JP3264240B2 - Method for producing copper tube having copper porous layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a copper tube having a copper porous layer formed on its surface. The copper pipe according to the present invention is applied to a pipe for a heat exchanger, a heat pipe, a pipe for hot and cold water supply, and the like.

[0002]

2. Description of the Related Art Conventionally, as a technique for forming a porous layer made of metal on the surface of a metal material, for example, the following techniques are known. Japanese Patent Application Laid-Open No. 60-103187 discloses a method for manufacturing a heat exchanger tube, which comprises forming a coating of a copper-tin-bismuth alloy on the surface of a steel tube. Japanese Patent Application Laid-Open No. S60-251390 discloses a method in which a low melting point solder (joining powder) of about 500 mesh and a material powder composed of copper pieces of 200 mesh or less are put on the inner surface of a copper tube (envelope). A method for manufacturing a heat pipe is disclosed in which these powders are heated and welded while being rotated in a circumferential direction. Japanese Patent Application Laid-Open No. 60-255983 discloses that a magnetic powder coated with a metal having a low melting point is sprinkled on a surface of a metal heat transfer base by using a magnetic field and heated, so that the magnetic powder is transferred to a heat transfer surface. There is disclosed a method for producing a heat exchanger, which is characterized in that the heat exchanger is closely adhered to a heat exchanger. JP-A-61-168
No. 793 discloses a heat transfer tube in which copper powder is sprayed onto the surface of a metal tube by a plasma spraying method to form fine irregularities on the surface, and a method for manufacturing the same. JP-A-62-2
No. 206382 discloses a heat pipe in which a dendritic or granular porous layer is formed on the inner surface of a metal tube such as a copper tube by electroplating. JP-A-2-12
No. 9488 discloses a superficially porous tube in which a number of fine open surfaces are formed by dezincing the inner and outer surfaces of a copper-zinc alloy tube. JP-A-2-1758
No. 81 discloses that a mixed layer of a low melting point metal powder (Sn powder) and a high melting point metal powder (Cu powder) is formed on the inner surface of a metal tube.
There is disclosed a method of manufacturing an inner porous tube which heats this to form micropores. JP-A-5-214504 discloses a method for manufacturing a heat transfer tube in which a metal wire is wound around a material tube while spraying metal powder on the surface of the material tube to form a porous sprayed layer, and the metal wire is removed after the sprayed layer is formed. A method is disclosed.

[0003]

Among the prior arts described above, a method of forming a porous layer made of copper on the surface of a copper tube by using a low-melting metal such as solder or Sn comprises a copper tube,
Since the porous layer made of copper is joined to the porous layer made of copper via a low-melting metal such as solder or Sn, heat conduction becomes poor at the low-melting metal portion, and as a result, the heat conduction loss between the copper tube and the porous layer is reduced. There was a problem of becoming larger. Further, when low melting point solder or the like is used, there is a problem that heat resistance and chemical resistance are deteriorated. In addition, a thermal spraying method such as plasma spraying, or a method of providing a copper porous layer or fine irregularities by electroplating on the surface of a copper tube has a problem that production is troublesome.

The present invention has a copper porous layer on the surface of a copper tube,
It is an object of the present invention to provide a method for efficiently producing a copper tube having excellent heat exchange efficiency.

[0005]

