JPH07278710A - Al brazing sheet - Google Patents

Abstract

PURPOSE:To produce an Al brazing sheet good in corrosion resistance and high in strength, in a core material in which one side is coated with a brazing filler metal and the other side with a sacrificial material by forming the core material, brazing filler metal and sacrificial material respectively of Al alloys having a specified compsn. CONSTITUTION:At the time of forming an Al brazing sheet of a core material, a brazing filler metal applied on one side of the core material and a sacrificial material applied on the other side of the core material, as the brazing filler metal, an Al-Si alloy is used. Moreover, as the core material, an Al alloy contg., by weight, 0.05 to 1.2% Si, 0.05 to 0.8% Fe, 0.1 to 1.0% Cu, 0.3 to 1.5% Mn, and the balance Al with inevitable impurities is used. As the sacrificial material, an Al alloy contg. 0.3 to 0.8% Si, 0.1 to 4.0% Mg, 0.1 to 0.5% Cu, and the balance Al with inevitable impurities is used. Thus, the Al brazing sheet excellent in corrosion resistance and furthermore having high mechanical strength can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al brazing sheet coated with a sacrificial material for the purpose of improving corrosion resistance, which is used in a radiator for automobiles and the like.

[0002]

2. Description of the Related Art As shown in FIG. 1, an automobile radiator, which is a kind of heat exchanger, usually comprises a tube 2 for passing cooling water, a fin 1 for heat radiation, a header plate 3, a resin tank 4 and the like. . Conventionally, Cu-based metal was often used for the members such as the tubes 2 and the fins 1, but in recent years, lightweight Al-based metal has been used in many cases in place of this. The above-mentioned members are usually joined by brazing in many cases, and the manufacturing method in this case is usually a method in which the tube 2, the fins 1, the header plate 3, etc. are first made of an Al brazing sheet and then brazed after assembling. . The Al brazing sheet is a sheet-shaped A
A core material made of an 1-alloy is coated (or clad) with a brazing material having a melting point lower than that of the core material (also a Al alloy).

Since the outer surface of the tube is to be brazed, the tube 2 is an electric resistance welded tube obtained by rolling and brazing an Al brazing sheet so that the brazing material is on the outer periphery. By the way, since the cooling water flows into the tube 2 during the use of the radiator, the inner surface of the tube 2 is easily corroded by the cooling water. In the case of the Cu-based metal tube, this was not a serious problem, but in the case of the Al-based metal, corrosion easily progresses from the corroded portion of the surface in the depth direction, and thus the tube 2
However, there is a problem in that the holes may penetrate due to corrosion on the inner surface of the steel, which may lead to leakage of cooling water.

For this reason, in recent years, for the purpose of improving the corrosion resistance of the tube 2, the inner surface of the tube 2 through which the cooling water passes has a potential lower than that of the core material (natural electrode potential is lower than that of the core material) Al alloy (sacrificial material). ) Is used. That is, the sacrificial material is preferentially corroded, which delays the progress of corrosion in the depth direction of the core material below the sacrificial material.
Although such a tube manufacturing method is used, a sacrificial material (an Al-Zn alloy having a natural electrode potential lower than that of the core material is often used) is usually provided on the surface opposite to the surface coated with the brazing material. The pipe is coated, rolled so that the sacrificial material side is the inner surface, and electric-welded to produce a tube.

[0005]

In recent years, there has been a strong demand for reducing the size and weight of radiators, and the members constituting the radiator, such as the tubes 2 and the fins 1, are becoming thinner and thinner. However, as a matter of course, the thinner the wall thickness, the shorter the formation time of the through hole due to corrosion. Therefore, it has been desired to improve the corrosion resistance of the member constituting the radiator. Especially in the case of a tube, cooling water leaks when the through hole is open, which is serious. For this reason, conventionally, an Al brazing sheet in which corrosion of the core material is delayed by the sacrificial effect of the sacrificial material has been used.

As a matter of course, the thicker the sacrificial material, the longer it takes to elute the corrosion, which is desirable. However, if the sacrificial material is thick, the tube 2 itself can be made even if the core material is thin. Does not mean that it has been made thinner. In order to obtain a sufficient sacrificial effect even if the sacrificial material is thin, it is necessary to improve the corrosion resistance (self-corrosion resistance) of the sacrificial material itself and extend the time until the corrosion elution. Naturally, it has also been desired to improve the corrosion resistance of the core material itself.

