JPS6264471A - Production of aluminum heat exchanger - Google Patents

Abstract

PURPOSE:To produce an Al heat exchanger having excellent corrosion resistance by combining Al members, brazing the members by a potassium fluoroaluminate flux in a non-oxidizing atmosphere and dissolving away the residue of the flux. CONSTITUTION:The Al or Al alloy members are brazed by using the potassium fluoroaluminate flux in the non-oxidizing atmosphere in the stage of combining said members and integrally joining said members to produce the heat exchanger. The flux or the like essentially consisting of any one kind of KAlF4, K2AlF5, H2O or K3AlF6 or >=2 kinds thereof is used as the potassium fluoroaluminate flux. The residue of the flux is dissolved away by immersing the joined member in an alkaline soln. such as caustic soda or acidic soln. such as nitric acid or hydrofluoric acid. The surface of the Al or Al alloy member is thereby made conductive and the corrosion resistance of the aluminum heat exchanger is improved.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to the method for producing aluminum heat exchangers using brazing, and particularly for improving the corrosion resistance of brazed aluminum heat exchangers. It is.

[Conventional technology]

In general, aluminum heat exchangers include the core of the drone cup type automatic 70 oil cooler shown in Figure 3 (a), the core of the tube and corrugated fin type automatic radiator shown in Figure 3 (b), The core of the serpentine type air conditioner condenser shown in FIG. 3(C), the core of the serpentine type air conditioner evaporator shown in FIG. 3(D), etc. are used.

The cores of these heat exchangers are basically made by combining the plating sheets shown in Table 1 and the Al or A1 alloy members shown in Table 2, and joining them together by brazing.

1st notation Heart material Leather material (brazing material)
Combined B△1: PC3003BA4343 One side Bha121] C300313△4343 Both sides [
(△2-.r'C69513A4343 One side 13
8220C et al.951 8△4343 Both sides BA23
1 C'3951 B△4045 One side (3△2
4PC6951BA4045 138 3PCs on both sides (
*) 3QO3!3A4003 One side B△, 4
PC<*) 3033 [3A4003 Both sides BA7PC(*) 3003 BA4004
one side! 3A8PC(*) 3QO3BA400
4 Both sides [389PC<*) 3003 B
△4005 Unilateral BAIOPC (*) 3003
BΔ4005 Both sides Bc171)C(*)
3003 r3A4NO4 one side 13A 18 PC(
*) 3003 B△4NO4 Both sides) r, (*) mark indicates Q empty praising sheet.

Table 2 Type Symbol 1〉Go XX series 1050.11C! 011200,
A, 1-o, s%C113xxX series 3003.300
4.3005, A, j-1, 1%Mn-2%Z05×〈
× system 5005.5050 6 x :< x system 6061.6063.6951
7XX (hereinafter referred to as NB brazing method) was the mainstream, but recently a method of brazing in a non-oxidizing atmosphere using a fluoride-based non-edible flux (hereinafter referred to as NB brazing method) has become mainstream.
law and abbreviation) came to be used. N13 method (yo3
This method uses flux at a low concentration of ~10%, and since the flux residue after brazing is non-corrosive, post-treatment is unnecessary, and other brazing methods require very little heat exchange. The manufacturing cost of the vessel is low.

[Problem that the invention seeks to solve]

In the FB method, Zn Cj! z is about 10% 1
-σ is included, and during this 70 minutes, it diffuses inside the surface layer of the heat exchanger member, forming a Znn diffusion layer with a maximum of ~2% and a diffusion depth of about 100 to 200μ, The potential becomes approximately -0.9V. This is the part of the heat exchanger member where ZO is not diffused) am (-0.70V ~ 0.75
v) On the other hand, the Znn diffusion layer acts as a sacrificial corrosion layer to prevent through-hole defects at angle t'1. However, in the NB method, since the flux used does not contain Zn, an In diffusion layer cannot be obtained, and deep pitting corrosion cannot be prevented.
do not have.

In order to achieve the same corrosion resistance as the Nf3 method and the FB method (this is a tube in which water or Freon flows through a (-1+-) T culm), a 7n diffusion layer of the same hair as the FB method is formed. 70 treatment or, in the case of the VB method, by sacrificing the base 1 fin of the potential known as the 7'3 method to improve corrosion resistance, prevent the circular tube body of the potential. s = K corrosion protection method is available.However, even when 7n treatment is applied with the NB method, and even in prefectural meetings using sacrificial 1'1 fins, cases have been reported in which through-pitting corrosion occurs in the pipe body1). ing.

