JPH05322482A - Manufacture of al heat exchanger - Google Patents

Abstract

PURPOSE:To enhance corrosion resistance of an outer surface side by using Al, Al alloy material which is more base than the potential of an outer surface of a tube as a fin material, using a brazing sheet of a layer clad having a core material containing Cu as a tube material, assembling a heat exchanger and then brazing it. CONSTITUTION:A heat exchanger for a radiator, etc., for a vehicle has a tube 2 and a heat dissipating fins in such a manner that both ends of the tube 2 are connected to a header 3. In this case, as a fin material, Al, Al alloy material which is more base at 50mV or higher than the potential of an outer surface of the tube is used. As a tube material, a brazing sheet of a three-layer clad in which Al-Si series brazing materials are clad on one side surface of an Al alloy core material containing 0.3-0.8% of Cu and Al or Al alloy sacrificial material which is more base than the potential of the core material is clad on the other side surface is used. Heat dissipating fins 1 and the tube 2 made of such materials are assembled, coated with fluoride series flux, dried, and brazed in a nonoxidative atmosphere to constitute the exchanger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an Al heat exchanger, and particularly to improve the corrosion resistance of the outer surface of a radiator, a parallel flow type condenser or the like.

[0002]

2. Description of the Related Art Various types of heat exchangers made of Al for automobiles are used, including radiators.
For example, in the radiator having the structure shown in FIG. 1, a commonly used material is a tube material having a plate thickness of about 0.4 mm.
A brazing sheet of layers, the outer surface of the tube is layered with JISA4343 (Al-7.5% Si), JISA4.
An Al-Si type brazing material such as 045 (Al-10% Si) is used for the layer which becomes the inner surface of the tube according to JIS A7072 (Al
-1% Zn), pure Al, etc. for sacrificial corrosion of a core material, which has a potential lower than that of the core material.
1-0.15% Cu-1.1% Mn) is used. The fin material is made of Al-1.1% Mn-1.5% Z in order to protect the tube in consideration of the corrosion resistance of the outer surface of the core.
A sacrificial fin having a plate thickness of about 0.1 mm, which has a potential lower than that of the outer surface of the tube, such as n or Al-0.1% In, is used. The header material is a 3-layer brazing sheet with a plate thickness of about 1.6 mm, and the core material is JI.
SA3003, Al-1% Zn-on the side where the heat medium flows
A 0.5% Mg alloy, and a brazing material such as JISA4343 or JISA4045 is used on the outer surface side of the core. These materials are molded into a predetermined shape, assembled, fixed with a jig, and generally degreased with an organic solvent such as trichloroethane or freon. And KAlF ₄ , K ₂ AlF ₅ · H
A 5% aqueous suspension of a fluoride-based flux of ₂ O, K ₃ AlF ₆ or the like is applied to the assembly by spraying or the like, and dried at about 200 ° C. to evaporate the water. After that, it is inserted into a brazing furnace in a non-oxidizing atmosphere replaced with nitrogen gas and the like, and heated to about 600 ° C. to perform brazing. After cooling, a plastic tank is attached to the header by caulking to complete the radiator. In this specification, the explanation of Al alloy composition is all
It means wt%, but it will be abbreviated as simply%.

[0003]

Corrosion resistance is one of the important properties required of the radiator thus manufactured. Regarding the corrosion resistance on the outer surface side, generally, a so-called sacrificial fin is used to protect the tube by preferentially corroding the fin by combination with a fin that is 50 mV or more less than the potential on the surface of the tube.
The problem here is the corrosive environment. In the concept of the sacrificial fin, an anticorrosive current flows between the fin and the surface of the tube through the electrolyte, and the tube can be protected only for the first time. For example, when the fin and the tube are not electrically connected to each other and only the surface of the tube is in a corrosive environment, the effect of the sacrificial fin is completely lost and the corrosion resistance is deteriorated.

