WO2018123731A1 - Ant nest corrosion resistant copper pipe and method for improving corrosion resistance using same - Google Patents

Abstract

Provided is copper pipe with excellent anticorrosive properties that is capable of exhibiting higher anticorrosive properties for ant nest corrosion and can suitably be used for heat transfer pipes, refrigerant pipes and the like in air conditioners and refrigeration equipment. The ant nest corrosion resistant copper pipe is formed using Cu material that includes P (phosphorus) in a proportion of 0.15 – 0.50% by mass and includes at least any one of the elements of Zn (zinc), Sn (tin), and Ni (nickel) in a total of 0.1 – 5.0% by mass, with the remainder being Cu and inevitable impurities.

Description

Ant-resistant nest-like corrosive copper pipe and method for improving corrosion resistance using the same

The present invention relates to the improvement of ant-corrosion resistant copper tube, and in particular, a technology for improving the corrosion resistance to ant-like corrosion of a copper tube suitably used for a heat transfer pipe, a refrigerant pipe and the like in air conditioners and refrigeration equipment. It is about

Conventionally, phosphorus (P) exhibits excellent characteristics in corrosion resistance, brazing property, thermal conductivity, bending workability, etc. in pipe materials such as heat transfer pipes of air conditioners and refrigerant piping (in-machine piping) of refrigeration equipment. Deoxidized copper (JIS-H3300-C1220T) has been mainly used.

By the way, phosphorus-deoxidized copper pipes, which are pipes used for such air conditioners and refrigeration equipment, are abnormal corrosion that progresses in the form of ant nest from the surface of the pipe in the thickness direction of the pipe, so-called ant nest It is recognized that corrosion may occur. This ant's nest corrosion is considered to occur in a wet environment using a lower carboxylic acid such as formic acid or acetic acid as a corrosive medium, and a chlorinated organic solvent such as 1,1,1-trichloroethane or a certain lubricating oil The same occurrence of corrosion has been confirmed even in the presence of formaldehyde and the like. In particular, it is known that when the pipe is used as a conduit in which dew condensation is caused in an air conditioner or a refrigerator, the occurrence is remarkable. And, if such ant nest corrosion occurs, it causes a problem that the rate of progress of the corrosion is high, and it progresses until it penetrates the copper pipe in a short period of time, and the equipment becomes unusable. It becomes.

For this reason, in Patent Document 1 (WO2014 / 148127), P (phosphorus) is contained at a ratio of 0.05 to 1.0% by weight, and the balance is made of Cu (copper) and Cu material which is an unavoidable impurity. It has been shown that a highly corrosion resistant copper tube is proposed, characterized in that it can improve the corrosion resistance to ant-like corrosion. That is, there is practically advantageously obtained a copper tube which can further improve the corrosion resistance to ant-like corrosion in a region where the P content is larger than a conventional tube made of phosphorus-deoxidized copper. The fact that it can be done is pointed out.

However, even in a copper tube formed by increasing the content of P, ant-like corrosion may occur in a more severe corrosive environment, and therefore, the corrosion resistance to ant-like corrosion is caused. Development of copper pipes of higher quality has been desired.

WO2014 / 148127

The present invention has been made on the background of such circumstances, and the problem to be solved is an air conditioner which can exhibit even higher corrosion resistance against nest-like corrosion of ant. And providing a copper pipe having excellent corrosion resistance that can be suitably used as a heat transfer pipe, a refrigerant pipe, etc. in refrigeration equipment, and a method of improving the corrosion resistance using the same, and using such a copper pipe. It also advantageously improves the life of the equipment being

Therefore, as a result of intensive studies on ant nest-like corrosion in a copper pipe as a pipe material used in an air conditioner, a refrigeration machine, etc., the present inventors determined P at a ratio of 0.15 to 0.50 mass%. By further containing at least one element of at least one of Zn, Sn and Ni in a total amount of 0.1 to 5.0% by mass with respect to the copper tube of the contained Cu material, The present invention has been accomplished by finding out the fact that the corrosion resistance against nest-like corrosion can be further improved.

That is, in the present invention completed based on such findings, P (phosphorus) is contained at a ratio of 0.15 to 0.50 mass%, and Zn (zinc), Sn (tin) and Termite-resistant characterized in that it contains 0.1 to 5.0% by mass in total of at least one element of Ni (nickel), and the balance is Cu and Cu which is an unavoidable impurity. The copper tube excellent in the nest-like corrosion property is the summary.

In addition, in the copper tube excellent in the nest corrosion resistance according to the present invention, more preferably, P is contained in a proportion of 0.15 to 0.50 mass%, and Zn, Sn or Ni is contained. The copper pipe is made of Cu material adjusted to have a content of 0.1 to 4.0% by mass to form a copper pipe, whereby a copper pipe having excellent corrosion resistance against ant-like nest corrosion is obtained. It can be advantageously formed.

In addition, according to one of the preferable embodiments of the formicary corrosive copper tube according to the present invention, the content of the unavoidable impurities is 0.05 mass% or less.

Furthermore, according to another preferred embodiment of the ant-resistant corrosive copper tube according to the present invention, the corrosive medium comprising a lower carboxylic acid, disposed in a wet environment, provides a tube wall thickness direction from the tube surface An ant-resistant corrosive copper tube is provided, characterized in that it is a copper tube that is exposed to the corrosive effect which proceeds in an ant-like manner.

And, in the present invention, the heat transfer pipe and refrigerant piping (in-machine piping) in air conditioners and refrigeration equipment comprising the above-mentioned nest-like corrosive copper pipe as described above are also the gist of the invention. .

In addition, according to the present invention, in a copper tube which is used in an air conditioner or a refrigerator and disposed in a wet environment, the lower carboxylic acid generated from the surface is generated in the wet environment as a corrosive medium The copper tube contains P in a proportion of 0.15 to 0.50% by mass and at least one of Zn, Sn, and Ni as a method for improving the corrosion resistance against nest corrosion of ant It is characterized by using a dovetail corrosive-resistant copper tube which contains two elements in a total amount of 0.1 to 5.0% by mass and the balance is Cu and Cu material which is an unavoidable impurity. The method of improving corrosion resistance is also the gist of the invention.

According to the present invention, a practical copper pipe which can exhibit further excellent corrosion resistance than conventionally known copper pipes in corrosion resistance to ants' nest-like corrosion can be advantageously provided. In addition, by using such a highly corrosion-resistant copper tube as a heat transfer pipe, refrigerant piping (in-machine piping), and the like in air conditioners and refrigeration equipment, the life of those equipments can be further effectively enhanced. It will be.

It is a partially expanded explanatory view of the cross section of an internally grooved tube manufactured in an example. It is partial explanatory drawing which shows the longitudinal cross-section containing the pipe axis of an internally grooved pipe in FIG. It is cross-sectional explanatory drawing which shows the outline | summary of the corrosion resistance test apparatus used in the Example.

By the way, in the dovetail-corrosion-resistant copper tube according to the present invention, the P content in the Cu material constituting it is in the range of 0.15 to 0.50 mass%, and Zn, Sn, Ni A major feature is that at least one of the elements is contained so as to have a ratio of 0.1 to 5.0% by mass in the total content. And by the inclusion of such a high concentration of P and the inclusion of a specific element, even in a more severe corrosive environment, generation of a selective corrosion form in which corrosion proceeds in the wall thickness direction in the form of ant nest, Corrosion resistance that is effectively suppressed or prevented and that is even better than known corrosion resistant copper tubes can be advantageously exhibited over a long period of time.

In the copper tube according to the present invention, when the P content is less than 0.15% by mass, a selective corrosion form is caused. The content needs to be 0.15 mass% or more. On the other hand, even if P content increases and exceeds 0.50% by mass, there is almost no change in the corrosion resistance against ant nest corrosion, but rather, the processability decreases in the production of a copper tube. The upper limit of the P content needs to be limited to 0.50% by mass, since problems such as cracking easily occur.

