Shaped part made of corrosion-resistant and machinable copper alloy

Abstract

To provide a copper alloy with low lead content, mechanical properties and corrosion resistance and its applications, a process for the manufacture of a molding, and a molding made therefrom.SOLUTION: The present invention provides a copper alloy that comprises Sn: 2 to 6%, Zn: 0 to 5%, S: 0.05 to 0.6%, Pb: less than 0.25%, Ni: less than 0.6%, Sb: less than 0.2%, and optionally phosphorus of up to 0.06 wt.%, B of up to 0.03 wt.%, and Zr of up to 0.03 wt.%, as well as unavoidable impurities, with the balance being Cu. The present invention also provides a process for the manufacture of moldings, involving at least one hot forming operation for copper alloys, and moldings made therefrom.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a copper alloy, its use, and a process for the manufacture of molded articles and articles formed therefrom. This relates to molded articles. [Background technology]

[0002] Water is a precious raw material and is essential for everyday use. When water is taken from the supply system, it is bacteriologically known that subsequent consumption may cause human disease. To achieve this, materials that come into direct contact with drinking water must be Copper is the most highly used general-purpose material with the highest quality and is used in industrial and technical applications in water-based systems. Copper is considered an essential material in surgical procedures. It is bacteriostatic and offers excellent corrosion resistance. Copper also exhibits excellent forming properties. Copper casting alloys are easy to cast and The material's high strength and toughness make it particularly suitable for plastomechanical molding.

[0003] However, it is precisely this plastic deformability that causes problems during machining. Here, homogeneous copper material tends to form long chips. This can disrupt the work sequence during fully automatic turning or drilling and can lead to severe wear on the tool cutting edges. Chip formation in copper is often the limiting factor in machining, so the workpiece This has a direct impact on economic efficiency.

[0004] Gunmetal belongs to the group of copper casting alloys and has good castability, optimum machinability and Characterized by a combination of high strength, corrosion resistance, and Particularly suitable for water-based systems such as fittings and sanitary technology. Common gunmetal alloys are It contains tin for increased corrosion resistance and zinc as a cost-effective alternative to copper. Heavy metals are added to make products made from gunmetal economically processable. Lead is added, which acts as a chip breaker for the alloy and allows it to be machined using CNC machines and This enables machining on a conventional automatic lathe.

[0005] When drinking water is not flowing through commercially available lead-containing fittings for an extended period of time, migration of metal ions can cause: Lead can be released into drinking water, and high levels of lead are considered a health hazard. For this reason, stricter requirements are being imposed around the world on the lead content of materials that come into contact with drinking water. In Germany, the statutory drinking water ordinance requires that lead content be less than 10% from January 12, 2013. There is increasing pressure worldwide to further reduce lead content in drinking water. For example, due to legal requirements in the United States, the lead content of copper alloys is limited to Regardless of the actual lead concentration in drinking water, it must not exceed an average lead content of 0.25%.

[0006] The ideal gunmetal is free of lead and other questionable substances and is made from the same or It has better efficiency and does not impair corrosion resistance, high mechanical strength and good processability.

[0007] Patent Document 1 describes a composition containing 4 to 6% by weight of tin, 4 to 6% by weight of zinc, and less than 0.25% by weight of The article describes a lead-free gunmetal alloy containing 100% lead. However, the functionality of these components is Subsequent mechanical processing to form a Noh mask is not taken into consideration. Without lead, the specific composition is uniform. They exhibit a uniform α-MK microstructure, which tends to form long chips and is economically machined. In addition, the casting process envisaged is not feasible for the production of molded parts. This requires a higher material input than conventional molding processes. Patent Document 6 describes a tin alloy containing 2 to 8% by weight of tin, 2.5 to 13% by weight of zinc, and 0. It contains less than 25% lead by weight, is suitable for hot pressing and has a homogeneous structure at the end of hot pressing. The paper describes a process for forming a lead-free gunmetal alloy that exhibits a slightly The blank to forming process allows economical production of formed parts with minimal material input. The process sequence is described, but the subsequent mechanical steps required to form the functional surface of the component are not included. The processing process is not taken into account. The chemical composition and subsequent hot forming result in a homogeneous microstructure. Again, in the absence of a chip breaker, long cuts are formed during machining. Debris forms and makes the part more difficult to machine economically.

[0008] Patent Document 7 discloses a Si-containing alloy containing relatively low but significant proportions of Mn, Al, and Zr. The present invention describes low-migration components made of relatively high amounts of copper alloys. is also disclosed in Patent Document 8. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] European Patent No. 2290114 [Patent Document 2] US Patent Application Publication No. 2012 / 0082588 [Patent Document 3] European Patent No. 2241643 [Patent Document 4] European Patent No. 3225707 [Patent Document 5] U.S. Patent No. 9,181,606 [Patent Document 6] European Patent No. 2872660 [Patent Document 7] European Patent No. 1801250 [Patent Document 8] International Publication No. 2007 / 068470 Summary of the Invention [Problem to be solved by the invention]

[0010] Despite the many copper alloys currently known in the prior art, on the one hand, there are On the one hand, the mechanical properties are controlled without the use of The goal of the project was to identify a gunmetal alloy that would allow for the forming process without compromising its corrosion resistance. It remains a challenge to develop alloys that exhibit good hot formability (i.e., no significant loss of mechanical properties). In particular, providing copper alloys that are preferably easy to machine has proven to be a particular challenge. There are.

[0011] Due to the above-mentioned shortcomings in the prior art, the object of the present invention is to provide a copper alloy that overcomes these shortcomings. In particular, copper alloys containing as few elements as possible are either lead-free or Essentially lead-free, eliminating expensive and / or difficult to mix metal components can.

[0012] This problem is solved by a copper alloy according to claim 1, its use according to claim 2 and a method according to claim 3. The solution is provided by the method for producing the moulded part according to the invention. Preferred designs are given in the dependent claims and in the following: Molded parts manufactured using the copper alloys described herein are also subject to stress. do. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Firstly, the invention will be described below with reference to the alloy according to the invention. The disclosed preferred designs include the disclosed uses, the disclosed manufacturing processes, and the disclosed molded parts. and should be considered the preferred design for these aspects of the invention. That is clear to one skilled in the art.

[0014] The present invention has chip breakers in its microstructure due to hot forming with low material input. Gunmetal alloy molded parts with high mechanical strength, high dimensional stability and high corrosion resistance These parts can be economically machined after hot pressing. The hot formable gunmetal alloy of the present invention has a microstructure that is chip-breaking. Elements such as Al, Si, Pb, Sb, Te, Se, C and Bi are added to form the does not require any additional repairs and can therefore be easily reused.

[0015] The invention therefore relates in particular to a process for forming a composite material comprising at least one hot forming process followed by machining. For the production of molded parts from Sn: 2-6% Zn: 0-5% S: 0.05-0.6% Pb: Less than 0.25 Ni: Less than 0.6 Sb: less than 0.2% % by weight, optionally up to 0.06% by weight of phosphorus, up to 0.003% by weight of B, Up to 0.03 wt. % Zr, including unavoidable impurities, the sum of the impurities being preferably 0.25 % by weight, the balance being Cu.

[0016] As mentioned above, in particular, the alloy of the present invention contains Al, Si, Sb, Te, Se, C and Bi. In the preferred embodiment, it is free of Pb.

[0017] The preferred contents of the alloying elements used according to the present invention are as follows, whereby Each of these is disclosed and claimed individually as well as each combination according to the invention (all of which are incorporated herein by reference). In all cases, percentages are by weight. Sn: 2 to 4%, and in some embodiments, 2% to less than 3.5%, such as 2 to 3.25%. Zn: 0 to 3%, in some embodiments, 0 to less than 1.5%, particularly 0.1% or more and less than 1.5%. Full S: 0.1 to 0.45%, in some embodiments, 0.1 to 0.2%, such as 0.1 to 0.2%. Less than 25% Ni: Less than 0.5%, 0% to 0.4%, such as 0 to 0.25%

[0018] The copper content in the alloy is preferably 88% by weight or more, more preferably 90% by weight or more. do.

[0019] The copper alloys disclosed herein unexpectedly overcome known shortcomings from the prior art. In particular, semi-finished and intermediate products made of copper alloys are very suitable for hot forming. Despite the frequent deterioration of strain hardening during hot forming (typically at temperatures between about 600 and 950 °C), At temperatures below 1000° C., the alloy according to the invention has excellent mechanical properties and does not exhibit a decrease in corrosion resistance (e.g. This allows the production of shaped parts (which can be further processed, for example, by machining).

[0020] Furthermore, the undesirable formation of particularly long chips is avoided, so that in this way (i.e. It has been shown that the parts formed (after hot forming) can also be further processed in an economical way. Therefore, despite the process involving hot forming, the alloy according to the invention does not contain any Pb or Si Although typical chip fracture components such as Cr, P, and H are omitted, the chip fracture components are still determined by the microstructure of the alloy. Therefore, the present invention provides a copper alloy having an excellent balance of desired properties. Thus, the reduction of other desirable properties of copper alloys and their suitability for use at high temperatures are provided. without fear of degrading the In combination, it is possible to produce shaped parts from this alloy, in particular by hot forming.

[0021] The alloy according to the invention can therefore be advantageously used for the production of moulded parts, The manufacturing process is sometimes combined with other machining processes, such as subsequent machining. In order to maintain the desirable properties of the copper alloys described herein, the individual alloys The gold components alone and their interactions allow for good and reproducible control of the alloy properties. become.

[0022] Tin acts in the alloy as a solid solution hardener, thus increasing the tensile strength, yield strength and It increases hardness but decreases elongation at break. Tin also increases corrosion resistance, and the higher the tin content, the greater the hardness. During the manufacture of the hot forming blank, strong tin is formed in the microstructure. It was recognized that segregation occurs, which leads to the formation of zone crystals during solidification. At the beginning, copper crystals with a relatively low tin content precipitate, and the rest of the melt is filled with copper with a higher tin content than the average content of the alloy. Departure from the stable copper-tin phase diagram results in the formation of a co-eutectoid. At room temperature, tin (α+δ) contents of more than 7% by weight may exist in the microstructure, but at equilibrium, This eutectoid is only formed at a maximum tin content of 15.8 wt.%. Since it crystallizes in the fz lattice, it can be easily deformed, but due to the enormous basic cell of 416 atoms, This makes the subsequent hot forming process more difficult. The materials can be removed by heat treatment at high temperature for a sufficient time (α+δ), but heat treatment requires a lot of energy. It requires energy.

[0023] There is also a risk of grain expansion of the microstructure during processing, which reduces elongation and 2-6 wt. % tin is particularly preferred. A tin content of about 2-4% by weight ensures high mechanical strength with high elongation and is suitable for casting. The formation of eutectoids (α+δ) during casting is avoided.

[0024] Sulfur is practically insoluble in solid copper, and the inherent properties of the material, such as corrosion resistance, are lost due to the addition of sulfur. Being insoluble in solid copper, sulfur reacts with copper in a manner similar to that of lead. This leads to constitutive behavior that affects the solidification process of tin alloys. However, unlike lead, At the end of solidification, sulfur is not present as an element in the microstructure, but is uniformly distributed in the microstructure. This phase exists in the form of intermetallic sulfur compounds. It was recognized that the alloy was brittle and therefore produced a chip failure mechanism.

[0025] The properties of sulfides affect the mechanical and plastic behavior of gunmetal materials. The sulfur content is determined by the amount of sulfide phase in the steel. From a sulfur content of more than 0.6 wt.%, α-Cu The stress transmitted to the matrix is ​​very strongly affected by sulfides, so hot pressing The process becomes extremely difficult. A sulfur content of 0.45% by weight to 0.5% by weight provides sufficient sulfide inclusions in the microstructure to provide a good chip surface. Generate fracture mechanisms and ensure hot forming process.

[0026] Zinc is added to the alloy as an economical substitute for copper. Between the zinc content and the sulfur content It has been recognized that the distribution of sulfide formation over time is closely related to the type of distribution. The higher the zinc content, the faster sulfide inclusions form in the microstructure during cast solidification. When the zinc content exceeds 5% by weight, the formation of sulfides occurs in the range of the solidification temperature of the gunmetal alloy. In this temperature range, a high percentage of molten material still exists within the cast structure. They are connected to each other in places.

[0027] High zinc content leads to the early formation of sulfides. These sulfides are heterogeneous and fine. Since the α-MK matrix is ​​concentrated in the fine structure, it is difficult to obtain the hot plate due to localized weakening of the α-MK matrix. The loess process becomes more difficult. At lower zinc contents, formation shifts to lower temperatures. In the previous residual melting zone, the sulfides are distributed uniformly and separately from each other. 0-5 wt. %, especially 0-3 wt. %, of zinc prevents the formation of sulfides at high temperatures. The investigation has shown that the copper alloy according to the invention, due to its specific composition, is suitable for the manufacturing process of moulded parts. and the process includes at least one hot forming step. The special composition of the alloy allows it to be easily processed after hot forming without problems, e.g. Further processing steps can be performed.

[0028] The thermoforming process according to the present invention can be, for example, a hot pressing process. Other hot forming processes known to the expert are also possible according to the invention. Before hot forming, such as in the topless process, the material is heated to 600°C to 950°C. However, the yield strength is low enough that hot forming processes can be used to plastically deform the gunmetal material. According to the present invention, the thermoforming can be carried out at any suitable temperature within the above temperature range, for example, at 700 to 800°C. The temperature can be adjusted according to the type of product to be molded, the molding speed, etc. Selected by the house.

[0029] Also, at a given temperature range, the atomic bonds of the sulfides weaken, so the formation of these superstructures It was recognized that in this temperature range, the phase loses its brittleness and becomes deformable. Immediately after formation, the α-MK matrix Dynamic recrystallization of the tin alloy takes place, removing the previously cast solid solutions of different tin concentrations, and the entire cross section is This ensures a uniform concentration, thus guaranteeing consistent mechanical and corrosion properties.

[0030] However, after the deformation process at room temperature, the sulfides are again distributed in the microstructure and become brittle. As a result, they act as chip breakers. Low sulfur content of 0.05% by weight or more Even in thermoformed parts with high content, the friction between the cutting chip and the tool changes over time. These altered friction conditions were found to cause tool vibrations during machining. The composite consists of a copper-containing α-MK matrix with embedded sulfides after hot pressing process. This is due to the heterogeneous microstructure of the chip. Shear bands are formed in the chip due to the vibration sliding. This results in lamellar and shear chips that are pulled away from the chip guide step of the tool. When ejected, they are destroyed during the further processing of the material. This prevents scrapping and enables economical processing.

[0031] To enable the hot pressing process envisaged in the present invention, the average grain size in the as-cast state is The measures necessary to ensure such an average grain size shall be determined by the experts. Grain refinement is achieved, for example, by the addition of chemical additives such as zirconium or boron. Use up to .005-0.03% by weight or use electromagnetic stirring, ultrasonic excitation, vibration, gas Other alternative processes for grain refinement, such as by means of injection or strong undercooling of the melt during casting, This is possible by using

[0032] The above copper alloys are particularly suitable for use in the manufacture of molded parts, the manufacture of which is carried out for at least 1 The copper alloys may also be used to manufacture formed parts, which include at least one hot forming operation. The hot forming operation is followed by additional processing steps such as subsequent machining. The process involves the manufacture of components, e.g. medium pipes such as gas or water pipes, e.g. Particularly suitable for the manufacture of connecting components such as joints. Hands are used to make and sell components of home plumbing systems such as pipes, fittings, end caps, and connectors. The basic process steps for the production of such molded parts are publicly available to experts. The specific copper alloys used in this context are well known and will not be described in detail here. The composition of the alloy means that there is no deterioration in mechanical properties and corrosion resistance even after hot forming, as described above. It is important to note that the obtained part is It was shown that the product could be subjected to other machining processes without any problems. Thus, machining is possible since undesirable formation of problems is avoided. It is possible to produce moulded parts in an economical way (in particular, good high temperature operating properties, Other desirable properties of copper alloys include inertness and corrosion resistance to substances they come into contact with, especially drinking water. In this connection, the component Pb, which is often considered necessary in the prior art, The use of Si, etc. is not necessary, yet the advantages of the invention described herein are achieved. Particular emphasis should be placed on this.

[0033] This unexpected advantage of the copper alloys described herein is in the manufacture of the molded parts mentioned above. This allows for economical use of the

[0034] example From lead-free gunmetal, formed parts for drinking water facilities are hot cut with subsequent machining. The alloy was produced in a fine-grained state by forming, which is due to the hot pressing process. It was shown that a chip breaker exists and that economical fully automated machining is possible.

Claims

1. A copper alloy suitable for the manufacture of formed parts by a process including at least one hot forming operation. The alloy has the following composition by weight: Sn: 2 to 6% Zn: 0 to 5% S: 0.05-0.6% Pb: less than 0.25% Ni: less than 0.6% Sb: less than 0.2% % by weight, optionally up to 0.06% by weight of phosphorus, up to 0.03% by weight of B, It is characterized in that it contains up to 0.03 wt. % Zr, unavoidable impurities, and the balance is Cu. A copper alloy characterized by its

2. of copper alloys for the manufacture of formed parts by a process including at least one hot forming operation The alloy has the following composition in weight percent: Sn: 2 to 6% Zn: 0 to 5% S: 0.05-0.6% Pb: less than 0.25% Ni: less than 0.6% Sb: less than 0.2% % by weight, optionally up to 0.06% by weight of phosphorus, up to 0.03% by weight of B, A copper alloy containing up to 0.03% by weight of Zr, unavoidable impurities, and the balance being Cu. The use of copper alloys.

3. 1. A process for producing a molded part from a copper alloy, the copper alloy comprising, in weight percent: The composition of, i.e. Sn: 2 to 6% Zn: 0 to 5% S: 0.05-0.6% Pb: less than 0.25% Ni: less than 0.6% Sb: less than 0.2% % by weight, optionally up to 0.06% by weight of phosphorus, up to 0.03% by weight of B, A copper alloy containing up to 0.03% by weight of Zr, unavoidable impurities, and the balance being Cu. wherein the process comprises: At least one hot forming operation of the copper alloy to produce a molded article. A process characterized by:

4. 10. The copper alloy of claim 1, wherein the sum of impurities does not exceed 0.25 wt. %. or the process according to claim 3.

5. The copper alloy according to any one of claims 1 to 4, wherein the tin content is 2 to 4 wt. %. For or process.

6. The copper alloy according to any one of claims 1 to 5, wherein the zinc content is 0 to 3% by weight. Or process.

7. 7. The composition according to claim 1, wherein the sulfur content is 0.1 to 0.45% by weight. Copper alloys, uses or processes.

8. The copper alloy does not contain any of the following elements: Al, Si, Sb, Te, Se, C, and Bi; and The copper alloy according to any one of claims 1 to 7, wherein the alloy is Pb-free. Or process.

9. The process further comprises at least one post-hot forming machining step. The process is suitable for producing shaped parts by at least one hot forming process. or the use comprises a machining process followed by hot forming.

9. The copper alloy, use or process according to any one of claims 1 to 8.

10. A copper alloy according to claim 1 or any one of claims 4 to 9, or a copper alloy according to claim 2 or and 4 to 9, or obtained by the use according to any one of claims 3 to 9.

2. A molded article obtained by the process described in claim 1.