JPH07166275A - Copper alloy excellent in resistance to ant-lair-like corrosion and heat exchanger tube made of this copper alloy - Google Patents

Abstract

PURPOSE:To obtain the copper alloy and the heat exchanger tube by incorporating specific amounts of R (rare earth elements excluding Y), Sn, Al, and P into Cu. CONSTITUTION:This copper alloy has a composition consisting of, by weight, 0.005-2% R, 0.005-5% Sn,. 0.005-5% Al, 0.005-0.5% P, and the balance Cu. This copper alloy has resistance to ant-lair-like corrosion improved to a greater extent, and a copper alloy tube composed of this copper alloy has superior resistance to ant-lair-like corrosion, and, when this tube is used as heat exchanger tube, the occurrence of leakage accident caused by ant-lair-like corrosion can be prevented. The above corrosion inhibiting effect becomes insufficient when the content of R is below the lower limit, and, when it exceeds the upper limit, deterioration in workability is brought about because ductility, etc., are deteriorated. The effect of inhibiting the occurrence and development of the above corrosion becomes insufficient when the contents of Sn and Al are below the lower limits, and, when they exceed the upper limits, workability is deteriorated. As to P content deoxidation and the above corrosion inhibiting effect become insufficient when it is below the lower limit, and, when it exceeds the upper limit, workability is deteriorated and the effect of improving corrosion resistance to a greater extent cannot be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy excellent in ant nest corrosion resistance, and further, a copper alloy for a heat exchanger comprising the ant nest corrosion corrosion resistance. It is about piping.

[0002]

2. Description of the Related Art Conventionally, phosphorous deoxidized copper pipes have been widely used as copper alloy pipes for heat exchangers (for example, JP-A-63-63).
No. 247326). This is because phosphorus deoxidized copper is heat conductive,
This is because the corrosion resistance is excellent, and the piping made of this phosphorous deoxidized copper is also excellent in workability and workability in addition to heat conductivity and corrosion resistance.

[0003]

However, the phosphorous deoxidized copper pipe used in the heat exchanger has a problem in that a leakage accident due to ant nest corrosion may occur. The features of ant nest corrosion are that they occur even though no abnormalities in chemical composition and tissue are observed, that the corrosion holes are so small that they are hard to detect with the naked eye, and that the corrosion section is specific and erosion occurs. It is shaped like an ant's nest that is intricately and intricately linked in a tunnel.

The reason why ant nest corrosion occurs when a phosphorus-deoxidized copper pipe is used as a heat exchanger pipe is that the lubricating oil remaining on the inner surface of the phosphorus-deoxidized copper pipe deteriorates and changes to an organic acid. It is considered to be generated by the contact of this organic acid, but it is not clear. In any case, it is a copper alloy excellent in ant nest corrosion resistance and a heat exchanger copper excellent in ant nest corrosion resistance. Alloy piping was required.

[0005]

Therefore, the present inventors have
From the above viewpoints, as a result of research to develop a copper alloy pipe for a heat exchanger, which is more excellent in ant nest corrosion resistance than the conventional phosphorus-deoxidized copper pipe, , R (where R is a rare earth element other than Y): 0.005 to 2% by weight, Sn: 0.05 to 5% by weight, and Al: 0.005
If it is contained in an amount of up to 5% by weight, the corrosion resistance of the copper alloy in the form of ant nest corrosion is further improved, and the copper alloy pipe made of this copper alloy is excellent in the ant nest formation corrosion resistance and can be used as a heat exchanger pipe. We also obtained the knowledge that no leakage accident due to ant nest corrosion will occur.

The present invention has been made on the basis of such findings. (1) R: 0.005 to 2% by weight, Sn: 0.05 to 5% by weight, Al: 0.005 to 5%
% Copper, P: 0.005 to 0.5% by weight, the balance being Cu and unavoidable impurities, and a copper alloy excellent in ant nest corrosion resistance, and (2) R: 0. ．
005 to 2% by weight, Sn: 0.05 to 5% by weight, Al:
0.005-5% by weight, P: 0.005-0.5% by weight
And a balance of Cu and unavoidable impurities, and a heat exchanger pipe made of a copper alloy having excellent ant-nest corrosion resistance.

Next, the reason why the component composition of the copper alloy of the present invention which is excellent in ant-nested corrosion resistance and the copper alloy piping is limited as described above will be explained.

(A) RR has the effect of suppressing ant nest corrosion when added to phosphorous deoxidized copper, but its content is 0.005% by weight.
If it is less than, the effect of suppressing the ant nest corrosion of the copper alloy is not sufficient,
On the other hand, if the content is more than 2% by weight, the effect of improving the ant's nest-like corrosion resistance is saturated, and rather the workability is deteriorated due to the decrease in ductility and the like, which is not preferable for pipe forming. Therefore, the content of R is set to 0.005 to 2% by weight.

(B) Sn Sn has a function of forming a stable oxide to suppress the occurrence of ant nest-like corrosion and its growth, but its content is 0.
If it is less than 05% by weight, the effect of stabilizing the surface of the copper alloy by the oxide film is not sufficient, so a satisfactory effect of suppressing ant nest-like corrosion cannot be obtained. Therefore, it is not preferable for tube forming. Therefore, the Sn content is set to 0.05 to 5% by weight.

(C) Al Al also forms a stable oxide to suppress the occurrence of ant nest corrosion and its growth, but its content is 0.0
If it is less than 05% by weight, a sufficient effect of suppressing ant nest corrosion cannot be obtained. On the other hand, if more than 5% by weight is contained, the weldability, brazing property and workability are rather deteriorated. Therefore, the content of Al is set to 0.005 to 5% by weight.

