EP1798298B1 - Use of a low-migration copper alloy and parts made of such alloy - Google Patents

Abstract

A copper alloy is used in the production of components for drinking water pipes and their fittings. The alloy contains (wt.%): 2.8-4 silicon; 1-15 zinc; 0.05-2 manganese; 80-96.95 copper; and optionally 0.05-0.4 aluminum and 0.05-2 tin. An independent claim is also included for a component made from the above copper alloy used for the production of drinking water pipes.

Description

The present invention relates to the use of a low-migration copper alloy for the production of components for gas and sanitary installation, especially for components that are used in drinking water installation and directly with the in the components, usually pipes, fittings and fittings, guided drinking water in Contact, as well as components consisting of such copper alloy.

Materials for the production of components for the gas and water installation are subject to special requirements, which are placed in particular on drinking water pipes and their components. First and foremost, the corrosion resistance of the components must be mentioned, because the components used should not corrode even after many years of use. In addition, special demands are made on the manufacturability and processability, with the alloys not only having to be simply and economically cast, but also the requirement that the cast components are easy to machine mechanically. Particular attention should be paid to a good machinability. Finally, the components produced from the copper alloy must also withstand the mechanical stresses required for the application. Thus, a tensile strength of more than 180 N / mm ² at a 0.2% proof stress of 85 N / mm ² is regularly considered necessary for copper-tin-zinc alloys. For bronzes (copper-tin alloys) the tensile strength should be 240 N / mm ² and the 0.2% proof stress 130 N / mm ² and more.

Of particular interest is also the behavior of the materials with regard to the release of ions of the alloy components of the materials or of reaction products with water constituents. Here, very narrow limits are to be observed for the protection of consumers with regard to the permitted release of metal ions from the components into the drinking water.

In addition to other alloys, highly copper-containing non-ferrous metal alloys, such as bronze or gunmetal, are also used today for producing the media-carrying components of gas and water pipes. In view of good machinability, certain amounts of lead are added to these non-ferrous metal alloys. To increase the corrosion resistance and the strength, the addition of nickel is preferable.

Conventional representatives of bronze casting alloys are compiled in DIN EN 1982. By way of example, the gun metal alloy CuSn5Zn5Pb5 with in each case between 4 to 6 wt .-% tin, zinc and lead at a level of up to 2.0 wt .-% nickel and up to 0.1 wt .-% phosphorus and as Admixtures up to 0.3 wt .-% iron and up to 0.25 wt .-% antimony are called. Although this material is characterized by good castability and corrosion resistance to seawater. With regard to the release of metal ions into the water, however, this material must be regarded as unsatisfactory against the background of the future expected limit values. Here, in particular, the high lead levy of CuSn5Zn5Pb5 is criticized.

With the EP-1 045 041 A lead-free copper alloy has already been proposed which is said to have satisfactory machinability and which comprises up to 79% by weight of copper, from 2 to 4% by weight of silicon and the remainder zinc. This alloy is particularly suitable for the production of fittings, fittings and the like parts for water-bearing piping systems in question. However, the alloy does not behave like gunmetal, particularly with regard to corrosion resistance, and consequently can not substitute it.

The GB-1 443 090 discloses a dezincification-enhanced copper alloy having between 80 and 90 weight percent copper, between 6.3 and 17.5 weight percent zinc, and between 2.8 and 4.75 weight percent silicon as essential alloying ingredients between 0.03 and 0.05% by weight of arsenic. To improve the corrosion properties is proposed by the proposed solution GB-1, 443,090 proposed a heat treatment of the cast parts. In this heat treatment, the cast parts are annealed at temperatures between 600 ° C and 750 ° C for a period of 5 to 10 days and then quenched. This heat treatment is carried out with the aim of obtaining the α and ξ phases to be preferred in view of the corrosion. By quenching in particular the formation of phases is to be avoided, the corrosion resistance is low, so the p and χ phase.

From the GB-1 385 411 For example, a copper alloy containing up to 10% by weight of aluminum is known and up to 5 wt .-% iron and which is used for the production of water-bearing components of water installations. However, this alloy shows inadequate corrosion behavior and, in particular, excessive migration of metal ions into the water.

The present invention is based on the problem of providing a migration behavior improved copper alloy, which is particularly suitable for the production of media-carrying gas or water pipes and their parts and the good corrosion resistance to the media, good strength and good machinability and castability Has. In terms of machinability, in particular, the chipping properties of the copper alloy are important. In addition, the invention wants to specify corresponding media-carrying components, in particular fittings or fittings, as well as an advantageous use of the copper alloy according to the invention.

