JPH0788676A - Manufacture of aluminum alloy brazing filler metal and heat exchanger made of aluminum alloy - Google Patents

Abstract

PURPOSE:To reduce buckling of fin during brazing, secure the effect of improving heat conductivity and strength of members and enable miniaturization and lightening in weight of a heat exchanger when the heat exchanger is manufactured. CONSTITUTION:This aluminum alloy brazing filler metal consist of 7.0<Si<=12.0wt.%, 0.1<Cu<=8.0wt.%, 0.05<Fe<=0.5wt.%, >=1 kind or >=2 kinds of 0.05<Zn<=0.5wt.%, 0.002<In<=0.3wt.%, 0.002<Sn<=0.3wt.% and the balance Al with inevitable impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy brazing material and a method for manufacturing an aluminum alloy heat exchanger. More specifically, the present invention relates to an aluminum alloy heat exchanger having excellent thermal efficiency and high strength. The present invention provides an aluminum alloy brazing material to be manufactured by a method and a brazing method using the same.

[0002]

2. Description of the Related Art A heat exchanger such as a radiator has a plurality of flat tubes (1) integrally formed with corrugated thin fins (2) as shown in FIG. Both ends of the flat tube (1) are opened in the space formed by the header (3) and the tank (4), and the flat tube (1) is passed through from the space on the side of one tank to a high temperature. The refrigerant is sent to the space on the side of the other tank (4), and heat exchanged in the tubes (1) and fins (2) to circulate the refrigerant that has become low temperature.

The tube material and header material of such a heat exchanger are, for example, JIS3003 (Al-0.15 wt% Cu).
-1.1 wt% Mn) alloy as a core material, and the inside of the core material, that is, the side that is constantly in contact with the refrigerant, is provided with JIS7 as a lining material.
A 072 (Al-1 wt% Zn) alloy and a brazing sheet clad with a brazing material such as JIS 4045 (Al-10 wt% Si) alloy are usually used on the outside of the core material. It is integrally assembled with other members by brazing.

FIG. 2 shows a serpentine type condenser, in which a tubular material (5) extruded into a tubular shape while hot or warm is bent in a meandering shape, and a corrugated fin (6) made of a brazing sheet is provided between the tubular materials. Is attached. Here, (7) indicates a connector. JIS3003 alloy is used for the pipe material, and J is used for the fin.
Zn for the purpose of giving IS3003 alloy and its sacrificial effect
JIS4045 alloy or J
A brazing material such as IS4343 (Al-7.5 wt% Si) alloy is clad on both sides. All of these are assembled by brazing by heating to a temperature of around 600 ° C and brazing. As a brazing method, a flux brazing method, a nocolock brazing method using a non-corrosive flux, etc. are used.

By the way, in recent years, heat exchangers have been in the direction of weight reduction and downsizing, and therefore thinning of materials has been desired. However, when the thickness is reduced by the conventional method, many problems occur.

First, the refrigerant passage constituent member (tube material, etc.)
However, even for fins, it is necessary to improve the strength as much as the material thickness is reduced, and some high strength alloys have been proposed, but sufficient strength has not been obtained. This is because it is necessary to add an alloying element to improve the strength of the material, but the addition of the alloying element lowers the melting point of the material,
This is because it melts during the brazing step of heating to a temperature near 0 ° C.

Further, in the refrigerant passage constituent member having a sacrificial layer, when an alloy containing Cu is used for the core material, Cu diffuses into the sacrificial layer during brazing, and the sacrificial layer does not have an effect as a sacrificial layer, resulting in corrosion resistance. Is reduced. Therefore, the amount of Cu that can be added to the core to improve the strength is limited.

Further, the phenomenon that the fins buckle during brazing or the wax diffuses and melts in the fins is more likely to occur as the fins become thinner, with a bare fin having a plate thickness of 50 μm and a brazing sheet fin having a plate thickness of 100 μm. It is said to be the limit. When buckling occurs in this way, the thermal efficiency of the heat exchanger decreases due to an increase in ventilation resistance.