(D) P P is added to the copper alloy as a deoxidizing agent to facilitate the production of a sound ingot and to contain it to suppress the occurrence of ant nest corrosion and its growth. When the content is less than 0.005% by weight, there is no sufficient deoxidizing effect, and a sufficient effect of suppressing ant nest corrosion is not obtained, while 0.
If the content is more than 5% by weight, a phosphide is formed, the workability is remarkably deteriorated, the pipe forming becomes difficult, and the effect of further improving the ant-nest-corrosion resistance cannot be obtained. Therefore, the content of P is set to 0.005 to 0.5% by weight.

In addition, the ant-nest-corrosion-resistant copper alloy of the present invention contains Pb, As, Fe, Se, and
Even if each of S and Sb is contained in a few ppm or less and oxygen is contained in an amount of about 50 ppm, it does not have any influence on the nest-like corrosion resistance of the ant.

[0013]

EXAMPLES Next, the ant-nest-corrosion-resistant copper alloy of the present invention and a pipe made of the copper alloy will be described in detail with reference to examples.

Outer diameter: 15.88 mm, wall thickness: 1.00 m
m, length: 250 mm, JIS standard H330
0, C1220T-OL material of conventional phosphorous deoxidized copper pipe (hereinafter referred to as conventional copper alloy pipe), made of a copper alloy having the component composition shown in Tables 1 to 3, outer diameter: 15.88 mm,
The copper alloy pipes for the heat exchanger of the present invention (hereinafter referred to as the copper alloy pipes of the present invention) 1 to 17 and the copper alloy pipes for the comparative heat exchanger (hereinafter, comparative copper alloy) having dimensions of wall thickness: 1.00 mm and length: 50 mm. 1 to 8 were prepared.

In each of the comparative copper alloy pipes 1 to 8, any one of the constituent components was out of the scope of the present invention (compositions out of the scope of the present invention are marked with *. Table 3 is shown).

The above copper alloy pipes 1 to 17 of the present invention and the comparative copper alloy pipes 1 to 8 were respectively connected to the conventional copper alloy pipe by a heat shrink tube made of Teflon to prepare a test copper alloy pipe having a total length of 300 mm. One end of this test copper alloy tube was sealed with a silicon stopper, 2 ml of a corrosive liquid consisting of 1 vol% formic acid was injected into the test copper alloy tube, the other end was sealed with a silicon stopper, and then the test copper alloy tube was sealed. Shake well and let the corrosive liquid adhere to the entire surface of the pipe. As described above, the reason why the copper alloy pipes 1 to 17 of the present invention and the comparative copper alloy pipes 1 to 8 are respectively connected to the conventional copper alloy pipes by the heat-shrinkable tube made of Teflon to make the test copper alloy pipes having a total length of 300 mm are to be obtained. The difficult copper alloy pipes 1 to 17 of the present invention and the comparative copper alloy pipes 1 to 8 are saved, and a certain length is secured as in the case where the pipes are used as pipes, so that the vapor pressure inside the pipes is made uniform. This is to secure and approximate the pipe conditions.

Next, a test copper alloy tube in which 2 ml of a corrosive liquid was injected was fixed in a constant temperature water tank in a state of standing in the longitudinal direction and half immersed in water. Corrosion test in which the copper alloy pipe is heated and cooled by simulating the temperature cycle that the copper alloy pipe undergoes day and night for 3 months under the condition of keeping for 12 hours. I went.

After completion of the corrosion test, the test copper alloy tube was taken out from the constant temperature water bath, the test copper alloy tube was cut into two pieces in the longitudinal direction, the cut surface was polished, and an optical microscope observation was performed to carry out the copper alloy pipe 1 of the present invention. .About.17, comparative copper alloy pipes 1 to 8 and conventional copper alloy pipes, the maximum erosion depth due to ant nest corrosion was measured, and the measurement results are shown in Tables 1 to 3.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

From the results shown in Tables 1 to 3, R: 0.
005 to 2% by weight, Sn: 0.05 to 5% by weight, Al:
0.005-5% by weight, P: 0.005-0.5% by weight
It can be seen that each of the copper alloy pipes 1 to 17 of the present invention containing the above is superior to the conventional copper alloy pipe in corrosion resistance of the ant nest. However, the comparative copper alloy pipe 1 out of the above range 1
Nos. 8 to 8 are not preferable as copper alloy pipes for heat exchangers because they are inferior in ant nest corrosion resistance, or have excellent ant nest corrosion resistance but extremely poor workability or brazeability. I also understand that.

[0023]

As described above, the pipe made of the copper alloy of the present invention is excellent in ant nest corrosion, and when used as a pipe for a heat exchanger, the reliability against ant nest corrosion has hitherto been high. It is further improved and has an excellent effect.

Front Page Continuation (72) Inventor Masato Watanabe 1975, Shimoishi Togami, Kitamoto City, Saitama 2 Mitsubishi Material Co., Ltd. Kitamoto Works

Claims (2)

[Claims] 1. R (where R is a rare earth element except Y): 0.005 to 2% by weight, Sn: 0.05 to 5% by weight, Al: 0.005 to 5% by weight, P: 0. 005
A copper alloy having excellent ant-nested corrosion resistance, characterized in that it has a composition containing 0.5% by weight and the balance being Cu and inevitable impurities. 2. R: 0.005 to 2% by weight, Sn: 0.
05-5% by weight, Al: 0.005-5% by weight, P:
A pipe for a heat exchanger, which is made of a copper alloy containing 0.005 to 0.5% by weight and the balance of Cu and unavoidable impurities and having excellent ant-nested corrosion resistance.