CN1961092A - Process for making finished or semi-finished articles of silver alloy comprising copper and germanium - Google Patents

Abstract

A method of producing a silver alloy finished or semi-finished product, said method comprising the steps of providing a silver alloy comprising at least 77% by weight of silver, copper and at least 0.5% by weight of germanium in an amount effective to reduce tarnish and/or or fire spotting; preparing or treating alloyed finished or semi-finished articles by heating at least to the annealing temperature; gradually cooling the article to ambient temperature; and reheating the article to induce precipitation hardening thereof. The avoidance of quenching reduces the risk of product damage.

Description

Process for producing silver alloy finished or semi-finished products comprising copper and germanium

technical field

The present invention relates to a process for the preparation of finished or semi-finished silver alloy articles and to the articles obtained by said method.

Background technique

Molten silver and copper are completely miscible in any proportion. However, alloys with about 2-27% copper content, when solidified and viewed under a microscope, show two separate components: one is nearly 100% silver; the other has a melting point of 1435 F (780 C) of silver-copper "eutectic" (71.9% silver; 28.1% copper). When the sterling silver is cooled, microscopic analysis shows the presence of both components mentioned above in the solidified sterling silver. The alloy is completely liquid at 1640°F (890°C) and completely solid at 1435°F (780°C). However, the extent to which copper dissolves in the solid alloy depends on the heat treatment used, and all physical properties of sterling silver can be significantly affected by heating the silver to different temperatures as well as by using different cooling rates.

Silver alloys are usually supplied in a soft state for easy processing. Heat treatment can be used to increase hardness (and reduce ductility). The so-called precipitation hardening process involves heating and cooling silver in such a way as to precipitate copper out of solid solution, thereby producing a fine binary structure. This structure is hard, but also difficult to machine and has a tendency to crack. Precipitation hardening of conventional Stirling silver can be achieved by (a) heating the alloy to 775°C or above, (b) holding the alloy at this temperature for 15-30 minutes to anneal (i.e., dissolve any copper in the silver ), (c) rapid quenching in cold water, which prevents the formation of Cu-rich coarse precipitates that are ineffective in inducing hardening, (d) rehardening the softened alloy by heating to, for example, 300°C for 30-60 minutes results in the formation of very fine Cu-rich particles that are effective in inducing hardening, and (e) air cooling. The annealing temperatures involved are very high and close to the melting onset temperature. In addition, in actual production, silversmiths are rarely able to safely quench products that are close to the finished product, because there is a risk of deformation of the produced product and/or damage to the welded joints. Silversmiths therefore believed that the precipitation hardening of Sterling silver was only important in metallurgy. Commercial or industrial production of jewelry, silver plates, dimples, etc. is very difficult (see Fischer-Buhner, "An Update on Hardening of Sterling Silver Alloys by Heat Treatment", Proceedings, Santa Fe Symposium on Jewelery Manufacturing Technology, 2003, 20 -47 at p.29) and is not necessary, since sterling silver is usually produced with a Vickers hardness of 70 or above. Higher Vickers alloys are obtained by work hardening rather than precipitation hardening.

