JP2001183089A - Anti-corrosion copper or copper alloy pipe having bent segment, its manufacturing method and water supplying and hot water supplying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-corrosion copper or copper alloy pipe having a bent segment, its manufacturing method and water supplying and hot water supplying device in which any water quality can be applied in reference to a difference in applied environment or the like and the anti-corrosion characteristics such as anti-hole corrosion characteristic and anti-corrosion characteristic or the like can be kept for a long period of time ranging from a low temperature to a high temperature. SOLUTION: An inner surface of a copper or copper alloy pipe having a bent segment is formed with amorphous ceramics film. Either copper or copper alloy pipe having this bent segment is manufactured by a method wherein the amorphous ceramics film is formed upon performing a bending work of the copper or copper alloy pipe or after the amorphous ceramics film is formed, the bending work is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion-resistant copper or copper alloy pipe having a bent portion used for architectural piping for hot and cold water supply, air conditioning and heating, a heat exchanger for a water heater, a heat exchanger using water, and the like. More particularly, the present invention relates to a corrosion-resistant copper or copper alloy tube having a bent portion having excellent corrosion resistance such as pitting and erosion to water or an aqueous solution, a method for producing the same, and a water supply / water heater using the same.

[0002]

2. Description of the Related Art Generally, copper and copper alloy pipes (hereinafter, copper and copper alloy pipes are collectively referred to as copper pipes) are excellent in corrosion resistance, toughness, ductility, brazing property, etc. Construction pipes for passing water or aqueous solution through, hot water heaters,
Used in heat exchangers and water heat exchangers. this is,
This is because high corrosion resistance to water is required in a wide temperature range from a low temperature to a high temperature. However, even when copper having such high corrosion resistance is used, particularly in the case of highly corrosive water quality, a through hole is formed in a part of the copper pipe due to corrosion during use, and water or the like in the inside leaks out. Accidents that can not be used as applications are likely to occur.

[0003] These accidents are often caused primarily by pitting. Pitting corrosion is corrosion in which a small part of the inner surface of a copper tube is corroded in the thickness direction of the tube to form point-like holes. Pitting is likely to occur in the vicinity of a bent portion, in a portion where the flow velocity is slow, and in a stagnant portion of water flowing in a pipe such as a joint portion and its vicinity. In these portions, deposits are easily formed on the inner surface of the tube, and oxygen concentration cells are formed in those portions, and pitting occurs under the deposits. Such pitting corrosion is caused by water quality (pH, SO ₄ ²⁻ /
HCO ₃ ^- and residual chlorine, soluble silicic acid, free carbonic acid, etc.) vary in their likelihood of occurrence. There is water treatment as a countermeasure against pitting, but it is difficult to change water quality as a practical problem.
Measures from the material side are required.

In particular, in a bent portion of a copper pipe for hot water supply or hot water supply or a return pipe having a low water pressure, the dissolved gas is liable to vaporize due to a change in the flow velocity, and the friction between the bubbles and the inner surface of the copper pipe and the mechanical shock such as an impact due to destruction. Erosion is likely to occur on the inner surface of the copper tube due to mechanical forces. As a countermeasure, a design change (reduction of the curvature and the number of the bent portion, etc.) and a restriction of the flow velocity are considered, but it is often difficult to realize the countermeasure, and therefore, a countermeasure from the material side is required. .

Conventionally, in order to prevent pitting, the following measures have been taken from the viewpoint of materials. Normally, when copper is cast to form a copper tube, a carbon film is inevitably present on the inner surface of the copper tube due to residual copper tube processing oil. This is because when the copper tube coil is annealed after drawing the copper tube using the drawing lubricating oil, when the drawing lubricating oil remaining in the tube is decomposed and discharged outside the tube, the lubricating oil is decomposed. Is insufficient, or the lubricating oil remains inside the copper pipe or carbides are formed inside the copper pipe after the annealing is completed while the decomposed lubricating oil is not discharged out of the pipe. When water is passed through a copper pipe containing a large amount of residual oil residue, a local battery is easily formed, and pitting is likely to occur. Therefore, the first
Is a method of removing residual carbon and residual oil.

[0006] The residual carbon and residual oil can be removed by heating and burning in air, but the copper tube is oxidized at the same time, and it is difficult to control this. Therefore, in the method for manufacturing a heat exchanger described in, for example, Japanese Patent Application Laid-Open No. 5-126483, in order to prevent the carbon film from remaining, the copper tube is heated during the manufacturing process to burn the carbon film, and the residual carbon film is slightly removed. There is disclosed a technique for removing carbon by press-fitting, for example, air or water together with oxides generated during heating. Further, in order to reduce the amount of residual coal, there is a method of purging the inside of the copper tube with an inert gas and annealing it, or a method of sucking the gas inside.

As a second method for preventing pitting corrosion, there is a method of forming a protective film on the inner surface of a pipe. For example, a method of oxidizing the inner surface of a copper tube under appropriate conditions to reduce the amount of residual carbon in the tube, and forming an oxide film of CuO and / or Cu ₂ O (hereinafter, referred to as a copper oxide film) (Japanese Patent Laid-Open No. Hei 6 (1994)). −4962
0) or a method of forming a Sn coating layer by plating the inner surface of a copper tube with Sn (US Pat. No. 2,282,511).

[0008] As a third method, there is a method of improving the pitting corrosion resistance by alloying copper forming the tube. For example, the piping described in JP-A-6-184669 is
r is 0.005 to 1% by weight and P, Sn, Ag, Ti
Further, it is formed from a copper alloy containing a small amount of R (a rare earth element other than Y) and contains Zr to improve pitting corrosion resistance (conventional example 2). Kobe Steel Technology Vo
l.38 No.4 (1988) is made of a Cu-Al-Sn-based alloy. By adding a small amount of Al and Sn, it is possible to suppress an increase in the spontaneous potential of the copper tube. Pitting corrosion resistance can be improved as compared with a copper tube made of deoxidized copper (conventional example 3).

As a countermeasure against erosion from the material side, similarly to the countermeasure against pitting corrosion, a copper tube having a plated film formed on the inner surface (Japanese Patent Laid-Open No. 8-120456), improvement in strength and corrosion resistance by alloying. Copper tube (JP-A-61-
231131), and a copper tube having an inner surface coated with a resin (JP-A-9-242983).

[0010]

However, in the method of reducing the amount of residual coal, such as Conventional Example 1 shown in the first method, it is difficult to prevent corrosion from corrosive factors in water quality, and pitting corrosion is difficult. And the fundamental solution to erosion is difficult. Furthermore, in the method of purging or suctioning an inert gas in a pipe, it is necessary to modify the annealing equipment, and in the case of a long coil, it is necessary to increase the annealing time, so that the productivity is reduced. There is a problem.

In the method of forming a protective film on the inner surface of the tube according to the second method, when a copper oxide film is used as the protective film, the formed copper oxide film is brittle and has a film thickness effective for corrosion resistance. Since it is difficult to form a thick oxide film, it is difficult to maintain sufficient corrosion resistance for a long time. Also, if the oxide film is partially peeled off, a local battery is formed,
There is a problem that the corrosion resistance is liable to be lowered.