Further, in order to solve the problem that the heat efficiency of the heat exchanger decreases as the material becomes thinner, fins having excellent thermal conductivity have been developed. For example, a fin material made of Al--Zr alloy is used. Proposed. However, such a fin material has low strength and has a problem that the brazing material is likely to diffuse when the brazing material is heated.

[0010]

In view of this, the present invention provides an aluminum alloy brazing material for producing an aluminum alloy heat exchanger that can be made compact and lightweight, and an aluminum alloy heat exchanger using the same. It was developed about the manufacturing method.

That is, the first aspect of the present invention contains Si in an amount of more than 7.0 wt% and 12.0 wt% or less, Cu in an amount of more than 0.1 wt% and 8.0 wt% or less, and Fe in an amount of more than 0.05 wt% and 0.5 wt% or less. , 0.
Zn over 05 wt% and 0.5 wt% or less, over 0.002 wt%
An aluminum alloy brazing material containing 0.3% by weight or less of In and 0.002% by weight or more and 0.3% by weight or less of Sn, and the balance being aluminum and inevitable impurities.

In the second aspect of the present invention, when an aluminum alloy heat exchanger is manufactured by brazing, Si of more than 7.0 wt% and 12.0 wt% or less, Cu of more than 0.1 wt% and 8.0 wt% or less of 0.05, containing more than 0.5 wt% and less than 0.5 wt% Fe,
Zn over 0.05 wt% and 0.5 wt% or less, over 0.002 wt%
An aluminum alloy brazing material containing 0.3% by weight or less of In and 0.002% by weight or more and 0.3% by weight or less of Sn, and the balance aluminum and unavoidable impurities is used. A method for manufacturing an aluminum alloy heat exchanger, characterized in that brazing is performed at a temperature of ℃ or less.

First, the concept of the present invention will be described.
When the aluminum alloy heat exchanger is manufactured by the brazing method as described above, the heating is usually performed at a temperature near 600 ° C. Since the temperature of 600 ° C. is considerably high for aluminum alloys, the following four problems occur. That is, the fins buckle during heating, the intermetallic compound in the alloy re-dissolves to reduce the thermal conductivity of the fins, the high-strength alloy with a low melting point cannot be used, and the refrigerant passage constituent member having a sacrificial layer Cu of core material
Will diffuse into the sacrificial layer and the corrosion resistance will decrease.

The inventors of the present invention conducted extensive studies to solve these problems, and thought that it would be effective to lower the brazing heating temperature, and examined how many degrees C or lower it could solve such problems. However, if the temperature is 585 ° C. or lower, buckling of fins during brazing is less likely to occur, thermal conductivity is slightly reduced, and the strength of the alloy can be improved by increasing the addition amount of Si. It has been found that the amount of diffusion of Pd decreases and the corrosion resistance improves. The above four points will be described in more detail.

Most of the buckling of the fins is caused by the high temperature creep phenomenon of the fins at a high temperature, and suddenly occurs at a temperature higher than 590 ° C. as a boundary (the fins are weakened). I found that. Therefore, 5
If the temperature is below 85 ° C, buckling due to this will not occur. Furthermore, although there is buckling due to the diffusion of wax in the fin, it was found that the diffusion of wax occurs rapidly around 595 ° C at higher temperatures. for that reason,
If the temperature is 585 ° C or lower, the wax diffusion is reduced, and the fins are less likely to buckle as a whole.

The thermal conductivity of the fin material to be brazed is lowered because the intermetallic compound precipitated in the aluminum alloy re-dissolves when the brazing heat is applied. The higher the heating temperature, the larger the solid solution limit of the alloying element and the higher the diffusion rate, so that the re-solid solution is likely to proceed.
Therefore, it was found that lowering the brazing temperature was effective in increasing the thermal conductivity of the fins, and at 585 ° C or less, the re-dissolution rate was low and the thermal conductivity did not decrease significantly. .

