JPH04270059A - Production of heat exchanger made of al - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of the external tube surface of a heat exchanger made of A1 consisting of a combination of a fin and a tube having a brazing filler metal layer on the external tube surface, such as radiator and parallel flow type capacitor. CONSTITUTION:The heat exchanger made of Al is produced by using, as a fin material, a bare material of Al alloy containing >=0.5% Zn, also using, as a tube material, a brazing sheet, where at least the side, to be the outer side of a tube, of an Al alloy core material is clad with an Al-Si brazing filler metal to >=15mum thickness, assembling a heat exchanger, applying a fluoride type flux, drying this flux, and then exerting brazing in a nonoxidizing atmosphere.

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 in particular to improving the corrosion resistance of the outer surface of tubes such as radiators and parallel flow type condensers.

0002

2. Description of the Related Art Various types of aluminum heat exchangers are used for automobiles, including radiators. In this specification, all descriptions of Al alloy compositions mean wt%, but this will be abbreviated to simply %. For example, in the radiator with the configuration shown in Figure 1, the tube material generally used is a three-layer brazing sheet with a thickness of about 0.4 mm, and the outer layer of the tube is JISA4343 (Al-7.5% Si), JI
An Al-Si brazing filler metal such as SA4045 (Al-10%Si) is used as the inner layer of the tube according to JISA7072 (
A sacrificial anode material with a lower potential than the core material that sacrificially protects the core material such as Al-1%Zn), pure Al, etc., and the core material is JISA30.
03 (Al-0.15%Cu-1.1%Mn) is used. In addition, the fin material is made of Al-1.1%Mn-1.5 to protect the tube considering the corrosion resistance of the outer surface of the core.
A sacrificial fin with a plate thickness of about 0.1 mm and having a potential less noble than the potential of the outer surface of the tube, such as %Zn or Al-0.1%In, is used. In addition, a three-layer brazing sheet with a thickness of about 1.6 mm is used for the header material, and the core material of this brazing sheet is JISA3003, and the side where the heat medium flows is Al-1%Zn-0.5%Mg. alloy,
A brazing material such as JISA4343 or JISA4045 is used on the outer surface 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 fluorocarbon. and KAlF4, K2 AlF5 ・H2 O, K
3 5% of fluoride flux consisting of AlF6 etc.
An aqueous suspension of about 200° C. 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 purged with nitrogen gas, etc., and heated to about 600° C. to perform brazing. After cooling, the plastic tank is attached to the header by caulking to complete the radiator.

0003

[Problems to be Solved by the Invention] Corrosion resistance is one of the important characteristics required of radiators manufactured in this manner. Regarding the corrosion resistance of the outer surface of the tube, it is generally 50% lower than the potential of the tube surface.
A so-called sacrificial fin concept has been adopted in which the tube is protected by preferentially corroding the fin in combination with a fin that is more base than mV. The problem here is the corrosive environment. In the sacrificial fin concept, the tube can only be protected when a corrosion protection current flows between the fin and the tube surface via an electrolyte. For example, if the fins and the tube are not electrically connected and only the tube surface becomes a corrosive environment, the sacrificial fin will have no effect at all. For example, considering the case where the fin component contains Zn, during brazing, Zn in the fin diffuses into the tube core material through the molten solder. This Zn acts as a sacrificial layer because its potential is slightly less noble than that of the undiffused core material. However, when the thickness of the solder in the tube is small, that is, when there is little molten solder, Zn in the fins becomes difficult to diffuse into the tube core material, and the effect as a sacrificial layer protecting the core material cannot be obtained.

0004

[Means for Solving the Problems] In view of the above-mentioned circumstances, the present invention has been made as a result of various studies and has discovered a manufacturing method for improving the corrosion resistance of an Al heat exchanger using sacrificial fins containing Zn. That is, the invention as claimed in claim 1 is a method for manufacturing an Al heat exchanger mainly composed of tubes through which a heat medium flows and radiation fins, in which bare aluminum alloy containing 0.5% or more of Zn is used as a fin material. Assemble the heat exchanger using a brazing sheet in which at least the outside surface of the Al alloy core material is clad with Al-Si brazing material to a thickness of 15 μm or more as a tube material,
A method for manufacturing an Al heat exchanger, characterized in that a fluoride flux is applied, dried, and brazed in a non-oxidizing atmosphere. In the method for manufacturing an Al heat exchanger having fins as the main part, Zn is used as the fin material at 0.
Contains 5% or more, and further contains Sn and In of 0.005 to 1 each
A bare material of an Al alloy containing one or two types in an amount of 10% is used, and a brazing sheet is used as a tube material in which at least the outside surface of the Al alloy core material is clad with an Al-Si brazing filler metal of 15 μm or more. 3. A method of manufacturing an Al heat exchanger, which comprises: assembling the heat exchanger, applying a fluoride flux, drying, and brazing in a non-oxidizing atmosphere; The tube material is Al-Si on one side which is the outside of the tube with an Al alloy core material.
3. The heating system according to claim 1, wherein the brazing sheet is made of a three-layer cladding sheet in which the other surface, which is the inner side of the tube, is clad with Al or an Al alloy having a more noble potential than the core material. This is a method for manufacturing an exchanger.