On the other hand, in order to make the core material thinner, it is necessary to improve the strength of the core material itself, but the strength of the sacrificial material cannot be ignored. Although the mechanical strength of the tube 2 particularly affects the strength of the core material constituting the Al brazing sheet,
It has been desired to improve the strength of the sacrificial material in order to compensate for the thinning of the core material.

However, there have been the following difficulties in improving the strength of the core material and the sacrificial material. First, the core material will be described. Conventionally, the core material needs to be a material that does not melt in the brazing process and does not significantly deteriorate in characteristics. Therefore, conventionally, the core material is made of Si, Mn, or C.
Al alloys containing u, Ti, Fe, Mg, etc. were often used. In order to improve the strength of the core material, for example, a method of increasing the amount of Mg, Si, Cu or the like contained in the core material can be considered. However, if Mg and Si are increased, Mg ₂ Si precipitates in the crystal grain boundaries in the core material during the brazing process, and grain boundary corrosion easily occurs, so that the corrosion resistance of the core material deteriorates. Also, if the amount of Mg contained in the core material is increased,
There is also a problem that Mg diffuses into the brazing material during the brazing process, reacts with the non-corrosive flux used in the brazing process, and deteriorates the brazing property.

Further, when Cu and Si contained in the core material are increased, Cu ₂ Al is added to the crystal grain boundaries in the core material in the brazing process.
Are precipitated and grain boundary corrosion easily occurs. In addition, the core material is Cu
If a large amount of Si or Si is contained, Cu in the core material in the brazing process
And Si diffuse into the Al-Zn alloy, which is a sacrificial material, and the natural electrode potential of the sacrificial material increases in the diffused portion, resulting in a decrease in potential difference from the core material and deterioration of the function as a sacrificial material. Occurs. As a countermeasure, Z contained in the sacrificial material
A possible method is to increase the amount of n to increase the potential difference from the core material. However, in this method, since the natural electrode potential with respect to the core material is lowered, the strength of the sacrificial material is reduced, and the natural electrode potential becomes too low, which causes a problem that the corrosion of the brazing material itself is accelerated.

Next, the sacrificial material will be described. Usually, the sacrificial material is thinner than the core material, but it is required to improve its strength as described above. As a method therefor, for example, a method of adding a large amount of Si to a conventional sacrificial material (Al-Zn alloy) can be considered. However, if the amount of Si is increased, the melting point of the sacrificial material is lowered, and there is a risk of melting in the brazing process.

Alternatively, a method of increasing the strength of the sacrificial material by reducing the amount of Zn contained in the sacrificial material can be considered. However, since Zn is added in order to lower the potential of the natural electrode so that the sacrificial material sacrifices the core material and is preferentially corroded, it is important to reduce the Zn content to diminish the sacrificial effect. There is no.

[0012]

SUMMARY OF THE INVENTION The present invention has been made as a result of intensive studies in view of the above circumstances, and its purpose is to provide Al having excellent corrosion resistance and high mechanical strength at the same time.
It aims to provide a brazing sheet. That is, the present invention is an Al brazing sheet comprising a core material, a brazing material coated on one surface of the core material, and a sacrificial material coated on the other surface of the core material. The brazing material is made of Al-Si alloy, and the core material is Si0.0
5 to 1.2 wt%, Fe 0.05 to 0.8 wt%, Cu
0.1 to 1.0 wt%, Mn 0.3 to 1.5 wt% and an Al alloy composed of the balance Al and unavoidable impurities, and the sacrificial material is Si 0.3 to 0.8 wt%, M
This is an Al brazing sheet made of an Al alloy containing g 0.1 to 4.0 wt% and Cu 0.1 to 0.5 wt% and the balance Al and inevitable impurities.

Further, Mg of 0.01 to 0.2 w is added to the core material.
Al brazing sheet containing t% or / and Ti 0.03 to 0.2 wt%, and further Z to the core material.
r0.03 to 0.3 wt% or / and Cr0.03
Provide an Al brazing sheet containing ˜0.3 wt%.

Further, the sacrificial material contains Zn 0.4 to 4.0 w.
Provided is an Al brazing sheet containing t%, and an Al brazing sheet containing 0.3 to 1.6 wt% of Mn in the sacrificial material.