Regarding strength, elements added as a high-strength aluminum alloy include Cu, Mg, Si, etc., but when used as a refrigerant passage constituent member, corrosion resistance and brazing property must be taken into consideration, and as a fin. When used, sacrificial effect, thermal conductivity and brazeability must be considered. Therefore, the number of elements that can be added to increase the strength is limited, and specifically, the addition of Si is effective. The amount of Si that can be added by brazing at 600 ° C is about 1 wt%, but at 585 ° C or less, about 2.5 wt% can be added.

Up to now, it has been difficult to increase the strength of a material having a sacrificial layer as a refrigerant passage constituent member. This is because when Cu is added to the core material to increase the strength, the corrosion resistance of the refrigerant passage constituting member is sharply reduced. As a result of intensive investigations by the inventors regarding this cause, Cu in the core material diffuses into the sacrificial layer and a component of the sacrificial material (for example, Zn) diffuses into the core material, so that the component of the sacrificial layer is brazed. It was found that there was a large change compared with the previous one, which caused a decrease in sacrificial effect and a decrease in corrosion resistance. Therefore, we studied various methods to prevent diffusion, but found that there is no preventive effect in the usual method because it occurs due to the diffusion of atoms at high temperature, and that lowering the heating temperature is an effective means, The temperature was examined. As a result,
As a result of comparing the upper limit temperature of 585 ° C with the normal brazing temperature of 600 ° C, it was found that in the case of 585 ° C, the diffusion amount is smaller and the corrosion resistance is improved.

As a method of brazing at a temperature lower than the normal brazing temperature, there is known a method of brazing at a temperature of about 500 ° C., which is called low temperature brazing. This method has a problem that the brazing material is easily corroded after brazing because an Al-Zn alloy or Zn alloy containing 20% or more of Zn is usually used as a brazing material. not being used. Furthermore, Al
In a Zn-based alloy, if the amount of Zn added exceeds 8%, the rolling property becomes very poor, so it is impossible to manufacture a brazing sheet by combined rolling, and a brazing sheet for low-temperature brazing is industrially stable. The manufacturing method to supply is not established. Therefore, brazing must be used for placing or the like, and the types of members that can be manufactured are limited. However, the inventors have found that the characteristics of the heat exchanger can be improved even at a brazing temperature of 585 ° C. or lower, which is much higher than the low temperature brazing as described above, and if so, it can be used as a brazing sheet. He thought that it would be possible to develop a wax and found its practicality.

By the way, there is an alloy conventionally known as a low melting point aluminum alloy brazing alloy (for example, Japanese Patent Laid-Open No. Hei 10 (1999) -242977).
3-57588). These are mainly developed for brazing castings, and contain a large amount of Cu or add a large amount of Zn as described above, so that they are cracked when rolling is performed. There was a problem and the brazing sheet could not be manufactured. If it cannot be used as a brazing sheet, it is not practical for industrially manufacturing a heat exchanger. The present invention has solved these problems and developed a braze that can be manufactured as a brazing sheet.

Here, the alloy composition of the brazing material of the present invention is 7.0.
Si over 12.0 wt% over wt%, 8.0 wt over 0.1 wt%
% Cu or less, 0.05 wt% or more and 0.5 wt% or less Fe is contained, and 0.05 wt% or more and 0.5 wt% or less Zn, 0.002 wt%
Over 0.3 wt% In, 0.002 wt% over 0.3 wt%
It is an aluminum alloy containing one or more of the following Sn. The reason for the limitation will be described below.

Si lowers the melting point of the alloy, but its amount is
If it is 7.0 wt% or less, the melting point is not sufficiently lowered and brazing cannot be performed at a temperature of 585 ° C or less. Further, when the amount exceeds 12.0 wt%, the melting point rises, so that brazing cannot be performed at a temperature of 585 ° C or lower.

