JPH06330265A - Production of copper tube for cold water type pitting corrosion resistance - Google Patents

Abstract

PURPOSE:To produce a copper tube for cold water type pitting corrosion resistance free from carbonaceous films on the inside, at the time of annealing a soft or semihard phosphorus deoxidized copper tube for piping by substituting the inside of the copper tube by gaseous hydrogen having high purity and executing heating and annealing in a nonoxidizing atmosphere. CONSTITUTION:At the time of subjecting a soft or semihard phosphorus deoxidized copper tube used as a copper tube for feeding water or hot water used in buildings, flat and condominia and general housing, lubricating oil used in the reduction working stage of the copper tube ununiformly remains on the inside face of the copper the as a carbonaceous film by heating at the time of the annealing to cause the pitting of the copper tube. For preventing the same, at the time of subjecting the copper tube to temper-annealing, the inside of the copper tube is substituted by gaseous hydrogen having high purity of >=99%, and both edges of the copper tube are sealed. Or, in the case the shape of the copper tube 15 formed of a coiled one, the inside of the copper tube 15 substituted by high purity hydrogen, and heating and annealing are executed in a nonoxidizing or reducing atmosphere such as gaseous N2, or DX without sealing both edges. The change of lubricating oil on the inside face of the copper tube into free carbon is prevented, and the generation of cold water type pitting corrosion in the copper tube can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cold water resistant copper pipe for pitting corrosion, more specifically, water supply for construction of buildings, condominiums, general houses, hot water supply pipes, heat transfer pipes for water heaters, and hot and cold water. Conditioning annealing treatment to reduce the formation of carbonaceous film due to free carbon remaining on the inner surface of pipes in the manufacturing process of soft or semi-hard phosphorus deoxidized copper pipes applied to air conditioning equipment pipes and heat transfer pipes And a method for producing a copper pipe for cold water resistant pitting corrosion.

[0002]

2. Description of the Related Art In the production of soft or semi-rigid phosphorous deoxidized copper pipes for piping, the lubricating oil used in the drawing process of copper pipes remains on the inner surface of the pipes, and the residual lubricating oil is subsequently subjected to tempering. It changes into a carbonaceous film by the annealing treatment and remains unevenly in the tube.

In Europe and the United States where hard water is used, water supply has been
I (1) for phosphorus deoxidized copper pipes used as hot water supply pipes
Occurrence of type pitting corrosion has been experienced, but it is presumed that this type I (1) type pitting corrosion is caused by the carbonaceous film remaining in the copper pipe, preventing the formation of the carbonaceous film, Alternatively, in order to remove the residual carbonaceous film, a method of mechanically removing the carbonaceous film by sandblasting (BS standard 2871),
After the normal annealing process, the inner surface of the copper pipe is cleaned and degreased with an organic solvent, and annealed while passing an oxidizing mixed gas through the pipe to prevent the carbonaceous film from remaining in the pipe (GB 2,041,483
No.) is proposed.

In Japan, since the quality of water used is soft water,
Up to now, we have seen phosphorous deoxidized copper pipes for water supply and hot water supply in Europe and the United States.
Almost no (1) type pitting corrosion was experienced, and the prevention and removal of the carbonaceous film remaining on the inner surface of the copper pipe was out of the manufacturing control range. However, recently, cold water type pitting corrosion, which has been experienced in the use of soft water as groundwater, is similar to I (1) type pitting in its corrosion form and corrosion products. As in the above case, it has been clarified that eliminating the residual carbonaceous film in the copper pipe is a measure for preventing cold water type pitting corrosion.

Usually, in the production of phosphorous deoxidized copper pipes, from the viewpoint of the commercial value in terms of appearance, in order to prevent the oxidative discoloration of the inside and outside faces of the copper pipes, the inside and outside faces of the pipes are in a non-oxidizing gas atmosphere such as nitrogen gas or DX gas Alternatively, annealing treatment is performed in a reducing gas atmosphere, but this treatment cannot remove the carbonaceous film remaining in the tube.

