Material made of a copper-zinc-silicon alloy and method for producing a component and method for producing a semi-finished product

Abstract

The invention relates to a material made of a copper-zinc-silicon alloy with the following composition: Cu: 67.0 to 72.0 wt.%, Si: 1.20 to 1.80 wt.%, Sn: 0.08 to 0.40 wt.%, P: 0.05 to 0.30 wt.%, Pb: optionally up to 0.10 wt.%, Fe: optionally up to 0.20 wt.%, Al: optionally up to 0.10 wt.%, Sb: optionally up to 0.10 wt.%, As: optionally up to 0.10 wt.%, with the remainder being Zn and unavoidable impurities, wherein the material has a structure which consists substantially of α-phase, optional β-phase, optional γ-phase and phosphide particles incorporated in the phases, and wherein the proportions of the β-phase and the γ-phase and the proportions of Si and P are selected such that the material satisfies the condition 185.092 - 5.72328∙([Beta]+[Gamma]) - 89.087∙[Si] - 354.137∙[P] + 2.8045∙([Beta]+[Gamma])∙[Si] + 236.598∙[Si]∙[P] < 60, wherein [Beta] represents the proportion of β-phase in vol.%, [Gamma] represents the proportion of γ-phase in vol.%, [Si] represents the proportion of silicon in wt.% and [P] represents the proportion of phosphorus in wt.%. The invention also relates to a method for producing a component and a method for producing a semi-finished product from a copper-zinc-silicon alloy.

Description

[0001] Wieland-Werke AG 89079 Ulm, 21.08.2025 Bt / Be

[0002] GP3432 - Foreign version

[0003] Description

[0004] Material made of a copper-zinc-silicon alloy and method for manufacturing a component and method for manufacturing a semi-finished product

[0005] The invention relates to a material made of a copper-zinc-silicon alloy for the production of media-carrying components, a method for producing a media-carrying component from a material made of a copper-zinc-silicon alloy, and a method for producing a semi-finished product from a material made of a copper-zinc-silicon alloy.

[0006] Components carrying media, such as fittings, screw connections, and valves, are frequently manufactured from brass semi-finished products using machining processes. To produce these semi-finished products, the alloy is cast, the casting is hot-pressed, and then cold-formed. In the past, the machinability of the resulting material was ensured by adding approximately 2 to 4 wt% lead to the alloy. CuZn36Pb2As is one example of such a material. Lead acts as a grain refiner, reduces ductility, breaks chips, and improves lubrication by forming thin parting lines. CuZn36Pb2As is dezincification-resistant according to ISO 6509. This good dezincification resistance is attributed to the fact that the α-phase of the material is inhibited by arsenic, while the dezincification-prone β-phase is removed by appropriate heat treatment (annealing) during the manufacturing process. Lead is harmful to health and the environment.Therefore, many countries have continuously reduced the limit values ​​for lead in copper alloys, and the replacement of lead-containing brass with lead-free, machinable copper alloys is being pursued. Limit values ​​are specified within the framework of EU directives, such as RoHS (Directive 2011 / 65 / EU), which sets an upper limit of 1000 ppm (0.1 wt%) of lead. Due to such regulatory requirements, there is a need for dezincification-resistant and easily machinable copper alloys with reduced lead content for components carrying media, especially drinking water.

[0007] As a lead-reduced, dezincification-resistant alternative, CuZn38As (CW511 L) already exists with a lead content of up to 0.2 wt.%. Due to the low lead content, the alloy is difficult to machine. Corrosion tests also show that the lead leachability of CuZn38As in drinking water only remains below the limit of 5 pg / l if the lead content of the alloy is less than 0.10 wt.%.

[0008] To ensure good machinability of the material even with lead contents of less than 0.1 wt.%, various alloying elements are proposed as an alternative to lead.

[0009] Numerous publications describe the use of bismuth (Bi) as an alternative to lead to improve machinability. To mitigate the problem of Bi film formation along grain boundaries and the associated susceptibility to stress and hot cracking, the addition of other elements is proposed. In this regard, particular reference is made to publications KR 10 0 555 854 B1, KR 10 2006 096 877 A, JP 2005290 475 A, JP 2014 122 427 A, and JP 2006 083443 A. Nevertheless, Bi is undesirable because, firstly, it is a metal with limited availability and, secondly, it leads to hot brittleness within the material cycles of copper alloys.

[0010] US patent 9,951,400 B1 discloses a copper-zinc-silicon alloy with 66 to 69 wt.% Cu, 1.53 to 2.0 wt.% Si, and the balance zinc. The alloy may also contain small amounts of Pb, P, Fe, Sn, Al, Ni, Co, As, Sb, Bi, Se, and S. The alloy typically contains at least 3 vol.% of non-a-phase components. This results in good machinability. Conversely, alloy compositions with a very low non-a-phase content exhibit poor machinability. The high ductility of the a-phase prevents chip breakage, leading to undesirably long chips. Satisfactory machinability can only be achieved with alloy compositions containing a significant volume fraction of non-a-phase. However, due to this significant volume fraction, such alloys exhibit suboptimal resistance to dezincification.Patent US 9,951,400 B1 does not provide any teaching on how to provide an alloy that exhibits both excellent resistance to dezincification and excellent machinability.

[0011] Some copper-zinc-silicon alloys exhibit corrosion when exposed to warm water with a high bicarbonate concentration. Therefore, a test with circulating warm water is performed on copper-zinc-silicon alloys used in the manufacture of components that carry fluids, as an additional criterion for corrosion resistance. This test uses water with a high Ks4.3 value, i.e., a high bicarbonate concentration.

[0012] The invention is therefore based on the objective of providing a material that exhibits both excellent resistance to dezincification and corrosion in circulating hot water with a high bicarbonate concentration, as well as excellent machinability despite a lead content limited to a maximum of 0.10 wt.%. The material is considered dezincification-resistant if, in a dezincification test according to DIN EN ISO 6509-1, it suffers a dezincification attack of less than 100 µm depth, preferably less than 50 µm depth. Furthermore, the material must be readily cold-formable and, at least in an intermediate state, also readily hot-formable. The invention is also based on the objective of providing a method for producing a dezincification- and corrosion-resistant component and a method for producing a readily machinable, dezincification- and corrosion-resistant semi-finished product.

[0013] The invention is described with respect to a material by the features of claim 1, with respect to a method for manufacturing a component by the features of claim 10, and with respect to a method for manufacturing a semi-finished product by the features of claim 11. The further referenced claims relate to advantageous embodiments and further developments of the invention.

[0014] A first aspect of the invention relates to a material made of a copper-zinc-silicon alloy with the following composition:

[0015] Cu: 67.0 to 72.0 wt.%,

[0016] Si: 1.20 to 1.80 wt.%,

[0017] Sn: 0.08 to 0.40 wt.%,

[0018] P: 0.05 to 0.30 wt.%,

[0019] Pb: optionally up to 0.10 wt%,

[0020] Fe: optionally up to 0.20 wt.%,

[0021] AI: optional up to 0.10 wt.%,

[0022] Sb: optional up to 0.10 wt.%,

[0023] As: optional up to 0.10 wt.%,

[0024] The remaining Zn and unavoidable impurities. The material has a microstructure consisting essentially of an α-phase, an optional β-phase, an optional γ-phase, and phosphide particles embedded in the phases. Within the scope of the invention, the phrase "consisting essentially of an α-phase, an optional β-phase, an optional γ-phase, and phosphide particles embedded in the phases" means that, in addition to the aforementioned components, the microstructure may contain further components that have formed due to unavoidable impurities or due to optional elements. Preferably, the proportion of these further components is less than 1 vol.%, more preferably less than 0.5 vol.%, and particularly less than 0.3 vol.% of the microstructure. The proportions of the β-phase and the γ-phase, as well as the proportions of Si and P, are selected such that the material meets condition (H).

[0025] 185.092 - 5.72328 ([Beta]+[Gamma]) - 89.087 [Si] -

[0026] 354.137 [P] + 2.8045 ([Beta]+[Gamma]) [Si] + 236.598-[Si]-[P] < 60 is satisfied, where [Beta] denotes the fraction of the β-phase in vol.%, [Gamma] the fraction of the γ-phase in vol.%, [Si] the fraction of silicon in wt.% and [P] the fraction of phosphorus in wt.%.

[0027] In light of the problem at hand, the invention is based on the premise that while an increasing volume fraction of the α-phase improves the dezincification resistance of the material, it also impairs its machinability. Phases that improve machinability in copper-zinc alloys, such as the β-phase or the γ-phase, increase the risk of dezincification and corrosion. Therefore, the lead used to improve machinability cannot simply be compensated for by increasing the proportions of the β-phase and γ-phase.