[0015]

The core material of the Al brazing sheet of the present invention is Si0.05-1.2wt%, Fe0.05-0.8.
wt%, Cu 0.1-1.0 wt%, Mn 0.3-1.
Since it contains 5 wt%, it has high strength.

Of the elements contained above, Mn, Si, and Mn
And Fe, and Fe and Si each form an intermetallic compound, which contributes to improving the strength of the core material. Cu has the effect of forming a solid solution in the Al alloy forming the core material to improve the strength and also increasing the natural electrode potential of the core material. These contents will be described below. First, regarding the Si content, 0.05 to 1.
2 wt% is good. This is because if it is less than 0.05 wt%, it hardly contributes to the improvement of strength, and if it exceeds 1.2 wt%, the melting point of the core material is lowered, and the core material may be melted in the brazing process. Further, if it exceeds 1.2 wt%, Si diffuses into the sacrificial material by about 0.8 wt% and deteriorates the corrosion resistance of the sacrificial material. The characteristically desirable Si content is 0.6 to 0.8 wt%.

Next, the Fe content is 0.05 to 0.8 wt.
% Is good. If it is less than 0.05 wt%, the contribution to the improvement of strength is poor. On the other hand, if it is added in excess of 0.8 wt%, the crystallized substances produced during casting of the core material become huge and the recrystallized grain size in the brazing process becomes small. It becomes easy to diffuse into the inside of the steel, resulting in deterioration of brazing property. Fe content is 0.2 to 0.4 wt% which is particularly desirable.

Mn forms an intermetallic compound with Si or Fe to improve the strength, but its content is 0.3 to 1.5 wt.
% Is good. This is because if it is less than 0.3 wt%, the contribution to the improvement of strength is poor, and if it exceeds 1.5 wt%, the workability of the core material is deteriorated.

The Cu content is preferably 0.1 to 1.0 wt%. If it is less than 0.1 wt%, the solid solution contributes little to the improvement in strength. Further, addition of Cu has the effect of increasing the natural electrode potential of the core material, but if it is less than 0.1 wt%, this effect is poor. On the other hand, if the content exceeds 1.0 wt%, a large amount of Cu ₂ Al is generated in the crystal grain boundaries in the core material during the brazing process to deteriorate the corrosion resistance of the core material, and Cu diffuses into the sacrificial material during the brazing process. It will be easier. When a large amount of Cu diffuses in the sacrificial material,
This is not desirable because the natural electrode potential of the sacrificial material becomes high.

In addition to the above core material, Mg of 0.01 to
0.2 wt% or / and Ti 0.03 to 0.2 wt
%, It is expected that the added Mg and Ti contribute to the improvement of strength. Mg forms a solid solution in the Al alloy forming the core material to improve the strength, and also forms an intermetallic compound with Si to improve the strength. Its content is 0.01wt%
When it is less than 0.2%, the contribution to the improvement of strength is poor, and when it exceeds 0.2% by weight, it reacts with the non-corrosive flux in the brazing step, and the brazing property deteriorates. Ti has a function of a refining agent at the time of casting of the core material, and if it is less than 0.01 wt%, its function is poor, and if it exceeds 0.2 wt%, workability such as rolling of the core material deteriorates.

Zr 0.03 to 0.3 wt% or / and Cr is added to the core material containing Si, Fe, Cu and Mn and Mg or / and Ti in the above contents.
When 0.03 to 0.3 wt% is included, improvement in strength due to Zr or Cr can be expected. Zr and Cr are Al ₃ Zr and A
It forms a fine intermetallic compound such as l ₃ Cr to improve the strength. The content is preferably 0.03 wt% or more,
If it is less than that, there is little contribution to the improvement of strength. On the other hand, 0.3w
If it exceeds t%, casting cracks are likely to occur during casting of the core material, so the content is preferably 0.03 to 0.3 wt%.

Next, the sacrificial material of the Al brazing sheet of the present invention will be described. The sacrificial material is coated on one surface of the core material and has a role of suppressing the corrosion of the Al brazing sheet from proceeding in the depth direction. The sacrificial material in the present invention includes Si 0.3 to 0.8 wt% and Mg 0.1 to
It contains 4.0 wt% and Cu 0.1-0.5 wt%. Si dissolves in the sacrificial material and contributes to the strength improvement. Its content is preferably 0.3 to 0.8 wt%, and if it is less than 0.3 wt%, it does not contribute much to the improvement of strength, and if it exceeds 0.8 wt%, the corrosion resistance of the sacrificial material will deteriorate and the melting point will decrease. The risk of melting in the application process increases, which is not desirable.

