JPH0713319B2 - Fin material for copper heat exchanger and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a fin material for a heat exchanger made of copper, which is suitable for a heat exchanger used in a severe corrosive environment such as an automobile, and a manufacturing method thereof, and particularly as a fin. The corrosion resistance is improved and the fins can be made thinner without lowering the thermal conductivity.

[Problems to be Solved by Conventional Techniques and Inventions]

In recent years, as the weight of heat exchangers for automobiles has become lighter, the trend toward thinner wall thickness of fin materials for heat exchangers has increased. The decrease in heat dissipation due to corrosion wear has become a problem.

Generally, fin materials for heat exchangers are required to have corrosion resistance as well as thermal conductivity and strength.
If the fin material itself is alloyed by the addition of the second and third elements to have corrosion resistance to withstand salt corrosion, it will lead to a significant decrease in thermal conductivity, making it unsuitable as a fin material for heat exchangers. Become. Therefore, there is a demand for a fin material for a heat exchanger that has sufficient thermal conductivity even when it is made thin and that has excellent corrosion resistance in a harsh environment.

In such a situation, a fin material for a heat exchanger has been proposed in which a Zn diffusion layer is formed on the surface of a highly conductive Cu-based material, the inner core material is protected by a sacrificial anode, and the thermal conductivity is given to the core material. There is. However, there is a problem that Zn disappears due to the dezincification corrosion peculiar to Zn alloys, and the sacrificial anode effect of Zn cannot be maintained for a long period of time. However, the Zn diffusion layer formed on the surface is limited to about several μm on one side due to the balance with thermal conductivity, but if the dezincification corrosion of the Zn diffusion layer can be effectively suppressed and prevented, the corrosion resistance will be even better. It is possible to expect fin materials for heat exchangers, and it is possible to reduce the wall thickness. In order to suppress the dezincification peculiar to brass, it is necessary to add a third element effective in improving the corrosion resistance to the Cu-Zn diffusion layer to measure the corrosion resistance of the diffusion layer itself.

[Means for Solving the Problems]

In view of this, the present invention, as a result of studying the influence of additional elements on the effect of improving the corrosion resistance of the Cu-Zn diffusion layer formed on the surface of Cu or Cu alloy strip, found that the addition of Ni is suitable, As a result of further study, a fin material for a heat exchanger made of copper having excellent corrosion resistance and a manufacturing method thereof have been developed.

That is, in the fin material of the present invention, the surface of Cu or a Cu alloy strip is coated with a Zn-Ni alloy having a Ni content of 6 to 18 wt% and subjected to a heat diffusion treatment to form a Cu-Zn-Ni alloy layer on the surface side. , Underneath
It is characterized in that a Cu-Zn alloy layer is formed.

Further, the method for producing the fin material of the present invention is such that the surface of a Cu or Cu alloy strip is coated with a Zn-Ni alloy having a Ni content of 6 to 18 wt% by electroplating and then subjected to heat diffusion treatment or heat diffusion treatment. It is characterized by being rolled.

[Action]

According to the present invention, the surface of a Cu or Cu alloy strip is plated with a Zn-Ni alloy having a Ni content of 6 to 18 wt%, which has excellent corrosion resistance.
It reduces the dezincification corrosion of the alloy and protects the internal Cu or Cu alloy by the sacrificial anodic effect of Zn.
As the alloy plating bath, if the plating content is such that the Ni content in the plating film is 6 to 18 wt% and the plating conditions are, sulfate bath, chloride bath, sulfate and chloride mixed bath, sulfamic acid bath, etc. are all used. it can.

The Ni content of 6-18 wt% is about 10 wt% when the Ni content is 6 wt% or more and the γ-phase-based morphology with excellent corrosion resistance begins to occur.
%, The γ phase becomes almost single phase and the corrosion resistance is improved, but 6w
If it is less than t%, the phase in which Ni is solid-dissolved in Zn is the main component, so there is little or no improvement effect on corrosion resistance, or even if there is, there is a merit of Zn-Ni alloy plating using expensive Ni. This is because it is not alive. In addition, the reason why the amount is 18 wt% or less is
Even if the Ni content is increased more than this, the corrosion resistance is not further improved, and it is economically disadvantageous because the expensive Ni increases, so the Ni content is preferably 10 to 15 wt%. .

The heat diffusion treatment after the Zn-Ni alloy plating is performed with the plating layer and Cu or
The mutual diffusion with the Cu alloy strip strengthens the adhesion between the two, and the difference in the diffusion rate between Zn and Ni in Cu (Zn is
Faster than Ni), part of Zn is replaced with Cu while maintaining the morphology of the Zn-Niγ phase, and the surface side of the diffusion layer is made a highly corrosion resistant Cu-Zn-Ni alloy layer, and the lower layer is Cu- This is because the two diffusion layers, which are Zn alloy layers, allow the diffusion layers to have both a sacrificial anode effect and high corrosion resistance. Further, the rolling process improves the adhesiveness and the dimensional accuracy in combination with the heat diffusion, and improves the strength of the fin material by forming the plated layer into a processed structure. The effect of the present invention can be obtained by performing either the heat diffusion treatment or the rolling process first, but it is desirable to perform the rolling process in the final step.

