JPH03291344A - Copper alloy for heat exchanger header plate - Google Patents

Abstract

PURPOSE:To obtain a copper alloy for a heat exchanger header plate excellent in stress corrosion cracking resistance, strength and workability by regulating the size distibution of a copper alloy having a specified compsn. constituted of Zn Sn, Si and Cu into a specified one. CONSTITUTION:This copper alloy for a heat exchanger header plate contains, by weight, 5 to 30% Zn, 1 to 5% Sn and 0.25 to 3.0% Si, furthermore contains, at need, total 0.05 to 5% of one or more kinds among <=0.1% P, <=3% Ni, <=2% Al, <=2% Mn, <=1.5% Zr and <=3% Mg and the balance Cu with inevitable impurities as well as has 20 to 80mum grain size. The alloy is excellent in stress corrosion cracking resistance and has sufficient strength and workability. The above grain size distribution can be controlled by heat treatment after rolling. By using this alloy, a heat exchanger in which the thinning of sheet thickness is permitted and having high capacity and high reliability can be obtd. at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a copper alloy for heat exchanger header plates that has excellent stress corrosion resistance.

[Conventional technology]

Conventionally, copper alloys, which have excellent heat dissipation and workability, have been mainly used as heat exchanger materials. As shown in Figure 1, the structure of a heat exchanger, such as an automobile radiator, consists of a core (3) consisting of a tube (1) through which a cooling medium flows and fins (2) that dissipate heat. A tank (
5) is attached, and the connection between the tank (5) and header plate (4) is as shown in the figure. This is done by caulking with a caulking plate (8) such as the like through an elastic sealing material (9).

In recent years, in order to reduce the weight and cost of heat exchangers, plastic tanks are used for the tanks, and the tank and header plates are connected directly by bending the periphery of the header plate instead of using caulking plates such as stainless steel. A method of caulking or press-fitting a claw part provided on the tank into a locking part of the header plate is adopted.

[Problem to be solved by the invention]

In a heat exchanger with such a structure, there is stress acting on the header plate due to caulking or press-fit locking, the external environment such as polluted air, and long-life coolant (LLC).
) has the disadvantage that stress corrosion (SCC) tends to occur on the header plate due to the corrosive action of the cooling water. In particular, when plastic tanks are used, corrosion tends to be accelerated due to the gap structure between the elastic sealing material and the header plate, and SCC tends to occur easily, so materials with excellent SCC resistance have been required.

In order to solve these problems, improved brass to which alloying elements such as P, Sn, AA', Si, and Zr are added for conventional header plates has been proposed in JP-A-60194033 and JP-A-61-542. Proposed. In addition, a header plate in which a corrosion-resistant layer of Cu, Ni, solder, etc. is formed on at least one side of the header plate is known as
This is proposed in Publication No. 86. It is also known that the SCC susceptibility of Cu-Zn alloys can be reduced by reducing the amount of Zn; for example,
No. 91 discloses a header plate in which at least one surface is coated with red copper containing a small amount of Zn.

However, as a header plate, it is difficult to cause SCC due to external and internal environments, has appropriate strength as a structural material, has excellent workability for press molding, and also has a property that inhibits solderability with tubes. Therefore, it is essential that it can be mass-produced at low cost as an industrial material.

However, although the above-mentioned method of reducing the amount of Zn improves SCC resistance, it has the drawback of decreasing strength and workability. In order to overcome this drawback, there is a method of composite coating with cladding or the like, but the composite coating increases the number of steps, reduces productivity, and increases costs, which is a problem. Furthermore, the method of improving SCC resistance by adding the above-mentioned alloying elements is simple, but it does not avoid deterioration of workability, deterioration of corrosion resistance due to the appearance of β phase, deterioration of solder jointability, etc., and the manufacturing cost increases. This also limits the type and amount of added elements.

As described above, the known methods cannot satisfy the various characteristics required of the header plate in a well-balanced manner, and have not been used industrially.

