JPH03229836A - Corrosion-resistant copper alloy tube - Google Patents

Abstract

PURPOSE:To stably reduce the elution of Cu ions in a copper alloy tube by subjecting a copper alloy tube essentially contg. specified amounts of Al and Sn to oxidation treatment in a specified oxygen contg. atmosphere and forming an oxidized film on the surface. CONSTITUTION:The compsn. of this copper alloy tube is formed from the one essentially contg., by weight, 0.1 to 2.5% Al and 0.01 to 2.5% Sn (where Sn>=Al/10 is regulated), contg. total 0.001 to 0.5% of one or more kinds among P, Mg, B, Mn and Si and the balance Cu with inevitable impurities. The copper alloy tube is subjected to oxidation treatment in an atmosphere contg. >=1ppm oxygen at >=150 deg.C to form as oxidized film of 0.01 to 10mum on the surface. As for the above atmosphere, the content of moisture is preferably regulated to <=1ppm. In this way, the generation of the deterioration in water quality caused by the elution of Cu can be prevented.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a corrosion-resistant copper alloy pipe, and more specifically, the present invention relates to a corrosion-resistant copper alloy pipe that has excellent resistance to Cu ion elution and is used as a piping material for water supply/hot water supply, etc. This relates to alloy tubes.

[Prior Art] Deoxidized copper, which has excellent corrosion resistance and workability, is widely used as a piping material for water supply, hot water supply, etc. However, even with deoxidized copper, it cannot be said that it fully satisfies the required properties, and depending on the water quality, Cu ions may be gradually eluted, causing the problem of blue water generation.

That is, when the amount of Cu ions eluted from the pipes increases and exceeds the water quality standard value for tap water (Cu 1.0 ppm), a problem arises in that laundry etc. are colored blue by the Cu ions. On the other hand, it is known that as the period of use passes, an oxide film is formed on the surface and Cu ions no longer elute. However, it takes a long period of time, such as 1 to 2 years, for such an oxide film to be formed on the inner surface of the water/hot water supply pipe, and the problem of Cu ion elution during that time cannot be avoided.

As a technology that solved this problem, A℃: 001~1,
5% (weight %: same below), Sn: 0.03-2.
Contains 5% (however, Sn+AIl≧01%), P, Mg,
One or more of B, Mn and Si in a total amount of 0.0
A corrosion-resistant copper alloy formed by forming a silicate film with a thickness of 0.01 to 10 μm on the inner surface of a copper alloy whose oxygen content is regulated to 0.05 to 0.5% and regulated to 1100 pp or less, and the remainder is Cu and inevitable impurities. pipes are provided (Tokuko Sho 6)
2-34821).

However, in the technique described in the above publication, a silicate film is formed, and a chemical such as coroital silica is required to form the silicate film.

[Problem to be solved by the invention] Under these circumstances, the present invention provides a corrosion-resistant copper alloy that can stably and reliably reduce the elution of Cu ions, regardless of the length of use, and does not require the use of chemicals. The purpose is to provide pipes.

[Means for Solving the Problems] The corrosion-resistant copper alloy tube of the present invention has AJ2: 0.1 to 2.5%.
(same below as weight%), Sn: 0.01 to 25% (however, Sn≧Afl/10), P, Mg, B,
One or more of Mn and Si in a total amount of 0.001
A copper alloy tube containing ~0.5% and the balance consisting of Cu and unavoidable impurities, containing 1 ppm or more of oxygen = 0,01 formed by oxidation treatment at 150°C or higher in an ambient atmosphere ~IDI! It is characterized by having a 7m long oxide film on its surface.

[Operations] Below, we will explain in detail the reasons for stipulating the above requirements, and
The function of the present invention will be clarified.

The oxide film formed on the inner surface of the steel pipe in water is Cu20. C
As long as these films are uniformly formed, the amount of Cu ions eluted will hardly exceed the standard value under normal usage conditions.

However, it has been experienced that the amount of Cu ions eluted exceeds the standard value during the initial stage of use until a film is formed, or when the water quality has a low pH and the film is highly soluble.

So, Cu20. As a measure to form a film other than CuO quickly and with high stability even in low pH water, Japanese Patent Publication No. 62-34821 discloses that an appropriate amount of A
u is added to form a silicate film.

A detailed study of the alloy described in Japanese Patent Publication No. 62-34821 revealed that when oxidized in a specific oxidizing atmosphere, aluminum such as AJ2303 forms on the surface layer even more than the Cu wood film such as Cu2O and CuO. Oxide and Afl(○
It has been found that aluminum hydroxides such as H) 3 are formed.

It was also found that the elution of Cu from Cu and Cu20CuO is suppressed by these skin moles.

Therefore, it was confirmed that in order to obtain the effect of suppressing Cu elution by A1 from the initial stage of use, it is sufficient to carry out oxidation treatment in an oxygen-containing atmosphere during the production of copper tubes without forming a silicate film. This is thought to be because aluminum oxide is formed on the outermost surface layer because AJZ has a stronger affinity for oxygen than Cu.

However, in order to suppress the amount of Cu elution to less than lppm of the water quality standard, the thickness of the oxide film needs to be 0.01 μm or more. On the other hand, if the film thickness exceeds 10 μm, cracks will occur in the film during bending of the tube, causing peeling. Therefore, the appropriate thickness of the oxide film is in the range of 0.001 to 10 μm.

Next, the reason for limiting the content of each additive element will be explained.

As mentioned above, Au is a main component of the present invention. 0
．． If it is less than 1%, the effect of suppressing Cu elution is not practical.
0.1% or more is required.

