Lead-free brass alloy

Abstract

The invention relates to a lead-free brass alloy for use in the manufacture of components for use in the lock and key industry and in the sanitary sector, comprising 1 - 45% zinc, 0.01 - 1% sulfur, 0.05 - 2% manganese, optionally including one or more other elements totaling 0.001 - 5%, and copper as the remaining portion to total 100%.

Description

[0001] The present invention relates to a lead-free brass alloy for use in the production of components for use in the lock and key industry and in the sanitary sector, a component made of such a lead-free brass alloy and a process for producing a lead-free brass alloy.

[0002] Brass alloys based on a combination of the elements Cu and Zn are used in a wide variety of industries due to their excellent combination of corrosion resistance, good thermal and electrical conductivity, castability, formability, and coatability. The high toughness of such copper alloys is particularly advantageous for the semi-finished production of rods, wires, and strips.

[0003] Unfortunately, brass alloys have proven less suitable for machining, particularly for continuous cutting processes, due to late chip breakage. The machinability of a material can be assessed particularly with regard to the criteria of cutting force, chip shape, component quality, and tool wear. With regard to copper alloys, the DKI (German Copper Institute: "Recommended machining parameters for copper and copper alloys", DKI Monograph i.18, 2010) defines the evaluation of machinability according to a machinability index. In Europe, the copper alloy CuZn39Pb3 is used for reference purposes, which is considered to have optimal machinability and therefore has a defined machinability index of 100. Decreasing machinability is usually represented by a reduction in the machinability index in increments of 10.

[0004] Pure copper has the lowest listed index with a machinability index of 20, the lead-free brass alloy CuZn37 achieves an average machinability index of 40, and the two-phase brass CuZn42 an average machinability index of 55. Absolute values ​​for a machinability index or a machinability index stated in this application preferably refer to a measurement carried out in accordance with or based on the final report of the research project conducted by the WZL with a precise explanation of the measurement of the machinability index: "Development of a high-performance machining process for difficult-to-machine lead-free copper wrought and cast alloys: Final report of the research center(s) no.1, Laboratory for Machine Tools and Production Engineering (WZL) at RWTH Aachen University on the project IGF16867 N funded by the AiF within the framework of the program for the promotion of industrial joint research and development (IGF) by the Federal Ministry of Economics and Technology based on a resolution of the German Bundestag; (approval period: 01.01.2011) - RWTH Publications (rwth-aachen.de)".

[0005] To improve machinability, it is known from the state of the art to add small amounts (e.g., 1-3%) of lead to alloys. Lead is insoluble in copper-containing alloys and forms a second phase, which causes chip breakage and thus improves machinability. Lead is also said to have a lubricating effect, which positively influences cutting forces and tool temperatures, as well as tool life.

[0006] Unfortunately, due to its toxicity, lead is subject to continually increasing regulatory restrictions. Lead has been classified as a substance of very high concern (SVHC) if an article contains more than 0.1% lead. Lead or its compounds may not be used or placed on the market in jewelry or in articles intended for the general public, particularly if the lead-containing metal can be put in the mouth by children and the permitted release rate of 0.05 µg cm² is exceeded.

[0007] Another regulation that specifically limits the lead content of Cu-Zn materials used in sanitary facilities is the EU Drinking Water Regulation (EU Drinking Water Directive 2020 / 2184), which lowers the limit value for lead in drinking water from 10 µg / l (0.01 mg / l) to 5 µg / l (0.005 mg / l).

[0008] Although lead-free, machinable alternatives are known in the field of Cu-Zn alloys, these alternatives have other disadvantages. For example, it is known to replace lead with silicon or bismuth (see, for example, DE 889 984 C, GB 2 211 206 A). However, even small amounts of bismuth added to the alloy cause embrittlement, which impairs the cold formability of the Cu-Zn alloys. Adding silicon leads to the formation of hard phases, which is particularly problematic for tool life and tool wear, as well as for production using continuous casting processes.

[0009] In the field of zinc- and nickel-free copper alloys, a lead-free alloy is also known, for example, from EP 2 625 300 B1, which contains an addition of 0.1–0.8% sulfur and 0.1–0.2% manganese as a chip breaker. However, the proposed ratio between manganese and sulfur has proven disadvantageous; in particular, it has been recognized that the proposed ratio between manganese and sulfur leads to adverse cold formability. Furthermore, the proposed ratio between manganese and sulfur would lead to the formation of eutectic zinc sulfides when using zinc, which, in addition to adverse cold formability, would negatively impact the impact and shock resistance of the material.

[0010] It is therefore the object of the present invention to at least partially remedy the aforementioned disadvantages of known brass alloy systems. In particular, the object of the invention is to provide an alloy system that is harmless to health and exhibits excellent processability, in particular improved machinability, with a given cold formability.