According to the present invention, there is provided a method for producing a copper tube having a copper porous layer, comprising the steps of (i) temporarily bonding copper powder to the surface of the copper tube with an organic binder to produce a pre-treated tube. ,
(Ii) The pretreatment tube is heated and held under an oxidizing atmosphere to form an oxidation treatment tube having a structure in which the copper powder, the surface of the copper tube, and the copper powder are cross-linked by an oxide generated on each surface. (Iii) heating the oxidized tube under a reducing atmosphere to form a copper porous layer on the surface of the copper tube in which copper powder is bonded to the surface of the copper tube or another copper powder by metal bonding. And the step of performing Further, another method for producing a copper tube having a copper porous layer according to the present invention comprises: (a) a step of temporarily joining copper powder to the surface of a copper plate with an organic binder to produce a pre-treated plate; A step of heating and holding the plate under an oxidizing atmosphere to form an oxidized plate having a structure in which the copper powder, the copper plate surface, and the copper powder are cross-linked by an oxide generated on each surface; Heating the oxidized plate under a reducing atmosphere to form a copper porous layer in which copper powder is bonded to the copper tube surface or another copper powder by metal bonding on the copper plate surface; The method is characterized in that the method includes a step of performing a rounding process on a copper plate having a porous layer formed thereon to obtain a copper tube having a copper porous layer.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, copper powder is temporarily joined to the surface of a copper tube with an organic binder, and the surfaces of the copper tube and the copper powder are once oxidized. As a result, a structure in which the copper tube and the copper powder and the copper powder and the copper powder are cross-linked (bridged) with the oxide is obtained. Thereafter, the oxidation treatment tube is heated in a reducing atmosphere. Thereby, the surface of the copper tube and the copper powder is reduced, and the oxide bond between the copper tube and the copper powder and between the copper powder and the copper powder becomes a metal bond.
At least one copper porous layer is formed on the surface of the copper tube. According to this method, a copper porous layer having good heat conductivity can be easily formed on the outer periphery of the copper tube, and the copper porous layer can also be easily formed on the inner peripheral surface of a relatively short copper tube. In another embodiment of the present invention, copper powder is temporarily joined to the surface of the copper plate with an organic binder, and the surfaces of the copper plate and the copper powder are once oxidized. As a result, a structure in which the copper plate and the copper powder and the copper powder and the copper powder are cross-linked (bridged) with the oxide is obtained. Thereafter, the oxidized plate is heated in a reducing atmosphere. As a result, the surfaces of the copper plate and the copper powder are reduced, and an oxide bond between the copper plate and the copper powder and between the copper powder and the copper powder becomes a metal bond, and at least one copper porous layer is formed on the surface of the copper plate. You. Further, the copper plate having the copper porous layer formed thereon is rounded to obtain a copper tube having the copper porous layer. By thus forming a copper tube by rolling a copper plate having a copper porous layer formed on at least one surface, it is possible to easily form a porous layer on the inner surface of a long copper tube, which was conventionally difficult to form. Will be able to In addition, a copper tube having a predetermined pattern of a copper porous layer having a large number of parallel straight lines, corrugations, etc. is formed by forming a copper porous layer of a predetermined pattern in a plate shape and rolling it to form a copper tube. Can be easily produced. As described above, the copper tube having the copper porous layer of a predetermined pattern on the outer peripheral surface or the inner peripheral surface improves the flow of fluid flowing inside or outside the tube or generates turbulent flow to improve heat exchange efficiency. It is possible to do.

[0007] Coarse copper powder having a particle size of 0.1 mm or more does not easily sinter on the surface of the copper plate even when simply heated in an inert atmosphere or a reducing atmosphere. Therefore, in the present invention, copper powder is attached to the surface of the copper plate, and the copper powder is sintered (sintered) to the surface of the copper plate by two-stage sintering of oxidation and reduction. If all the copper is oxidized in the oxidation step, the strength of the copper plate itself is reduced, so only the surfaces of the copper plate and the copper powder are oxidized. Further, once the temperature is lowered in a state of being oxidized at a high temperature, the copper powder and the surface oxide are peeled off from the copper plate surface due to the difference in thermal expansion coefficient between Cu and Cu oxide. Therefore, in the present invention, it is desirable that after oxidation, reduction is performed while maintaining the temperature at a high temperature.

In the present invention, the material copper tube or copper plate is
Pure copper (Cu), Cu-P alloy (phosphor bronze), Cu-Be alloy (beryllium bronze), Cu-Sn alloy (bronze), Cu-
An Al alloy, a Cu-Si alloy, a Cu-Ni alloy, or an alloy mainly containing copper to which two or more elements are added can be used, and pure copper is particularly desirable. The copper tube or copper plate to be used only needs to have at least the surface portion formed of copper or a copper alloy.In addition to the above-described integrated member made of copper or a copper alloy, the surface of another metal plate such as a steel plate is made of copper. A coated material or a copper-steel clad material may be used. In addition to the circular tube, the copper tube may be an elliptical tube or a square tube having a triangular, square, rhombic, or polygonal cross section. As the shape of the copper plate, a thin plate, a thick plate, a foil, a long tape, or the like is used.