In addition, in the copper tube according to the present invention, when the content of Zn combined with the high P content as described above is less than 0.1% by mass, selective corrosion forms occur in a more severe corrosive environment. In the present invention, the Zn content needs to be 0.1% by mass or more. On the other hand, when the Zn content increases and exceeds 5.0% by mass, there is almost no change in the corrosion resistance against ants' nest corrosion, and the brazing temperature is lowered because the melting point of the copper material is lowered by the addition of Zn. From the viewpoint of difficulty, the upper limit of the Zn content is 5.0% by mass, preferably 4.0% by mass.

Similarly, if the content of Sn combined with such a high content of P is less than 0.1% by mass, a selective corrosion form will be triggered under a more severe corrosive environment, In the present invention, the Sn content needs to be 0.1% by mass or more. On the other hand, when the Sn content increases and exceeds 5.0% by mass, there is almost no change in the corrosion resistance against ant-like nest corrosion, but rather, the hot workability decreases in the production of a copper tube. The upper limit of the Sn content is 5.0% by mass, preferably 4.0% by mass, since problems such as cracking of the material are likely to occur.

Furthermore, in the copper tube according to the present invention, if the content of Ni combined with the high content of P is less than 0.1% by mass, selective corrosion morphology will be triggered under more severe corrosive environment However, in the present invention, the Ni content needs to be 0.1% by mass or more. On the other hand, when the Ni content increases and exceeds 5.0% by mass, there is almost no change in the corrosion resistance to the ant-like corrosion, but rather, plastic working in cold working etc. in the production of copper tubes. As the upper limit of the Ni content is 5.0% by mass, preferably 4.0% by mass is adopted, since it is likely that problems such as cracking and grooving can not be caused in roll forming due to a decrease in Be done.

And, in the present invention, it is possible to add and contain Zn, Sn and Ni alone as described above, in addition to or in combination of two or three of them. Are adjusted so that the total content of the combined elements is in the range of 0.1 to 5.0% by mass, desirably in the range of 0.1 to 4.0% by mass. The Rukoto.

In addition to the P content as described above and the contents of Zn and / or Sn and / or Ni, the remainder is composed of Cu (copper) and unavoidable impurities in addition to the P content and the content of Zn and / or Sn and / or Ni according to the present invention. Inevitable impurities such as Fe, Pb, Si, S, Bi, etc. are generally composed of 0.05 mass% or less, preferably 0.005 mass% or less, in total. It is adjusted to be as follows.

Thus, in the copper tube according to the present invention, the total content of added Zn and / or Sn and / or Ni in addition to the specified amount of P content is kept within the specified range. By doing this, it is possible to advantageously contribute to the improvement of the ant-like nest corrosion resistance, and the reason is considered to date as follows. That is, it is presumed that the formation of cuprous oxide plays an important role in the occurrence of ants' nest-like corrosion, and in the present invention, in the present invention, Zn, Sn and Ni as alloy components are considered. By adding a predetermined amount of at least one of the elements, it is possible to suppress the formation of such cuprous oxide and to effectively suppress the occurrence and progress of the ant-like corrosion It is believed that.

For this reason, the copper tube according to the present invention is disposed in a wet environment utilizing such characteristics, and proceeds from the surface of the tube in the thickness direction of the tube in an ant-like manner by a corrosive medium consisting of lower carboxylic acid. It is advantageously used as a tube exposed to the corrosive effect.

Moreover, the copper pipe according to the present invention as described above can be suitably used as a heat transfer pipe, refrigerant pipe, etc. in an air conditioner, and similarly, it can be used as a heat transfer pipe, refrigerant pipe (in-machine pipe), etc. in refrigeration equipment. It can be suitably used.

By the way, when manufacturing a copper tube according to the present invention having such a configuration, the balance is Cu and unavoidable impurities in the above-mentioned P content (concentration) and Zn, Sn and / or Ni content (concentration). Using the ingots and billets made of Cu material, the method of obtaining the target copper tube through the same process as the conventional one such as casting, homogenization treatment, hot extrusion of the tube, and drawing of the tube. However, at that time, it is also possible to combine preheating in the hot extrusion process which is plastic working with the homogenization treatment.

