature can be obtained.

An embodiment of the present invention will be described below.
An aluminum alloy having the composition of the test material shown in Table 1 was melted by a conventional method to obtain a billet having a diameter of 200 mm. The billet was homogenized by holding at 550 ° C. for 8 hours. This billet was extruded at 480 ° C. and an extrusion speed of 40 m / min to obtain a flat extruded tube shown in FIG. During the extrusion, the extrudability of each sample material was evaluated. The extrudability was evaluated by measuring the extruding pressure when extruding at 40 m / min, and the occurrence of the extruding pressure and pickup (a defect in which part of the surface of the extruded material was stripped off in the form of dots).
In addition, in the process of cooling the extruded tube after hot extrusion, before the temperature of the extruded tube decreases to 400 ° C., a Zn sprayed layer made of pure industrial Zn is formed on the outer surface of the extruded tube by a thermal spraying method. Formed. In the Zn sprayed layer, the amount of Zn was set to about 10 g / m ² at the outer flat portion.

The tube height was adjusted at a reduction rate of 2 to 15% by a resizing step before brazing. Inventive material No. Resizing was not performed for No. 10 (the same component as invention material No. 7). The extruded tube was simulated for brazing heat treatment, heated at 600 ° C. for 3 minutes, and then the proof stress was measured.
The yield strength was measured by a tensile test at normal temperature and 165 ° C. These test results are shown in Table 2.

  As shown in Table 2 above, it was revealed that the test material of the present invention was excellent in both extrudability and strength (yield strength). On the other hand, comparative material No. which is out of the scope of the present invention. Nos. 2, 4, and 6 have good extrudability but insufficient strength. In 1, 3, and 7, although the strength is high, the extrudability is poor.

It is a partial perspective view which shows the assembly | attachment state of the extrusion tube and fin in one Embodiment of this invention.

Explanation of symbols

1 Aluminum alloy extruded tube for heat exchanger 2 Hole 3 Sprayed layer 4 Fin

Claims (5)

% By mass
Si: 0.31 to 0.7%,
Fe: 0.3 to 0.6%,
An aluminum alloy extruded tube for a heat exchanger, which contains Mn: 0.01 to 0.4%, and the balance is made of Al and inevitable impurities.     Furthermore, it is characterized by containing at least one of Ti: 0.01-0.3%, Zr: 0.05-0.3%, Cr: 0.05-0.3% by mass%. The aluminum alloy extruded tube for heat exchangers according to claim 1. The extrudate is provided with a Zn or Zn-containing layer on the outer surface thereof, and the Zn content of the layer is ² to 20 g / m ^2. Aluminum alloy extruded tube.   It manufactured using the aluminum alloy extruded tube for heat exchangers of any one of Claims 1-3, The heat exchanger characterized by the above-mentioned.   It is a manufacturing method of the aluminum alloy extrusion tube for heat exchangers of any one of Claims 1-3, Comprising: A distortion rate is given to the aluminum alloy extrusion tube for heat exchangers obtained by extrusion before brazing. A method for producing an aluminum alloy extruded tube for a heat exchanger, wherein 2 to 15% strain processing is performed.

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