Cu lowers the melting point of the alloy and improves the wax flowability. Further, Cu has a function of enhancing external corrosion resistance of the heat exchanger when an alloy containing Cu is used for the refrigerant passage constituting member. That is, various studies have been conducted on the external corrosion resistance of the heat exchanger, and when Cu is not added to the brazing filler metal, the Cu added in the passage forming member diffuses into the brazing filler metal during brazing, and the brazing filler metal and the passage constitution are formed. It has been found that a low Cu region is generated in the vicinity of the boundary with the member and is preferentially corroded, resulting in severe corrosion accompanied by swelling. In the present invention, Cu is added to the brazing material to prevent Cu from diffusing from the passage forming member to the brazing material, prevent a low Cu region from occurring near the boundary between the brazing material and the sacrificial material, and improve corrosion resistance. It was Here, if the amount of Cu is 0.1 wt% or less, the above effect is not sufficient, and if the amount exceeds 8.0 wt%, the brazing potential becomes too noble, and the refrigerant passage constituent members preferentially corrode. In addition to the deterioration of corrosion resistance, the rolling workability of the alloy is deteriorated, which makes it unsuitable for use in brazing sheets for heat exchangers. Therefore, Cu is 0.1 wt
% And 8.0 wt% or less, but stable characteristics are exhibited especially at 0.5 to 3.5 wt%.

Fe has the function of refining the crystal grains when the wax is solidified after melting and increasing the strength of the fillet, but if the amount is 0.05 wt% or less, it does not exhibit the effect sufficiently. Further, Fe forms an intermetallic compound during solidification, which becomes the starting point of corrosion. Therefore, the upper limit of the amount of Fe is 0.5 wt% because of the balance between the grain refinement effect and corrosiveness.
Stipulate.

Further, in the brazing alloy to which Cu is added as in the present invention, the occurrence of swelling due to external corrosion can be suppressed, but the electric potential of the brazing becomes nobler than the electric potential of the core material, and the external corrosion progresses in a pit shape. There is a problem of high speed.
The addition of Zn, In and Sn lowers the brazing potential, brings the brazing potential closer to that of the core alloy, and improves the corrosion resistance.
However, if the amount of Zn is 0.05 wt% or less and the amount of In and Sn is 0.002 wt% or less, the effect is not sufficient. The amount of Zn
If it exceeds 0.5 wt%, the melting point of the wax may be too low and the wax may diffuse into the core. In addition, the amounts of In and Sn are
If it exceeds 0.3 wt%, the self-corrosion resistance of the wax will decrease and
The rolling workability of the alloy deteriorates, making it unsuitable for use as a brazing sheet for heat exchangers.

Although the alloying elements of the brazing alloy of the present invention are as described above, 0.05 wt% of each of the other elements is inevitable as an inevitable impurity.
% Or less, it may be contained.

The brazing material of the present invention is used as a brazing sheet for brazing an aluminum alloy heat exchanger. Examples of the aluminum alloy heat exchanger here include, but are not limited to, a radiator, a condenser, and an evaporator. Here, the application of the present invention is limited to the heat exchanger, when the present invention is carried out, there is an effect of improving the thermal efficiency of the heat exchanger due to the effect of improving the heat conduction of the material, and further, the heat exchanger This is because it has an ordinary fin, but is effective in improving the high temperature buckling resistance of the fin.

In this case, the braze alloy composition is limited as described above, but the alloy composition of the aluminum alloy used for the other fins and the refrigerant passage constituting member is not particularly limited.
Alloys for brazing at temperatures around 600 ° C (eg 3
Alloys containing various elements based on 003 alloy and 100
0 type alloy) may be used as it is. This is because when the brazing of the present invention is performed at a temperature of 585 ° C. or lower, the high temperature buckling property and the thermal conductivity of the fin are necessarily improved. In addition, aiming at high strength of the alloy, for example, 10
It is also possible to use an aluminum alloy of 00 series alloy or 3000 series alloy to which Si is added by 1.2 wt% or more.

In the present invention, the brazing temperature exceeds 570 ° C. 5
Perform below 85 ℃. This is because when the brazing temperature is 570 ° C. or lower, the brazing material of the present invention has a composition that does not melt and cannot be brazed. Further, when the temperature exceeds 585 ° C, the thermal conductivity of the material is lowered and the high temperature buckling property of the fin is lowered, and further, an alloy having a low melting point or an alloy containing a large amount of Cu is used as the refrigerant passage constituting member. This is because it cannot be used for. By decreasing the brazing temperature in this way,
This has the effect of extending the life of the brazing furnace.

