JP2685926B2 - A Blazing sheet for refrigerant passage of heat exchanger manufactured by A - Google Patents

Description

The present invention relates to a brazing sheet for a refrigerant passage of a heat exchanger made of Al, in which a sacrificial anode material having a lower potential than the core material is provided on the inner side (refrigerant side). It is clad as a sacrificial material to prevent the occurrence of pitting corrosion inside the refrigerant passage.

[Conventional technology]

Conventionally, Al heat exchangers such as radiators and heater cores have been manufactured by flux brazing using a fluoride-based non-corrosive flux. Radiator is first
As shown in Figures (a) and (b), fins (2) are arranged between tubes (1) through which the refrigerant passes, and header plates (3) are attached to both ends of the tubes (1) to assemble the core (4). After brazing, the resin tanks (5) and (5 ') are attached to the header plate (3) through the packing (6), and the fins are JIS3003 alloy with Zn of 1.5 wt% (hereinafter wt%).
%) Is used for the tube, and a JIS4343 brazing filler metal is clad on the outside (atmosphere side) of the core material made of JIS3003 alloy, and JIS7072 is used on the inside (refrigerant side). Thickness 0.3 clad with alloy as sacrificial material
~ 0.4mm brazing sheet (cladding ratio of inner and outer layers is 5
~ 10%) and the same brazing sheet (plate thickness 1.0 to 1.8 mm) as the tube is used for the header plate.

In such a radiator, the following measures are taken to prevent the occurrence of pitting corrosion on the refrigerant side. In other words, the tube thickness is as thin as 0.3 to 0.4 mm, and JIS 3003 alloy alone
l Since pitting corrosion peculiar to alloys may occur and liquid leakage may occur early, as shown in Fig. 2 (a), inside the core material made of JIS3003 alloy, JIS7072 alloy (potentially lower than this) A
The clad is a sacrificial material (1-Zn alloy).

The sacrificial material made of JIS7072 alloy and the core material made of JIS3003 alloy are exposed to an atmosphere of about 600 ° C during the brazing heating, whereby the Zn in the JIS7072 alloy is JIS3003 alloy as shown in Fig. 2 (b). Side surface, Zn concentration on the surface is 0.4 to 0.8%, and diffusion depth from the inner surface is 80 to 150 μm.
n shows the diffusion pattern. Due to this preferential corrosion of the Zn diffusion layer, the pitting corrosion generated from the refrigerant side does not grow deeply but takes a shallow and wide form of corrosion and exhibits long-term pitting corrosion resistance.

Al-Zn alloy itself has a characteristic that it takes a shallow and shallow corrosion form (face corrosion), and due to the potential difference between the core material and the Al-Zn alloy sacrificial material, the sacrificial material layer is preferentially corroded even after the core material is exposed,
Prevents corrosion of core material. Further, Zn diffused into the core material also causes pitting corrosion on the surface of the core material and suppresses the occurrence of pitting corrosion. As such a sacrificial material, Al-Zn, Al-Zn-Mg, Al-Mn-Zn, Al
-Mn-Zn-Mg alloy is used.

[Problems to be solved by the invention]

The Zn diffusion pattern of the radiator tube material is
The Zn concentration on the surface of the sacrificial material may decrease and the diffusion depth may become deep due to changes in the brazing conditions. Therefore, a sufficient potential difference from the core material cannot be ensured, and pitting corrosion remarkably decreases.

Further, when the plate thickness of the tube material becomes thinner, when the same brazing heating as in the conventional case is performed, not only Zn diffusion progresses due to excessive heating as described above, but also the ratio of the Zn diffusion layer to the tube material plate thickness. And the reduction of the plate thickness due to corrosion has a great effect on not only the corrosion resistance but also the structural strength.

[Means for solving the problem]

The present invention, as a result of various studies in view of this, suppresses Zn diffusion from the Al-Zn alloy used as a sacrificial material for the tube material to the core material, and is also excellent due to variation in brazing heating conditions and reduction in plate thickness. This is a brazing sheet for Al heat exchanger refrigerant passage showing pitting corrosion resistance.

That is, one of the present invention is to clad an Al alloy brazing material on the outside (atmosphere side) of the core material made of Al alloy and to the inside (refrigerant side)
In a brazing sheet clad with an Al alloy sacrificial material, the sacrificial material contains Zn 0.5 to 5.0%, Zr 0.03 to 0.3%, Fe 0.4% or less, Si 0.6% or less, and the balance Al and unavoidable impurities An alloy is used, and an Al alloy having a higher potential than the sacrificial material is used as the core material. The recrystallized grain size of the sacrificial material after brazing may be 100 μm or more.