〔Example〕

Heat-resistant copper strip containing 0.02 wt% Mg with a thickness of 0.065 mm (conductivity 95.5
% IACS) using the following plating baths (1), (2),
Using (3), (4), (5), (6), and (7), apply 2.4-μm thick Zn-Ni alloy plating on both sides, and
Heat-diffused for minutes, rolled to 0.036mm
Of fin material.

A corrosion test was performed on this, and the deterioration rate of the tensile strength was measured. The result was compared with the result of plating pure Zn with a thickness of 2.4μ, followed by heat diffusion treatment at 450 ° C for 1 minute, and then rolling it to a thickness of 0.036mm.
Shown in the table.

In the corrosion test, salt spray based on JIS Z 2371 was carried out for 1 hour, and then kept in a thermo-hygrostat at a temperature of 70 ° C. and a humidity of 95% for 23 hours, which was repeated 30 times.

Plating bath (1) NiSO ₄・ 6H ₂ O 300g / ZnSO ₄・ 7H ₂ O 80g / Na ₂ SO ₄ 100g / Al (SO ₄ ) ₃・ 14-18H ₂ O 30g / pH 2.5 Temperature 50 ℃ Current density 5A / dm ² plating bath (2) NiCl ₄・ 6H ₂ O 180g / ZnCl ₂ 80g / NH ₄ Cl 230g / H ₃ BO 20g / pH 5.0 Temperature 30 ℃ Current density 5A / dm ² plating bath (3) NiSO ₄・ 6H _{2 O 300g / ZnSO 4 · 7H 2} O 250g / Na 2 SO 4 100g / Al 2 (SO 4) 3 · 14-18H 2 O 30g / pH 2.0 temperature 50 ° C. current density 35A / dm ² plating bath (4) NiSO ₄・ 6H ₂ O 80g / ZnSO ₄・ 7H ₂ O 240g / Na ₂ SO ₄ 100g / Al ₂ (SO ₄ ) ₃・ 14-18H ₂ O 30g / pH 1.5 Temperature 50 ℃ Current density 5A / dm ² Plating bath (5 _{) NiSO 4 · 6H 2 O 50g} / ZnSO 4 · 7H 2 O 250g / Na 2 SO 4 100g / Al 2 (SO 4) 3 · 14-18H 2 O 30g / pH 1.5 temperature 50 ° C. current density 5A / dm ² plating Bath (6) NiSO ₄・ 6H ₂ O 300g / ZnSO ₄・ 7H ₂ O 20g / Na ₂ SO ₄ 100g / Al ₂ (SO ₄ ) ₃・ 14-18H ₂ O 30g / pH 1.5 Temperature 50 ℃ Current density 5A / dm ² plating bath (7) ZnSO ₄・ 7H ₂ O 250g / Na ₂ SO ₄ 100g / Al ₂ (S O ₄ ) ₃・ 14-18H ₂ O 30g / pH 1.5 Temperature 50 ℃ Current density 5A / dm ² As is clear from Table 1, the comparative fin material No. 7 in which pure Zn is plated, followed by heat diffusion and rolling, has a markedly deteriorated strength when dezincified, whereas the fin material No. 1 of the present invention ~
It can be seen that in Nos. 4 and 4, the dezincification is small and the strength deterioration is small.

On the other hand, a comparative fin material with a low Ni content in the plated film
It can be seen that in No. 5, the dezincification is remarkable and the strength is greatly deteriorated.
Also, the comparative fin material No. 6 whose Ni content exceeds the upper limit of 18 wt%
Does not show the effect of improving the corrosion resistance further,
Since a large amount is contained, it leads to an increase in cost and is disadvantageous.

〔The invention's effect〕

Thus, according to the present invention, while effectively improving the corrosion resistance of the copper heat exchanger fin material, it is possible to suppress the decrease in thermal conductivity low, improve the service life as a heat dissipation fin, and It has a remarkable industrial effect such as a reduction in thickness and weight.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Norimasa Sato, No. 500 Kiyotaki-cho, Nikko City, Tochigi Prefecture, Furukawa Electric Co., Ltd. Nikko Works (72) Sumio Susa, 1-1, Showa-cho, Kariya City, Aichi Japan Within Denso Co., Ltd. (72) Inventor Katsuhiko Takada 1-1, Showa-cho, Kariya City, Aichi Prefecture Within Nihon Denso Co., Ltd. (56) Reference JP 61-172690 (JP, A) JP 61-110794 (JP, A)

Claims (2)

[Claims] 1. A Ni content of 6 to 18 on the surface of Cu or Cu alloy strip.
For a copper heat exchanger characterized by forming a Cu-Zn-Ni alloy layer on the surface side by coating a wt% Zn-Ni alloy by heat diffusion treatment and forming a Cu-Zn alloy layer below it. Fin material. 2. A surface of a Cu or Cu alloy strip is coated with a Zn-Ni alloy having a Ni content of 6 to 18 wt% by electroplating and then subjected to heat diffusion treatment or heat diffusion treatment and rolling. A method of manufacturing a fin material for a copper heat exchanger, comprising: