JPH04120230A - Brass mixed with in and sb and excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of brass without deteriorating its heat conductivity and heat conductivity by incorporating specified amounts of In and Sb into brass. CONSTITUTION:The compsn, of brass is constituted of, by weight, 25 to 38% Zn, 0.05 to 0.5% In, 0.01 to 0.3% Sb and the balance Cu with inevitable impurities. Its average grain size is preferably regulated to 2 to 10mum. In enters into solid soln. in the matrix of the alloy and has effects of transforming the corrosive form of the brass from a partial dezincing one into a general corrosive one and reducing its corrosive loss. Sb transforms the corrosive form of the brass from a partial dezincing one into a general corrosive one and reduces its corrosive loss by changing the form of the dezincing corrosion from a linear one into an exfoliation one. Moreover, by the regulation of the grain size, the force of corrosion progressing in the depth direction of the material can be suppressed.

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 of beaches and urban areas with high concentrations of exhaust gas, deterioration of function due to corrosion of the materials in the main parts of heat exchangers has become frequently observed.

For this reason, 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 uses copper, which has excellent corrosion resistance, without reducing thermal conductivity or electrical conductivity, and without making the material price too high, as a material that satisfies the performance required for materials for heat exchangers. The purpose is to provide alloys.

[Means for Solving the Problem] The inventors of the present invention were considering improving the dezincification corrosion resistance of brass by incorporating In and Sb into a Cu-Zn alloy. They discovered that the corrosion resistance of brass was significantly improved, and further discovered that by adjusting the grain size of this alloy, it was possible to significantly improve the corrosion resistance of brass. This is what led to this.

That is, in order to solve the problem, the present invention contains 25 to 38% of Zn, 0.05 to 0.5% of In, 0.01 to 0.3% of Sb, and the balance is In addition to disclosing brass made of Cu and unavoidable impurities, it is also intended to disclose that the above-mentioned problems can be solved by using the above-mentioned brass material whose average crystal grain size is adjusted to 2 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. Also, if the Zn content exceeds 38% by weight, In this case, the amount of β phase precipitated becomes large, and the workability of the material deteriorates.

Next, In is solid dissolved in the alloy base, and has the effect of shifting the corrosion mode of brass from partial dezincification corrosion to full-scale corrosion mode, as well as reducing the corrosion loss. , the content of In is 0.05 to 0.5% by weight
The reason for this limitation is that when the In content is less than 0.05% by weight, no improvement in the effect of suppressing dezincification corrosion of the material is observed, and furthermore, when the In content exceeds 0.5% by weight, When this happens, the amount of corrosion on the entire surface of the material increases.
On the contrary, the effect of improving the characteristic of reducing the corrosion depth deteriorates.

Next, Sb changes the form of dezincification corrosion from plug-like to layered, thereby shifting the corrosion form of brass from partial dezincification corrosion to full-scale corrosion and reducing the corrosion loss. However, the reason why the Sb content is limited to 0.01 to 0.3% by weight is that if the Sb content is less than 0.01% by weight, the material will undergo dezincification corrosion. No effect was observed on changing the
If the Sb content exceeds 0.3% by weight, Sb will segregate at the grain boundaries, and as a result, the grain boundary areas will be preferentially corroded. It is.

Finally, adjusting the grain size of the material is necessary to suppress the corrosion force that progresses toward the depth of the material, but in this case, it is necessary to adjust the average grain size of the material by 2. ~1
The reason why it is adjusted to 0 μm is that if the average crystal grain size is less than 2 μm, processed structures tend to remain, and the corrosion resistance of the material deteriorates.If the average grain size exceeds 10 μm, This is because the decrease in the maximum corrosion depth that would occur if the general corrosion phenomenon of the material was suppressed was no longer observed.