In the mechanical removal method such as sand blasting proposed in Europe and America, fine particles such as alumina are removed at high speed,
Large-scale equipment for injecting into the pipe at high pressure is required, and a large amount of crushed powder of fine particles is generated during the work, and there is a possibility that it becomes a spray state and harms the environment. Further, the phosphorous deoxidized copper pipe is often handled in a coil shape in the manufacturing process, but this method has a drawback that it cannot be applied to the treatment of the coiled copper pipe. After cleaning the inside of the pipe, the method of annealing by passing an oxidizing gas through the pipe usually requires annealing, pretreatment of cleaning with an organic solvent, which increases the number of work steps and increases the manufacturing cost. , Because it is necessary to treat the organic solvent after use as an environmental measure,
The processing cost increases and the manufacturing cost increases.

[0007]

DISCLOSURE OF THE INVENTION The present invention is used as a copper pipe for piping for water supply, hot water supply, etc., and is formed in a soft or semi-hard phosphorus deoxidized copper pipe for performing annealing treatment for tempering. It was made as a result of earnest research on a manufacturing method for eliminating a carbonaceous film, and its purpose is to solve the problems in the above-mentioned conventional removal method, and to manufacture phosphorus deoxidized copper pipes for piping. A copper pipe for cold water resistant pitting corrosion that can remove the carbonaceous film generated in the pipe without increasing the cost and without environmental problems and can also be applied to the treatment of coiled copper pipes by performing a new temper annealing treatment. It is to provide a manufacturing method of.

[0008]

In order to achieve the above object, a method for producing a cold water resistant pitting copper pipe according to the present invention is a soft or semi-rigid phosphorus deoxidation for pipes which is subjected to annealing treatment for tempering. In the method of manufacturing a copper pipe, after replacing the inside of the drawn copper pipe with hydrogen gas, annealing treatment in a non-oxidizing or reducing atmosphere is performed to reduce the formation of carbonaceous film on the inner surface of the copper pipe. The basic characteristic of hydrogen gas is 99% purity.
The second characteristic of the configuration is that it is the above hydrogen gas,
After replacing the inside of the copper pipe with hydrogen gas, seal both ends of the copper pipe and anneal in a non-oxidizing or reducing atmosphere.After replacing the inside of the copper pipe with hydrogen gas, seal both ends of the copper pipe. The third and fourth structural features are to perform the annealing treatment without performing the annealing.

The present invention is applied to a soft or semi-hard phosphorous deoxidized copper pipe which is subjected to softening treatment by annealing after drawing.
When a copper pipe is drawn, it is unavoidable that the lubricating oil containing the higher hydrocarbons used in the drawing process remains in the pipe, and in the subsequent annealing treatment, the higher hydrocarbons become aromatic due to thermal decomposition reaction. Changes to hydrocarbons and lower hydrocarbons. In a normal annealing atmosphere, during the annealing treatment, the aromatic hydrocarbons further pass through tar and change into carbon, and this carbon remains in a copper pipe in a nonuniform manner.

The present invention reduces the formation of a carbonaceous film on the inner surface of a copper tube by drawing a copper tube, replacing the atmosphere in the tube with hydrogen gas, and then annealing in a non-oxidizing or reducing atmosphere. To do. The hydrogen gas prevents the higher hydrocarbons contained in the drawing lubricating oil from changing to aromatic hydrocarbons that cause the generation of free carbon. When the inside of the copper pipe is replaced with hydrogen gas, there is a risk of explosion due to hydrogen gas during the annealing process, so the atmosphere in the furnace during the annealing process is a non-oxidizing or reducing atmosphere. Nitrogen gas or DX gas is used to form the atmosphere in the furnace.
The use of these gases also prevents the outer surface of the treated copper tube from being oxidized and improves the quality value in appearance.

