JPH04128332A - Te-added brass excellent in corrosion resistance - 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] [Industrial Application Field] The present invention is used as a material for heat exchangers such as condensers, water heaters, distillers, coolers, water supply devices, etc., particularly for automobiles, etc. This invention relates to brass with excellent corrosion resistance, which is suitable as a tube material for radiators.

[Prior Art] Conventionally, brass or a copper alloy to which a small amount of P is added has been generally used as a tube material for a radiator, and it has particularly good mechanical properties and formability. Brass has been widely used because it exhibits excellent properties and can be obtained at a lower price than other copper alloys.

However, in recent years, as the areas in which the above devices are used have expanded and the environment in which they are used has deteriorated, the materials used in the devices have a high salt concentration. As heat exchangers are increasingly being used in the atmosphere on beaches and in the atmosphere near cities where exhaust gas concentration is high, deterioration of function due to material corrosion has become frequently observed in the main parts of heat exchangers. The emergence of materials with higher corrosion resistance than conventional materials has been awaited.

[Problems to be Solved by the Invention] Although ordinary brass is reasonably priced, it is extremely sensitive to stress corrosion cracking phenomenon that occurs when stress is applied in a corrosive atmosphere. As materials for heat exchangers are required to be lightweight, they are required to be thin, so it is becoming more and more desirable to supply materials that can easily withstand corrosive environments.

The present invention is a copper alloy that satisfies the performance required for materials for heat exchangers, and that has excellent corrosion resistance without reducing thermal conductivity or electrical conductivity, without significantly increasing the material price. The purpose is to provide the following.

[Means for Solving the Problems] The inventors of the present invention, while considering improving the dezincification corrosivity of brass, found that by incorporating Te into a Cu-Zn alloy, the dezincification corrosivity of brass was significantly improved. In addition to discovering that improvements can be observed, they also discovered that by adjusting the crystal grain size of this alloy, it is possible to significantly improve the corrosion resistance of brass, leading to the present invention. It is.

That is, in the present invention, Zn is 25 to 38% by weight and Te
Brass contains 0.005 to 0.5% of CU and the remainder is CU and unavoidable impurities, and its average crystal grain size is 2.
It is intended to disclose that the above-mentioned problems can be solved by using a material whose thickness is adjusted to ~10 μm.

[Function] In the present invention, Zn is dissolved in Cu to give it the function of improving material strength, and the reason why the Zn content is limited to 25 to 38% by weight is as follows. If the Zn content is less than 25% by weight, the material strength will not be sufficient and the copper content will increase, leading to an increase in price. In this case, the amount of β phase precipitated becomes large, and the workability of the material deteriorates.

Next, Te acts as a solid solution in the alloy base to shift the corrosion form of brass from partial dezincification corrosion to full-scale corrosion, and to reduce the corrosion loss. , the reason why the content of Te is limited to 0.005 to 0.5% by weight is that the content of Te is 0.005% by weight.
If the Te content is less than 0.5% by weight, no improvement in the effect of suppressing dezincification corrosion of the material will be observed, and furthermore, if the Te content exceeds 0.5% by weight, the amount of general corrosion of the material will increase. Therefore, if the corrosion depth is reduced, the effect of improving the properties of
This is because the workability of the material will be impaired.

Finally, adjusting the grain size of the material is necessary to suppress the corrosion progression force that develops in the depth direction of the material, but in this case, it is necessary to adjust the average grain size of the material. 2
It is adjusted to ~10 μm.

If the average crystal grain size is less than 2 μm, the processed structure tends to remain, and the corrosion resistance of the material deteriorates. If the average grain size exceeds 10 μm, it may cause general corrosion of the material. This is because the effect of reducing the maximum observed corrosion depth begins to be lost.

The average grain size of a material is normally measured after the final annealing process, but since the rolling rate of the radiator tube material is low in the finishing process, it is measured after the final cold rolling. Because no change is observed in the average grain size before and after the process, all values of the average grain size described in this specification are measured for the material that has undergone the final cold working. ing.

[Example] Example 1 Electrolytic copper 33524, electrolytic zinc 1475g, Cu-5
Using 1.1 g of 0% Te master alloy as raw material, the analysis value is Z
n29.5% by weight, Te0.01% by weight, balance Cu
A copper alloy consisting of
An ingot with a radius of 100 mm and a length of 150 mm was obtained.