When an Sn coating layer is formed as a protective film, plating for forming the Sn coating layer is necessary. However, in order to perform plating inside a long copper tube, electroless plating is required. . In electroless plating, defects such as pinholes are likely to exist. Also, if residual carbon, residual oil, oxides, or the like remains inside the copper tube, the adhesion strength of Sn plating decreases,
The plating coating is easily peeled off partially. When the plating is partially peeled off, the corrosion resistance is rather lowered due to the formation of a local battery. In addition, when used at a high temperature, such as a copper pipe for hot water supply, Sn of the plating layer and Cu of the base material react with each other, and the Sn plating layer changes to a brittle intermetallic compound, so that it is easily peeled off. In addition, there is a problem that the potential is higher than that of the base material and the corrosion resistance of the copper tube is reduced.

As a third method, the method of alloying copper described in Conventional Examples 2 and 3 and the like involves changing the natural electrode potential of copper by alloying copper and reducing the hardness of copper. Corrosion resistance is improved due to the increase. However, due to alloying, deformation resistance and work hardening coefficient are increased, so that problems such as an increase in the number of times of annealing during production and production of small-diameter pipes become difficult occur, and an increase in production cost is liable to occur. .

Further, the method of coating the inner surface with a resin has a problem that the adhesiveness between the resin and the copper tube is deteriorated due to aging. In addition, it is necessary to consider in advance the recycling of the inner resin-coated copper tube.

As described above, corrosion factors include external factors (water quality), formation of a corrosion battery due to a local increase in potential due to adhesion of organic substances to the surface, etc., and corrosion battery due to the appearance of a density portion of dissolved carbon in water quality. It is possible to elute metals (existing local anodes) due to the transfer of electrons using water as a catalyst when a corrosion battery is formed. However, at present, high corrosion resistance to such corrosion factors is considered. No copper or copper alloy tube to have.

The present invention has been made in view of the above-mentioned problems, and is capable of improving corrosion resistance such as pitting corrosion resistance and erosion resistance from a low temperature to a high temperature for a long time regardless of the water quality due to a difference in use environment. An object of the present invention is to provide a corrosion-resistant copper or copper alloy tube having a bent portion that can be maintained, a method for producing the same, and a water / water heater using the same.

[0017]

According to the present invention, there is provided a corrosion-resistant copper or copper alloy tube having a bent portion, wherein the copper or copper alloy tube having a bent portion has an amorphous ceramic coating on the inner surface of the copper or copper alloy tube. Is formed.

In the present invention, ceramics do not react with water and aqueous solutions and are chemically stable to aqueous fluids, have sufficient hardness, and are resistant to friction with water. By forming an amorphous ceramic film having such properties on the inner surface of a copper tube, a highly corrosion-resistant copper or copper alloy tube having ideal characteristics against pitting, erosion and other corrosion is obtained. Can be.

Further, copper or copper alloy tubes having a bent portion having an amorphous ceramic film formed on the inner surface thereof, or a copper or copper alloy tube having a bent portion having an amorphous ceramic film formed on the inner surface thereof and a straight tube It is preferable that the copper or copper alloy tube is joined by brazing or the like, and the amorphous ceramic film is not formed at the joint. Note that the joint is an area where the copper tubes to be joined overlap each other. That is, when one copper pipe is expanded, the end of the other copper pipe is inserted into the copper pipe, and the copper pipes are overlapped at this end, an overlapping area is a joint. The copper tubes are joined together by brazing material or the like at the part.

Further, the radius of curvature at the inside of the bend of the bent portion is R [mm], and the outer diameter of the copper or copper alloy tube is D [m].
m], it is preferable that R / D is 0.5 or more.

Further, the thickness of the amorphous ceramic film is preferably 0.1 to 100 μm.

Preferably, the hardness of the amorphous ceramic film is 3H to 10H as a pencil scratch value.

Further, the center line average surface roughness Ra in the tube axis direction on the inner surface of the copper or copper alloy tube is 0.5 μm or less;
Moreover, it is preferable that the maximum surface roughness Rmax is 1.0 μm or less.

Further, when the crystal grain size in the thickness direction of the copper or copper alloy tube is d [μm] and the radius of curvature at the bent portion is R [mm], at least d / R at the bent portion. It is preferred that ≦ 20.

The thickness of the oxide film existing between the amorphous ceramic film and the copper or copper alloy tube is 0.1%.
It is preferably not more than μm.

The method for producing a corrosion-resistant copper or copper alloy tube having a bent portion according to the present invention comprises the steps of forming a bent portion in a copper or copper alloy tube by bending, and forming an amorphous surface on the inner surface of the copper or copper alloy tube. Forming a ceramic film.

[0027] Another method for producing a corrosion-resistant copper or copper alloy tube having a bent portion according to the present invention comprises the steps of: forming an amorphous ceramic film on the inner surface of the bent or bent copper alloy tube;
Forming a bent portion by bending the copper or copper alloy tube.

According to the present invention, there is provided a water heater / water heater using a corrosion-resistant copper or copper alloy tube having a bent portion according to the present invention, wherein the corrosion-resistant copper or copper alloy tube having a bent portion according to any one of claims 1 to 9 is used.
It is characterized by being used more than once.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. As described above, copper pipes used for architectural piping or heat exchangers need to be excellent in wear resistance and corrosion resistance without peeling off even when used for a long time regardless of differences in temperature or water quality. is there. The inventors of the present application have conducted intensive studies to solve such a problem of copper tube corrosion. As a result, since the amorphous ceramic film is chemically stable and does not react with water and an aqueous solution, this film is formed on the copper tube. It has been found that corrosion resistance can be improved by forming it on the inner surface. Then, a corrosion-resistant copper or copper alloy tube having a bent portion and a method for manufacturing the same have been found.

Ceramics are chemically stable to aqueous fluids without reacting with water and aqueous solutions. Moreover, since it has sufficient hardness, it is resistant to friction with water. Therefore, it has ideal properties against pitting, erosion and other corrosion. However, ordinary crystalline ceramics have lower ductility than metals, and it is difficult to adopt applications for performing plastic working such as bending.

The inventors of the present invention focused on the fact that some amorphous ceramics have the same strength as crystalline ceramics, but have higher ductility than crystalline ceramics. By forming a thin film of amorphous ceramics on the inner surface of the tube, the inventors have invented a target corrosion-resistant copper or copper alloy tube and a method for producing the same. Furthermore, it has been found that by using such a corrosion-resistant copper or copper alloy pipe, a water supply / water heater having excellent corrosion resistance can be obtained. Further, the corrosion-resistant copper or copper alloy pipe of the present invention is suitable for recycling because amorphous ceramics formed on the inner surface by re-melting are separated on the surface of the molten metal and become slag.

In the present invention, the copper tube having a bent portion is, for example, a copper tube having a bent portion such as a U shape, an L shape, an S shape, and a spiral shape. The number of bent portions may be one or more. Also,
Corrosion resistant copper or copper alloy tubes can also be joined together.

