阅读说明：本技术 耐蚁巢状腐蚀性优异的铜管 (Copper pipe with excellent ant nest-like corrosion resistance ) 是由 京良彦 玉川博一 大谷良行 于 2017-11-10 设计创作，主要内容包括：提供一种能够对蚁巢状腐蚀发挥更进一步高的耐腐蚀性的、适宜用作空调设备、冷冻设备中的导热管、制冷剂配管等的防腐性优异的铜管。其为以0.15～0.50重量％的比率含有P、余量由Cu和杂质组成的铜管,该铜管的材质中含有P氧化物颗粒,且使该P氧化物颗粒中的当量圆直径为0.1μm以上的颗粒的数密度为50000个/mm<Sup>2</Sup>以下。(Provided is a copper pipe which exhibits a further high corrosion resistance against formicary corrosion and is excellent in corrosion resistance, and which is suitably used as a heat transfer pipe, a refrigerant pipe, or the like in air-conditioning equipment and refrigeration equipment. The copper pipe contains P in a ratio of 0.15 to 0.50 wt%, and the balance being Cu and impurities, and the copper pipe contains P oxide particles in a material thereof, and the number density of particles having an equivalent circle diameter of 0.1 μm or more among the P oxide particles is 50000/mm 2 or less.)

1. A copper pipe excellent in formicary corrosion resistance, characterized by comprising a material containing P in a ratio of 0.15 to 0.50 wt%, with the balance being Cu and impurities, wherein the material of the copper pipe contains P oxide particles, and the number density of particles having an equivalent circle diameter of 0.1 [ mu ] m or more among the P oxide particles is 50000/mm 2 or less.

2. The copper pipe excellent in formicary corrosion resistance according to claim 1, wherein a content of a specific impurity element group consisting of Cr, Mn, Fe, Co, Zr, and Mo in the impurities is 0.01 wt% or less in total.

3. The copper pipe excellent in formicary corrosion resistance according to claim 2, wherein the content of inevitable impurities other than the specific impurity element group in the impurities is 0.005% by weight or less in total.

4. The copper pipe excellent in formicary corrosion resistance according to any one of claims 1 to 3, characterized in that it is a copper pipe which is disposed in a wet environment and is subjected to a corrosion action which progresses in a formicary shape from the pipe surface in the pipe wall thickness direction by a corrosion medium containing a lower carboxylic acid.

5. A method for producing a copper pipe, characterized in that the copper pipe is excellent in formicary corrosion resistance according to any one of claims 1 to 4,

The Cu raw material is melted, the P raw material is added thereto in multiple portions to prepare a Cu melt having the above-mentioned P content, and then the billet is cast and then hot extruded to produce a pipe.

6. A method for manufacturing a copper pipe as claimed in claim 5, wherein the first amount of addition of the P material divided into the plurality of times is such that the Cu melt contains P in a ratio of 0.015 to 0.040% by weight.

7. A method of manufacturing a copper pipe according to claim 5 or 6, wherein the preparation of the Cu melt and the casting of the billet are carried out in an inert gas or reducing gas atmosphere.

8. A heat transfer pipe for air conditioning equipment or refrigeration equipment, characterized by comprising the copper pipe having excellent formicary corrosion resistance according to any one of claims 1 to 4.

9. A refrigerant pipe in an air conditioner or a refrigeration equipment, characterized by comprising the copper pipe excellent in formicary corrosion resistance according to any one of claims 1 to 4.

10. A method for improving corrosion resistance of a copper pipe used in an air conditioner or a refrigeration equipment, which is disposed in a humid environment, against formicary corrosion caused from the surface of the copper pipe in the humid environment using a lower carboxylic acid as a corrosion medium, the method comprising: the copper pipe is a copper pipe containing P in a ratio of 0.15 to 0.50 wt%, and the balance being Cu and impurities, and is configured such that P oxide particles are contained in the material of the copper pipe, and the number density of particles having an equivalent circle diameter of 0.1 μm or more among the P oxide particles is 50000/mm 2 or less.

Technical Field

The present invention relates to a copper pipe having excellent resistance to formicary corrosion, and more particularly to a technique for improving the corrosion resistance to formicary corrosion of a copper pipe suitable for use as a heat transfer pipe, a refrigerant pipe, or the like in air conditioning equipment and refrigeration equipment.

