JPH04128333A - Te-and p-added brass excellent in corrosion - Google Patents

Abstract

PURPOSE:To remarkably improve the dezincification resistance of brass and also to improve the corrosion resistance of brass to a large extent by incorporating Te and P into a Cu-Zn alloy and further regulating the crystalline grain size of this alloy. CONSTITUTION:A copper alloy having satisfactory properties required of a heat exchanger material, free from deterioration in thermal conductivity and electric conductivity, causing no particular rise in material price, and excellent in corrosion resistance can be produced by providing a brass having a composition consisting of, by weight, 25-38% Zn, 0.005-0.5% Te, 0.005-0.05% P, and the balance Cu with inevitable impurities and also regulating the average crystalline grain diameter of this brass to 2-10mum.

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 become more and more deteriorating, the materials used in the devices have become increasingly salty. 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 were considering improving the dezincification corrosion resistance of brass by incorporating Te and P into a Cu-Zn alloy. The inventors have discovered that the corrosion resistance of brass can be significantly improved by adjusting the crystal grain size of this alloy, and have thus arrived at the present invention. It is something that

That is, in the present invention, Zn is 25 to 38% by weight and Te
0.005-0.5% and P 0.005-0.05
It is intended to disclose that the above-mentioned problems can be solved by using a material that is made of brass containing 1.5% of copper, with the remainder being Cu and unavoidable impurities, and whose average crystal grain size is adjusted to 2 to 10 μm. be.

[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.If the Zn content exceeds 38% by weight, This is because 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. This is because, on the contrary, the effect of improving the property of reducing the corrosion depth deteriorates, and Te precipitates at the grain boundaries, impairing the workability of the material.

Furthermore, P has the effect of changing the corrosion form of the material from plug-like to layer-like, resulting in a decrease in the corrosion depth of the material.

In this case, the reason why the P content is limited to 0.005 to 0.05% by weight is that a P content of less than 0.005% by weight is sufficient to change the corrosion form of the material from plug-like to layer-like. On the other hand, if the P content exceeds 0.05% by weight, P will segregate at the grain boundaries, and the grain boundaries will be preferentially corroded, causing the material to deteriorate. This is because it starts to have a negative impact on the

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 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 3473 g of electrolytic copper, 1520 g of electrolytic zinc, and Cu-5
1g of 0% Te master alloy and 5.9g of Cu-15%P master alloy
was used as the raw material, and the analysis values were 30.4% by weight of Zn and Te.
a, 01% by weight, and po.

A copper alloy consisting of 0.15% by weight and the balance Cu was melted in an atmospheric melting furnace to a thickness of 30 mm, width of 100 mm, and length of 150 m.
m ingots were obtained.

The surface of the obtained ingot was milled 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 milled by 1 mm on each side, and then Cold rolling was performed to a thickness of 3 mm, and 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 5 μm, cold working was performed to obtain a strip with a thickness of 0.3 mm, and from this strip, a width of 25 mm was obtained. A test piece with 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
The measurement was carried out in accordance with the comparison method of the crystal grain size test method for rolled copper products specified in 1997, and the salt spray test method specified in JIS Z2371 was adopted as the test method for examining 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 in the above manner was 36μ.
It was m.

Example 2 Electric #i 3219 g, electrolytic zinc 1770 g, 5
Using 2.5 g of 0% Te-Cut alloy and 8.24 g of 15% p-cU master alloy as raw materials, the analysis values were 35.4% by weight of Zn, 025% by weight of Tea, 021% by weight of Po, and the balance Cu. A copper alloy with an average crystal grain size of 4μ was obtained.
As a result of processing in the same manner as in Example 1 except that m was used, the measured maximum corrosion depth of the sample was 38 μm.

Example 3 3221 g of electrolytic copper, 1735 g of electrolytic zinc, and 50% T
38g of e-Cu master alloy and 5.9g of 15% P-CU master alloy
g is used as a raw material, and the analysis value is 34.7% by weight of Zn,
Tea, 38% by weight and 5PO, 021% by weight, balance Cu
As a result of processing in the same manner as in Example 1, except that the average crystal grain size was 5 μm, a copper alloy consisting of
The measured maximum corrosion depth of the sample was 36 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 The analysis values were 35.5% by weight of Zn and Tea.

A copper alloy consisting of 003% by weight, Po, 030% by weight, and the balance CU was obtained, and as a result of processing in the same manner as in Example 1, except that the average crystal grain size was 7 μm, the results were measured. The maximum corrosion depth of the sample was 51 μm.

Comparative Example 3 Analysis values: Zn 35.4% by weight and 20102% by weight
A copper alloy consisting of , and the remainder Cu was obtained, and treated in the same manner as in Example 1, except that the average grain size was 6 μm. As a result, the maximum corrosion depth of the measured sample was 56 μm.
Met.

Comparative example 4 The analysis values were Zn 34.7% by weight and T e 0.

A copper alloy consisting of 032% by weight, Po, 054% by weight, and the balance CU was obtained, and as a result of processing in the same manner as in Example 1, except that the average crystal grain size was 5 μm, the results were measured. The maximum corrosion depth of the sample was 54 μm.

Comparison Fs5 The analysis values were 35.1% by weight of Zn and Tea.

A copper alloy consisting of 0.3% by weight, Po, 0.22% by weight, and the balance Cu was obtained, and as a result of processing in the same manner as in Example 1, except that the average crystal grain size was 20 μm, the results were measured. The maximum corrosion depth of the sample was 45 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;
~0.5% and 0.005 to 0.05% of P, with the remainder consisting of Cu and inevitable impurities.
Brass with excellent corrosion resistance and P added. 2) The brass with excellent corrosion resistance to which Te and P are added according to claim 1, characterized in that the average crystal grain size is 2 to 10 μm.