JPH07331372A - Aluminum alloy brazing sheet excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain an Al alloy brazing sheet excellent in corrosion resistance. CONSTITUTION:This Al alloy brazing sheet is prepared by cladding one side or both sides of a core material of Al alloy containing 0.03-<0.10% Si and 0.5-1.6% Mn with an Al alloy brazing filler metal containing one or two kinds among 7.0-11.0% Si, 1.0-7.0% Zn, and 0.01-0.10% In. If necessary, one or >=2 kinds-among 0.01-<0.5% Cu, 0.1-1.0% Mg, and 0.01-0.15% each of Cr, V, Ti, and Zr are incorporated into the above core material. By this method, an electric potential layer in which electric potential is low and increases with the approach to the inner part is formed on the surface of the core material, by which the progress of local corrosion deep into the inner part of the core material can be prevented and corrosion resistance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al alloy brazing sheet having excellent corrosion resistance, which is used as a component material for heat exchangers for automobiles.

[0002]

2. Description of the Related Art As a material for heat exchangers for automobiles,
Conventionally, a brazing sheet has been widely used in which an Al alloy such as JIS A3003 is used as a core material, and an Al-Si brazing material is clad to the core material. The brazing sheet is molded and brazed to produce a heat exchanger. ing. By the way, since this heat exchanger is used in a severe corrosive environment, it is required to have excellent corrosion resistance, but it cannot be said that the brazing sheet has sufficient corrosion resistance. Therefore, in the past, Z was used as the brazing material for brazing sheets.
Methods such as adding n and other components to give the wax a sacrificial anode effect, and adding cores and other components to increase the potential of the core and increase the corrosion resistance of the brazing sheet have been taken. There is.

[0003]

However, according to the above-mentioned conventional improvement method, although the corrosion resistance of the brazing sheet is improved to some extent, once local corrosion occurs in the core material, the local corrosion easily occurs. There is a problem that the core material progresses deep into the core material and a through hole is formed relatively early. The present invention has a basic object to solve the above problems, and provides an Al alloy brazing sheet having improved corrosion resistance by suppressing local corrosion occurring in the core material of the brazing sheet from deeply advancing inward. That is the purpose.

[0004]

In order to solve the above problems, in the present invention, the Al alloy brazing sheet of the first invention is, by weight%, Si: 0.03 to less than 0.10%, M
n: 0.5 to 1.6% Al alloy core material containing Si: 7.0 to 11.0% on both sides or one side, and further Z
It is characterized in that an Al alloy brazing material containing one or two of n: 1.0 to 7.0% and In: 0.01 to 0.10% is clad. In addition, the Al alloy brazing sheet of the second invention is, as a component of the Al alloy core material, in addition to the components of the first invention, further by weight%, Cu: 0.01 to.
Less than 0.5%, Mg: 0.1-1.0%, Cr, V, T
i, Zr: 0.01 to 0.15% each of one type or two or more types are contained.

[0005]

According to the present invention, the potential of the surface layer of the core material is appropriately lower than that of the inside due to the appropriate diffusion and penetration of Si from the brazing material, and the potential gradually increases from the surface to the inside. An ascending potential layer is obtained at the surface layer.
Further, the brazing filler metal contains at least one of Zn and In, and the potential is lowered. Corrosion progresses in a planar manner on the surface of the brazing filler metal or core due to the gradient potential layer and the base brazing filler metal. ,
The progress of the core material to the inside is suppressed. Next, the reasons for limiting the specific components of the brazing sheet of the present invention will be described.

(Core material) Si: 0.03 to less than 0.10% The potential of the Al-Mn alloy is minimized by containing about 0.3% of Si, but Si is heated by the heating during brazing. It is also supplied from the brazing material into the core material by diffusion. Considering this diffusion amount, the Si content in the core material needs to be less than 0.10% in order to make the potential of the core material surface layer moderately base. On the other hand, Si also contributes to the strength of the core material, so it is necessary to contain Si by 0.03% or more. Therefore, the Si content is limited to 0.03 to less than 0.10%. For the same reason as above, it is more desirable to limit the content to 0.04 to less than 0.08%.