(R: Means for solving the corner point) In view of this, the present invention has been developed as a result of various studies.
L, - remains as a residue on the surface of the heat exchanger, its main component (Al<Af F4, 3Al F6, etc.) is found to be densely adhered to the surface of the heat exchanger, but is non-conductive. Therefore, even if the fins etc. have a sacrificial corrosion effect, no anti-corrosion current will flow between the fins and the pipe body to be protected from corrosion, and even if the flux residue film is partially destroyed during the corrosion process, there will be no sufficient anti-corrosion current. We learned that the current does not flow, preventing pitting corrosion of the pipe body, and that the corrosion resistance of the aluminum heat exchanger brazed using the N13 method was improved as a result of further investigation based on these findings. We have developed a method for manufacturing aluminum heat exchangers that can

That is, the manufacturing method of the present invention involves brazing (or brazing by combining two alloy members (manufacturing of a heat exchanger joined together by J) in a non-oxidizing atmosphere using potassium fluoroaluminate flux. After brazing with aluminum, the flux residue is dissolved and removed to make the surface of the Al member conductive.

In the present invention, potassium fluoroaluminate fluxes include 1〈△fF+, Kz△fFs, Kz
Af "s ・l-120, to: A, e
A flux containing either one type of F6 or a mixture of two or more types of F6 as a main component, or a flux containing 50 to 6
Flux mixed at a ratio of 0W (%, 40 to 50W [%) is used. Also, there are various methods for dissolving and removing residual flux after brazing. For example, using an alkaline solution such as caustic soda, nitric acid, or hydrofluoric acid. , immersion in an acidic solution such as sulfur M in a cylinder is effective.

[Effect]

By dissolving and removing the non-conductive flux residue that adheres to the surface of the aluminum heat exchanger brazed using the NB method, the surface of the heat exchanger becomes conductive, and there is a gap between the fins and the anti-corrosion tube. A sufficient anticorrosion current flows, and pitting corrosion of the tube body can be effectively prevented. As mentioned above, the surface of the aluminum heat exchanger should be left with non-conductive flux or hardened. Corrosion-preventing current does not flow between the fins and the anti-corrosion tubes, so it is not possible to prevent pitting corrosion on the tube bodies. A sufficient anti-corrosion current flows between the bodies, preventing pitting corrosion in the tube bodies, and making it possible to lengthen the RQ of the heat exchanger.

[Example 1] 1 with a thickness of 1 mtn, a width of 50 mttt, and a length of 50 tum.
050 alloy (I14 thinner than 99.50% pure Al) 1
~ After degreasing with Reclen, KAfF+ was immersed in a flux solution in which KAfF+ was suspended in water at a temperature of 10%, and dried at a temperature of 110° C. for 30 minutes. Regarding this, imitating the NB method, N
After heating at a temperature of 610° C. for 10 minutes in a Z gas atmosphere, the flux residue stuck to the surface was dissolved and removed by the dissolution process shown in Table 3. Regarding this, the conductivity of the surface was examined using a tester. The results are also listed in Table 3.

Table 3 Manufacturing ri=No Melting treatment
Process Surface metaelectricity Inventive method 15%Na 0f
-1・60℃×1 minute→Washing→ Yes 30% 1-IN
O3/room temperature x 1 minute → washing with water → drying! ! 230%liN 03 ・Room temperature x 20 minutes - Washing with water → Yes Drying II 35% LiN 03 ・Room temperature x 2 minutes -) Washing with water →
Dry with drying method 41 H2SO4・50℃×2 minutes → Water (5 in 1 → Conventional method with drying 5 Ec)
None As is clear from Table 3, the method of the present invention is NG.
The conductivity of the surface was determined by dissolving and removing the residual flux stuck to the surface in steps 1 to 4 ([1], but in conventional method NO, which does not involve dissolution treatment, the surface became non-conductive due to the adhesion of the residual flux). It turns out that it is.

・'Example 2] 0'! As shown in Figure 1J, an extruded multi-hole tube (1) made of 1050 alloy is made of 8 (-1% Mn -2% Zn alloy as the core + O, and 10% on both sides at -). 1:3
A corrugated fin (2) made of a plating sheet clad with 4045 alloy < A f -10% 3i alloy) was assembled, fixed with an iron jig and degreased with trichlene, and then KAAF was applied at a concentration of 10%. It was immersed in a flux solution suspended in water and dried at a temperature of 110° C. for 30 minutes.

