JPS60200987A - Corrosion resistant welded copper pipe and its production - Google Patents

Abstract

PURPOSE:To provide a corrosion resistant welded copper pipe which can eliminate the problem of corrosion as a capillary for a condenser even if said pipe is a long-sized pipe having a small diameter by coating part or the whole of the inside surface of the pipe obtd. by forming a copper (alloy) bar to a tubular shape and welding the same with a metal exhibiting the baser potential than said pipe in using environment. CONSTITUTION:Zn is hot dipped over the entire length on one surface of a bar consisting of, for example, deoxidized copper and having 1mm. thickness and 80mm. width to 20mm. width and 40mu thickness. The bar is then formed to a tubular shape with the galvanized side faced inward and the seam of the bar is Tig- welded and thereafter the weld beads are removed. The objective welded copper pipe 1 having a weld zone 2 in the axial direction thereof and a belt-like galvanized layer 3 in the axial direction of the inside surface thereof is thus obtd. The effect resulted from electrolytic protection is obtd. over the entire length by such welded copper pipe by which the problem of corrosion such as pitting, errosion-corrosion, green water, etc. is solved as a feed pipe for water and hot water.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copper-based welded pipe with excellent corrosion resistance and a method for manufacturing the same, and in particular, solves corrosion problems such as pitting corrosion, erosion corrosion, and blue water in water supply and hot water supply pipes. This solves problems such as erosion of condenser tubes and corrosion of contaminated seawater.

Copper or copper alloys are originally materials with excellent corrosion resistance, and are suitable for water supply,
It is used for various purposes, including hot water supply pipes and condenser tubes, and these pipes are usually made by forming thread into a tubular shape and welding the seams or by drawing. However, the corrosion resistance of these pipe materials is not sufficient.
Pitting corrosion, erosion, blue water, etc. have been reported when used for water supply and hot water supply pipes, and occurrence of erosion, contaminated seawater corrosion, etc. has been reported when used for condenser tubes. .

Such corrosion damage causes water leakage and the like, leading to plant failure and lack of comfortable living space, so various countermeasures have been proposed. For example, inhibitors are added and deaerated to water and hot water supply pipes, and various types of heat exchangers, such as thin tubes for condensers, are coated inside and inhibitors are added. However, all of these methods are incomplete and water leaks occur at a rate of once to several times a year, and there is a strong desire for improvement.

Possible methods of making the inner surface of copper-based pipe materials highly corrosion resistant include plating and electrolytic protection. However, it is technically difficult to plate the inner surface of a long, narrow-diameter tube, and it cannot be put to practical use when pretreatment (degreasing, pickling, water washing, etc.) of the inner surface of the tube and reliability are taken into consideration. Further, in cathodic protection, which is most effective in preventing corrosion, current is not supplied from the anode to the cathode inside the small diameter long tube to be protected, and the corrosion effect only affects a portion of the tube end. It is also possible to use a highly corrosion-resistant material instead of the copper-based pipe material, but this has the drawback of being expensive.

In view of this, as a result of various studies, the present invention solves the corrosion problems such as pitting corrosion, erosion corrosion, and blue water for water supply and hot water supply pipes, and solves the problems such as corrosion corrosion and contaminated seawater corrosion as thin pipes for condensers. The present invention discloses a corrosion-resistant copper welded pipe and a method for manufacturing the same, and the welded pipe of the present invention is a pipe in which copper or copper alloy strips are formed into a tubular shape and welded. It is characterized by being coated with a metal that exhibits a more base potential in the usage environment.

In addition, the method for manufacturing the welded pipe of the present invention involves coating a part or the entire surface of a copper or copper alloy strip with a metal that exhibits a baser potential in the usage environment than the strip, and forming it into a tubular shape with the coated surface inside. The feature is that the seams between the strips are then welded.

In other words, the welded pipe of the present invention is a pipe in which copper or copper alloy strips are formed into a tubular shape and the joints of the strips are welded. When a working fluid is passed through a pipe coated with a metal that exhibits a base potential, such as zinc or iron, only the base metal will be eluted due to the principle of cathodic protection, and the welded pipe will be coated with a metal that exhibits a base potential, such as zinc or iron. C protection (corrosion protection) will be provided. The elution of base metals is not very fast, and a protective film with anti-corrosion effect is naturally formed on the inner surface of the welded pipe during the elution period of the base metals, so even after the base metals have been eluted and consumed. ,
Shows excellent corrosion resistance.