With regard to the fabric-related aspect of the present invention, the use of a copper alloy having the features of claim 1 is proposed. This copper alloy comprises between 2 and 4.5% by weight of silicon, between 1 and 15% by weight of zinc and between 0.05 and 2% by weight of manganese. In addition to these necessary elements, the copper alloy may contain between 0.05 and 0.4% by weight of aluminum and / or between 0.05 and 2% by weight of tin. The remainder of the alloy contains copper and unavoidable impurities. These impurities are preferably limited to a content of 0.5% by weight. Most preferably, the upper limit for the impurities is 0.25%. This upper limit applies in particular to the cumulative nickel and lead content in the alloy, which has proven to be a particularly effective measure for suppressing the migration of lead or nickel. In view of this, the alloy is preferably free of lead and / or nickel. As a lead-free alloy, an alloy is considered in which the content of lead is less than 0.25%. The nickel-free alloy is considered to be an alloy in which the nickel content is less than 0.15%.

It has been found that with a copper alloy, as specified in claim 1, as best as possible to be placed on components for media-carrying gas or water pipes requirements can be met. That's how it shows Alloy a good casting behavior. The components produced by casting can be machined well. Tests on specimens have shown that the strength meets the requirements to be met. In addition, the corrosion resistance of the alloy is high.

In practical experiments it could be confirmed that the components in question for media-carrying lines easily with the usual casting process, for example, in the sand, mold, spin or continuous casting can be produced. With regard to the cooling conditions from the melt, there are no special requirements. The casting thus obtained can be processed well spanhebend. To reduce the tendency of the casting to migrate, it may preferably be subjected to a heat treatment before machining. In this case, the casting is preferably annealed at between 400 ° C and 800 ° C for at least half an hour. Preferably, the heat treatment is carried out in a temperature interval of between 600 ° C and 700 ° C. The glow time can be any length. In terms of economic constraints, however, this is set at between 2 and 16 hours. In this glow time, the Aufzeitphase is not included.

The annealing takes place in particular with the aim of adjusting the α-phase in the cast component, which, according to the present inventions, enables the combination of different properties to be achieved. It should be noted, however, that even the vast majority of the necessary alloying elements copper, zinc and silicon solidifies in a natural cooling from the melt without separate heat treatment in the form of α-mixed crystals.

Addition of silicon within the specified interval also promotes chip breakage during processing. However, with increasing silicon content, tool wear also increases in the machining of components made of the alloy. Accordingly, the upper limit of the silicon content is set to 4.5 wt% not least in view of the machinability of the alloy.

With regard to the required corrosion resistance is in the Copper alloy, the zinc content limited to 15 wt .-%. On the other hand, a minimum content of 1% by weight of zinc guarantees a minimum of machinability.

Manganese is added to the alloy within the limits of 0.05 to 2% by weight in order to improve the microstructure. Manganese refines the microstructure and positively influences the solidification behavior of the copper alloy. However, the manganese content is limited to 2% by weight in consideration of the migration tendency of manganese.

Limiting the sum of the impurities to a maximum of 0.5% by weight limits the content of ingredients that may possibly migrate into the drinking water to a minimum that is also economically desirable. With a further limited upper limit of the unavoidable impurities of 0.25% by weight, a higher security against migration, but at the expense of manufacturing costs, can be achieved.

Preferably, the alloy contains between 5 and 15% by weight of zinc. In this limited interval, the best possible combination of corrosion resistance and machinability can be achieved.

In order to optimize the strength with sufficient elongation properties of the material in combination with good migration values, the silicon content is set at between 2.8% by weight and 4% by weight.

To further reduce the migration tendency of manganese, its content is preferably set at 0.2 to 0.6 wt .-%. The alloy preferably contains no nickel or lead at all for the same reasons. The copper content in the alloy should be at least 80 and not more than 96.95% by weight.

According to one aspect of the present invention, the use of the copper alloy for the production of components for media-carrying gas or water pipes is proposed. These are in particular those components to understand that form drinking water pipes, in particular fittings and fittings and parts thereof. Not least because of the good stress-strain properties The copper alloy should preferably be made of a compression connector of the copper alloy according to the invention. The compression connectors can either be designed as separate components or be provided with material or positive fit to the fitting or the fitting. Also, the press connectors can be realized as integral components in the casting of the fitting or fitting from the copper alloy. The casting alloy is particularly suitable for producing an element of a press connection arrangement, as for example from the EP 0 343 395 or the DE 10 2004 031 247 is known.

