EP2971198B1 - Precious metal alloy for use in the jewellery and watchmaking industry - Google Patents

Description

The invention relates to a use of a noble metal alloy containing palladium and rhodium, for articles of the jewelry and watch industry.

In the jewelery and watch industry, a particularly white metal color of a noble metal alloy is desired, since in this way the gloss of stones, in particular of gemstones such as diamonds, which has a piece of jewelery made from this noble metal alloy, is supported in a particularly good manner. White gold is therefore very often coated with a galvanic rhodium layer, to improve the less white color of white gold or a white gold alloy used to make the jewelry. Rhodium is known to be the precious metal with the best white color. Such an approach is z. B. in the DE 10 2008 050 135 and in the DE 10 2010 026 930 described. The disadvantage of this is not only that in the manufacture of the jewelry made of white gold or white gold alloy, an additional operation - the galvanic Rhodinierung this piece of jewelry - must be performed. It is more important for a buyer of such a manufactured piece of jewelry that galvanically applied rhodium layers are subjected to natural wear during use of the piece of jewelry, so that after a certain wearing time the rhodium coating of the piece of jewelry must be renewed, as by their wear the less white color of the base material of the jewel, that is, the white gold alloy, has become visible.

To make a piece of jewelry made of rhodium or a rhodium alloy as a massive alloy is impractical because rhodium very brittle and therefore for the production of jewelry such as jewelry, jewelry, watch cases, writing instruments, etc. not or at least not sufficiently suitable platinum and high-alloy platinum alloys such as an alloy with 95 wt.% platinum have a sufficiently white color for most of the applications occurring in the jewelery and watch industry and are generally considered to be of particular value since platinum is the highest metal price precious metal. Palladium is a white precious metal with the lowest Reflectance of light and therefore acts gray compared to platinum alloys. For this reason, palladium is currently used only for selected applications in the jewelry and watch industry where it does not or does not respond to an "ideal white" color of a product made from palladium or a palladium alloy primary arrives, used. Palladium not only has the advantage over platinum that it is about 40% lighter than this precious metal. Rather, the metal price of palladium is significantly lower than that of platinum. The two aforementioned advantages can be due to the disadvantageous color described above - palladium acts gray - use only inadequate in the jewelry and watch industry.

From the DE 1 086 442 B is the use of a palladium-rhodium alloy known as a material for spinnerets. The alloy used for this purpose has 25% to 50%, in particular 25% to 42% rhodium and the balance palladium. Up to 15%, preferably up to 10%, and in particular less than 5%, of the palladium may be replaced by other platinum metals, gold, silver, iron. Cobalt, nickel, copper and / or manganese are replaced, wherein the content of base metals should not exceed 3%, with the proviso that up to a rhodium content of 30%, the iridium content is <7%. The properties which characterize the abovementioned alloys for use as material for spinnerets are that these alloys, even in the heat-treated state, still have a certain elongation, so that the risk of cracking due to embrittlement is largely eliminated.

From the DE 1 080 785 B is the use of a palladium-rhodium alloy as a material for electrical contacts and potentiometers known. The alloy to be used here consists of 5% to 45%, preferably 15% to 40% rhodium and the remainder palladium. The alloy may contain up to 15%, preferably up to 5%, of one or more other platinum metals, gold, silver, nickel, cobalt or copper, provided that in the presence of iridium the iridium content is less than 10%. The properties of these alloys are particularly distinguished for the production of electrical contacts and potentiometers, that the hardness and closing strength is maintained even if a mechanical stress occurs at a contact. In addition, these alloys should can be produced with high uniformity and always have a constant contact resistance; Their use is according to the information in the aforementioned document then particularly advantageous if absolute switching reliability and uniform electrical conditions, a constancy of the output resistance at the contact point and the lowest possible contact migration when opening the contact points of the electrical contact or the potentiometer made therefrom is required.

From the EP 2 420 583 A2 Applicant is aware of an ideal white, tarnish-resistant precious metal jewelery alloy comprising rhodium at 40 weight percent to 70 weight percent and platinum at 60 weight percent to 30 weight percent, wherein the weight fraction of platinum and the weight ratio of rhodium in the Substantially add up to 100% by weight. The above-mentioned document also describes the use of this rhodium-platinum alloy for producing a piece of jewelry such as a watch, jewelry, a jewelery article or a writing instrument.

