EP3436615A2

EP3436615A2 - Component for media-conducting gas or water lines, which contains a copper alloy

Info

Publication number: EP3436615A2
Application number: EP17718474.4A
Authority: EP
Inventors: Martin Haake; Andreas Hansen; Frank Leistritz
Original assignee: Geberit International AG; Rehau AG and Co; Gebr Kemper GmbH and Co KG
Current assignee: Geberit International AG; Gebr Kemper GmbH and Co KG; Rehau Automotive SE and Co KG
Priority date: 2016-03-29
Filing date: 2017-03-28
Publication date: 2019-02-06

Abstract

The present invention relates to a component for media-conducting gas or water lines, in particular a fitting for supply lines of drinking water, wherein the component is at least partially made of a lead-free copper alloy which has the following alloy components in wt.%: 3.5 wt.% ≤ Sn ≤ 4.8 wt.%; 1.5 wt.% ≤ Zn ≤ 3.5 wt.%; 0.25 wt.% ≤ S ≤ 0.65 wt.%; 0.015 wt.% ≤ P ≤ 0.1 wt.%; and unavoidable impurities, with the rest being copper.

Description

Component for media-carrying gas or water pipes

The present invention relates to a component for media-carrying gas or water pipes, in particular fitting or fitting for drinking water pipes, wherein the component consists at least partially of a lead-free copper alloy. On metallic materials for use in components for water-bearing, especially drinking water leading trades, such as fittings, fittings, pipes, press connectors, roof gutters or gutters, special requirements must be met. In particular, in the case of standing in contact with drinking water components, the corrosion resistance should be mentioned. Especially copper-containing non-ferrous metal alloys such as bronze, brass or gunmetal also contain a certain amount of lead, because lead has the

Machinability of such alloys improved. In practice, nickel is also present in such alloys to increase the strength and corrosion resistance of the alloys. However, due to the toxicity of these metals, such materials must have a low tendency to migrate metal ions into the medium, i. a low release of ions of the alloy components to the medium. For this purpose, the materials used to protect consumers must comply with very narrow limits, which are regulated by the Drinking Water Ordinance. For this purpose, EP 1 798 298 A1 discloses a largely lead-free and nickel-free copper alloy which, in addition to copper and unavoidable impurities, contains 2% by weight to 4.5% by weight of silicon, 1% by weight to 15% by weight. Zinc, 0.05 wt .-% to 2 wt .-% manganese and optionally 0.05 wt .-% to 0.4 wt .-% of aluminum and

0.05 wt .-% to 2 wt .-% tin. The alloy described in EP 1 798 298 A1 exhibits an improved migration behavior for lead, nickel, copper and zinc ions compared to a conventional gunmetal. The alloy can be subjected to a heat treatment after casting in order to achieve a high proportion of α-mixed crystal and thus a particularly favorable migration behavior of the alloy.

For use in the drinking water installation is currently the gunmetal alloy

CuSn5Zn5Pb2 with contents of about 5 wt% tin and about 5 wt% zinc is widely used. This copper alloy has excellent corrosion resistance and can therefore be used in all water qualities within the drinking water supply. Alloys of this type are usually formed in the structure of a single phase and offer

- 1 -

CONFIRMATION COPY Her a high plastic deformability. However, it is precisely this plastic deformability that causes problems in machining machining. Single-phase copper materials tend to form a long chip. This type of chip inhibits the work flow during fully automated turning or drilling, and leads to heavy wear on the tool cutting edges. In order to be able to process the products nevertheless economically, lead is added to the alloys as a chip-breaking additive. Lead enables economical, fully automated mechanical processing.

Lead is practically insoluble in copper and has a low melting point. As a result, it is the last solidifying element in copper-tin alloys. This constitutional behavior leads to lead at the end of solidification in the microstructure in the form of evenly distributed, small, drop - shaped particles in between

Dendrite arms present. These fine, teardrop-shaped particles act as chipbreakers without affecting the original properties of the material. This is particularly evident in the corrosion resistance, since the lead particles are present as incoherent phases and thus can not interact with the surrounding matrix. Also, the uniform distribution of small, teardrop-shaped lead particles ensures that similar mechanical characteristics are consistently to be expected over a uniform cross section.

