Nickel 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 manufacture 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 method 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 coating properties. The high toughness of such copper alloys is particularly advantageous for the production of semi-finished products such as bars, wires, and strips.

[0003] Unfortunately, nickel silver alloys have proven less suitable for machining, especially for continuous cutting processes, due to their delayed chip breakage. The machinability of a material can be evaluated based on criteria such as cutting force, chip shape, component quality, and tool wear. For copper alloys, the German Copper Institute (DKI) recommends a machinability index, specifically "Recommended machining parameters for copper and copper alloys" (DKI Monograph i.18, 2010). In Europe, the copper alloy CuZn39Pb3 is used for reference purposes, as it is considered optimally machinable and therefore has a defined machinability index of 100. Decreasing machinability is typically represented by a reduction in the machinability index in increments of 10.

[0004] Pure copper has the lowest listed machinability index of 20, while the only listed lead-free nickel silver alloy, CuNi18Zn20, achieves a medium machinability index of 33. The absolute values ​​mentioned in this application regarding a machinability index or a machining index preferably refer to a measurement procedure according to or based on the final report of the research project carried out by the WZL, with a detailed explanation of the measurement of the machinability index: “Development of high-performance machining for difficult-to-machine lead-free wrought and cast copper alloys: Final report of the research unit(s) No.1, Machine Tool Laboratory (WZL) of RWTH Aachen University on the project IGF16867 N, funded by the Federal Ministry for Economic Affairs and Technology on the basis of a resolution of the German Bundestag, via the AiF within the framework of the program for the promotion of industrial collaborative research and development (IGF); (funding period: 01.01.2011) - RWTH Publications (rwth-aachen.de)".

[0005] To improve machinability, it is known in 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 breakage and thus machinability. Lead is also attributed with a lubricating effect, which positively influences cutting forces, tool temperatures, and tool life.

[0006] Unfortunately, lead is subject to increasingly stringent legal restrictions due to its toxicity. Lead has been classified as a Substance of Very High Concern (SVHC) as soon as a product contains more than 0.1% lead. This applies to jewelry or products intended for the general public, especially if the lead-containing metal could be put in the mouth by children, and the permitted release rate is 0.05 µg / cm³. 2 If the limit is exceeded, lead or its compounds may not be used or placed on the market as soon as the product contains more than 0.05% lead.

[0007] From the field of zinc- and nickel-free copper alloys, for example, a lead-free alloy is known 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 to be disadvantageous; in particular, it has been found that the proposed ratio leads to poor cold formability. Furthermore, the proposed ratio would lead to the formation of eutectic zinc sulfides when zinc is used, which, in addition to poor cold formability, would negatively affect the impact and shock resistance of the material.

[0008] It is therefore the object of the present invention to at least partially overcome the aforementioned disadvantages of known nickel silver alloy systems. In particular, it is the object of the invention to provide a non-toxic alloy system that exhibits excellent machinability, especially improved machinability, while maintaining cold formability.

[0009] The foregoing problem is solved by a nickel silver alloy with the features of independent claim 1, a method with the features of independent method claim, and an apparatus claim with the features of claim 14. Further features and details of the invention will become apparent from the respective dependent claims, 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 and the method according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always makes, or can make, reciprocal references.

[0010] According to the invention, a nickel silver alloy is provided for use in the manufacture of components for the lock and key industry as well as in the jewelry and watchmaking industries. 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 amount to complete the alloy.

[0011] Within the scope of the invention, a nickel silver alloy can preferably be understood to be an alloy comprising the elements copper, nickel, and zinc as its main constituents. Of these main constituents, copper preferably constitutes the component present in the largest quantity. It is understood that, in addition to the aforementioned components or elements, as well as sulfur, manganese, and some optional components, the nickel silver alloy according to the invention may also contain traces of unavoidable impurities, which preferably constitute less than 0.5% (in total) and less than 0.2% (for each element), and in particular less than 0.2% (in total) and less than 0.1% (for each element). A component for use in the jewelry and watchmaking industries can advantageously be understood to include components such as bracelets, chains, straps, clasps, watch movements, wheels, springs, and hands.The stated percentages can also be advantageously understood as mass proportions.

