JPH0642997B2 - Method for manufacturing thin aluminum plate for brazing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an aluminum thin plate for fins, which has excellent high temperature buckling resistance and is suitable for non-corrosive flux brazing and carrier gas brazing.

(Prior Art) Conventionally, a heat exchanger made of an aluminum alloy such as a condenser for an automobile cooler and an evaporator is composed of an extruded multi-hole tube and a corrugated fin.

Generally, such an extruded multi-hole tube has a JIS A105
0 (99.5 wt% or more of A (hereinafter wt% is simply abbreviated as%)) or A3003 (A-0.15% Cu-1.1% M
n) Alloy is used and A3003 is used for corrugated fins.
Alternatively, A3203 (A-1.1% Mn) is used as the core material,
A-Si alloy, for example, A4343 (A
-7.5% Si) and A4004 (A-10% Si-1.5
A so-called brazing sheet, in which% Mg) is clad, is used.

The heat exchanger using these brazing sheets is generally manufactured by a so-called brazing method in which the extruded multi-hole tube and the brazing sheet are heated to 590 to 620 ° C. for several minutes to be joined.

By the way, in the case of the brazing sheet used for the non-corrosive flux brazing method or the carrier gas brazing method among the brazing methods, Zn is added to the A3003 alloy as the core material (or skin material) of the corrugated fin, and the effect of the sacrificial anode fin is added. It is necessary to prevent corrosion of the extruded tube material. However, when Zn is added, the sacrificial anode effect is improved but the high temperature buckling resistance is lowered.

Further, in the carrier gas brazing method, if the skin material diffuses significantly, Zn in the core material evaporates, the amount of residual Zn in the fin decreases, and the sacrificial anode effect may not be expected sufficiently.

On the other hand, as a method of manufacturing a fin material for manufacturing an aluminum alloy heat exchanger by such a brazing method, Mn,
A method of manufacturing a fin material in which a skin material is clad with a core material of an aluminum alloy containing a predetermined amount of Mg, Zr, or the like has been recently proposed (Japanese Patent Laid-Open No. 60-215729).

(Problems to be Solved by the Invention) In the method disclosed in the above-mentioned JP-A-60-215729, the buckling resistance is improved by adding Zr and one annealing is performed as an intermediate treatment of a predetermined cold rolling. I'm doing it. However, the high temperature buckling resistance of the brazing sheet is
In recent years, the required level has become stricter as the fin material has become thinner, and such a method cannot satisfy the required level.

Further, in the non-corrosive flux brazing method or the carrier gas brazing method, the conventional brazing sheet in which Zn is added to the core material as described above has low high temperature buckling resistance and cannot satisfy the requirement for thinning of fin material. It was

Therefore, it is an object of the present invention to provide a method for producing an aluminum thin plate for brazing which has a high resistance to buckling at high temperature even if it is thinned and exhibits an excellent sacrificial anode effect for an extruded multi-hole tube.

A further object of the present invention is to provide a method for producing an aluminum thin plate for brazing, which is particularly suitable for the non-corrosive flux brazing method and the carrier gas brazing method.

(Means for Solving Problems) As a result of various studies conducted by the present inventors to solve the above problems, as a result, an aluminum alloy containing a predetermined amount of Mn and Zn and controlling the amounts of Fe and Si was used as a core material. When processing a laminated material coated with an A-Si-based or A-Si-Mg-based brazing filler metal as a skin material, annealing is performed immediately after the hot rolling is finished, or after cold rolling is performed. In order to improve the high temperature buckling resistance, it is necessary to perform two intermediate annealings, and further, the cold rolling rate between those intermediate annealings and the final cold rolling rate after the final intermediate annealing are also measured. It was found to be important and a detailed examination was conducted. As a result, they have found that it is necessary to control the rolling rate under certain conditions in the cold rolling and annealing steps. The present invention has been accomplished based on this finding.

That is, the present invention is Mn0.6 ~ 2.0%, Fe0.3% or less, S
i 0.6% or less, Zn 0.5 to 2.0%, balance A (or more, wt
%) Aluminum alloy as a core material, and A-Si
When hot-rolling and cold-rolling the composite material using the Al-based or A-Si-Mg-based brazing material as the skin material, (a) to the heat-treated or homogenized composite material, Performing intermediate annealing twice in the process after hot rolling, (c) From the second to last intermediate annealing to the final intermediate annealing, the cold rolling rate R ₁ (%) and the final intermediate annealing to the final sheet thickness. Cold rolling rate R ₂ (%) of 10 ≦ R ₁ ≦ 90, 10 ≦ R ₂ ≦ 60, 30 ≦ R ₁ + R ₂ and R ₁ −R ₂ ≦ 60 are cold rolled. The present invention provides a method for manufacturing an aluminum thin plate for brazing, which is characterized by the above.