In the patent US 8,470,101 B2, a lead-free alloy is described, in addition to copper and unavoidable impurities from 0.1 wt .-% to 0.7 wt .-% sulfur, up to 8 wt .-% tin and up to 4 wt. -% zinc and in which the task of the lead over sulfur phases in the form of sulfide particles are met. In contrast to the element lead, however, these sulfides do not have the property of forming themselves inevitably at the end of solidification in the form of small, distributed phases. In the case of an unfavorably selected composition of the alloy described in US Pat. No. 8,470,101 B2, unfavorable sulfide formation in the microstructure may occur. As a result, the strength is reduced and there is a reduction of the mechanical characteristics. Furthermore, the sulfides described in US Pat. No. 8,470,101 B2 do not have high corrosion resistance. However, just for a use of such a sulfur-containing copper alloy in a drinking water installation, a corrosion-resistant matrix is necessary to ensure the longevity of the components. In copper alloys, nickel is able to increase both corrosion resistance and to improve the distribution of sulphide phases in the microstructure. However, high nickel contents lead to a high metal ion release into the drinking water and are therefore classified as hygienically questionable. The specified alloy range in US Pat. No. 8,470,101 B2 can not guarantee, over the entire scope described therein, that sufficiently high corrosion, strength, processing or hygiene properties are present. But especially these properties are essential for thin-walled drinking water-bearing components. Against this background, the present invention has the object to provide a lead-free copper alloy for the production of components for media-carrying gas or water pipes, compared to a conventional gunmetal alloy, such as CuSn5Zn5Pb2, a corrosion-resistant matrix, good strength properties with good handling properties, a high pressure tightness and improved migration behavior. In addition, the lead-free copper alloy should have a good casting behavior, eg. In sand or continuous casting.

These and other objects are achieved by a component for media-carrying gas or water pipes with the features of claim 1. Preferred embodiments of the component according to the invention are described in the dependent claims.

Surprisingly, according to the present invention, it has been recognized that a lead-free copper alloy containing as alloy components in% by weight, in addition to copper (Cu) and unavoidable impurities, 3.5% by weight of tin (Sn) .s, 4.8% by weight. , 1, 5 wt .-%. Zinc (Zn) <3.5 wt .-%, 0.25 wt .-% <sulfur (S) <0.65 wt .-% and 0.015 wt .-% < Phosphorus (P) .s 0.1 wt .-%, on contact with waters of different water qualities shows compared to standard brass (CuZn40Pb2) and dezincification resistant brass (CuZn36Pb2As) improved top layer formation, which has been proved, inter alia, by suitable hot aging experiments. Because of this improved overcoat, the lead-free copper alloy shows no dezincification or similar selective corrosion attack. Therefore, the lead-free copper alloy has improved corrosion resistance over the entire frame prescribed by the Drinking Water Ordinance (hereinafter referred to as "TWVO") Accordingly, the present invention preferably constitutes a component for media-carrying gas or water pipelines, particularly. in particular a fitting or a fitting for drinking water pipes, wherein the component consists at least partially of the lead-free copper alloy according to the invention.

It has been found that in the alloy used according to the invention, two sulfur-containing phases, copper sulfide and zinc sulfide, form in the microstructure as a function of the temperature and offset from one another. In order to achieve optimum machining properties through sulfide particles, they should be as round, finely divided and small as possible. This behavior is preferable to observe in the formation of copper sulfides. Zinc sulfides, however, tend to have a geometrically unfavorable shape. It has been recognized that the timing of phase formation, the type, number and distribution of the sulfur-containing particles are critical to machinability and mechanical properties such as elongation of the component. The formed sulfides, preferably as copper sulfide, offer the advantage, similar to the lead particles, of being present as incoherent phases. The tin content has an influence on the strength, corrosion resistance and on the phase distribution and, in the claimed range from 3.5% by weight to <4.8% by weight, achieves an optimally balanced, economical ratio of the properties described above. With a tin content of more than 4.8% by weight, the strength and corrosion resistance in the matrix continue to increase, but under normal cooling conditions in sand casting, the distribution of the sulfides becomes coarser and the size increases. At levels below 3.5% by weight of tin, there is insufficient corrosion inhibition. Also, because of the weak solid solution hardening necessary for the practice properties are not achieved. Although a high tensile strength can be achieved at levels above 4.8% by weight of tin, the elongation values of the material are reduced. Contents of well over 4.8 wt .-% tin lead to the formation of a structure which embrittlement and unfavorable effect on the processing.