From the EP 1 548 135 A1 For example, an alloy for use in the high-temperature range is known, in particular for gas turbines, aircraft drives and devices for generating energy. The alloy described therein comprises at least 50 atomic percent rhodium and up to 49 atomic percent of a first material consisting of at least one of palladium, platinum, iridium or a combination thereof and between 1 atomic percent and 15 atomic percent of a second material selected from the elements , Tungsten, rhenium or a combination thereof, and up to 10 atomic percent of a third material consisting of chromium or mixtures thereof, said alloy having an A1 structured phase at temperatures> 1000 ° C in an amount of at least 90 percent by volume ,

From the DE 10 2004 024 026 A1 For example, a catalyst for N ₂ O decomposition in the Ostwald process is known which has a support and a rhodium, rhodium / palladium or rhodium oxide coating applied thereto.

The DE 38 12 565 C1 describes the use of castable palladium alloys in dental technology. The alloys used herein comprise 60 weight percent to 99.5 weight percent palladium, 0.5 weight percent to 40 weight percent iridium and 0 weight percent to 25 weight percent ruthenium and / or rhodium.

It is an object of the present invention, a palladium-based alloy for use in the jewelry and watch industry for the production of jewelry such as jewelry, jewelry, jewelry or writing instruments, as well as watches, watch cases and components of the aforementioned goods to provide a comparison to pure or high-alloyed palladium "white" color possesses.

This object is achieved by the use of a noble metal alloy, which provides that the precious metal alloy used in a proportion of 40-60 wt .-% rhodium and in a proportion of 40-60 wt .-%, and that the noble metal alloy is preferably gold, platinum, ruthenium and / or iridium in an amount of between more than 0 to 10 wt .-%, preferably in a proportion of between 2 wt .-% and 5 wt .-%, more preferably in one Proportion of 3 wt .-%, in which case the corresponding proportion of rhodium and / or palladium is replaced by the aforementioned secondary alloy components, and wherein the proportions of rhodium and palladium and the preferably provided above-mentioned secondary alloy components, of conventional impurities and admixtures except for 100% by weight supplement.

The precious metal alloy described above is particularly suitable for use in the jewelry and watch industry because it has a white color with that of rhodium or a rhodium coating, or at least which is comparable to platinum or platinum alloys. Therefore, the precious metal alloy is particularly bright in an advantageous manner and is therefore particularly suitable for the production of jewelry, in particular jewelry that have gems such as diamonds. Since the precious metal alloy used according to the invention - since it is produced metallurgically and not just a coating - this color itself, it is no longer necessary for the production of jewelry their color by a further treatment step, such. As a galvanic rhodium, to improve.

Another advantage of the noble metal alloy used in the invention is that it is significantly lighter in weight than a platinum alloy of the same or comparable white color, and that it is much cheaper to produce than such a platinum alloy, since - as already stated above - the Metal price of rhodium and palladium is significantly lower than that of platinum.

The noble metal alloy used according to the invention has a hardness soft in the range of 180-200 HV and is therefore particularly well suited for the production of a piece of jewelry by means of a hot deformation. It has a hardness hard in the range of more than 250 HV, preferably more than 300 HV, and is therefore characterized by a good wear resistance. The pieces of jewelery produced from the precious metal alloy used according to the invention are therefore distinguished by the fact that their glossy surface is retained for a long time.

An advantageous development of the invention provides that the precious metal alloy palladium used according to the invention contains from 47 to 53% by weight and rhodium contains from 53 to 47% by weight, the proportions of rhodium and palladium and of supplement the aforementioned impurities and admixtures to 100 wt .-%. Such Measure has the advantage of an even whiter color of the noble metal alloy according to the invention.

A further advantageous embodiment of the invention provides that the precious metal alloy used according to the invention comprises 50-52% by weight of palladium and 50-48% by weight of rhodium, wherein the abovementioned proportions of palladium and rhodium - of the aforementioned impurities and admixtures apart - supplement to 100 wt .-%.

A further advantageous development of the invention provides that the noble metal alloy used according to the invention comprises 50% by weight of palladium and 50% by weight of rhodium, these two proportions of palladium and rhodium, apart from the aforementioned impurities and admixtures, being 100% Add% by weight.

A further advantageous development of the invention provides that the noble metal alloy according to the invention has 47-50% by weight of palladium and 53-50% by weight of rhodium, the proportions of palladium and rhodium, apart from the aforementioned impurities and admixtures, to 100 wt .-% complete.

A further advantageous embodiment of the invention provides that the alloy according to the invention contains gold, platinum, ruthenium and / or iridium in a proportion of more than zero and not more than 10% by weight, preferably 2% by weight to 5% by weight, more preferably 3% by weight, with the proportions of rhodium and palladium and the abovementioned secondary alloying components being added to 100% by weight, and the secondary alloying components preferably replacing the corresponding proportion of rhodium.

Further advantages and developments of the invention are the subject of the dependent claims.

Further details and advantages of the invention can be found in the exemplary embodiments which are described below.

The first embodiment of the described noble metal alloy comprises 40-60 wt .-% palladium and 60-40 wt .-% rhodium, wherein the aforementioned proportions of palladium and rhodium to 100 wt .-% complement, if one of the usual Disregards impurities and admixtures of these metals. It is not necessary for a person skilled in the art to explain that the abovementioned proportions by weight and also the proportions by weight of the following exemplary embodiments are to be understood to include the usual tolerances occurring in a metallurgical production process.

The precious metal alloy described has a yellowness index YI in the range of 9 to 10. Such a yellowness index Yl of less than 10 is considered to be very low for such noble metal alloys and is generally only achieved by rhodium itself or a rhodium-platinum alloy.

The brightness value (L * value) of the described alloy lies in the range between 86 and 88, which is surprising since the L * value is significantly higher than for the pure noble metals palladium or rhodium: rhodium has an L * value of 83.8 and palladium one from 81.1 up. The precious metal alloy described therefore, in an advantageous manner, has a very bright appearance, that is to say has a very white color, which is at the level of platinum alloy with 95% by weight of platinum. The described precious metal alloy is therefore visually hardly distinguishable from rhodium, a rhodium layer applied galvanically on a base material, a rhodium-platinum alloy, or at least platinum or a platinum alloy with 95% by weight platinum, but is advantageously and Way cheaper to produce.

The values listed above were determined by measurements and the standard conditions defined by DIN 5033. The further values of the L * a * b * color space are in the range of 0.7 <= a * <= 0.9 and 3.5 <= b * <= 4 for the exemplary embodiment described.

A second exemplary embodiment of the noble metal alloy provides that the noble metal alloy contains 53-47% by weight of palladium and 47-53% by weight of rhodium, the abovementioned proportions taking into account unavoidable impurities and admixtures as well as the corresponding metallological tolerance limits to 100 wt .-% complete. Such an alloy has an L * value in the range of 87.3 and a yellowness index Yl in the range of 9.7. The color parameters a * and b * are approximately 0.8 and 3.8, respectively.

A third embodiment of the noble metal alloy provides that the precious metal alloy 52-50 wt .-% palladium and 48-50 wt .-% rhodium, wherein the proportions of palladium and rhodium - of conventional admixtures and impurities and alloy tolerances apart - supplement to 100 wt .-%. Such an alloy has a yellowness index Yl of 9.8, an L * value of 87.3. The color parameters a * and b * are 0.8 and 3.8, respectively.

A fourth exemplary embodiment of the noble metal alloy provides that it contains 50% by weight of palladium and 50% by weight of rhodium, with the proportions of palladium and rhodium, apart from customary admixtures and impurities and alloy tolerances, being 100% by weight. % complete. Such an alloy has a yellowness index YI in the range of 9.8. The brightness L * is in the range of 87.3 and the color parameters a * and b * are 0.8 and 3.8, respectively.

A fifth embodiment of the noble metal alloy provides that the noble metal alloy contains 47-50% by weight of palladium and 53-50% by weight of rhodium, wherein the proportions of rhodium and palladium - apart from conventional admixtures and impurities and alloy tolerances - add up to 100 wt .-%. Such a noble metal alloy has a yellowness index Yl in the range of 9.8. The brightness L * is in the range of 87.4 and the color parameters a * and b * are 0.9 and 3.7, respectively.

A sixth embodiment of the noble metal alloy provides that the noble metal alloy 40 wt .-% palladium and 60 wt .-% rhodium, wherein the proportions of rhodium and palladium - apart from conventional admixtures and impurities and alloy tolerances - to 100 Add% by weight. Such an alloy has a yellowness index YI in the range of 9.0. The brightness L * is in the range of 87.1 and the color parameters a * and b * are 0.8 and 3.5, respectively.

Preferred among the abovementioned noble metal alloys is that of the fourth exemplary embodiment, that is to say an alloy which has a weight fraction of 50% by weight of palladium and 50% by weight of rhodium. As can be seen from the color parameters detailed above, this has a yellow-blue value b * of 3.8 which is close to the arithmetic mean of the corresponding b * values of rhodium (b * = 2.8) and palladium (b * = 6.0). The green-red value a * of the alloy of the fourth embodiment is slightly higher than the arithmetic mean of the primary alloy components of this alloy; Rhodium has an a * value of a * = 0.6 and palladium has a value of a * = 0.4. The green-red value a * of the alloy of the fourth embodiment is about 0.8, but is still substantially close to zero and therefore still negligible.

Surprisingly, it has been found that the brightness value L * of the described alloys, in particular the alloy of the fourth embodiment with L * = 87.3, is significantly higher than that of the pure materials. Palladium has a brightness L * of 81.1 and a yellowness index Yl of 13.6.

The corresponding values of rhodium are L * = 83.8 and Yl = 6.8. The L * value of the alloy of the fourth embodiment is L * = 87.3 at the level of a 95% platinum alloy, whereby this alloy is very bright, which also results from the yellowness index of Yl = 9.8 , As a result, in particular, the noble metal alloy according to the fourth embodiment can hardly be visually distinguished from rhodium, a galvanic rhodium layer, a rhodium-platinum alloy or at least platinum or a high-alloy platinum alloy such as Pt 950.

It is preferred that the noble metal alloys described above gold, platinum, ruthenium and / or iridium in an amount of more than 0 wt .-% and at most 10 wt .-% is added as a secondary alloy components, wherein the proportions of rhodium and palladium and those of the secondary alloy components to 100 wt .-% complete, apart from conventional admixtures and impurities and alloying tolerances. Such a measure has the advantage that the cast structure of such a noble metal alloy has a finer microstructure.

In the preparation of the aforementioned gold, platinum, ruthenium and / or rhodium-containing precious metal alloy of an alloy according to one of the first five embodiments, it is preferably provided that the corresponding proportion of rhodium is replaced by the proportion of the abovementioned secondary alloy components added to these alloys , But it is also possible that not rhodium, but palladium is replaced. Likewise, a combination of the two aforementioned measures, namely that the corresponding proportions of rhodium and palladium are replaced by the abovementioned secondary alloy components, is possible.

Surprisingly, it has been found that the precious metal alloys described are very well suited for jewelry casting by the lost wax process, with conventional equipment and investment materials for the casting of Precious metal alloys can be used. The castings made from the described alloys have essentially no or only a low porosity. They have a hardness in the range of 180-200 HV. This large molding hardness has the advantage that for the production of jewelry finished molds can be cast and their hardness does not have to be subsequently improved by deformation of a variety of applications.

Another advantage of the precious metal alloys described is that surface defects were virtually not observed by reactions with an investment. The unexpectedly low solidification shrinkage of the precious metal alloys described compared to other jewelry materials such as platinum 950 or white gold 750 reduces the risk of shrinkage porosity, which is a major problem in jewelry casting.

Another advantage of the described noble metal alloys is that gas and / or embedding mass reactions are almost excluded since both rhodium and palladium have a high chemical resistance. This also implies that re-pouring of residues of the described noble metal-precious metal alloys without much difficulty is feasible, since these described precious metal alloys are not affected by chemical reactions in Schmuckguß process. This thereby given reusability of remnants of the casting process leads to a good material utilization.

Another advantage of the precious metal alloys described is in connection with the jewelery casting, that castings produced by such a jewelery casting have close to the final dimensions, which in conjunction with a good Wiedervergießbarkeit brings an economical use of materials with it.

The cast hardness of the alloys described in the range of 180-200 HV, in particular 190 HV, has the advantage that these alloys can best be processed by means of a hot forming process, for which a temperature above the miscibility gap at about 845 ° C is suitable , Particularly suitable is a temperature of 1200-1300 ° C. The advantage is that at such a temperature still hammering or rolling is possible, with deformations of up to 10% per forming step is possible.

After the hot deformation and a consequent transformation of the cast structure, cold working with machines such as are commonly used in precious metal processing is also possible. The solution-annealed state (annealing at 1000 ° C and subsequent quenching) has a hardness of 130 HV to 140 HV. By cold working hardening greater than 250 HV, preferably greater than 300 HV can be achieved. The high hardness of the described precious metal alloys provides good wear resistance and thereby provides a good preservation of a gloss surface of a jewelry made of the described alloys such as a piece of jewelry, a clock of a watch case, a writing instrument, jewelry, jewelry or the like, as well as Components of the aforementioned articles.

Claims (8)

1. Use of a precious metal alloy, comprising palladium and rhodium, for manufacturing pieces like jewelry, jewelry articles, bijouterie, watches and watch cases and/or writing utensils and/or a component thereof, characterized in that the used precious metal alloy comprises palladium in an amount of 40-60% by weight and rhodium in an amount of 40-60% by weight, and that the used precious metal alloy preferably comprises gold, platinum, ruthenium and/or iridium in an amount between greater than 0 to 10% by weight, preferably in an amount between 2% by weight and 5% by weight, more preferably in an amount of 3% by weight, wherein by the aforementioned secondary alloy components the corresponding amount of rhodium and/or palladium is replaced, and wherein the amounts of rhodium and palladium as well as of the preferably provided aforementioned secondary alloy components complement, apart from usual admixtures and impurities, to 100% by weight.
2. Use of the precious metal alloy according to claim 1, characterized in that the precious metal alloy comprises palladium in an amount of 53-47% by weight and rhodium in an amount of 47-53% by weight.
3. Use of the precious metal alloy according to one of the preceding claims, characterized in that the precious metal alloy comprises palladium in an amount of 52-50% by weight and rhodium in an amount of 48-50% by weight.
4. Use of the precious metal alloy according to one of the preceding claims, characterized in that the precious metal alloy comprises palladium in an amount of 50% by weight and rhodium in an amount of 50% by weight.
5. Use of the precious metal alloy according to one of the preceding claims, characterized in that the precious metal alloy comprises palladium in an amount of 47-50% by weight and rhodium in an amount of 53-50% by weight.
6. Use of the precious metal alloy according to one of the preceding claims, characterized in that the precious metal alloy comprises palladium in an amount of 40% by weight and rhodium in an amount of 60% by weight.
7. Article like jewelry, jewelry article, bijouterie, watch, watch case and/or writing utensil as well as a component thereof, characterized in that the article is made of a precious metal alloy comprising palladium in an amount of 40-60% by weight and rhodium in an amount of 60-40% by weight, and that the used precious metal alloy comprises preferably gold, platinum, ruthenium and/or iridium in an amount of between greater than 0 and 10% by weight - preferably in an amount between 2% by weight and 5% by weight, more preferably in an amount of 3% by weight, wherein by the aforementioned secondary alloy components the corresponding amount of rhodium and/or palladium is replaced, and wherein the amounts of rhodium and palladium as well as of the preferably provided aforementioned secondary alloy components complement, apart from usual admixtures and impurities, to 100% by weight.
8. Jewelry piece like jewelry, jewelry article, bijouterie, watch, watch case and/or writing utensil as well as a component thereof according to claim 7, characterized in that the aforementioned goods and/or a respective component thereof is manufactured from a solid alloy.