JPH0196357A - Manufacture of aluminum thin plate for brazing - Google Patents

Abstract

PURPOSE:To obtain an Al alloy thin plate for a fin suitable as corrosion- resistant flux brazing and vacuum brazing by subjecting an Al alloy having specific compsn. to a heat treatment, hot rolling and cold rolling including intermediate annealing. CONSTITUTION:The ingot of the Al alloy contg., by weight, 0.2-2.0% Mn, 0.3-0.8% Fe, <0.6% Si and <2.0% Zn is heated to 420-540 deg.C, is retained for 1-24hr and is subjected to a homogenizing treatment. The alloy is then hot rolled, is immediately or after hot rolling, subjected to intermediate annealing at least for two times and is subjected to the cold rolling in such a manner that the cold rolling ratio from the intermediate annealing one time before the last to the final annealing is regulated to 10-60% and the cold rolling ratio from the final intermediate annealing to the final plate thickness is regulated to 20-50%, by which the title thin plate is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a thin aluminum plate for fins that has excellent high-temperature buckling resistance and is suitable for non-corrosive Furazox bracing and vacuum brazing.

(Prior Art) Conventionally, as a fin material for an aluminum alloy heat exchanger, a bare material of A3003 alloy or a plating sheet of a laminated material clad with an Al-Si alloy has been used. In recent years, there has been an increasing demand for thinning of these fin materials, and each fin material has been made thinner by about 0.12 mm, and there are nine types. On the other hand, bare materials have been used at a thickness of about 0.12 mm from the beginning, and progress has not been made to make them thinner than that.

(Problem to be solved by the invention) The reason why the bare material for fins does not become thinner is because it is heated at a high temperature of 590 to 620 degrees Celsius in the pre-zinc process for manufacturing heat exchangers, so the material is thinned. The strength of the fins decreases due to heating, and as a result, the fins tend to collapse, a phenomenon known as buckling. Furthermore, even if the high-temperature strength of the material is simply increased, wax will diffuse into the fin material during brazing, resulting in a decrease in the high-temperature strength of the fin, which poses a problem when thinning the fin.

(Means for Solving the Problems) As a result of various studies in order to solve the above problems, the present inventors found that a material containing predetermined amounts of Mn and Fe, Si and Zn
It has been found that the objective can be achieved by using an aluminum alloy with a controlled n content and rolling with appropriate combinations of homogenization treatment conditions, number of intermediate annealing after hot rolling, and cold rolling rate. The present invention has been made based on this knowledge.

That is, the first aspect of the present invention is Mn 0.2 to 2. Owt%
(Hereinafter, wt% is simply written as %), Fe0.3-0.8%
, Si 0.6% or less, Zn 2.0% or less, and the balance A, when producing a thin plate material from an aluminum alloy ingot, after homogenizing at 420°C to 540°C for 1 to 24 hours, Intermediate rolling is performed, and intermediate annealing is performed at least twice in the process after hot rolling, and the cold rolling rate is 10 to 60 between the last intermediate annealing and the last intermediate annealing.
%, and cold rolling is performed at a cold rolling rate of 20 to 50% from the last intermediate annealing to the final plate thickness. It is.

The second aspect of the present invention is Mn 0.2-2.0%, Fe0.3-
0.8%, Cu 0.05-0.2%, Si 0.6% or less, Zn 2.0% or less, and the balance is Al when manufacturing a thin plate material at 420°C.
After homogenization treatment at ~540°C for 1 to 24 hours, hot rolling is performed, and intermediate annealing is performed at least twice in the process after hot rolling, from the last intermediate annealing to the last intermediate annealing. In the meantime, the cold rolling rate becomes 10 to 60%, and the cold rolling rate increases to 2 between the last intermediate annealing and the final plate thickness.
The present invention provides a method for producing an aluminum thin plate for brazing, which is characterized in that cold rolling is performed to achieve a rolling thickness of 0 to 50%.

The method of the present invention will be explained in detail below.

The reason for limiting the additive elements and amounts of the aluminum alloy used in the present invention as described above is as follows.

The amount of Mn added is 0.2 to 2.0%. Mn not only improves the strength of the alloy, but also forms fine precipitates of AfL-Mn-Fe or A1-Mn-5i, coarsening recrystallized grains and improving high-temperature buckling resistance during high-temperature heating during brazing. It has the function of improving sex. The amount of Mn added is 0.2
If it is less than 2.0%, the effect is small, and if it is added in excess of 2.0%, giant crystallized substances tend to form, resulting in poor formability as a fin material.

The amount of Fe added is 0.3 to 0.8%. Fe is A sentence,
Coexistence with Mn produces A-Mn-Fe type precipitates, which improves high-temperature buckling resistance during high-temperature heating.

