METHOD FOR PRODUCING METALLIC COMPONENTS AND METALLIC COMPONENT PRODUCED THEREFOR

Description

[0001] The present invention relates to a method for producing components for media-carrying gas or water pipes, in particular fittings or valves for drinking water pipes, wherein the components are made at least partially of a lead-free copper alloy. Furthermore, the present invention relates to a component for media-carrying gas or water pipes, in particular a fitting or valve for drinking water pipes, produced by such a method.

[0002] Components for media-carrying gas or water pipes have a complex geometry. As used herein, a component is said to have a complex geometry if the component cannot be manufactured using a quasi-continuous forming process, such as the extrusion of rods or tubes and the rolling of strips.

[0003] Metallic materials used in components for water-carrying systems, especially those for drinking water, such as fittings, valves, pipes, press connectors, roof gutters, or drainage systems, are subject to special requirements. Corrosion resistance is particularly important for components that come into contact with drinking water. Gunmetal is one of the most important alloys with correspondingly high corrosion resistance for such components. However, it has the disadvantage that it is only hot-formable at very high cost.

[0004] The red brass alloy CuSn5Zn5Pb2, with contents of approximately 5 wt.% tin and approximately 5 wt.% zinc, is currently widely used in drinking water installations. This copper alloy exhibits excellent corrosion resistance and is therefore suitable for use in all water qualities within drinking water supplies. Components made from this alloy are cast and then machined to produce the final product. However, machining is problematic due to the alloy's plastic deformability, which leads to long chip formation. To ensure the products remain economically viable, lead is added to the alloys as a chip-breaking additive, enabling economical, fully automated machining.However, regulations regarding lead content in alloys used in drinking water installations have already been drastically tightened in the past. Further tightening of these regulations, even leading to a complete ban on lead in such alloys, is likely in the future.

[0005] Therefore, patent US 8,470,101 B2 describes a lead-free gunmetal alloy with high corrosion resistance. In addition to copper and unavoidable impurities, it consists of 0.1 wt.% to 0.7 wt.% sulfur, up to 8 wt.% tin, and up to 6 wt.% zinc. In this alloy, the lead acts as a chip breaker via sulfur phases in the form of sulfide particles. During casting, shrinkage cavities can form across the entire wall thickness of the component, causing porosity in the material, which in turn can lead to leaks in the component during machining. Furthermore, harmful constituents of the medium being transported can accumulate in the cavities, negatively impacting corrosion resistance. Other lead-free copper alloys are known from DE 10 2012 013817 A1 and DE 20 2016 101661 U1.A method for producing components for media-carrying gas or water pipes from a lead-free copper alloy is disclosed in the subsequently published EP 3 581 667 A1.

[0006] Against this background, the present invention is based on the object of providing a method for producing components for media-carrying gas or water pipes from a lead-free copper alloy that overcomes the disadvantages of the prior art. In particular, the components for media-carrying gas or water pipes obtained by the method according to the invention should exhibit high corrosion resistance and high pressure tightness, as well as be producible with minimal effort.

[0007] These and other objects are achieved by a manufacturing method for a component for media-carrying gas or water pipes having the features of claim 1 or by a component having the features of claim 9. Preferred embodiments of the method according to the invention or of the component according to the invention are described in the dependent claims.

[0008] According to the present invention, it was surprisingly discovered that a lead-free copper alloy which, as alloying components in wt.%, in addition to copper (Cu) and unavoidable impurities, wherein lead is present in an amount of not more than 0.25 wt.% and nickel with a nickel content of not more than 0.4 wt.% as unavoidable impurities, also comprises 3 wt.% to 8 wt.% tin (Sn), 1.3 wt.% to 6 wt.% zinc (Zn), 0.1 wt.% ≤ sulfur (S) ≤ 0.7 wt.% and optionally up to 0.2 wt.% phosphorus (P), optionally not more than 0.1 wt.% antimony; and optionally iron, zirconium and / or boron alone or in combination of two or more of the said elements not more than 0.3 wt.%, can be subjected to a hot pressing process.When a blank made of such an alloy is subjected to a hot-pressing process, grain refinement occurs primarily in the near-surface areas of the resulting workpiece, without requiring any further measures during the production of the copper alloy or the blank. This grain refinement in areas close to the surface of the component also has the advantage that the resulting component has increased surface hardness, which gives it high wear resistance, while the component as a whole exhibits good toughness properties due to the larger grain size within the component. This fine-grained alloy structure is surprisingly unaffected by incoherent areas and can therefore be excellently formed.Furthermore, the fine-grained alloy structure, particularly at the surface, leads to greater density of the component obtained according to the invention and to improved migration and corrosion properties. The hot-pressing process also enables near-net-shape production, which, starting from the surface, avoids volume-intensive machining of the material and thus the exposure of porosities, as well as a high amount of alloy waste.