An example of manufacturing a copper tube having a copper porous layer by the method of the present invention using the copper tube will be described with reference to FIGS. In the present invention, first, copper powder 3 is temporarily bonded to one of the outer peripheral surface and the inner peripheral surface of copper tube 1 or both inner and outer surfaces (hereinafter, referred to as the surface of copper tube 1) with organic binder 2, as shown in FIG. Step (i) of preparing the pretreatment tube 11 is performed. The organic binder 2 is preferably a material which is easily eliminated in the subsequent step (b) of heating and maintaining the pretreatment tube 11 under an oxidizing atmosphere, and in which traces of excess ash and carbon do not remain. Examples include glycerin, oils (mineral oils, animal and vegetable oils and fats), and organic adhesives such as acrylic resin and cellulose resin. For convenience, a commercially available spray-type acrylic resin adhesive may be used to spray-coat the desired portion of the copper tube 1.

Further, as the copper powder 3 used in the present invention, pure copper and a copper alloy mainly composed of copper can be used as in the case of the copper tube 1, and a copper powder made of pure copper is particularly preferable.
In addition, the particle size of the copper powder can achieve the functions required for the copper porous layer to be produced, that is, an improvement in heat exchange efficiency and an increase in surface area, and the formed copper porous layer has sufficient mechanical strength and The average particle diameter is usually 0.1 to 3 mm, preferably about 0.2 to 2 mm. Further, in order to arrange the copper powder 3 densely on the surface of the copper tube 1, it is desirable to make the particle diameter of the copper powder 3 as uniform as possible. The method for dispersing the copper powder 3 on the surface of the copper tube 1 is not limited. For example, a method of dropping the copper powder 3 little by little on the outer peripheral surface of the copper tube 1 or a method of putting a predetermined amount of copper powder into the copper tube 1, May be used to fix the copper powder 3 on the inner peripheral surface of the copper tube 1 while moving the copper powder. Alternatively, an organic binder may be applied again to the copper powder 3 temporarily bonded to the copper tube 1 and the copper powder 3 may be scattered to form a multilayer structure.

Next, the pretreatment tube 11 in which the copper powder 3 is temporarily bonded to the surface of the copper tube 1 is placed in an atmosphere heating furnace or the like, and heated and maintained at 400 to 700 ° C. in an oxidizing atmosphere, preferably in air. As shown in FIG. 2, the copper powder 3 and the surface of the copper tube 1 and the copper powder 3
The step (ii) of forming an oxidation treatment tube 12 having a structure in which the surfaces are crosslinked by the oxide 4 generated on each surface is performed. The heating temperature in this oxidizing atmosphere is 400 ° C.
If it is less than the above, the amount of oxides generated on the surface of the copper powder 3 and the surface of the copper tube 1 is reduced, and the bonding strength between the copper tube 1 and the copper powder 3 is weakened. On the other hand, when the heating temperature exceeds 700 ° C., the copper tube 1 made of copper or a copper alloy is softened and may be deformed or its strength may be reduced. The time for heating and holding the pretreatment tube 11 under the oxidizing atmosphere is not particularly limited as long as a structure in which the surface of the copper tube 1 and the copper powder 3 are sufficiently bonded to each other by the crosslinked structure of the oxide is obtained as described above. Is about 10 minutes to 3 hours,
Preferably, it is about 15 minutes to 1 hour. As the oxidizing gas used in the step (ii), in addition to the above air, pure oxygen gas, oxygen gas diluted with nitrogen gas or carbon dioxide gas, nitrous oxide gas, or the like can be used. When the copper porous layer 5 is formed on the outer peripheral surface of the copper tube 1, if the outer peripheral surface is oxidized while purging by flowing an inert gas such as nitrogen gas into the tube, the oxidation of the inner peripheral surface of the tube is reduced. Can be prevented.

Next, the surroundings of the oxidation treatment tube 12 are heated and held in a reducing atmosphere to form a copper porous layer 5 in which the copper powder 3 is fixed to the surface of the copper tube 1 and other copper powder 3 by metal bonding. ,
The step (iii) of forming the copper tube 13 shown in FIGS. 3 and 4 is performed. Here, after a heating step in an oxidizing atmosphere, if a reducing gas such as a hydrogen gas is immediately introduced into an atmosphere heating furnace containing the oxidation treatment tube 12, combustion may occur. In order to prevent this, after the above (ii) step, while maintaining the temperature of the oxidation treatment tube 12 or shifting to the treatment temperature of the (iii) step, the surroundings of the oxidation treatment tube 12 are replaced with an inert gas atmosphere. After that, the atmosphere is replaced with a reducing atmosphere,
i) It is desirable to carry out the process. By changing the oxidizing atmosphere to the reducing atmosphere without changing the temperature of the copper tube 1, it is possible to prevent the copper oxide 4 and the copper powder 3 from being separated due to a difference in thermal expansion coefficient between copper and copper oxide. Can be. As the inert gas used here, nitrogen gas, argon gas, helium gas or the like is used, and preferably, nitrogen gas is used. In addition, as a reducing gas for forming a reducing atmosphere, a carbon monoxide-containing gas such as hydrogen gas, hydrogen gas diluted with nitrogen gas, carbon monoxide gas, butane decomposition gas, water gas, and generation gas is used. Hydrogen gas and hydrogen gas diluted with nitrogen gas are particularly suitable.