The hydrogen gas used is preferably highly pure, and it is preferable to use one having a purity of 99% or more. The use of general industrial-grade hydrogen having a purity of 99% or more can sufficiently obtain the effect of reducing the carbonaceous film formation without significantly increasing the treatment cost. In the present invention, after replacing the inside of the pipe with hydrogen gas, in the case of a straight pipe, it is preferable to seal and anneal both ends of the pipe, but in the case of a coil, seal both ends of the pipe. The atmosphere in the tube is maintained even without annealing, and a sufficient carbonaceous film formation reducing effect can be obtained.

[0012]

According to the present invention, which has the above-mentioned constitution, in the production of the phosphorus-deoxidized copper pipe for pipe which is subjected to the temper annealing after the drawing process, the inside of the drawn copper pipe is replaced with hydrogen gas and then the annealing process is performed. Since it is carried out, the hydrogen concentration in the pipe is high, and therefore, the aromatic hydrocarbons produced by thermal decomposition during annealing from the higher hydrocarbons contained in the lubricating oil are mostly converted to lower hydrocarbons by the hydrogenation reaction, It suppresses the generation of free carbon that causes the formation of carbonaceous film, significantly reduces the formation of carbonaceous film, and prevents the occurrence of cold water resistant pitting corrosion.

[0013]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Example 1 A phosphorus deoxidized copper pipe (JIS H3300 C1220) was used with a lubricating oil (lubricating oil A) having a hydrocarbon polymer as a main component and a kinematic viscosity of 500 cSt (40 ° C.) and a residual carbon content of 0.01%. It was drawn and made into a tube with an outer diameter of 15.88 mm, a wall thickness of 0.71 mm, and a length of 2,000 mm.
The inside of this phosphorous deoxidized copper pipe is for general industrial use (purity 99.99%
After substituting the above hydrogen gas with the hydrogen gas, both ends of the tube were mechanically sealed using Swagelok, and annealed at 600 ° C. for 30 minutes in a nitrogen gas atmosphere.

After the annealing treatment, the amount of carbonaceous film remaining in the tube was measured by the following method to determine the amount of free carbon. (1) Fill the tube with 1-1-1 trichloroethane to remove residual oil. (2) After drying the inside of the tube, nitric acid (1 + 1) is injected, and the remaining carbonaceous film is removed by dissolving the entire surface inside the tube, and dissolved in a nitric acid solution. (3) The nitric acid solution in which the carbonaceous film is dissolved is suction filtered using a glass filter paper that has been preheated, and the carbonaceous film is collected on the filter paper. (4) The collected carbonaceous film is burned together with a filter paper in an oxygen stream, and the generated carbon gas is quantified by a coulometric titration method,
Find free carbon. Table 1 shows the measurement results of the amount of free carbon remaining in the tube.

Comparative Example 1 A phosphorus deoxidized copper tube having the same material and dimensions as drawn by the same conditions as in Example 1 was replaced with air and 99.9% nitrogen gas, and then annealed under the same conditions as in Example 1. Then, the results of measuring the amount of free carbon in the same manner as in Example 1 are shown in Table 1.

[0016]

[Table 1]

As shown in Table 1, the phosphorus deoxidized copper tube treated according to the present invention has a significantly reduced residual free carbon amount in the tube, and no oxidative discoloration on the inner surface of the tube was observed.
The appearance quality was also excellent. On the other hand, the copper tube according to the comparative example had a large amount of free carbon, and when air was used as the replacement gas, oxidative discoloration was also observed in the tube.

Example 2 A phosphorus deoxidized copper pipe (JIS H3300 C1220) was used, and the lubricating oil A used in Example 1 and a kinematic viscosity of which the main component was a hydrocarbon polymer were 150 cSt (40 ° C.) and residual carbon. Min. 0.01% or less of lubricating oil (lubricant B)
22.22mm, 0.81mm thick, 100m long coil shape. The inside of this coiled copper tube is for general industrial use (purity 99.9
After replacement with hydrogen gas (9% or more), the tube was annealed at 600 ° C. for 30 minutes in a DX gas atmosphere without sealing both ends.