[0009] Accordingly, the present invention relates to a method for producing components for media-carrying gas or water pipes, in particular a fitting or a valve for drinking water pipes, which consist at least partially of a copper alloy comprising the following alloy components in wt.%: 3.0 wt% < Sn ≤ 8 wt%; 1.3 wt% < Zn ≤ 6 wt%; 0.1 wt% ≤ S ≤ 0.7 wt%; optionally not more than 0.2 wt% phosphorus; and optionally not more than 0.1 wt% antimony; and optionally not more than 0.3 wt% iron, zirconium and / or boron alone or in combination of two or more of the said elements; and unavoidable impurities, with lead in an amount of not more than 0.25 wt% and nickel with a nickel content of not more than 0.4 wt% being included as unavoidable impurities, and the balance being copper; wherein the method comprises the steps of (a) melting the copper alloy; (b) producing extrusion blanks from the copper alloy; and (c) pressing the extrusion blanks at a suitable pressing temperature to form the components, wherein the pressing temperature is in a range from 750°C to 900°C and the extrusion blanks are heated to the pressing temperature before step (c) and held at the pressing temperature for a period of from 0.1 s to 60 min, and wherein the copper alloy in the component has a microstructure with an average grain size of less than 100 µm in a region close to the surface after the pressing process. Furthermore, the present invention lies in the provision of a component for media-carrying gas or water pipes, in particular a fitting or valve for drinking water pipes, which is produced according to the method according to the invention.

[0010] Furthermore, it was found that an optional antimony content of a maximum of 0.1 wt.% is uncritical with regard to the drinking water migration properties. The copper alloy can also optionally contain proportions of the elements iron (Fe), zirconium (Zr) and / or boron (B) alone or in a combination of at least two of the aforementioned elements as grain refiners. It is preferred that iron in a weight proportion of up to 0.3 wt.%, zirconium in a weight proportion of up to 0.01 wt.% and / or boron in a weight proportion of up to 0.01 wt.% are contained in the lead-free copper alloy. These grain refiners prevent hot cracking and have a positive effect on mechanical properties such as tensile strength, material hardness and the like.

[0011] As used herein, the term "component for media-carrying gas or drinking water pipes" refers in particular to components that come into contact with water, in particular drinking water, in a domestic installation piping system. Fittings and valves for such domestic installation piping systems are preferred according to the invention. The component for media-carrying gas or drinking water pipes can be a threaded or threadless part. This includes, in particular, connectors, connecting pieces, connecting angles, multiple distributors, T-pieces, wall T-pieces, wall angles, system transitions, transition pieces, and angled transition pieces, each of which can optionally have at least one thread. An example of such a component for media-carrying gas or drinking water pipes is, in particular, the connector known from EP 2 250 421 A1.

[0012] Furthermore, the term "near-surface region," as used herein, refers to the region of a component that lies at least 200 µm, preferably at least 100 µm, below the surface of the component. It is understood that these grain sizes are only present in sections of the component that have actually undergone deformation during the pressing step.

[0013] The extrusion blanks made of the copper alloy used in the method according to the invention can in particular be sections cut to length from bar material or hollow bar material of the copper alloy.

[0014] The sulfur content of the copper alloy used in the process according to the invention is preferably 0.2 wt.% to 0.65 wt.%. Due to the hot forming process, the sulfide particles align themselves to a particularly high extent in the forming direction at a sulfur content in this preferred range. With a sulfur content below 0.20 wt.%, the problem can arise that sufficient chip breaking can no longer be generated because the distances between the individual particles could become too large. This could result in burrs that must be removed in additional work steps. With a sulfur content greater than 0.65 wt.%, the reduced distances between the individual particles in the forming direction can lead to two effects: Firstly, the dislocations can no longer move as freely through the matrix, and material separation can occur at the sulfide particles during the hot forming process.Secondly, the component produced according to the invention may have lower strength, which may impair the durability of the component. Furthermore, a sulfur content above 0.65 wt.% sulfur may lead to a deterioration in the mechanical properties, such as the elongation at break. Further improved properties were achieved with an alloy whose sulfur content is in the range from 0.23 wt.% to 0.45 wt.%, in particular in the range from 0.25 wt.% to 0.35 wt.%. Due to the alloy composition used according to the invention, at such a sulfur content the metal sulfides are present in the lead-free copper alloy as an incoherent, finely distributed, dispersed phase in the form of finely distributed particles.This offers the advantage that any corrosion that may occur occurs only to a limited extent locally on these particles and not along interconnected, larger, individual phases of the alloy structure, as is the case with standard brass, for example. Due to the small size of the particles and the very closed microstructure (no cavities or similar) compared to a cast component, no significant corrosion attack occurs.

[0015] The zinc content of the copper alloy used in the process according to the invention is preferably 1.3 wt.% to 3.5 wt.%, with a zinc content in the range of 2.0 wt.% to 3.0 wt.% being particularly preferred. With a zinc content in this range, a homogeneous distribution of the particles in the alloy structure can be ensured. Furthermore, the zinc in this range improves the flowability of the material during the forming process. The zinc content of max. 3.5 wt.% additionally ensures that partial corrosion phenomena can be avoided and particularly high corrosion resistance can be achieved. Further improved results can be achieved with a zinc content of 1.5 wt.% to 3.3 wt.%, particularly preferably 2.0 wt.% to 3.0 wt.%.

[0016] The proportion of phosphorus (P) in the lead-free copper alloy is preferably at least 0.001 wt.%, in particular 0.015 wt.% to 0.1 wt.%. Below 0.015 wt.% phosphorus, it is possible that sufficient deoxidation of the melt may not occur, which could have a negative impact on the phase formation of the alloy. On the other hand, with a phosphorus content of more than 0.1 wt.%, the copper alloy tends to have adverse effects on the mechanical properties, such as reduced elongation at break. From this perspective, the weight proportion of phosphorus in the lead-free copper alloy is preferably in the range of 0.02 wt.% to 0.08 wt.%, particularly preferably in the range of 0.04 wt.% to 0.06 wt.%.

[0017] The tin content of the copper alloy used in the process according to the invention is preferably in a range from 3.0 wt.% to 4.8 wt.%, in particular in a range of 3.0 wt.% ≤ Sn ≤ 4.5 wt.%. In this range, a balanced, economical relationship between strength, corrosion resistance and phase distribution is achieved. With a tin content in the range from 3.0 wt.% to 4.8 wt.%, particularly good results are achieved with regard to elongation at break and corrosion resistance. Furthermore, with a tin content in the range from 3.0 wt.% to 4.8 wt.%, the process according to the invention can be carried out particularly economically with regard to forming speed and forming force. Dynamic strain aging may occur when carrying out the process according to the invention.This can occur particularly when the diffusion rate of the tin atoms during the forming process is equal to the rate of migration of the lattice defects. The occurrence of dynamic strain aging can be avoided when carrying out the process according to the invention by using suitable forming speeds and forming forces. Particularly good results can be achieved with a tin content of 3.5 wt.% to 4.0 wt.%. This preferred range therefore represents an ideal compromise between corrosion resistance and manufacturability.

[0018] Preferably, the copper content of the lead-free copper alloy is at least 90 wt.%, particularly preferably more than 92 wt.%. It has been shown that such a copper content allows for good processability combined with good corrosion resistance.

[0019] The copper alloy used in the method according to the invention is preferably a lead-free copper alloy. As used herein, the term "lead-free copper alloy" means a copper alloy that contains, in particular, lead as an unavoidable impurity in an amount of no more than 0.25 wt.%, but preferably no more than 0.10 wt.%, particularly preferably no more than 0.05 wt.%. The lead content in the alloy is a maximum of 0.25 wt.%, preferably a maximum of 0.10 wt.%, and particularly preferably a maximum of less than or equal to 0.05 wt.%. In a lead migration test according to DIN EN 15664-1, the alloy shows no signs of increased lead release in the first few weeks. Instead, from the eighth test week onwards, no significant lead migration into the drinking water can be detected or is within the range of the measurement accuracy of the method.The nickel content, as an unavoidable impurity in the alloy used in the invention, is a maximum of 0.4 wt.%, preferably a maximum of 0.3 wt.%. The addition of nickel increases the alloy's corrosion resistance without compromising its hygienic safety. Similar to lead, the nickel migration values in a test according to DIN EN 15664-1 are well below the legally required limit.

[0020] According to the invention, the pressing temperature in stage (c) is in a range from 750°C to 900°C, preferably in a range from 800°C to 880°C. Below a pressing temperature of 750°C, it cannot be reliably guaranteed that fine grain formation will occur. Furthermore, in this range, significantly higher forming forces are necessary to produce a component. This can lead to quality problems due to improperly formed areas and, on the other hand, the forming process is then no longer economical. Above a pressing temperature of 900°C, the first liquid phases form along the grain boundaries of the copper alloy, which leads to hot cracks and unfavorable grain boundary coatings in the material. In the preferred pressing temperature range of 800°C to 880°C, a particularly homogeneous, fine-grained microstructure is created and the risk of hot cracks is minimized.At pressing temperatures in the range of 815°C to 850°C, dynamic strain aging of the alloy can be particularly well avoided.

[0021] According to the invention, the blanks are heated to the pressing temperature before step (c) and held at the pressing temperature for a period of 0.1 s to 60 min, preferably from 2 s to 10 min. Holding the blanks at the pressing temperature for the specified period before pressing ensures that the entire blank has reached a homogeneous temperature, thus allowing a uniform pressing process to take place.

[0022] It may also prove advantageous if, after the hot-pressing process, the copper alloy in the component has a microstructure with an average grain size of less than 100 µm in a region close to the surface. This further improves the migration behavior and corrosion resistance of the components produced according to the invention. Preferably, after the hot-pressing process, the copper alloy in the component has a microstructure with an average grain size of 10 µm to 70 µm, in particular 20 µm to 60 µm, in the region close to the surface.

[0023] With regard to the component according to the invention, it has proven advantageous if the component according to the invention has a wall thickness in the range of 0.5 mm to 6.0 mm, at least in sections, since the thin wall thickness leads to cooling rates suitable for the formation of the copper sulfides that are favorable for migration behavior. Furthermore, it is preferred if the entire component according to the invention has a wall thickness within the stated ranges of 0.5 mm to 4.0 mm, since a wall thickness in this range leads to a particularly increased formation of the desired sulfide particles. A wall thickness of less than 0.5 mm might not provide sufficient mechanical strength for the component according to the invention due to the small cross-section. From these aspects, it is preferred that the component according to the invention has a wall thickness in the range of 1.0 mm to 4.0 mm, at least in sections.

[0024] In addition, the copper alloy in the component according to the invention has a microstructure with an average grain size of less than 100 µm in a region close to the surface. This contributes to very good migration behavior and high corrosion resistance of the components according to the invention. At the same time, a pressure-tight microstructure can be ensured. The pressure-tight microstructure results, among other things, from the closure of possible cavities and shrinkage due to the high pressures and temperatures introduced during drop forging. At the same time, the material is homogenized and possible differences in grain sizes are compensated for, which likewise improves the mechanical properties. After the hot pressing process, the copper alloy in the component preferably has a microstructure in the region close to the surface with an average grain size of 10 µm to 70 µm, in particular of 20 µm to 60 µm.

[0025] The part produced according to the invention has a pressure-tight structure with improvements in corrosion resistance. In contrast to a casting, in which surface erosion can begin at the base of a shrinkage cavity and may be intensified by concentrations, with the present production method, which includes a hot forming step, the surface attack is only noticeable starting from the surface. This also enables the construction of even more delicate components with increased mechanical requirements. Furthermore, possible segregations are homogenized during hot pressing, thus preventing concentration differences and possible tin depletion. This can prevent potential corrosion attack. The present invention will be explained in more detail below with reference to exemplary embodiments and tests conducted therewith, as well as the attached drawings.It is to be understood that these examples are not to be considered limiting the invention in any way. Unless otherwise stated, all percentages and proportions in this application, including the claims, are by weight. Short description of the drawings

[0026] Fig. 1 shows a micrograph of a formed test specimen made of alloy 1; Fig. 2 shows a micrograph of another formed test specimen made of alloy 1; Fig. 3 shows a photographic representation of an embodiment of a component according to the invention formed as a wall angle, made of alloy 2; Fig. 4 shows a photographic overview of the micrograph of the Fig. 3 shown component according to the invention, made of alloy 2; Fig. 5 an enlarged section of the Fig. 4shown overview of the component according to the invention, made of alloy 2; Fig. 6 a further enlarged section of the Fig. 4 shown overview of the component according to the invention, made of alloy 2; Fig. 7 a further enlarged section of the Fig. 4 shown overview of the component according to the invention, made of alloy 2; Fig. 8 a further enlarged section of the Fig. 4shown overview of the component according to the invention, made from alloy 2; Fig. 9 a photographic image of a cast and thus non-inventive component made from alloy 22 according to Table 5, which shows an example of a possible shrinkage cavity and the resulting deeper attack point in the artificial aging test (based on Turner with a chloride content of 250 mg / l and a carbonate hardness of 5.5 °dH); Fig. 10 a photographic image of a component made from alloy 22 according to Table 5, which shows an example of a homogeneous surface with a protective layer structure in the artificial aging test (based on Turner with a chloride content of 250 mg / l and a carbonate hardness of 5.5 °dH). Laboratory test on forming behavior

[0027] To simulate the forming behavior, drop forging tests were conducted on a laboratory scale. A tube measuring 23 mm x 8 mm served as the starting material. The semi-finished product was manufactured from a copper alloy using a continuous casting process. The component proportions in the copper alloy are given in Table 1 below in wt.%. Table 1: Alloy composition alloy Cu Zn Pb Sn P S Fe Ni Si Sb Al 1 94,2 1,4 0,02 3,87 0,04 0,42 0,01 0,01 0,01 0,01 0,01

[0028] The crescent-shaped test specimens were produced by cutting approximately 5 mm thick discs from the tube and splitting them in half. The resulting test specimens were placed, rounded side up, into the die. The die is a cube-shaped tool made of solid steel. It has a cross-shaped recess on the top, into which the test specimen was placed.

[0029] The test specimen held in the die was placed in a furnace for the heating time specified in Table 2 and then heated to the forming temperature also specified in Table 2. For forming, the test specimen held in the die was removed from the furnace, placed on an anvil, and formed by striking it with a sledgehammer with a mass of 5 kg. The number of hammer blows is given in Table 2. Due to the crescent-shaped geometry and the recess of the inner diameter of the tube, forming took place in every case. Following forming, the specimen was cooled with water to preserve and assess the resulting microstructure. The formed specimens were then metallographically prepared and assessed in the forming area. The grain sizes were determined using the line section method according to DIN EN ISO 2624.

[0030] The test conditions are summarized in Table 2 below: Table 2: Test conditions Sample number Forming temperature [°C] Heating time [min] Number of impacts (deformation) 1 800 90 2 2 800 30 1 3 830 75 1 4 830 75 1 5 860 65 1 6 860 65 - 7 800 60 - 8 800 60 - 9 830 60 - 10 830 60 - 11 860 60 - 12 860 60 - 13 600 60 - 14 600 60 - 15 600 60 1 16 600 60 1 17 700 60 1 18 700 60 1 19 700 60 - 20 700 60 - 21 950 60 1 22 950 60 1 23 950 60 1 24 950 60 -

[0031] The tests showed that very positive forming properties are evident in the range between 800 and 860°C, and the described fine grain formation occurs. At lower temperatures, hardly any more forming is possible. At higher temperatures, melting and reticulated sulfide agglomerates are visible. Figure 1A micrograph of a test specimen that was formed in a laboratory test at 830°C (sample 3) is shown. The formed microstructure exhibits a reduced average grain size of approximately 45 µm. The grain size of the test specimen before forming corresponds to that of a cast component, approximately 540 µm.

[0032] In Figure 2 (Sample 21) shows a micrograph of another formed test specimen, which was formed by a hammer blow at about 950°C. As Figure 2 As shown, the microstructure of the test specimen contains melted microstructure areas, which are due to the high forming temperature of approximately 950°C. The average grain size here is approximately 140 µm. The component in question exhibits hot cracks and unfavorably distributed sulfide particles within the microstructure. Therefore, this condition is not suitable for use in a real component. Investigation of a pressed component regarding the grain size distribution

[0033] To simulate the manufacturability of a pressed component in a real production process, some typical components of a drinking water installation were manufactured. Among other things, a wall bracket was produced, which is shown in the photographic representation according to Figure 3 is shown.

[0034] The copper alloy used to press the wall angle had the proportions of the components in wt.% given in Table 3 and Table 4 below. Table 3: Alloy composition alloy Cu Zn Pb Sn P S Fe Ni Si Sb Al 2 94,9 1,6 0,05 3,2 0,01 0,19 0,01 0,02 0,01 0,00 0,01 Table 4: Other alloy compositions alloy Cu Zn Pb Sn P S Fe Ni rest 3 95,1 1,5 0,01 3,1 0,004 0,26 0,01 0,01 0,03 4 95,1 1,6 0,01 3,0 0,04 0,25 0,02 0,01 0,04 5 95,2 1,6 0,01 2,9 0,03 0,24 0,02 0,01 0,03 6 95,1 1,6 0,01 3,0 0,02 0,25 0,01 0,01 0,04 7 93,6 1,6 0,02 4,5 0,01 0,24 0,02 0,01 0,04 8 93,8 1,6 0,01 4,0 0,03 0,43 0,01 0,01 0,04 9 95,4 1,3 0,01 3,0 0,01 0,16 0,01 0,01 0,03 10 95,5 1,3 0,01 3,0 0,01 0,14 0,01 0,01 0,03 11 94,5 1,3 0,01 3,9 0,02 0,15 0,01 0,00 0,03 12 94,7 1,2 0,01 3,9 0,01 0,15 0,01 0,00 0,03 13 94,3 1,5 0,01 3,9 0,03 0,15 0,01 0,00 0,04 14 93,9 1,5 0,02 4,1 0,04 0,46 0,01 0,00 0,03 15 93,9 1,5 0,02 4,0 0,02 0,46 0,01 0,00 0,03 16 94,0 1,5 0,02 4,0 0,02 0,46 0,01 0,00 0,02 17 92,4 3,1 0,02 4,0 0,04 0,43 0,02 0,00 0,03 18 92,4 3,0 0,02 4,0 0,04 0,43 0,02 0,00 0,03 19 94,9 1,6 0,01 3,0 0,05 0,44 0,01 0,00 0,02 20 95,3 1,3 0,01 2,9 0,02 0,46 0,01 0,00 0,03 21 95,4 1,2 0,01 2,9 0,01 0,45 0,01 0,00 0,02

[0035] For the production of the wall angle, continuous cast rods were made from the above-mentioned material, which were then cut to length into pressed blanks. The pressed blanks were then heated in a preheating furnace to a pressing temperature of approximately 830°C. From the preheating furnace, the heated blanks were then transferred via a chute into a preheated die, where the components were manufactured by closing the die. The resulting pressed parts were then cooled. In a final step, the components were finished and provided with a through hole and a thread.

[0036] In Figure 4 is an overview image of the microstructure of a section through the Figure 3 shown pressed wall angle, made of alloy 2. The different positions show critical areas of the fitting. In Figure 5(Position 1) shows the threaded area with a particularly fine-grained structure. The lower part of the image shows the inner side that comes into contact with the medium, particularly water, during the intended use of the component according to the invention. This is where the increased strength of the pressure-tight structure in the threaded area comes into play. This results in less deformation in the highly stressed threaded area and the component is better sealed. Figure 6 (Position 2) the inner area behind the thread tooth is made of Figure 4 to recognize.

[0037] The grain size increases at this point, resulting in greater toughness. Figure 7(Position 3) This type of microstructure is also shown in another area. This is located in the thread root at the transition to the component's taper. Here, the average grain size is approximately 25 µm. The increased surface hardness in this area, due to the low average grain size, is particularly advantageous for preventing erosive wear. Figure 8 (Position 4) illustrates the area where the component according to the invention has been drilled out for the transition to the outlet. Essentially, the alloy in the extrusion blank, i.e., prior to the extrusion process, is still in its original state, which can absorb any mechanical forces that may occur in the form of displacements. These can represent a particularly stressed area during on-site assembly, especially when aligning the wall angle for a fitting, where the tough core is a great advantage.

[0038] This shows that the material hardness in the deformed areas can generally be increased significantly. In the present example, in the collar area (see position 1 - Figure 3 ) the hardness can be significantly increased to a hardness of 78 HBW 2.5 / 62.5 according to DIN EN ISO 6506-1 compared to an identical wall angle made using a sand casting process.

[0039] For the other lead-free copper alloys from Table 4, components pressed according to the invention are also obtained with improved properties, such as the material hardness in the deformed areas. Determination of the corrosion behavior of a copper alloy in contact with an aqueous medium of components produced by the drop forging process

[0040] To assess corrosion resistance, components manufactured by drop forging were subjected to a hot aging test, which is described in the published patent application DE 10 2017 100896 A1.

[0041] For these artificial ageing tests, a lead-free copper alloy was used, among other materials, the proportions of the individual alloy components of which are given in Table 5 below in wt.%. Table 5: Alloy composition alloy Cu Zn Pb Sn P S Fe Ni Si Sb Al 22 94,78 1,66 0,00 3,27 0,01 0,20 0,01 0,02 0,00 0,01 0,00

[0042] To produce test specimens, wall angles 16 Rp ½ were manufactured from the alloy for construction site use. The components were mechanically processed under near-series conditions. For example, the surfaces were manufactured with comparable roughness depths. To obtain the test specimens, the components were then cut in half. The surface of the test specimens was cleaned with acetone. To generate a zero level for the measurement, the underside of the components was then painted and the unpainted test area was cleaned again. The test specimens were then placed freely suspended in a test container. The test containers were then placed in an oven at 90°C for five months, with the test medium being changed at intervals of seven days.

[0043] Twenty-one different aqueous test media or test waters with different pH values and acid capacities were used as test media. In addition, different chloride ion and / or sulfate ion contents were adjusted by adding sodium chloride and / or sodium sulfate. The contents can be found in Table 6. Table 6: Water number PH value Carbonate hardness in °dH Chloride in mg / l Sulfate in mg / l 1 9 0,5 10 - 2 9 0,5 100 - 3 9 0,5 250 - 4 9 0,5 1000 - 5 8 1,5 15 - 6 8 1,5 60 - 7 8 1,5 140 - 8 8 3,0 30 - 9 8 3,0 100 - 10 8 5,5 80 - 11 8 5,5 120 - 12 8 5,5 250 - 13 7 9,0 100 - 14 7 9,0 160 - 15 7 14,0 140 - 16 7 18,0 40 - 17 7 18,0 100 - 18 7 18,0 250 - 19 9 0,5 250 250 20 8 5,5 250 250 21 7 18,0 250 250

[0044] After completion of the five-month test period, the test containers are removed from the heating cabinet, cooled to room temperature, the test specimens are removed from the respective test containers, dried, cut open and the cut surface is examined under a light microscope after appropriate processing.

[0045] Compared to a component cast from alloy 22, a component hot-pressed from alloy 22 exhibits even better attack resistance. This is primarily due to the denser structure. Because there are no cavities or porosities, the medium attacks the surface of the hot-pressed component across the entire surface, quickly forming a protective, firmly adhering, closed cover layer. As with the cast component, this layer is virtually free of defects and thus provides complete protection by preventing attack at the base of any porosity.

[0046] In Fig. 9A conventionally cast component made of alloy 22 is shown with attacks that continue along pores into the depth, which was subjected to artificial aging at a carbonate hardness of 5.5 °dH and a chloride content of 250 mg / l. In comparison, in Fig. 10 A hot-pressed component made of alloy 22, which was tested under the same test conditions in the artificial ageing test with identical material composition, is shown. In contrast to the component made of Fig. 9 no pores. The medium therefore attacks the surface homogeneously and the attacks are therefore significantly reduced. The corrosion behavior is improved by hot pressing, as in Fig. 10 shown to have a positive impact.

[0047] The present invention has been described above with reference to examples and comparative examples. However, it will be apparent to those skilled in the art that the invention is not limited to these examples, but rather the scope of the present invention is determined from the appended claims.

Claims

1. Method for producing components for media-carrying gas or water pipes, in particular fittings or valves for drinking water pipes, which consist at least partly of a copper alloy, comprising the following alloy components in % by weight: 3.0% by weight ≤ Sn ≤ 8% by weight; 1.3% by weight ≤ Zn ≤ 6% by weight; 0.1% by weight ≤ S ≤ 0.7% by weight; optionally not more than 0.2% by weight of phosphorous; optionally not more than 0.1% by weight of antimony; and optionally iron, zirconium and / or boron alone or in combination of two or more of said elements, not more than 0.3% by weight; and unavoidable impurities, wherein lead in an amount of not more than 0.25% by weight and nickel with a nickel content of not more than 0.4% by weight are included as unavoidable impurities, and the remainder copper; wherein the method comprises the following steps: (a) melting the copper alloy; (b) producing press blanks from the copper alloy; and (c) pressing the press blanks at a suitable pressing temperature to form the components, wherein the pressing temperature is in the range of 750°C to 900°C and the press blanks are heated to the pressing temperature before step (c) and are held at the pressing temperature for a period of 0.1 s to 60 min, and wherein the copper alloy in the component after the pressing process has a microstructure with an average grain size of less than 100 µm in an area close to the surface.

2. Method according to claim 1, characterised in that the sulphur content in the alloy is 0.20% by weight ≤ S ≤ 0.65% by weight, in particular 0.23% by weight ≤ S ≤ 0.45% by weight, and preferably 0.25% by weight ≤ S ≤ 0.35% by weight.

3. Method according claim 1 or claim 2, characterised in that the zinc content in the alloy is 1.3% by weight ≤ Zn ≤ 3.5% by weight, preferably 1.5% by weight ≤ Zn ≤ 3.3% by weight, particularly preferably 2.0% by weight ≤ Zn ≤ 3.0% by weight.

4. Method according to any one of the preceding claims, characterised in that the phosphorous content in the alloy is 0.015% by weight ≤ P ≤ 0.1% by weight, in particular 0.02% by weight ≤ P ≤ 0.08% by weight, and preferably 0.04% by weight ≤ P ≤ 0.06% by weight.

5. Method according to any one of the preceding claims, characterised in that the tin content in the alloy is 3.0% by weight ≤ Sn ≤ 4.8% by weight, preferably 3.0% by weight to 4.5% by weight, particularly preferably 3.5% by weight to 4.0% by weight.

6. Method according to any one of the preceding claims, characterised in that copper is included in the lead-free copper alloy in an amount of more than 90% by weight.

7. Method according to any one of the preceding claims, characterised in that the pressing temperature in step (c) is in a range from 800°C to 880°C and particularly preferably in a range from 815°C to 850°C.

8. Method according to any one of the preceding claims, characterised in that the press blanks are heated to the pressing temperature before step (c) and held at the pressing temperature for a period of 2 s to 10 min.

9. Component for media-carrying gas or water pipes, in particular a fitting or valve for drinking water pipes, produced by a method according to any one of claims 1 to 8.

10. Component for media-carrying gas or water pipes according to claim 9, characterised in that the copper alloy in the component after the pressing process has a microstructure with an average grain size of less than 100 µm in an area close to the surface.

11. Component according to claim 9 or claim 10, characterised in that the component has a wall thickness in the range from 0.5 mm to 6.0 mm, preferably in the range from 1.0 mm to 4.0 mm, at least in sections.