JPH05253691A - Composite tube for al heat exchanger and production thereof - Google Patents

Abstract

PURPOSE:To secure a long term reliability and reduce the cost by lowering a joining temp. for brazing of an Al heat exchanger which uses a cold or hot extruded tube. CONSTITUTION:A cold or hot extruded Al or Al alloy tube has, at least on a part of its surface, a coating of a Zn base alloy solder having a composition consisting of, by weight, 10.5-5.0% Al, 1.5-10.0% Sn, or either one or two kinds of <=5% Cu, <=0.5% Ti and the balance Zn, the coating is applied with the Zn base alloy by flux and ultra sonic means or a hot dip plating jointly with the foregoing at 440-510 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum heat exchanger composite tube and a method for producing the same, and particularly to a heat exchanger using an Al or Al alloy tube formed by cold or hot extrusion. By lowering the joining temperature in the attaching process, ensuring long-term reliability, and reducing the cost.

[0002]

2. Description of the Related Art Since an aluminum heat exchanger has a complicated structure, a brazing sheet clad with an Al--Si alloy brazing material is generally used as a part of a component of an assembly, and the melting point of the core material is The temperature is increased to about 600 ° C., which is directly below, brazing is performed in a furnace using Nocolock brazing method or vacuum brazing method, and the components are joined together. For example, in a heat exchanger using an electric resistance welded tube, the tube material is a brazing sheet in order to prevent perforation corrosion of the tube. On the other hand, in a heat exchanger using a tube formed by cold or hot extrusion, since a brazing sheet cannot be used for the tube, the fin material is used as a brazing sheet and Zn is applied to the tube surface for the purpose of preventing perforation corrosion of the tube. Brazing after spraying.

[0003]

Generally, an aluminum heat exchanger is brazed with an Al-Si alloy brazing material in the form of a brazing sheet, so that the joining temperature is as high as about 600 ° C. Strict temperature control is essential because it is close to the melting point of materials other than brazing filler metal. In addition, since it is necessary to keep it in a vacuum or an inert gas atmosphere, there is a problem that equipment cost and running cost are high. Further, the melting point of the brazing filler metal used for the skin material also limits the material used for the core material. Further, since the clad material is used, there is a problem that the waste cannot be reused. Further, in a heat exchanger using a tube formed by cold or hot extrusion, treatment such as Zn thermal spraying is necessary in order to prevent perforation corrosion of the tube.

[0004]

As a result of various investigations in view of the above, the present invention has made it possible to join aluminum-based materials at a lower temperature, reduce costs, and ensure reliability for a long time, and a composite tube for an aluminum heat exchanger. This is a developed manufacturing method.

That is, the composite tube of the present invention comprises Al of 0.5 to 5.0 wt% as solder on at least a part of the surface of an Al or Al alloy tube formed by cold or hot extrusion.
%, Sn 1.5-10.0 wt%, or further Cu
It is characterized by containing one or two kinds of 5 wt% or less and Ti 0.5 wt% or less, and coating a Zn-based alloy composed of the balance Zn.

According to the method for producing the composite tube of the present invention, at least a part of the surface of the Al or Al alloy tube formed by cold or hot extrusion is used as solder with Al 0.5-
A Zn-based alloy containing 5.0 wt% and Sn 1.5 to 10.0 wt%, or one or two of Cu 5 wt% or less and Ti 0.5 wt% or less, and the balance Zn is 440.
The coating is performed at a temperature of up to 510 ° C., and the Zn-based alloy is coated by flux, ultrasonic waves, or hot dipping in which these are used in combination.

[0007]

As described above, the present invention uses a composite tube in which at least a part of the surface of an Al or Al alloy tube formed by cold or hot extrusion is coated with a Zn-based alloy as a solder, so that Does not need a brazing sheet as a part that needs to be joined mechanically,
Bonding at lower temperatures is possible. Therefore, for example, it is possible to use a high-strength material having a relatively low liquidus point such as JIS 5000 series (Al-Mg series) alloy for the fin material, and it is possible to reduce the thickness of the joined parts. Since the Zn-based alloy coated on the tube surface as solder acts as a sacrificial anode layer on the tube material, it is possible to prevent pitting corrosion of the tube and ensure long-term reliability.

As a Zn-based alloy coated as solder,
Zn-based alloy containing 0.5 to 5.0 wt% of Al and 1.5 to 10.0 wt% of Sn, or 1 or 2 of 5 wt% or less of Cu and 0.5 wt% or less of Ti, and the balance Zn. To use.

As a method of coating the surface of the tube with a Zn-based alloy, hot dip plating using flux, hot dipping using ultrasonic waves, and the like are economically advantageous. Alternatively, the tube to be treated may be first subjected to zincate treatment and then hot-dipped.

The addition of Al in a Zn-based alloy is equivalent to the melting Z
This is for preventing the oxidation of n, lowering the melting point to facilitate the hot dipping and joining work, and improving the strength and the joining strength by refining the crystal grains. However, the reason why the addition amount of Al is limited to 0.5 to 5.0 wt% is that these effects are insufficient if it is less than 0.5 wt%, and if it exceeds 5.0 wt%, the oxidation and strength of molten Zn are prevented. This is because the melting point is increased but the spreadability of the Zn-based alloy is deteriorated and the bonding workability is deteriorated, although the improvement is good.

