JPH04100674A - Production of brazing sheet for flux brazing - Google Patents

Abstract

PURPOSE:To remove surface stains and oxide films and to obtain a brazing sheet having excellent flux brazability by etching and neutralizing the surfaces of the brazing sheet. CONSTITUTION:The surface of the aluminum brazing sheet formed by cladding an Al-Si alloy as a brazing material is etched at 0.01 to 1.5g/m<2> with an alkaline soln. and is then neutralized in the production of this brazing sheet. Since the surface films are removed and the wettability with a flux liquid is improved, the brazing property is improved. The amt. of the flux to be used is decreased and the flux residues are thereby decreased and, therefore, the coatability, corrosion resistance and heat exchange performance are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a brazing sheet for flux brazing, and particularly to a method for improving brazing properties.

[Conventional technology]

JIS 3003 alloy is generally used for flux brazing when manufacturing heat exchangers for automobiles.

A brazing sheet is used in which the surface of a core material of JIS 3005 alloy or JIS 6951 alloy is clad with a brazing material made of JIS 4343 alloy or JIS 4045 alloy, which is an AO-Si alloy. Generally, the plate material of the heat exchanger has a thickness of 0.5 to 21 nm.
In, a material having a thickness of 0.1 to 0.2 mm is used as the fin material.

For example, taking a radiator as an example, as shown in Figure 1, the header (8) to which the resin tank Q (It is attached via the rubber gasket (9)) is made of a 1.6 mm thick brazing plate clad with brazing filler metal on one side. The material of the tube (7) through which the sheet and the refrigerant flow is made of a brazing sheet with a thickness of 0.4 mm clad with brazing metal on one side and subjected to electric resistance welding.The material of the fin (6) is J.I.
A bare material made of S5XXX alloy with a plate thickness of 0.1++ on is used.

By the way, among the flux brazing properties, the brazing method, which uses a fluoride-based non-corrosive flux and performs brazing heating in an inert gas at atmospheric pressure, has recently become popular. The reason for this is first that the flux concentration is about 3wt%, which is 5% compared to the conventional wax method using chloride flux.
This is because the concentration is extremely low compared to 0 to 60 wt%, and the amount of flux used is small, which is effective in reducing costs. The second reason is that according to the brazing method using this fluoride flux, the flux residue remaining on the aluminum surface after brazing is non-corrosive to the aluminum, so there is no need to remove the flux residue. It's for a reason.

On the other hand, when conventional chloride-based fluxes are used, cleaning treatments such as hot water washing and nitric acid washing are required after brazing, which is also a problem in terms of pollution.

[Problems to be Solved by the Invention] However, since this fluoride flux is insoluble in water, it is difficult to uniformly apply a low concentration flux to the surface of the brazing sheet as described above. This is because the surface of the brazing sheet exhibits water repellency due to adhesion of rolling oil, which also makes uniform application more difficult.

To deal with this, in practice, the flux concentration was increased slightly or a surfactant was added to the flux liquid to increase the amount of flux deposited and ensure brazability.

However, increasing the amount of flux deposited in this way is disadvantageous in terms of cost, and this also results in a large amount of flux residue after brazing, which not only reduces paintability and corrosion resistance, but also In areas where flux tends to aggregate, such as the louvers and fillets of heat exchanger fins, residue clumps occur, increasing ventilation resistance and reducing heat exchange performance. Put it away.

In addition, when brazing in an inert gas, the dew point of H2O, which is an oxidizing gas, is -40°C or less, and the dew point of 02 is 11000p.
It is necessary to regulate the temperature to below p, and there is also a problem of deterioration in brazing properties due to changes in the atmosphere.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention provides a brazing sheet that has excellent flux brazing properties by removing surface dirt and oxide film by etching and neutralizing the surface of the plain sheet. This reduces the amount of flux used and eases regulations on oxidizing gases in the brazing atmosphere.

That is, in the production of an aluminum brazing sheet clad with AQ-Si alloy as a brazing material, the surface of the sheet is coated with an alkaline solution at 0.01-1.5 g/m
``It is characterized by etching and then neutralization treatment, and the etching treatment is performed before the final annealing of the brazing sheet, or after the rolling and annealing process of the brazing sheet is completed. It is valid.