Next, the action of each component in the aluminum alloy composition used for the core material of the fin material of the present invention will be described.

Mn not only improves the strength of the alloy, but also A-Mn-
Fe or A-Mn-Si-based fine precipitates are formed, the recrystallized grains are coarsened, and the high temperature buckling resistance during high temperature heating during brazing is improved. That amount
If it is less than 0.6%, its effect is small, and if it exceeds 2.0%, a large crystallized substance is likely to be formed, resulting in poor moldability as a fin material.

Fe is A-Mn-Fe due to coexistence with A and Mn.
System precipitates are formed, the recrystallized grains are coarsened, and the high temperature buckling resistance during high temperature heating during brazing is improved.
If it exceeds%, the amount of crystallized substances increases and acts as a nucleus site for recrystallization, so that the recrystallized grains become finer and conversely the high temperature buckling resistance deteriorates.

Si has a function of producing fine precipitates of A-Mn-Si system, coarsening recrystallized grains and improving high temperature buckling resistance during high temperature heating during brazing, but if less than 0.05%, If the effect is small and exceeds 0.6%, the recrystallized grains become finer due to the effect of crystallized substances, and the high temperature buckling resistance deteriorates. Zn
Has a function of making the potential of the fin material base and preventing pitting corrosion of the working fluid passage such as a tube by the sacrificial anode effect, but if it is less than 0.5%, its effect is small, and if it exceeds 2.0%, self-corrosion becomes Brazeability is reduced.

In the present invention, the laminated material is subjected to a homogenizing treatment. This homogenizing treatment is performed by homogenizing a core material having the above composition and then clad an A-Si-based or A-Si-Mg-based skin material, or by cladding the skin material and then performing a homogenization treatment. It is carried out. If the homogenization temperature exceeds 580 ° C, the recrystallized grain size during brazing becomes fine and the high temperature buckling resistance deteriorates. Therefore, the upper limit is set to 580 ° C. When the skin material is clad and then homogenized, the melting point of the skin material (577 ° C. for A-Si system, A-Si-Mg
The temperature should be 555 ° C or less in the system. Further, in the present invention, the required characteristics can be sufficiently satisfied only by clad the skin material on the core material without performing the homogenization treatment.

Next, hot rolling is performed by heating to a temperature below the melting point of the skin material, but there is no particular requirement for this condition.
Further, when the homogenizing treatment is performed after the skin material is clad, the hot rolling may be performed immediately after the homogenizing treatment.

Immediate annealing is performed after the hot rolling is completed or after cold rolling is performed, but two intermediate annealings are required to improve the high temperature buckling resistance.

Further, the cold rolling rate during the intermediate annealing and the final cold rolling rate are also important, and cold rolling and annealing are performed under the following conditions. When R ₁ is the cold rolling rate (%) from the _second to final annealing to the final annealing and R ₂ is the cold rolling rate (%) from the final annealing to the final plate thickness, 10 ≦ R ₁ ≦ 90 and 10 ≦ R ₂ ≦ 60 and 30 ≦ R ₁ + R ₂ and R ₁ −R
_This is a step of performing intermediate annealing at a plate thickness that satisfies the condition of ₂ ≤ 60. FIG. 1 shows the range of the cold rolling rate regulated by R ₁ and R ₂ .

The temperature and time of the intermediate annealing are not particularly limited, but usually 300
It is 0.5 to 6 hours at -400 degreeC.

Generally, the cause of high temperature buckling of aluminum alloy fin material is considered to be that molten skin material diffuses through grain boundaries of the core material or through sub-boundary, and therefore, in order to prevent diffusion, high temperature of brazing is used. When heated, it recrystallizes quickly (removes the sub-boundary),
Moreover, it is necessary that the recrystallized grains are large (the grain boundary area is small).

According to the research conducted by the present inventors, the largest cause of delay in recrystallization during heating of brazing at high temperature is M
Solid solution elements such as n and Si precipitate and compete with recrystallization. To prevent this, cold rolling and intermediate annealing are repeated after hot rolling is completed, and precipitates are sufficiently precipitated in the matrix in advance. By doing so, it was proved effective to reduce the amounts of solute Mn and Si. These fine precipitates existing before heating at a high temperature delay recrystallization to some extent, but usually do not cause a problem, but rather have a function of coarsening the grain size and improve the high temperature buckling resistance. In order to obtain such an effect, one intermediate annealing is not enough,
Two intermediate anneals are required.

Further, if the cold rolling ratio (R ₁ ) from the penultimate intermediate annealing to the final intermediate annealing is less than 10%, precipitation during the final annealing is insufficient, recrystallization does not occur, and high temperature heating of brazing is performed. In that case, the sub-boundary tends to remain. On the other hand, if it exceeds 90%, recrystallization during the final annealing is extremely fast and the size of the precipitate is also extremely fine, which hinders the disappearance of the sub-boundary during brazing and deteriorates the high temperature buckling resistance.

