JPH02228496A - Fin material for heat exchanger made of copper and production thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fin material for a copper heat exchanger and a method for manufacturing the same, which are suitable for heat exchangers for automobiles and the like used in severe corrosive environments. be.

[Prior art and problems to be solved by the invention] In recent years, as the weight of automobile heat exchangers has been reduced, there has been an increasing trend toward thinner fin materials for heat exchangers, and areas where chlorides such as NaCO are sprayed as snow melting agents are increasing. In coastal areas and coastal areas, the problem is that the heat dissipation performance deteriorates due to severe corrosion and wear of the fins due to chlorides.

In general, fin materials for heat exchangers have both corrosion resistance and thermal conductivity (
electrical conductivity) and strength, etc., such as Cu-N I corrosion-resistant alloys. If the fin material itself is alloyed by the addition of a third element to provide corrosion resistance against salt corrosion, the electrical conductivity will be significantly reduced, making it unsuitable as a fin material for a heat exchanger. Therefore, there is a demand for a fin material for a heat exchanger that exhibits sufficient electrical conductivity even when the thickness is reduced, and that also exhibits excellent corrosion resistance under severe circumstances.

Under such circumstances, a fin material for heat exchangers has been proposed in which a Zn diffusion layer is formed on the surface of a highly conductive Cu-based material to protect the internal core material as a sacrificial anode, and the core material has thermal conductivity. ing. However, this material has the problem that Zn disappears due to dezincification corrosion peculiar to Zn alloys, and the sacrificial anode effect of Zn cannot be maintained for a long period of time.

On the other hand, although this problem exists, the Zn diffusion layer formed on the surface is limited to a few micrometers per side due to conductivity, and if dezincification corrosion of the Zn diffusion layer can be effectively suppressed and prevented. Furthermore, we can expect a fin material for heat exchangers with excellent corrosion resistance, and it will also be possible to make the fins thinner.

In order to suppress the dezincing characteristic of brass, Cu-Zn
It is necessary to add a third element effective in improving corrosion resistance to the diffusion layer to improve the corrosion resistance of the diffusion layer itself.

[Means to solve the problem]

In view of this, the present invention has investigated the influence of additive elements on the corrosion resistance improvement effect of the Cu-Zn diffusion layer formed on the surface of Cu or Cu alloy strip, and has found that the addition of Ni is suitable, As a result of further studies, we developed a fin material for copper heat exchangers with excellent corrosion resistance and a method for manufacturing the same.

That is, one of the fin materials of the present invention is that the surface of a Cu or Cu alloy strip having a thickness a is coated with a Zn-Ni alloy having a total thickness b on both sides within a range that satisfies the following formula 0. It is characterized by:

Another fin material of the present invention is Cu or C having a thickness of a.
Zn-N with a total thickness of b on both sides is placed on the surface of the u alloy strip.
i alloy is coated within the range where the following formula 0 holds true, and a Cu-Z n-N 1 alloy layer is formed as a surface layer by heat diffusion treatment, and a Cu-Zn alloy layer is formed below it. This is a characteristic feature.

In addition, one of the manufacturing methods of the present invention is to apply electroplating to the surface of a Cu or Cu alloy strip having a thickness a so that the total thickness is b on both sides.
The Zn--Ni alloy is coated within a range that satisfies the following formula 0.

Furthermore, another manufacturing method of the present invention is to apply a Zn-Ni alloy with a total thickness of b on both sides by electroplating on the surface of a Cu or Cu alloy strip with a thickness a in a range where the following formula 0 holds. It is characterized in that after being coated with a heat-diffusion treatment or a heat-diffusion treatment and a rolling process.

b/a ~0.03-0.14 (2) In any of the above cases, the Zn--Ni alloy preferably has a Ni content of 6-18 wt%.

[Effect]

In the present invention, Zn-
When the total thickness of the Ni alloy is b and the thickness of the Cu or Cu alloy strip is a, the ratio of these, b/a, is 0.03.
Zn-N with excellent corrosion resistance in the range of ~0.14
Zn mainly consisting of the γ phase of i or consisting of a single γ phase
-It covers the Ni alloy. With this configuration, dezincification corrosion of the Zn alloy of the above material is reduced, and the sacrificial anode effect of Zn reduces internal Cu or C.
o It has the advantage of being able to protect the alloy.

A sulfate bath is a plating bath that can be used to coat such a Zn-Ni alloy.

Any bath such as a chloride bath, a mixed bath of a sulfate bath and a chloride bath, or a sulfamic acid bath may be used. ) Any of these plating baths may be used as long as the plating bath and plating conditions are as follows.

Furthermore, the reason why b/a is defined in the range as in the above formula 0 is good because if b/a is less than 0.03, the decrease in electrical conductivity is small, but this point is good, but it has little effect on improving corrosion resistance.
This is because the advantages of Zn-Ni alloy plating, which uses expensive Ni, are not utilized. Furthermore, b/a is 0.1
If it exceeds 4, it is sufficiently effective in improving corrosion resistance, but it leads to a significant decrease in electrical conductivity, which is especially noticeable in heat diffusion treated materials, making it unsuitable for automotive heat exchanger fin materials where electrical conductivity is important. This is because it becomes a commodity, and in addition, it is expensive
This is because the basis weight of i increases, which is economically disadvantageous. And preferably the value of b/a is 0.045 to 0,
A range of 10 is desirable.

