JPH03287738A - Fin material for heat exchanger assembled by vacuum brazing method and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a fin material for a heat exchanger assembled by a vacuum brazing method and excellent in buckling resistance and strength after brazing by incorporating specified ratios of Mn, Si, Mg, Zr and Ti into Al. CONSTITUTION:An Al alloy ingot contg., by weight, 0.7 to 1.1% Mn, 0.6 to 1.0% Si, 0.3 to 1.5% Mg, 0.01 to 0.2% Zr, 0.05 to 0.2% Ti and the balance substantial Al is subjected to soaking treatment in the temp. range of 450 to 520 deg.C soaking temp., is hot-rolled, is thereafter immediately cold-rolled and is subjected to annealing for refining. In this way, the fin material for a heat exchanger excellent in buckling resistance can be obtd., which has 0.05 to 0.4% remaining amt. of Mg after vacuum brazing, has 100 to 400mu average grain size and is excellent in strength.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a fin material for a heat exchanger assembled by vacuum brazing, and more particularly, to
The present invention relates to a fin material for a heat exchanger that has excellent buckling resistance during brazing and allows thinning of the fin material, a method for manufacturing the same, and a fin material for a heat exchanger assembled by a vacuum brazing method.

(Prior Art) Generally, a brazed heat exchanger is composed of a plate material made of a plating sheet, a tube, and a corrugated fin material, and is assembled by various brazing methods.

In heat exchangers such as evaporators, attempts are being made to reduce costs and weight by making the fin materials thinner, but there are also problems such as buckling resistance during brazing and insufficient strength after brazing. many. In addition, using the fin material of heat exchangers assembled by brazing as a sacrificial anode to suppress penetrating corrosion of tubes and plate materials has been considered, and some have been put into practical use, but the thickness of the fin material M is added for the purpose of improving strength when it becomes less than 100 μm.
The amount of evaporation of g is increased and sufficient strength cannot be obtained. Similarly, the amount of evaporation of Zn added to make the fin material act as a sacrificial anode increases, making it impossible to obtain a sufficient sacrificial anode effect.

(Problems to be Solved by the Invention) Al-1,2%Mn-0,1%Sn (or In) alloys are known as aluminum alloys used as sacrificial anode fin materials (for example, , Japanese Patent Publication No. 59-22
6144 etc.). However, this alloy is prone to cracking during hot rolling, and there are problems with scrap management and processing, which increases material costs.

Furthermore, Al-1,2% Mn-1,5% Zn alloys have also been studied (for example, JP-A-56-142845).

However, it has not been put into practical use due to problems such as instability of the sacrificial anode effect and contamination of the vacuum brazing furnace by evaporated Zn.

Furthermore, in order to respond to the thinning of fin materials, it is desired to improve the buckling resistance of current products and increase the strength after brazing. This will be essential for promoting the project.

The present invention has been made in response to these demands, and is capable of improving buckling resistance and strength after brazing in a fin material for a heat exchanger assembled by vacuum brazing, and making it possible to reduce the thickness of the fin material. The purpose is to provide technology that makes it possible.

(Means for Solving the Problems) In view of these problems, the present inventor has conducted extensive research into the composition and manufacturing process of fin materials for heat exchangers assembled by vacuum brazing.

We discovered that it acts as a sacrificial anode on the tube material made of pre-zinc sheet, and also improves the buckling resistance and strength after brazing, making it possible to make the fin material thinner. It is an invention.

That is, in the present invention, Mn: 0.7 to 1.1%, Si:
0.6-1.0%, Mg: 0.3-1.5%, zr: 0
．． 01 to 0.2% and Ti: 0.05 to 0.2%, and if necessary further contains Zn: 0 and 5 to 3%, with the remainder substantially consisting of Al. The gist of this article is a fin material for heat exchangers that can be assembled by brazing.

In addition, the manufacturing method involves soaking an aluminum alloy ingot having the above chemical components at a soaking temperature of 450 to 520°C, and after hot rolling, cold rolling without intermediate annealing. , and is characterized by subjecting it to final temper annealing.