Further, when the final cold rolling rate (R ₂ ) is less than 10%, the workability is small, the recrystallization during brazing is delayed, the sub-boundary remains, and the high temperature buckling resistance deteriorates. On the other hand, when R ₂ exceeds 60%, the recrystallized grain size becomes fine, the high temperature buckling resistance deteriorates, and the formability as a fin material deteriorates.

Therefore, the conditions of 10 ≦ R ₁ ≦ 90 and 10 ≦ R ₂ ≦ 60 are required. Further, in the region of 10 ≦ R ₂ ≦ 20, the high temperature buckling resistance may be deteriorated even if 10 ≦ R ₁ ≦ 90, and the conditions of 30 ≦ R ₁ + R ₂ and R ₁ −R ₂ ≦ 60 are also: Need to add.

A4 is a specific example of the A-Si-based or A-Si-Mg-based brazing filler metal used as the skin material in the present invention.
343 (A-7.5% Si) and Zn added with about 1% thereof, and A4004 (A-10% Si-1.5).
% Mg).

The final thickness of the fin material obtained by the present invention is usually 0.1.
It is 0 to 0.20 mm.

(Example) Next, the present invention will be described in more detail based on examples.

Examples Ingots having compositions A to E shown in Table 1 below (304 mm^t× 70
0 mm^w× 1600 mm ) Is homogenized and then chamfered (some are
Only chamfering without homogenization), A equivalent to A4343
A skin material of -7.5% Si is clad on both sides with a cladding rate of 12%.
Rad Then, as shown in Table 2, reheating, hot working
0.12mm fin braze that is rolled, cold rolled and annealed
Was prepared. Detailed processing method is shown in Table 2.
You Also, plot this processing method No. 3 to 15 in Fig. 1.
did. The numbers in the figure indicate the processing method No., and the range surrounded by a line
Indicates the range of the conditions of the present invention.

The fin material obtained as described above was tested for high temperature buckling resistance and corrosion resistance. The results are shown in Table 3.

(1) High temperature buckling resistance test Processed by processing methods 3 to 15 using alloys A to E as core materials
22 mm wide and 6 long from the brazing sheet for fins obtained from
A 0 mm sample (21) was made and this was shown in Fig. 2 (a).
Use the fixture (23) on the base (22) as shown in (b).
t × 22^wX50 Cantilevered and held at 610 ° C for 10
Heat in air for minutes. After heating as shown in Fig. 2 (c)
The high temperature buckling resistance is evaluated by the amount of the lower amount. In this evaluation method
And the amount of droop is 15 mm or less, the actual condenser
Make sure there is no problem when brazing
confirmed.

Therefore, a drooping amount of 15 mm or less is determined to be acceptable.

(2) Pitting corrosion resistance test of fin material As shown in FIG. 3, fin material (31) is corrugated.
Then on both sides 0.8^t× 20^w× 100 A300
Filter the 3 plates (32) with a non-corrosive flux brazing method.
I told you

This test piece was sprayed with salt water (according to JIS Z2371) 40
A 00 hr test was performed to examine the pitting corrosion generated on the A3003 plate.

(Effects of the Invention) According to the present invention, the high temperature buckling resistance can be further improved as compared with the conventional one, and the fin material can be made thinner.

Therefore, according to the method of the present invention, an aluminum thin plate for fins suitable for non-corrosive flux brazing and carrier gas brazing can be manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory view of the range of the cold rolling rate taken in the method of the present invention, and FIGS. 2 (a), (b), and (c) are explanatory views of the test method for the buckling resistance of the fin material. FIG. 3 is an explanatory diagram of a pitting corrosion resistance test for fin materials.

Claims (1)

[Claims] 1. Mn 0.6 to 2.0%, Fe 0.3% or less, Si 0.6
%, Zn 0.5-2.0%, balance A (or more, wt%) as the core material, and A-Si or A-Si-Mg based brazing material as the skin material. In rolling and cold rolling, (a) the heat-treated or homogenized composite material is subjected to (b) two intermediate annealings in the steps after hot rolling, and (c) 2 from the end. th rolling reduction R ₁ from the intermediate annealing to final intermediate annealing _(%) and the cold-rolling reduction from the final intermediate annealing to a final sheet thickness R _{2 (%)} is 10 ≦ R ₁ ≦ 90,10 ≦ A method for producing an aluminum thin plate for brazing, characterized in that cold rolling is performed so as to satisfy the relationships of R ₂ ≦ 60, 30 ≦ R ₁ + R ₂ and R ₁ −R ₂ ≦ 60.