This was heated to a temperature of 610° C. for 10 minutes in a Nz gas atmosphere to perform brazing. This was subjected to the dissolution treatment process shown in Table 4 to dissolve and remove the flux residue adhered to the surface, thereby producing a core for an evaporator of a repentine ink.

Regarding this, a salt water spray test based on JIS Z2371 was conducted for 1000 hours, and the maximum depth of pitting corrosion occurring in the extruded multi-hole tube was measured. The results are shown in Table 4 ()f.

Table 4 Manufacturer: 7 people 11'0
Surface conductivity Maximum pitting depth (m) Method of the present invention 6
Wash 5% Na OH "60" CX 1 minute with water → Yes 0.130% l-1 NO3 at room temperature x 1 minute →
Washing with water → drying r7 730% 1l NO5 - room temperature x 10 minutes - → washing with water →
Yes 0.2 dry, t 85% IF, room temperature x 2 minutes -→Wash>
Yes 0.2 drying... 91 is 1-1zSO+ 50℃ x 2 minutes -→
Water washing → Yes 0,1 snake operation 11 people +0 1;;shi
None 0.7 As is clear from Table 4, the maximum pitting depth of the extruded multi-hole tube in two cores is b
It can be seen that the corrosion resistance is as shallow as 0.1 to 0.2 mm and has good corrosion resistance. On the other hand, in the conventional method in which the flux residue is not dissolved, the maximum pitting depth is as deep as 0.7 mm compared to C.

[Example 3] As shown in Figure 2, 3003 alloy (8(-0.1% Cu
-1,2% Mn alloy) as the core material, and one side of it has [3Δ
A to B clad with 4343 alloy (A!-7,5% S1 alloy) between flat chicoves (3) made of 11PC,
A rugate fin (4) made of e-1%Mn-2%70 alloy is provided, and plates (6) made of BAIIPC are provided at both ends of the rugate fin (4), and 1 night blade made of BΔ11PC is provided on both sides! - Attach (, 5) and assemble a small automatic radiator, fix it with a jig and perform tri-clean vapor degreasing. In the figure, (7) shows a plastic tank.
. In addition, the voltage Q of the core material (3003 alloy) of the flat tube (3) made of 11PC to B is -0.7V (measured with saturated Amagi electrode, 5% NaC,e, at 25°C), 8 (-1 %
The potential of the corrugated fin made of M11-2%711 is -0,9V.

Next, this was immersed in a flux solution containing KAfF+ suspended in water at a concentration of 10%, dried at a temperature of 110°C for 30 minutes, and then heated to a temperature of 610°C in a Nz gas atmosphere for 14 minutes.
Brazing was performed by heating for 0 minutes. This is 5% of room temperature.
After being immersed in HF for 2 minutes, it was washed with water and dried to dissolve and remove the flux residue stuck to the surface. Regarding this, along with conventional products that do not remove flux residue, JIS Z23
A salt spray test based on 71 was conducted and the time required for 4-pass pitting to occur on a flat decoup was compared.7 As a result, while the conventional product caused 4-pass pitting at 15,001 tN, the method of the present invention It took 4,500 hours for the manufactured radiator to generate 1 d-time eclipse.

〔Effect of the invention〕

As described above, according to the present invention, the corrosion resistance of aluminum heat exchangers can be improved and the corrosion resistance can be improved by more than three times, resulting in a remarkable industrial effect.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of a core for an IL-Bentine type evaporator, Fig. 2 is an explanatory diagram showing an example of a core for an automobile radiator, and Fig. 3 (a), (())
, (C), and (D) show examples of various cores for single-aluminum heat exchangers; (A) is the core of a Dron cup type automobile oil cooler; (B) is the core of an automatic heavy duty radiator; (c) shows the core of a serpentine-type condenser, and (d) shows the core of a serpentine-type evaporator. 1... Extruded multi-hole Chicove 2... Corrugated fin 3... Flat tube 4... Corrugated fin 5... → Noid bracket 6... Plate 7... Plastic gastric tank Figure 1, Figure 2 Figure 3 (B) (C)

Claims (1)

[Claims] In the manufacture of heat exchangers that combine Al or Al alloy members and join them together by brazing, after brazing in a non-oxidizing atmosphere using potassium fluoroaluminate flux, the flux residue is dissolved and removed to form an Al Or a method for manufacturing an aluminum heat exchanger, characterized in that the surface of the Al member is conductive.