In the copper tube according to the present invention obtained as described above, the size such as the outer diameter and the wall thickness (tube wall thickness) is appropriately selected according to the application of the copper tube. For example, in the case where the copper tube according to the present invention is used as a heat transfer tube, it is well known that flat inner and outer surfaces which are surface shapes formed by tube extrusion are adopted, It is also effective to form a heat transfer tube which is provided with various forms of inner and outer grooves by being subjected to various kinds of inner and outer surface processing known in the art.

In the following, some examples according to the present invention will be shown to clarify the present invention more specifically, but the present invention is not limited by any description of such examples. It goes without saying. In addition to the embodiments described below, the present invention also includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention other than the specific description described above. It should be understood that it is possible to add improvements, etc.

First, using high-purity electric copper having a Cu content of 99.999% by mass or more, P is added at a ratio shown in Table 1 below, and further, Zn, Sn and Ni as additional elements are added. In order to investigate the effect of the inclusion of at least one of the elements listed above, at least one of the additional elements is contained in the proportions shown in Table 1 below, and the test copper tube No. 1 is contained. Various billets corresponding to 1 to 29 were cast.

Next, using these various billets, after their homogenization treatment, hot extrusion was performed according to a conventional method to obtain various extruded raw tubes having an outer diameter of 102 mm and an inner diameter of 75 mm. Further, the obtained extruded tube was cold-rolled by a pilger mill to obtain a rolled tube having an outer diameter of 46 mm and an inner diameter of 39.8 mm. In addition, the working degree (the reduction in area) in this cold rolling was 88.9%. Here, the cross-sectional reduction rate is obtained by the following equation.
Cross-sectional reduction rate (%) = [(cross-sectional area before processing-cross-sectional area after processing)
/ Cross section before processing] × 100

Thereafter, each of the various types of rolled blanks obtained above is subjected to a plurality of cold-drawing operations several times, and the outer diameter is 7.8 to 10.0 mm, the bottom thickness is 0.25 to 0. A 30 mm draw tube was obtained. Incidentally, the working ratio in the whole of this cold drawing was 95.1 to 97.0% in terms of reduction in area. Further, the total working ratio in cold rolling and cold drawing, ie, the total working ratio in cold working, was 98.9 to 99.3% in terms of reduction in area. Furthermore, one or more intermediate annealings were performed in the above-described drawing process. Then, after final drawing processing, intermediate annealing was performed to manufacture a raw pipe for rolling processing.

The various raw pipes thus obtained are subjected to ball rolling in the same manner as in the prior art, and various inner surfaces having a spiral inner groove form and shape as shown in FIGS. 1 and 2. A grooved tube was obtained. The inner grooved tube has an outer diameter of 7.0 mm, a thickness (t) of 0.23 mm, a fin height (h) of 0.22 mm, a fin apex angle (γ) of 13 °, and a groove. It was formed so as to have the dimensional specifications of the number of lines: 44 and the lead angle (α): 28 °.

Next, after performing final annealing at the annealing temperature: 550 ° C. for the various inner grooved tubes obtained above (however, since the recrystallization temperature rises in a copper alloy to which Ni is added by 0.1% or more, annealing) The temperature was set to 650 ° C.), and copper tubes No. 1 and 2 were used as seamless tubes for heat transfer tubes of the cross fin tube type heat exchanger. I got 1-29.

Test copper tube No. In the cases of 19, 23 and 27, since a Cu material having a high P content is used, defects such as cracks occur in the pipe making process, and processing can not be performed to the end, and corrosion is caused. It was not possible to obtain a copper tube that could be subjected to the test. Moreover, the test copper pipe No. In the case of No. 24, since a Cu material having a high Sn content is used, a defect such as a crack occurs in the hot step, so that copper can not be processed to the end and can be subjected to a corrosion test. I could not get a tube. Furthermore, the test copper pipe No. In the case of No. 28, since a Cu material having a high Ni content is used, a defect such as a crack occurs in the cold process, and the copper can not be processed to the end and can be subjected to a corrosion test. I could not get a tube.