[0012] It should be noted at the outset that the stated proportions of the respective components of the alloy in question preferably refer to the total quantity of 100% or are summed accordingly to 100%. These proportions are given in wt.%.

[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, the lead content can be compensated or substituted, and a healthy alloy system can be provided which exhibits 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 is advantageous according to the invention that copper constitutes the main alloying component, wherein copper is preferably present in the nickel silver alloy in a proportion of > 30%, and in particular in a proportion of > 40%. Particularly preferably, the nickel silver alloy may have a copper content of > 50%, and in particular of > 60%.

[0015] Within the framework of simple and versatile machinability, it is advantageously provided according to the invention that the nickel silver alloy is castable by continuous casting and is cold-workable. Cold workability can preferably be understood as the deformation of a shaped body at room temperature up to a degree of deformation of > 40% without the material cracking or otherwise being damaged. In addition to cold workability, the alloy according to the invention can be particularly suitable for machinability via other manufacturing routes, such as direct casting of parts or semi-finished product production using semi-finished product molds, such as bars, tubes, or wires.

[0016] With regard to ensuring safe use and a robust and stable design of a nickel silver alloy with versatile machinability, it can be advantageous if the alloy is lead-free and / or silicon-free and / or bismuth-free. Avoiding lead is particularly important due to the toxicity of lead compounds. Furthermore, avoiding silicon and bismuth prevents 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 using continuous casting.

[0017] With a view to enabling the most targeted adaptation 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 uncomplicated machinability, it is also advantageously conceivable that the nickel silver alloy has a machinability index of > 50, at least with respect to one of the criteria process force, chip formation, component quality or tool wear, based on the measurement procedure mentioned at the beginning according to the final report of the research project carried out by the WZL.

[0019] In the context of improved, preferably simplified, machinability, in particular via an extrusion process or a cold forming process, it can advantageously further be provided according to the invention 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%.

[0020] In the context of improved, preferably simplified, machinability via extrusion or cold forming processes, it is particularly advantageous that the alloy contains monosulfides, wherein the monosulfides are preferably predominantly in the form of manganese sulfide, and in particular more than 80% in the form of manganese sulfide. The addition of sulfur according to the invention, in combination with the defined manganese content, leads to the suppression of the undesirable zinc-based and / or copper-based sulfides and results in the formation of spheroidal manganese sulfides, which provide the advantageous formability combined with good machinability.

[0021] Accordingly, it can be advantageously provided within the scope of the invention that the monosulfides have a spherical morphology. This advantageously reduces the formation of eutectic Zn-Mn sulfides, which have an embrittlement 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 may 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, it may be provided that the nickel content is 1 to 18%, preferably 5 to 15% and / or the zinc content is 10 to 30%, preferably 15 to 20% and / or the copper content is 40 to 80%, preferably 50 to 70%.

[0024] Advantageously, the nickel silver alloy according to the invention can exhibit improved machinability compared to a single-phase nickel silver alloy (at least with regard to the criterion of process force, i.e., a lower process force to be applied).

[0025] With a view to significantly improving the machinability of the nickel silver alloy in question, it may also be advantageous to include sulfur in the nickel silver alloy at a concentration of 0.05 to 0.5%.

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

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

[0028] The invention also relates to a method for producing a nickel silver alloy, preferably one described above. The method 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 one or more other elements totaling 0.001–5%, and copper as the remaining amount needed to reach 100%, heating the component mixture to fuse the components, and cooling the fused nickel silver alloy. The method according to the invention thus offers the same advantages as those already described in detail with regard to the nickel silver alloy according to the invention and the component described above.It is understood that individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out in the proposed sequence, but also in a different sequence. In particular, individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out repeatedly, e.g., 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 a self-learning manner, in particular by a computer.

[0029] With a view to effectively heating the mixed alloy components for fusing the components, it may also be provided that the alloy is produced via a melt flow process or a sintering process.

[0030] In the context of suitable further processing or treatment of the nickel silver alloy in question for the manufacture 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 being manufactured 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 can each 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 differing from that according to the invention (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 process according to the invention for the production of a nickel silver alloy according to the invention.

[0033] Fig. Figure 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 that differs from the sulfur-manganese ratio according to the invention (left image).

[0034] In particular, the Fig. 1 a metallographic section of a Cu-Ni-Zn alloy according to the invention cast by continuous casting with a proportion 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, 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) shows the formation of rounded or spherical monosulfides, which indicate a cold formability of at least 40% (see markings).

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

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

[0038] Measurements 1 and 2, which differ with respect to the design of a groove produced during machining (Measurement 1: groove width = 1 mm, Measurement 2: groove width = 2 mm), show qualitatively the same picture, namely an increase in the determined machining force, starting with a nickel silver alloy containing 1% lead (nickel silver alloy 1), then with the nickel silver alloy according to the invention containing sulfur (nickel silver alloy 2), and finally with a nickel silver alloy without lead or sulfur (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 for machining a nickel silver alloy according to the invention lies between the process force required for a nickel silver alloy with 1% lead (nickel silver alloy 1) and a nickel silver alloy without lead or sulfur (nickel silver alloy 3).

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

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

[0041] As per Fig.As can be seen from Figure 3, the inventive method comprises the steps of mixing 100 of 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 one or more further elements totaling 0.001 - 5%, and copper as the remaining part missing to a total of 100%, heating 200 of the component mixture to melt the components, and cooling 300 of the fused nickel silver alloy.

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

[0043] Furthermore, the alloy can be further processed after being manufactured using an extrusion process and / or 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 ratios given are to be understood as weight fractions.

[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] Using the nickel silver alloy listed above, it is particularly possible to provide a material that is harmless to health for the production of components for use in the lock and key industry as well as in the jewelry and watch industry, which has easy processing properties, in particular good cold formability and improved machinability. Reference symbol list 100 Mixing the alloy components to produce a component mixture 200 Heating the component mixture to fuse the components 300 Cooling of the fused nickel silver alloy QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 2 625 300 B1

[0007]

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 jewellery and watchmaking industry, comprising: - 1 - 30% nickel, - 8 - 45% zinc, - 0.01 - 1% sulfur, - 0.05 - 5% manganese, - optionally one or more additional elements totalling 0.001 - 5%, - as well as the remaining part of copper missing to reach 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 that the 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 the one or more additional elements optionally contained in the nickel silver alloy in a total of 0.001 - 5% are selected from the group consisting of aluminum, chromium, phosphorus, molybdenum, tungsten, magnesium, zirconium, iron, titanium, calcium, cerium, tellurium. [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 sulphides formed, preferably of < 1% of the volume of the sulphides formed, wherein 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 30% and / or the copper content is 50 - 70%. [12] Nickel silver alloy according to one of the preceding claims, characterized bythat sulfur is contained in the nickel silver alloy at a level of 0.05 to 0.5%. [13] Component made of a nickel silver alloy according to one of the preceding claims for use in the lock and key industry or in the jewellery 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: - Mixing (100) of the following alloy components according to the specified proportions to produce a component mixture: 1 - 30% nickel, 8 - 45% zinc, 0.01 - 1% sulphur, 0.05 - 5% manganese, optionally one or more other elements totalling 0.001 - 5% and copper as the remaining part missing to reach 100%, - heating (200) the component mixture to melt the components, - Cooling (300) of the molten nickel silver alloy. [15] Method according to claim 14, characterized by that the alloy is produced using a fused metal process or a sintering process. [16] Method according to claim 14 or 15, characterized by 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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