Background

Heretofore, phosphorus (P) deoxidized copper pipe (JIS-H3300-C1220T) which is excellent in corrosion resistance, brazeability, thermal conductivity, bending workability and the like has been mainly used as a pipe material such as a heat transfer pipe and a refrigerant pipe (in-machine pipe) in air-conditioning equipment and refrigeration equipment.

However, it has been found that the phosphorus deoxidized copper pipe, which is a pipe material used in air conditioning equipment and refrigeration equipment, may undergo abnormal corrosion that progresses in a formicary shape in a pipe wall thickness direction from the pipe surface, so-called formicary corrosion. It is considered that this formicary corrosion occurs in a wet environment using a lower carboxylic acid such as formic acid or acetic acid as a corrosive medium, and it is confirmed that the same corrosion occurs in an environment in which a chlorine-based organic solvent such as 1,1, 1-trichloroethane, a certain lubricating oil, formaldehyde, or the like is present. It is known that the above corrosion is remarkably generated when the pipe is used as a conduit causing dew condensation in air conditioners and refrigerators. Further, the formicary corrosion rapidly progresses when it occurs, and progresses to penetrate the copper pipe in a short time, which causes a problem that the device cannot be used.

Therefore, WO2014/148127 proposes a high corrosion resistance copper tube, which is characterized by being made of a Cu material containing P (phosphorus) in a ratio of 0.05 to 1.0 wt%, and the balance being Cu (copper) and inevitable impurities, and thereby showing that the corrosion resistance to formicary corrosion can be improved. That is, the following fact is thus pointed out: in the field where the P content is increased, a copper pipe having corrosion resistance against formicary corrosion further improved as compared with the conventional pipe made of phosphorus deoxidized copper can be obtained in a practical aspect.

However, even in such a copper pipe obtained by increasing the P content, the formicary corrosion may occur in a more severe corrosion environment, and therefore, development of a copper pipe having further high corrosion resistance against the formicary corrosion has been desired.

Disclosure of Invention

problems to be solved by the invention

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to solve the above-mentioned problems, to provide a copper pipe which exhibits further high corrosion resistance against formicary corrosion and is excellent in corrosion resistance, and which can be suitably used as a heat transfer pipe and a refrigerant pipe in an air conditioner or a refrigeration equipment, and to advantageously improve the life of equipment using such a copper pipe.

Means for solving the problems

Therefore, the present inventors have intensively studied the formicary corrosion in a copper pipe as a pipe material used in an air conditioner, a refrigeration equipment, or the like in order to solve the above-described problems in the prior art, and as a result, they have found the following facts: the corrosion resistance to formicary corrosion can be further advantageously improved by controlling the number density of the P oxide particles having an equivalent circle diameter of 0.1 μm or more contained in the material of the copper pipe containing P at a ratio of 0.15 to 0.50 wt% to a certain value or less, and the present invention has been completed.

That is, the present invention has been made based on the above findings, and the main object thereof is a copper pipe excellent in formicary corrosion resistance, which is characterized by containing P in a ratio of 0.15 to 0.50 wt%, and the balance being Cu and impurities, and being configured such that the material of the copper pipe contains P oxide particles, and the number density of particles having an equivalent circle diameter of 0.1 μm or more among the P oxide particles is 50000 pieces/mm 2 or less.

In one of the preferred embodiments of the copper pipe according to the present invention, the corrosion resistance to the formicary corrosion can be further improved by making the content of the specific impurity element group consisting of Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Zr (zirconium), and Mo (molybdenum) in the impurities to be 0.01 wt% or less in the total amount.

In another preferred embodiment of the copper pipe excellent in the formicary corrosion resistance according to the present invention, the content of unavoidable impurities other than the specific impurity element group among the impurities is 0.005 wt% or less in total.

Furthermore, the copper pipe excellent in the formicary corrosion resistance shown in the present invention can be advantageously used as a copper pipe which is disposed in a wet environment and is subjected to a corrosion action that progresses in a formicary shape from the pipe surface in the pipe wall thickness direction due to a corrosion medium containing a lower carboxylic acid.

