JPH0957486A - Al alloy brazing filler metal for vacuum brazing and production of al alloy brazing sheet and al alloy heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a size and weight of a heat exchanger by specifying a composition and using a Cu containing Al alloy brazing filler metal without adding Zn so as to lower the brazing temp. and improve high temp. buckling resistance/conductivity. SOLUTION: A brazing filler metal has a composition consisting of, by weight, 6.0-13.0% Si, 1.2-3.0% Cu, 0.2-2.0% Mg, 0.01-0.5% Sn and/or 0.01-0.5% In and the balance Al with inevitable impurities. At the time of executing brazing with using this brazing filler metal, the vacuum brazing in a temp. range of 570-585 deg.C is required. At the time of producing a heat exchanger, the brazing sheet, in which this brazing filler metal is cladded on one face or both faces of Al alloy core material, is preferably used. A covering rate of the brazing sheet is about 2-20% at the normal case, the Al alloy of core material is one suitable for brazing at a neighborhood of 600 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to vacuum brazing Al.
The present invention relates to a method for manufacturing an alloy brazing material, an Al alloy brazing sheet and an Al alloy heat exchanger, and more specifically, manufacturing an Al alloy heat exchanger having excellent thermal efficiency, high strength and high corrosion resistance by vacuum brazing. The present invention provides an Al alloy brazing material, an Al alloy brazing sheet, and a brazing method for an Al alloy heat exchanger using the brazing material.

[0002]

2. Description of the Related Art For example, as shown in FIG. 1, a laminated evaporator has a passage structure composed of fins (1) and a brazing sheet forming refrigerant passages (3) and (3 '). Sheets (2), (2 ')
Are alternately laminated and assembled by brazing. In such an evaporator, as a fin material, an alloy to which Zn, Sn, In or the like is added is used in order to give a sacrificial effect to an Al alloy or an Al-Mn alloy.
And JIS 3003 alloy (A
It is generally used that the core material is 1-0.15 wt% Cu-1.1 wt% Mn) and both surfaces thereof are coated with an Al-Si-Mg brazing alloy.

FIG. 2 shows a serpentine type evaporator. This is assembled by brazing with fins (1) installed between the extruded multi-hole pipes (4) bent in a meandering shape, and connectors (5) and (5 ') attached to both ends of the extruded multi-hole pipes (4). ing. In such an evaporator, the fin material is made of Al alloy or Al-
A brazing sheet in which an alloy obtained by adding Zn, Sn, In, etc. to a Mn-based alloy is used as a core material and an Al-Si-Mg-based brazing alloy is coated is used. For extruded multi-hole tubes, JIS3003 is used.
Alloys, Al-Cu based alloys, or Al-Cu-Mn based alloys are used.

All of these are assembled by brazing by heating to a temperature of around 600 ° C. and brazing. As the brazing method, a vacuum brazing method, a flux brazing method, and a nocolock brazing method using a non-corrosive flux are used. And so on.

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, since fins have low thermal conductivity when they are made thin, a fin material of Al-Zr alloy having excellent thermal conductivity has been developed. However, since the fins have low strength, they tend to buckle during brazing. , The precipitate in the fin is re-dissolved to reduce the thermal conductivity of the fin, and it is necessary to add the alloying element to improve the strength of the member, but the addition of the alloying element lowers the melting point. ,
There is a problem such as melting during the brazing process of heating to a temperature near 600 ° C.

The inventors of the present invention have made earnest studies to solve these problems, and thought that it would be effective to lower the brazing heating temperature, and examined what temperature below to solve the above problems. However, it has been found that when 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 amount of Si added. The above three points will be described in more detail.

Most of the fin buckling is caused by the creep phenomenon of the fin at high temperature,
It was found that the temperature abruptly rises around 590 ℃ at higher temperatures. Therefore, at 585 ° C or lower, buckling due to this does 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. Therefore, if the temperature is 585 ° C or lower, the diffusion of wax will be small, and the buckling of the fins will be less likely to occur as a whole.