There is no effect if the amount of Fe added is less than 0.3%, and 0.8%
If it is added in excess of this amount, the amount of crystallized material increases, the formability decreases, and corrugating becomes difficult.

The amount of Si added is 0.6% or less. Si is A! 1-M
It produces fine n-Fe-3i precipitates and has the function of improving high-temperature buckling resistance during high-temperature heating during brazing. When more than 0.6% of Si is added, the melting point of the alloy decreases and the high temperature strength decreases.

The amount of Zn added is 2.0% or less. Zn lowers the potential of the fin material and has a sacrificial anode effect to prevent pitting corrosion of working fluid passages such as tubes.

When Zn is added in excess of 2.0%, self-corrosion increases and brazability decreases.

The amount of Cu added is 0.05 to 0.2%.

Cu contributes to the potential of the fin to the extruded tube, but is useful for high temperature buckling resistance. Therefore, its addition is done in consideration of this, but if it is less than 0.05%, it will not have that effect, and if it exceeds 0.2%, the sacrificial anode effect cannot be changed.

Note that other elements (Mg, Cr, Zr, Ti, etc.) do not affect the effects of the present invention if their content is 0.05% or less.

Next, the steps of forming an alloy having the above composition into a thin plate by subjecting it to heat treatment and rolling treatment after casting will be sequentially explained.

First, an aluminum alloy ingot with the above components is heated to 420 to 540
Homogenization treatment is carried out at 1 to 24 hours at ℃. When homogenized, Mn, Fe, and Si dissolved in solid solution during casting are removed.
is precipitated as a fine intermetallic compound, and the Al-Fe-Mn-based and vertical-Fe-Mn-Si-based particles precipitated over the entire surface of the fin material improve high-temperature buckling resistance. If the temperature is less than 420° C., segregation during casting will not be sufficiently homogenized, and the hot rolling temperature will be low, making cracks likely to occur during hot rolling.

At temperatures exceeding 540°C, precipitation is difficult to proceed, and when precipitation occurs, its distribution is coarse rather than fine.
The effect of improving high temperature buckling resistance cannot be obtained. If the holding time of the homogenization treatment is less than 1 hour, fine precipitates will not be sufficiently formed and the high temperature buckling resistance will not be improved. Holding heat for 24 hours or more is not only economically inappropriate, but also causes the precipitates to become too coarse, which may reduce high-temperature buckling resistance. The retention time is 1
Most preferably, the time is between 9 hours and 9 hours.

In the present invention, hot rolling is performed after the homogenization treatment as described above, and intermediate annealing is performed at least twice immediately after hot rolling or at least twice after cold rolling. From the intermediate annealing to the last intermediate annealing, the cold rolling rate becomes 10 to 60%, and from the last intermediate annealing to the final plate thickness, the cold rolling rate becomes 20 to 50%. Perform cold rolling.

In the present invention, the temperature and time of intermediate annealing are not particularly limited and follow conventional methods, but are usually 320°C to 450°C and 0.
．． Preferably, the treatment is carried out for 5 to 6 hours.

The reason why conditions for intermediate annealing and cold rolling are limited in the present invention is as follows.

First, the reason for performing at least two intermediate annealings is that the coil after hot rolling is industrially unavoidable due to variations in temperature during hot rolling and differences in the cooling rate of the coil after hot rolling. This is to avoid variations in the metal structure due to variations in conditions. This variation in metallographic structure is mainly due to variation in the state of recovery and recrystallization, and for example, the amount of recovery in the inner circumference of the coil is greater than in the outer circumference of the coil, which is more easily cooled. Such differences cannot be completely eliminated by the conventional one-time intermediate annealing, and at least two intermediate annealings are required because they result in variations in the properties of the final product. The second reason is that intermediate annealing also serves as a precipitation treatment, and a fine precipitate layer is precipitated while intermediate annealing is performed at least twice to improve high-temperature buckling resistance.

Next, if the cold rolling rate from the last intermediate annealing to the last intermediate annealing is less than 10%, recrystallization will not be completely completed in the final intermediate annealing, and if it exceeds 60%, the cold rolling rate will be at the beginning of the intermediate annealing. After recrystallization is completed, the effect of atoms moving through dislocations and promoting precipitation is reduced, and high temperature buckling resistance is not improved in either case. If the cold rolling rate from the last intermediate annealing to the final plate thickness is less than 20%, recrystallization will not be completed on the heated surface where the solder is applied, and the solder will diffuse the sub-soldering of the fin material, reducing the high temperature buckling resistance of the fin material. Decreases sex. When the final cold rolling rate exceeds 50%, fine recrystallization occurs on the brazing heating surface, resulting in a decrease in high temperature strength.