Patent GB-B-2255348 (Rateau, Albert and Johns; MetaleuropRecherche) discloses a novel silver alloy which maintains the inherent hardness and luster of the Ag-Cu alloy while reducing the problems caused by the tendency of the copper content to oxidize performance. The alloy is an Ag-Cu-Ge ternary alloy comprising at least 92.5% by weight Ag, 0.5-3% by weight Ge and the balance copper excluding impurities. The alloy is resistant to rusting in ambient air during normal production, shipping and finishing operations, deforms easily in the cold state, is readily brazed and does not shrink significantly when cast. They also exhibit excellent ductility and tensile strength. Germanium is said to play a protective role, which is why the new alloy exhibits a favorable combination of properties, with germanium in solid solution in both the silver and copper phases. The alloy's microstructure is said to consist of two phases, a solid solution of germanium and copper in silver surrounded by filamentous solid solutions of germanium and silver in copper (which itself contains a small dispersion of the intermetallic CuGe phase). Germanium in the copper-rich phase is said to inhibit surface oxidation of this phase by forming a thin GeO and/or _GeO2 protective coating that prevents firestains during brazing and flame annealing. In addition, the addition of germanium significantly retards the spread of tarnish, the surface turns yellowish rather than black, and the tarnish products are easily removed with ordinary tap water. The reason for this is that increased hardness is obtained by detensioning the alloy, e.g. heating to 500°C and then heating the alloy to a "low annealing" temperature below 400°C, e.g. heating to 200°C for 2 hours to provide a Vickers of about 140 hardness. However, it is not suggested that such hardness can be obtained without a step of heating to annealing temperature followed by quenching, and therefore it is not suggested that an increased hardness can be obtained in the near-fabricated workpiece.

Patent US-A-6168071 and EP-B-0729398 (Johns) disclose a kind of silver/germanium alloy, and its silver content is at least 77% by weight, and germanium content is 0.4-7%, and all the other is mainly copper except impurity, and this The alloy contains elemental boron as a grain refiner at a concentration greater than 0 ppm and less than 20 ppm. The boron content of the alloy can be obtained by providing boron in a copper/boron master alloy containing 2% by weight of elemental boron. This low concentration of boron is reported to unexpectedly provide excellent grain refinement in silver/germanium alloys, endowing the alloy with greater strength and ductility than silver/germanium alloys without boron. The boron in the alloy inhibits grain growth even at temperatures used for welding in the jewelry industry, and samples of the alloy have been reported to be resistant to pitting even when repeatedly heated to the temperature at which the copper/germanium eutectic in conventional alloys melts performance. Strong and aesthetically pleasing joints between discrete alloy elements can be obtained without the use of filler material between the free surfaces of the two elements, and butt or lap joints can be formed by diffusion methods or resistance or laser welding techniques. Welds in the above alloys have a much smaller average grain size compared to welds with sterling silver, resulting in improved weld formability and ductility, and alloy 830 has been welded by plasma welding and Polish without grinding. There is still no disclosure or suggestion that precipitation hardening can be achieved in close proximity to the finished workpiece.

Argentium (trademark) sterling silver contains Ag 92.5% by weight and Ge 1.2% by weight, the balance copper and about 4 ppm boron as a grain refiner. The Society of American Silversmiths maintains a website at http://www.silversmithing.com/largentium.htm for a commercial implementation of the above alloy known as Argentium (trademark). It is disclosed that Argentium sterling silver is precipitation hardenable (i.e., by heating to annealing temperature and quenching), by reheating to a temperature obtainable in a domestic oven, such as 450°F (232°C) for about 2 hours or At 570°F (299°C) for about 30 minutes, twice the final hardness can be achieved. It is further disclosed that the hard alloy can be softened by conventional annealing (ie heating to annealing temperature and quenching) and then hardened again if desired. However, it is not mentioned that precipitation hardening is suitable for near-fabricated workpieces and can solve the problems of deformation and damage of welded joints.

US-A-6726877 (Eccles) specifically discloses a allegedly resistant firescale, work-hardenable jewelry silver alloy composition comprising 81-95.409 wt% Ag, 0.5-6 wt% Cu, 0.05-5 % by weight Zn, 0.02-2% by weight Si, 0.01-2% by weight B, 0.01-1.5% by weight In, and 0.01 to not more than 2.0% by weight Ge. The germanium content is said to give the alloy the work-hardening properties exhibited by conventional 0.925 silver alloys, along with the fire-spot resistance of what was known before June 1994 as a supposedly fire-spot alloy. Amounts of Ge in the alloy of about 0.04-2.0 wt% are said to provide improved work hardening properties relative to refractory alloys not containing germanium, but the hardening properties are neither linear with the increase of germanium nor with the degree of processing. The Zn content in the alloy is related to the color of the alloy and acts as a reducing agent for silver and copper oxides, and is preferably 2.0-4.0% by weight. The Si content in the alloy is preferably adjusted relative to the Zn ratio used, and is preferably 0.15-0.2% by weight. Precipitation hardening after annealing is not disclosed, nor is it disclosed or mentioned that deformation and weld joint damage in near-finished workpieces made of this alloy can be avoided.