The heating temperature when heating the oxidation treatment tube 12 in a reducing atmosphere is 300 to 700 ° C., preferably 40 to 700 ° C.
The temperature is set to about 0 to 600 ° C. When the heating temperature is lower than 300 ° C., the reduction is not sufficient, and the copper oxide remains,
(Ii) The temperature difference from the process is large, and the copper powder 3 and oxides are easily peeled off. When the heating temperature exceeds 700 ° C., the copper tube 1 made of copper or a copper alloy is softened, and may be deformed or have reduced strength. Oxidation tube 1 under reducing atmosphere
The time for heating and holding the copper powder 3 is as described above.
Although there is no particular limitation as long as the copper porous layer 5 fixed to the surface and other copper powder 3 by metal bonding can be formed, it is usually 10
Minutes to 3 hours, preferably 15 minutes to 1 hour.

By sequentially performing the above steps (i) to (iii), a copper tube having a copper porous layer 5 formed on the outer peripheral surface and the inner peripheral surface of the copper tube 1 as shown in FIGS. 13 are produced. The copper pipe 13 having the copper porous layer is applied to a pipe for a heat exchanger, a heat pipe, a pipe for hot water supply, and the like. According to this method, the heat conduction between the copper porous layer and the copper tube can be improved as compared with the case where the porous layer is formed on the surface of the base via the low melting point metal. Further, the copper tube 13 having the copper porous layer can be manufactured with simple manufacturing equipment in a short time.

An example of manufacturing a copper tube having a copper porous layer by a method of the present invention using a copper plate will be described with reference to the drawings. In this method, first, the copper tube 1 described above is attached to one or both surfaces of the copper plate 1 (hereinafter referred to as a copper plate surface).
In the same manner as the method using
Are temporarily joined to form a pretreatment plate 11 shown in FIG. 1 (a).
Perform the process. Next, this pretreatment plate 11 is placed in an atmosphere heating furnace or the like, and is placed in an oxidizing atmosphere, preferably in air, for 400 to 400 hours.
Heating and holding at 700 ° C., as shown in FIG. 2, the oxidized plate 12 having a structure in which the copper powder 3 and the surface of the copper plate 1 and the copper powder 3 are cross-linked by the oxide 4 generated on each surface. The step of forming (b) is performed. Next, the periphery of the oxidized plate is heated and held in a reducing atmosphere, and as shown in FIG. 3, the copper porous layer 5 in which the copper powder 3 is fixed to the copper plate surface and other copper powder 3 by metal bonding is applied. The step (c) of forming and forming a copper plate having the copper porous layer 5 is performed.

Next, the copper plate having the copper porous layer 5 is rounded to perform a step (d) of manufacturing a copper tube 14 shown in FIG. This rounding process may use a well-known technique used for manufacturing a copper pipe or a steel pipe, for example. Also, the seam may be welded to form a complete tube or may not be welded.

By sequentially performing each of the steps (a) to (d), the copper powder 3 is bonded to at least one of the outer peripheral surface and the inner peripheral surface by metal bonding to the surface of the copper plate 1 and the other copper powder 3. A copper tube 14 having the adhered copper porous layer 5 is obtained. This copper pipe 14 is applied to a pipe for a heat exchanger, a heat pipe, a pipe for hot and cold water supply, and the like. According to this method, the heat conduction between the copper porous layer and the copper tube can be improved as compared with the case where the porous layer is formed on the surface of the base via the low melting point metal. Further, a copper porous layer which is firmly bonded to the surface of the copper plate via copper is formed, and this copper plate is rolled into a copper tube, so that the copper tube having the copper porous layer can be manufactured with simple manufacturing equipment in a short time. Can be manufactured. Therefore, according to the present invention,
A copper tube having excellent heat exchange efficiency can be manufactured efficiently. In addition, since the copper tube is manufactured by rolling the copper plate 13 having the copper porous layer 5 formed thereon, the copper porous layer can be easily formed on the inner surface of the long tube, which has been difficult to form by the conventional method.