The copper tube used in the present invention may be made of oxygen-free copper, phosphorous deoxidized copper, tough pitch copper, Cu-Fe
-P, Cu-Mn-P, Cu-Ni-Si, Cu-Sn
-P and Cu-Zn, etc., but any other copper alloy can be applied as long as it can be processed into a tube.
In view of the adhesive strength of the amorphous ceramic film to the inner surface of the copper tube and the prevention of swelling at the interface between the inner surface of the copper tube and the ceramic film, the amount of oxygen contained in the copper tube is 30 ppm by mass or less, Preferably, the amount is less than 2 ppm by weight.

The shape of the copper tube is almost a smooth tube for architectural use, but can be applied to all shapes such as an inner grooved tube and a corrugated tube.

In the present invention, the amorphous ceramic film formed on the inner surface of the copper tube is, for example, SiO ₂ , ZrO ₂ , S
A mixture of a metal alkoxide-based polymer containing iO ₂ · ZrO ₂ , Al ₂ O _3, TiO _2, etc., to which an inorganic filler is appropriately added, diluted with alcohol to an appropriate concentration, and sprayed, dipped and coated. Is supplied to the inside of a copper tube by a method, and the copper tube is placed in a reducing or non-oxidizing atmosphere for 50 to 50 minutes.
It can be prepared by heating to a temperature of 0 ° C. for a predetermined time and cooling to room temperature.

The amorphous ceramic formed on the inner surface of the copper tube in this way is dense and impermeable to moisture, and has ductility to follow the plastic working (bending, can expansion, etc.) and expansion and contraction of the copper tube. Can be deformed and deformed, has high hardness, is not easily consumed by abrasion with water, has a smooth surface, does not disturb the flow of water or aqueous solution, and hardly causes precipitation of insoluble components contained in the aqueous solution, water and aqueous solution And does not react with water repellency,
It does not corrode and deteriorate even in water or aqueous solution for a long time, it has no conductivity, so it is difficult for ions dissolved in aqueous solution to precipitate, and its adhesion with copper or copper alloy is strong. It has many excellent properties, such as being able to maintain corrosion resistance stably for a long time, stable from low temperature to high temperature, and maintaining excellent corrosion resistance irrespective of temperature change of the aqueous solution. It is most suitable for imparting properties such as pitting and erosion. In addition, for example, when an amorphous ceramics film is formed on the inner surface of a copper tube and put into a melting furnace, the amorphous ceramics film separates into a molten metal surface and becomes slag in a melting process, so from the viewpoint of recycling. Are better. The copper melt can be regenerated as copper by casting after scouring (degassing and squeezing).

Next, an amorphous ceramic film formed on the inner surface of the copper tube and a method for forming the same will be specifically described with reference to an example. As an amorphous ceramic film, for example, S
i-CH ₃ having a bond and Si-O bond. The Si—CH ₃ bond and Si represented by the following chemical formula 1
An alcohol is added to an alcoholic solution having a structure containing a -O bond to prepare a treatment solution having an appropriate concentration, and this treatment solution is applied to the inner surface of the copper tube. Then, after applying the solution to the inner surface of the copper tube, the solution is heat-treated under appropriate conditions, so that Si
A uniform amorphous ceramic film having —CH ₃ bonds and Si—O bonds is formed.

[0038]

Embedded image

When the treatment liquid is heat-treated, a polycondensation reaction is caused by heating, the oxygen of the OH group is cut off and combined with other oxygen or Si, and an amorphous ceramic having a structure represented by the following chemical formula 2 is obtained. A film is formed.

[0040]

Embedded image

In the structure represented by the chemical formula 2, in order to impart good corrosion resistance and ductility to the amorphous film, it is necessary to use a Fourier transform infrared spectrophotometer (FT-IR).
Si-CH ₃ by rmation-infrared spectroscopy)
Area ratio of stretching peak of Si—O bond to bond (Si—
O) / (Si—CH ₃ ).
It is preferable to set this value to 8 to 20 for the following reason.

The magnitude of the expansion / shrinkage peak area ratio (Si—O) / (Si—CH ₃ ) of the Si—CH ₃ bond to the Si—O bond of the amorphous ceramic film by FT-IR (hereinafter, referred to as peak area ratio). The length corresponds to the number of methyl groups in the amorphous structure of the film. As shown in Chemical Formula 2, the film
When a methyl group binds to i ⁴⁺ , the Si ⁴⁺ network is broken. The peak area ratio corresponds to the number of defects in the amorphous structure of such a film, and affects the hardness and deformability of the film. If the peak area ratio is less than 8 and the number of methyl groups is large, the number of defects in the amorphous structure is increased and the strength of the film is reduced, and even when the film is not formed, the corrosion resistance cannot be maintained for a long time. . On the other hand, if the peak area ratio exceeds 20 and the number of methyl groups is small, the defects in the amorphous phase are reduced and the deformability of the film is reduced, and the copper or copper alloy pipe is bent or the base material is thermally expanded by heating. It is not easy to follow and cracks easily occur. Therefore, the peak area ratio is 8 to 20.
It is preferable that

Note that the infrared absorption spectrum was
For TR (Attenuated Total Reflection) infrared spectroscopy
It can be measured more, for example, manufactured by Perkin Elmer
FT-IR Paragon1000 (MCT (Magnetron Co.)
mputed Topography) with detector), Au for microscopic observation
Combination with to Image System and conical Ge crystal
8cm resolution^-1100 times of integration
Area 100 × 100μm ^TwoCan be measured under the conditions of
You. Figure 1 shows the measured infrared absorption of the amorphous ceramic film.
It is a graph which shows an example of a spectrum. Figure 1
The horizontal axis indicates the wave number, and the vertical axis indicates the absorption intensity. Note that this
The coating is applied to the inner surface of the copper tube to form an amorphous ceramic coating.
After applying the physical solution, 99.99% N_TwoIn a gas atmosphere
At a heating rate of 60 ° C./min, a heating temperature of 500 ° C.
Heating with a heat retention time of 15 minutes and a cooling rate of 10 ° C / min
Processed to form an amorphous ceramic film.
You. Amorphous ceramic film formed by this
The thickness was 0.7 μm and the surface roughness Ra was 0.2 μm.

As shown in FIG. 1, in the obtained infrared absorption spectrum, the area of the absorption peak derived from the Si—CH ₃ stretching vibration appearing at 1300 to 1200 cm ⁻¹ ,
The ratio of the area of the absorption peak derived from Si—O stretching vibration appearing at 1200 to 900 cm ⁻¹ is defined as the peak area ratio.
In Figure 1, Si-CH ₃ area of absorption peak derived from stretching vibration 48.837, Si-CH ₃ area of absorption peak derived from stretching vibration becomes 3.0489, which peak area ratio of about 16 0.0.