Note that the average grain size of a material is normally measured in the final annealed state, but the radiator tube material that is the subject of the present invention has a low finish rolling rate, so it is measured after the final cold rolling. No change was observed in the average grain size of the material between before and after, and all values of average grain size described in this specification were measured for the material that had completed the final cold rolling process. It is something that

[Example] Example 1 Electric tR 3564g, electrolytic zinc 1425g, In
Using 9g of Zn and 2.5g of Sb as raw materials, the analysis value shows Zn
28-5% by weight, In0.18% by weight, and Sb0.0
A copper alloy consisting of 5 weights, 1%, and the balance Cu is melted in an atmospheric melting furnace, and has a thickness of 30 mm, a width of 100 mm, and a length of 150 mm.
Obtained an ingot.

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 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
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 W4fR mirror on each cut surface of the test piece, and the test piece was subjected to the test. Measurements were taken over the entire length of a sample with a width of 25 mm at five locations, totaling 125 mm, and the depth of the most deeply corroded part between these points was taken as the maximum corrosion depth of the sample.

The maximum corrosion depth of the sample measured as above was 4 μm.
Met.

Example 2 3468 g of electrolytic copper, 1520 g of electrolytic zinc, and In11
Using Zn30.g and Sb1g as raw materials, the analysis value was Zn30.
4% by weight, 0.22% by weight of In, and 0.02% by weight of Sb.
% 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 8 μm. there were.

Example 3 3193g of electrolytic copper, 1785g of electrolytic zinc, and In16
．． 5g and 5.5g of Sb were used as raw materials, and the analysis value was Z
n35.7% by weight, In0.33% by weight, and Sb0.
A copper alloy consisting of 11% by weight and the balance Cu was obtained and treated in the same manner as in Example 1 except that the average grain size was 5 μm. was 12 μm.

Comparative Example 1 Zn content 30.5 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 75 μm.

Comparative example 2 The analysis value was 35.3% by weight of Zn and Ino.

A copper alloy consisting of 23% by weight and the balance 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 measured maximum corrosion depth of the sample was was 18 μm.

Comparative Example 3 Analysis IN To L Te Z n 34 , 31E Amount % To, Sbo.

A copper alloy consisting of 0.8% by weight and the balance Cu was obtained, and the average crystal grain size was 8 μm, but the treatment was carried out in the same manner as in Example 1. As a result, the measured maximum corrosion depth of the sample was was 31 μm.

Comparative example 4 The analysis value was 36.4% by weight of Zn, and Ino.

A copper alloy consisting of 0.2% by weight, Po, 0.20% 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 7 μm. The maximum corrosion depth of the sample was 33 μm.

Comparative example 5 The analysis value was 34.4% by weight of Zn and Ino.

A copper alloy consisting of 62% by weight, 3% by weight of SbO, 209015% by weight, and the balance Cu was obtained, and the process was carried out in the same manner as in Example 1, except that the average crystal grain size was 5 μm. As a result, the maximum corrosion depth of the sample measured was 23
It was μm.

Comparative example 6 The analysis value was 29.6% by weight of Zn, and Ino.

22% by weight, 0.33% by weight of Sb, and po.

A copper alloy consisting of 23% by weight and the balance Cu was obtained and treated in the same manner as in Example 1, except that the average grain size was 8 μm. As a result, the measured maximum corrosion depth of the sample was 21 μm.

Comparative example 7 The analysis value was 35.2% by weight of Zn and Ino.

A copper alloy consisting of 21% by weight of Sb, 0.04% by weight of Sb, 101023% by weight of Cu, and the balance was treated in the same manner as in Example 1, except that the average crystal grain size was 20 μm. As a result, the maximum corrosion depth of the sample measured was 3
It was 8 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.

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 for tubes, making a great contribution to this industry.

Claims (1)

[Claims] 1) 25 to 38% Zn and 0.05 to 38% In by weight;
0.5%, contains 0.01-0.3% Sb, and the balance is C.
In and S characterized by consisting of u and inevitable impurities
Brass with excellent corrosion resistance added with b. 2) The brass with excellent corrosion resistance to which In and Sb are added according to claim 1, characterized in that the average crystal grain size is 2 to 10 μm.