Furthermore, the fin material of the heat exchanger assembled by the vacuum brazing method is characterized in that it has the above chemical components and the residual amount of Mg after vacuum brazing is in the range of 0.05 to 0.4%. Alternatively, the average crystal grain size after vacuum brazing is in the range of 100 to 400 μm.

The present invention will be explained in more detail below.

(effect) First, the knowledge that led to the present invention will be explained.

For plating sheets that make up the tubes and tanks of heat exchangers assembled by vacuum brazing, the core material is generally made of Al2-Mn alloy 3003, and the brazing material is Al-3i-Mg alloy. 4004 and 4104 are used.

Various experiments have revealed that in order to act as a sacrificial anode on these plating sheets, it is necessary to make the pitting potential of the fin material 30 mV or more more base than the pitting potential of the plating sheet surface. did. S as an alloying element
30mV from plating sheet without using n or indium
For example, pure aluminum is known as an aluminum alloy having a base pitting potential, but it is not practical as it has insufficient strength as a fin material. 3003, an Al-Mn alloy commonly used as a fin material, has medium strength and good brazing properties, but there is almost no difference in pitting potential from the plating sheet. Therefore, the sacrificial anode effect cannot be obtained.

Therefore, as a result of investigating a method for shifting the pitting corrosion potential of the Al-Mn alloy to a less noble state, it was found that the most effective method is to suppress the amount of solid solution of Mn.

Specifically, these include regulating the amount of Mn added, fixing Mn as an AM-Mn-Fe-based compound by adding Fe, and precipitating the AM-Mn-based compound by optimizing the soaking process.

On the other hand, if the thickness of the fin material is 100μ or more, such measures are effective, but in order to cope with the thinning of the fin material, it is necessary to improve the strength after brazing. .

The addition of Mg is effective against the decrease in strength due to the regulation of Mn content, and the addition of Mg is effective in suppressing recrystallization in improving sag resistance and buckling resistance. It has become clear that controlling the cold working rate before brazing is effective. However, as described above, as the fin material becomes thinner, the evaporation and scattering of Mg during brazing increases, and it has been found that sufficient post-brazing strength cannot be obtained by adding Mg alone.

Therefore, in order to improve the strength after brazing, we investigated alloys with various compositions and found that Al-Mn-Si alloys show less deterioration in properties as fin materials, and that the coexistence of Mg further improves the strength. It has been found. In addition, as a result of examining the influence of manufacturing conditions on alloys with the same composition, we found that M
High strength was obtained by low-temperature soaking in which n coarse precipitates were not formed, and higher strength was obtained in the H2 type than in the H1 type in which intermediate annealing was performed.

It has also been found that for alloys with the same composition, the smaller the crystal grain size after brazing, the higher the strength can be obtained.

As is clear from the above findings, the present invention was completed as a result of various studies aimed at improving the strength after brazing, and based on the results, progress was made to improve the characteristics required of the fin material. .

In other words, the method for improving the strength after brazing is as described above, but the fin material has buckling resistance and brazing properties during brazing, and is at least electrochemically abrasive to tubes, etc. etc. are required.

To improve buckling resistance during brazing.

The grain size seen from the plate surface is at least 10 after brazing.
It is necessary that the thickness is 0 μm or more, and for this purpose, Zr
This can be done by adding or controlling manufacturing conditions. The same applies to improvement of brazing properties. On the other hand, as the crystal grain size becomes coarser, the strength decreases. The crystal grain size after brazing that can ensure strength after brazing while maintaining buckling resistance during brazing is limited to a range of 100 to 400 μI.

In order to obtain a sacrificial anode effect on the tube material, Mn
Although it is preferable to suppress the solid solution amount as much as possible, in the brazing method using a carrier gas, although the addition of Zn causes contamination of the furnace, the remaining Zn provides a sacrificial anode effect.

Next, the reasons for limiting the chemical components in the present invention will be described.

