JPH0647715B2 - Copper pipe for hot water supply - Google Patents

Description

The present invention relates to a hot water supply copper pipe used in a hot water piping system.

[Prior art and its problems] As the piping materials for tap water and hot water, various materials such as copper, copper, stainless steel, alloy resin, plated steel pipe, and synthetic resin coated steel pipe are used. Copper pipes are widely used because of their good workability and good corrosion resistance to water and hot water. Especially for hot water pipes in buildings, their stability and workability are evaluated, and a large amount of copper pipes are used. Is used for. However, in a special water environment, the surface of the copper pipe may dissolve, and the copper concentration in the water may exceed 1 ppm (mg /), which is the water quality standard for tap water of the Ministry of Health. Even if the copper concentration is less than 1 ppm, when a sanitary facility or the like is used for a long period of time, this copper may be precipitated as a copper salt and may be colored blue. As a measure for reducing the copper solution, water quality, that is, mitigation of corrosive environment, change of material and the like have been conventionally performed, but there are the following problems.

Countermeasures for mitigating water quality and corrosive environment have been mainly implemented by introducing chemicals into water. For example, alkaline caustic soda, sodium bicarbonate, etc. have been injected for acidic water supply, and a small amount of sodium silicate, sodium phosphate, etc. have been injected for water quality in which scale as a protective film is difficult to form. However, with this method, it is necessary to supplement the consumption of chemicals and to install and maintain chemical injection equipment. In addition, these tasks are generally outsourced to specialized vendors and are not suitable for private housing.

As a countermeasure by changing the material, there is an example in which an alloy having a strong corrosion resistance, for example, stainless steel, or a resin-coated pipe that is stable for supplying water and hot water is adopted. However, with these materials, a simple brazing joint like a copper pipe is not possible, and especially with a cladding pipe or the like, the terminal treatment of the joint portion is difficult, and the corrosion resistance may remain a problem. In addition, as a measure for preventing the dissolution of copper, metal plating or the like has been performed, but there are problems that the terminal treatment is difficult as in the previous example, and that there is the influence of contact corrosion of different metals.

SUMMARY OF THE INVENTION In view of the above points, the present invention provides an inner surface of a copper pipe for hot water supply,
By forming a Cu-Sn alloy layer having a corrosion resistance and a tin concentration of 35% or less, it is possible to provide a copper tube that is less likely to dissolve copper and is easy to handle.

When Cu and Sn are alloyed, various intermetallic compounds are generated depending on the Sn concentration. Among these intermetallic compounds, ε
Phase (Cu-38.37% Sn) and η phase (Cu-60.8)
9% Sn) has particularly poor corrosion resistance and is not suitable as a protective coating layer on the inner surface of a copper pipe. Therefore, Cu-Sn on the inner surface of the copper tube
The alloy composition must have a Sn concentration of 35% or less.
If it is 35% or more, an intermetallic compound of Cu and Sn may be generated, which deteriorates corrosion resistance and mechanical properties.
Further, in order to improve the corrosion resistance, it is better to set the Sn concentration to 5% or more. The most corrosion resistant Sn concentration range is 5
The range of up to 20% is desirable.

The larger thickness of the alloy coating layer contributes to the improvement of corrosion resistance, but the Cu-Sn alloy has a high hardness, becomes difficult to process, and loses the original characteristics of the copper tube. It is desirable that the thickness is 50% or less. On the other hand, when the thickness is 3 μm or less, the effect as the protective coating layer is small and the corrosion resistance is about the same as pure copper.

The copper tube used for the base of the present invention may have a smooth inner surface, but it is preferable that the inner tube has small irregularities or projections. Although these irregularities or protrusions do not contribute to the original corrosion resistance, when a Cu—Sn alloy layer is formed by performing a heat diffusion treatment after coating Sn in the tube, a molten Cu—Sn alloy is used. It is extremely effective in maintaining a uniform thickness. Therefore, the irregularities or protrusions may have any structure that does not allow molten Cu-Sn alloy to flow out, and the shape thereof is a spiral or linearly extending groove in the pipe, independent protrusions, scratches processed with a wire brush or a file. The cross-sectional shape may be any of a rectangular shape, a trapezoidal shape, a triangular circular shape, and the like.