However, when Al is added to Cu, the bondability of brazing, which is an advantage of copper pipes, decreases.As a result of investigating various additive elements for the purpose of improving this, it was found that the addition of Sn is effective. As a result of investigating the heading and the required amount to be added, it was found that 1/10 or more of the amount of AJZ is required in terms of weight ratio. Therefore, Sn is the second major component of the present invention next to AJZ.

However, if the amount of A°C added is too large, the workability during pipe making will decrease, so it should be kept below 2.5%. Also, if the amount of Sn added is too large, the hot workability will decrease. .5%
Must be kept below.

Also, are P, Mg, B, and Mn deoxidizing elements to obtain a healthy ingot, or is it necessary to contain appropriate amounts of these deoxidizing elements in order to suppress hydrogen embrittlement in copper pipes? is necessary.

In other words, it is known that when brazing is heated with a torch in an oxidizing atmosphere and then heated in a reducing atmosphere, for example, oxygen-free copper tends to become brittle. It is thought that oxygen diffuses into copper when it is heated in a reducing atmosphere, and this oxygen reacts with hydrogen that enters when it is heated in a reducing atmosphere, causing hydrogen embrittlement. ing. However, if a small amount of elements that have a strong bonding force with oxygen are included as mentioned above, oxygen will penetrate deep into the body because these elements will combine with the oxygen that enters when heated in an oxidizing atmosphere. As a result, hydrogen embrittlement is thought to be less likely to occur. However, if the amount of these deoxidizing elements is too large, the processability will deteriorate, so the total amount should be kept at most 0.5% or less, preferably 0.1% or less.

On the other hand, as a result of various studies regarding the oxidation treatment conditions, it was determined that it is appropriate to form an oxide film in an oxygen atmosphere containing jppm or more of oxygen and by heating to 150° C. or higher. This is because an oxide film will not be formed even if heated to a high temperature below 1ppm, and at 150°C
This is because if it is less than that, an appropriate oxide film will not be formed even in an atmosphere with a high oxygen content.

Roughly speaking, the above-mentioned = moisture content as surrounding air is less than 1 ppm, preferably less than number + Pl), more preferably less than number p
By using an atmosphere containing less than Pb, it is possible to significantly reduce the amount of Cu discharged, and the brazing properties are further improved.

[Example] Using a copper alloy with the chemical composition shown in Table 1, the inner diameter was 21 mm.
x Copper alloy tubes with a wall thickness of 1.0 mm were produced and further subjected to oxidation treatment to produce various test tubes.

The thickness of the oxide film was calculated from the etching time until the metal element of the base material was detected by Auger analysis in the depth direction.

The amount of Cu eluted from the test tube was measured by passing water through the test tube under model water supply conditions, periodically removing it, filling the tube with water for 24 hours, and measuring the amount eluted during that time. Table 1 shows the change over time in the amount of Cu eluted. In addition, in order to compare the characteristics of the copper alloy pipe of the present invention with a conventional steel pipe (phosphorus deoxidized steel pipe) (CI220T), No. 3, 9, and 10 in Table 1 were
The elution amount was graphed and shown in FIG.

In addition, each test tube was brazed using a soft solder, and the filling rate of the solder when a socket (C1220T) was brazed at 300° C. was determined and used for evaluation. The filling rate of wax is shown in Table 1.

The copper alloy tubes (No. 1 to 9) of the present invention are the conventional steel tubes (No. 1 to 9).
The amount of Cu eluted is smaller than that of C1220T).

However, No. 9 does not have an appropriate thickness of oxide film, so the value is high at the initial stage of water flow. Furthermore, no decrease in properties was observed in brazing.

On the other hand, since No. 1l has a low Al content, the amount of Cu eluted reached the water quality standard value of 1 ppm. Also, No. 12 is S
Since n is less than 1/10 of the amount of Al, the filling rate of the solder is low, which means that the brazing properties have deteriorated.

On the other hand, Table 2 shows the influence of oxidation treatment conditions. No. 4 in Table 1 was used as the test gold.

Nos. 4.13 and 15.17 in the Table of Contents were prepared under the oxidation treatment conditions within the range of the present invention, and the film thickness was 0.01 μm or more, and the amount of Cu eluted after 10 days was as small as about 0.3 ppm.

In addition, No. 14 has an oxygen concentration lower than the range of the present invention, and N
016 has a heating temperature higher than the range of the present invention, so the film thickness is 0.
．． The Cu elution amount is also as high as 0.8 ppm.

Furthermore, in the case of No. 17, which was oxidized in an ambient atmosphere, the amount of Cu eluted was significantly reduced.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to reliably prevent water quality deterioration due to Cu elution.

[Brief explanation of drawings]

FIG. 1 is a graph showing changes over time in the Cu elution amount of typical test tubes.

Claims (2)

[Claims] (1) Al: 0.1 to 2.5% (weight%: same below),
Essentially contains Sn: 0.01 to 2.5% (however, Sn≧Al/10), and one or more of P, Mg, B, Mn, and Si in a total amount of 0.001 to 0.5 %, the balance being Cu and unavoidable impurities, the tube is formed by oxidation treatment at 150°C or higher in an oxygen-containing atmosphere containing 1 ppm or more of oxygen. A corrosion-resistant copper alloy tube characterized by having a 10 μm oxide film on its surface. (2) The corrosion-resistant copper alloy tube according to claim 1, wherein the atmosphere has a moisture content of 1 ppm or less.