[Effect]

In this way, the amount of alkaline etching is 0.01 to 5 g/a.
The reason why it was set as +2 is that if it is less than 1 g/m2 of O, there is no effect of improving brazing properties, and if it exceeds 5 g/m2, Si particles will drop off from the surface of the brazing sheet and the surface unevenness will increase. This is because the brazing properties deteriorate. Alkaline etching may be carried out at a temperature of 30 to 70 DEG C. with an aqueous NaOH solution having a concentration of 1 to 5%.

After alkaline etching, it is necessary to wash with water and nitric acid for the purpose of removing and neutralizing smut. This smut removal and neutralization treatment may be carried out at room temperature with a nitric acid aqueous solution having a concentration of 5 to 30%, but it is necessary to wash with tap water at room temperature before and after washing with nitric acid.

Further, the above-mentioned cleaning treatment may be carried out by dipping or spraying, but in order to continuously treat rolled coils, it is possible to increase the line speed by employing spray cleaning which has strong etching power and neutralizing power.

After the water treatment, it is important to dry the brazing sheet at 80 to 150°C so that no moisture remains on the surface of the brazing sheet.

The reason why the above etching treatment is performed before the final annealing is as follows.

In other words, a large amount of rolling oil residue and aluminum abrasion powder adheres to the surface of a brazing sheet that has been hot-rolled or cold-rolled, and if annealed in this state, oil and dirt will seize and the surface quality will deteriorate. deteriorates significantly. Therefore, by cleaning before the final annealing, these surface foreign substances can be removed, so that the only change due to annealing is a slight increase in the film thickness. The annealing atmosphere is 0□ and H2020.
If the annealing is carried out in a low amount of annealing gas, the increase in film thickness can be minimized. This treatment is suitable for producing O material (tempered material), which is an annealed material.

Furthermore, if the above-mentioned etching treatment is performed after rolling and annealing, it is possible to easily remove oil, dirt, etc. that have been baked in by the annealing. However, compared to the etching treatment before the final annealing described above, the amount of etching in this case needs to be larger. This treatment involves cold rolling after annealing (H material).
suitable for manufacturing.

〔Example〕

Next, examples of the present invention will be described.

<Example 1> When manufacturing a brazing sheet in which JIS 4045 alloy filler metal was clad on both sides of a JIS 3003 alloy core material to a thickness of 10%, the thickness of the clad material was made 5 mm by hot rolling, and then cold rolling was performed. After rolling to a thickness of 0.5 mm, alkali cleaning was performed under the conditions shown in Table 1. Thereafter, a final annealing of 360'CX 2 Hr was performed in an inert gas to obtain a 0.6 mm thick zero material. Note that smut removal and neutralization treatment after alkali cleaning were performed in the following steps.

That is, (room temperature x 30 seconds) (60°C x 30 seconds) (90°C x 10 seconds)
The weight before and after washing was measured to calculate the amount of etching, and the pressure resistance and occurrence of solder breakage on the outside were investigated as follows. The results are shown in Table 1.

That is, by using a brazing sheet that has been subjected to alkali cleaning, that is, etching treatment under each of the above conditions, as shown in FIG.
Cup molded product with an opening in the center and an exhaust port (2)
1) was produced. And as a flux K AQF
, resin, AQF, etc.
% concentration, applied to each of the cup molded products separately and dried at 150°C, and then stacked these cup molded products (1) alternately to form three cup molded products, as shown in Figure 3. The hollow structure (3) was assembled into a hollow container shape that communicated with the exhaust port (2), and the pressure tester connection port (5) was attached to the exhaust port (2) of the cup molded product (1) at the upper end. . Then, store this hollow container at a dew point of -60°C and the amount of 02 is 9ooppm.
They were heated to 595° C. in a N2 gas atmosphere to perform brazing and integrate, and five integrated hollow containers (hereinafter referred to as cores) were produced for each etching treatment condition.

These cores were visually inspected for solder breaks on the outside, and if one or more cores had one or more breaks in the solder, it was determined that there was a break in the wax, and how many of the five cores had breaks in the wax. I wrote down the following.