[0028] The invention proposes the targeted addition of silicon (Si) and phosphorus (P). Silicon strengthens the α-phase. This improves machinability by reducing the cold-forming capacity of the α-phase. Surprisingly, with increasing silicon content, the proportions of β-phase or γ-phase can be compensated for, so that sufficiently good machinability is achieved even with very low proportions of β-phase or γ-phase. Phosphorus improves dezincification resistance and forms phosphides with copper (and also with zinc), which promote chip breakage. The phosphides are particles that act as interfaces during machining, thus promoting chip breakage. Silicon facilitates the formation of shear bands. This is advantageous for machining, as these enable the formation of shear chips. Silicon and phosphorus thus condition the ductile and therefore unfavorable α-phase for machining in such a way that it is readily machinable. If the phosphorus content is below 0.05 wt.If the phosphorus content is below -%, not enough phosphides are formed. A phosphorus content above 0.30 wt% leads to cracking during hot forming.

[0029] The machinability of the material is determined by the combined selection of the parameters β-phase, γ-phase, Si, and P. For good machinability, the volume fractions of the β-phase ([Beta]) and the γ-phase ([Gamma]], as well as the weight fractions of Si ([Si]) and P ([P]), are chosen such that the alloy fulfills the condition H < 60, where the value H is defined as follows:

[0030] H = 185.092 - 5.72328 ([Beta]+[Gamma]) - 89.087 [Si] - 354.137 [P] + 2.8045 ([Beta]+[Gamma]) [Si] + 236.598 [Si] [P]

[0031] This relationship quantitatively describes the influence of the parameters β-phase, γ-phase, silicon content, and phosphorus content on the machinability of the material, as well as the interaction of these parameters with each other. For example, a low volume fraction of β-phase and γ-phase can be compensated for by a higher weight fraction of silicon within the alloy composition specification, and vice versa. Furthermore, the presence of no or only small amounts of β- and γ-phase is advantageous for the ductility of the material.

[0032] Furthermore, it is shown that materials made of CuZnSiP alloys with a Cu content of at least 67.0 wt.%, a Si content of at least 1.20 wt.%, and a P content of at least 0.05 wt.% are dezincification-resistant according to DIN EN 1264, even in the presence of β- or Y-phases, with a maximum dezincification depth of 100 pm, which is determined according to EN ISO 6509-1. Thus, within the scope of the first aspect of the invention, the dezincification resistance of the proposed material is ensured by its composition, namely by the minimum amounts of Cu, Si, and P.

[0033] Tin improves the corrosion resistance of materials in circulating hot water. The addition of tin (Sn) forms a better, and especially denser, protective layer on the material's surface. Tin has the property of accumulating on the surface, where it exists as an oxide. Generally, an alloying element leads to a compact oxide layer if the Pilling-Bedworth criterion is met, namely, "the density of the element's oxide is less than the density of the element, and the oxide is not porous." Tin fulfills this criterion. Silicon also fulfills the Pilling-Bedworth criterion and can form a dense silicate protective layer. However, silicate is attacked by carbonic acid. Tin oxide improves the compactness of the protective layer and thus prevents corrosion by carbonic acid. This improves corrosion resistance in hot water with a high bicarbonate concentration.At a tin content of less than 0.08 wt.%, the inhibitory effect is insufficient. At a tin content of more than 0.40 wt.%, further phases form in the microstructure, which can adversely affect dezincification resistance. The alloy contains up to 0.10 wt.% lead. Lead has a positive effect on machinability; however, its proportion in the alloy is regulated.

[0034] The optional presence of iron in the alloy results in a finer grain structure in the as-cast condition. This improves hot formability. The grain refinement is also present in the final state of the material, which has a positive effect on dezincification resistance. Preferably, at least 0.04 wt.% iron, and particularly preferably at least 0.05 wt.% iron, can be present in the alloy. If the amount of iron is too high, iron phosphides are formed, resulting in a lack of phosphorus, which acts as a dezincification inhibitor and is necessary for the formation of chip-breaking (Cu,Zn) phosphides. Fe-P compounds are less machinable than the (Cu,Zn)-P compounds that would otherwise form. Therefore, the proportion of iron is limited to 0.20 wt.%, preferably to 0.12 wt.%.

[0035] The alloy may optionally contain up to 0.10 wt% aluminum, preferably up to 0.05 wt% aluminum. Aluminum forms aluminum phosphides with phosphorus, which are undesirable. Therefore, the proportion of aluminum must not exceed 0.10 wt%, preferably not more than 0.05 wt%.

[0036] The alloy can optionally contain up to 0.10 wt% antimony and up to 0.10 wt% arsenic. The antimony and arsenic further improve dezincification resistance. Thus, the dezincification-inhibiting effect of phosphorus can be enhanced by arsenic and antimony.

[0037] The material can be in the form of a wrought material or a cast material.

[0038] The advantage of the proposed material lies in its ability to solve all three problems of the task: The material is in a state where it exhibits (i) excellent resistance to dezincification due to its minimum Cu, Si, and P content, (ii) very good resistance to corrosion in circulating, bicarbonate-containing warm water due to its Sn content, and (iii) excellent machinability despite a Pb content limited to a maximum of 0.10 wt.% due to the "H < 60" criterion. This combination of properties is achieved through the precise selection of the elements Cu, Si, P, and Sn, as well as through the specifically tailored microstructure. The material requires no further treatment to meet the requirements for use in components carrying fluids.

[0039] Preferably, the proportion of the β-phase in the microstructure of the material is at most 4 vol.%, particularly preferably at most 2 vol.% and ideally at most 1 vol.%.

[0040] Advantageously, the sum of the proportions of the β-phase and the γ-phase can be less than 6 vol%, preferably less than 5 vol%, particularly preferably less than 4 vol% and ideally less than 3 vol%.

[0041] In one embodiment of the invention, the proportion of the y-phase in the microstructure of the material can be at most 5 vol.%, preferably at most 3 vol.%, particularly preferably at most 2 vol.%, and ideally at most 1 vol.%. Limiting the proportion of the y-phase improves corrosion resistance in circulating hot water, especially in hard hot water, i.e., water with a high concentration of bicarbonate.

[0042] In a further embodiment of the invention, the copper content can be at least 68.0 wt.%, preferably at least 69.5 wt.%, and at most 71.5 wt.%, preferably at most 71.0 wt.%. With a copper content of at least 68.0 wt.%, the material is particularly resistant to dezincification. Limiting the copper content to at most 71.5% results in a particularly machinable alloy. In a further embodiment of the invention, the silicon content can be at least 1.30 wt.%, preferably at least 1.40 wt.%, and at most 1.70 wt.%, preferably at most 1.60 wt.%. With a silicon content of at least 1.30 wt.%, the material is particularly resistant to dezincification. With a silicon content of at least 1.40 wt.%, neither the β-phase nor the γ-phase is required to achieve sufficiently good machinability.

[0043] In a further embodiment of the invention, the tin content can be at least 0.15 wt.%, preferably at least 0.20 wt.%, and at most 0.35 wt.%, preferably at most 0.30 wt.%. With a tin content of at least 0.15 wt.%, corrosion resistance in circulating hot water is achieved particularly reliably. Limiting the tin content to a maximum of 0.35 wt.% inhibits the formation of undesirable phases in the microstructure of the material.

[0044] In a further embodiment of the invention, the phosphorus content can be at least 0.07 wt.%, preferably at least 0.10 wt.%, and at most 0.25 wt.%, preferably at most 0.20 wt.%, and particularly preferably at most 0.15 wt.%. With a phosphorus content of at least 0.07 wt.%, the alloy is highly resistant to dezincification even without arsenic and antimony. With a phosphorus content of at most 0.20 wt.%, the alloy can be hot-formed without difficulty. Particularly preferably, the phosphorus content is at least 0.10 wt.% and at most 0.14 wt.%.

[0045] In a further advantageous embodiment of the invention, the lead content can be at least 0.03 wt.%. Even a lead content of 0.03 wt.% improves the machinability of the material.

[0046] The material described above can be supplied as a wrought material in the form of wire, tube, rod, or profile semi-finished products. To produce such a semi-finished product, the copper-zinc-silicon alloy is melted and, preferably by continuous casting, cast into a finished product. After casting, heat treatment can optionally be carried out to homogenize the material. The cast product is then hot-formed, for example, by extrusion. After hot forming, a heat treatment at 400 °C to 580 °C for 1 to 10 hours can optionally be performed. Cold forming steps, particularly drawing processes, bring the material to its final dimensions in the desired semi-finished product shape.