It was found that with constant cooling conditions with increasing zinc content, the proportion of copper sulfide decreases and the proportion of zinc sulfide increases. With a zinc content of 1, 5 wt .-% to 3.5 wt .-%, particularly preferably with a zinc content in the range of 1, 8 wt .-% to 3.0 wt .-%, it can be ensured that in Walls of up to 6 mm a homogeneous distribution of smaller sulfides is favored. From this point of view, a zinc content of 2.0% by weight to 2.8% by weight is particularly preferred. The content of max. 3.5% by weight of zinc additionally ensures that partial corrosion phenomena can be avoided and high corrosion resistance can be achieved. The sulfur content of 0.25 wt .-% to 0.65 wt .-% determines the volume fraction of the sulfides with. From 0.25 wt .-% sulfur, an amount of sulfide particles is produced, which ensures sufficient machinability of the alloy. Sulfur content above 0.65 wt% sulfur can lead to the formation of undesirable coarse sulfide particles. In addition, due to the high proportion of sulfide particles, the load-transmitted cross section, ie the cross section of the component which absorbs stresses from the outside, can be reduced so much that a deterioration of the mechanical characteristics, such as elongation at break and the like, occurs. Further improved properties have been achieved with an alloy whose sulfur content is in the range of 0.3% to 0.6% by weight, in particular in the range of 0.35% to 0.55% by weight , Due to the alloy composition used according to the invention, the metal sulfides are present in such a sulfur content in the lead-free copper alloy as an incoherent, finely divided, disperse phase in the form of finely divided particles. This offers the advantage that any corrosion occurring only to a limited extent locally on these particles and not along coherent, larger, individual phases of the alloy structure takes place, as is the case, for example, with standard brass. Due to the small size of the particles no significant corrosive attack takes place. The proportion of phosphorus (P) in the lead-free copper alloy according to the invention is 0.015 wt .-% to 0.1 wt .-%. Below 0.015% by weight of phosphorus, there is no sufficient deoxidation of the melt, which has a negative effect on the phase formation of the alloy. On the other hand, with a phosphorus content of more than 0.1% by weight, the lead-free copper alloy tends to adversely affect the mechanical properties, such as reduced elongation at break. From these viewpoints, the weight proportion of phosphorus in the lead-free copper alloy is preferably in the range of 0.02 wt% to 0.08 wt%, more preferably in the range of 0.04 wt% to 0.06 wt%. -%.

As used herein, the term "lead-free copper alloy" means a copper alloy containing, in particular, lead as an unavoidable impurity in an amount of not more than 0.25 wt%, but preferably 0.09 wt%, more preferably not more than 0 In the alloy, the lead content is at most 0.25% by weight, preferably at most 0.09% by weight and particularly preferably at most less than or equal to 0.05% by weight Examination of lead migration according to standard DIN EN 15664-1, the alloy shows no signs of increased lead delivery in the first few weeks From the eighth week of testing, no significant lead migration is detected in the drinking water or lies within the range of the measuring accuracy of the method. The low lead content in the alloy used in the invention thus leads to a significant reduction of metal ion migration in drinking water, the low lead content has no negative effects on the chip breaking and thus on the machinability of the alloy used in the invention.

The nickel content in the alloy used in the invention is at most 0.4 wt .-%, preferably, the nickel content is at most 0.3 wt .-%. The addition of nickel increases the corrosion resistance of the alloy, without being in conflict with hygienic safety. Similar to lead, the values of nickel migration are far below the legally required limit when tested according to DIN EN 15664-1. Furthermore, it was found that an antimony content of at most 0.1% by weight with respect to the properties of the drinking water migration is not critical. The alloy may furthermore have an iron content of at most 0.3% by weight.

In preferred embodiments, the lead-free copper alloy may also contain fractions of the elements iron (Fe), zirconium (Zr) and / or boron (B) alone or in a combination of at least two of said elements as grain refiner. It is preferred that iron in a weight fraction of up to 0.3 wt .-%, zirconium in a weight fraction of up to 0.01 wt .-% and / or boron in a weight fraction of up to 0.01 wt. -% are contained in the lead-free copper alloy. Avoid the grain finer

Warm cracking and affect the mechanical properties, such. Tensile strength, material hardness and the like positive.