FIGS. 6 to 8 show various shapes of the copper porous layer 5 on the inner peripheral surface or the outer peripheral surface to form a copper tube having the copper porous layer 5 of various patterns by performing rounding.
FIG. 6 illustrates the copper plate 13 on which the copper plate 13 is formed.
Shows a case where a large number of linear copper porous layers 5 are formed along the longitudinal direction of FIG. By forming the copper porous layer 5 in this manner, when the copper plate 13 is rolled into a copper tube, the resistance of the fluid flowing along the tube can be reduced. FIG.
Shows a case where the copper porous layer 5 is formed in an oblique strip shape, and when the copper plate 13 is rolled into a tube, the spiral copper porous layer 5 is formed on the inner or outer peripheral surface of the tube. . FIG.
Shows a case where the copper porous layer 5 is formed in a large number of waves.
When the copper plate 13 is rolled into a tube, they generate a turbulent flow in the fluid flowing along the copper tube, so that the heat exchange efficiency can be further improved. The pattern of the copper porous layer 5 formed on the copper plate 13 is not limited to each of the above examples, but may be a curved shape.
It may be formed in an S-shaped pattern, a W-shaped pattern, or may be formed in a pattern such as various symbols such as a dot shape, a single rod shape, a <character shape, or a wavy shape.

It is also possible to continuously perform the above steps (a) to (d) to continuously produce a long copper tube 14. In that case, using a long copper plate, an organic binder coating device, a copper powder spraying device, a furnace capable of heating under an oxidizing atmosphere and a reducing atmosphere, and a welded pipe for rounding and seam welding It is desirable to arrange the devices in order and move the long copper plate at a constant speed while continuously performing the steps (a) to (d). According to this method, a long copper tube having a copper porous layer on the inner surface, which has conventionally been difficult to form, can be easily manufactured.

[0020]

Embodiments of the present invention will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the description of the embodiments. (Example 1) A copper tube (substrate) made of pure copper having an outer diameter of 11 mmφ and an inner diameter of 9 mmφ, a pure copper powder having an average particle diameter of 0.6 mm, and an acrylic resin-containing spray (organic binder) were prepared. Acrylic resin was spray-applied around the copper tube and then sprinkled with pure copper powder. As a result, pure copper powder uniformly adhered to only one or two layers. A copper tube (pre-treated material) having copper powder adhered to the outer peripheral surface is placed in a tubular electric furnace, heated and maintained in air at 600 ° C. for 0.5 hour, and then, while maintaining the temperature as it is, once inside the furnace tube. After replacing with an inert gas (N ₂ ), the gas was replaced with a reducing gas (H ₂ ) and further maintained at 700 ° C. for 0.5 hour. As a result, a copper tube having a copper porous layer formed by baking pure copper powder on the outer peripheral surface of the copper tube was obtained.

Example 2 A thin copper plate made of pure copper having a width of 50 mm, a pure copper powder having an average particle diameter of 0.8 mm, and a commercially available acrylic resin-containing spray (organic binder) were prepared. After spray coating an acrylic resin on the surface of the copper plate, the pure copper powder was sprinkled on the copper plate to obtain a pre-treated plate. Then, the pre-treated plate was placed in an electric furnace, heated and maintained in air at a temperature of 500 ° C. for 30 minutes, and then the atmosphere in the furnace was replaced with an N ₂ atmosphere while the temperature in the electric furnace was kept constant. _The atmosphere was replaced with _two atmospheres, and heated and maintained at a temperature of 500 ° C. for 30 minutes. After heating, it is allowed to cool to room temperature in an H ₂ atmosphere, the copper plate is taken out, the copper porous layer is rolled toward the outer peripheral surface by roll processing, and the seam is joined by arc welding,
A copper tube was made. As a result, a copper tube in which one to three layers of pure copper powder were baked on the outer peripheral surface to form a copper porous layer was obtained.