[0047] The material described above can be used to manufacture a fluid-carrying component by machining. In particular, the material can be used in the form of a semi-finished product as described above. Alternatively, the material can be used in its as-cast state, resulting in a cast component. Due to its special chemical composition, the material is resistant to dezincification and corrosion in circulating hot water even without further treatment, especially without subsequent heat treatment.

[0048] Regarding further technical features and advantages of the material according to the invention, explicit reference is hereby made to the explanations in connection with the exemplary embodiments and comparative examples.

[0049] A second aspect of the invention relates to a method for manufacturing a component from a copper-zinc-silicon alloy. The method comprises the following steps: a) Melting a copper-zinc-silicon alloy and casting a product from a copper-zinc-silicon alloy with the following composition:

[0050] Cu: 64.0 to 72.0 wt.%, Si: 0.40 to 1.80 wt.%,

[0051] Sn: 0.08 to 0.40 wt.%,

[0052] P: 0.05 to 0.30 wt.%,

[0053] Pb: optionally up to 0.10 wt%,

[0054] Fe: optionally up to 0.20 wt.%,

[0055] AI: optionally up to 0.10 wt.%, preferably up to 0.05 wt.%,

[0056] Sb: optional up to 0.10 wt.%,

[0057] As: optional up to 0.10 wt.%,

[0058] Residual Zn and unavoidable impurities, b) optional heat treatment of the casting, c) optional hot forming of the casting and optional further forming steps, d) resulting in a material having a microstructure consisting essentially of α-phase, optional β-phase, optional γ-phase and phosphide particles embedded in the phases, wherein the proportions of β-phase and γ-phase and the proportions of Si and P are chosen such that the material meets condition (H)

[0059] 185.092 - 5.72328 ([Beta]+[Gamma]) - 89.087 [Si] -

[0060] 354.137 [P] + 2.8045 ([Beta]+[Gamma]) [Si] + 236.598 [Si] [P] < 60 is satisfied, where [Beta] denotes the proportion of the β-phase in vol.%, [Gamma] the proportion of the γ-phase in vol.%, [Si] the proportion of silicon in wt.% and [P] the proportion of phosphorus in wt.%, e) Machining of the material to obtain a component, f) Heat treatment of the component such that the proportion of the β-phase in the microstructure of the material is at most 4 vol.% and the proportion of the γ-phase in the microstructure of the material is at most 5 vol.%.

[0061] Within the scope of the invention, the fact that the microstructure of the material "consists essentially of an α-phase, an optional β-phase, an optional γ-phase, and phosphide particles embedded in the phases" means that, in addition to the aforementioned components, the microstructure may contain further components that form due to unavoidable impurities or due to optional elements. Preferably, the proportion of these further components is less than 1 vol.%, more preferably less than 0.5 vol.%, and particularly less than 0.3 vol.% of the microstructure.

[0062] The material can be in the form of a wrought material or a cast material in step e).

[0063] As described above in connection with the material according to the invention, the machinability of the material is ensured in the proposed method by selecting the proportions of the β-phase and the γ-phase as well as the proportions of Si and P such that the material fulfills the condition “H < 60” immediately before process step e), wherein the value H is defined as follows:

[0064] H = 185.092 - 5.72328 ([Beta]+[Gamma]) - 89.087 [Si] - 354.137 [P] + 2.8045 ([Beta]+[Gamma]) [Si] + 236.598-[Si]-[P]

[0065] This relationship quantitatively describes the influence of the parameters β-phase, γ-phase, silicon content, and phosphorus content on the machinability of the material, as well as the interaction of these parameters with each other. For example, a low proportion of β-phase and γ-phase can be compensated for by a higher proportion of silicon within the specification of the alloy composition, and vice versa.

[0066] Within the framework of this second aspect of the invention, the

[0067] The dezincification resistance of the material in its final state, and thus the dezincification resistance of the component, is ensured by the heat treatment of the component in step f). The heat treatment converts the β-phase into the dezincification-resistant α-phase. The heat treatment is carried out such that the proportion of the β-phase in the microstructure of the material is at most 4 vol.%, preferably at most 2 vol.%. The heat treatment is preferably carried out in a temperature range between 350 °C and 500 °C for a duration of 1 to 12 hours, particularly preferably between 420 °C and 480 °C for a duration of 3 to 12 hours.

[0068] Corrosion resistance in circulating hot water is achieved by a tin content of at least 0.08 wt.% and by limiting the proportion of the y-phase in the microstructure to a maximum of 5 vol.%. Preferably, the proportion of the y-phase in the microstructure is a maximum of 4 vol.%, and particularly preferably a maximum of 2 vol.%.

[0069] The advantage of the proposed manufacturing process according to the second aspect is that the dezincification resistance of the material is only adjusted after machining. Therefore, the material used for machining in step e) does not necessarily have to be in a dezincification-resistant state, while the material in the final state, i.e., after step f), no longer needs to be easily machinable. This subsequent adjustment of the dezincification resistance thus allows the alloy composition and the microstructure constituents to be selected within a very wide range before machining. More degrees of freedom are available than in the first aspect of the invention described above. In particular, these parameters can be adjusted so that the material exhibits optimal machinability at low metal costs.The proportions of copper and silicon can be selected within a wider range than in the material according to the first aspect of the invention. A third aspect of the invention relates to a method for producing a semi-finished product from a copper-zinc-silicon alloy. The method comprises the following steps: a) Melting and casting a casting product from a copper-zinc-silicon alloy with the following composition:

[0070] Cu: 64.0 to 72.0 wt.%,

[0071] Si: 0.40 to 1.80 wt.%, preferably up to 1.20 wt.%

[0072] Sn: 0.08 to 0.40 wt.%,

[0073] P: 0.05 to 0.30 wt.%,

[0074] Pb: optionally up to 0.10 wt%,

[0075] Fe: optionally up to 0.20 wt.%,

[0076] AI: optionally up to 0.10 wt.%, preferably up to 0.05 wt.%,

[0077] Sb: optional up to 0.10 wt.%,

[0078] As: optional up to 0.10 wt.%,

[0079] Residual zinc and unavoidable impurities, b) optional heat treatment of the casting, c) hot forming and / or cold forming of the casting, whereby a semi-finished product is obtained from a material having a microstructure consisting essentially of an α-phase, an optional β-phase, an optional γ-phase, and phosphide particles embedded in the phases. The semi-finished product has a continuous cross-section along its axis and is preferably wire-shaped, rod-shaped, tubular, or profile-shaped. The process comprises at least one heat treatment of the semi-finished product after hot forming or after cold forming, wherein the heat treatment is carried out in the temperature range between 450 °C and 550 °C, preferably between 490 °C and 530 °C, particularly preferably between 505 °C and 525 °C, for 2 to 8 hours, such that the proportion of the optional β-phase in the microstructure of the material of the semi-finished product is at most 4 vol.The proportion of the optional γ-phase in the microstructure of the material is at most 5 vol.%. In this process according to the third aspect of the invention, both the dezincification resistance and the machinability of the material are adjusted by heat treatment in the temperature range between 450 °C and 550 °C in combination with the selection of alloying elements. This heat treatment forms additional fine phosphide particles in the α-phase, which promotes machinability, in particular chip breakage. At the same time, this heat treatment ensures the dezincification resistance of the material in its final state by converting the β-phase into the dezincification-resistant α-phase. The heat treatment is carried out such that the proportion of the β-phase in the microstructure of the material is at most 4 vol.%, preferably at most 2 vol.%, and the proportion of the γ-phase in the microstructure of the material is at most 5 vol.%, preferably at most 3 vol.%.Surprisingly, it has been shown that while heat treatment reduces the proportion of the β-phase, which is favorable for machinability, in the microstructure, this reduction is compensated for by the formation of additional phosphide particles in the α-phase. Contrary to expectations, the annealed state, which contains very little β-phase, is therefore no less machinable than the unannealed state, which contains significantly more β-phase.

[0080] Advantageously, the sum of the proportions of the β-phase and the γ-phase can be less than 6 vol%, preferably less than 5 vol%, particularly preferably less than 4 vol% and ideally less than 3 vol%.

[0081] As explained in connection with the first aspect of the invention, the tin content in the alloy improves the corrosion resistance of the material in circulating hot water.