The thermal conductivity of the fin material to be brazed is lowered because the intermetallic compound precipitated in the Al alloy is re-dissolved during the brazing addition heat. 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 the strength, although elements added as a high-strength Al alloy include Cu, Mg, Si, etc., when used as a refrigerant passage constituent member, corrosion resistance and brazing property must be taken into consideration. When used as a fin, sacrificial effect, thermal conductivity and brazing property must be taken into consideration. Therefore, the number of elements whose addition amount can be increased for improving strength is limited, and specifically, 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.

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. In this method, since an Al-Zn alloy or Zn alloy containing 20% or more of Zn is usually used as a brazing material, there is a problem that the brazing material is easily corroded after brazing. not being used. Further, there is an alloy known as an Al alloy brazing alloy having a low melting point in the past (for example, JP-A-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. Furthermore, in vacuum brazing such as that relating to the present invention, Zn having a high vapor pressure almost evaporates at a temperature of 400 to 500 ° C., and the melting point of the brazing material cannot be lowered, so brazing at low temperature is impossible. Met.

[0011]

In view of this, the present invention has been made in view of the above.
The present invention is to develop an Al alloy brazing material for vacuum brazing, an Al alloy brazing sheet, and a method for manufacturing an Al alloy heat exchanger using the same, which can reduce the size and weight of the 1 alloy heat exchanger.

That is, the Al alloy brazing filler metal for vacuum brazing of the present invention comprises 6.0 wt% or more and 13.0 wt% or less Si, 1.2 wt.
% To 3.0 wt% Cu, 0.2 wt% to 2.0 wt% Mg, and 0.01 wt% to 0.5 wt% S
It is characterized by containing one or two of n and 0.01 wt% or more and 0.5 wt% or less of In, and the balance Al and unavoidable impurities.

The Al alloy brazing sheet for vacuum brazing of the present invention is obtained by clad on one side or both sides of an Al alloy core material using the above Al alloy as a brazing material.

According to the method for manufacturing an Al alloy heat exchanger of the present invention, when the Al alloy heat exchanger is manufactured by brazing, the above Al alloy brazing material is used and the temperature exceeds 570 ° C.
It is characterized in that vacuum brazing is performed at a temperature of ℃ or less.

Further, another method of manufacturing the Al alloy heat exchanger of the present invention is, when manufacturing the Al alloy heat exchanger by brazing, using the above Al alloy brazing sheet and exceeding 570 ° C. and 585 ° C. or less. It is characterized in that vacuum brazing is performed at the temperature.

Here, the alloy composition of the brazing filler metal of the present invention is 6.0.
contains wt% or more and 13.0 wt% or less Si, 1.2 wt% or more and 3.0 wt% or less Cu, 0.2 wt% or more and 2.0 wt% or less Mg,
Furthermore, 0.01 wt% or more and 0.5 wt% or less Sn, 0.01 wt% or more
A containing one or two kinds of In of 0.5 wt% or less
L alloy. The reason for the limitation will be described below.

Si lowers the melting point of the alloy, but its amount is
If it is less than 6.0 wt%, the melting point will not be sufficiently lowered and brazing will not be possible at temperatures below 585 ° C. Further, when the amount exceeds 13.0 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, it has a function of improving the strength of the alloy. Here, if the amount of Cu is less than 1.2 wt%, the effect of lowering the melting point and improving the brazing flow property is not sufficient, and the amount of Cu is
If it exceeds 3.0 wt%, the brazing potential becomes too noble, and the core material will be preferentially corroded, which will lower the corrosion resistance and also reduce the rolling and forming processability of the alloy, resulting in heat exchange. It becomes unsuitable as a brazing sheet for dexterous brazing sheets. Therefore, Cu should be 1.2 wt% or more and 3.0 wt% or less.