Mn: 0.5-1.6% Mn precipitates as a compound to improve the strength of the core material and further improve the pitting corrosion resistance. In order to obtain the effect sufficiently, it is necessary to contain 0.5% or more, while 1.6
If it exceeds%, the workability is deteriorated, so the content is limited to the above range. Cu: 0.01 to Less than 0.5% Cu is contained in an amount of 0.01% or more as desired in order to increase the strength of the core material and further make the potential of the core material noble to an appropriate degree.
However, if it is contained excessively, the effect of lowering the potential of the core material surface layer portion due to Si diffusion will be reduced. Further excessive Cu
The inclusion makes the core material too noble, increases the potential difference from the brazing material, and causes the brazing material to corrode early, so that it becomes difficult to progress the corrosion in a planar manner. Therefore, the Cu content is set to less than 0.5%. For the same reason, it is more desirable to set the upper limit to less than 0.3%.

Mg: 0.1-1.0%, Cr, V, T
i, Zr: 0.01 to 0.15% each Mg, Cr, V, Ti, and Zr are optionally contained in order to improve the strength of the core material. In order to obtain this effect, it is necessary that each content be at least the lower limit, while if it exceeds the upper limit, the workability of the material will be impaired.

(Brazing material) Si: 7.0 to 11.0% Si is contained in order to lower the liquidus temperature of Al and to enhance the fluidity of the brazing material when it is melted. The Si content is selected in consideration of ensuring good fluidity, and is a content that diffuses into the core material during brazing to appropriately lower the potential of the core material. From these points, the Si content is limited to the above range.

Zn: 1.0 to 7.0%, In: 0.01
~ 0.10% Zn, In base the potential of the brazing filler metal and give a sacrificial anode effect. In addition, when brazing, a part thereof diffuses into the core material, which also has the effect of lowering the potential of the surface layer portion of the core material, and at least one of these is contained in the brazing material. In order to obtain these effects, it is necessary that the content is not less than the lower limit, while if it exceeds the upper limit, the self-corrosion property increases, so the content is set within the above range.

[0011]

EXAMPLE A core material and a brazing filler metal (cladding ratio of brazing filler metal of 10% each) having various combinations of the component compositions shown in Table 1 were used.
A brazing sheet having a thickness of 5 mm was prepared, a fluoride-based flux was applied to these brazing sheets, and heat treatment equivalent to brazing was performed at 600 ° C. for 5 minutes in a nitrogen gas atmosphere. Using these materials as test pieces, an acidic salt spray test was performed for 720 hours, and the maximum pitting depth after the test was measured. The results are shown in Table 2. From Table 2, it can be seen that the brazing sheet of the present invention material has a slight erosion, whereas the comparative material has deep corrosion and penetrates the material.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

As described above, according to the Al alloy brazing sheet of the present invention, Si: 0.0
Si: 7.0-1 on both sides or one side of an Al alloy core material containing 3 to less than 0.10% and Mn: 0.5 to 1.6%
1.0%, Zn: 1.0-7.0% and I
n: A containing 0.01 to 0.10% of one kind or two kinds
Since the 1-alloy brazing material is clad, the surface layer of the core material becomes partially baser than the inside, and local corrosion is prevented from proceeding to the inside of the core material. Therefore, if a heat exchanger or the like is manufactured using this brazing sheet as a component material, a product excellent in corrosion resistance can be obtained.

Claims (2)

[Claims] 1. Si: 0.03 to 0.10% by weight
Below, Mn: 0.5 to 1.6% on both sides or one side of the Al alloy core material containing Si: 7.0 to 11.0%,
Furthermore, Zn: 1.0-7.0% and In: 0.01-0.
An Al alloy brazing sheet excellent in corrosion resistance, characterized by being clad with an Al alloy brazing material containing 10% of one or two kinds 2. As a component of the Al alloy core material, further, by weight%, Cu: 0.01 to less than 0.5%, Mg: 0.1 to
1.0%, Cr, V, Ti, Zr: 0.01 to 0.1 each
The Al alloy brazing sheet having excellent corrosion resistance according to claim 1, which contains 5% of one kind or two kinds or more.