New silver alloy

Abstract

The invention relates to a nickel silver alloy for use in the manufacture of components for use in the lock and key industry as well as in the jewelry and watch industry, comprising 1 - 30% nickel, 8 - 45% zinc, 0.01 - 1% sulfur, 0.05 - 5% manganese, optionally including one or more further elements totaling 0.001 - 5%, and copper as the remaining portion to total 100%.

Description

[0001] The present invention relates to a nickel silver alloy for use in the production of components for use in the lock and key industry as well as in the jewelry and watch industry, a component made of such a nickel silver alloy and a process for producing a nickel silver alloy.

[0002] Nickel silver alloys based on a combination of the elements Cu, Ni, 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, nickel silver 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, while the only listed lead-free nickel silver alloy, CuNi18Zn20, achieves an average machinability index of 33. Absolute values ​​for a machinability index or 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., 0.1-3%) of lead to alloys. Lead is insoluble in copper-containing alloys and forms a second phase that improves chip breaking and thus machinability. Lead is also said to have a lubricating effect, which positively influences cutting forces, tool temperatures, and tool life.

[0006] Unfortunately, due to its toxicity, the element lead is subject to continually advancing legal restrictions. For example, lead has been classified as a substance of very high concern (SVHC) as soon as 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, if the article contains more than 0.05% lead. Furthermore, the amendment to Regulation EC 1272 / 2008 is scheduled to come into force on September 1, 2025. This classifies massive lead as chronically hazardous to water and therefore as hazardous waste.

[0007] 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.

[0008] It is therefore the object of the present invention to at least partially remedy the aforementioned disadvantages of known nickel silver 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.

[0009] The above object is achieved by a nickel silver 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 13. 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.

[0010] According to the invention, a nickel silver alloy is intended for use in the manufacture of components for use in the lock and key industry, as well as in the jewelry and watchmaking industry. The nickel silver alloy according to the invention comprises 1-30% nickel, 8-45% zinc, 0.01-1% sulfur, 0.05-5% manganese, optionally one or more other elements totaling 0.001-5%, and copper as the remaining portion to reach 100%.

[0011] For the purposes of the invention, a nickel silver alloy can preferably be understood as an alloy which has the elements copper, nickel, and zinc as its main components. 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 nickel silver alloy according to the invention, which can preferably be present 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 jewelry and watch industry can advantageously be understood as components such as bracelets, chains, carriers, clasps, watch movements, wheels, springs, and hands.The percentages given can also advantageously be understood as mass fractions.

[0012] Before proceeding with the following explanations, it should be noted that the percentages of the respective components of the alloy in question preferably refer to the total amount of 100% or, accordingly, add up to 100%. The percentages correspond to weight percent.

[0013] 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.

[0014] With a view to increasing the hardness and strength of the nickel silver alloy, it can advantageously be provided according to the invention that copper is the main alloy component, with copper preferably being present in the nickel silver alloy in a proportion of >30%, in particular >40%. Particularly preferably, the nickel silver alloy can have a copper content of >50%, in particular >60%.

[0015] To achieve simple and versatile machinability, the invention advantageously provides that the nickel silver alloy is castable in a continuous casting process and is cold-formable. Cold-formability is preferably understood to mean the deformation of a shaped body at room temperature to a degree of deformation of > 40% without cracking or other damage to the material. In addition to cold-formability, the alloy according to the invention can be particularly suitable for processing via other production routes, such as direct part casting or semi-finished product production using semi-finished forms such as rods, tubes, or wires.

[0016] With regard to the health-safe use and robust and stable design of a nickel silver alloy with versatile machinability, it can also be advantageous if the alloy is lead-free, silicon-free, and / or bismuth-free. Avoiding lead can be done particularly due to the described toxicity of lead compounds. Avoiding the use of 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 nickel silver alloys are also more difficult to produce by continuous casting.

[0017] 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 further elements optionally contained in the nickel silver alloy in a total of 0.001 - 5% are selected from the group of aluminum or other foreign elements for nucleation, such as zirconium, iron, titanium, calcium, cerium, tellurium, chromium, phosphorus, molybdenum, tungsten or magnesium.

[0018] With regard to simple, fast and inexpensive machinability, it is also advantageously conceivable that the nickel silver 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.

[0019] 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%.

[0020] 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, with the monosulfides preferably being 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 and / or copper-based sulfides and causes the formation of spherical manganese sulfides, which determine the advantageous formability in combination with good machinability.

[0021] 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.

[0022] 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.

[0023] Furthermore, to increase the hardness and strength of the nickel silver alloy, the nickel content can be 1 to 18%, preferably 5 to 15%, and / or the zinc content 10 to 40%, preferably 15 to 20%, and / or the copper content 40 to 80%, preferably 50 to 70%. A nickel content of 7% in combination with a zinc content of 35 to 38% has proven particularly advantageous with regard to increasing the hardness and strength of the nickel silver alloy.

[0024] Advantageously, the nickel silver 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 and / or with regard to the criterion of surface quality and / or tool wear) compared to a single-phase nickel silver alloy.

[0025] With a view to significantly improving the machinability of the nickel silver alloy in question, it may also be advantageous if sulphur is contained in the nickel silver alloy at a level of 0.05 to 0.5%.

[0026] Manganese may also preferably be contained in the nickel silver alloy according to the invention in a proportion of 0.2 to 2%.

[0027] The invention also further relates to a component made of a nickel silver alloy described above for use in the lock and key industry or in the jewelry and watchmaking industry. Thus, the component according to the invention offers the same advantages as those already described in detail with regard to the nickel silver alloy according to the invention.

[0028] The invention further relates to a process for producing a nickel silver alloy, preferably a nickel silver 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: 1-30% nickel, 8-45% 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 nickel silver alloy. Thus, the process according to the invention offers the same advantages as those already described in detail with regard to the nickel silver 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.

[0029] With a view to effectively heating the mixed alloy components to melt the components, it can further be provided that the alloy is produced by a fused metal process or a sintering process.

[0030] Within the scope of a suitable further processing or machining of the nickel silver alloy in question for the production of components for use in the lock and key industry as well as in the jewelry and watch industry, 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 and / or a casting process (e.g. direct part casting).

[0031] 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.

[0032] They show: Fig. 1 a representation of a microscopic image of a nickel silver alloy according to the invention (right image) together with a nickel silver alloy with a sulfur-manganese ratio deviating from the inventive sulfur-manganese ratio (left image), Fig. 2 graphical plot of the cutting force for three different nickel silver alloys (1 to 3) in two different measurements, Fig. 3 a schematic representation of the individual steps of a method according to the invention for producing a nickel silver alloy according to the invention.

[0033] Fig. 1 shows a representation of a microscopic image of a nickel silver alloy according to the invention (right image) together with a nickel silver alloy with a sulfur-manganese ratio deviating from the sulfur-manganese ratio according to the invention (left image).

[0034] In particular, the Fig. 1a metallographic section of a Cu-Ni-Zn alloy according to the invention cast by continuous casting with a content of 0.075% sulfur and 0.4% manganese (right image) and a metallographic section of a Cu-Ni-Zn alloy cast by continuous casting with 0.1% sulfur and 0.2% manganese (left image).

[0035] As can be seen from a comparison of the two images, in the representation of the Cu-Ni-Zn alloy according to the invention with a proportion of 0.075% sulfur and 0.4% manganese (right image), a formation of round or spherical monosulfides can be seen, which indicate a cold formability of at least 40% (see markings).

[0036] On the left side, however, the formation of eutectic Zn-Mn sulfides can be seen (see markings), which have an embrittling effect and counteract the desired cold formability.

[0037] Fig. 2shows a graphical plot of the cutting force (in Newton) for three different nickel silver alloys (1 to 3) in two different measurements.

[0038] Measurements 1 and 2, which differ with regard to the design of a groove created during machining (measurement 1: groove width = 1 mm, measurement 2: groove width = 2 mm), qualitatively show the same picture, namely an increase in the determined machining force, starting with a nickel silver alloy with a 1% lead content (nickel silver alloy 1), to the nickel silver alloy according to the invention with a sulfur content (nickel silver alloy 2) to a nickel silver alloy without lead and sulfur content (nickel silver alloy 3), which demonstrates the advantageous use of sulfur as a lead substitute. The measurements are to be evaluated purely qualitatively and show that the process force required when machining a nickel silver alloy according to the invention lies between the process force required for a nickel silver alloy with a 1% lead content (nickel silver alloy 1) and a nickel silver alloy without lead and sulfur content (nickel silver alloy 3).

[0039] A torus cutter was used as the profile cutter. It was milled through the respective sample material (workpieces made of nickel silver alloys 1 to 3) at a cutting depth of 0.1 mm in several steps up to a maximum depth of 1.7 mm at a 90° angle in a face milling process. The process force was determined using a Kistler Micro Dyn with a response threshold of < 0.002 N, a sensitivity of -12.5 pC / N (F x,y ) and -20 pC / N (F z ), and a cutoff frequency fn(x,y,z) > 15 kHz.

[0040] Fig. 3 shows a schematic representation of the individual steps of a method according to the invention for producing a nickel silver alloy.

[0041] As per Fig. 3As 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 - 30% nickel, 8 - 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 nickel silver alloy.

[0042] The alloy can be produced, for example, using a melt flow process or a sintering process.

[0043] 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:

[0044] Table 1 below lists some exemplary compositions for a nickel silver alloy according to the invention. The specified ratios are to be understood as weight fractions. Table 1 Nr. Ni Zn S Mn Al Cr P Mon W Mg Ca Cu 1 13 24 0,07 0,35 - - - - - - - R 2 12 25 0,5 2,2 0,002 - - 0,001 0,02 0,001 R 3 2 27 0,1 0,6 - - - - - - 0,05 R 4 18 27 0,15 0,8 0,003 0,02 0,02 0,001 - R 5 7 38 0,3 1,5 0,03 0,01 0,005 - 0,05 - R 6 25 10 0,05 0,3 0,02 0,002 0,001 0,001 - - 0,01 R

[0045] 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.

[0046] By means of the nickel silver 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 jewellery and watch industry, which has easy processability, in particular has a given cold formability and improved machinability. List of reference symbols

[0047] 100Mixing the alloy components to produce a component mixture 200Heating the component mixture to melt the components 300Cooling the molten nickel silver alloy

Claims

1. Nickel silver alloy for use in the manufacture of components for use in the lock and key industry as well as in the jewelry and watch industry, comprising: - 1 - 30% nickel, - 8 - 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 part missing to a total of 100%.

2. Nickel silver alloy according to claim 1, characterized by that Copper is the main alloy component, with copper preferably being present in a proportion of > 30%, in particular in a proportion of > 40% in the nickel silver alloy.

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

4. Nickel silver alloy according to one of the preceding claims, characterized by thatthe alloy is lead-free and / or silicon-free and / or bismuth-free.

5. Nickel silver alloy according to one of the preceding claims, characterized by that which optionally contain one or more further elements from the group aluminium, chromium, phosphorus, molybdenum, tungsten, magnesium, zirconium, iron, titanium, calcium, cerium, tellurium, totalling 0.001 - 5% in the nickel silver alloy.

6. Nickel silver alloy according to one of the preceding claims, characterized by that the nickel silver alloy has a machinability index of > 50.

7. Nickel silver alloy according to one of the preceding claims, characterized by that the alloy has a proportion of an M2S 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, where the proportion of the MnS phase is in particular at least four times as large as the proportion of the M2S phase.

8. Nickel silver 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.

9. Nickel silver alloy according to one of the preceding claims, characterized by that the monosulfides have a spherical morphology.

10. Nickel silver alloy according to one of the preceding claims, characterized by that the manganese content in the alloy is more than three times the sulfur content, preferably more than four times.

11. Nickel silver alloy according to one of the preceding claims, characterized by that the nickel content is 1 to 18% and / or the zinc content is 10 to 40% and / or the copper content is 50 - 70%.

12. Nickel silver alloy according to one of the preceding claims, characterized by thatSulphur is contained in the nickel silver alloy at 0.05 to 0.5%.

13. A component made of a nickel silver alloy according to any one of the preceding claims for use in the lock and key industry or in the jewelry and watchmaking industry.

14. A method for producing a nickel silver alloy, preferably a nickel silver 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 - 30% nickel, 8 - 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 nickel silver alloy.

15. Method according to claim 14, characterized by thatthe 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 and / or by means of a casting process.

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