Another aspect of the present invention is a brazing sheet in which an Al alloy brazing material is clad on the outer side (atmosphere side) of a core material made of an Al alloy and an Al alloy sacrificial material is clad on the inner side (refrigerant side). Zn0.5-5.0%, Zr0.03-0.3%, Fe0.4
% Or less, Si 0.6% or less, Mn0.05 to 1.5%, Cr0.03
~ 0.3%, Ti0.03 ~ 0.3%, V0.03 ~ 0.3% in the range of any one or more, using the balance Al and unavoidable impurities alloy, the core material from the sacrificial material This is characterized by using an Al alloy having a noble potential, and the recrystallized grain size of the sacrificial material after brazing may be 100 μm or more.

(Operation)

The reason for limiting the components of the sacrificial material containing Zn in the present invention as described above is as follows.

That is, the present invention suppresses Zn diffusion to the core material side during brazing heating, significantly improves pitting corrosion resistance, and coarsens the recrystallized grain size during brazing heating of the sacrificial material, Zn
This is an increase in the diffusion suppressing effect.

However, the reason for limiting the Zn content of the sacrificial material to 0.5 to 5.0% is that the electric potential of the sacrificial material is base and acts as a sacrificial anode. If it is less than 0.5%, there is no effect, and if it exceeds 5.0%. This is because the effect is saturated and the melting point of the sacrificial material is lowered. Also, the Zr content is limited to 0.03-0.3%,
This is because the recrystallized grain size is coarse and Zn diffusion to the core side is suppressed and the strength is improved. If it is less than 0.03%, there is no effect, and if it exceeds 0.3%, the workability is deteriorated.
The Fe content is limited to 0.4% or less in order to make the recrystallized grain size coarse and suppress Zn diffusion to the core material side.
This is because if the content exceeds 100%, the recrystallized grain size becomes finer and the Zn diffusion suppressing effect decreases. The Si content is limited to 0.6% or less because the recrystallized grain size becomes coarse when Si is added,
It suppresses Zn diffusion and improves the strength of the sacrificial material.
This is because if it exceeds 6%, the melting point of the sacrificial material is lowered.

Next, Mn, Cr, Ti, and V were added to the sacrificial material as Mn 0.05 to 1.5% and Cr 0.03 to 0.
Addition of any one kind or two kinds or more within the range of 3%, Ti0.03 to 0.3%, and V0.03 to 0.3% makes the recrystallized grains coarse and suppresses the diffusion effect of Zn. At the same time, it is because the strength of the sacrificial material is improved. If it is less than the lower limit, there is no effect, and if it exceeds the upper limit, the workability is deteriorated.

When a brazing sheet is manufactured by an ordinary method using the alloy having the above composition as a sacrificial material, the recrystallized grain size is about 50 to 200 μm after brazing and heating, but in the manufacturing process, the homogenization treatment temperature and the final cold rolling after intermediate annealing are performed. By controlling the rate, the recrystallized grain size after brazing and heating is 100 μm
With the above, the effect of suppressing Zn diffusion can be further improved.

As the core material, there is no problem if an Al alloy having a higher potential than the sacrificial material is used, for example, Al-Mn-based JIS3003 alloy, Al-Mn
-Mg-based JIS3004 alloy, Al-Mg-Si-based JIS6951 alloy, or alloys obtained by adding Cu to these alloys are used. The outer side (atmosphere side) of the core material is clad with an Al-Si based Al alloy brazing material to form a three-layer structure. The clad ratio of the sacrificial material and the outer brazing material is 5 to 15%, and is set to be high when the plate thickness is thin and low when the plate thickness is opposite, and the thickness is preferably 10 μm or more.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Example 1 An alloy having the composition shown in Table 1 was used as a sacrificial material, and a soaking treatment was performed at 550 ° C. after melt casting by a conventional method. This is 500 ℃
After being hot-rolled in, a plate having a thickness of 2.5 mm was obtained by cold rolling.

On the other hand, a 45 mm thick JIS3003 alloy ingot is used for the core material, an Al alloy brazing material made of a 2.5 mm thick JIS4343 alloy on one surface of the core material, the other surface of the sacrificial material is clad, and hot rolled, A brazing sheet having a thickness of 0.4 mm, a brazing material clad ratio of 5% and a sacrificial material clad ratio of 5% was produced by intermediate annealing and cold rolling.