[0082] The advantage of the proposed manufacturing method according to the third aspect of the invention is that both the dezincification resistance and the machinability of the material are adjusted by heat treatment in the temperature range between 450 °C and 550 °C, and thus during the production of the semi-finished product. In contrast to the method according to the second aspect of the invention, the semi-finished product already fulfills these two requirements.

[0083] In a particular embodiment of this third aspect of the invention, the material can have a microstructure after heat treatment in which, over an area of ​​21000 pm 2The material contains 30 to 160 phosphide particles with an equivalent diameter of 0.5 to 1 pm, 10 to 150 phosphide particles with an equivalent diameter of 1 to 2 pm, and a maximum of 40 phosphide particles with an equivalent diameter of more than 2 pm. This results in particularly favorable machining properties.

[0084] It is particularly advantageous if an area of ​​21000 pm is used. 2 at least 70, preferably at least 100 phosphide particles with an equivalent diameter of 0.5 to 1 pm are present.

[0085] Preferably, within the scope of the second and third aspects of the invention, the Cu content of the copper-zinc-silicon alloy can be at least 64.5 wt.%, particularly preferably at least 65.0 wt.% and at most 69.0 wt.%, particularly preferably at most 68.5 wt.%.

[0086] Furthermore, within the scope of the second and third aspects of the invention, the Si content of the copper-zinc-silicon alloy can preferably be at least 0.50 wt.%, particularly preferably at least 0.55 wt.%, and at most 0.95 wt.%, particularly preferably at most 0.90 wt.%.

[0087] Within the framework of the second and third aspects, the material preferably fulfills the condition.

[0088] 0.36 < ([Zn]+10 [Si]+2.3 [Sn]) / ([Cu]+[Zn]+10 [Si]+2.3 [Sn]) < 0.39 where [Cu] denotes the proportion of Cu in wt.%, [Zn] the proportion of Zn in wt.%, [Si] the proportion of silicon in wt.%, and [Sn] the proportion of Sn in wt.%. The term ([Zn]+10 [Si]+2.3-[Sn]) / ([Cu]+[Zn]+10 [Si]+2.3 [Sn]) is used in this invention as the zinc equivalent Zn eqThis is indicated by the zinc equivalent value. If the zinc equivalent is 0.36 or less, the material is not sufficiently machinable. If the zinc equivalent is 0.39 or greater, the desired upper limit of the β-phase cannot be reliably maintained during the heat treatment of the component in step f) or during the heat treatment of the semi-finished product. In other words, the material cannot then be annealed to be "β-free".

[0089] In one embodiment of the second and third aspects of the invention, the copper content of the copper-zinc-silicon alloy can be at least 64.5 wt.%, preferably at least 65.0 wt.% and at most 66.5 wt.%, preferably at most 66.0 wt.%, and the silicon content can be at least 0.50 wt.%, preferably at least 0.55 wt.% and at most 0.70 wt.%, preferably at most 0.65 wt.%. This ensures that the maximum value of the β-phase is reliably achieved during the heat treatment of the component or semi-finished product, while simultaneously providing very favorable machinability.

[0090] In an alternative embodiment of the second and third aspects of the invention, the copper content of the copper-zinc-silicon alloy can be at least 67.0 wt.%, preferably at least 67.5 wt.% and at most 69.0 wt.%, preferably at most 68.5 wt.%, and the silicon content can be at least 0.75 wt.%, preferably at least 0.80 wt.% and at most 0.95 wt.%, preferably at most 0.90 wt.%. This ensures that the maximum value of the β-phase is reliably achieved during the heat treatment of the component or semi-finished product, while simultaneously providing very favorable machinability.

[0091] In a further embodiment of the second and third aspects of the invention, the tin content can be at least 0.15 wt.%, preferably at least 0.20 wt.%, and at most 0.35 wt.%, preferably at most 0.30 wt.%. With a tin content of at least 0.15 wt.%, corrosion resistance in circulating hot water is achieved particularly reliably. Limiting the tin content to a maximum of 0.35 wt.% inhibits the formation of undesirable phases in the microstructure of the material.

[0092] In a further embodiment of the second and third aspects of the invention, the phosphorus content can be at least 0.07 wt.%, preferably at least 0.10 wt.%, and at most 0.25 wt.%. With a phosphorus content of at least 0.07 wt.%, the alloy is highly resistant to dezincification even without arsenic and antimony. With a phosphorus content of at most 0.25 wt.%, the alloy can be hot-formed without difficulty. In a further particular embodiment of the second aspect of the invention, the phosphorus content is preferably at least 0.10 wt.% and at most 0.20 wt.%, particularly preferably at most 0.15 wt.%. In a further particular embodiment of the third aspect of the invention, the phosphorus content can be at least 0.12 wt.%, particularly preferably at least 0.15 wt.%, and at most 0.23 wt.%.Phosphorus forms brittle phosphides in the alloy, which particularly promote chip breakage and, in combination with a Si content of more than 0.4 wt.%, lead to short chips.

[0093] In a further advantageous embodiment of the second and third aspects of the invention, the lead content can be at least 0.03 wt.%. A lead content of at least 0.03 wt.% improves the machinability of the alloy. With regard to the optional alloying elements Fe, Al, Sb, and As and their technical effects, explicit reference is made hereto to the explanations relating to the copper-zinc-silicon alloy material described above according to the first aspect of the invention. The statements made therein can be applied to the copper-zinc-silicon alloy used in the processes described above for manufacturing a component according to the second aspect of the invention or for manufacturing a semi-finished product according to the third aspect of the invention.

[0094] Regarding further technical features and advantages of the manufacturing processes according to the invention, explicit reference is hereby made to the explanations in connection with the exemplary embodiments and comparative examples.

[0095] The invention is explained in more detail using exemplary embodiments and comparative examples.

[0096] Samples 1 to 47 were melted in an induction furnace and then cast. The composition of the samples is documented in Tables 1 to 3. Sample 30 represents the lead-containing reference alloy CuZn36Pb2As. Sample 31 represents the lead-reduced alloy CuZn38As (CW511 L) with a lead content of 0.2 wt.%. The remaining samples each have a lead content of less than 0.1 wt.%.

[0097] Samples No. 1 to No. 10 and No. 19 to No. 33 were milled after casting, homogenized for 1 hour, and then hot-rolled at 800 °C. After hot-rolling, samples No. 10 were milled and then cold-formed with a degree of deformation of 20%. Sample No. 2, which is identical in composition to Sample No. 1, as well as Samples No. 10, No. 30, No. 31, and No. 33, were annealed at 550 °C for 8 hours after hot-forming and before cold-forming. Samples No. 11 to No. 16 were hot-formed by extrusion at 690 °C to 730 °C. After hot-forming, Samples No. 11 to No. 16 were annealed at 520 °C for 4 hours. Samples 11 to 16 were then pickled and subsequently cold-formed with a degree of deformation of 8%. Sample 16 was then annealed at 750 °C for 2 hours.

[0098] Samples No. 3 to No. 9 were divided after cold forming, and a portion of the samples were additionally annealed at 450 °C for 8 hours – in accordance with process step f) of the above-described process for manufacturing a component – ​​to reduce the proportion of the β-phase. These annealed samples are documented in Table 2 as samples No. 19 to No. 25 (in the same order as samples No. 3 to No. 9).

[0099] At the final state, the yield strength R was determined in each case. p 0.2, the tensile strength R m and the elongation at break from the tensile test and the electrical conductivity are determined.

[0100] Longitudinal sections of the samples were examined using light microscopy. The surface area fractions of the α-phase, β-phase, γ-phase, and phosphide particles corresponding to their volume fractions, as well as the grain size of the α-phase, were determined.

[0101] The dezincification resistance of the samples was determined according to EN ISO 6509-1. The maximum depth of dezincification attack is given as a measure of dezincification resistance.

[0102] Machinability was determined by a planing test. An indexable insert with a contour that promotes chip breakage was used. The depth of cut was 125 µm and the planing speed was 35 m / min. Ten planing operations were performed. During the planing operations, the bending moment acting on the tool was measured, and the mean bending moment was calculated. The resulting chips were visually assessed and categorized according to their chip shape. A chip shape number was assigned to each chip shape according to the following list, with a chip shape number of at least 0.5 considered sufficient:

[0103] The corrosion susceptibility of the samples in circulating hot water was investigated in a test rig. For this purpose, hollow test specimens were turned and drilled from the samples to be tested in their final state. The test specimens were continuously subjected to a flow of 60 °C hot water at flow velocities of 0.5 m / s and 2.5 m / s in the test rig. The local drinking water used for testing was analyzed on December 20, 2023, and contained the following water constituents:

[0104] Hydrogen carbonate: 352 mg / l (5.68 mmol / l)

[0105] Chloride: 25.8 mg / l

[0106] Sulfate: 17.3 mg / l

[0107] The test specimens were removed after a flow period of 4 weeks, and metallographic sections were prepared through the inner surface. The microstructure on the inner surface of the test specimens was examined using a light microscope, and the maximum corrosion attack was determined. The results of the investigations are documented in Tables 1, 2, and 3. Specimens No. 2, No. 11, No. 12, and No. 14 (Table 1), specimens No. 19, No. 20, and No. 25 (Table 2), as well as specimens No. 34 and No. 40 to No. 42 (Table 3) are specimens according to the invention. Samples No. 1, No. 3 to No. 10, No. 13, No. 15, No. 16 (Table 1), samples No. 21 to No. 24, No. 30 to No. 33 (Table 2) and samples No. 35 to No. 37 and No. 43 to No. 47 (Table 3) are reference samples and are marked with (*).

[0108] To assess the machinability of the samples, the bending moment determined during planing and the shape of the chips were used. A mean bending moment of no more than 60 Nm was considered very favorable. The tables also show the value H for each sample, which is calculated according to the formula described above from the proportions of Si and P in wt.% and the proportions of β-phase and γ-phase in vol.%. A correlation can be observed between the measured bending moment during the planing test and the value of H.

[0109] For the quantitative determination of the phosphide particle size distribution, light microscopy images of unetched longitudinal sections of the samples were used. Image sections measuring 167 pm x 126 pm (corresponding to an area of ​​21,000 pm) were examined. 2Images were selected and evaluated at 1000x magnification using the ImageJ software. This made it possible to identify individual particles and determine their equivalent diameter and area. Based on their equivalent diameter, the particles were categorized as 0.5 to 1 pm, 1 to 2 pm, and greater than 2 pm.

[0110]

[0111] Table 1

[0112]

[0113] Table 1 (continued)

[0114]

[0115] Table 2

[0116]

[0117] Table 2 (continued)

[0118]

[0119] Table 3

[0120]

[0121] Table 3 (continued)

[0122] Specimen No. 1 is a reference specimen in the unannealed condition. With a β-phase volume fraction of 1%, a γ-phase volume fraction of 6%, a silicon content of 1.44 wt.%, and a phosphorus content of 0.090 wt.%, the specimen exhibits a hardness value (H) of 43.8, thus fulfilling the condition H < 60. The average bending moment during planing was determined to be 35.8 Nm, and the chip shape was rated at 1.25. This specimen is therefore exceptionally machinable. The specimen's composition of 70.62 wt.% Cu, 1.44 wt.% Si, and 0.090 wt.% P results in excellent dezincification resistance. The dezincification attack is only 20 µm longitudinally and 14 µm transversely. Therefore, the specimen is dezincification-resistant according to EN ISO 6509-1. However, the volume fraction of the y-phase of 6% does not guarantee resistance to corrosion in circulating hot water.

[0123] Specimen No. 2 is a specimen according to the invention, which was annealed after hot forming. With a volume fraction of 0% for the β-phase, 3% for the γ-phase, a Si content of 1.44 wt.%, and a P content of 0.090 wt.%, the specimen exhibits a value H of 50.5 and thus fulfills the condition H < 60. The average bending moment during planing was determined to be 44.0 Nm, and the chip shape was rated at 0.5. This specimen is therefore readily machinable. The absence of the β-phase is noticeable in the chip shape. The composition of the specimen with 70.62 wt.% Cu, 1.44 wt.% Si, and 0.090 wt.% P ensures, as with specimen No. 1, excellent dezincification resistance. The dezincification attack is only 26 µm longitudinally and 17 µm transversely. This means the sample is dezincification resistant according to EN ISO 6509-1. The Sn content of 0.226 wt.%, together with a volume fraction of the y-phase of only 3%, makes the sample resistant to corrosion in circulating hot water.Samples No. 3 to No. 9 each have a silicon content of less than 1.1 wt.% and a copper content of 63 to 68 wt.%. Due to the low silicon content combined with a volume fraction of the β-phase exceeding 4%, the samples exhibit dezincification depths of more than 200 pm according to EN ISO 6509-1. They are therefore not dezincification-resistant. Large bending moments were measured during planing of samples No. 7 and No. 8. In sample No. 7, this is due to the low silicon content combined with the low β-phase content of only 6 vol.%, while in sample No. 8, the complete absence of silicon cannot be compensated for by the high β-phase content of 12 vol.%. The H value is significantly above 60 for both samples.

[0124] Specimen No. 10 is a reference sample that was annealed after hot forming. The sample contains neither β-phase nor γ-phase, but due to its silicon content of 1.57 wt.% in combination with a phosphorus content of 0.11 wt.%, it is readily machinable: The h-value is 47.4, and the sample exhibits a low bending moment of 45.1 Nm when planed. Specimen No. 10 thus demonstrates that by selectively alloying silicon and phosphorus, even with nearly 100 vol% α-phase, a material with very good machinability can be obtained. The absence of β-phase results in very good dezincification resistance. The maximum attack depth is 31 pm. The tin content of the sample is only 0.01 wt.%, so the material is subject to significant corrosion when exposed to hot water circulation.

[0125] Samples No. 11, No. 12, and No. 14 are samples according to the invention, which were annealed after hot pressing. With regard to their composition, they are similar to sample No. 10, but have a tin content of 0.25 to 0.30 wt.%. All three samples are free of the β-phase. The volume fraction of the γ-phase is 0% (in No. 12), 2% (in No. 11), and 4% (in No. 14), with a silicon content of approximately 1.5 wt.% and phosphorus contents of 0.099 to 0.110 wt.%. For all three samples, the H value lies between 42 and 55, thus fulfilling the condition H < 60. The average bending moment during planing was determined to be 50.9 Nm (No. 11), 54.2 Nm (No. 12), and 48.2 Nm (No. 14). The chip shape was rated at 0.5 (No. 14), 1 (No. 12), and 1.15 (No. 11). Therefore, these samples are machinable to very well. In particular, sample No. 12 demonstrates that by selectively alloying Si and P, a material with good machinability can be obtained even with 99 vol% α-phase.Due to their composition, the samples are highly resistant to dezincification and corrosion. The maximum depth of dezincification attack for these samples is 74 pm, thus meeting the dezincification resistance standard EN ISO 6509-1. The maximum attack depth in the corrosion test rig was determined to be 26 pm (No. 11), 8 pm (No. 12), and 22 pm (No. 14) after 4 weeks of use, and 82 pm (No. 11), 27 pm (No. 12), and 42 pm (No. 14) after 21 weeks of use, all at a flow velocity of 0.5 m / s. At a flow velocity of 2.5 m / s, maximum corrosion depths were determined in the corrosion test rig after 4 weeks of operation to be 0 pm for all three samples and after 21 weeks of operation to be 62 pm (No. 11), 44 pm (No. 12), and 46 pm (No. 14), respectively. The samples therefore demonstrate excellent corrosion resistance when circulating warm water with a high bicarbonate concentration.

[0126] Specimen No. 13 is a reference specimen that was annealed after hot pressing. Due to its composition, the specimen is very resistant to dezincification: the attack depth is 30 pm longitudinally and 25 pm transversely. The volume fraction of the β-phase is 0%, which promotes dezincification resistance. On the other hand, with regard to machinability, the silicon content of 1.29 wt% is too low to compensate for the lack of β- and γ-phases: the H value is 64.3, which is above the limit of 60. The average bending moment during planing was determined to be 105.1, and the chip shape was rated as 0. Therefore, this specimen is poorly machinable.Furthermore, the absence of tin makes the sample susceptible to corrosion in circulating warm water: After four weeks of use in the corrosion test rig, the maximum attack depth was determined to be 79 pm and after 21 weeks 137 pm for a flow rate of 0.5 m / s, and 90 pm for a flow rate of 2.5 m / s after four weeks and 127 pm after 21 weeks. Thus, the sample is significantly more susceptible to corrosion than samples No. 11, No. 12, and No. 14 according to the invention.

[0127] Specimen No. 15 is a reference specimen that was annealed after hot pressing. Due to its composition, the specimen is resistant to dezincification: the attack depth is 92 pm longitudinally and 31 pm transversely. The volume fraction of the β-phase is 0%, which promotes dezincification resistance. The higher silicon content of 1.5 wt.% compared to specimen No. 13, in combination with a phosphorus content of 0.10 wt.%, compensates for the absence of the β- and γ-phases with regard to machinability: the value H is 51.5, thus fulfilling the criterion H < 60. The average bending moment during planing was determined to be 49.2, and the chip shape was rated at 0.5. Therefore, this specimen is readily machinable. Samples No. 13 and No. 15 thus demonstrate that the material's machinability is highly sensitive to the silicon content. The absence of tin makes sample No.15. Susceptible to corrosion in circulating hot water: The maximum attack depth was determined to be 69 pm after 4 weeks of use in the corrosion test rig and 167 pm after 21 weeks for a flow rate of 0.5 m / s, and 144 pm after 4 weeks and 159 pm after 21 weeks for a flow rate of 2.5 m / s. This means that the sample is significantly more susceptible to corrosion than the samples according to the invention.

[0128] Specimen No. 16 is a reference sample that was annealed in its final state, i.e., after the last cold forming, at 750 °C for 2 hours. After annealing, the sample exhibits a volume fraction of 1% for the β-phase and 10% for the γ-phase, with a silicon content of 1.47 wt.% and a phosphorus content of 0.110 wt.%. The H-value is 35.8, thus fulfilling the criterion H < 60. The average bending moment during planing was determined to be 38.5 Nm, and the chip shape was rated at 1.25. This indicates that the sample is very easy to machine. However, the high proportion of γ-phase leads to increased susceptibility to corrosion in the hot water test rig: despite a tin content of 0.25 wt.%.-% A maximum attack depth of 91 pm was determined after 4 weeks of use in the corrosion test rig, and a maximum attack depth of 116 pm after 21 weeks of use for 0.5 m / s flow velocity, and a maximum attack depth of 64 pm after 4 weeks of use and 124 pm after 21 weeks of use for 2.5 m / s flow velocity.

[0129] Sample No. 19 is a sample according to the invention in the annealed state. Its composition, which is identical to that of sample No. 3, with 67.77 wt.% Cu, 0.858 wt.% Si and 0.213 wt.% Sn, yields a zinc equivalent of 0.3717. The condition 0.36 < Zn eqThe requirement of < 0.39 is therefore met. Thus, sample no. 19 is multiphase after hot forming (like sample no. 3) and can be annealed for dezincification resistance. In the final state after annealing at 450 °C / 8 hours, the sample exhibits a volume fraction of 0% for the β-phase and 4% for the γ-phase. Testing for dezincification resistance according to EN ISO 6509-1 yields attack depths of 52 pm longitudinally and 36 pm transversely. Therefore, the sample is dezincification resistant. Machinability in the annealed condition is not optimal, with an average bending moment of 80.2 Nm and a chip shape of 1, solely due to the high bending moment. The chip shape is very good due to a sufficiently high silicon content in combination with phosphide particles in the microstructure. However, if the sample is planed in the state before annealing, i.e. after hot forming and cold forming (corresponds to sample no. 3), the average bending moment is significantly reduced to 41.1 Nm with a chip shape of 1.The sample is therefore very machinable in this intermediate state. With a volume fraction of 6% for the β-phase and 4% for the γ-phase, with a silicon content of 0.858 wt.% and a phosphorus content of 0.124 wt.%, the condition H < 60 for sample no. 3 (and thus also for sample no. 19 before final annealing) with H = 41.1 is fulfilled. Subsequent annealing transforms the very machinable, but not dezincification-resistant, sample no. 3 into the very dezincification-resistant state of sample no. 19.

[0130] Sample No. 20 is a sample according to the invention in the annealed state. Its composition, which is identical to sample No. 4, with 65.65 wt.% Cu, 0.571 wt.% Si and 0.211 wt.% Sn, yields a zinc equivalent of 0.3764. The condition 0.36 < Zn eqThe requirement of < 0.39 is therefore met. Consequently, sample no. 20 is multiphase after hot forming (like sample no. 4) and can be annealed for dezincification resistance in the final state. After annealing at 450 °C for 8 hours, the sample exhibits a volume fraction of 4% of the β-phase and 1% of the γ-phase. Testing for dezincification resistance according to EN ISO 6509-1 yields attack depths of 97 pm longitudinally and 126 pm transversely. Thus, the sample is just barely considered dezincification resistant. Machinability in the annealed state is not optimal, with an average bending moment of 70.5 Nm and a chip shape of 1.25, solely due to the high bending moment. The chip shape is excellent due to a sufficiently high silicon content in combination with phosphide particles in the microstructure. However, if the sample is in the state before annealing, i.e. after hot forming and cold forming (corresponds to sample no.4) After planing, the average bending moment is significantly reduced to 58.6 Nm with a chip shape of 0.75. The specimen is therefore more easily machinable in this intermediate state. With a volume fraction of 12% for the β-phase and 0% for the γ-phase, a silicon content of 0.571 wt.%, and a phosphorus content of 0.132 wt.%, the condition H < 60 is met for specimen no. 4 (and thus also for specimen no. 20 before final annealing) with H = 55.8. Subsequent annealing transforms the easily machinable but not dezincification-resistant specimen no. 4 into the dezincification-resistant state of specimen no. 20.

[0131] Sample No. 25 is a sample according to the invention in the annealed state. Its composition, which is identical to sample No. 9, yields with

[0132] 65.42 wt% Cu, 0.564 wt% Si and 0.235 wt% Sn, a zinc equivalent of 0.3778. The condition 0.36 < Zn eqThe value < 0.39 is therefore fulfilled. Thus, sample no. 25 is multiphase after hot forming (like sample no. 9) and can be annealed for dezincification resistance in its final state. After annealing at 450 °C for 8 hours, the sample exhibits a volume fraction of 0% for the β-phase and 1% for the γ-phase. Testing for dezincification resistance according to EN ISO 6509-1 yields attack depths of 44 pm longitudinally and 53 pm transversely. Therefore, the sample is dezincification resistant. Machinability in the annealed state is not optimal, with an average bending moment of 80.5 Nm and a chip shape of 1.25, solely due to the high bending moment. The chip shape is excellent due to a sufficiently high silicon content in combination with phosphide particles in the microstructure. However, if the sample is in the state before annealing, i.e. after hot forming and cold forming (corresponds to sample no.9) After planing, the average bending moment is significantly reduced to 42.0 Nm with a chip shape of 1. The specimen is therefore excellently machinable in this intermediate state. With a volume fraction of 11% for the β-phase and 0% for the γ-phase, a Si content of 0.564 wt.%, and a P content of 0.240 wt.%, the condition H < 60 is met for specimen no. 9 (and thus also for specimen no. 25 before final annealing) with H = 36.3. Subsequent annealing transforms the readily machinable but not dezincification-resistant specimen no. 9 into the dezincification-resistant state of specimen no. 25. Specimens no. 21 and no. 22 are comparison specimens in the annealed state. Their respective compositions, identical to sample no. 5 and sample no. 6 respectively, yield a zinc equivalent of more than 0.39 for both samples. The condition Zn. eqThe requirement of < 0.39 is therefore not met, which is why the samples cannot be converted into a dezincification-resistant state by annealing. In the final state after annealing at 450 °C / 8 hours, the samples exhibit a volume fraction of the β-phase of 8% (No. 21) and 11% (No. 22), respectively, and a volume fraction of the γ-phase of 1% (No. 21) and 0% (No. 22). Testing for dezincification resistance according to EN ISO 6509-1 yielded attack depths of 230 pm longitudinally / 203 pm transversely on sample No. 21 and 379 pm longitudinally / 278 pm on sample No. 22.

[0133] Specimen No. 23 is a reference specimen in the annealed condition. Its composition, identical to that of Specimen No. 7, results in a zinc equivalent of less than 0.36. Therefore, the specimen is not sufficiently multiphase after hot forming. Machinability in the annealed condition is very poor, with an average bending moment of 121.4 Nm and a chip formation of 0. If the specimen is planed in the pre-annealed condition, i.e., after hot forming and cold forming (corresponding to Specimen No. 7), the average bending moment is also very high at 109.6 Nm with a chip formation of 0. Thus, the specimen is very poorly machinable in both conditions. With a volume fraction of the β-phase of 6% (unannealed) or 3% (annealed) and a volume fraction of the γ-phase of 0% (unannealed) or 2% (annealed) at a Si content of 0.280 wt.% and a P content of 0.096 wt.%, the condition H < 60 is not met by either sample no. 23 with H = 107.8 or by sample no.7 with H = 102.9 is satisfied.

[0134] Sample No. 24 is a comparative sample in the annealed state, whose

[0135] The composition is identical to sample no. 8. Sample no. 24 is indeed dezincification-resistant with a maximum dezincification depth of 75 pm longitudinally and 90 pm transversely, but it does not meet the condition H < 60 in either the annealed or the unannealed intermediate state. Machinability in the annealed state is very poor, with an average bending moment of 119.8 Nm and a chip formation of 0. If the sample is planed in the pre-annealed state, i.e., after hot forming and cold forming (corresponding to sample no. 8), the average bending moment is also very high at 104.8 Nm with a chip formation of 0. The sample is therefore very difficult to machine in both states. With a volume fraction of the β-phase of 12% (unannealed) or 5% (annealed) and a volume fraction of the γ-phase of 0% (unannealed) or 0% (annealed) at a Si content of 0.000 wt.% and a P content of 0.098 wt.%, the condition H < 60 is not met by either sample no. 24 with H = 121.8 or by sample no.8 with H = 81 ,7 is satisfied.

[0136] Specimen No. 30 represents the lead-containing reference alloy CuZn36Pb2As in the annealed condition. With dezincification depths of 86 pm longitudinally and 69 pm transversely, the specimen is dezincification-resistant according to EN ISO 6509-1. The Pb content of 1.5 wt.% makes the material readily machinable. The bending moment determined in the planing test is 21.3 Nm with a chip shape weighted as 0.5.

[0137] Specimen No. 31 represents the lead-reduced alloy CuZn38As with a lead content of 0.2 wt.% in the annealed condition. With dezincification depths of 109 pm longitudinally and 94 pm transversely, the specimen is still dezincification-resistant according to EN ISO 6509-1. Due to the low lead content, the specimen is more difficult to machine than specimen No. 30. The bending moment determined in the planing test is 70.8 Nm with a chip shape rated as 0.

[0138] Sample No. 33 is a reference sample in the annealed condition, whose composition is identical to the unannealed reference sample No. 32. With 70.7 wt.% Cu, 27.8 wt.% Zn, 1.49 wt.% Si and less than 0.0005 wt.% P, the sample has a zinc equivalent of 0.38. The condition 0.36 < Zn eqThe value < 0.39 is therefore fulfilled. Sample No. 33 has an α-phase content of 98 vol.% and a γ-phase content of 2 vol.%. Although Sample No. 33 does not contain any β-phase, it is not dezincification-resistant: When testing for dezincification resistance according to EN ISO 6509-1, attack depths of 182 pm longitudinally and 294 pm transversely are obtained. This is due to the absence of phosphorus, which inhibits the α-phase from dezincification. Since no brittle phosphides are present, chip breakage is difficult in this sample despite the high Si content of almost 1.5 wt.%, and an insufficient chip shape of 0 is observed. Sample No. 33 thus indirectly demonstrates that phosphorus improves not only dezincification resistance but also machinability.

[0139] Sample No. 34 is a sample according to the invention, which, after casting and hot forming (800 °C), was annealed for four hours at 520 °C and subsequently cold-formed by drawing with a degree of deformation of 7.5%. Its composition, with 65.49 wt.% Cu, balance Zn, 0.230 wt.% P, 0.62 wt.% Si and 0.2 wt.% Sn, yields a zinc equivalent of 0.38. The condition 0.36 < Zn eqThe value < 0.39 is therefore fulfilled. In its final state after drawing, the sample exhibits a volume fraction of less than 1% for the β-phase and less than 1% for the γ-phase. Testing for dezincification resistance according to EN ISO 6509-1 yielded low attack depths of 59 pm longitudinally and 46 pm transversely. Thus, the sample is dezincification-resistant. The phosphide particles are very finely dispersed, with 137 particles with an equivalent diameter of 0.5 to 1 pm, 61 phosphide particles with an equivalent diameter of 1 to 2 pm, and 16 phosphide particles with an equivalent diameter greater than 2 pm, within an area of ​​21,000 pm. 2The finely dispersed phosphide particles promote chip breakage, resulting in a good chip shape of 0.5 mm during planing. The sufficiently high silicon content in the alloy also contributes to the good machinability. Sample No. 34 thus demonstrates that a suitable alloy composition, combined with appropriate annealing during the production process, can produce a semi-finished product that exhibits both very good dezincification resistance and good machinability. Because the semi-finished product already possesses both advantageous properties, it is unnecessary to ensure dezincification resistance through a subsequent heat treatment of the component after machining.

[0140] Samples No. 35, No. 36, and No. 37 are reference samples that were hot-formed by pressing at 800 °C after casting. The composition of sample No. 35, with 65.70 wt.% Cu, balance Zn, 0.122 wt.% P, 0.62 wt.% Si, and 0.285 wt.% Sn, yields a zinc equivalent of 0.38. The condition 0.36 < Zn eqThe value < 0.39 is therefore met. Unlike sample no. 34, samples no. 35 to no. 37 were not annealed. Therefore, after pressing, they exhibit a volume fraction of 6 to 10% of the β-phase and a volume fraction of 1 to 2% of the γ-phase. Accordingly, the dezincification resistance test according to EN ISO 6509-1 yields attack depths of 305 pm to 377 pm longitudinally and 78 pm to 193 pm transversely. These samples are therefore not dezincification resistant. The phosphide particles are finely dispersed with 32 to 50 particles with an equivalent diameter of 0.5 to 1 pm, 26 to 46 phosphide particles with an equivalent diameter of 1 to 2 pm, and 5 to 35 phosphide particles with an equivalent diameter of more than 2 pm in an area of ​​21,000 pm. 2This promotes chip breakage. Due to the sufficiently large silicon content (Is) in combination with brittle phosphides, good chip shapes are obtained during planing, corresponding to chip shape numbers of 0.5 and 1. Despite the considerably larger volume fraction of the β-phase compared to sample no. 34, the chip shape is not significantly more favorable. Therefore, the heat treatment performed on sample no. 34 to reduce the β-phase does not lead to a significant deterioration of the machining properties. The formation of a large number of phosphide particles with an equivalent diameter of 0.5 µm to 1.0 µm through the heat treatment has a beneficial effect on chip breakage.

[0141] Samples No. 40, No. 41, and No. 42 are samples according to the invention, which were annealed at 450 °C for 8 hours after casting. The samples were not reshaped. These samples have a tin content between 0.213 and 0.281 wt.%. All three samples have a β-phase content of less than 1 vol.%. The γ-phase volume fraction is 4% (in Nos. 40 and 41) and 5% (No. 42), with a silicon content between 1.2 and 1.4 wt.% and phosphorus content of 0.1 wt.%. For all three samples, the value H lies between 49 and 57, thus fulfilling the condition H < 60. The average bending moment during planing was determined to be 60.6 Nm (No. 40), 62.3 Nm (No. 41), and 82.3 Nm (No. 42). The chip shape was rated at 1.25 for all three samples, indicating excellent machinability. Due to their composition and phase fractions, the samples exhibit high resistance to dezincification and corrosion. The depth of dezincification attack is 16 µm longitudinally and 30 µm transversely (for No. 41).40), 27 pm longitudinally and 17 pm transversely (for No. 41) and 102 pm longitudinally and 127 pm transversely (for No. 42). These samples are therefore dezincification-resistant according to EN ISO 6509-1. In corrosion tests, the maximum attack depth after 4 weeks of use was determined to be 55 pm (No. 40), 43 pm (No. 41), and 97 pm (No. 42) at a flow velocity of 0.5 m / s. The samples thus demonstrate good corrosion resistance in the circulation of warm water with a high bicarbonate concentration.

[0142] Specimen No. 43 is a tin-free reference sample that was annealed at 450 °C for 8 hours after casting. The sample is resistant to dezincification: the attack depth is 88 pm longitudinally and 67 pm transversely. The volume fraction of the β-phase is less than 1% and the volume fraction of the γ-phase is 8%. The H value is 44.0. The average bending moment during planing was determined to be 50.8 Nm and the chip shape was rated at 1.25. This indicates that the sample is very easy to machine. However, the absence of tin makes the sample susceptible to corrosion in circulating hot water: after four weeks of use in the corrosion test rig, the maximum attack depth was determined to be 442 pm at a flow velocity of 0.5 m / s. This results in a significantly stronger attack on the sample than on samples No. 40, No. 41 and No. 42 according to the invention. A comparison of samples No. 40 to No.43 shows that tin improves corrosion resistance when hot water with a high hydrogen carbonate concentration is circulated.

[0143] Samples No. 44, No. 45, No. 46, and No. 47 are reference samples which, unlike samples No. 40 to 43, were not annealed after casting. These samples were not formed. The volume fraction of the β-phase is between 1 and 2 vol.%, and the volume fraction of the γ-phase is between 6 and 11 vol.%. The H-value for these samples ranges from 36.6 to 46.7. The average bending moment during planing was determined to be between 49.4 and 61.2 Nm, and the chip shape was rated at 1 to 1.25. Therefore, these samples are very easy to machine, but due to the high proportion of the γ-phase, they are not resistant to dezincification. The attack depths are 79 to 492 µm longitudinally and 106 to 393 µm transversely. Compared to the annealed variants No. 40 to No. 42, the samples are also more susceptible to corrosion in circulating hot water: After four weeks of use in the corrosion test rig, the three tin-containing samples No. 44, No. 45 and No. 42 showed the following results:46 maximum corrosion depths of 86 to 130 pm were determined for a flow velocity of 0.5 m / s. Additionally, the absence of tin in sample no. 47 leads to significantly increased corrosion in circulating hot water: After four weeks of use in the corrosion test rig, a maximum corrosion depth of 386 pm was determined for the tin-free sample no. 47 at a flow velocity of 0.5 m / s. These investigations demonstrate that even with a cast material, a suitable alloy composition combined with heat treatment can produce a material that is readily machinable, exhibits sufficient dezincification resistance, and is resistant to corrosion in circulating hot water with a high bicarbonate concentration.

Claims

Patent claims 1. Material made of a copper-zinc-silicon alloy with the following Composition: Cu: 67.0 to 72.0 wt.%, Si: 1.20 to 1.80 wt.%, Sn: 0.08 to 0.40 wt.%, P: 0.05 to 0.30 wt.%, Pb: optionally up to 0.10 wt%, Fe: optionally up to 0.20 wt.%, AI: optional up to 0.10 wt.%, Sb: optional up to 0.10 wt.%, As: optional up to 0.10 wt.%, Residual Zn and unavoidable impurities, wherein the material has a microstructure consisting essentially of α-phase, optional β-phase, optional γ-phase and phosphide particles embedded in the phases, and wherein the proportions of β-phase and γ-phase as well as the proportions of Si and P are chosen such that the material meets condition (H) 185.092 - 5.72328 ([Beta]+[Gamma]) - 89.087 [Si ] - 354.137 [P] + 2.8045 ([Beta]+[Gamma]) [Si] + 236.598 [Si] [P] < 60 is satisfied, where [Beta] denotes the proportion of the β-phase in vol.%, [Gamma] the proportion of the γ-phase in vol.%, [Si] the proportion of silicon in wt.% and [P] the proportion of phosphorus in wt.%.

2. Material according to claim 1, characterized in that the proportion of The y-phase in the microstructure of the material is at most 5 vol.%.

3. Material according to claim 1 or 2, characterized in that the Cu content is at least 68.0 wt.% and at most 71.5 wt.%.

4. Material according to one of claims 1 to 3, characterized in that the Si content is at least 1.30 wt.% and at most 1.70 wt.%.

5. Material according to one of the preceding claims, characterized in that the Sn content is at least 0.15 wt.% and at most 0.35 wt.%.

6. Material according to one of the preceding claims, characterized in that the P content is at least 0.07 wt.% and at most 0.25 wt.%.

7. Material according to one of the preceding claims, characterized in that the Pb content is at least 0.03 wt.%.

8. Wire, tube, rod or profile-shaped semi-finished products made of a material according to one of the preceding claims.

9. Media-carrying component made of a material according to one of claims 1 to 7.

10. Method for manufacturing a component from a material consisting of a copper-zinc-silicon alloy, the method comprising the following steps: a) Melting and casting of a cast product made from a copper-zinc-silicon alloy with the following composition: Cu: 64.0 to 72.0 wt.%, Si: 0.40 to 1.80 wt.%, Sn: 0.08 to 0.40 wt.%, P: 0.05 to 0.30 wt.%, Pb: optionally up to 0.10 wt%, Fe: optionally up to 0.20 wt.%, AI: optional up to 0.10 wt.%, Sb: optional up to 0.10 wt.%, As: optional up to 0.10 wt.%, Residual Zn and unavoidable impurities, b) optional heat treatment of the casting, c) optional hot forming of the casting and optional further forming steps, d) resulting in a material having a microstructure consisting essentially of α-phase, optional β-phase, optional γ-phase and phosphide particles embedded in the phases, wherein the proportions of β-phase and γ-phase and the proportions of Si and P are chosen such that the material meets condition (H) 185.092 - 5.72328 ([Beta]+[Gamma]) - 89.087 [Si] - 354.137 [P] + 2.8045 ([Beta]+[Gamma]) [Si] + 236.598 [Si] [P] < 60 is satisfied, where [Beta] denotes the proportion of the β-phase in vol.%, [Gamma] the proportion of the γ-phase in vol.%, [Si] the proportion of silicon in wt.% and [P] the proportion of phosphorus in wt.%, e) Machining of the material, thereby obtaining a component, f) Heat treatment of the component so that the proportion of the β-phase in the microstructure of the material is at most 4 vol.% and the proportion of the γ-phase in the microstructure of the material is at most 5 vol.%.

11. Method for producing a semi-finished product from a copper-zinc-silicon alloy material, the method comprising the following steps: a) Melting and casting a cast product from a copper-zinc-silicon alloy having the following composition: Cu: 64.0 to 72.0 wt.%, Si: 0.40 to 1.80 wt.%, Sn: 0.08 to 0.40 wt.%, P: 0.05 to 0.30 wt.%, Pb: optionally up to 0.10 wt%, Fe: optionally up to 0.20 wt.%, AI: optional up to 0.10 wt.%, Sb: optional up to 0.10 wt.%, As: optional up to 0.10 wt.%, Residual Zn and unavoidable impurities, b) optional heat treatment of the casting, c) hot forming and / or cold forming of the casting, whereby a semi-finished product is obtained from a material having a microstructure consisting essentially of α-phase, optional β-phase, optional γ-phase and phosphide particles embedded in the phases, wherein the process includes at least one heat treatment of the semi-finished product after hot forming or after cold forming, wherein the heat treatment is carried out in the temperature range between 450 °C and 550 °C for 2 to 8 hours, such that the proportion of the optional β-phase in the microstructure of the material of the semi-finished product is at most 4 vol.% and the proportion of the optional γ-phase in the microstructure of the material is at most 5% by volume.

12. Method according to claim 11, characterized in that the Heat treatment is carried out in the temperature range between 505 °C and 525 °C for 2 to 8 hours.

13. Method according to claim 11 or 12, characterized in that the material after heat treatment has a microstructure in which, over an area of ​​21000 pm 2 30 to 160 phosphide particles with an equivalent diameter of 0.5 to 1 pm, 10 to 150 phosphide particles with an equivalent diameter of 1 to 2 pm and a maximum of 40 phosphide particles with an equivalent diameter of more than 2 pm are present.

14. Method according to one of claims 10 to 13, characterized in that the material meets the condition 0.36 < ([Zn]+10 [Si]+2.3 [Sn]) / ([Cu]+[Zn]+10 [Si]+2.3 [Sn]) < 0.39 is satisfied, where [Cu] denotes the proportion of Cu in wt.%, [Zn] the proportion of Zn in wt.%, [Si] the proportion of silicon in wt.%, [Sn] the proportion of Sn in wt.%.

15. Method according to one of claims 10 to 14, characterized in that the Cu content of the copper-zinc-silicon alloy is at least 64.5 wt.% and at most 66.5 wt.% and the Si content of the copper-zinc-silicon alloy is at least 0.50 wt.% and at most 0.70 wt.%.

16. Method according to one of claims 10 to 14, characterized in that the Cu content of the copper-zinc-silicon alloy is at least 67.0 wt.% and at most 69.5 wt.% and the Si content of the copper-zinc-silicon alloy is at least 0.75 wt.% and at most 0.95 wt.%.

17. Method according to one of claims 10 to 16, characterized in that the Sn content of the copper-zinc-silicon alloy is at least 0.15 wt.% and at most 0.35 wt.%.

18. Method according to one of claims 10 to 17, characterized in that the P-part of the copper-zinc-silicon alloy is at least 0.07 wt.% and at most 0.25 wt.%.

19. Method according to any one of claims 10 to 18, characterized in that the Pb content of the copper-zinc-silicon alloy is at least 0.03 wt.%.

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