[0011] The above object is achieved by a lead-free brass alloy having the features of independent claim 1, a method having the features of the independent method claim, and a device claim having the features of claim 14. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details mentioned in connection with the alloy system according to the invention naturally also apply in connection with the component according to the invention and the method according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0012] According to the invention, a lead-free brass alloy is intended for use in the manufacture of components for use in the lock and key industry, as well as in the sanitary sector. The lead-free brass alloy according to the invention comprises 1-45% zinc, 0.01-1% sulfur, 0.05-5% manganese, optionally a total of 0.001-5% one or more other elements, and copper as the remaining portion to reach 100%.

[0013] In the context of the invention, a lead-free brass alloy can preferably be understood to mean an alloy which has the elements copper and zinc as its main components and is lead-free (< 0.1% Pb) except for traces of unavoidable impurities. Of the main components, copper can preferably represent the largest component in terms of quantity. It is understood that, in addition to the components or elements mentioned, as well as sulfur, manganese and some optional components, traces of unavoidable impurities can also be contained in the lead-free brass alloy according to the invention, which can preferably be contained in the alloy in a proportion of < 0.5% (in total) and < 0.2% (for one element), in particular in a proportion of < 0.2% (in total) and < 0.1% (for one element).A component for use in the lock and key industry can advantageously be understood as components such as locking cylinders, keys, locking fittings, locks, or closures. A component for use in the sanitary sector can preferably be understood as pipes, pipe connections, or fittings, or the like. The specified percentages can also advantageously be understood as mass fractions.

[0014] Before proceeding with the following explanations, it should be noted that the percentages of the respective components of the alloy in question refer to the total amount of 100% or, accordingly, add up to 100%. The percentages correspond to weight percent.

[0015] Within the scope of the present invention, it has been recognized that by adding sulfur and manganese in proportions specifically selected according to the invention, a lead content can be compensated or substituted and an alloy system that is harmless to health can be provided which has excellent processability, in particular improved machinability while maintaining cold formability.

[0016] With a view to increasing the hardness and strength of the lead-free brass alloy, it can advantageously be provided according to the invention that copper represents the main alloy component, wherein copper is preferably present in a proportion of > 55%, particularly preferably in a proportion between 55 and 80%, in particular in a proportion between 63 and 80% in the lead-free brass alloy.

[0017] To achieve simple and versatile machinability, the invention advantageously provides that the lead-free brass alloy is machinable and producible using a continuous casting process and is cold-formable. In this case, cold formability is preferably understood to mean the deformation of a shaped body at room temperature to a degree of deformation of > 40% without the material cracking or being otherwise damaged. In addition to cold formability, the alloy according to the invention can be particularly suitable for being machinable via other production routes, such as direct part casting or semi-finished product production using semi-finished forms such as rods, tubes, or wires.

[0018] With regard to the safe use and robust and stable design of a lead-free brass alloy with versatile machinability, it can also be advantageous if the alloy is also silicon-free and / or bismuth-free and / or nickel-free. Avoiding silicon and bismuth also serves to prevent material embrittlement and the formation of hard phases, which negatively impact the cold formability of materials and tool wear. Silicon-containing brass alloys are also more difficult to produce by continuous casting. Avoiding nickel can preferably improve the processability, in particular the formability, of the alloy according to the invention.

[0019] In order to reduce health risks and environmental pollution as well as to improve processability, it can also advantageously be provided that the alloy according to the invention is antimony-free and / or lanthanum-free (contains no antimony and / or lanthanum, or only in traces of < 0.1%).

[0020] With a view to the most targeted adaptability of further material properties of the alloy according to the invention, it can advantageously be provided that the one or more additional elements optionally contained in the lead-free brass alloy in a total of 0.001-5% are selected from the group consisting of aluminum, chromium, phosphorus, tellurium, tungsten, magnesium, calcium, iron, and cerium. Aluminum can preferably be contained in the lead-free brass alloy in a proportion of <0.9% to prevent embrittlement of the material and ensure easy castability of the alloy.

[0021] With regard to improved processability, in particular improved machinability with a given cold formability, it has been found to be particularly advantageous to add the elements chromium and / or cerium and / or tungsten to a total amount of 0.001 - 5% in the alloy according to the invention.

[0022] With regard to simple, fast and inexpensive machinability, it is also advantageously conceivable that the lead-free brass alloy has a machinability index of > 50 at least with regard to one of the criteria process force, chip formation, component quality or tool wear, based on the measurement procedure mentioned above in accordance with the final report of the research project carried out by the WZL.

[0023] In the context of improved, preferably simplified, workability, in particular via an extrusion process or a cold forming process, it can advantageously be further provided according to the invention that the alloy has a proportion of an M 2 S phase (where M = Cu and / or Zn) of < 10% of the volume of the sulfides formed, preferably of < 1% of the volume of the sulfides formed.

[0024] In the context of improved, preferably simplified, machinability via an extrusion process or a cold forming process, it is particularly advantageous for the alloy to contain monosulfides, wherein the monosulfides are preferably predominantly in the form of manganese sulfide, in particular more than 80% in the form of manganese sulfide. The inventive addition of sulfur in combination with the defined manganese content leads to the suppression of the disadvantageous zinc-based or copper-based sulfides of the M 2 N type and causes the formation of spherical manganese sulfides, which improve machinability while simultaneously not hindering the cold formability of the material.

[0025] Accordingly, within the scope of the invention, it can advantageously be provided that the monosulfides have a spherical morphology. This can advantageously reduce the formation of eutectic Zn-Mn sulfides, which have an embrittling effect and counteract cold formability.

[0026] With a view to achieving an advantageous ratio between sulfur and manganese to improve cold formability and machinability, it can preferably be provided that the manganese content in the alloy is more than three times the sulfur content, preferably more than four times.

[0027] In addition, to increase the hardness and strength of the lead-free brass alloy, the zinc content may be 5 to 38% and / or the copper content 55 to 95%, preferably 63 to 95%.

[0028] Advantageously, the brass alloy according to the invention can have improved machinability (at least with regard to the criterion of process force, ie a lower process force to be applied) compared to a single-phase brass alloy.

[0029] With a view to significantly improving the machinability of the lead-free brass alloy in question, it can advantageously also be provided that sulfur is contained in the lead-free brass alloy at a level of 0.05 to 0.5%.

[0030] Manganese may also advantageously be contained in the nickel silver alloy according to the invention in a proportion of 0.2 to 2%.

[0031] In the context of high homogeneity, high density (low porosity), high strength and toughness of the alloy material in question, as well as a low amount of impurities, it can advantageously be provided that the brass alloy according to the invention is in the form of a fused-salt alloy. A fused-salt alloy can be understood in particular as an alloy produced using a fused-salt process.

[0032] The invention also further relates to a component made of a lead-free brass alloy described above for use in the lock and key industry or in the sanitary sector. Thus, the component according to the invention offers the same advantages as those already described in detail with regard to the lead-free brass alloy according to the invention.

[0033] The invention further relates to a process for producing a lead-free brass alloy, preferably a lead-free brass alloy described above. The process according to the invention comprises the steps of mixing the following alloy components in the specified proportions to produce a component mixture: 1-45% zinc, 0.01-1% sulfur, 0.05-5% manganese, optionally a total of 0.001-5% one or more other elements, and copper as the remaining portion to reach 100%, heating the component mixture to melt the components, and cooling the molten lead-free brass alloy. Thus, the process according to the invention offers the same advantages as those already described in detail with regard to the lead-free brass alloy according to the invention or the component described above.It is understood here that individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out in the proposed order, but also deviating from the proposed order. Individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out repeatedly, for example, cyclically. It is further understood that individual, several, or all of the mandatory and optional steps of the method according to the invention can also be carried out at least partially automatically or in an automated and / or self-learning manner, in particular by being implemented by a computer.

[0034] With regard to effective heating of the mixed alloy components to melt them, it can also be provided that the alloy is produced using a molten metal process or a sintering process. A molten metal process can be understood, in particular, as primary forming from a melt. A molten metal process is particularly suitable in this case with regard to high homogeneity, high density (low porosity), as well as high strength and toughness of an alloy material. Furthermore, impurities can generally be removed very efficiently using a molten metal process.

[0035] Within the scope of a suitable further processing or machining of the lead-free brass alloy in question for the production of components for use in the lock and key industry as well as in the sanitary sector, it can advantageously be further provided according to the invention that the alloy is further processed after production by means of an extrusion process and / or by means of a cold forming process.

[0036] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail, partly with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0037] It shows: Fig. 1 a schematic representation of the individual steps of a process according to the invention for producing a lead-free brass alloy according to the invention.

[0038] Fig. 1 shows a schematic representation of the individual steps of a method according to the invention for producing a lead-free brass alloy.

[0039] As per Fig. 1 As can be seen, the method according to the invention comprises the steps of mixing 100 the following alloy components according to the stated proportions to produce a component mixture: 1 - 45% zinc, 0.01 - 1% sulfur, 0.05 - 5% manganese, optionally a total of 0.001 - 5% one or more further elements and copper as the remaining part missing to a total of 100%, heating 200 the component mixture to melt the components and cooling 300 the molten lead-free brass alloy.

[0040] The alloy can be produced, for example, using a melt flow process or a sintering process.

[0041] In addition, the alloy can be further processed after production by means of an extrusion process and / or by means of a cold forming process. Examples of implementation:

[0042] Table 1 below lists some exemplary compositions for a lead-free brass alloy according to the invention. The ratios given are to be understood as weight percentages. The "R" in the column for copper stands for the remainder or the remaining portion. Table 1 Nr. Zn S Mn Al Cr P The W Mg Ca Cu 1 5 0,05 0,25 0,003 - 0,003 - 0,002 0,02 R 2 28 0,2 1 - 0,5 - 0,02 0,002 - 0,002 R 3 25 0,5 2,5 - - - - - 0,5 R 4 10 0,15 0,8 0,01 - 0,005 - 0,5 0,5 R 5 32 0,9 4,5 0,002 - - 0,5 0,001 R 6 36 1 5 0,5 0,01 0,001 0,001 - - R 7 42 0,3 1,5 0,001 - 0,002 - - - 0,01 R

[0043] The above explanation of the embodiments describes the present invention exclusively by way of examples. Of course, individual features of the embodiments can be freely combined with one another, provided they are technically feasible, without departing from the scope of the present invention.

[0044] By means of the lead-free brass alloy listed above, it is possible in particular to provide a material which is harmless to health for the production of components for use in the lock and key industry as well as in the sanitary sector, which is easy to process and in particular has excellent cold formability and machinability. List of reference symbols

[0045] 100Mixing the alloy components to produce a component mixture 200Heating the component mixture to melt the components 300Cooling the molten lead-free brass alloy

Claims

1. Lead-free brass alloy for use in the manufacture of components for use in the lock and key industry and in the sanitary sector, comprising: - 1 - 45% zinc, - 0.01 - 1% sulphur, - 0.05 - 5% manganese, - optionally a total of 0.001 - 5% one or more other elements, - and copper as the remaining part to make up 100%.

2. Lead-free brass alloy according to claim 1, characterized by that Copper is the main alloy component, with copper preferably being present in a proportion of > 55%, particularly preferably in a proportion between 55 and 80%, in particular in a proportion of > 63% in the lead-free brass alloy.

3. Lead-free brass alloy according to claim 1 or 2, characterized by that the lead-free brass alloy can be produced and / or processed in a continuous casting process and is cold-formable.

4. Lead-free brass alloy according to one of the preceding claims, characterized by that the alloy is silicon-free and / or bismuth-free and / or nickel-free.

5. Lead-free brass alloy according to one of the preceding claims, characterized by that the alloy is antimony-free and / or lanthanum-free.

6. Lead-free brass alloy according to one of the preceding claims, characterized by that which optionally contain one or more further elements from the group aluminium, chromium, iron, calcium, cerium, phosphorus, tellurium, tungsten, magnesium, in a total amount of 0.001 - 5% in the lead-free brass alloy.

7. Lead-free brass alloy according to one of the preceding claims, characterized by that the lead-free brass alloy has a machinability index of > 50.

8. Lead-free brass alloy according to one of the preceding claims, characterized by thatthe alloy has a proportion of an M2S phase, where M = Cu and / or Zn, of < 10% of the volume of the sulphides formed, preferably of < 1% of the volume of the sulphides formed.

9. Lead-free brass alloy according to one of the preceding claims, characterized by that the alloy comprises monosulfides, wherein the monosulfides are preferably largely in the form of manganese sulfide, in particular more than 80% in the form of manganese sulfide.

10. Lead-free brass alloy according to one of the preceding claims, characterized by that the monosulfides have a spherical morphology.

11. Lead-free brass alloy according to one of the preceding claims, characterized by thatthe manganese content in the alloy is more than three times the sulfur content, preferably more than four times and / or that the zinc content is 5 to 38% and / or the copper content is 55 to 95%, preferably 63 to 95%.

12. Lead-free brass alloy according to one of the preceding claims, characterized by that Sulphur is contained in the lead-free brass alloy at > 0.05%, preferably at 0.06 to 0.5%.

13. Component made of a lead-free brass alloy according to any one of the preceding claims for use in the lock and key industry or in the sanitary sector.

14. A method for producing a lead-free brass alloy, preferably a lead-free brass alloy according to one of the preceding claims, comprising the steps of: - mixing (100) the following alloy components according to the specified proportions to produce a component mixture: 1 - 45% zinc, 0.01 - 1% sulfur, 0.05 - 5% manganese, optionally a total of 0.001 - 5% one or more further elements and copper as the remaining part missing to a total of 100%, - heating (200) the component mixture to melt the components, - cooling (300) the molten lead-free brass alloy.

15. Method according to claim 14, characterized by that the alloy is produced by a molten metal process or a sintering process and / or that the alloy is further processed after production by means of an extrusion process and / or by means of a cold forming process.

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