In addition, high-pressure air was introduced through the connection port (5), and the pressure strength of the five cores was examined, and the average value was recorded.

Note that the cup molded product at the bottom of the hollow container is a cup molded product without holes (4).

As is clear from Table 1, the compressive strength of the cores produced by the method of the present invention was all 38 kgG/ci or more, and they exhibited excellent brazing properties without any brazing breakage.

On the other hand, cores made by Comparative Method No. 6 with a small amount of etching, cores made by Comparative Method No. 9 without nitric acid neutralization, and cores made by Comparative Method No. 9 without alkaline cleaning are 3.
The pressure resistance was only about 4 to 35 kgG/cd, and wax breakage also occurred. Comparative method No. 7, which had a large amount of etching, had relatively high pressure resistance, but cracking of the solder occurred.

<Example 2> When manufacturing a fin material consisting of a brazing sheet in which JIS 4343 alloy brazing filler metal is clad on both sides of a JIS 3003 alloy core material to a thickness of 10%, the cladding material is hot-rolled to a thickness of 5 mm. After that, it was cold rolled to a thickness of 0.20 mm, then intermediate annealed at 360°C for 2 hours, and further cold rolled to a thickness of 0.16 mm.
+a fin material was used, and then alkaline cleaning was performed under each condition shown in Table 2.

Note that the neutralization treatment conditions for those that were subsequently subjected to neutralization treatment were the same as in Example 1.

Then, the etching amount was calculated in the same manner as in Example 1, and the results are also listed in Table 2.

In addition, as shown in Fig. 4, a capacitor mini core was prepared by combining the corrugated fin σD under these conditions with a JIS 1050 material extruded tube (2), and then the same fluoride flux as in Example 1 was used. was applied at a concentration of 1%, and brazing was performed under the same conditions as in Example 1.

And 1 of the corrugated fin mountain α, which is the connection between the fin opening υ of each mini-core and the extruded tube (2) shown in Fig. 4.
The number of ridges of joints with good brazing per 00 pieces was investigated, and the ratio of the number of ridges to the total number of ridges was calculated as the bonding rate, and the results are also listed in Table 2.

As can be seen from Table 2, for the mini cores using the fin material according to the present invention, the fin bonding rate was 95%.
As described above, good bondability was exhibited even under severe brazing conditions using low concentration flux. On the other hand, Comparative Method No. 17 without alkaline cleaning and Comparative Method N with insufficient cleaning.

, No. 14 had a low bonding rate of 85% because the flux liquid did not sufficiently wet the fin surface, and No. 16, which had no neutralization treatment, had a particularly poor bonding rate.

〔Effect of the invention〕

As described above, according to the present invention, by subjecting the brazing material to moderate alkaline etching combined with neutralization treatment, the surface film can be removed and the wettability of the flux liquid can be improved, thereby improving brazing properties. According to the present invention, it is possible to reduce the amount of flux used, and as a result, flux residue is reduced, resulting in significant effects such as improvement in paintability, corrosion resistance, heat exchange performance, etc.

[Brief explanation of drawings]

Figure 1 is a partially cutaway perspective view of the radiator, Figure 2 (
A) (B) shows a cup molded product for brazing test. (A) is a plan view, (B) is a cross-sectional view along the YY line of
The figure is a side sectional view of a hollow container for pressure resistance tests in which cup molded products are combined, and FIG. 4 is a perspective view showing a mini-core of a capacitor for brazing tests. ■ Cup molded product exhaust port Hollow structure No hole Cup molded product Pressure tester Connection port Fin tube Header Rubber packing Resin tank Extruded tube Corrugated fin mountain Figure 1 Figure 2

Claims (3)

[Claims] (1) In manufacturing an aluminum brazing sheet clad with Al-Si alloy as a brazing material, the surface is etched with an alkaline solution of 0.01 to 5 g/m^2, and then neutralized. A method for producing brazing sheets for flux brazing. (2) The method for producing a brazing sheet for flux brazing according to claim (1), wherein the etching treatment is performed before final annealing of the brazing sheet. (3) The method for producing a brazing sheet for flux brazing according to claim (1), wherein the etching treatment is performed after the rolling and annealing process of the brazing sheet is completed.