Accordingly, the present invention also provides a method for producing a copper pipe having excellent formicary corrosion resistance, which comprises melting a Cu raw material, adding a P raw material thereto a plurality of times to prepare a Cu melt having the above-mentioned P content, casting a billet, and hot-extruding the billet to produce a pipe.

In a preferred embodiment of the method for producing a copper pipe according to the present invention, the first amount of addition of the P material divided into a plurality of times is such that the Cu melt contains P in a proportion of 0.015 to 0.040% by weight.

Further, in the method for producing a copper pipe according to the present invention, it is preferable that the preparation of the Cu melt and the casting of the billet are performed in an inert gas or reducing gas atmosphere.

The present invention also provides a heat transfer pipe and a refrigerant pipe (in-machine pipe) in an air conditioner or a refrigeration equipment, which are made of the above copper pipe having excellent formicary corrosion resistance.

In addition, the present invention also provides a method for improving corrosion resistance of a copper pipe used in an air conditioner or a refrigeration equipment, which is disposed in a humid environment, against formicary corrosion caused by a lower carboxylic acid as a corrosive medium from the surface thereof in the humid environment, wherein the following copper pipe is used as the copper pipe: the copper pipe is a copper pipe containing P in a ratio of 0.15 to 0.50 wt%, and the balance being Cu and impurities, and is configured such that P oxide particles are contained in the material of the copper pipe, and the number density of particles having an equivalent circle diameter of 0.1 μm or more among the P oxide particles is 50000/mm 2 or less.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a practical copper pipe which exhibits corrosion resistance against formicary corrosion more excellent than the conventionally known copper pipes, and to use such a copper pipe as a heat transfer pipe in an air conditioner or a refrigerator, a refrigerant pipe (in-machine pipe), or the like, thereby advantageously exhibiting characteristics such as a more effective improvement in the life of these devices.

Drawings

Fig. 1 is a cross-sectional explanatory view showing an outline of a corrosion resistance test apparatus used in examples.

Detailed Description

The copper pipe excellent in the formicary corrosion resistance shown in the present invention is characterized in that the copper pipe is formed so that the P content of the Cu material constituting the copper pipe is in the range of 0.15 to 0.50 wt%, and the material of the copper pipe contains P oxide particles, and the number density of particles having an equivalent circle diameter of 0.1 μm or more among the P oxide particles is 50000 pieces/mm 2 or less. Thus, by containing P at a high concentration and controlling the number density of the P oxide particles of a predetermined size or larger, the entire surface corrosion or pitting corrosion can be effectively changed to a form other than the formicary corrosion even in a more severe corrosion environment, and the corrosion resistance to the formicary corrosion can be further improved.

In particular, if the P content in the copper pipe is less than 0.15 wt%, a selective corrosion mode in which corrosion progresses in a formicary shape is likely to occur, and therefore, in the present invention, the P content needs to be 0.15 wt% or more. On the other hand, even if the P content is increased to more than 0.50 wt%, there is little change in corrosion resistance against formicary corrosion, but in the case of producing a copper pipe, workability is lowered and problems such as cracks are likely to occur, so the upper limit of the P content needs to be controlled to 0.50 wt%.

In the copper pipe excellent in the formicary corrosion resistance shown in the present invention, when the number density of particles having an equivalent circle diameter of 0.1 μm or more among the P oxide particles contained in the material of the copper pipe exceeds 50000 particles/mm 2, a selective corrosion mode in which corrosion progresses in a formicary shape is caused in a more severe corrosion environment, and therefore, in the present invention, the number density of P oxide particles having an equivalent circle diameter of 0.1 μm or more contained in the material of the copper pipe is limited to 50000 particles/mm 2 or less.