The height of this unevenness or protrusion is 0.01 mm (10 μm
If it is at least m), the molten alloy can be prevented from flowing out. On the other hand, when the thickness is 0.5 mm or more, the thickness of the Cu—Sn alloy layer formed on the upper portion of the convex portion or the protrusion becomes insufficient, and there is a possibility that the alloy layer becomes nonuniform.

[Examples] Example 1 After the inner surface of a phosphorus-deoxidized copper tube having an outer diameter of 28.58 mm and a wall thickness of 1.27 mm was machined with a large number of grooves having a groove height of 10 μm to 0.8 mm, Sn was formed on the inner surface. Was uniformly coated to a thickness of 0.5 to 20 μm. The copper pipes were heat-treated at 700 ° for 2 hours in an inert gas atmosphere to obtain the target Cu-S.
A copper tube having an n alloy layer was obtained.

Each of the obtained copper pipes was filled and sealed with tap water as shown in Table 1, heated at 70 ° C. for 24 hours, and then the copper elution amount in each copper pipe was measured. The results are shown in Table 2.

From Table 2, it can be seen that the elution amount of copper from the copper pipe can be significantly reduced by using the Cu-Sn alloy as the protective coating layer.

Example 2 A large number of protrusions having a height of 50 μm were formed on the inner surface, and the outer diameter was 2
Various S on the inner surface of a copper tube with a thickness of 8.58 mm and a wall thickness of 1.27 mm.
A Cu—Sn alloy layer having an n concentration was formed by coating to a thickness of 20 to 30 μm.

About each obtained copper pipe, tap water shown in Table 1
A corrosion test was conducted by continuously passing hot water under the conditions of ° C and 2 m / sec. Table 3 shows the results of calculating the corrosion rate for one year from the test time of 40 days.

From Table 3, it can be seen that the corrosion amount of the copper pipe can be significantly reduced by using a Cu—Sn alloy having a predetermined composition as the protective coating layer.

[Effects of the Invention] According to the present invention, a hot water supply copper pipe with less elution of copper can be obtained by forming a protective coating layer of a Cu-Sn alloy on the inner surface. Moreover, since the protective coating layer is thin, the protective coating layer can be used under the same conditions as the conventional one without coating, and it is not necessary to improve the connecting joint component.

Further, unlike a resin-coated tube, it has high heat resistance, and can withstand various heat treatments such as brazing and hot dipping on the outer surface.

In addition to preventing copper elution, various corrosion phenomena,
For example, there is a secondary effect that durability is increased against erosion and pitting corrosion.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masayuki Okuyama 19-18 Sakurada-cho, Atsuta-ku, Nagoya, Aichi Toho Gas Co., Ltd. (72) Inventor Kuniaki Seki 3550, Kidayo-cho, Tsuchiura-shi, Ibaraki Hitachi Cable Metal Research Laboratory Co., Ltd. (72) Inventor Shinichi Nishiyama 3550 Kidayo-cho, Tsuchiura City, Ibaraki Prefecture Hitachi Cable Metal Research Laboratory (72) Inventor Gen Abe 3550 Kidayo-machi, Tsuchiura City, Ibaraki Hitachi Cable Ltd. Metal Research In-house (72) Inventor Kiyoshi Oizumi 3550 Kidayo-cho, Tsuchiura-shi, Ibaraki Hitachi Cable Co., Ltd. Tsuchiura factory (56) Reference JP 49-111835 (JP, A) JP 60-121264 (JP, A) ) JP-A-60-200954 (JP, A) JP-B-38-25006 (JP, B2)

Claims (4)

[Claims] 1. A copper pipe for hot water supply, comprising a Cu-Sn alloy layer formed by diffusion of Sn and Cu on the inner surface of the copper pipe. 2. The Sn concentration in the Cu—Sn alloy layer is 3 by weight.
The copper pipe for hot water supply according to the above item 1, which is 5% or less. 3. The hot water supply copper pipe according to claim 1, wherein the thickness of the Cu—Sn alloy layer is 3 μm or more and 50% or less of the thickness of the copper pipe. 4. The inner surface has irregularities or protrusions having a height of 0.01 to 0.5 mm, and the surface of the irregularities or protrusions is C.
The first term, the second term, or the third term having a u-Sn alloy layer.
Copper pipe for hot water supply according to item.