EP0568094B1 - Nickel free non-ferrous heavy metal alloy and its use - Google Patents

Abstract

Non-ferrous heavy-metal alloy, nickel-free apart from, at most, 0.09% as a result of smelting, having a composition in per cent by weight of: Mn: more than 5.0 up to 15.00% Al: from 4.0 to 7.50% Fe: from 1.0 to 2.80% B: from 0.0005 to 0.01% Si: from 0.0 to 0.30% Ni: from 0.0 to 0.09% C: from 0.0 to 0.08% S: from 0.0 to 0.03% P: from 0.0 to <0.01% the remainder being copper with impurities due to smelting. Such a copper mixed-crystal alloy is particularly suitable as a material for jewellery and metal objects which, in normal use, are in contact with the skin, especially for spectacle frames and parts of spectacle frames and coins. The alloys according to the invention do not trigger any nickel-caused allergies.

Description

The invention relates essentially to nickel-free non-ferrous metal alloys and their use as a material for jewelry and metal objects which come into contact with human skin during normal use, in particular spectacle frames and parts of spectacle frames.

Nickel-containing materials are used to manufacture eye wires and other parts for eyeglass frames. Examples are the non-ferrous metal alloys listed in Table 1 with corresponding material numbers according to DIN and compositions: Table 1: Non-ferrous metal alloys according to DIN Material number. alloy DIN 2.0730 CuNi 12 Zn 24 17663 2.0740 CuNi 18 Zn 20 17663 2.0842 CuNi 44 Mn 1 17664 2.4110 NiMn 2 17741 2.4360 NiCu 30 Fe 17743 2.4361 LC-NiCu 30 Fe 17743 2.4870 NiCr 10 17742/73

When using such alloys, an allergic reaction to prolonged skin contact can occur due to the nickel content. Similar problems can arise if such nickel-containing alloys are used to manufacture jewelry or metal objects and these are usually worn in close contact with the skin.

The invention is therefore based on the object of providing a material for jewelry and metal objects which come into contact with human skin in normal use and in which the problem of possible allergic reactions does not occur.

Associated with this is the task of providing non-ferrous metal alloys for eyeglass frames and parts of eyeglass frames which, in addition to being tolerated by the skin, have high stability and strength.

This object is achieved according to the invention by a nickel-free or essentially nickel-free non-ferrous metal alloy with the following composition in percent by weight: Mn more than 5.0 to 15.00% Al 4.0 to 7.50% Fe 1.0 to 2.80% B 0.0005 to 0.01% Si 0.0 to 0.30% Ni 0.0 to 0.09% C. 0.0 to 0.08% S 0.0 to 0.03% P 0.0 to <0.01% and copper with remnants of melting-related impurities.

The alloy can be produced by conventional metallurgical processes.

The material and objects made from it, e.g. Glasses and parts of glasses do not cause a nickel allergic reaction if they come into contact with human skin for a long time. This essential condition is met according to the invention by the non-ferrous metal alloy according to claim 1, which is free of nickel up to a maximum of 0.09%. Table 2 shows the nickel emissions of alloys according to the invention determined in the corrosion test.

The alloy according to the invention can be used as a material for the production of jewelry and metal objects which are in contact with the skin under normal use. Examples include earrings and ear studs, necklaces, bracelets and chains, anklets, finger rings, hair clips, watch bottoms, watch straps, chains and clasps, buttons, clasps, rivets, zippers and metal pendants. The alloy according to the invention is also advantageous for coins. In particular, the non-ferrous metal alloy according to the invention is suitable for spectacle frames and parts of spectacle frames.

Materials for eyeglass frames or parts thereof are solidified by cold forming during manufacture. This requires good cold formability. This requirement is met according to the invention in that a homogeneous, in particular single-phase, copper mixed crystal alloy is used due to its chemical composition. Examples of alloys according to the invention are listed in Table 2.

The individual parts are connected to one another in the manufacture of eyeglass frames. Such individual parts are connected, inter alia, by means of welding, preferably resistance welding, but also by other methods which introduce very small amounts of heat into the parts to be connected. The connection can also be carried out by soldering, preferably hard, resistance or high-frequency soldering. The connections can also be glued.

Of great importance for the functional fulfillment of eyeglass frames or eyeglass parts is their stability or rigidity. This is usually achieved through the use of materials that are hardened by forming, preferably work hardened. This work hardening must be maintained even after one of the connection work described above and may only drop slightly at certain points so that the overall stability of the eyeglass frame is achieved.

Surprisingly, it turns out that this essential requirement is met by the eyeglass frames according to the invention and parts of eyeglass frames according to claim 2, and in particular according to claim 3, from a homogeneous, single-phase non-ferrous metal alloy. This phenomenon is of crucial importance, since a homogeneous, single-phase non-ferrous metal alloy cannot be subjected to a strengthening hardening treatment due to the lack of separation options.

The use according to the invention of the homogeneous, single-phase, essentially nickel-free alloy according to claims 1 to 3 also results in an economic advantage in the manufacture of spectacle frames and parts thereof in comparison with two-phase or multiphase non-ferrous metal alloys, due to the elimination of heat treatment. This is because, following connection work, due to a sharp drop in strength in the connection area, these must be subjected to an expensive hardening annealing treatment in order to achieve the strength required for the overall stability of the glasses.

Surprisingly, it was found that the use according to the invention is the economical production of all metallic parts of an eyeglass frame and their connection from a single one Non-ferrous metal alloy according to one of claims 1 to 3 enables.

During manufacture, the spectacle frames or spectacle frame parts are subjected to various surface treatments and / or provided with coatings with nickel-free metallic and non-metallic substances. Such a coating serves to improve the protection of the alloy from atmospheric corrosion and / or to improve the appearance; on the other hand, the coating is not used to protect human skin from nickel-allergic reactions. The surface treatment includes to name polishing and electroplating. The alloys according to the invention meet the requirement of galvanizing and polishing ability.

The following are explanations for limiting the content of the individual alloy elements according to claims 1 to 3:

Pure copper cannot be brought to the strength required for the manufacture of spectacle frames or spectacle parts by cold working. Furthermore, the corrosion resistance for the use mentioned is not sufficient.

Additions of aluminum bring about a significant improvement in corrosion resistance and an increase in strength and hardness through solid solution strengthening. A noticeable improvement in these properties is only achieved with additions above approx. 4%. On the other hand, a content of 7.5% Al in the copper, depending on additional elements, must not be exceeded in order to ensure a single-phase, homogeneous structure in all temperature ranges until the solidus temperature is reached. Above 7.5% Al there is a clear decrease in elongation which is undesirable for the purpose of the invention.

In addition to increasing the tensile strength through solid solution strengthening, additions of iron result in a strong grain refinement of the structure, which has a positive effect on the cold-forming properties. A noticeable improvement in these properties can only be achieved with additions above approx. 1%, while a content of 2.8% Fe to ensure a single-phase, homogeneous structure must not be exceeded.

Manganese additives in the alloys which can be used according to the invention increase the strength properties by solid-solution strengthening both at room temperature and at higher temperatures. Furthermore, they improve the aforementioned cold formability, in particular the homogeneous alpha copper alloys. Manganese additives noticeably improve the weldability.

Of decisive importance for the alloys according to the invention is the fact that the incorporation of manganese atoms in the homogeneous, single-phase alpha-copper lattice greatly increases the recrystallization temperature compared to manganese-free copper and thus achieves an inert recrystallization behavior.

This essential phenomenon is used in the use of the alloy for the manufacture of spectacles or spectacle parts, so that connection work, in particular various soldering and welding processes, can be carried out and so the strength achieved by cold working is largely retained even after this connection work. The metallurgical explanation of only a slight reduction in strength in the heat-affected area of a soldering of cold-worked non-ferrous non-ferrous alloys according to the invention lies in the small temperature difference, ie only a small thermal activation as the driving force of the primary recrystallization, between the working temperature of the soldering process and the high recrystallization temperature of the alloy used.

$$\text{\%Al >= - 0,2 x \%Mn + 7}$$

The limitation of the manganese content to more than 5 to 15% results from the fact that the phenomenon described above only becomes effective with increasing Mn contents above 5%, whereas Mn contents above 15% no longer make any noteworthy contribution, but a significant one Reduce the essential stretch properties. When justifying the limitation of the manganese content to a maximum of 15%, the interaction with aluminum must also be taken into account. Increasing manganese contents reduce the solubility of aluminum in the homogeneous alpha-copper mixed crystal, which, as already described above, is imperative according to the invention. Lowered aluminum contents are known to degrade the strength and corrosion properties. This advantageously results in a scattering range with material and processing properties favorable for the manufacture of spectacles and spectacle parts, which is described for the interaction between manganese and aluminum contents by the following relationships: $$\text{\% Al <= - 0.2 x\% Mn + 8.5}$$

$$\text{\% Al> = - 0.2 x\% Mn + 7}$$

The silicon content is limited according to claim 1 to a maximum of 0.3%, since a higher content in the alloy according to the invention with 5.0 to 15.0% manganese, 4.0 to 7.5% aluminum and 1.0 to 2.8 % Iron lead to excretions and thus no homogeneous alpha-copper mixed crystal would be present. Furthermore, the necessary very good weldability is worsened by higher silicon contents over 0.3%.

The sulfur content is limited to a maximum of 0.03%, while the phosphorus content should be less than 0.01%, since higher contents in mixed copper-crystal alloys lead to hot brittleness and, in particular, significantly impair the required weldability.

An addition of boron in contents of 0.0005 to 0.01% to homogeneous alpha-copper mixed crystal alloys has an advantageous effect in a noticeable improvement in the hot deformability or reduction in the hot brittleness. Furthermore, boron promotes fine grain, which in turn has a positive effect on the cold-forming ability. A limitation to a maximum of 0.010% is intended to avoid the occurrence of undesirable boron deposits.

Corrosion test

According to Danish Legislative Decree No. 472 of June 27, 1989, materials and articles made from them do not cause a nickel allergic reaction if, during a corrosion test, they are made of artificial sweat in a test solution consisting of: Sodium chloride 0.5% by weight Lactic acid 0.1% by weight urea 0.1% by weight water ad 100% by weight PH value 6.5 (adjusted with 2.5% by weight ammonia water) do not release more than 0.5 µg nickel per cm ² and per week. This requirement applies to the material used and the objects made from it in the uncoated and in the coated state.

Four non-ferrous metal alloys (1 to 4) according to the invention and a nickel-containing comparison alloy (5) with the compositions given in Table 2, which is usually used for spectacle frames, were subjected to the corrosion test in accordance with Danish Legislative Decree No. 472. The values for the determined nickel release are shown in Table 2.

The nickel release of the alloys according to the invention is below the required limit of 0.5 µg per cm ² and per week and is significantly lower than the nickel release of the comparison alloy. Table 2: Chemical composition of the test alloys 1 to 4 and the comparative alloy 5 in percent by weight and their nickel release determined in the corrosion test in µg per cm ² and per week: alloy 1 2nd 3rd 4th 5 Mn 5.3 9.2 9.8 14.6 1.1 Al 7.2 6.0 6.1 4.9 0.4 Fe 2.4 1.8 2.1 1.2 2.1 Si 0.07 0.15 0.01 0.05 0.10 Ni 0.14 0.02 0.03 0.01 rest C. 0.027 0.008 0.003 0.049 0.08 S 0.009 0.001 0.002 0.006 0.006 P 0.01 0.02 0.01 0.02 0.02 B 0.001 0.004 0.002 0.009 - Cu rest rest rest rest 32.5 Ni levy 0.48 0.18 0.11 0.15 85.4

Claims (6)

1. Homogeneous, single-phase α-copper mixed crystal alloy, characterised by the following composition in weight per cent: Mn more than 5.0 to 15.00 % Al 4.0 to 7.50 % Fe 1.0 to 2.80 % B 0.0005 to 0.01 % Si 0.0 to 0.30 % Ni 0.0 to 0.09 % C 0.0 to 0.08 % S 0.0 to 0.03 % P 0.0 to <0.01 % and copper with impurities due to smelting as the remainder.
2. Spectacle frame or spectacle frame part, characterised in that it is made from a homogeneous, single-phase α-copper mixed crystal alloy with the following composition in weight per cent: Mn more than 5.0 to 15.00 % Al 4.0 to 7.50 % Fe 1.0 to 2.80 % B 0.0005 to 0.01 % Si 0.0 to 0.30 % Ni 0.0 to 0.09 % C 0.0 to 0.08 % S 0.0 to 0.03 % P 0.0 to <0.01 % and copper with impurities due to smelting as the remainder.
3. Spectacle frame or spectacle frame part according to claim 2, characterised in that the relationships: $$\text{\%Al <= - 0.2 x \%Mn + 8.5}$$

   

   $$\text{\%Al >= - 0.2 x \%Mn + 7}$$

   

   are fulfilled for the material used.
4. Spectacle frame or spectacle frame part according to one of claims 2 to 3, characterised in that the material parts used are joined to one another by welding, soldering and/or bonding.
5. Spectacle frame or spectacle frame part according to one of claims 2 to 4, characterised in that they are coated with nickel-free, metallic and non-metallic materials.
6. Use of an alloy according to claim 1 for producing jewellery and metal objects, particularly spectacle frames and spectacle frame parts as well as coins.