[0005]

[Operation] The heat exchanger to which the present invention is applied is any type of heat exchanger consisting of a combination of fins and a tube having a brazing metal layer on the outer surface, such as the radiator shown in Fig. 1, the heater, and the parallel flow type condenser shown in Fig. 2. Applicable to heat exchangers. The tube through which the heat medium flows is made of a brazing sheet in which at least one side of the outer surface of the tube is clad with a brazing material, and the coiled brazing sheet is continuously clad in the tube so that the brazing material is on the outside surface. The material is electrically welded and formed into a flat tube. When used as a radiator tube, a three-layer brazing sheet is used, and the outer surface of the tube is clad with a brazing material and the inner surface is clad with a sacrificial material that protects the core material. This sacrificial material is generally JISA7072 (Al-1%Zn), and other alloys having a more base potential than the core material, such as pure Al, Al--Ca alloy, and Al--Sn alloy, are used. Also, the core material is generally JI
SA3003 alloy is used, but other Al-1
%Mn-0.5%Cu alloy, heat treatment system Al-Mg-S
Any alloy such as an i-based alloy or an Al-Mg-Si-Mn-Cu based alloy can be used. In parallel flow type capacitors, the outside of the tube is generally clad with a brazing material, and the inner surface of the tube is not clad or is clad with a brazing material and is generally used as an electric resistance welded tube. Al-Si brazing filler metal is an alloy containing at least 5 to 15% Si, for example, JIS4343, JI
S4045, JIS4047, etc. Note that these brazing fillers may contain elements that improve the fluidity of the brazing filler metal, elements that lower the melting point, elements that improve the strength, elements that improve the corrosion resistance of the brazing filler metal, and the like. The reason why the thickness of the brazing filler metal is set to 15 μm or more is to improve corrosion resistance by diffusing the Zn of the fins to the tube surface through the molten solder, but if it is less than this, there will be little Zn diffusion and there will be sufficient Zn on the tube surface. This is because a diffusion layer is not formed, making it impossible to protect the tube and resulting in poor corrosion resistance. The fins are corrugated and combined with a brazing filler metal clad tube, so it is common to use bare material. The fin must contain Zn at least 0.5%; if it is less than this, Zn will not diffuse into the tube effectively and will not work effectively. Moreover, if the amount is too large, the corrosion resistance of the fin itself will deteriorate, so it is best to keep it at about 3%. The base alloy to which Zn is added is pure Al, JISA300
3. Alloys such as JISA3203 and JISA6951,
Al or Al alloy containing at least one of Sn and In, Al or Al alloy containing at least one of Ca and Li
Alloys containing more than one species. Note that the content of Sn and In contained in the Al alloy of the fin material is preferably in the range of 0.005 to 1%, respectively. Below the lower limit, the potential will not become base and a sufficient sacrificial effect will not be obtained. If the upper limit is exceeded, plastic workability and self-corrosion resistance will be poor. Any other alloy can be used as long as the potential of the fin is less base than that of the tube surface. Then, as shown in Figure 1, the corrugated fin (1
) and ERW processed tube (2), and header (3)
and are assembled into the heat exchanger and fixed with a jig. Then, it is degreased using an organic solvent such as Freon. Then, a 5% aqueous suspension of fluoride flux is applied by spraying or the like. Fluoride flux is generally KAlF.
4, K2 AlF5 ・H2 O, K3 AlF6
A flux containing at least one type of fluoride is used, but a flux to which other fluorides are added to improve performance such as improving brazing properties, lowering the melting point, and adding corrosion resistance effects may also be used. Any other fluoride-based flux that can be used for brazing Al may be used. After applying the flux, drying is performed at about 100°C to 300°C to evaporate water. The core is coated with flux and dried.
Next, brazing is performed. Brazing is performed in a non-oxidizing atmosphere with a low dew point and low oxygen concentration. To obtain this atmosphere, nitrogen gas is generally used and brazing is performed at a dew point of -40°C and an oxygen concentration of about 200 ppm. The brazing temperature is determined by the melting point of the brazing material, the melting point of the material, and other performance issues, and is approximately in the range of 590°C to 620°C. Note that the faster the temperature increase rate, the better, as the material and flux will oxidize and deteriorate brazing properties.