Preferably, the copper content of the lead-free copper alloy is at least 90% by weight, preferably more than 91% by weight.

According to the invention it is preferred if the sulfides of the lead-free copper alloy are homogeneously distributed in the structure. The number of sulfide particles should be high and their average size should be low in order to ensure uniform mechanical properties, good corrosion resistance, improved machinability and high pressure tightness over the entire microstructure. As the material of the sulfide particles, copper sulfide is preferable. because the presence of copper sulphide allows to substitute the volume of lead with a much lower content of sulfur.

In addition, it has proved to be very advantageous if the component according to the invention at least in sections has a wall thickness in the range of 0.5 mm to 6.0 mm, since the thin wall thickness leads to suitable cooling rates for the formation of copper sulfides. Furthermore, it is preferred if the entire component according to the invention has a wall thickness within the ranges of 0.5 mm to 4.0 mm, since a wall thickness in this range results in a particularly increased formation of the desired sulfide particles. A wall thickness below 0.5 mm could not have sufficient mechanical strength of the component according to the invention due to the small cross section. From these points of view, it is preferred that the component according to the invention at least partially has a wall thickness in the range of 1, 0 mm to 4.0 mm.

It may also be advantageous if at a wall thickness of less than 6 mm in the transverse section of the component according to the invention at least a proportion of 1, 6 area percent sulfide particles and / or a surface area factor ASP% is less than 1000. Such values result in sulfur sulfides being present as an incoherent, finely divided, disperse phase. As a result, deep trough and / or hole-shaped attacks, in particular corrosion attacks, are avoided on the components according to the invention. As used herein, the term "Area Property Code ASP%" is the mathematical description for the measure of the shape and location of a bell curve, which is a plot of the averages of the area classes (abscissa) in combination with the percentage distribution of the area

Sulfide particles in these surface classes (ordinate) results (see Fig. 1). The value of the surface content index ASP% is obtained by measuring the area of the respective particles, for example from an enlarged image of a micrograph, the percentage allocation of the particles detectable in the image in classes, the multiplication of the percentage values of the allocation with the mean value of the class and the formation of a large average from the resulting averages of the classes, with the large mean being taken as the "area key figure ASP%".

The alloy used in the invention has the excellent property of forming a topcoat very rapidly on the inner, water-wetted surface. The cover layer has a thickness of preferably at least 2 μm, more preferably of at least 3 μηπ, on. This covering layer increases the corrosion resistance and ensures the longevity of the components made of this material, since further corrosion is prevented. Migration from the material to the drinking water can only take place if corrosion processes take place in the material. Here, the top layer thus acts as a protective layer and limits the further metal delivery to the drinking water to a minimum. Although the copper content in the described alloy is higher than in conventional gunmetal alloys, such. As CuSnZn5Pb2, only a reduced copper metal release takes place. The good results of the test according to DIN EN 15664-1 prove that the composition of the alloy used according to the invention does not affect the quality of the drinking water over the entire claimed area without extensive restrictions in the workability. At the same time, compared to conventional gunmetal alloys, such as, for example, CuSnZn5Pb2, the alloy used according to the invention simultaneously has improved migration behavior in combination with excellent corrosion resistance.

In casting experiments could be proven that the components of the invention for media-leading gas or water pipes with conventional casting methods, such as sand, mold or continuous casting can be produced. The casting produced by such casting method can be machined well spanhebend.

As used herein, the term "component for media-carrying gas or drinking water lines" is to be understood in particular as those components which come into contact with a domestic installation pipe system with water, in particular with drinking water, whereby fitting and fittings of such domestic installation pipe systems are preferred according to the invention Such a fitting is to be mentioned in particular the connection piece known from EP 2 250 421 A1.