In an amorphous ceramic film having a Si—CH ₃ bond and a Si—O bond as shown in the chemical formula 2, the Si—O bond is a covalent bond and therefore has a strong bonding force. Excellent in nature. In addition, Si
The Si ⁴⁺ network is cut by the —CH ₃ bond, and therefore the film does not peel off from the copper tube because the film has excellent deformability in conformity with molding or thermal expansion of the copper tube. Also, since the film is made of amorphous ceramics,
It is extremely dense and excellent in water repellency. Therefore, by forming such an amorphous ceramic film on the inner surface of the copper tube, it has extremely excellent wear resistance and corrosion resistance, and even if used for a long time, A copper tube free from corrosion such as corrosion can be obtained.

In the Si—CH ₃ bond and the Si—O bond, since the methyl group starts to be eliminated by heating, the ratio of the number of bonds can be changed depending on the heating conditions after the application of the treatment liquid. The properties of the porous ceramic film can be changed.

The above description has been made on the amorphous ceramics having a Si—CH ₃ bond and a Si—O bond.
₂ , even in the case of a metal alkoxide-based polymer containing SiO ₂ .ZrO ₂ , Al ₂ O _3, TiO _{2 and the} like as main components,
Similarly, the peak area ratio by each FT-IR (Zr-O)
/ (Zr-CH _3), to form the value by amorphous ceramic coating which is an object of (Al-O) / (Al -CH 3) and (Ti-O) / (Ti -CH 3) Will be possible. Also in these peak area ratios, in order to impart ductility together with good corrosion resistance, the above (Si—CH ₃ ) /
For the same reason as the peak area ratio of (Si—O), it is preferably 8 to 20.

The temperature at which the amorphous ceramics film is formed can be selected from room temperature to 500 ° C. in consideration of the timing of bending or the properties to be imparted to the film. Also, in the early stage of heating, an oxide film is easily formed between the copper tube and the amorphous ceramics film, and if the heating rate during heating and the cooling rate after heating are fast, the difference in linear expansion between copper and ceramics will increase. Thereby, the film is easily peeled off. Therefore, when performing the heat treatment, a non-oxidizing or reducing atmosphere is desirable. In particular, when heating to a temperature of 300 ° C. or more, 600 ° C. /
It is preferable to heat at a rate of not more than 1 minute, then hold for 5 to 300 minutes, and cool at a rate of not more than 100 ° C./minute.

As described above, by appropriately regulating the atmosphere during the heat treatment, the temperature rising and falling rates, and the heating holding temperature and the heating holding time, the copper tube is oxidized at the time of the heat treatment, and the surface of the copper tube and the amorphous ceramic film are formed. This prevents the oxide film such as a copper oxide film from being formed at the interface of the film, making it easy for the film to peel off, and prevents the film from cracking or peeling due to the difference in the coefficient of linear expansion between ceramics and copper. Therefore, an amorphous ceramic film having excellent adhesion and deformability to the copper tube can be formed on the inner surface of the copper tube.

The thickness of the amorphous ceramic film can be changed by changing the concentration of the processing solution to be applied, the thickness of the applied solution, the number of times of application, and the like. Further, the treatment liquid may be applied again to the inner surface of the copper tube on which the film is formed and heated to increase the film thickness.

Hereinafter, the reasons for limiting the numerical values, which are constituent elements of the present invention, will be described.

The radius of curvature at the inside of the bend of the bending portion is R
[Mm], and the outer diameter of the copper or copper alloy tube is D [mm].
When bending is performed on a copper tube having an R / D of 0.5 or more and an amorphous ceramic film formed on the inner surface in advance, if the R / D is less than 0.5, the amorphous formed The porous ceramic film is easily peeled off. In addition, the stress generated by the expansion and contraction of the copper tube in use increases, and the amorphous ceramic film is liable to peel off because the flow rate of water or aqueous solution flowing in the tube at the bending portion changes greatly. Become. Therefore,
R / D is preferably 0.5 or more. A more preferable range for the value of R / D is 1.0 or more.

The thickness of the amorphous ceramic film: 0.1
If the thickness of the film is less than 0.1 μm, the film becomes thinner due to friction between the tube and water when the tube is used, and it is difficult to maintain good corrosion resistance for a long period of time. On the other hand, when the film thickness is 100μ
If it exceeds m, the amorphous ceramic film will crack or peel off due to the difference in the coefficient of linear expansion between ceramics and copper when the temperature of the tube is lowered during film formation. This is because the expansion coefficient of copper and copper alloy is about 16 to 18 × 10 ⁻⁶ , whereas the coefficient of linear expansion of the ceramics used in the present invention is 2
This is because it is as small as about 12 × 10 ⁻⁶ . In addition, it is difficult for the coating to follow the deformation of the copper tube base due to the processing, and the coating may peel off. Therefore, the thickness of the film is 0.
The thickness is preferably 1 to 100 μm. A more preferable range for the film thickness is 0.2 to 50 μm. In particular, it is 0.2 to 20 μm, more preferably 0.2 to 10 μm at the bent portion.

Film hardness: Pencil scratch value 3H to 10
The hardness of the H film is determined by the pencil scratch value (JIS K 5400-
When the film thickness is less than 3H in 1990), the film is soft, so that the film is worn away with the increase in use time due to friction between the film and water flowing through the copper tube, and the corrosion resistance is likely to be reduced. on the other hand,
If the hardness is more than 10H, the deformability of the film will decrease,
In the same manner as described above, it becomes difficult for the film to follow the deformation of the copper tube material due to processing or the thermal expansion of the copper tube material due to heating, and the film may peel off. Therefore, it is preferable that the hardness of the film is 3H to 10H as a pencil scratch value.

The center line average surface roughness of the inner surface of the pipe (JIS B
0601-1982): Ra 0.3 μm or less and Rm
ax 0.4 μm or less The surface roughness of the inner surface of the copper tube on which the amorphous ceramic film is formed is determined by the easiness of peeling of the film when water flows through the copper tube and the ionic and insoluble substances contained in water. Affects the ease of precipitation on the amorphous ceramic film. If the center line average surface roughness Ra exceeds 0.3 μm and the maximum surface roughness Rmax exceeds 0.4 μm, turbulence occurs near the coating surface formed in the pipe due to the unevenness of the coating surface. This turbulence may cause the film to peel off. In addition, ions and insoluble substances contained in water are easily deposited on the amorphous ceramic film. Therefore, it is preferable that the center line average surface roughness Ra of the inner surface of the tube be 0.3 μm or less and the maximum surface roughness Rmax be 0.4 μm or less.

The surface roughness of the inner surface of the copper tube on which such an amorphous ceramic film is formed is affected by the surface roughness of the inner surface of the copper tube before the film is formed. Therefore, it is preferable that the surface roughness of the inner surface of the copper tube before forming the film is 0.3 μm or less and the maximum surface roughness is 0.4 μm or less. Further, for example, the center line average surface roughness Ra of the inner surface of the copper tube after forming the amorphous ceramics film using a liquid processing solution or the like can be 0.3 μm or less and the maximum surface roughness Rmax can be 0.4 μm or less. If the surface roughness of the inner surface of the copper tube inner surface substrate is 0.3 μm or more and / or the maximum surface roughness is 0.4 μm
m or more.