The thickness of the thin plate material obtained by the method of the present invention is 0.10
It is preferable to set it to below mm. In the case of fins with a thickness exceeding 0.1 On+m, the strength of the fin material at high temperatures is often sufficient even without using the manufacturing method of the present invention, and with the thickness of the parentheses, the fins are The material cannot be made thinner. The lower limit of the plate thickness is not particularly limited and is preferably about 0.0411O1.

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

Example 1 DC ingot (thickness 100 mm) of an alloy having the composition shown in Table 1
After applying 1 oin per side to both sides, 4 as shown in Table 2.
After homogenizing the seed conditions, hot rolling was performed to obtain hot rolled plates with a thickness of 3.5 mm, and from these hot rolled plates, 0.07 weight brazing plates were obtained by the steps shown in Table 2. An aluminum thin plate was produced. The high temperature buckling resistance of the obtained thin plate was tested by the following method. The results are shown in Table 3.

High-temperature buckling resistance test A sample thin plate with a width of 22+sm and a length of 60mm was obtained from each sample material.
Create a
Use the fixture 3 on top to hold it in a cantilevered manner with a length of 501 cm,
Heat at 610'C for 10 minutes in air. Figure 1 (c)
High-temperature dust resistance is evaluated based on the amount of droop after heating as shown in the figure below. In this evaluation method, it was confirmed that if the amount of droop was 15 mm or less, there would be no problem when an actual capacitor was assembled and brazed.

Therefore, a drooping Q l of 51@l+ or less is determined to be acceptable.

As is clear from the results in Table 1 and Table 3, according to the method of the present invention, at a plate thickness of 0.07 mm, the droop J, 1 was less than 10 cm, showing excellent high-temperature buckling resistance. There is. On the other hand, in the comparative examples, the amount of droop exceeds 15I1m in all cases, and the high temperature buckling resistance is extremely poor.

Example 2 DC ingot (thickness 300 mm) having the composition shown in Table 4
After 2011II on one side and both sides, it was homogenized at 520"C for 4 hours, followed by hot rolling to a thickness of 3
．． 5a+w hot-rolled plates were used, and aluminum thin plates for brazing each having a plate thickness of 0.06 mm were produced using the hot-rolled plates according to the steps shown in Table 5. The resulting thin plate was tested for high temperature buckling resistance in the same manner as in Example 1. The results are shown in Table 6.

As is clear from the results in Table 4, Table 6, and Table 6, according to the method of the present invention, when the plate thickness is 0.06 mm, the amount of droop is 15 mm or less in all cases, indicating excellent high-temperature buckling resistance.

On the other hand, Plate B of the comparative example has a large amount of droop and is inferior in high temperature buckling resistance.

(Effects of the Invention) As described above, according to the present invention, a thin aluminum plate for brazing having excellent high-temperature buckling resistance can be manufactured. Therefore 1
According to the method of the present invention, the corrugated fins of the heat exchanger' can be made even thinner, making it possible to reduce the weight and cost of the heat exchanger.

[Brief explanation of the drawing]

FIGS. 1(A), 1(B), and 1(C) are explanatory diagrams of a buckling resistance test method for fin materials. Patent applicant Furukawa Aluminum Industries Co., Ltd. Agent Patent attorney Ii 1) Toshizo.

Claims (1)

[Claims] 1) Mn0.2-2.0%, Fe0.3-0.8%, S
i0.6% or less, Zn2.0% or less, balance Al (more than w
t%), hot rolling is performed after homogenization treatment at 420°C to 540°C for 1 to 24 hours, and at least 2% Intermediate annealing is performed twice, and the cold rolling rate is 10 between the last intermediate annealing and the last intermediate annealing.
60%, and cold rolling is performed at a cold rolling rate of 20 to 50% from the last intermediate annealing to the final plate thickness. 2) Mn0.2-2.0%, Fe0.3-0.8%, C
u0.05-0.2%, Si0.6% or less, Zn2.0
% or less, and the balance is Al (wt% or more) when producing a thin plate material from an aluminum alloy ingot with a composition of 420°C
After homogenization treatment at ~540°C for 1 to 24 hours, hot rolling is performed, and intermediate annealing is performed at least twice in the process after hot rolling, from the last intermediate annealing to the last intermediate annealing. In between, the cold rolling rate is 10 to 60%, and from the last intermediate annealing to the final plate thickness, the cold rolling rate is 2.
1. A method for producing an aluminum thin plate for brazing, which comprises performing cold rolling to achieve a rolling strength of 0 to 50%.