This is brazed and heated at 600 ° C for 10 minutes, and the maximum Zn concentration on the surface of the sacrificial material and the Zn diffusion depth from the surface of the sacrificial material are measured by cross-section EPMA.
It was determined by line analysis, and the recrystallized grain size of the sacrificial material after heating was measured. Also, it was immersed in tap water containing 10 ppm of Cu ²⁺ ions for 3 months, and subjected to a cycle corrosion test at 80 ° C for 8 hours and room temperature for 16 hours. It was measured by the method. Table 1 shows the results.

As is clear from Table 1, all the examples of the present invention have a high Zn concentration on the surface of the sacrificial material and a shallow Zn diffusion depth, and exhibit excellent pitting corrosion resistance. On the other hand, in the comparative example in which the composition of the sacrificial material deviates, the surface Zn concentration is low or the Zn diffusion depth is deep, resulting in poor pitting corrosion resistance.

Example 2 Using Example Nos. 4 and 10 of the present invention in Example 1, the sacrificial material after brazing and heating was changed by changing the conditions for homogenizing the sacrificial material and the cold rolling rate after intermediate annealing of the clad material. The recrystallized grain size was changed.

The same brazing heating as in Example 1 was performed on this, and the Zn diffusion state, the pit depth by the corrosion test, and the recrystallized grain size of the sacrificial material were measured in the same manner as in Example 1. Table 2 shows the results.

As is clear from Table 2, all of the examples of the present invention in which the recrystallized grain size of the sacrificial material after brazing and heating was 100 μm or more, suppressed Zn diffusion to the core material side and exhibited excellent pitting corrosion resistance. I understand.

The recrystallized grain size of the core material made of JIS 3003 alloy used in the examples after brazing and heating was 50 to 150 μm, and the potentials of the core material and the sacrificial material were 5% NaCl solution and a saturated calomel electrode as a reference. , The core material was -720 mV, and the sacrificial material was -730 to -900 mV.

〔The invention's effect〕

As described above, according to the present invention, it is possible to remarkably suppress Zn diffusion from the sacrificial material to the core material, prevent deterioration of pitting corrosion resistance due to decrease of surface Zn concentration under severe brazing conditions, and brazing sheet. Since Zn diffusion can be suppressed even when the thickness is reduced, high Zn material is used as a sacrificial material,
By thinly clad the sacrificial material, it is possible to reduce the ratio of the thickness of the Zn diffusion layer to the total plate thickness, and it is possible to obtain long-term pitting corrosion resistance. Is.

[Brief description of the drawings]

1 (a) and (b) show an example of a radiator, (a) is a front view, (b) is an enlarged sectional view taken along the line AA in (a), and FIG. 2 (a) (b). ) Shows an example of the Zn diffusion state before and after brazing heating of the tube material.
FIG. 3 is an explanatory diagram showing a Zn concentration on the surface of the sacrificial material before heating for brazing, and (b) a Zn diffusion depth from the surface of the sacrificial material after heating for brazing. 1 ... Tube, 2 ... Fin 3 ... Header plate, 4 ... Core 5, 5 '... Resin tank, 6 ... Packing

Claims (4)

(57) [Claims] 1. Al on the outside (atmosphere side) of a core material made of Al alloy
A brazing sheet in which an alloy brazing material is clad and an Al alloy sacrificial material is clad on the inside (refrigerant side), the sacrificial material is Zn 0.5 to 5.0 wt%, Zr 0.03 to 0.3 wt%, Fe 0.4 wt% or less, Si
A brazing sheet for a refrigerant passage of an Al heat exchanger characterized by using an alloy containing 0.6 wt% or less and the balance Al and unavoidable impurities, and using an Al alloy having a higher potential than a sacrificial material as a core material. . 2. The recrystallized grain size of the sacrificial material after brazing is 100 μm.
The brazing sheet for a refrigerant passage of the Al heat exchanger according to claim 1, wherein the brazing sheet has a length of at least m. 3. Al outside the core material made of Al alloy (atmosphere side)
A brazing sheet in which an alloy brazing material is clad and an Al alloy sacrificial material is clad on the inside (refrigerant side), the sacrificial material is Zn 0.5 to 5.0 wt%, Zr 0.03 to 0.3 wt%, Fe 0.4 wt% or less, Si
0.6wt% or less, Mn0.05-1.5wt%, Cr0.03-0.3
wt%, Ti 0.03 to 0.3 wt%, V 0.03 to 0.3 wt%, and any one or more of them are used, and the balance is Al and unavoidable impurities. A brazing sheet for a refrigerant passage of a heat exchanger made of Al, which is made of an Al alloy having a higher potential. 4. The recrystallized grain size of the sacrificial material after brazing is 100 μm.
The brazing sheet for a refrigerant passage of the Al heat exchanger according to claim 3, wherein the brazing sheet has a length of at least m.