Mg has the effect of evaporating during brazing and improving the degree of vacuum by the getter action, and the action of destroying the oxide film by evaporation. If the content is less than 0.2 wt%, the above-mentioned action does not occur sufficiently and brazeability deteriorates.
On the other hand, when the temperature exceeds the range, the amount of the Mg-based oxide film increases conversely during the brazing heat and the brazing property deteriorates.

Further, in the brazing alloy containing Cu as in the present invention, there is a problem that the brazing potential becomes nobler than that of the core, and the core material is preferentially corroded. The addition of Sn and In lowers the brazing potential and makes the brazing potential less base than that of the core alloy to improve the corrosion resistance. However, if the amounts of Sn and In are less than 0.01 wt%, the effect of improving the corrosion resistance is not sufficient. Further, when the amount of Sn and In exceeds 0.5 wt%, the self-corrosion resistance of the braze is lowered and the rolling workability of the alloy is lowered, which makes it unsuitable as a brazing sheet for a heat exchanger.

Although the alloying elements of the brazing material of the present invention are as described above, the addition of Bi for the purpose of improving the brazing property does not impair the effects of the present invention. Further, if Fe as an unavoidable impurity is contained in an amount of 0.5 wt% or less, the effect of the present invention is not impaired, and the content of other elements is 0.05 wt.
% Or less, it may be contained.

In the present invention, the brazing alloy having the above composition is clad on one side or both sides of the core material to form a brazing sheet, and its coverage varies depending on the plate thickness of the member used and is about 2 to 20%. The alloy used as the core material of the brazing sheet is not particularly limited.
An alloy for brazing at a temperature in the vicinity of ° C (for example, a 1000 series alloy, a 3000 series alloy, or an alloy obtained by adding various elements to these alloys as a base) may be used as it is.

Next, in the present invention, the brazing temperature is higher than 570 ° C and lower than 585 ° C. This is because when the brazing temperature is 570 ° C. or lower, the brazing material of the present invention does not melt and cannot be brazed. Further, when the temperature exceeds 585 ° C, the thermal conductivity of the material is lowered and the fins are significantly buckled at high temperature. Further, an alloy having a low melting point or an alloy containing a large amount of Cu is used as a refrigerant passage constituent member. This is because it cannot be used. In addition,
By lowering the brazing temperature in this way, the electric cost as a brazing cost is reduced, and the life of the brazing furnace is extended.

In the manufacturing method of the present invention, the brazing conditions are such that the temperature is limited as described above, and the brazing method is limited to the vacuum brazing method. However, in the present invention, the process after heating is not particularly limited. Processes such as aging treatment and painting may be performed as is conventionally done.

[0025]

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

Example 1 A brazing sheet fin was prepared by combining a brazing material having the alloy composition shown in Table 1 and a core material. The plate thickness of the fins is 0.12 mm, and both are H14 temper with the brazing material clad on both sides of the core material by 10%. For these, the brazing heat was applied under the conditions of Table 2, and the buckling test, the tensile test, and the conductivity were measured. Buckling test is shown in Figure 3.
The amount of buckling after heating was measured by the test method shown in. The conductivity was measured by the double bridge method. Further, a corrugated brazing sheet fin and a JIS3003 alloy plate were alternately laminated in a core shape to prepare a mini core, and brazing heat was applied under the conditions of Table 2 to observe the fillet formation state. The results are shown in Table 2.

[0027]

[Table 1]

[0028]

[Table 2]

According to Table 2, the invention examples (1) to (6) are conventional examples.
Compared with (7) and (8), high temperature buckling resistance and conductivity are significantly improved, and brazing property is also good. In particular, in Example (2) of the present invention, even if a high-strength core material is used, the core material does not melt, so that not only high-temperature buckling resistance and conductivity but also strength is improved. On the other hand, the comparative example (9) using a high-strength alloy for the core material
At the brazing heat temperature of 00 ° C, the core material melted and buckled significantly, and the fins collapsed in the mini core. Furthermore, although Comparative Examples (10), (11), and (12) have improved high-temperature buckling resistance and conductivity, they are outside the alloy range of the brazing filler metal of the present invention, and the temperature of the brazing heat is 585 ° C or less. The brazing property is inferior because the brazing property cannot be obtained sufficiently.