Here, the brazing conditions of the present invention are limited in temperature as described above, but other conditions may be almost the same as the conventional one. That is, it is not particularly limited as long as it is a flux brazing method, a nocolock brazing method using a non-corrosive flux, or the like. Assembling before brazing, cleaning, and flux coating depending on the case may be performed as usual. In this case, the flux can be brazed in the temperature range of the present invention by using, for example, a cesium-based flux.

In the present invention, the steps after heating are not particularly limited. Processes such as aging treatment, flux removal, and painting may be performed as is conventionally done.

[0032]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A brazing sheet fin made of a combination of a brazing material having the alloy composition shown in Tables 1 and 2 and a core material was prepared. That is, the plate thickness of these brazing sheet fins is 0.11 mm, and the brazing material is 10% on both sides of the core material.
It is a H14 temper that is clad by each. These were heated in N ₂ gas under the conditions shown in Table 3 and a drooping test was conducted. The hanging test was performed with a protrusion length of 50 mm. The results are shown in Table 3.
I wrote it in.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

Clearly from Table 3, the brazing sheet fins No. 1 to No. 23 using the brazing alloy of the present invention have drastically improved drooping characteristics as compared with the brazing sheet fins using the brazing alloys of the conventional example and the comparative example. There is.

(Example 2) A three-layer brazing sheet plate having a plate thickness of 0.25 mm and made of a brazing filler metal, a core member and a sacrificial member having the compositions shown in Tables 4 and 5 was manufactured by an ordinary method. did. That is, the clad ratio of the brazing material clad to the core material is 10%, and the clad ratio of the sacrificial material is 15%. Further, Fe, S as impurity elements in the sacrificial material.
i is included in the range of 0.01 to 0.2 wt%.
These were heated in N ₂ gas under the conditions shown in Table 6. The obtained plate material was subjected to a tensile test and an external corrosion resistance test and an internal corrosion resistance test as described below, with the brazing material part as the outer side and the sacrificial layer part as the inner side.

In the external corrosion resistance test, only the central portion of the surface of the brazing material was exposed, all the other surfaces were sealed, and a CASS test (JISH8681) was conducted for 360 hours to examine the occurrence of pitting corrosion. The results are shown in Table 6.

The internal corrosion resistance test was conducted by using a plate material with the brazing material masked in tap water containing 10 ppm of Cu ²⁺ ions.
It was immersed for 8 months and subjected to a cycle corrosion test at 80 ° C. for 8 hours and room temperature for 16 hours, and the pit depth generated on the surface of the sacrificial material was determined by the depth of focus method using an optical microscope. The results are shown in Table 6.

[0041]

[Table 4]

[0042]

[Table 5]

[0043]

[Table 6]

From Table 6, in Comparative Examples 11 and 17, Zn and I were used as brazing materials.
Since it does not contain n and Sn, the external corrosion resistance is reduced. In Comparative Example 12, the brazing material does not contain Cu, and the external corrosion resistance is reduced. Comparative Examples 13, 14, and 15 are out of the range of the brazing alloy of the present invention, and the brazing does not melt at 585 ° C or lower, so heating was performed at a temperature of 600 ° C or higher, but the core material melted. It was In Comparative Example 15, Cu and Zn of the brazing alloy were added in an amount exceeding the range of the present invention, and the brazing sheet could not be manufactured due to cracking during rolling. The conventional example is an example in which a relatively large amount of Cu is contained in the core material, but the corrosion resistance is poor. On the other hand, according to the example of the present invention, a high-strength material can be used and the corrosion resistance is excellent.