[Means to solve the problem]

As a result of a detailed investigation and analysis of the above phenomenon, the present invention found that although conventional header plates are resistant to external environments such as ammonia environments, LLC used as a cooling medium is particularly susceptible to mutual interaction such as heat and oxygen in real environments. It has been found that SCC is likely to occur in the environment of LLC that has been altered by the action. In other words, we found that the conventional SCC resistance evaluation alone was insufficient for header plate materials, and in addition, as a result of intensive research, we developed a new We have developed a copper alloy for heat exchanger header plates.

That is, the Zn content of the alloy of the present invention is 5 to 30 wt%.

Snl~3wt% and SiO,05~3.0wt
%, the balance consists of Cu and unavoidable impurities, and the crystal grain size is 20 to 80 μm. Another alloy of the present invention is Zn5 to 30 vf%, S
nl ~5v1% and S i O,05~3.0wt%
Contains P (1, Iwt% or less, Ni3t1% or less.

Al2wt% or less, Mn2wt% or less, Zr 1
, 5W 1% or less, Mg 5v 1% or less, a total of 0.05 to 3 wt% of one or more types (hereinafter wt% is %)
), the remainder being Cu and unavoidable impurities, and having a crystal grain size of 20 to 80 μm.

[For production]

The present invention is made of an alloy having the above composition, and the addition of Zn, Sn, and Si is to provide sufficient strength and SCC resistance, and the reason why the Zn content is limited to 5% to 30% is that the Zn content is limited to 5% to 30%. If it is less than 30%, the strength and workability will be insufficient, and if it exceeds 30%, although the strength and workability are excellent, the SCC resistance will decrease. The Sn content was limited to 1 to 5% because if it is less than 1%, the strength improvement effect is insufficient and the SCC resistance against LLC is insufficient, and if it exceeds 5%, the strength is improved but the resistance is insufficient. This is because the SCC property becomes saturated, the cost of raw materials increases, and the material becomes unsuitable as an industrial material.

The reason why the Si content was limited to 0.05 to 3% was 0.05%.
If it is less than %, the improvement in strength is insufficient and the conventional SCC resistance against ammonia is insufficient. 3%
If it exceeds this value, the processability will be insufficient and it will have no industrial meaning.

Next, the addition of P, Ni, AI, Mn, Zr, and Mg
In particular, the addition of P, Ni, Mn, and Zr has a large strength-improving effect, and also suppresses SCC from the external environment.
g is for suppressing SCC on the LLC side. And 2
011% or less, N43% or less, A12% or less.

The reason why any one or more of Mn is 2% or less, Zr is 1.5% or less, and Mg is 3% or less is limited to a total of 0.05 to 5% because less than 0.05% improves strength and SCC resistance. This is because the effect is so small that even if it is added in excess of 5%, the effect will be saturated.

Furthermore, the reason why the crystal grain size is set to 20 to 80 μm is to provide sufficient workability without compromising SCC resistance and strength. If it is less than 20 μm, the strength will improve but the workability will be insufficient, and it will be difficult to process during press forming. Cracks may occur, 8
This is because if the length exceeds 0.11 m, molding is possible, but roughness is likely to occur, resulting in frequent appearance defects. In order to obtain a grain size of 20 to 80 μm, the alloy having the above composition may be adjusted to the thickness of the product size by heat treatment after rolling.

The present invention has a crystal grain size of 20 to 80 for the alloy having the above composition.
By using μm, it has strength, workability, and solderability suitable for a header plate of a heat exchanger, and has SCC resistance not only against the external environment but also against the internal environment that comes into contact with the LLC. We can provide excellent and inexpensive copper alloys. In addition, there is the usual residual of deoxidizing agents such as P used in the melting process, and Fe and P that are unavoidably mixed in industrially.
Impurities such as b, Ag, and S do not impair the effects of the present invention.

〔Example〕

The present invention will be described below with reference to Examples.