Mg forms a solid solution in the sacrificial material to improve the strength, and when the core material contains more Si than the sacrificial material, S that diffuses from the core material in the brazing step.
i and Mg ₂ Si are formed to suppress wide diffusion of Si entering from the core material into the sacrificial material. Further, Mg ₂ Si has a lower natural electrode potential than the Al alloy which is the sacrificial material, and promotes the sacrificial effect of the sacrificial material. The content is 0.1-4.
0 wt% is preferable, and if it is less than 0.1 wt%, the contribution to the improvement in strength is poor, and the contribution to the suppression of the diffusion of Si is poor. On the other hand, when it exceeds 4.0 wt%, Mg diffuses into the core material, Mg ₂ Si is generated in the core material, and the grain boundary corrosion thereof deteriorates the corrosion resistance.

Cu contributes to the improvement of strength by forming a solid solution with the sacrificial material. The content is preferably 0.1 to 0.5 wt%.
If it is less than 0.1 wt%, it hardly contributes to the improvement of strength, and 0.5
If it exceeds wt%, the natural electrode potential of the sacrificial material increases and the sacrificial effect decreases.

With the above contents, Si, Mg and C
When Zn is further added to the sacrificial material containing u, the solid solution of Zn lowers the natural electrode potential of the sacrificial material and enhances the sacrificial effect. Its content is preferably 0.4 to 4.0 wt%,
If it is less than 4 wt%, the improvement of the sacrificial effect is insufficient and 4.0 w
If it exceeds t%, the self-corrosion resistance of the sacrificial material becomes too poor.

The sacrificial material containing Si, Mg, Cu and Zn in the above-mentioned contents has high strength and is highly effective as a sacrificial material. In addition to improving the self-corrosion resistance of the sacrificial material. It is considered that this is because the adverse effect of Fe, which is liable to be contained as an unavoidable impurity in a small amount in the Al alloy, is reduced by the addition of Mn and the strength is improved.

The effects of adding Mn are presumed to be as follows. In general, Fe is easily contained as an impurity in an Al alloy as an industrial material, and it is difficult to remove Fe contained in a trace amount from the viewpoint of cost. And this Fe is Al ₃ Fe in the sacrificial material (Al-Zn alloy).
It is known that the self-corrosion resistance of the sacrificial material deteriorates due to corrosion in the vicinity of the precipitates and the like. It is considered that the effect of Fe can be improved by adding Mn. The mechanism is that Mn is Al-Mn- in the sacrificial material.
Fe-based precipitates are formed, Fe diffusion is suppressed, and Al ₃
It can be presumed that the precipitation of Fe and the like is suppressed. Further, the effect of improving the strength of the sacrificial material can be expected by dispersing the Al-Mn-Fe-based precipitates described above. In addition, industrial Al
Usually, Fe, which is unavoidably mixed as an impurity in the material, is preferably less than 0.7 wt%.

However, the amount of Mn added is preferably 0.3 to 1.6 wt% in terms of the effect of improving the self-corrosion resistance. If less than 0.3 wt%, this effect is insufficient, and
When the content exceeds wt%, the workability is deteriorated, and the sacrificial material may be cracked when rolled to form an electric resistance welded pipe.

The brazing material of the Al brazing sheet of the present invention is not particularly limited, but JIS 4045
Usual brazing materials such as alloys can be used.

[0030]

【Example】

Inventive Examples, Comparative Examples and Conventional Examples Tables 1 to 3 show the compositions of the core material and the sacrificial material. Brazing material is J
IS 4045 alloy. A core material, a sacrificial material, and a brazing material having the compositions shown in the table are separately cast and homogenized (600
(° C x 9 hours), and then clad-roll (590 ° C) a sacrificial material on one side of the core material and a brazing material on the other side of the core material, and further hot-rolling and cold-rolling the thickness to 0.3 mm. From this, an Al brazing sheet was manufactured by subjecting this to heat treatment of JIS H14 tempering. The sacrificial material, core material, and brazing material have clad rates of 10%, 77%, and 13%, respectively.