This is because the addition of Sn lowers the melting point of the Zn-based alloy, and improves the spreadability, hot-dipability and bondability of the alloy. Therefore, the addition amount of Sn is 1.5 to
The reason why the content is limited to 10.0 wt% is that if less than 1.5 wt%, these effects are insufficient, and if it exceeds 10.0 wt%, the properties are excellent but the strength is weakened.

The addition of Cu is for improving the wettability between the Zn-based alloy and the Al material and the strength. However, the reason why the amount of Cu added is limited to 5 wt% or less is that if the amount of Cu added exceeds 5 wt%, the melting point becomes too high, and the workability of joining deteriorates.

[0013] The addition of Ti is to prevent the oxidation of the Zn-based alloy, Al
This is to improve the wettability with the material and prevent the change in color. However, the reason why the amount of Ti added is limited to 0.5 wt% or less is that the melting point is too high if the amount added exceeds 0.5 wt%.
This is because the workability of joining is deteriorated.

The temperature at which the Zn base alloy is coated on the Al material is set to 440 to 510 ° C. for the following reason.
This is because the melting point of the Zn-based alloy in the present invention is approximately 410 ° C. or less, but if it is less than 440 ° C., the spreadability of the Zn-based alloy cannot be ensured and it is difficult to perform sound coating. Again 51
This is because heating above 0 ° C. is more than necessary and is disadvantageous in terms of energy cost. The melting point (liquidus point) of the Zn-based alloy is preferably in the range of 360 to 430 ° C.

The temperature at which the tube of the present invention is used in combination with other heat exchanger parts and these are joined by the above Zn-based alloy may be approximately the same as the above coating treatment temperature.

[0016]

EXAMPLES The present invention will be described below with reference to examples. JI
After forming a multi-hole tube by extrusion using an S1100 (Al-0.12 wt% Cu) alloy, a Zn-based alloy having the composition shown in Table 1 was formed on the outside of the tube by hot dipping with ultrasonic waves. A composite tube for a heat exchanger made of aluminum was prepared by coating the plate to a thickness of -40 μm. The coating temperature at this time was the same as the bonding temperature in Table 1.

JIS 3003 (Al-0.15) in which this tube is bent in a meandering shape and corrugated between the tubes is formed.
A fin material made of a wt% Cu-1.1 wt% Mn) alloy was sandwiched and bonded at the bonding temperature shown in Table 1 to assemble the serpentine type capacitor shown in FIG. In Figure 1, (1)
Indicates a multi-hole tube, and (2) indicates a fin material. For comparison, the fins have a brazing sheet (the skin material is JIS 4045).
A similar serpentine type capacitor was assembled by a conventional method using (Al-10 wt% Si) brazing alloy),
The bonding temperature at which a sound bonding portion was obtained was compared with the above-mentioned inventive examples.

[0018]

[Table 1]

According to the example of the present invention, compared with the conventional brazing using the Al—Si alloy brazing material, about 100 to 1 is used.
Bonding can be performed at a temperature as low as 50 ° C. As a result of examining the soundness of the joint portion between the tube and the fin after forming the capacitor, it was confirmed that a joint having no defect such as a joint defect was obtained.

Although the present invention has been described with reference to an aluminum capacitor as an example, the present invention is not limited to this, and Al using a tube formed by cold or hot extrusion is used.
It goes without saying that it can be applied to Al alloy heat exchangers in general.

[0021]

As described above, according to the present invention, the joining temperature can be lowered in the joining of the aluminum heat exchanger, and the Zn-based alloy is electrochemically base compared with the tube material. Since it has a sacrificial action on the tube material, it is possible to ensure long-term reliability against pitting corrosion of the tube material, which is an industrially significant effect.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a serpentine type capacitor.

[Explanation of symbols]

 1 tube 2 fin material

Claims (3)

[Claims] 1. Al formed by cold or hot extrusion
Alternatively, as a solder, Al 0.5 to 5.0 wt% and Sn 1.5 to 10.
0 wt% or further Cu 5 wt% or less, Ti 0.5
A composite tube for an aluminum heat exchanger, characterized in that it contains one or two of wt% or less and is coated with a Zn-based alloy consisting of the balance Zn. 2. Al formed by cold or hot extrusion
Alternatively, as a solder, Al 0.5 to 5.0 wt% and Sn 1.5 to 10.
0 wt% or further Cu 5 wt% or less, Ti 0.5
A method for producing a composite tube for an aluminum heat exchanger, which comprises coating a Zn-based alloy containing one or two of wt% or less and the balance Zn at a temperature of 440 to 510 ° C. 3. The method for producing a composite tube for an aluminum heat exchanger according to claim 2, wherein the Zn-based alloy is coated by flux, ultrasonic waves or hot dip plating in which these are used in combination.