Fig. 1

ein Schaubild mit einem Vergleich der Bleimigration eines Ausführungsbeispiels der Kupferlegierung gegenüber einer anderen konventionellen Rotguss-Legierung;

Fig. 2

ein Schaubild mit einem Vergleich der Nickelmigration eines Ausführungsbeispiels der Kupferlegierung gegenüber einer anderen konventionellen Rotguss-Legierung;

Fig. 3

ein Schaubild mit einem Vergleich der Kupfermigration eines Ausführungsbeispiels der Kupferlegierung gegenüber einer anderen konventionellen Rotguss-Legierung; und

Fig. 4

ein Schaubild mit einem Vergleich der Zinkmigration eines Ausführungsbeispiels der Kupferlegierung gegenüber einer anderen konventionellen Rotguss-Legierung.

The present invention will be illustrated below with reference to an embodiment in conjunction with the drawings. The drawing shows:

Fig. 1

a graph comparing the lead migration of one embodiment of the copper alloy over another conventional gunmetal alloy;

Fig. 2

a graph comparing nickel migration of one embodiment of the copper alloy versus another conventional gunmetal alloy;

Fig. 3

a graph comparing copper migration of one embodiment of the copper alloy versus another conventional gunmetal alloy; and

Fig. 4

a graph comparing zinc migration of one embodiment of the copper alloy over another conventional gunmetal alloy.

Figs. 1 to 4 show the time course of the release of certain metal ions in a measurement arrangement according to DIN 50931-1 over a total period of 26 weeks. DIN specifies the test arrangement and test conditions with which the corrosion probability of materials for metallic components of a drinking water installation can be determined in the case of corrosive contamination of drinking water.

• Si: 3,5 Gew.-%;
• Zn: 1,6 Gew.-%;
• Mn: 0,5 Gew.-%;
• unvermeidbare Verunreinigungen in Summe: max. 0,5 Gew.-%;
• und als Rest Kupfer.

Shown in each case is the time profile when using an exemplary embodiment of a copper alloy having the following composition:

• Si: 3.5% by weight;
• Zn: 1.6% by weight;
• Mn: 0.5% by weight;
• unavoidable impurities in total: max. 0.5% by weight;
• and as the rest of copper.

• Zn: 5,5 Gew.-%;
• Sn: 4,5 Gew.-%;
• Pb: 3,0 Gew.-%;
• Ni: 0,5 Gew.-%;
• Rest: Kupfer und unvermeidbare Verunreinigungen.

The results are compared in the respective representations of FIGS. 1 to 4 with those measured values that can be achieved in a conventional gunmetal alloy under the same experimental conditions. The gunmetal alloy has the following composition:

• Zn: 5.5% by weight;
• Sn: 4.5% by weight;
• Pb: 3.0% by weight;
• Ni: 0.5% by weight;
• Remainder: copper and unavoidable impurities.

The measurement results with the exemplary embodiment of the copper alloy are marked with A. The comparison measurement with the gunmetal alloy with B.

In addition to the above-mentioned comparison, FIGS. 1 to 3 also contain a limit value according to the German Drinking Water Ordinance (TrinkwV) for the delivery of certain ions to water and the parameter value W (15) to be observed during migration tests. This parameter value W (15) must be adhered to if it is intended to avoid exceeding the value of the TrinkwV when using the tested component. The parameter value W (15) results from the product of the limit value according to the TrinkwV and the ratio of the form factors A and B. According to DIN 50931-1, the form factor A results from the ratio of the water-contacted surface of the material to the water-contacting surface of the entire test section. The form factor B is a normalization factor in accordance with DIN 50930-6, which takes into account the type of components.

FIG. 1 illustrates that the lead-release quantity of the gunmetal alloy drops from a very high value, greater than 50 μg / l, almost exponentially within the first four weeks of testing to a value which is just above the limit of the German drinking water regulations of 10 μg / l. l after 12 to 26 weeks of testing. At the beginning of the tests, this significant excess is attributed to the fact that lead, which had been introduced to the surface of the component to be tested, migrated into the drinking water as a result of the processing and production of the test part. After the first few weeks, the near-surface lead has migrated out of the sample and the amount of discharged lead remains approximately constant.

By contrast, the exemplary embodiment according to A gives virtually no lead to the drinking water. Even an increased value at the beginning of the experiments can not be seen. Since the measured values are at the limit of the resolution of the measurement analysis, the fluctuations in the measured values are attributed to the measuring accuracy of the measuring apparatus. Essentially, the measured value for the lead release in the sample remains well below the limit value of the TrinkwV of 10 μg / l.

The same applies to the nickel output shown in FIG. 2 of the compared samples. The comparison sample from the gunmetal alloy shows a typical course in which the conventional alloy after nine weeks exceeds the limit value according to the German TrinkwV, after a maximum in about the 18th Week slowly back to the limit value of the TrinkwV. Although the increase in the nickel concentration in drinking water can not be explained exactly by the gunmetal alloy B so far. The increase is reproducible. The limit issued by the TrinkwV is not met.