In order to examine the formability of the produced Al brazing sheet, rolling was carried out under the same conditions as in the case of producing an electric resistance welded tube. As a result, in Comparative Example No. 77, the sacrificial material cracked, and in No. 89, the core material cracked. Next, brazing and heating were performed on the examples of the present invention, the comparative examples, and the conventional example excluding the comparative examples No. 77 and 89.
Brazing heating is performed with non-corrosive flux (KF-Al
The F ₃₎ with respect to the liquid (water suspended materials mixed in water flux was applied to 3 wt% equivalent) to braze the side of the Al brazing sheet was conducted by heating of 600 ° C. × 3.5 minutes in a nitrogen atmosphere .

Among the comparative examples, No 71, 72, 78, 79
No.74, 81, 8 sacrificial material in brazing heating
In No. 8, the core material was melted by heating by brazing. Except for these, examples of the present invention, comparative examples, and conventional examples were subjected to a corrosion resistance test after heating for brazing and leaving them in the room temperature atmosphere for 7 days. Corrosion resistance testing exposes only test portions, other portions covered with Teflon tape, corrosion test _{^{(Cl - 100ppm, CO 3 2-}} 100pm, SO 4 2-, Cu 2+ 10ppm
Was immersed in the corrosive liquid of 8 ° C. for 8 hours and room temperature for 16 hours, and the test was repeated for 4 months. After the corrosion resistance test, the corrosion product in the corroded portion was removed with a phosphoric acid-chromic acid solution, and then the corrosion holes were observed with an optical microscope. The depth of the holes was measured by the depth of focus method. Moreover, after cutting at the hole and polishing the cut surface, the presence or absence of grain boundary corrosion was examined. In Tables 4 to 6, the depth of the maximum hole (when the maximum hole has penetrated, it is described as penetration), and when the intergranular corrosion was observed, it was described as having the intergranular corrosion.

Further, the natural electrode potentials (core material and sacrificial material) of the Al brazing sheet subjected to the brazing heating (not subjected to the corrosion test) were measured. Measurement method is 5% NaCl
In an aqueous solution, measurement was performed using a saturated calomel electrode as a reference electrode. Also brazed and heated (not tested for corrosion)
The tensile strength of the Al brazing sheet (according to JIS No. 5 test piece) was also measured. The above results are shown in Tables 4-6.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

[0039]

[Table 6]

As is clear from Tables 4 to 6, all the inventive examples had higher tensile strength than the conventional examples. In addition, none of the holes penetrated due to corrosion. On the other hand, in the conventional example, the maximum hole depth was equivalent to that of the present invention, but the tensile strength was smaller than that of the present invention. Further, although some of the comparative examples have high tensile strength, all of them have the maximum pores penetrating them. From Tables 4 to 6, it is clear that the inventive examples have high tensile strength and excellent corrosion resistance.

[0041]

[Effect] As described above, the Al brazing sheet of the present invention has high mechanical strength and corrosion resistance and excellent characteristics, and is highly reliable, and promotes weight reduction of automobile radiators, etc. It makes a significant contribution.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view showing a main part of a vehicle radiator.

[Explanation of symbols]

 1 fin 2 tube 3 header plate 4 resin tank

Claims (5)

[Claims] 1. An Al brazing sheet comprising a core material, a brazing material coated on one surface of the core material, and a sacrificial material coated on the other surface of the core material. The brazing material is an Al-Si alloy, and the core material is Si0.0
5 to 1.2 wt%, Fe 0.05 to 0.8 wt%, Cu
It is an Al alloy containing 0.1 to 1.0 wt% and Mn 0.3 to 1.5 wt% and the balance Al and unavoidable impurities, and the sacrificial material is Si 0.3 to 0.8 wt% and Mg.
An Al brazing sheet which is an Al alloy containing 0.1 to 4.0 wt% and Cu 0.1 to 0.5 wt% and the balance Al and inevitable impurities. 2. The core material contains 0.01 to 0.2 wt% of Mg.
The Al brazing sheet according to claim 1, further containing 0.03 to 0.2 wt% of Ti and / or Ti. 3. The core material is Zr 0.03 to 0.3 wt%
The Al brazing sheet according to claim 2, further comprising 0.03 to 0.3 wt% of Cr and / or Cr. 4. The sacrificial material contains 0.4 to 4.0 wt% Zn.
The Al brazing sheet according to claim 1, 2 or 3, which comprises: 5. The sacrificial material contains 0.3 to 1.6 wt% of Mn.
The Al brazing sheet according to claim 4, which comprises: