JPH04100696A - Production of brazing sheet for vacuum brazing - Google Patents

Abstract

PURPOSE:To improve the reliability of a brazed part by etching the surface of the Al brazing sheet consisting of an AlSi-Mg alloy as a brazing material at a specific rate by an alkaline soln., then subjecting this sheet to a neutralizing treatment in the production of the magnetic brazing sheet. CONSTITUTION:The surface of the Al-Si-Mg alloy as the brazing material is etched at 0.02 to 5g/m<2> by the alkaline soln. and is then subjected to the neutralizing treatment in the production of the magnetic brazing sheet. The execution of the etching treatment before the final annealing of the brazing sheet or after the end of the rolling and annealing stage of the brazing sheet is effective. The brazing sheet is subjected to the alkaline etching of about the middle degree, by which the pressure resistant strength of a joining member and the reliability of the brazed part, such as suppression of the generation of brazing material run-out, are improved in this way. The brazability is stabilized in spite of some fluctuations in brazing conditions.

Description

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

[Conventional technology]

Vacuum brazing is generally used to manufacture heat exchangers made of aluminum and having a hollow structure, such as the Dron cup type evaporator conventionally used for automobiles. This vacuum brazing property is achieved by JIS 40, which is an AO-Si-Mg alloy on the surface of the core material of JIS 3003 alloy, JIS 3005 alloy, or JIS 6951 alloy.
Brazing is performed under vacuum using a brazing sheet clad with a brazing material made of 04 alloy or JIS 4104 alloy.

However, in the case of a heat exchanger having a hollow structure like the one mentioned above, the Mg contained in the brazing filler metal is insufficiently evaporated, and the brazing properties inside the assembled members become unstable.

Therefore, as a method to eliminate such instability, a technique has been disclosed in which the surface of the brazing sheet is cleaned with acid or alkali. Therefore, a method for manufacturing the plate material and fin material of the evaporator using this method will be specifically explained below.

That is, the plate material is manufactured as an annealed material (O material) through the steps shown in FIG. 1, while the fin material is manufactured as a rolled material (H material) as shown in FIG. The above-mentioned cleaning of the brazing sheet may be carried out one or more times at any of the steps indicated by A in FIGS. 1 and 2.

[Problem to be solved by the invention]

However, since such alkaline cleaning strongly etches the surface of the brazing material of the brazing sheet, the following problems occur unless the etching conditions, including water washing and neutralization, are not appropriate.

(2) Si particles in the brazing material fall off due to etching, making it difficult for the surface of the brazing material to melt during brazing.

■When unevenness is formed on the surface by etching, the press oil used during press forming in the pre-brazing process gets into these recesses, and degreasing with solvent becomes insufficient, so this press oil is carried into the brazing furnace. It may cause oil contamination in the furnace or reduce brazing performance.

(2) Si and Fe compounds generated during etching remain on the surface of the brazing sheet and impede the flow of wax during brazing.

■If Na ions cannot be removed sufficiently, moisture in the air will be taken in and a thick hydroxide film will be formed, reducing brazing properties.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention has been developed to produce a brazing sheet with excellent vacuum brazing properties by suppressing the etching conditions with alkali to a lower level than before, and by eliminating any residual alkaline content through water washing and neutralization. The present invention provides a method.

That is, in the production of an aluminum brazing sheet clad with an AO-3t-Mg alloy as a brazing material, the surface of the sheet is coated with an alkaline solution in an amount of 0.02 to 5 g.
/m2 etching and then neutralization treatment, and it is effective to perform the etching treatment before the final annealing of the brazing sheet, or after the completion of the rolling and annealing process of the brazing sheet. It is.

[Effect]

In this way, the amount of alkaline etching is 0.02 to 5 g/m.
The reason why it is set as 2 is that if it is less than 0.02 g/m2, there is no effect of improving brazability, and if it exceeds 5 g/m2, the shedding of 81 particles becomes noticeable, the surface unevenness increases, and the brazability is deteriorated. This is because it decreases. And alkaline etching is 20~
It may be treated with a NaOH aqueous solution having a concentration of 1 to 5% at a temperature of 70°C.

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 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 a temperature of 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. Note that if the annealing is performed in an annealing atmosphere in which the O2 and H20 concentrations are kept low, the increase in film thickness can be minimized. This process is suitable for manufacturing zero 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 is suitable for producing H material which is subjected to cold rolling after annealing.