In addition, the heat diffusion treatment after coating the Zn-Ni alloy coats the coating layer and C.
Mutual diffusion with u or Cu alloy strip strengthens the adhesion between the two, and zn, l! :The aim is to utilize the difference in the diffusion rate of NI (Zn is faster than Ni) to replace a portion of Zn with Cu while maintaining the Zn-Ni γ phase morphology. That is, by performing such treatment, the surface side of the diffusion layer is made into a highly corrosion-resistant Cu-Zn-Ni alloy layer, and the lower layer is made of Cu.
This is because by forming a two-layer diffusion layer with a Zn alloy layer, the diffusion layer has both an expensive sacrificial anode and high corrosion resistance. Further, the rolling process, in combination with heating and diffusion, improves adhesion, improves dimensional accuracy, and improves the strength of the fin material by forming the plating layer into a processed structure. Although the effects of the present invention can be obtained by performing either the heating diffusion treatment or the rolling process first, it is desirable to perform the rolling process in the final step.

In addition, the reason why the Ni content in the Zn-Ni alloy coated on the Co or Cu alloy strip is set to 6 to 18% is because the ZnNi alloy phase has a Nl content of 6% or more and is mainly composed of the γ phase, which has excellent corrosion resistance. This is because when the content is about 10% or more, it becomes almost a single γ phase, and the corrosion resistance is improved.

However, when the Ni content is less than 6%, the main phase is a solid solution of Ni in Zn, so there is little or only a slight effect on improving corrosion resistance, so Zn-Ni uses expensive Ni. This is because the benefits of using the alloy are not utilized. Moreover, even if the Ni content exceeds 18%,
Not only is it ineffective in further improving corrosion resistance, but it is also expensive.
This is because i increases, which is economically disadvantageous. Preferably, the Ni content is 10 to 15%.

〔Example〕

Next, embodiments of the present invention will be described.

<Example 1> The following No. I
Fin materials shown in Table 1 were prepared by applying Zn--Ni alloy plating to both surfaces using plating baths No. to No. and ■.

The electrical conductivity of these fin materials was measured, and the deterioration rate of tensile strength was measured after a corrosion test.
Table 1 also shows a comparison with the results of the deterioration rate of the electrical conductivity and tensile strength after the corrosion test, which were similarly measured for a conventional fin material plated with n.

The corrosion test was carried out in accordance with JIS Z2371 by spraying salt water for 1 hour and then holding it in a constant temperature and humidity chamber for 23 hours at a temperature of 70° C. and a humidity of 95%, which was repeated 30 times.

+11 Plating bath No. I Ni5O,・e H,0 ZnS　O4-”t　H2O azsO4 A&2 (SO,)! -14-18H,OH temperature Current density (2) Plating bath No. U N　i　S　O4・6　H2O ZnS01・7H2O N a 2 S 01 AQz(Sot)s-t4-tsHz.

H Temperature and current density (3) Plating bath No., m Ni5O, -6820 ZnS04- ”r H2O Naz SO+ All!! (S 04)j -114-18H203o
o#' 80g/1 100g/f 3ag/l 50 ℃ 5 A/dm" 3oog/l sog/j2 100g/f! 30g/A' 2.5 50 ℃ 5 A/d is 300g/I! 2oog# Loog /1 30g/l H Temperature current density (4) Plating bath No, IV NICQ2・6H20 nC0z NH,CQ 3BO H Temperature current density (5) Plating bath Ha, V NiSO4・6H20 ZnS04 ” 78zO azsO4 A172 (S 01) ff-14-18H20H Temperature current density (6) Plating bath No., Vl 2.5 50 °C 35 Aldm2 180g/1 80g/1 230g/12 20g/I! 5.0 30 ℃ 5 Aldm2 80g/1 240g/1 00gN 30g# 1.5 50 ℃ 5 Alrim" NI S Or " 6 Hto 50 g
/ 12ZnS Or” 7 N20 25
0 g/ItNa2S 04'
100g/I! A(7z(SQ, ns bow 4 1
．． 8H2030g/ ItpH1.5 Temperature 50'C Current Density 5 Aldm2(7) Plating Bath N
o, ■ NiS Or ・6 N20 300 g/l
ZnS 04-7 Hzo 20 g/IN
L2 S Or 100 g/IA
Qt(S 04)3 ・1418H2030g/It
pH 1.5 Temperature 50'C
Current density 5 Aldm2 (8) Plating bath No. ■ Zn5O+ 7HtO250g/(!NazS 0.
100 g/IAQz (SQ mountain-14
-tsHzo 30g/ip8
1.5 Temperature Current Density 50°C 10 A/dm” As is clear from Table 1, the conventional fin material No. 17 plated with pure Zn showed significant strength deterioration due to corrosion, whereas the present fin material No. 61 ~No. 11 shows that the strength deterioration is small and the corrosion resistance is improved.