Mn: Mn is an element necessary to ensure strength and brazability during and after brazing, but on the other hand, as the amount of solid solution increases, the pitting potential of the aluminum alloy becomes more It is necessary to suppress the amount as much as possible. The lower limit value is set at 0.7% as the minimum addition amount necessary to maintain brazeability and strength after brazing. On the other hand, by adding Fe and Si and controlling manufacturing conditions.

The upper limit of the addition amount that suppresses the amount of solid solution and provides a base pitting potential for the plating sheet is 1.1%.

Si: Si is added as an alloying element to improve strength after brazing. However, if the amount added is less than 0.6%, sufficient strength will not be obtained, and if it is added more than 1.0%, the strength will improve, but the melting point will decrease and the buckling resistance will decrease, which is not preferable. Therefore, the amount of Si added is 0.6 to 1.0%, which can improve the strength without inhibiting brazing properties.
limited to the range of

Mg: Mg is necessary to obtain strength after brazing, and the required strength after brazing of the fin material is, for example, 16K.
g/am”, residual M, amount is 0.15
% is required. Considering evaporation and scattering during brazing, the amount added to the material needs to be 0.3 to 1.5%. It should be noted that if Mg is contained less than 0.3%, sufficient strength cannot be obtained, and if it is contained more than 1.5%, it is not preferable because it causes a decrease in brazing properties and erosion of the fin material by the brazing material.

Zr: Zr is effective in controlling the structure of the fin material and improving buckling resistance during brazing.

However, if it is less than 0.01%, the effect is insufficient;
Moreover, if it exceeds 0.2%, the effect will be saturated, and on the contrary, coarse intermetallic compounds will be formed, resulting in a decrease in workability, which is not preferable. Therefore, the Zr content is in the range of 0.01 to 0.2%.

Ti: Ti forms a compound of Al and TiAl, crystallizes, and then disperses in layers during hot rolling and cold rolling, and has the effect of flattening recrystallized grains along the rolling direction during brazing. There is. As a result, reduction in strength can be suppressed and buckling resistance can be improved. However, if the amount added is less than 0.05%, such effects will be insufficient, and if it exceeds 0.2%, coarse intermetallic compounds will be formed, resulting in a decrease in workability, which is not preferable.

Therefore, the amount of Ti is set in the range of 0.05 to 0.2%.

Zn: Zn has the effect of shifting the potential of the fin material to a less noble state and causing the fin material to act as a sacrificial anode on the tube material.
Evaporates and scatters due to vacuum brazing.

However, by controlling the composition and crystal grain size of the fin material, it is possible to allow some of it to remain. The amount remaining varies depending on the degree of vacuum during brazing.

Considering the amount evaporated during brazing, the amount of Zn added is in the range of 0.5 to 3%. If it is less than 0.5%, the sacrificial anode effect will be insufficient, and if it exceeds 3%, contamination of the furnace will be accelerated, which is not preferable.

Note that Zn may be added as necessary.

(Manufacturing conditions) Next, the manufacturing conditions of the fin material will be explained.

First, the reason why the soaking temperature before hot rolling was regulated is as follows.

In other words, buckling resistance and strength after brazing greatly depend on the structure of the fin material, and if recrystallization is completed at a temperature just below the brazing temperature and the crystal grain size is 100 μm or more, buckling resistance is achieved. It turned out to be excellent. Furthermore, if the average crystal grain after brazing exceeds 400 μι, the strength will decrease significantly even if the structure is controlled. Therefore, it is necessary to observe the average crystal grains of the fin material after brazing from the plate surface and establish the manufacturing conditions of the material so that the grain size is in the range of 100 to 400 μm. As a manufacturing process to obtain such a structure, the soaking temperature before hot rolling is set at 450 to 5
It is regulated within the range of 20°C.

After soaking treatment, hot rolling is performed and cold rolling is performed, but intermediate annealing is not performed along with cold rolling, and temper annealing is performed at the end after cold rolling to improve the strength after brazing. This is to improve the performance.

Examples of the present invention are shown below.