Grain size d [μm] of copper tube and bending of bent part
When bending a copper tube on which an amorphous ceramic film having a ratio of a radius of curvature R [mm] d / R ≦ 20 on the inner side is bent, a step occurs at a grain boundary at a bent portion. When this step is large, the deformation of the amorphous ceramic film cannot be followed up and may be peeled off. Also, even if R / D is 0.5 or more, d / R
Exceeds 20, the amorphous ceramic film tends to peel off at the bent portion. Even without peeling, the friction between the step and the water increases, and the amorphous ceramic film is easily peeled off due to this frictional force. Therefore,
d / R is preferably 20 or less. Also, d / R
Is more preferably 10 or less.

[0058] An interlayer is provided between the copper tube and the amorphous ceramic film.
Thickness of existing oxide film: 0.1 μm or less When an oxide film exists between the copper tube and the amorphous ceramic film, the bonding force between the oxide film and the copper tube base is small, so that the oxide film is formed on the oxide film. When an amorphous ceramic film is formed,
Separation easily occurs at the interface between the oxide film and the copper tube base. If the thickness of the oxide film exceeds 0.1 μm, sufficient adhesion strength of the amorphous ceramic film cannot be obtained. For example, when flowing water inside the copper tube, the amorphous ceramic film is peeled off. In the part, a local battery or the like is formed, and pitting corrosion is more likely to occur. Therefore, it is preferable that the thickness of the oxide film existing between the copper tube and the amorphous ceramic film be 0.1 μm or less. The oxide film is obtained by cutting a copper tube on which an amorphous ceramic film is formed by a method that generates less heat, and cutting the cut surface with a scanning electron microscope (Scanning electron microscope).
on a microscope (SEM)) at a magnification of 10,000 or more, and the film thickness can be measured. When the growth of the oxide film is intense, a gap or crack may be observed between the amorphous ceramic film and the copper tube base.

As described later, the thickness of the oxide film is set to 0.1 μm
In order to keep the thickness below 200%, when the total amount of the oxide film formed on the inner surface of the copper tube base before the formation of the amorphous ceramic film is converted into Cu ₂ O, the film thickness should be 200 ° or less. Care must be taken to control the formation atmosphere of the porous ceramic film to prevent oxidation.

There are two types of copper oxidation, cupric oxide (CuO) and cuprous oxide (Cu ₂ O), which differ in the valence of copper and are divalent (Cu ²⁺ ) and copper (Cu ²⁺ ), respectively. Monovalent (C
u ⁺ ). In the case of a copper alloy, an oxide of an alloy element may be formed in addition to the oxide of copper. Such measurement of the oxide film can be performed by an electrochemical method (cathode reduction method). The actual oxide is Cu
There are O, Cu ₂ O, oxides of the additional elements, and the like, and the film thickness when all of them are regarded as Cu ₂ O is defined as the film thickness of the oxide film. Thus, the thickness T (Å) of the oxide film, the molecular weight M (Cu ₂ O: 133.2 (g)), the current density i (mA
/ Cm ² ), the number of electrons n (C
u ₂ O: 2), product density ρ (Cu ₂ O: 6.04 (g)
/ Cm ³ )), Faraday number F (96500 (C / mo
l)), the following equation 1 holds.

[0061]

T = ((M × i × t) / (n × ρ × F)) × 10 ⁵

Next, a method of forming a bent portion will be described. Normally, copper pipes for architectural piping for water supply and hot water supply and for air conditioning and heating or for heat exchangers using water include a bent part in a part of the piping. As a method of forming such a bent portion, a method of bending a copper tube on which an amorphous ceramic film is formed,
Alternatively, it is possible to cope with the above-mentioned application by a method of joining a copper tube with an amorphous ceramic film having a bent portion to a copper tube with an amorphous ceramic film having a bent portion. Also, after bending the copper tube, an amorphous ceramic film is formed on the inner surface thereof, and then joined to a copper tube having another bent portion or not including the bent portion, thereby forming a bent portion as a whole. A copper tube with an amorphous ceramic film having the following may be prepared. In this case, an amorphous ceramic film may be formed on the copper tube in advance.

In the present invention, since the amorphous ceramic film formed on the inner surface of the copper tube generally has poor wettability of brazing materials such as phosphor copper brazing, silver copper brazing and solder, the copper tube provided with the amorphous ceramic film is used. When joining each other by using a brazing material, it is preferable that an amorphous ceramics film is not formed at a joining portion where the brazing material of the copper tube turns. If an amorphous ceramic film is formed at the joint, the amorphous ceramic film may be removed in advance by mechanical or chemical means.

[0064]

The copper tube with an amorphous film having a bent portion according to an embodiment of the present invention will be specifically described below in comparison with a comparative example which is out of the scope of the present invention. In the following examples, common measurement and test methods will be described.

The pencil scratch hardness was measured according to JIS K5400.
The hardness of the test piece was measured according to -1990.

For evaluation of pitting corrosion resistance, a polarization resistance measurement and a running water test were performed. The measurement of the polarization measurement is performed using the following aqueous solution A
The polarization curve of the sample was measured by the anode / cathode polarization method, and the current density at the time of polarization at −100 mV (vs. SCE) with respect to the standard electrode potential was read from the cathode polarization curve. Test pieces were collected from three test materials prepared under the same conditions, and the average of the measured values of the three test pieces was defined as the current density of the sample. It can be determined that pitting corrosion is less likely to occur as the value of the current density is smaller.

The aqueous solution A is pH 6.5, silica (SiO
₃ ^2- ): 60 ppm, bicarbonate ion (HCO ₃ ^2- ): 80 p
pm, chloride ion (Cl ⁻ ): 30 ppm and sulfate ion (SO ₄ ²⁻ ): 20 ppm were all added as sodium salts. The pH value was adjusted with carbon dioxide gas.

In the flowing water test, the following two types of aqueous solutions B and C were applied to a copper tube on which the formed amorphous ceramic film was formed or a copper tube not formed at a predetermined temperature and a flow rate of 0%. Circulation was performed at 0.2 m / sec for 6 months (flowing time was 30 minutes / day). Then, the copper tube after the test was cut in half, the inner surface was observed, the presence or absence of greenish blue was confirmed, and the pitting pit was confirmed by a stereoscopic microscope (magnification: 10 to 50 times). When a pit was found, the pit depth was investigated by observing the cross section. Then, those having no pitting pits and no corrosion were evaluated as ○, 0.02 mm.
Pits less than 0.02
Those having pitting pits of not less than mm were evaluated as x.

The aqueous solution B has a water temperature of 25 ° C., pH 6.5,
Silica (SiO ₃ ^2- ): 60 ppm, bicarbonate ion (HC
O ₃ ^2-): 80ppm, chloride ion ^(Cl -): 30p
pm, sulfate ion (SO ₄ ²⁻ ): A product obtained by adding all 20 ppm with a sodium salt was used. The pH value was adjusted with carbon dioxide gas.