In the following, the present invention will be explained in more detail with reference to exemplary embodiments and tests carried out therewith as well as attached drawings. It should be understood that these examples are not to be construed as limiting the invention in any way. Unless otherwise specified, all percentages and percentages in the present application including the claims are based on the weight. Brief description of the drawings

In the drawings Fig. 1 shows exemplary plots of the areas of the particles versus the percentage

Distribution of particles in different size classes, which serve as a basis for determining the ASP% ("bell curve");

Fig. 2 is an overview of the test waters in the diagram according to Turner;

3 shows a diagram from which the attack depths of the dezincification in the standard brass in the hot aging test carried out emerge after 5 months of aging; 4 is an overview diagram showing the formation of the cover layer in the lead-free copper alloy used in the present invention after 5 months of aging;

5 is a photograph showing an example of a corrosion attack of standard brass in the hot aging test (based on Turner with a

Chloride content of 250 mg / l and a carbonate hardness of 5.5 ° dH);

6 shows a photograph of the alloy 2 used according to the invention, which shows an example of a continuous covering layer in the hot aging test (based on Turner with a chloride content of 250 mg / l and a carbonate hardness of 5.5

° dH);

Fig. 7 is a diagram of the thermal analysis of two melts with different zinc contents cast under the same conditions;

Fig. 8 is a Gefügeschliffbild a component of a melt, which was cast with a zinc content of about 3.9 wt .-%;

9 is a Gefügeschliffbild a component according to the invention from a melt, which was cast with a zinc content of about 2.4 wt .-%; 10 is a Gefügeschliffbild a component according to the invention from a melt, which has been slowly cooled; and FIG. 11 shows a micrograph of a component according to the invention from a melt which has been cooled rapidly.

Heat Exposure Tests for Corrosion Resistance of Alloys To evaluate the corrosion resistance of copper alloys, a hot aging test was developed that simulates the long-term corrosion behavior of alloys in a five-month trial period. The construction and execution of the test are based on the corrosion test established for decades and the Turner diagram ("The Influence of Water Composition on the Decinification of Duplex Brass Fittings", 1965) based thereon and the further investigations by Ladeburg ("Studies of dezincification phenomena Fittings made of copper alloys "; 1966). In these investigations, corrosion curves were recorded for the dezincification of the materials. The surface of the components was evaluated after a month of aging in different waters and conclusions about the dezincification resistance of the alloy were drawn.

FIG. 2 shows a Turner diagram for the test waters used in the hot aging test. In the diagram, the carbonate hardness (as a measure of water hardness) is plotted against the chloride ion content of the test water. The line, labeled "Turner Classic", represents the corrosion characteristic of dezincification developed by Turner ("The Influence of Water Composition on the Decini- zation of Duplex Brass Fittings", 1965). According to the usual interpretation of the world of corrosion, no dezincification takes place in the area below this line. Above this line, however, there is a very high risk that damage due to dezincification of the relevant component occurs. The points shown give an overview of the different test waters that were used in the described hot swapping test.

Inter alia, the following lead-free copper alloys were used for the heat aging tests carried out, the proportions of the components being given in the following Table 1 in% by weight: Table 1 :

For the production of test specimens, half cylinders with a wall thickness of 5 mm were cast from the alloys 1 and 2. Thereafter, the test specimens were on the outside by means of a turning to a roughness Rz of max. 25μιη machined and on the inside by means of a drilling with a through hole roughness Rz of max. 40 pm provided. This special surface treatment is intended to make it possible to compare the specimens with real components.

The surface of the specimens was cleaned with acetone. Subsequently, the test specimens were placed freely hanging in a test container. The test containers were then placed in a 90 ° C oven for five months with the test medium changed at seven-day intervals.

The test media were each 21 different test water with different pH values and carbonate hardness (the carbonate hardness (KH) is the proportion of calcium and magnesium ions, for the unit volume in the equivalent concentration

Hydrogencarbonationen is present), in addition, various levels of chloride ions and / or sulfate ions were set. The contents can be taken from Table 2:

Table 2:

After completion of the five-month test period, the test containers are removed from the oven, cooled to room temperature, taken the test specimens from the respective test containers, dried, cut open and the cut surface is examined by appropriate optical microscopy.

Alloys 1 and 2 showed over the entire area of the drinking water ordinance tested in hot aging an outstanding formation of a protective, adherent, closed covering layer required for copper alloys which has a thickness of at least 2 μm in the hot aging test and thus an improved covering layer with respect to a conventional lead-containing copper alloy based on a CuSnZn alloy (eg CuSn5Zn5Pb). Furthermore, this layer is almost free of disturbances or defects and thus unfolds its full protection by avoiding a deeper, local corrosion attack (see FIG. 4 and FIG. 6). In the diagram according to FIG. 3, the attack depths for standard brass (CuZn40Pb2) are shown after a five-month hot aging test for the respective test waters. In each case, a selective corrosion in the form of a dezincification, predominantly a zinc plating, appears. Clearly visible are attack depths, which in some cases suffice up to approx. 750 pm and thus illustrate a very poor corrosion resistance.