[0004]

SUMMARY OF THE INVENTION In view of such a situation, the present invention has made various investigations and found a method for improving the corrosion resistance of a heat exchanger when the sacrificial fin has no or little anticorrosion effect. Then, by adding Cu to the tube core material, the potential difference between the core material and the surface of the brazing material is utilized to protect the tube from corrosion. That is, the present invention relates to a method for manufacturing a heat exchanger mainly composed of a tube through which a heat medium flows and a radiation fin, and as a fin material, a fin material of Al or Al alloy that is 50 mV or more less than the potential of the outer surface of the tube. With 0.3% Cu as the tube material
Al-Si brazing material is clad on one surface of the Al alloy core material containing 0.8% to 0.8%, and the other surface of the Al alloy has a lower potential than the core material.
Alternatively, a heat exchanger is assembled by using a brazing sheet of three-layer clad clad with an Al alloy sacrificial material, fluoride flux is applied, dried, and brazed in a non-oxidizing atmosphere. It is a manufacturing method of a heat exchanger.

[0005]

The heat exchanger to which the present invention is applied includes a radiator shown in FIG. 1, a parallel flow type condenser shown in FIG. 2, fins such as a heater (not shown), and a tube material having a brazing material layer on the outer surface. It is applicable to all heat exchangers consisting of a combination of.

The tube through which the heat medium flows uses a brazing sheet of three layers in which a brazing material is clad on one side and a sacrificial material is clad on the other side. It is formed into a flat shape by electric resistance sewing and molding so that

This sacrificial material is generally JISA7072.
(Al-1% Zn), other pure Al, Al-Ca
An alloy having a lower potential than the core material such as an alloy or an Al-Sn alloy can be used.

Generally, a JISA3003 alloy is used as the core material, but in the present invention, Cu of 0.3% to 0.
By using an Al alloy containing 8%, the potential of the core material is made nobler than the potential of the brazing material to improve the corrosion resistance of the tube material. The reason why the Cu content is limited to the range of 0.3% to 0.8% is that the effect is small if it is less than 0.3%.
This is because if it exceeds 0.8%, the potential becomes noble, but the self-corrosion resistance and the workability of the material are poor. Also add Cu A
l or Al alloy means 99.7% Al, JISA300
3 (Al-0.15% Cu-1.1% Mn), JISA
3203 (Al-1.1% Mn), JISA 3005
(Al-1.1Mn-0.4% Mg), JISA606
3 (Al-0.4Si-0.6Mg) and the like, and any alloy can be used as long as it is an alloy to which an element such as Zn, Ca, Sn, In having a base potential is not added. ..

The Al-Si type brazing material is at least Si.
Alloy containing 5 to 15% of the amount, for example, JIS4343,
JIS 4045, JIS 4047 and the like. It should be noted that these brazing filler metals may contain an element such as Bi that improves the fluidity of the brazing filler metal, an element such as Sn that lowers the melting point, or an element such as Zn that improves the corrosion resistance of the brazing filler metal.

Since the fins are used after corrugation and are combined with the brazing material clad tube, a bare material is generally used, but a brazing sheet fin material may be used. 50 mV from the outer surface of the tube
The above base fin material of Al or Al alloy is 99.7%
Al, Al 0.1% In alloy, pure Al-based alloy such as alloy having good thermal conductivity, Al-Mn-based, for example, Al-0.15% Cu.
-1.1% Mn-1.5% Zn alloy, etc., and any alloy can be used as long as it is substantially 50 mV or more base from the outer surface of the tube.

The corrugated fin (1), the electric resistance machined tube (2), and the header (3) are assembled and fixed by a jig. Then, it is degreased with an organic solvent such as CFC. Then, a 5% aqueous suspension of fluoride flux is applied by spraying or the like. Fluoride-based flux generally means KAlF ₄ , K ₂ AlF ₅ · H ₂ O, K ₃ Al.
The one containing at least one kind of F ₆ is used,
A flux to which other fluorides are added for improving performance such as improvement of brazing property, lowering of melting point and addition of corrosion resistance effect may be used. Any other fluoride-based flux that can be used for brazing Al may be used, and the flux is not particularly limited. Then, after applying the flux, drying is performed at about 100 ° C. to 300 ° C. to evaporate water. The core coated with the flux and dried is then brazed. Brazing is performed in a non-oxidizing atmosphere with a low dew point and a low oxygen concentration. Nitrogen gas is generally used to obtain this atmosphere, with a dew point of 40 ° C. and an oxygen concentration of 200.
Brazing at about ppm. The brazing temperature is determined depending on the melting point of the brazing material, the melting point of the material, and other performance problems, but is generally in the range of 590 ° C to 620 ° C. Since the material and the flux are oxidized and the brazing property is deteriorated, the higher the heating rate is, the better.