[0022]

The method for producing a copper tube according to the present invention comprises the steps of temporarily bonding copper powder to the surface of a copper tube with an organic binder, heating and holding the powder in an oxidizing atmosphere, and subsequently in a reducing atmosphere. Since the copper porous layer is fixed to the copper tube by metal bonding by performing the step of heating and holding, the copper tube having the copper porous layer is manufactured in a short time with simple manufacturing equipment. be able to. In addition, a step of temporarily bonding copper powder to the surface of the copper plate with an organic binder and heating and holding the same in an oxidizing atmosphere, and subsequently performing a step of heating and holding the same in a reducing atmosphere, is performed so that the copper porous layer is bonded to the metal. Forming a copper porous layer adhered to the copper plate, and then rounding the copper plate to produce a copper tube having a copper porous layer, so that a porous layer is formed on the surface of the base via a low melting point metal. As compared with the above, the heat conduction between the copper porous layer and the copper tube can be improved. Further, a copper porous layer which is firmly bonded to the surface of the copper plate via copper is formed, and this copper plate is rolled into a copper tube, so that the copper tube having the copper porous layer can be manufactured with simple manufacturing equipment in a short time. Can be manufactured. Therefore, according to the present invention,
A copper tube having excellent heat exchange efficiency can be manufactured efficiently. Further, since the copper tube on which the copper porous layer is formed is rolled to manufacture the copper tube, the copper porous layer can be easily formed also on the inner surface of the long tube, which is difficult to form by the conventional method. Furthermore, since a copper tube is manufactured by rolling the copper plate on which the copper porous layer is formed, a large number of copper porous layers having a predetermined pattern such as a parallel linear shape and a wavy shape are formed on the surface of the copper plate, and the outer peripheral surface or the inner peripheral surface is formed. A copper tube having a copper porous layer of a predetermined pattern on its surface can be easily manufactured. A copper tube having such a copper porous layer can improve the flow of fluid flowing inside or outside the tube, or generate turbulence to improve the heat exchange efficiency.

[Brief description of the drawings]

FIG. 1 illustrates an example of a method of manufacturing a copper tube having a copper porous layer according to the present invention, in which step (i) (or step (a)) of temporarily joining copper powder to the surface of a copper tube (or copper plate); FIG.

FIG. 2 is an enlarged sectional view showing a step (ii) (or a step (b)) of forming an oxidation-treated tube (or an oxidation-treated plate).

FIG. 3 is an enlarged sectional view showing a step (iii) (or a step (c)) of forming a copper tube having a copper porous layer.

FIG. 4 is a perspective view showing a copper tube having a copper porous layer manufactured through steps (i) to (iii).

FIG. 5 is an enlarged sectional view showing a step (d) of performing rounding on a copper plate having a copper porous layer.

FIG. 6 is a plan view showing an example of a pattern of a copper porous layer formed on a copper plate surface.

FIG. 7 is a plan view showing another pattern.

FIG. 8 is a plan view showing still another pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper pipe (or copper plate) 2 Organic binder 3 Copper powder 4 Oxide 5 Copper porous layer 11 Pretreatment plate (or pretreatment tube) 12 Oxidation treatment plate (or oxidation treatment tube) 13 Copper tube having a copper porous layer (Or copper plate) 14 Copper tube with copper porous layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 24/08 F28F 1/12 B21D 53/06 B22F 1/02

Claims (2)

(57) [Claims] (I) a step of temporarily joining copper powder to the surface of a copper tube with an organic binder to produce a pretreatment tube; and (ii) heating and holding the pretreatment tube in an oxidizing atmosphere, A step of forming an oxidized tube having a structure in which the powder, the copper tube surface, and the copper powder are cross-linked by an oxide generated on each surface; (iii) heating and holding the oxidized tube in a reducing atmosphere Forming a copper porous layer on the surface of the copper tube, in which copper powder is bonded to the surface of the copper tube or another copper powder by metal bonding;
A method for producing a copper tube having a copper porous layer, comprising the steps of: 2. (a) a step of temporarily bonding copper powder to the surface of a copper plate with an organic binder to produce a pre-treated plate; (b) heating and holding the pre-treated plate in an oxidizing atmosphere; Forming an oxidized plate having a structure in which the surface of the copper plate and the copper powder are crosslinked by an oxide generated on each surface; (c) heating and holding the oxidized plate under a reducing atmosphere;
A step of forming a copper porous layer in which copper powder is bonded to the surface of the copper plate or another copper powder by metal bonding on the surface of the copper plate, and (d) rounding the copper plate on which the copper porous layer is formed to form copper. A method for producing a copper tube having a copper porous layer, comprising the steps of obtaining a copper tube having a porous layer.