JPH06207257A - Complex tube for aluminum heat exchnager and manufacture thereof - Google Patents

Abstract

PURPOSE:To secure the reliability for long term and to reduce the cost by lowering a joining temp. in a brazing process of an aluminum heat exchanger using a tube formed by cold-or hot-extrusion. CONSTITUTION:On at least a part of the surface of Al or Al alloy tube formed by the cold-or hot-extrusion, Zn base alloy containing 10-70wt% Sn and 2-10wt% At and the balance Zn is coated as the solder. The coating is executed by using the Zn base alloy with flux, ultrasonic wave or both of them at the m.p. of this Zn base alloy +30 deg.C to 410 deg.C in the hot-dip coating method.

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, aluminum heat exchangers have a high joining temperature of about 600 ° C. because they are brazed in the form of a brazing sheet using an Al—Si alloy brazing material. 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 studies in view of this, the present invention can perform bonding with an aluminum-based material at a lower temperature (specifically, 410 ° C. or lower), which leads to cost reduction and long-term reliability. This is the development of an aluminum heat exchanger composite tube that can be secured and its manufacturing method.

That is, the composite tube of the present invention has Sn: more than 10 wt% and 70 wt% or less and Al: 2 to 10 wt% as solder on at least a part of the surface of an Al or Al alloy tube formed by cold or hot extrusion. It is characterized in that it is coated with a Zn-based alloy containing 10 wt% and the balance Zn.

According to the method of manufacturing the composite tube of the present invention, Sn: 10 wt% as a solder is formed on at least a part of the surface of an Al or Al alloy tube formed by cold or hot extrusion.
%, 70 wt% or less, Al: 2 to 10 wt%, and a Zn-based alloy consisting of the balance Zn is coated at a temperature of the melting point of the Zn-based alloy + 30 ° C. or more and 410 ° C. or less, The Zn-based alloy is coated by flux, ultrasonic waves, or hot dip plating using these 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 also 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,
Sn: over 10 wt%, 70 wt% or less, Al: 2-10
A Zn-based alloy containing wt% and the balance Zn is used.

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 Sn to the Zn-based alloy lowers the melting point of the Zn-based alloy and enhances the fluidity of the alloy to improve spreadability (wettability with Al), hot dipability and bondability. Is. Then, the addition amount of Sn is 10 wt%
The reason for limiting the amount to 70 wt% or less is that these effects are insufficient at 10 wt% or less, and a sound joining portion with an aluminum-based material cannot be obtained at a joining temperature of 410 ° C. or less,
If it exceeds 70 wt%, the melting point will be further lowered, but no further improvement in fluidity will be recognized, and the addition of more than necessary Sn will increase the cost of the bonding alloy (solder).

The addition of Al is for preventing the oxidation of the molten Zn and the molten Sn, lowering the melting point, facilitating the hot dipping and joining work, and improving the wettability with Al. However, the reason why the addition amount of Al is limited to 2 to 10 wt% is that these effects are insufficient if the amount is less than 2 wt%.
This is because if it exceeds wt%, the melting point rises, the spreadability of the Zn-based alloy deteriorates, and the workability of joining at low temperatures of 410 ° C. or lower deteriorates.

Further, the temperature for coating the Zn-based alloy on the Al material is the melting point (liquidus point) of the Zn-based alloy + 30 ° C. or higher, 4
The reason why the temperature is set to 10 ° C. or lower is as follows. Zn coating temperature
This is because if the melting point of the base alloy is less than + 30 ° C., the spreadability of the Zn base alloy cannot be ensured and a sound coating cannot be obtained. Further, the melting point of the Zn-based alloy in the present invention is 410 ° C. or lower, and heating above 410 ° C. is excessive heating, which is also disadvantageous in terms of energy cost.

Further, the temperature when the tube of the present invention is combined with other heat exchanger parts and they are joined by the above Zn base alloy may be approximately the same as the above coating treatment temperature.

[0014]

EXAMPLES Examples of the present invention will be described below. 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 is provided between the tubes.
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, a brazing sheet (JIS 3003 alloy for the core material and JIS 4045 (Al-10 wt% Si) alloy brazing material for the skin material) was used for the fins to assemble a similar serpentine-type capacitor by the conventional method, and heat it to 600 ° C to join it. did.

For these capacitors, the joint state between the fin and the tube was visually inspected, and the results are shown in Table 1. Also, after cutting out a part of the joint from the capacitor and embedding and polishing in resin, the fillet shape in the cross section of the joint is observed with a microscope to check the wetting condition of the solder alloy with Al, and the results are also shown in Table 1. did.

[0017]

[Table 1] * 1 A: Good joining B: Partial joining C: Not joining * 2 A: Continuously good fillet formation B: Partial good fillet formation C: Incomplete formation of fillet (sufficient joining) No swelling of the alloy for use is observed) D: No fillet is formed

According to the invention examples No. 1 to 7, Al--Si
Compared with the conventional brazing using a system alloy brazing material, at a temperature lower by about 200 to 250 ° C. (410 ° C. or less), a good joint with a good fillet shape can be obtained.
On the other hand, in Comparative Examples Nos. 8 to 10 in which the composition of the Zn-based alloy is out of the range of the present invention, joining is impossible or only partially joined at a temperature of 410 ° C or lower.

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.

[0020]

As described above, according to the present invention, in the joining of the aluminum heat exchanger, the joining temperature can be lowered (to 410 ° C. or less) to reduce the running cost, and a good joining state can be obtained. Can be secured. Also Zn
Since the base alloy is electrochemically baser than the tube material and has a sacrificial effect 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 Multi-hole tube 2 Fin material

Claims (2)

[Claims] 1. Al formed by cold or hot extrusion
Alternatively, as a solder, Sn: more than 10 wt% and more than 70 wt%, and Al:
A composite tube for a heat exchanger made of aluminum, characterized by containing a Zn-based alloy containing 2 to 10 wt% and the balance being Zn. 2. Al formed by cold or hot extrusion
Alternatively, as a solder, Sn: more than 10 wt% and more than 70 wt%, and Al:
A method for producing a composite tube for an aluminum heat exchanger, which comprises coating a Zn-based alloy containing 2 to 10 wt% and the balance Zn at a temperature of the melting point of the Zn-based alloy + 30 ° C to 410 ° C. .