Example 2 An Al alloy brazing sheet having a plate thickness of 0.5 mm was manufactured by combining a brazing material having a composition shown in Table 3 and a core material by a usual method. Both are brazing sheets with 15% brazing filler metal clad on both sides of the core material. These were subjected to brazing heat under the conditions shown in Table 4 and then subjected to a tensile test and a corrosion resistance test. Corrosion resistance test exposes only the central part of the surface of the brazing material, seals all other surfaces,
The CASS test (JISH8681) was performed for 336 hours, and the depth of pitting corrosion generated on the surface was measured by the depth of focus method using an optical microscope. The results are shown in Table 4.

[0031]

[Table 3]

[0032]

[Table 4]

Since the brazing sheets of Examples 1 to 3 of the present invention make the electric potential of the brazing material lower than the electric potential of the core material, they are superior in corrosion resistance to those of the conventional example 5. Further, since the brazing sheet of Inventive Example 4 does not melt when using the core material of the high-strength alloy as compared with the brazing sheet of Conventional Example 5, it is possible to improve the strength and has a higher corrosion resistance than that of Conventional Example 5. Are better.
On the other hand, in the brazing sheet of Comparative Example 6 using the high-strength alloy, the core material was melted at the heating temperature of 600 ° C., so that the corrosion resistance test could not be performed. In Comparative Example 7, since Sn or In was not added, the potential of the brazing material became more noble than the potential of the core material, and the core material was preferentially corroded to deteriorate the corrosion resistance. In Comparative Example 8 in which the amount of Cu is more than the range of the present invention, the electric potential of the brazing material becomes nobler than that of the core material as in Comparative Example 7 in which Sn and In are added, and the core material is Corrosion is preferentially corroded to deteriorate the corrosion resistance.

[0034]

As described above, when the heat exchanger is manufactured by using the brazing material of the present invention, the fins do not buckle during brazing, and the heat conductivity, strength and corrosion resistance of the members are improved. ,
The obtained heat exchanger can be reduced in size and weight and has a remarkable industrial effect.

[Brief description of drawings]

FIG. 1 is a perspective view of a partial cross section showing a laminated evaporator.

FIG. 2 is a side view showing a part of a serpentine type evaporator.

FIG. 3 is a side view showing a buckling test.

[Explanation of symbols]

 1 Fin 2 ', 2 Passage Sheet 3', 3 Refrigerant Passage 4 Extruded Multi-hole Pipe 5 ', 5 Connector 6 Jig

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C22C 21/00 C22C 21/00 J (72) Inventor Yoshihiro Kinoshita 1-1, Showa-cho, Kariya city, Aichi prefecture Address: Nihon Denso Co., Ltd. (72) Inventor Taketoshi Toyama 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (4)

[Claims] 1. Si of not less than 6.0 wt% and not more than 13.0 wt%, 1.2
One of the following: wt% to 3.0 wt% Cu, 0.2 wt% to 2.0 wt% Mg, 0.01 wt% to 0.5 wt% Sn, 0.01 wt% to 0.5 wt% In Alternatively, an Al alloy brazing material for vacuum brazing, characterized in that it contains two kinds and the balance is Al and unavoidable impurities. 2. The Al alloy brazing filler metal according to claim 1,
An Al alloy brazing sheet for vacuum brazing, characterized in that an alloy core material is clad on one side or both sides. 3. When manufacturing an Al alloy heat exchanger by brazing, vacuum brazing is performed at a temperature higher than 570 ° C. and lower than 585 ° C. using the Al alloy brazing material according to claim 1. And a method of manufacturing an Al alloy heat exchanger. 4. When manufacturing an Al alloy heat exchanger by brazing, vacuum brazing is performed at a temperature above 570 ° C. and below 585 ° C. using the Al alloy brazing sheet according to claim 2. And a method of manufacturing an Al alloy heat exchanger.