The aqueous solution C has a water temperature of 60 ° C. and a water quality of pH.
6.5, silica (SiO ₃ ^2- ): 60 ppm, bicarbonate ion (HCO ₃ ^2- ): 80 ppm, chloride ion (C
l ^-): 30ppm, sulfate ion (SO ₄ ^2-): 20pp
m, residual chlorine (R-Cl): used was one in which 5 ppm was all added as a sodium salt. The pH value was adjusted with dilute sulfuric acid.

The erosion resistance was evaluated by a running water test. In the flowing water test, the following aqueous solution D having a temperature of 25 ° C. was flowed to the prepared copper tube with an amorphous ceramics film or the copper tube having no amorphous ceramics film at a flow rate of 4.0 m / m.
After the test, the copper tube was cut in half, and the presence or absence of wall thinning due to erosion was examined by observing the inner surface of the copper tube. In particular, the corrosion depth was examined with a microscope in the cross-section near the corrosion-reduced part and the bent part of the copper pipe. If there is no corrosion,
The case where corrosion having a corrosion depth of less than 0.02 mm occurred was indicated by Δ, and the case where corrosion having a corrosion depth of 0.02 mm or more occurred was indicated by x.

[0072] aqueous solution D is, pH 6.5, a chloride ion ^(Cl -): 1000ppm, chloride ion was used which was added at sodium chloride. The pH value was adjusted with sulfuric acid. Table 1 below shows the content of additive ions in the aqueous solutions A to D.

[0073]

[Table 1]

[0074] The first embodiment outer diameter 9.52 mm, wall thickness 0.5mm phosphorus deoxidized copper (JI
(SC1100) A sample having a length of 1000 mm was sampled from a smooth tube coil (annealed) and used as a test material. The oxide film thickness on the inner surface of these copper tubes was 50 ° in terms of Cu ₂ O, and the crystal grain size in the thickness direction was 20 to 80 μm. The center line average surface roughness Ra of the inner surface of the copper tube was 0.3 μm, and the maximum surface roughness Rmax was 0.35 μm. The residual oil amount on the inner surface of the pipe was 3 mg / dm ² , and the residual carbon amount was 0.11 mg / d
m ² .

After the treatment liquid for forming an amorphous ceramic film is applied to the inside of the copper tube of these test materials, it is heated at a predetermined temperature to form an amorphous ceramic film on the inner surface of the copper tube of the test material. did. Hereinafter, a method of forming the amorphous ceramic film will be described. As a treatment liquid, a solution obtained by adding 1 to 20 parts by mass of isopropyl alcohol to 1 part by mass of a stock solution of ceramica G1-50 (manufactured by Nichiita R & D Laboratories) and a stock solution was used. In order to apply these solutions to the test material, a rubber stopper is placed on one end of the copper tube, filled with a processing solution of a predetermined concentration and held for 5 minutes, and then the rubber stopper on one end is removed and the processing solution inside flows out. I let it. Next, when the temperature is 25 ° C and the humidity is 6
In an atmosphere of 0%, the copper tube coated with the treatment liquid on the inner surface was held for 3 minutes so that the tube axis direction was vertical, and then dried for 60 minutes while keeping the tube axis direction horizontal. The film thickness of the amorphous ceramic formed in the tube was adjusted by changing the concentration of the treatment liquid or repeating the process of applying the treatment liquid after drying the treatment liquid or after forming the film a plurality of times.

The dried copper tube was placed in a vacuum electric furnace and evacuated. Then, the inside of the furnace was replaced with nitrogen gas having a purity of 99.99%.
And heated the copper tube to form an amorphous ceramic film on the test material. Similarly, a sample heated and maintained at 250 ° C. in an air atmosphere was formed. The temperature of the copper tube was raised and lowered at a heating rate of 60 ° C./min (from 30 ° C.) and a cooling rate of 30 ° C./min (up to 30 ° C.) at any heating temperature. The test material was 60 minutes, the test material at a heating temperature of 500 ° C. was 10 minutes, and the higher the temperature, the shorter the heating time. In this way, for each of the film forming conditions obtained by combining the concentration of the coating solution to be applied and the heating conditions, 14 test materials each having a film formed were prepared. Two of them were cut in half in parallel to the tube axis direction, and the film thickness, film surface roughness, and film hardness (pencil scratching) of 700 mm at the center in the longitudinal direction at equidistant positions in the longitudinal direction. Hardness) and the thickness of the oxide film formed between the film and the copper tube base. In a copper tube having an amorphous ceramic film formed under the same conditions, these measured values are almost the same in the longitudinal direction of the two copper tubes and the same copper tube. ,
It was found that an almost uniform amorphous ceramic film was obtained over the entire length of the tube.

The remaining twelve copper tubes under the same conditions for forming the amorphous ceramic film were 100 mm at both ends in the longitudinal direction.
Each mm was cut and bent at a predetermined radius of curvature using a pipe bender to form a U-shaped tube having one bent portion at the center in the longitudinal direction. The radius of curvature of the bent portion was changed by a bending jig. A test for evaluating pitting corrosion resistance and erosion resistance was performed using the U-tube thus prepared. In the pitting water running test and the erosion running water test, the case where it was determined that pitting and erosion did not occur, respectively, was evaluated as O, and the case where it was determined that pitting and erosion occurred, respectively, was evaluated as x. Tables 1 and 2 below show the heating temperature at the time of forming the ceramic film and the results of the investigations of the examples and comparative examples.

[0078]

[Table 2]

[0079]

[Table 3]

In the copper tubes with the amorphous ceramic coatings of Examples 1 to 6, the ratio (R / D) of the radius of curvature inside the bent portion to the outer diameter of the tube (R / D), the film thickness of the amorphous ceramic, Pencil scratch hardness of the crystalline ceramic film, surface roughness in the pipe axis direction on the inner surface of the pipe (Ra / Rmax), ratio of the crystal grain diameter d in the pipe thickness direction to the radius of curvature R inside the bend of the bent portion (d / R) is within the preferred range of the present invention, so that the current density at 100 mV polarization exhibiting pitting corrosion resistance is 1/10 that of the copper tube of Comparative Example 13 in which an amorphous ceramics film is not formed.
Thus, the pitting corrosion resistance was extremely excellent. Also, according to a pitting corrosion evaluation test by a running water test for 6 months, in the copper tube of this example, since the amorphous ceramic film on the inner surface of the copper tube remains,
No pitting occurred and no pitting occurred, indicating good pitting resistance. Further, in the copper tube of this example, the amorphous ceramics film on the inner surface of the copper tube was not broken, and no corrosion-reduced portion was found on the inner surface of the copper tube according to the erosion resistance evaluation test by running water test for 6 months. No erosion resistance was exhibited.

In the copper tube of Example 7, the thickness of the amorphous ceramic film was 0.04 μm, which was smaller than the lower limit of the preferable range of the present invention, and the amorphous ceramic film formed in the copper tube was Due to the presence of the thin part, the current density slightly increased, and small pitting and erosion of less than 0.02 mm occurred in the running water test.