It should be noted that, at the present stage, the reason why the corrosion resistance is improved by controlling the number density of the P oxide particles of the prescribed size or more to a specific value or less in the present invention is considered as follows. That is, in the copper pipe having a large P content according to the present invention, when the copper pipe is exposed to a corrosive environment, P in the copper pipe material reacts with water in the environment to dissolve, and phosphoric acids such as orthophosphoric acid and polyphosphoric acid (hereinafter, referred to simply as phosphoric acids) are produced. Since these generated phosphoric acids have an action of inhibiting the formicary corrosion, it is extremely important to improve the corrosion resistance to the formicary corrosion in that the phosphoric acids are efficiently generated from the copper tube when the copper tube is exposed to a corrosive environment. However, when P contained in the copper pipe material is oxidized and exists in the form of P oxide particles in the form of P2O5 or the like, it is difficult to sufficiently exhibit the above-described effect of improving the corrosion resistance. In particular, if the number density of the P oxide particles having an equivalent circle diameter of 0.1 μm or more contained in the material of the copper pipe exceeds 50000 particles/mm 2, the presence of the P oxide particles affects the corrosion resistance-improving effect, and a significant proportion of P present in the material of the copper pipe is consumed as P oxide, and the P concentration distribution in the mother phase becomes uneven, and the P oxide particles themselves give an accelerating effect at the start point of corrosion and in the propagation thereof, thereby causing a decrease in corrosion resistance. Therefore, it is considered that the corrosion resistance to the formicary corrosion is further improved by appropriately controlling the number density of the P oxide particles in the copper pipe.

In the case where a target copper pipe is produced using a Cu raw material having the composition of the present invention as described above, for example, an ingot such as an ingot or billet made of a Cu raw material having the composition described above is used and produced through the steps of casting, homogenization treatment, hot extrusion, rolling, drawing, annealing, and the like, and in this case, the ingot is formed as follows.

That is, in order to make the number density of particles having an equivalent circle diameter of 0.1 μm or more among the P oxide particles contained in the material of the copper pipe satisfy 50000 pieces/mm 2 or less, in casting as a main generation source of the P oxide particles, it is advantageous to adopt the following method: as an atmosphere in the step from melting to solidification of the Cu raw material, it is advantageous to use a non-oxidizing gas such as an inert gas or a reducing gas, and it is particularly preferable to carry out these steps in a reducing gas, and further to add the added P raw material in 2 portions in order to remove O (oxygen) from the Cu raw material (melt). In this case, the amount of P to be added first is adjusted so that the content of the P to be added to the Cu melt is about 0.015 to 0.040 wt% based on the Cu melt for deoxidation of the Cu melt, and then the remainder of the P raw material is added so that a predetermined P content is obtained. This is advantageous in that O (oxygen) is efficiently removed from the Cu material (melt) as a P oxide formed by reaction with P in the Cu melt, and a copper pipe material having a predetermined P content can be obtained.

The copper pipe excellent in the formicary corrosion resistance shown in the present invention is made of a material having a P content other than the above-described P content and the balance of Cu and impurities, and in the present invention, the corrosion resistance of the copper pipe is further improved by limiting the content of a specific impurity element group consisting of Cr, Mn, Fe, Co, Zr, and Mo to 0.01 wt% or less in the total amount in particular among such impurities. Since these specific impurity elements are likely to form compounds with P by heat treatment such as annealing, the resulting P-based precipitates reduce the corrosion resistance of the copper pipe.

Further, among the impurities contained together with Cu in the copper pipe material, in addition to the above specific impurity element group, elements such As S, Si, Ti, Ag, Pb, Se, Te, Bi, Sn, Sb, and As are present As inevitable impurities, and it is generally preferable to adjust such inevitable impurities to 0.005 wt% or less in total.

As the Cu material in which the content of such specific impurity element group and the inevitable impurity elements other than the specific impurity element group is reduced, industrial pure copper whose purity is improved by a conventionally known smelting technique, for example, electrolytic copper whose purity is improved so that the Cu content becomes 99.99 wt% or more can be favorably used.

The dimensions such as the outer diameter and the wall thickness of the copper pipe of the present invention obtained as described above can be appropriately selected according to the application of the copper pipe. Further, when the copper pipe according to the present invention is used as a heat transfer pipe, it is effective to use a heat transfer pipe provided with inner surface grooves (ridges) and outer surface grooves (ridges) in various forms by performing various known inner surface processing and outer surface processing as is well known, in addition to smooth inner and outer surfaces. When used as a refrigerant pipe, a copper pipe having smooth inner and outer surfaces is generally used.

Furthermore, the copper pipe according to the present invention can be suitably used as a heat transfer pipe, a refrigerant pipe, or the like in air conditioning equipment, and can also be suitably used as a heat transfer pipe, a refrigerant pipe (in-machine pipe), or the like in refrigeration equipment.