On the other hand, FIG. 4 shows the behavior of the cover layer formation of a lead-free copper alloy (alloy 1 and alloy 2) used according to the invention after a five-month hot aging test for the respective test waters. It turns out that it only comes to the formation of a protective topcoat. There is no visible selective corrosion attack. The thickness of the formed, adherent, protective cover layer is at least 4 pm. In Fig. 5 is a photograph of the microstructure in standard brass

(CuZn40Pb2) as a result of an exemplary corrosion attack after the five-month hot aging test, based on Turner, with a chloride content of 250 mg / l and a carbonate hardness of 5.5 ° dH. Here, an uneven, partially disturbed structure of the cover layer and the selective corrosion attack in the form of a

Entzinkung clearly recognizable.

In comparison, FIG. 6 shows a photograph of the microstructure of a result of the five-month hot aging test, based on Turner, with a chloride content of 250 mg / l and a carbonate hardness of 5.5 ° dH, based on an alloy component according to the invention 2 (Alloy 1 shows an analogous behavior) was performed. Compared to the microstructure shown in FIG. 4, the component according to the invention shows no selective corrosion attack after an identical heat aging test but a uniform, homogeneous structure of a protective, firmly adhering cover layer with a thickness of 4 μm to 23 μm.

In comparison to the standard brass, the alloy in the hot aging test carried out here, based on Turner, is free from selective corrosion attacks (eg dezincification and stress corrosion cracking) and almost all other corrosion phenomena. The experiments also show that sulfur sulfides as incoherent, finely divided, disperse phases show a significant corrosive advantage. This results from the avoidance of deep trough and / or hole-shaped attacks, which could lead to a significantly accelerated corrosion by a possible decrease in the pH and a concentration of the critical ingredients of the medium. In addition, no unfavorable corrosion-unfavorable, surface-moderately large phases are formed, which could be attacked as already described above by corrosion and then lead to a rapid failure of the component (see ß-phase in standard brass). Casting tests to determine the effects on sulfide formation

It could be determined from experiments that the alloy composition decisively influences the distribution, the form and the time of phase formation and that unfavorable contents have a negative effect on the phase and microstructure formation.

First, thermal tests were performed, which were subsequently verified by image analysis.

FIG. 7 shows a thermal analysis in a temperature-time diagram, by means of which thermal effects (for example release of latent heat) of metals can be detected which can arise in the case of solid-to-liquid transitions or solid state phase transformations. Plotted is the cooling temperature of the alloy and the first time derivative of the measurement signal against the time, which is described as the cooling rate. A change in the peak in the cooling rate curve corresponds to a thermal effect in the material. In the case of the lead-free alloy used in accordance with the invention, sulfide formation should be aimed for shortly before the end of solidification at low temperature, since in this way the sulfides, like the lead, are distributed more homogeneously in the microstructure.

Table 3

The cooling rate in Fig. 7 corresponds to the typical solidification process of a copper-tin alloy to 5 wt .-% tin in sand casting. Upon further comparison of the two curves it becomes clear that in the alloy 3 at approx. 400s an early thermal effect occurs during the proceeding solidification process, which results in a

Sulfide education is due. In the alloy 4 according to the invention, the sulfide formation takes place delayed, shortly before the end of the solidification. The fact that both samples have been cooled under identical conditions is underpinned by the further cooling rate profile of the samples, which is identical after phase formation. The varying timing of the phase formation is thus due to the different zinc content in the alloys. Early sulfide formation affects the sulfide form and distribution in the microstructure. Thus, the early formation of sulfide in alloy 3 leads to a heterogeneous, partial phase distribution, which adversely affects the mechanical characteristics such as elongation. In Fig. 8 (Alloy 3) and Fig. 9 (Alloy 4 used in the present invention), the differences in the structure of components made of melts according to Alloys 3 and 4 of Fig. 7 are seen with the different zinc contents. According to the present invention, the material composition is adjusted in a way that avoids premature sulfide formation and promotes homogeneous distribution.