After the annealing treatment, a sample for analysis having a length of 2 m was collected from both ends and the center of each coiled copper tube, and the amount of residual carbonaceous film in the tube was measured by the method shown in Example 1. Was determined by the amount of free carbon. The results are shown in Table 2.

Comparative Example 2 After replacing the inside of a phosphorus-deoxidized copper pipe of the same material and the same size, which was drawn by the same conditions as in Example 2, with N ₂ + 5% H ₂ gas,
The same annealing treatment as in Example 2 was performed. After annealing, the amount of free carbon inside each coiled copper tube was measured by the same method as in Example 2. The measurement results are shown in Table 2.

[0021]

[Table 2]

As shown in Table 2, the free carbon content of the copper tube treated according to the present invention is reduced to 1/2 to 1/4 of the free carbon content of the copper tube according to the comparative example. No oxidative discoloration was observed.

Example 3 A phosphorus deoxidized copper pipe (JIS H3300 C1220) was subjected to bull block drawing using the lubricating oil A and the lubricating oil B used in Examples 1 and 2, and a pipe outer diameter of 15.88 mm and meat Thickness 0.71 mm, length 1,
It was processed into a coil of 800 m. The inside of this coiled copper tube was replaced with hydrogen gas for general industrial use (purity of 99.99% or more) and then continuously annealed in a DX gas atmosphere using a roller hearth furnace. After the annealing treatment, 2 m long samples for analysis were taken from three locations at both ends and the center of each coiled copper tube, and the amount of residual carbon film in the tube was calculated as the free carbon amount according to the method described in Example 1. It was judged. The results are shown in Table 3.

Comparative Example 3 The inside of a phosphorus-deoxidized copper tube having the same material and dimensions as drawn by the same conditions as in Example 3 was replaced with N ₂ + 5% H ₂ gas, and annealed under the same conditions as in Example 3. After that, the amount of free carbon was measured by the same method as in Example 3. The measurement results are shown in Table 3.

[0025]

[Table 3]

As shown in Table 3, the amount of free carbon in the copper tube treated according to the present invention was reduced to 1/3 to 1/10 of the free carbon in the copper tube according to the comparative example. No oxidative discoloration was observed.

[0027]

According to the present invention, the formation of carbonaceous film on the phosphorus deoxidized copper pipe for piping can be significantly reduced, so that it is possible to prevent the occurrence of cold water type pitting corrosion on the copper pipe for piping. Becomes The present invention also installs a hydrogen gas supply device,
By adding a hydrogen gas introduction process, the existing process can be performed with almost no change to the conventional process, so that the production cost does not increase, and a copper pipe with cold water resistant pitting corrosion is not produced. It contributes to stable supply and is extremely useful in industry.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Seiken Sawa, 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industry Co., Ltd.

Claims (4)

[Claims] 1. A method of manufacturing a soft or semi-hard phosphorus deoxidized copper pipe for piping, which is subjected to annealing treatment for tempering, after replacing the inside of the drawn copper pipe with hydrogen gas, and then nonoxidizing or reducing. A method for producing a copper pipe for cold water resistant pitting corrosion, which comprises annealing in a strong atmosphere to reduce the formation of a carbonaceous film on the inner surface of the copper pipe. 2. The method for producing a cold water resistant copper pipe for pitting corrosion according to claim 1, wherein the hydrogen gas has a purity of 99% or more. 3. The cold water resistant pitting corrosion corrosion resistant corrosion resistant pitting corrosion corrosion resistant pitting corrosion resistant pit according to claim 1, characterized in that after the inside of the copper pipe is replaced with hydrogen gas, both ends of the copper pipe are sealed and annealed in a non-oxidizing or reducing atmosphere. Copper pipe manufacturing method. 4. The cold water resistant type according to claim 1, wherein after the inside of the copper pipe is replaced with hydrogen gas, annealing is performed in a non-oxidizing or reducing atmosphere without sealing both ends of the copper pipe. Manufacturing method of copper tube for pitting corrosion.