As background, US-A-4810308 (Leach & Garner) discloses a hardenable silver alloy comprising not less than 90% silver; not less than 2.0% copper; and at least one element selected from the group consisting of lithium, tin and antimony Metal. The silver alloy may also contain up to 0.5% by weight of bismuth. Preferably, the metals making up the alloy are mixed and heated to a temperature not lower than 1250-1400°F (676-760°C) for, for example, about 2 hours to anneal the alloy into a solid solution, in the examples 1350°F ( 732°C). The annealed alloy is then rapidly cooled to ambient temperature by quenching. Age hardening may then be performed by reheating to 300-700°F (149-371°C) for a predetermined period of time, followed by cooling the age-hardened alloy to ambient temperature. The age-hardenable alloy exhibits a hardness significantly higher than conventional sterling silver, typically 100 HVN (Vickers Hardness Number), and can be returned to a relatively soft state by high temperatures. The disclosure of US-A-4869757 (Leach & Garner) is similar. In both cases, the annealing temperatures disclosed are higher than those of Argentium, and neither reference discloses alloys that are resistant to fire staining or tarnish. The inventors are aware that the methods disclosed in these patents are not used in commercial production, nor does it disclose or mention that hardening can be achieved in close proximity to the finished workpiece.

US-A-05817195 and 5882441 are said to relate to a silver alloy called Steralite which exhibits high tarnish and corrosion resistance. The alloy of US-A-5817195 (Davitz) contains 90-92.5 wt% Ag, 5.75-5.5 wt% Zn, 0.25-less than 1 wt% Cu, 0.25-0.5 wt% Ni, 0.1-0.25 wt% Si and 0.0- 0.5% by weight In. The alloy of US-A-5882441 (Davitz) contains 90-94 wt% Ag, 3.5-7.35 wt% Zn, 1-3 wt% Cu and 0.1-2.5 wt% Si. A similar high zinc low copper alloy is disclosed in US-A-4973446 (Bernhard) which is said to have reduced firespot, reduced porosity and reduced grain size. None of these references address annealing or precipitation hardening.

Contents of the invention

We have now found that products of useful hardness can be obtained by hardening Ag-Cu-Ge alloy workpieces heated to the annealing temperature by gradual cooling followed by moderate reheating to produce precipitation hardening. Typically, reheating is carried out, for example to 180-350°C, and preferably 250-300°C for precipitation hardening. Remarkably, it has been found that overaging of Ag-Cu-Ge alloys during precipitation hardening does not cause a significant decrease in the resulting hardness. New methods of processing workpieces can be applied, e.g. as part of welding or annealing in a mesh belt conveyor furnace or in investment casting, eliminating the need for Ag-Cu sterling silver and possible as described above Quenching such as water, which causes deformation or product damage, can therefore be used close to the finished workpiece. This method can be used for alloys of the general type disclosed in GB-B-2255348. It is believed that this method can also be used for some or all of the alloys disclosed in US-A-6726877, including alloys with relatively high germanium content and alloys with lower germanium content as well as alloys with relatively high zinc and silicon contents.

The invention provides a method for preparing silver alloy finished or semi-finished products, the method comprising the steps of:

providing a silver alloy comprising at least 77% by weight silver, copper and at least 0.5% by weight germanium, the germanium content being effective to reduce tarnishing and/or fire spot;

preparing or treating finished or semi-finished articles of said alloy by heating to at least the annealing temperature;

Gradually cool the article to ambient temperature; and

The article is heated again to induce its precipitation hardening.