(Embodiment 3) An aluminum alloy fin material having a plate thickness of 0.06 mm made of a bare material having a composition shown in Tables 7 and 8 and a core material having a composition shown in Nos. No.
Clad a brazing filler metal having a composition shown in 3 to 7 with a thickness of 10%,
As shown in Table 8, a combination of an electric resistance welded tube material with a plate thickness of 0.3 mm and a header plate material with a plate thickness of 1 mm, in which the sacrificial material with the following composition is clad at a thickness of 15% on the other surface, The radiator shown in 1 was assembled. That is, the sacrificial material composition of the member numbers No. 3, No. 4, and No. 7 is Al-4 wt%
Zn-2 wt% Mg alloy, No. 5 member number is Al-
4 wt% Zn, material number No. 6 is Al-1 wt% Zn
Is. Here, for the tube material, a coil-shaped plate material having a plate thickness of 0.3 mm shown in Table 7 is manufactured by an ordinary method, and the coil-shaped plate material is slitted to a width of 35.0 mm according to the size of the electric resistance welding pipe.
It was made into a strip material. Then, this strip was processed into an electric resistance welded pipe with a width of 16.0 and a thickness of 2.2 mm using a resistance welded pipe manufacturing device. In addition, a coil-shaped plate material with the same configuration and a plate thickness of 1.0 mm is
It was slitted to 60 mm and used as the strip for the header plate.

The assembled radiator was applied with a 10% concentration solution of a flux obtained by mixing 3% of a cesium-based flux with a potassium fluoride-based flux, and heating in N ₂ gas under the brazing addition heat conditions of Table 8, Brazed With respect to the obtained radiator, it was examined by observing the appearance whether or not the crushed condition of the fins and tubes and the brazing property for forming the fillet were good. The results are shown in Table 8. In addition, the heat efficiency of the normally brazed heat exchanger was investigated. The thermal efficiency was measured according to JIS D 1618 (Testing method for air conditioners for automobiles). Table 8 shows the rate of improvement with respect to the thermal efficiency of the conventional heat exchangers (in Table 8). In addition, the results of the tensile test performed on the tube material after the brazing heat is also shown.

[0047]

[Table 7]

[0048]

[Table 8]

In the method of the present invention, the heat exchanger is manufactured without causing the fins to be crushed, high strength materials can be used, and the manufactured radiator is excellent in thermal efficiency.

[0050]

As described above, when a heat exchanger is manufactured using the brazing alloy of the present invention, there is little buckling of the fins during brazing, and there is an effect of improving the thermal conductivity and strength of the member. The size and weight of the exchanger can be reduced, which is a significant industrial effect.

[Brief description of drawings]

FIG. 1 is a perspective view, partly in section, showing a radiator.

FIG. 2 is a perspective view of a partial cross section showing a serpentine type evaporator.

[Explanation of symbols]

 1 Flat tube 2 Fins 3 Header 4 Tank 5 Tubing 6 Fins 7 Connector

Claims (2)

[Claims] 1. Si of more than 7.0 wt% and 12.0 wt% or less,
Cu exceeding 0.1 wt% and 8.0 wt% or less, exceeding 0.05 wt% 0.
Fe of 5 wt% or less, Zn of more than 0.05 wt% and 0.5 wt% or less, In of more than 0.002 wt% and 0.3 wt% or less, 0.0
An aluminum alloy brazing material characterized by containing one or more of Sn in an amount of more than 02 wt% and 0.3 wt% or less, and the balance being aluminum and inevitable impurities. 2. When manufacturing an aluminum alloy heat exchanger by brazing, Si is more than 7.0 wt% and less than 12.0 wt%, Cu is more than 0.1 wt% and less than 8.0 wt%, Cu is more than 0.05 wt% and 0.5 wt%. % Fe or less, 0.05 wt% over 0.5
Zn of less than wt%, I of more than 0.002 wt% and less than 0.3 wt%
n, more than 0.002 wt% and 0.3 wt% or less of Sn, 1 type or 2 types or more are contained, and the aluminum alloy brazing filler metal which consists of the balance aluminum and unavoidable impurities is used. A method for manufacturing an aluminum alloy heat exchanger, which comprises brazing.