Also, even if the Ni content is within the specified range, b/a is 0.0.
Comparative fin material No. 13 and No. 16 less than 3
Comparative fin material No. 12, which has a b/a exceeding 0.14, not only has no effect on improving corrosion resistance, but also has a large decrease in conductivity, and increases in cost due to the increased basis weight. increases and becomes disadvantageous.

Furthermore, even if b/a is within the specified range, the Ni content is 6%.
Comparative fin material No. 14 below had severe strength deterioration,
Comparative fin material No. with Ni content exceeding 18%,
In No. 15, no further improvement in corrosion resistance was observed, and in addition, the high Ni content led to an increase in cost, which was disadvantageous.

<Example 2> Next, a heat-resistant copper strip containing 0.02% Mg with a thickness of 0.065 mm (
After applying Z-row Ni alloy plating to both sides of IAC3) with a conductivity of 95.5%, heat diffusion treatment was performed, and after that, rolling was performed to obtain fin material No. 18 with a thickness of 0.0360101 as shown in Table 2. - No. 28 was produced.

We then measured the electrical conductivity of these fin materials, and
After carrying out the same corrosion test as in Example 1, the deterioration rate of tensile strength was measured, and these results were evaluated by applying pure Zn plating to a thickness of 24 br on the surface of the heat-resistant steel strip, and then performing a heat diffusion treatment. The results are also listed in Table 2 in comparison with the results measured for a fin material with a thickness of 0.036 mm produced by Comparative Method No. 34, which was then rolled.

As is clear from Table 2, Comparative method fin material No. 3, which was plated with pure Zn and then subjected to heating diffusion treatment and rolling processing.
In No. 4, dezincing was significant and strength deterioration was large. However, it can be seen that all of the fin materials No. 18 to No. 128 produced by the method of the present invention have less dezincing and less strength deterioration.

On the other hand, even if the b/a ratio is within the specified range, comparative method fin material No. 31 with an Nl content of less than 6% has severe strength deterioration, while comparative method fin material with a Ni content of over 18% Material No. 32 not only shows no greater improvement in corrosion resistance, but is disadvantageous in terms of cost due to its high Ni content.

Furthermore, even if the Ni content is within the specified range, the b/a ratio is 0.
．． Comparative method fin material No. less than 03, 30 and No.
Comparative method fin material No. 33 has a significant strength deterioration, and this ratio exceeds 0.14. Comparative method fin material No. 29 has little effect of further improving corrosion resistance, and furthermore, the conductivity decreases significantly (and the basis weight is large). This leads to cost increase and is disadvantageous.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to effectively improve the corrosion resistance of a fin material for a copper heat exchanger, and to suppress a decrease in thermal conductivity, making it possible to use such a fin material as a heat dissipation fin. This has significant industrial effects, such as improving the service life and making it possible to make the fin material thinner and lighter.

Claims (8)

[Claims] (1) For a copper heat exchanger, characterized in that the surface of a Cu or Cu alloy strip having a thickness a is coated with a Zn-Ni alloy having a total thickness of b on both sides within a range that satisfies the following formula: Fin material. b/a=0.03~0.14 (2) The fin material for a copper heat exchanger according to claim (1), wherein the Zn-Ni alloy has a Ni content of 6 to 18 wt%. (3) The surface of a Cu or Cu alloy strip with a thickness of a is coated with a Zn-Ni alloy with a total thickness of b on both sides within a range that satisfies the following formula, and then heated and diffused to form a surface layer. C
A u-Zn-Ni alloy layer is formed, and a Cu-Zn layer is formed below it.
A fin material for copper heat exchangers characterized by forming an alloy layer. b/a=0.03~0.14 (4) The fin material for a copper heat exchanger according to claim (3), wherein the Zn-Ni alloy has a Ni content of 6 to 18 wt%. (5) A copper product characterized in that the surface of a Cu or Cu alloy strip having a thickness a is coated with a Zn-Ni alloy having a total thickness b on both sides by electroplating within a range that satisfies the following formula: Method for manufacturing fin material for heat exchanger. b/a=0.03~0.14 (6) The method for manufacturing a fin material for a copper heat exchanger according to claim (5), wherein the Zn-Ni alloy has a Ni content of 6 to 18 wt%. (7) After coating the surface of a Cu or Cu alloy strip with a thickness of a with a Zn-Ni alloy with a total thickness of b on both sides by electroplating within a range that satisfies the following formula, heat diffusion treatment or A method for manufacturing a fin material for a copper heat exchanger, characterized by subjecting the material to heating diffusion treatment and rolling processing. b/a=0.03~0.14 (8) The method for producing a fin material for a copper heat exchanger according to claim (7), wherein the Zn-Ni alloy has a Ni content of 6 to 18 wt%.