〔Example〕

Next, examples of the present invention will be described.

<Example 1> When manufacturing a brazing sheet in which JIS 4004 alloy brazing material was clad on both sides of a JIS 3003 alloy core material with a thickness of 15%, the thickness of the cladding material was set to 5 mm by hot rolling, and then After cold rolling to a thickness of 0.6 mm, alkali cleaning was performed under the conditions shown in Table 1. Thereafter, final annealing was performed at 360° C. for 2 hours in an inert gas to obtain an O material with a thickness of 0.6 mm. Note that the neutralization treatment after the alkaline cleaning was performed in the following step. That is, (room temperature x 30 seconds) (60°C x 30 seconds) (90'C
The weight before and after washing was measured to calculate the amount of etching, and the compressive strength 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. Next, as shown in Figure 2, these cup molded products (1) are stacked alternately to form three hollow structures (
3) into the shape of a hollow container that communicates with the exhaust port (2), and the pressure tester connection port (5) is attached to the exhaust port (2) of the cup molded product (1) at the upper end. The containers were integrated by vacuum brazing at a temperature of 595° C. in a vacuum of 5XIO” Torr, and five integrated hollow containers (hereinafter referred to as cores) were produced for each etching treatment condition.

These cores were then visually inspected for solder breakage on the outside, and if one or more cores had breakage of the solder, it was determined that there was a breakage of the solder, and in how many of the 5 cores did the breakage occur? was written.

In addition, water was introduced through the connection port (5), 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 43 kgG/at or higher, and they exhibited excellent brazing properties without any brazing breakage.

On the other hand, cores made by Comparative Method No. 056 with a small amount of etching, cores made by Comparative Method No. 008 without nitric acid neutralization, and cores made by Comparative Method No. 49 without alkaline cleaning were 38~
It only had a pressure resistance of about 39 kgG/ci, and wax breakage also occurred. Also, comparative method N has a large amount of etching.
Samples 0 and 7 had high pressure resistance, but had noticeable solder breakage.

<Example 2> The same clad material as in Example 1 was hot rolled to a thickness of 5 m.
A brazing sheet was manufactured in the following order: a+ binding, further cold rolling to a thickness of 0.61, and final annealing at 360°C x 2 hours, and at the final stage, cleaning was performed under the conditions shown in Table 2. The etching amount was calculated in the same manner as in Example 1, and the pressure resistance test and occurrence of solder breakage were also investigated, and the results are also listed in Table 2.

As can be seen from Table 2, in this case, in order to obtain the same amount of etching as in Example 1, it is generally necessary to take a longer etching time; It has a pressure resistance of above 100%, and there is no occurrence of solder breakage. On the other hand, the core produced by the comparative method had inferior compressive strength and noticeable solder breakage.

〔Effect of the invention〕

As described above, according to the present invention, by subjecting the brazing material to moderate alkali etching combined with neutralization treatment, the reliability of the brazing metal part is improved, such as improving the pressure resistance of the joint members and suppressing the occurrence of solder breakage. can be achieved. According to the present invention, it is possible to stabilize brazing performance even when there is a slight decrease in brazing conditions such as fluctuations in the degree of vacuum in the brazing part, variations in brazing temperature, or changes in the clearance of joining parts. becomes.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the manufacturing process of the plate material of the tron cup type evaporator, Figure 2 is an explanatory diagram showing the manufacturing process of the fin material of the tron cup type evaporator, and Figure 3 (a) and (b) are Showing the cup molded product for brazing test, (a) is a plan view, (b) is YY of (a)
A line sectional view, and FIG. 4 is a side sectional view of a hollow container for pressure resistance testing in which a cup molded product is combined. 1 - Cup molded product 2 Exhaust port 3 Hollow structure 4 - Cup molded product without holes 5 - Pressure tester connection port ↑← ↑ ← ↑ ←〈

Claims (3)

[Claims] (1) In the production of aluminum brazing sheets clad with Al-Si-Mg alloy as a brazing material,
A method for producing a brazing sheet for vacuum brazing, characterized in that the surface thereof is etched with an alkaline solution at a rate of 0.02 to 5 g/m^2, and then neutralized. (2) The method for producing a brazing sheet for vacuum 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 vacuum brazing according to claim (1), wherein the etching treatment is performed after the rolling and annealing process of the brazing sheet is completed.