In comparison, the copper alloy A gives no appreciable nickel ions to the drinking water. Here, too, the measured values of about 2 μg / l are in the range of the resolution of the analysis related to the measuring instruments.

For copper delivery (Figure 3), the two compared alloys are essentially the same course. However, the alloy A assumes lower values for the copper release in μg / l within the time-meaningful experimental results. The maximum for both alloys is the measured value after 18 weeks of testing. Thereafter, the copper output drops for both alloys. The better migration values for the element copper over conventional gunmetal prove the improved corrosion resistance of the alloy A and were not to be expected at first, since the alloy A has a higher copper content than conventional gunmetal. However, it has been shown that it is precisely this high copper content of 80% and higher that is the main reason for the improved migration behavior. Incidentally, both alloys, even at their maximum, maintain a sufficient distance from the W (15 value). Taking into account the experimental set-up, this results in compliance with the limit values according to TrinkwV. In comparison, however, it is noticeable that the alloy A compared to the conventional alloy B with a difference of about 500 micrograms / l, corresponding to 20 to 25% cheaper, behaves.

Finally, Fig. 4 shows the amount of zinc released by the alloy into the drinking water. For zinc, no limit is set according to the TrinkwV. The course of the zinc release in the case of the copper alloy A differs considerably from the corresponding course for the comparative alloy B. The migration of the embodiment A of the alloy of zinc is below 100 μg / l at all times. The conventional alloy B exceeds this value many times.

The diagrams shown in FIGS. 1 to 4 illustrate the advantages of the copper alloy A, in particular the influence of the silicon for suppressing unwanted metal ion migration into the drinking water.

Claims (17)

1. Use of a copper alloy for the manufacture of components for medium-conducting gas pipes and/or water pipes, in particular drinking-water pipes, and valves and fittings for the same, the copper alloy comprising, in wt%: $$2.8\le \mathrm{Si}\le 4,$$

   

   $$1\le \mathrm{Zn}\le 15,$$

   

   $$0.05\le \mathrm{Mn}\le 2,$$

   

   and $$80\le \mathrm{Cu}\le 96.95,$$

   

   optionally further comprising: $$0.05\le \mathrm{AI}\le 0.4,$$

   

   $$0.05\le \mathrm{Sn}\le 2,$$

   

   and unavoidable impurities.
2. Use according to Claim 1, characterized in that the copper alloy is used for the manufacture of compression couplings.
3. Use according to Claim 1, characterized in that the copper alloy is used for the manufacture of valves and fittings with a permanent compression joint.
4. Use according to any one of Claims 1 to 3, characterized in that 5 wt% ≤ Zn ≤ 15 wt%.
5. Use according to any one of Claims 1 to 4, characterized in that 0.2 wt% ≤ Mn ≤ 0.6 wt%.
6. Use according to Claim 5, characterized in that the unavoidable impurities contained total is not more than 0.5 wt%.
7. Use according to Claim 6, characterized in that the unavoidable impurities contained total is not more than 0.25 wt%.
8. Use according to Claim 6 or Claim 7, characterized in that any Ni and/or Pb contained as unavoidable impurities totals not more than 0.25 wt%.
9. Components for medium-conducting gas pipes and/or water pipes, in particular drinking-water pipes, and valves and fittings for the same, at least partly consisting of a copper alloy comprising, in wt%: $$2.8\le \mathrm{Si}\le 4,$$

   

   $$1\le \mathrm{Zn}\le 15,$$

   

   $$0.05\le \mathrm{Mn}\le 2,$$

   

   and $$80\le \mathrm{Cu}\le 96.95,$$

   

   optionally further comprising: $$0.05\le \mathrm{AI}\le 0.4,$$

   

   $$0.05\le \mathrm{Sn}\le 2,$$

   

   and unavoidable impurities.
10. Component according to Claim 9, characterized in that more than 98 wt% of the elements Cu, Zn and Si is present in the form of an alpha mixed crystal.
11. Components according to Claim 9 or Claim 10, characterized in that the components are compression couplings.
12. Components according to any one of Claims 9 to 11, characterized in that the components are valves or fittings with a permanent compression joint.
13. Component according to any one of Claims 9 to 12, characterized in that 5 wt% ≤ Zn ≤ 15 wt%.
14. Component according to any one of Claims 9 to 13, characterized in that 0.2 wt% ≤ Mn ≤ 0.6 wt%.
15. Component according to Claim 14, characterized in that the unavoidable impurities contained total is not more than 0.5 wt%.
16. Component according to Claim 15, characterized in that the unavoidable impurities contained total is not more than 0.25 wt%.
17. Component according to either of Claims 15 and 16, characterized in that any Ni and/or Pb contained as unavoidable impurities totals not more than 0.25 wt%.

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