The method described above is based on the difference in properties between conventional Stirling silver alloys on the one hand and other Ag-Cu binary alloys and on the other hand Ag-Cu-Ge alloys, where gradual cooling of the binary Stirling-silver type alloys produces Coarse precipitates and only limited precipitation hardening, whereas gradual cooling of Ag-Cu-Ge alloys produces fine precipitates and effective precipitation hardening, especially when the alloy contains an effective amount of grain refiner. Gradual cooling includes avoiding any abrupt cooling steps, such as dropping the article into water or other cooling liquid, and generally means cooling to ambient temperature over a period of more than 10 seconds, preferably more than 15 seconds. Control can be achieved by gradual cooling during the mesh belt furnace process of workpieces to be brazed and/or annealed as they move towards the discharge end of the furnace. Controlling the rate of heat loss through the low conductivity investment material of the mold box can also be achieved during investment casting if the workpiece being cast is allowed to air cool to ambient temperature.

When applied to alloy finished products or semi-finished products disclosed in US6726877, the method includes the following steps:

Silver alloys are provided comprising at least 86% by weight Ag, 0.5-7.5% by weight Cu, 0.07-6% by weight Zn and a mixture of Si, wherein the content of Si is about 0.02% by weight to about 2.0% by weight, and about 0.01% by weight Up to not more than 3.0 wt. % Ge (preferably not more than 2.0 wt. % Ge).

Manufactures or semi-manufactures of alloys prepared or treated by heating to at least the annealing temperature;

gradually cooling the product; and

The article is heated again to induce its precipitation hardening.

Detailed ways

Alloys that can be used in the above method

Alloys that may be treated in accordance with the present invention include alloys containing at least 77% by weight silver containing copper and an amount of germanium effective to reduce firespotting and/or tarnishing. The inventors believe that 0.5% by weight of Ge provides a preferred lower limit, and that less than 1% by weight is practically undesirable, with amounts of 1-1.5% by weight being preferred.

Ternary Ag-Cu-Ge alloys and quaternary Ag-Cu-Zn-Ge alloys suitable for treatment by the method of the invention have a silver content of preferably at least 80% by weight, and most preferably at least 92.5% by weight, up to not more than 98% by weight %, preferably no more than 97% by weight of the alloy. The germanium content of the Ag-Cu-(Zn)-Ge alloy should be at least 0.5%, more preferably at least 1.1%, and most preferably at least 1.5%, most preferably no more than 3%, based on the weight of the alloy. The main alloying components that can be used to replace (in addition to zinc) copper are Au, Pd and Pt. Other alloying components may be selected from Al, Ba, Be, Cd, Co, Cr, Er, Ga, In, Mg, Mn, Ni, Pb, Si, Sn, Ti, V, Y, Yb and Zr, assuming that germanium is not Provides resistance to firespot and tarnishing effects without undue detrimental effects. The weight ratio of germanium to incidental constituent elements may range from 100:0 to 60:40, preferably from 100:0 to 80:20. Currently commercially available Ag-Cu-Ge alloys such as Argentium do not add incidental components.

The remainder of the ternary Ag-Cu-Ge alloy, excluding impurities, incidental constituents and any grain refiners, consists of copper in an amount of at least 0.5%, preferably at least 1%, more preferably at least 2%, and most preferably at least 4%. For '800 grade' ternary alloys, for example, a copper content of 18.5% is suitable. It has been found that in the absence of both copper and germanium no hardening on reheating may be observed.

The remainder of the quaternary Ag-Cu-Zn-Ge alloy, excluding impurities and any grain refiner, will consist of copper and zinc, the copper content should be at least 0.5%, preferably at least 1%, and more based on the weight of the alloy. Preferably at least 2%, and most preferably at least 4%, and the weight ratio of zinc to copper should not be greater than 1:1. Thus, zinc can optionally be present in the silver-copper alloy at 0 to 100% by weight of the copper content. For '800 grade' quaternary alloys eg a copper content of 10.5% and a zinc content of 8% is suitable.