Such welded pipes are produced by coating a part or the entire surface of a copper or copper alloy strip with a metal that exhibits a potential of Ct4 in the usage environment, forming it into a tubular shape with the coated surface inside, and then forming the strip into a tubular shape. Constructed by welding the seams. The coating method is different from that for the inner surface of the tube, since the strip is coated with C, so it can be easily coated by heat fusion, electroplating, pressure bonding, etc. Further, it is desirable to weld the seam of the strips after forming into a tubular shape by various welding methods, and to remove any welding beats that occur.

Examples of the welded pipe of the present invention will be described in detail below.

Example (1) Using a strip of phosphorus deoxidized copper (JIS H3300, C1220) with a thickness of 1 mm and a width of 80 mm, one side of the strip was hot-dipped with zinc having a width of 20 mm and a thickness of 40 μm over the entire length. Forming into a tubular shape with the galvanized side inside, welding the seam of the strips by 1g, removing the weld bead, and cutting the welded part (
2), and a band-shaped galvanized layer (3) in the axial direction of the inner surface of the tube.
) A welded pipe (1) of the present invention was manufactured.

Tap water at 60°C containing 2 to 3 ppm of C (2) was passed through this welded pipe for one month, and the occurrence of pitting corrosion on the inner surface was examined. As a result, no pitting corrosion was observed on the inner surface of the welded pipe. Also, the eluted copper ω was measured and found to be 0.1tll)Ill. For comparison, a phosphorus-deoxidized copper seamless pipe manufactured by the drawing process was then passed through water in the same manner. As a result, a large number of pitting corrosion up to a depth of 0.3 mm was observed on the inner surface of the seamless pipe. The amount of copper ions also showed a very high value of 2.0 ppm.

Example (2) Aluminum brass (JIS H3300, C687
0) thickness 1.245#, rll 80 mm
6 in C, leaving a welded part in the longitudinal direction on one side.
0mm.

After crimping iron foil with a thickness of 20μ, forming it into a tube with the iron foil side inside, high-frequency welding the seam of the strips, removing the weld bead, and forming the tube in the axial direction as shown in Figure 2. It has a welded part (2) at about 10mm from the welded part (2).
A welded pipe (1) of the present invention having a steel foil pressure bonding layer (3a) on the inner surface of the pipe was manufactured with a spacing (() of The reason why the iron foil was soaked was to prevent iron from getting into the welding area.

Artificial seawater containing 0.3 ppm of 82-ions was passed through this welded pipe for two months, and the state of pitting corrosion on the inner surface of the pipe was reduced to 1!
, I got it. As a result, no pitting corrosion was observed on the inner surface of the tube. For comparison, an aluminum brass seamless pipe manufactured by the drawing method was subjected to water passage in the same manner, and numerous pitting corrosion up to a depth of 0.2 mm was observed on the inner surface of the seamless pipe.

Above, we have explained zinc-coated copper oxide welded pipe and iron foil-coated aluminum brass welded pipe, but this is not limited to these, and the same applies to other copper and steel alloy welded pipes. Similar results can be obtained, and the same effect can be obtained even if the metal coated on the inner surface of the tube is one that exhibits a lower potential in the operating environment than a copper-based welded tube.

As described above, according to the present invention, the effect based on cathodic protection can be obtained over the entire length of the pipe even if it is a long pipe with a small diameter, and corrosion problems such as pitting corrosion, erosion corrosion, and water leakage can be solved as water supply and hot water supply pipes. death,
It has remarkable industrial effects, such as being able to solve corrosion problems such as erosion and rotten seawater corrosion as a thin tube for condensers.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of one embodiment of the welded pipe of the present invention, and a second vagina is a partially cutaway perspective view of another embodiment of the welded pipe of the present invention. 1... Welded pipe 2... Welded part 3.3a... Covering metal layer

Claims (1)

[Scope of Claims] (1) A tube formed from copper or copper alloy strips and welded into a tubular shape, in which a part or the entire inner surface of the tube is coated with a metal that exhibits a lower potential in the usage environment than the tube. Corrosion-resistant copper-based welded pipes characterized by After processing the tubular form mink with the surface inside,
A method for manufacturing a corrosion-resistant copper-based welded pipe characterized by welding the joints of the strips.