JPS63153251A - Manufacture of thin aluminum sheet for brazing - Google Patents

Abstract

PURPOSE:To manufacture the titled thin Al sheet having superior buckling resistance at high temp. and a significant sacrificial anode effect by hot rolling a clad material consisting of an Al alloy contg. specified percentages of Mn, Fe, Si, Cu and Zn and an Al-Si brazing filler metal and by subjecting the resulting hot rolled sheet to cold rolling, process annealing and cold rolling at a specified draft. CONSTITUTION:An Al alloy consisting of, by weight, 0.6-2% Mn, <=0.3% Fe, <=0.6% Si, 0.02-0.2% Cu, 0.5-2.0% Zn and the balance Al as a core material is clad with an Al-Si or Al-Si-Mg brazing filler metal as a cladding material to obtain a clad material. This clad material is homogenized, heated to a temp. below the m.p. of the cladding material and hot rolled. The resulting hot rolled sheet is cold rolled at about 10-90% draft, process-annealed by heating at >=about 300 deg.C for about 0.5-4hr and cold rolled to about 0.10-0.20mm final thickness at 30-70% draft. Thus, a thin Al sheet for fins suitable for brazing with a noncorrosive flux or a carrier gas is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a thin aluminum plate for pre-zincing, which has excellent high-temperature buckling resistance and is suitable for non-corrosive flux brazing and carrier gas flash brazing.

(Prior Art) Conventionally, heat exchangers made of aluminum alloy, such as condensers for automobile coolers and evaporators, are composed of extruded multi-hole tubes and corrugated fins.

Generally, JISA I is used for such extruded multi-hole tubes.
O50 (Ai greater than 99.5 wt% (wt% is abbreviated as %)) and A3003 (Ai - 0.15% C
A, 3003 or A3203 (AM-1, 1% Mn) alloy is used for corrugated fins.
%Mn) as the core material, and A or -Si alloy,
For example, A4343 (A or -7.5%Si) or A400
4 (AM-10%5i-1.5%Mg) or a so-called plating sheet is used.

The production of heat exchangers using these pre-zinc sheets is generally carried out by the so-called pre-sink method, which is a method in which the extruded multi-hole tube and the pre-zinc sheet are heated to 590 to 620° C. for several minutes and bonded together.

By the way, in the case of a brazing sheet used for the non-corrosive black spraying method or carrier gas brazing method, Zn is added to A3003 alloy as the core material (or skin material) of the corrugated fin, and the sacrificial anode fin is used as a sacrificial anode fin. There is a need to provide corrosion protection to extruded tubing. However, when Zn is added, although the sacrificial anode effect is improved, the high temperature buckling resistance is reduced.

In addition, in the carrier gas brazing method, if the diffusion of the skin material is large, Zn in the core material will evaporate, and the amount of Zn remaining in the fins will decrease, making it impossible to expect a sufficient sacrificial anode effect.

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

(Problems to be Solved by the Invention) The method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 60-215729 improves the buckling resistance by incorporating Zr and performing one annealing as an intermediate treatment of a predetermined cold rolling process. I am doing it for the sake of doing it. However, as fin materials become thinner, there is a need to increase the strength of the material during molding.
It is difficult to satisfy this requirement with a final cold rolling reduction of about 1.0%.

In addition, in the non-corrosive flux brazing method or carrier gas brazing method, the conventional brazing sheet with Zn added to the core material has low high temperature buckling resistance and cannot satisfy the requirements for thinning the fin material. There wasn't.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a thin aluminum plate for brazing, which has high high temperature buckling resistance even when the thickness is reduced, and exhibits an excellent sacrificial anode effect for extruded multi-hole tubes.

A further object of the invention is to provide a method for producing aluminum sheet for brazing which is particularly suitable for non-corrosive black spraying and carrier gas brazing methods.

(Means for Solving the Problems) As a result of various studies in order to solve the above problems, the present inventors have developed an aluminum alloy containing predetermined amounts of Mn, Zn, and Cu and with controlled amounts of Fe and Si. As the core material, A-Si
The inventors have discovered that the object can be achieved by subjecting a laminated material coated with AJL-Si-Mg brazing filler metal or AJL-Si-Mg brazing filler metal as a skin material to a predetermined process, and based on this knowledge, the present invention has been completed.