In the copper tube of Example 8, since the film thickness of the amorphous ceramics film was 119 μm, which is higher than the upper limit of the preferable range of the present invention, the current density was slightly increased, and the small hole was found by the flowing water test. Eating and erosion occurred. When observing the bent portion of the copper tube of this example, cracks in the amorphous ceramic film and partial peeling from the copper tube were observed. Therefore, the base of the copper tube was exposed at these defective portions.

In the copper tube of Example 9, since the radius of curvature R inside the bend of the bent portion of the copper tube is small and R / D is less than the lower limit of the preferable range of the present invention, the amorphous portion in the bent portion is not used. Due to cracking of the ceramic coating and partial exfoliation from the copper tube, the current density increased slightly and small pitting and erosion occurred.

In the copper tube of Example 10, the amorphous ceramic film was hardened and the hardness exceeded the upper limit of the preferred range of the present invention, so that the amorphous ceramic film was hard and the ductility was reduced. The current density slightly increased due to cracking of the amorphous ceramic film at the bent portion and partial peeling from the copper tube, and small pitting and erosion occurred.

In the copper tube of Example 11, the crystal grain size d of the copper tube was large, and the ratio d / R of the crystal grain size d to the radius of curvature R inside the bend of the bent portion was the upper limit of the preferred range of the present invention. Since the value exceeded the value, a step was formed at the grain boundary at the bent portion, cracking and peeling of the film occurred, the current density increased slightly, and small pitting and erosion occurred.

In the copper tube of Example 12, since heating for forming the amorphous ceramic film was performed in the air, oxygen entered the film during the film forming process, and the copper tube of the present invention was deposited on the substrate on the inner surface of the copper tube. Since an oxide film having a film thickness exceeding the upper limit of the preferred range was formed, the adhesion of the ceramic film to the copper tube substrate was reduced, and cracking and peeling of the film occurred, particularly at the bent portion, and the current density increased slightly. Pitting and erosion occurred.

In the copper tube of Comparative Example 13, since the amorphous ceramic film was not formed on the inner surface of the tube, the current density was highest, and the depth was 0.2 m in the flowing water test.
m or larger pitting and erosion were observed, and the result was the worst pitting and erosion resistance.

[0088] The second embodiment outside diameter 15.88 mm, thickness 0.8mm phosphorus deoxidized copper (J
IS C1100) Thirteen samples having a length of 1000 mm were collected from a smooth tube coil (annealed) and used as test materials. The oxide film thickness on the inner surface of these copper tubes is 50 in terms of Cu ₂ O.
Å, the crystal grain size in the thickness direction was 30 μm. The center line average surface roughness Ra of the inner surface of the copper tube was 0.3 μm, the residual oil amount on the inner surface of the tube was 3 mg / dm ² , and the residual carbon amount was 0.13 mg /
dm ² .

An amorphous ceramics film having a thickness of 0.25 μm was formed on seven of these copper tubes in the same manner as in Example 1. FIG. 2 is a schematic view showing a test material having a ceramic film formed thereon. As shown in FIG. 2, both ends of each test material were cut by 100 mm, and the length was 800 mm.
A copper tube with an amorphous ceramic film was prepared. When one copper tube with an amorphous ceramics film was cut in half in the longitudinal direction and examined, the pencil scratch hardness was 5H, the surface roughness Ra of the film was 0.23 μm, and Rmax. It was 0.33 μm.

The remaining six wires were bent to form bent portions. FIG. 3 and FIG. 4 are schematic diagrams showing the copper pipes subjected to U-shaped bending and L-shaped bending, respectively. As shown in FIG. 3, three of the six copper tubes have a U-shaped bend (R1 / D = 1.89) in which the radius of curvature R1 inside the bend of the bent portion at the center in the longitudinal direction is 30 mm. , D / R1 = 1.0)
Was performed to form a U-shaped bent copper tube 1. As for the other three, as shown in FIG. 4, the radius of curvature R2 inside the bend of the bent portion is 50 mm (R2 / D = 3.15, d / R2 = 0.
6) and the radius of curvature R3 is 20 mm (R3 / D = 1.2
6, d / R3 = 1.5) to form an L-shaped bent copper tube 2.

Next, a U-shaped bent copper tube 1 and an L-shaped bent copper tube 2
Was used one by one to form a joined copper tube 3. FIG. 5 is a schematic view showing a joined copper tube. First, as shown in FIG.
One end of a U-shaped bent copper pipe 1 is expanded using an expansion jig so that an L-shaped bent copper pipe 2 can be inserted, and an L-shaped bent copper pipe 2 to be inserted is inserted. Contact part 4
In, the amorphous ceramics film formed on the inner surface was peeled off using emery paper from the insertion end to a position having a width of 5 mm. Thereafter, the U-shaped bent copper pipe 1 and the L-shaped bent copper pipe 2 were brazed and joined using phosphor copper brazing (BCuP-2), and three sets of joined copper pipes 3 were prepared.

Further, the same U-shaped bending and L-shaped bending as described above using six copper tubes having no amorphous ceramic film formed on the inner surface, and brazing using these copper tubes were performed. Three sets of test materials for comparison were prepared to make Comparative Example 15.

Thereafter, Example 14 and Comparative Example 15 are described.
And 30 kg / cm by He gas ^TwoPressure
Leak test was performed on all test materials.
I confirmed that it would not be born.

Using the brazed copper tubes of these Examples and Comparative Examples, a current density measurement and a water flow test for evaluating pitting corrosion resistance and erosion resistance were performed in the same manner as in Example 1. As a result, in Example 14, the current density was 0.0050 μA / dm ² , and no pitting, erosion, discoloration, and the like were seen at all near the U-shaped and L-shaped bent portions after the running water test, which was favorable. High corrosion resistance.

On the other hand, in Comparative Example 15, the current density was as high as 7.18 μA / dm ² , and pitting, erosion, and discoloration were observed near the U-shaped and L-shaped bent portions after the running water test. Was.

[0096] Third Embodiment outer diameter 9.52 mm, wall thickness 0.5mm phosphorus deoxidized copper (JI
SC1100) Thirteen samples having a length of 1000 mm were collected from a smooth tube coil (annealed) and used as test materials.
The oxide film thickness on the inner surface of these copper tubes is 50 ° in terms of Cu ₂ O,
The crystal grain size in the thickness direction was 25 μm. Further, the center line average surface roughness Ra of the inner surface of the copper pipe Ra = 0.3 μm, Rmax =
0.45 μm, the residual oil amount on the inner surface of the pipe was 3 mg / dm ² , and the residual carbon amount was 0.11 mg / dm ² .

FIG. 6 is a sectional view showing a pipe joint made of phosphorus deoxidized copper. As shown in FIG. 6, the same-diameter socket 5 used for a pipe joint has a groove formed in the center of a copper tube made of phosphor deoxidized copper having the same diameter at both ends, and a copper tube to be joined from the end is inserted. The copper tube and the same diameter socket 5 can be joined by brazing. The same-diameter socket 5 has an oxide film thickness of 50 ° in terms of Cu ₂ O and a crystal grain size in the thickness direction of 35 μm.
m, the center line average surface roughness Ra of the inner surface of the copper tube is 0.25 μm
m, and the maximum surface roughness Rmax was 0.35 μm. Seven sockets 5 of the same diameter were prepared, and an amorphous ceramic film having a thickness of 0.5 μm was formed on the inner surface of each socket 5 of the same diameter.