Desweit was recognized that the cooling conditions of the melt to a component according to the invention, have an influence on the sulfide formation. A high cooling rate, which is preferred for a thin wall, results in a fine-meshed dendritic network with fine residual melt areas, from which a globular formation of the sulfides is supported. In this respect, rapid cooling is preferred according to the invention. 10 and 11 show micrographs of components according to the invention from an identical melt which has been cooled under varying conditions. In a rapid cooling, the micrograph in Fig. 11 shows a structure resulting in higher mechanical characteristics, e.g. Tensile strength, elongation at break and the like results.

To confirm this characteristic, the particles were analyzed by image analysis

Microstructures of specimens examined and characterized.

It has been shown that in the production of components according to the invention under the mentioned cooling conditions of a melt, an inventively together Alloyed, it can be achieved that at least partially present in a Gefügeschliff the casting at least 1, 8 area percent of the total area formed as sulfide particles. Among other things, the volume of sulfides and the surface area can be determined by means of this image analysis.

For the further determination of the sulfide particles different size classes are introduced (see Table 4). Subsequently, the particles are measured and assigned to the classes by percentage. Now the percentages are multiplied by the mean of the class. The resulting mean values of the classes are summarized to a large mean. The resulting value represents the surface area factor of sulfide particles ASP%. The alloys used according to the invention can be characterized by an area content index ASP% of less than 1000.

Table 4:

Hitherto, the present invention has been described with reference to Examples and Comparative Examples. However, it will be apparent to those skilled in the art that the is not limited to these examples, but the scope of the present invention from the appended claims.

Claims

claims

1. component for media-carrying gas or water pipes, in particular fitting or fitting for drinking water pipes, wherein the component consists at least partially of a lead-free copper alloy having the following alloy components in wt .-%:

3.5 wt% - £ Sn <4.8 wt%;

1.5% by weight of Zn <, 3.5% by weight;

0.25% by weight <S <0.65% by weight;

0.015 wt% <, P <, 0.1 wt%;

unavoidable impurities as well

to the rest of copper.

2. Component according to claim 1, characterized in that the sulfur content in the alloy 0.3 wt .-% £ S <0.60 wt .-%, in particular 0.35 wt .-% s s s 0.55

Wt .-%, is.

3. Component according to claim 1 or claim 2, characterized in that the zinc content in the alloy 2.0 wt .-% <Zn <, 3.0 wt .-% is.

4. Component according to one of the preceding claims, characterized in that the proportion of phosphorus in the alloy 0.02 wt .-% <P <0.08 wt .-%, in particular 0.04 wt .-% s P s 0 , 06 wt .-%, is.

5. Component according to one of the preceding claims, characterized in that the content of lead not more than 0.25 wt .-%, in particular not more than 0.09 wt .-% and preferably not more than 0.05 wt. %, is.

6. Component according to one of the preceding claims, characterized in that the content of nickel is not more than 0.4 wt .-%.

7. Component according to one of the preceding claims, characterized in that the content of antimony is not more than 0.1 wt .-%.

8. Component according to one of the preceding claims, characterized in that the content of iron, zirconium and / or boron alone or in combination of two or more of said elements is not more than 0.3 wt .-%.

9. Component according to one of the preceding claims, characterized in that copper is contained in the lead-free copper alloy in an amount of more than 90 wt .-%.

10. Component according to one of the preceding claims, characterized in that the component at least partially has a wall thickness in the range of 0.5 mm to 6.0 mm, preferably in the range of 1, 0 mm to 4.0 mm.

11. Component according to one of the preceding claims, characterized in that at a wall thickness below 6 mm in the transverse section of the component at least a proportion of 1, 6 area percent sulfide particles and / or a surface area factor ASP% is less than 1000.

12. Component according to one of claims 1 to 11, characterized in that it has a homogeneous, protective cover layer of at least 2 pm.

13. Component according to one of the preceding claims, characterized in that sulfur sulfides are present as incoherent, finely divided, disperse phase and thus deep multi- and / or hole-shaped attacks, in particular corrosion attacks, are avoided.

14. Component according to one of the preceding claims, characterized in that the

Material according to DIN EN 15664-2 after 16 weeks has no increased lead or nickel migration and complies with the specifications of DIN EN 15664-2.