[0012]

EXAMPLES Al-0.1% In-0.15% Zr alloy,
A coil material having a thickness of 0.1 mm and a width of 16 mm and made of an Al-1.1% Mn-1.5% Zn alloy is corrugated,
Fin material was manufactured. Further, a core material having the composition shown in Table 1 and J
A brazing sheet for a tube having a plate thickness of 0.4 mm and having a brazing material clad ratio of 10% and a sacrificial material clad ratio of 10% was manufactured by a conventional method using a brazing material of ISA4045 alloy and a sacrificial material of JISA7072 alloy. Then, a tube material having a thickness of 2.2 mm and a width of 16 mm was manufactured with a general electric resistance welded pipe manufacturing facility so that the brazing material was on the outer surface side. Furthermore, as a header material, JIS A 4045 alloy brazing material and JIS
Using a core material of A3003 alloy and a sacrificial material made of JIS A7072 alloy, a plate material having a brazing material clad ratio of 5% and a sacrificial material clad ratio of 5% and having a thickness of 1.6 mm is manufactured, and press-formed into a header. processed. These members were assembled into a radiator as shown in FIG. 1, fixed with a jig, and degreased with freon. And KAlF ₄ , K ₂ Al
5% of fluoride-based flux composed of F ₅ · H ₂ O
The water suspension was applied by spraying and then inserted into a furnace heated to 200 ° C. to dry the water. Immediately after drying,
The sample was inserted into a brazing furnace heated to a temperature of 600 ° C. in a nitrogen gas atmosphere having a dew point of −40 ° C. and an oxygen concentration of 100 ppm, and brazing was performed while the actual temperature was kept at 600 ° C. for 3 minutes. Then it was taken out of the furnace. Further, a plastic tank was caulked and attached to the header through an O-ring to manufacture a radiator. A CASS test was performed for this radiator for 720 hours to measure the pitting depth on the outer surface of the tube. The results are also shown in Table 1.

[0013]

[Table 1]

As is clear from Table 1, No. 1 of the present invention example.
1-No. In No. 4, as a result of the corrosion test, the pitting depth is 0.1 mm.
It was below, and the corrosion resistance was excellent. On the other hand, Comparative Example No. which is out of the range of the present invention example. 5 to No. In No. 8, the pitting depth was 0.25 to 0.32 mm, and the corrosion resistance was poor.

[0015]

As described above, according to the present invention, the corrosion resistance on the outer surface side of the heat exchanger such as the radiator can be remarkably improved, and the industrially remarkable effect is exhibited.

[Brief description of drawings]

FIG. 1 is a schematic view of a radiator.

FIG. 2 is a schematic diagram of a parallel flow type condenser.

[Explanation of symbols]

 1 fin 2 tube 3 header 4 plastic tank 5 header pipe

Claims (1)

[Claims] 1. A method of manufacturing a heat exchanger mainly comprising a tube through which a heat medium flows and a radiation fin, wherein a fin material made of Al or an Al alloy that is 50 mV or more less than the potential of the outer surface of the tube is used as the fin material. As a tube material, an Al-alloy brazing material is clad on one surface of an Al alloy core material containing 0.3% to 0.8% of Cu, and Al or Al having a lower potential than the core material on the other surface. A heat exchanger made of Al, characterized in that a heat exchanger is assembled using a brazing sheet of three-layer clad clad with an alloy sacrificial material, fluoride flux is applied, dried and brazed in a non-oxidizing atmosphere. Manufacturing method.