Then, after forming an amorphous ceramic film having a thickness of 0.35 μm on seven of the test materials by the same method as in Example 1, as shown in FIG. Both ends were cut by 100 mm to prepare a copper tube with an amorphous ceramic film having a length of 800 mm. When one copper tube with an amorphous ceramics film thus prepared was cut in half in the longitudinal direction and inspected, the pencil scratch hardness was 6H, the surface roughness Ra of the film was 0.25 μm, and Rmax. It was 0.37 μm. About three of the remaining six, the radius of curvature R4 inside the bend of the bend is 20 m at the center in the longitudinal direction.
U bending (R4 / D = 2.10, d / R4 =
1.25) to produce a U-shaped bent copper tube 6. The other three
For the book, U-shaped bending (R5 / R5 /
D = 1.58, d / R5 = 1.66) to produce a U-shaped bent copper tube 7.

Next, a joined copper pipe was prepared using one of the prepared U-shaped bent copper pipes 6 and 7 respectively. FIG.
FIG. 2 is a schematic view showing a joined copper tube. As a method of forming the joined copper tube, first, the inner amorphous ceramic film was peeled off from both ends of the same diameter socket 5 to a position of 5 mm using emery paper. Thereafter, as shown in FIG. 7, a U-shaped bent copper tube 6 and a U-shaped bent copper tube 7 having a U-shaped bend having different radii of curvature are inserted into the same-diameter socket 5 and brazed and joined to form a joined copper tube. Were prepared in three sets. This bonded copper tube is referred to as Example 16.

Further, three sets of comparative test materials were prepared by performing U-shaped bending and brazing in the same manner as described above using six copper tubes having no amorphous ceramic film formed on the inner surface. 17 was set. As a result of the leak test for Example 16 and Comparative Example 17, it was confirmed that no leak occurred.

By using the brazed copper tubes of Example 16 and Comparative Example 17, a flow test was conducted in the same manner as in Example 1 to measure current density and to evaluate pitting corrosion resistance and erosion resistance. Was. As a result, in Example 16, the current density was extremely low at 0.0065 μA / dm ² , and the pitting, erosion, discoloration, etc. were observed in the vicinity of the U-shaped bent portion having two types of curvature and the joint portion of the pipe joint after running water tests. Was not observed at all, indicating good corrosion resistance.

On the other hand, in Comparative Example 17, the current density was as high as 6.88 μA / dm ^2, and pitting and erosion and discoloration were observed in the vicinity of the U-shaped bends 6 and 7 after running water tests. Occurrence was observed.

[0103]

As described in detail above, according to the present invention,
Because the amorphous ceramic film is formed on the inner surface of the copper or copper alloy tube, even if a bent portion is formed on the copper or copper alloy tube, from high to low temperatures, even if used for a long time regardless of the water quality It is not corroded and has extremely excellent pitting and erosion resistance, and if it is used, an excellent water / water heater can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of an infrared absorption spectrum of an amorphous ceramic film.

FIG. 2 is a schematic view showing a test material on which a ceramic film is formed.

FIG. 3 is a schematic view showing a U-shaped bent copper pipe 1 subjected to a U-shaped bending process.

FIG. 4 is a schematic diagram showing an L-shaped bent copper pipe 2 subjected to an L-shaped bending process.

FIG. 5 is a schematic view showing a joined copper tube joined by using a U-shaped bent copper tube 1 and an L-shaped bent copper tube 2;

FIG. 6 is a sectional view showing a pipe joint made of phosphorus deoxidized copper.

FIG. 7 is a schematic diagram showing a joined copper pipe using a U-shaped bent copper pipe 6 and a U-shaped bent copper pipe 7.

[Explanation of symbols]

 1, 6, 7; U-shaped bent copper tube 2: L-shaped bent copper tube 3: jointed copper tube 5: same-diameter socket

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akinori Tsuchiya 65, Hirasawa, Hadano City, Kanagawa Prefecture Inside the Hadano Works of Kobe Steel Co., Ltd. (72) Inventor Kozo Saeki 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel, Ltd.Kobe Research Institute

Claims (11)

[Claims] 1. A copper or copper alloy tube having a bent portion, wherein an amorphous ceramic film is formed on an inner surface of the copper or copper alloy tube. . 2. Copper or copper alloy tubes having a bent portion with an amorphous ceramic film formed on the inner surface thereof, or a copper or copper alloy tube and a straight tube having a bent portion with an amorphous ceramic film formed on the inner surface 2. The corrosion-resistant copper or copper alloy having a bent portion according to claim 1, wherein the copper or copper alloy tube is joined to the tube, and the amorphous ceramic film is not formed at the joint. tube. 3. The radius of curvature of the inside of the bend at the inside of the bend is R [mm], and the outside diameter of the copper or copper alloy tube is D [mm].
The corrosion-resistant copper or copper alloy tube having a bent portion according to claim 1 or 2, wherein R / D is 0.5 or more. 4. The method according to claim 1, wherein said amorphous ceramic film has a thickness of 0.1 to 100 μm.
A corrosion-resistant copper or copper alloy tube having a bent portion according to any one of claims 1 to 3. 5. The copper or copper alloy tube according to claim 1, wherein the hardness of the amorphous ceramic film is 3H to 10H as a pencil scratch value. 6. The copper or copper alloy pipe has a center line average surface roughness Ra of 0.5 μm or less and a maximum surface roughness Rmax of 1.0 μm or less in the tube axis direction on the inner surface. Item 6. A corrosion-resistant copper or copper alloy tube having a bent portion according to any one of Items 1 to 5. 7. When the crystal grain size in the thickness direction of the copper or copper alloy tube is d [μm] and the radius of curvature in the bent portion is R [mm], at least d / R ≦ in the bent portion. The corrosion-resistant copper or copper alloy pipe having a bent portion according to any one of claims 1 to 6, wherein 8. An oxide film present between said amorphous ceramic film and said copper or copper alloy tube has a thickness of 0.1 μm.
The corrosion-resistant copper or copper alloy tube having a bent portion according to any one of claims 1 to 7, characterized in that: 9. A method for forming a bent portion on a copper or copper alloy tube by forming a bent portion on the copper or copper alloy tube and forming an amorphous ceramic film on the inner surface of the copper or copper alloy tube. A method for producing a corrosion-resistant copper or copper alloy tube. 10. The bending method according to claim 1, further comprising the steps of: forming an amorphous ceramic film on the inner surface of the copper or copper alloy tube; and forming a bent portion on the copper or copper alloy tube by bending. For producing a corrosion-resistant copper or copper alloy tube having a portion. 11. A corrosion-resistant copper or copper alloy having a bent portion, wherein at least one of the corrosion-resistant copper or copper alloy tubes having the bent portion according to claim 1 is used. Water heater using pipes.