(Example) First, an aluminum alloy fin material (sample material) with a thickness of 01 o 8 Peng was manufactured by the process under the conditions shown in Table 1 for an aluminum alloy having a water chemical component, and was used in the following experiment. provided. The manufacturing process for the H24 material is soaking treatment → hot rolling → cold rolling → final annealing, and for the HI3 material, it is soaking treatment → hot rolling → cold rolling (including intermediate annealing).

]11L The obtained test material was heated to two types of vacuum degree A (2X) shown in Table 2.
10'Torr), B (I x 10'Torr,
After heating at 595° C. for 3 ml in a vacuum (using a carrier gas), mechanical properties were measured. The results are shown in Table 2.

As is clear from Table 2, the materials of the present invention are all 3003 alloy (Na
Compared with 23), considerably high strength is obtained. In addition, the average value of the crystal grain size observed from the plate surface side of the fin material heated under the same conditions and the average content of Mg in the fin material measured by wet chemical analysis are also listed.
It was confirmed that the crystal grain size was in the range of 100 to 400 μm and the residual amount of Mg was in the range of 0.105 to 0.4%.

A test piece of the shape shown in Figure 1 (10 peaks, pitch 5
Il Garden's fin, fin height 121, fin width 25
■ Set it in a vacuum of 5X10 Torr and
℃×3mln, and the amount of buckling was measured to evaluate the buckling resistance. The results are also listed in Table 2.

From Table 2, it can be seen that all of the materials of the present invention have a buckling resistance equivalent to or higher than that of the 3003 alloy, which has been conventionally frequently used as a fin material.

The moxibustion sample material was heated at 595°C x 3 w in a vacuum of 5 x 10 Torr.
After in-heating, electrochemical properties were measured. The results are also listed in Table 2.

From Table 2, all of the materials of the present invention exhibit lower pitting corrosion potentials than the 3003 alloy, which has conventionally been widely used as a fin material. Therefore, since it is electrochemically less noble with respect to the tube plating sheet, at least it does not promote corrosion.

[Blank 1 (Effects of the Invention) As detailed above, according to the present invention, excellent buckling resistance and strength after brazing can be obtained, and a base potential can be reduced with respect to the tube plating sheet. Therefore, the anticorrosion effect of the tube material can be expected due to the sacrificial anode action. Therefore, significant industrial effects such as cost reduction and weight reduction of the heat exchanger can be obtained.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is an explanatory diagram showing the shape of a test piece for a buckling resistance test. 1...fin.

Claims (5)

[Claims] (1) In weight% (the same applies hereinafter), Mn: 0.7 to 1.1
%, Si: 0.6-1.0%, Mg: 0.3-1.5%
, Zr: 0.01-0.2% and Ti: 0.05-0.
A fin material for a heat exchanger assembled by a vacuum brazing method, characterized in that the fin material contains 2% Al and the remainder is substantially made of Al. (2) Mn: 0.7-1.1%, Si: 0.6-1.0
%, Mg: 0.3-1.5%, Zr: 0.01-0.2
% and Ti: 0.05 to 0.2%, and further Zn: 0
．． A fin material for a heat exchanger assembled by a vacuum brazing method, characterized in that the fin material contains 5 to 3% of Al, and the remainder is substantially made of Al. (3) In producing a fin material for a heat exchanger, an aluminum alloy ingot having the chemical composition according to claim 1 or 2 is soaked at a soaking temperature of 450 to 520°C,
A method for producing a fin material for a heat exchanger assembled by a vacuum brazing method, which comprises performing cold rolling without intermediate annealing after hot rolling, and finally subjecting the material to temper annealing. (4) It has the chemical component according to claim 1 or 2, and
A fin material for a heat exchanger assembled by a vacuum brazing method, characterized in that the residual amount of Mg after vacuum brazing is in the range of 0.05 to 0.4%. (5) It has the chemical component according to claim 1 or 2, and
A fin material for a heat exchanger assembled by a vacuum brazing method, characterized in that the average crystal grain size after vacuum brazing is in the range of 100 to 400 μm.