That is, the present invention provides M n 0.6 to 21 F e 0
．． 3% or less, Si 0.6% or less, a Cu Q, 02~
The core material is an aluminum alloy consisting of 0-2%1, Zn0.5-2.0%, and the balance Al.
M-S 1- After hot rolling and cold rolling, intermediate annealing is performed on the laminated material with Mg-based brazing filler metal as the skin material, and then cold rolling is performed at a rolling rate of 30 to 70% to obtain the final plate thickness. The present invention provides a method for manufacturing a thin aluminum plate for brazing, which is characterized by the following.

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

Mn improves the strength of the alloy and also improves the strength of the AJI-M
It produces n-Fe or Al-Mn-Si-based fine precipitates, coarsens recrystallized grains, and has the function of improving high-temperature buckling resistance during high-temperature heating during brazing. If the amount is less than 0.6%, the effect is small, 2.0%
If it is added in excess of this amount, large pieces are likely to form, resulting in poor moldability as a fin material.

Fe is A l −M n− due to the coexistence with A sentence and Mn.
It produces Fe-based precipitates, coarsens recrystallized grains, and improves high-temperature buckling resistance during high-temperature heating during brazing, or
If it exceeds 0.3%, the amount of crystallized substances increases and acts as a nucleation site for recrystallization, resulting in finer recrystallized grains and, conversely, deteriorating high-temperature buckling resistance.

Si forms fine Al-Fljn-Si precipitates,
0.05%, which has the effect of coarsening recrystallized grains and improving high-temperature buckling resistance during high-temperature heating during brazing.
If the content is less than 0.6%, the effect will be small, and if it exceeds 0.6%, the recrystallized grains will become finer due to the effect of crystallized substances, deteriorating high-temperature buckling resistance.

Zn lowers the potential of the fin material and has a sacrificial anode effect to prevent pitting corrosion in working fluid passages such as tubes.
If it is less than 5%, the effect is small, and if it exceeds 2.0%, self-corrosion increases and brazability decreases.

Since Cu affects the potential of the fin material and reduces the sacrificial anode effect, it has been conventionally considered that addition of Cu is an undesirable element. However, as a result of various studies, the present inventors found that when the amount of Fe added is limited to 0.3% or less, the addition of Cu has an effective effect in improving high-temperature buckling resistance. . this is.

When the amount of Fe added is small, Cu becomes AJI-Fe at the time of ingot.
-The amount of Cu-based products is small, and most of them are dissolved in the matrix, which is removed by A during the subsequent heat treatment process.
Since it precipitates as an n-Cu-M n-based precipitate,
This is believed to be because the amount of solid solution Mn is reduced, recrystallization proceeds quickly during high-temperature heating, and high-temperature buckling resistance is improved. To achieve this effect, 0.02%
More than 0.2% of Cu is required, and if it exceeds 0.2%, the potential of the fin becomes noble and the sacrificial anode effect disappears.

In addition, in the present invention, other elements (Mg, Cr, Ti
, Zr, Ca, Li, etc.), if it is less than 0.05%, the effect of the present invention will be affected! not give.

In the method of the present invention, first, the combined material of the core material and the skin material is homogenized. This homogenization treatment is performed after homogenizing the core material having the above composition.
- It is carried out by cladding with Mg-based skin material, or by homogenizing the skin material after cladding. If the homogenization temperature exceeds 580°C, the recrystallized grain size during brazing becomes finer and the high temperature buckling resistance deteriorates, so the upper limit is set to 580°C.
Set at 0℃. In addition, when homogenizing the skin material after cladding, the melting point of the skin material (577
℃, or 555°C for Al-51-Mg systems).In addition, in the present invention, simply cladding the core material with the skin material without homogenization treatment sufficiently satisfies the required characteristics. can do.

Next, it is heated to a temperature below the melting point of the skin material and hot-rolled, but there is no need to specify any particular conditions for this. Hot rolling may be performed immediately after the chemical treatment.

After hot rolling, intermediate annealing is performed after cold rolling. Cold rolling is necessary to promote precipitation of solid solution elements during intermediate annealing, and the rolling reduction is preferably 10 to 90%.

In the intermediate annealing, it is preferable to heat the material at 300° C. or higher for 0.5 to 4 hours so that elements such as Mn, Cu, and Si in solid solution are likely to precipitate.