An ingot with the chemical components shown in Table 1 was melted, and after being divided into two parts, 8
It was heated to 00°C and hot rolled into a board with a thickness of 8 mm. After removing the oxide film on the surface by pickling, cold rolling and annealing were repeated to obtain a plate material with a thickness of 0.8 mm.
A heat treatment was performed in the range of 5 to 60 seconds to prepare samples having the crystal grain sizes shown in Table 2. Table 2 shows the results of measuring the bow tensile strength and elongation as mechanical properties of the obtained samples.

Next, the sample prepared in this way was pressed into a header plate, and the press workability was investigated. Those with good press workability were marked with ○, those with slight unevenness were marked with Δ, and those with significant unevenness were marked. Those with rough skin are marked with an X, and those with cracks during molding are marked with an XX, and these are also listed in Table 2.

In addition, this header plate is used to form a radiator core, a plastic tank is attached to the header plate, and the radiator is created by caulking the area around it, making it SCC resistant.
The characteristics were compared and evaluated as follows. In other words, regarding SCC resistance, the external environment and internal environment are separated, and the SCC resistance of the external environment is
CC resistance was measured by measuring the time until leakage occurred in a 1% ammonia atmosphere, and SCC resistance in the internal environment was measured by filling LLC diluted to 30% at 80°C with an internal pressure of 2kg/'cd. After holding it for 90 days, it was evaluated based on the presence or absence of leakage and the presence or absence of cracks after disassembly. In other words, regarding liquid leakage, if there is no liquid leakage, mark ○, and if there is a decrease in the liquid sealing ability of the joint (
Liquid leakage due to material softening (softening of the material) is represented by an X mark, liquid leakage due to SCC is represented by an XX mark, and cracking after disassembly is represented by the presence or absence of SCC in the material, and these are also listed in Table 2.

As is clear from Table 2, the alloy of the present invention with a grain size of 20 to 80 μm has both sufficient strength and workability as a header plate, and is more resistant to internal and external environments than conventional alloys. It can be seen that the SCC resistance is significantly improved. On the other hand, it can be seen that most of the comparative alloys with different alloy components have poor SCC resistance in the internal environment even if the crystal grain size is within the range of 20 to 80 μm.

Also, although the alloy components are within the specified range, the crystal grain size is 10 μm.
Comparative alloy Nα15 with a grain size of 100 μm or less cracks during press forming (comparative alloy Nα15 with grain size of 100 μm)
In case of t18), significant roughness occurred during molding.

Although it has been explained that the alloy of the present invention has excellent properties as a header plate, it can be used not only for header plates but also other parts of heat exchangers such as tubes, as well as materials for electrical and electronic parts such as wiring materials, terminals, and connectors. However, it is possible to improve the lifespan at a low cost.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent SCC in an automobile heat exchanger and provide a high performance and highly reliable heat exchanger. Therefore, it is possible to use a heat exchanger with an integrally caulked structure in the radiator, and at the same time, since it has sufficient strength, it is possible to reduce the thickness of the plate, making it possible to reduce the weight and cost of the heat exchanger, which is an industrially significant feature. It is effective.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway perspective view of the structure of an automobile radiator. 1 tube, (2) fin. 3 core, (4) header plate. 5) Plastic tank. 6) Claw part of header plate. 7) Claw part of plastic tank. 8 Caulking plate 9) Elastic sealing material Figure 1

Claims (2)

[Claims] (1) Zn5-30wt%, Sn1-5wt% and Si
A copper alloy for a heat exchanger header plate, characterized in that the copper alloy contains 0.05 to 3.0 wt%, the balance consists of Cu and inevitable impurities, and has a crystal grain size of 20 to 80 μm. (2) Zn5-30wt%, Sn1-5wt% and Si
Contains 0.05-3.0wt%, and further includes P0.1wt%
Below, Ni3wt% or less, Al2wt% or less, Mn2w
t% or less, Zr1.5wt% or less, Mg3wt% or less, one or more types in total 0.05 to 5wt%
1. A copper alloy for a header plate of a heat exchanger, characterized in that the remainder is Cu and unavoidable impurities, and has a crystal grain size of 20 to 80 μm.