[0006]

[Example 1] A fin material was produced by corrugating a coil material made of a fin alloy having the composition shown in Table 1 and having a thickness of 0.1 mm and a width of 16 mm. Also JIS
A4045 brazing metal and Al-0.5%Cu-1.1%M
With core material of n alloy and sacrificial material of JISA7072 alloy,
Tube materials having a plate thickness of 0.3 mm and having a sacrificial material cladding ratio of 10% were manufactured by a conventional method by changing the thickness of the brazing material as shown in Table 1. Then, so that the brazing material is on the outside side, it is made into a tube with a thickness of 2.2 mm and a width of 1 mm using general electric resistance welded pipe manufacturing equipment.
A 6 mm tube material was manufactured. Furthermore, a JISA4045 alloy brazing material is used as a header material, a JISA3003 alloy core material, and a sacrificial material made of an Al-1%Zn-0.5%Mg alloy, with a brazing material cladding ratio of 10% and a sacrificial material cladding ratio of 10%. A plate with a thickness of 1.6 mm having the following configuration was manufactured and press-molded into a header. Assemble these members into a radiator as shown in Figure 1, fix them with a jig,
Then, it was degreased with Freon. And KAlF4 and K
A 5% aqueous suspension of fluoride flux having a composition of 2AlF5 ・H2O was applied by spraying, and then 2
It was inserted into a furnace heated to 00°C to dry moisture. Immediately after drying, it was inserted into a brazing furnace heated to 600°C in a nitrogen gas atmosphere with a dew point of -40°C and an oxygen concentration of 100 ppm, and the actual temperature was maintained at 600°C for 3 minutes for brazing. Then I took it out of the furnace. Furthermore, a radiator was manufactured by caulking and attaching a plastic tank to the header via an O-ring. Regarding this radiator, the state of Zn diffusion from the outer surface of the tube (Zn concentration % on the surface of the tube brazing material) was investigated, and a CASS test was conducted for 720 hours to measure the depth of pitting on the outer surface of the tube. The results are also listed in Table 1.

[0007]

[Table 1]

As is clear from Table 1, the No.
．． 1~No. 6, the Zn concentration on the tube surface is 0.5~
As a result of the corrosion test, the pitting depth on the outer surface of the tube was 0.1 mm or less, and the corrosion resistance was excellent. On the other hand, Comparative Example No. 1 has a thin brazing material that is outside the scope of the present invention. 7.No. 8. Comparative example No. with a small amount of added Zn in the fin. 9, No. In No. 10, the Zn concentration was low and through-pitting corrosion occurred in the tube, resulting in poor corrosion resistance.

[0009]

As described above, according to the present invention, the corrosion resistance of the outer surface of the tube of a heat exchanger such as a radiator can be significantly improved, and a remarkable effect can be achieved industrially.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram 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 (3)

[Claims] Claim 1. A method for manufacturing an Al heat exchanger mainly composed of tubes through which a heat medium flows and radiation fins, using bare Al alloy material containing 0.5 wt% or more of Zn as the fin material, As a tube material, a heat exchanger is assembled using a brazing sheet in which at least the outside surface of the Al alloy core material is clad with Al-Si brazing filler metal of 15 μm or more, and a fluoride flux is applied and dried. A method for manufacturing an Al heat exchanger, characterized by brazing in a non-oxidizing atmosphere. 2. A method for manufacturing an Al heat exchanger mainly composed of tubes through which a heat medium flows and heat dissipation fins, wherein the fin material contains 0.5 wt% or more of Zn, and further contains 0 each of Sn and In. A bare Al alloy material containing one or two types in an amount of .005 to 1 wt% is used as a tube material, and at least the outside surface of the Al alloy core material is clad with an Al-Si brazing filler metal of 15 μm or more. A method for manufacturing an Al heat exchanger, which comprises assembling the heat exchanger using a brazing sheet, applying fluoride flux, drying, and brazing in a non-oxidizing atmosphere. 3. The tube material has an Al alloy core material, and has an Al-Si brazing filler metal on one side that is the outside of the tube, and an Al or Al alloy that has a less potential than the core material on the other side that is the inside of the tube. 3. The method for manufacturing a heat exchanger according to claim 1, wherein a three-layer cladding brazing sheet is used.