After intermediate annealing, final cold rolling is performed to produce a product, and the cold rolling rate (final cold rolling rate) is 30 to 70%. If this cold rolling ratio is less than 30%, a fin material having a strength that satisfies the requirement of thinning cannot be obtained. Note that if this cold rolling ratio is less than 25%, recrystallization of the fin material does not occur during brazing, Si of the skin material diffuses into dislocations, and the high temperature strength of the core material is extremely reduced. It has conventionally been thought that at a cold rolling reduction of 30% or more, strength can be obtained, but the high temperature strength during brazing decreases. However, as in the present invention, when the amount of Fe added is regulated, the number of recrystallized nuclei generated during brazing heating is reduced, and the amount of solid solution elements that inhibit recrystallization is reduced by adding Cu, high temperature A decrease in strength can be prevented. The reason why the upper limit of the cold rolling rate was set at 70% is that if it exceeds 70%, the amount of work will be large, and recrystallization nucleation will occur from the deformation zone.
The iQ crystal grains become finer, and Si from the skin material diffuses through the grain boundaries.
High temperature strength decreases.

A specific example of the A1-5i type or Al-51-Mg type brazing material used as the skin material in the present invention is A4.
343 (Al-7, 5% Si) with about 1% Zn added to it and A4004 (Al-10% 5i-1,
5% Mg), but is not limited to this.

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

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

Example Ingots (304x
700 x 1600 mm) was homogenized at 550°C for 5 hours, solidified and made into Al-7 equivalent to A4343 alloy.
, 5% Si skin material was clad on both sides with a 12% cladding ratio on one side.This composite material is shown in Table 2 below with experiment numbers ql ~
It was processed as shown in No. 17.

That is, after reheating at 520°C for 1 hour, hot rolling was carried out to 3.51 mm, cold rolling to a predetermined thickness, intermediate annealing at 360°C for 2 hours, and then cold rolling. A plating sheet for fins of 0.12 m5 was prepared.

The fin material obtained as described above was tested for tensile strength, high temperature buckling resistance, and corrosion resistance. The results are shown in Table 2.

(1) High-temperature buckling resistance test A sample (11) with a diameter of 22 m5 and a length of 60 m5 was prepared from a plating sheet for fins obtained by processing using processing methods 1 to 17 using alloys A to E as core materials, As shown in Figures 1 (a) and (b), hold this on a stand (12) using a fixture (13) to hold the tx22"
Heat at 610° C. for 10 minutes in air. High-temperature buckling resistance is evaluated based on the amount of droop after heating as shown in FIG. 1 (c).

In this evaluation method, it was confirmed that if the amount of droop was 15 or less, there would be no problem when an actual capacitor was assembled and brazed.

Therefore, a drooping amount of 15 ■I or less is judged to be acceptable.

(2) Pitting corrosion resistance test of fin material As shown in Figure 2, after corrugating the fin material (21), 0.8” x 20 x 100 pieces on both sides (■ own)
A3003 plates (22) were brazed using a non-corrosive flux brazing method.

This specimen was subjected to a salt water spray test (according to J I 5Z2371) for 4,000 hours to examine pitting corrosion that occurred in the A3003 board.

(Effects of the Invention) According to the present invention, the strength and high-temperature buckling resistance can be further improved than in the past, and the fin can be made thinner.

According to the method of the invention, it is thus possible to produce thin aluminum sheets for fins suitable for non-corrosive black spraying and carrier gas spraying.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are explanatory diagrams of a test method for buckling resistance of fin materials, and FIG. 2 is an explanatory diagram of a pitting corrosion resistance test of fin materials. Patent Applicant Furukawa Aluminum Industries Co., Ltd. Agent Patent Attorney Ii 1) Toshi 73 Figure 1 Figure 2 Figure No. 1 /C/C/ Tsum

Claims (1)

[Claims] Mn0.6-2%, Fe0.3% or less, Si0.6% or less, Cu0.02-0.2%, Zn0.5-2.0%,
A composite material made of an aluminum alloy with the remainder Al (wt% or more) as a core material and an Al-Si or Al-Si-Mg brazing material as a skin material is hot-rolled and cold-rolled, and then subjected to intermediate annealing. A method for producing an aluminum thin plate for brazing, which is then cold rolled at a rolling rate of 30 to 70% to obtain a final thickness.