The surface of the obtained ingot was chamfered by 2 mm on each side, and then hot-rolled at a temperature of 850°C to form an intermediate material with a thickness of 10 mm.Furthermore, the surface of this intermediate material was chamfered by 1 mm on each side. After cold rolling to a thickness of +3 mm, intermediate annealing was performed again at a temperature of 600''C for 1 hour in a nitrogen atmosphere.

The material subjected to intermediate annealing was subsequently cold rolled into a strip with a thickness of 0.4 mm, and then rolled at a temperature of 450°C.
After final annealing for 1 hour in a nitrogen atmosphere to adjust the average grain size of the strip to 6 μm, it was further cold-worked into a strip with a thickness of 0.3 mm. A test piece with a width of 25 mm and a length of 100 mm was cut out and subjected to grain size and corrosion resistance tests.

When measuring the grain size of materials, JISH0501
In addition to measuring according to the comparison method of the crystal grain size test method for rolled copper products specified in 2013, the salt spray test method specified in JIS Z2371 is used as the test method to check the corrosion resistance of the material.

In this case, the treatment time of salt water spray on the test piece is 1 continuous time.
After the salt spray treatment was completed for 50 hours, the test piece was cut into 6 equal parts in the width direction, and the corrosion depth was measured using an optical microscope on each cut surface of the test piece. Measurements were taken over the entire length of the 25 mm sample at 5 locations, totaling 125 mm, and the depth of the most deeply corroded part between these points was defined as the maximum corrosion depth of the sample.

The maximum corrosion depth of the sample measured as above was 39μ.
It was m.

Example 2 3227 g of electrolytic copper, 1765 g of electrolytic zinc, and 50% T
Using 8g of e-Cu master alloy as raw material, the analysis value is Zn3
A copper alloy consisting of 5-3% by weight, Tea, 08% by weight, and the balance Cu was obtained and treated in the same manner as in Example 1 except that the average crystal grain size was 8 μm. As a result, the results were measured. The maximum corrosion depth of the sample was 32 μm.

Example 3 3227 g of electrolytic copper, 1740 g of electrolytic zinc, and 50% T
Using 33g of e-Cu master alloy as a raw material, the analysis values were 34.8% by weight of Zn, 33% by weight of Tea, and the balance C.
A copper alloy consisting of u was obtained, and the sample was treated in the same manner as in Example 1, except that the average crystal grain size was 4 μm. As a result, the maximum corrosion depth of the measured sample was 35 μm.

Comparative Example 1 Zn content 30.3 with average crystal grain size adjusted to 5 μm
As a result of processing in the same manner as in Example 1 except that the sample was made of brass having a weight of %, the measured maximum corrosion depth of the sample was 82 μm.

Comparative Example 2 A copper alloy consisting of 35.5% by weight of Zn, 3% by weight of Te, and the balance Cu was obtained as an analysis value, and treated in the same manner as in Example 1 except that the average crystal grain size was 7 μm. As a result, the maximum corrosion depth of the sample measured was 75
It was μm.

Comparative example 3 The analysis values were 35.4% by weight of Zn and Tea.

A copper alloy consisting of 10% by weight, Po, 02% by weight, and the balance Cu was obtained, and the result was measured in the same manner as in Example 1, except that the average crystal grain size was 6 μm. The maximum corrosion depth of the sample was 56 μm.

Comparative example 4 The analysis values were 35.3% by weight of Zn and Tea.

A copper alloy consisting of 0.8% by weight and the balance Cu was obtained, and the treatment was carried out in the same manner as in Example 1, except that the average grain size was 20 μm. As a result, the maximum corrosion depth of the measured sample was was 42 μm.

As described above, by carrying out the present invention, it has become possible to easily obtain a material that exhibits a high degree of corrosion resistance even in a corrosive environment.

The above measurement results are shown in Table 1.

Further, Table 2 summarizes the results of measuring the maximum corrosion depth of materials for alloys of the same composition with different average grain sizes.

(Margins below this page) [Effects of the invention] By carrying out the present invention, radiators used in automobiles, etc. can be used as materials for heat exchangers such as condensers, water heaters, distillers, coolers, water supply devices, etc. It has made it possible to easily obtain brass, which has excellent corrosion resistance and is suitable as a tube material, making a great contribution to this industry.

Claims (1)

[Claims] 1) 25 to 38% Zn and 0.005% Te by weight;
Te-added brass with excellent corrosion resistance characterized by containing ~0.5% of Te with the remainder consisting of Cu and unavoidable impurities. 2) The Te-added brass with excellent corrosion resistance according to claim 1, characterized in that the average crystal grain size is 2 to 10 μm.