Then, with respect to the various prepared inner grooved tubes (test copper tubes No. 1 to 29), an ant-like corrosion test was carried out using the test apparatus shown in FIG. In FIG. 3, 2 is a 2 L poly container which can be sealed with a cap 4, and a test copper pipe 10 is passed through the cap 4 so as to penetrate a silicon plug 6 attached. The lower end opening of the test copper tube 10 is closed by a silicon plug 8 while being inserted into the poly container 2 at a predetermined depth. Here, the test copper tube 10 has a length of 18 cm, and the length of the portion exposed in the poly container 2 is 15 cm. Further, 100 ml of a formic acid aqueous solution having a predetermined concentration is accommodated in the poly container 2 in such a form that the formic acid aqueous solution does not come in contact with the test copper tube 10.

Moreover, in the nest corrosion test of ant, in a state where a predetermined test copper pipe 10 is set in a poly container 2 containing the formic acid aqueous solution 12 with the formic acid concentration of the formic acid aqueous solution 12 being 0.1%. By leaving the bath outside for 2 hours / day and keeping it at room temperature (15 ° C.), dew condensation on the surface of the test copper tube 10 is caused by the temperature difference. I urged. And the corrosion test under such conditions was carried out for 80 days.

Then, for each test copper pipe subjected to such corrosion test, the cut surface of the portion exposed in the poly container 2 shown in FIG. 3 is examined, the maximum corrosion depth is measured, and the result is The results are shown in Table 2 below.

As apparent from the results of Table 2, in the case of a corrosion test using a 0.1% aqueous solution of formic acid, P is contained in the range of 0.15 to 0.5% by mass according to the present invention, and Test copper tube No. 1 containing at least one element of Zn, Sn and Ni in a total amount in the range of 1.0 to 5.0% by mass. In 1 to 17, it was recognized that there was no occurrence of ant-like corrosion and only slight corrosion of the tube surface.

On the other hand, the test copper pipe No. which is a comparative example is. As for 21, 25, and 29, it was recognized that significant ant-like corrosion had occurred because the P content was less than 0.15% by weight. Furthermore, the test copper pipe No. In 18, 20, 22 and 26, although the P content is within the range of the present invention, any of Zn, Sn, Ni, because the concentration of each additive element is outside the specified range, And significant ant-like corrosion occurred.

2 poly container 4 cap 6 silicon stopper 8 silicon stopper 10 test copper tube 12 formic acid aqueous solution

Claims (9)

1. P is contained in a proportion of 0.15 to 0.50 mass%, and at least one element of Zn, Sn and Ni is contained in a total amount of 0.1 to 5.0 mass%, And the remaining portion is made of Cu and a Cu material which is an unavoidable impurity.
2. The formicary corrosive-resistant copper tube according to claim 1, wherein the content of Zn is 0.1 to 4.0% by mass.
3. The formicary corrosive-resistant copper tube according to claim 1, wherein the Sn content is 0.1 to 4.0% by mass.
4. The formicary corrosive-resistant copper tube according to claim 1, wherein the content of Ni is 0.1 to 4.0% by mass.
5. 5. The multi-layered corrosive-resistant copper tube according to claim 1, wherein the content of the unavoidable impurities is 0.05% by mass or less.
6. A copper tube which is disposed in a wet environment and which is exposed to a corrosive action progressing like a nest of ant from a tube surface to a tube thickness direction from a tube surface by a corrosive medium comprising a lower carboxylic acid. A dovetail-shaped corrosive copper tube according to any one of claims 5 to 10.
7. A heat transfer pipe in an air conditioner or a refrigerator according to any one of claims 1 to 6, which is formed of the formicary corrosive copper tube according to any one of claims 1 to 6.
8. A refrigerant pipe in an air conditioner or a refrigerator according to any one of claims 1 to 6, which is formed of the dovetail corrosive copper tube according to any one of claims 1 to 6.
9. Copper tubes used in air conditioners and refrigeration equipment, placed in a wet environment, improve corrosion resistance against ant-like corrosion that occurs in the wet environment using a lower carboxylic acid as a corrosion medium, which originates from the surface In such a copper tube, P is contained in a proportion of 0.15 to 0.50% by mass, and at least one of Zn, Sn and Ni is added in a total amount of 0. What is claimed is: 1. A method for improving corrosion resistance comprising using a dovetail corrosive-resistant copper tube which is contained in an amount of 1 to 5.0% by mass and the balance of which is Cu and Cu as an unavoidable impurity.

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