In addition to silver, copper and germanium, and optionally zinc, the alloy preferably contains grain refiners to inhibit grain growth during alloy processing. Suitable grain refiners include boron, iridium, iron and nickel, with boron being particularly preferred. The content of the grain refiner, preferably boron, in the Ag-Cu-(Zn)-Ge alloy may be 1 ppm to 100 ppm, preferably 2 ppm to 50 ppm, more preferably 4 ppm to 20 ppm, based on the weight of the alloy, and is very typically Boron 1-10ppm, for example 4-7ppm.

In a preferred embodiment, the alloy is a ternary alloy consisting of 80%-96% silver, 0.1%-5% germanium, and 1%-19.9% copper, by weight of the alloy, excluding impurities and any grain refiners. alloy. In a more preferred embodiment, the composition of the alloy is 92.5%-98% silver, 0.3%-3% germanium and 1%-7.2% copper and A ternary alloy of 1ppm-40ppm boron as a grain refiner. In an even more preferred embodiment, the composition of the alloy is 92.5%-96% silver, 0.9%-2% germanium and 1%-7% copper by weight of the alloy excluding impurities and grain refiners And a ternary alloy of 1ppm-40ppm boron as a grain refiner. A particularly preferred ternary alloy is that sold under the name Argentium, which contains 92.5-92.7% by weight Ag, 6.1-6.3% by weight Cu and about 1.2% by weight Ge.

As mentioned above, the alloy disclosed in US 6726877 comprises at least 86% by weight Ag; 0.5-7.5% by weight Cu; and about 0.01 to no more than 3.0 wt. % Ge, preferably no more than 2.0 wt. % Ge. In some embodiments, at least 92.5 wt% silver is present, 2-4 wt% Cu may be present, preferably 2-4 wt% Zn is present, 0.02-2 wt% Si is present and 0.04-3.0 wt% Ge is present. The alloy may also contain up to 3.5% by weight of at least one additive selected from In, B and mixtures of In and B, for example up to about 2% by weight B and up to about 1.5% by weight In, and they may also contain 0.25-6% by weight %Sn. A specific class of alloys comprises 81-95.409 wt% Ag, 0.5-6 wt% Cu, 0.05-5 wt% Zn, 0.02-2 wt% Si, 0.01-2 wt% B, 0.01-1.5 wt% In and 0.01- 3% Ge by weight. Another class of alloys contains 75-99.159 wt% Ag, 0.5-6 wt% Cu, 0.05-5 wt% Zn, 0.02-2 wt% Si, 0.01-2 wt% B, 0.01-1.5 wt% In, 0.25-6 wt% Sn and 0.01-3 wt% Ge.

High copper alloys according to WO9622400 (Eccles) can also be used, these alloys are based on 2.5-19.5 wt% Cu, 0.02-2 wt% Si, 0.01-3.3 wt% Ge, the balance silver, incidental components and impurities. Examples of these alloys include (a) 92.5 wt % Ag, 7.0 wt % Cu, 0.2 wt % Si and 0.3 wt % Ge, (b) 92.5 wt % Ag, 6.8 wt % Cu, 0.3 wt % Si and 0.2 wt % Ge and 0.2 wt% Sn, (c) 83.0 wt% Ag, 16.5 wt% Cu, 0.2 wt% Si and 0.3 wt% Ge. In the case of these alloys, it is believed that the combination of germanium and copper content results in the ability to harden by heating to annealing temperature, gradual air cooling, and reheating under mild conditions to produce precipitation hardening.

shaped or processed article

In one embodiment, the article is a shaped or fabricated article, such as a jewelry article, a braided wire mesh or chain or net woven from drawn wire, or spun (spun) from a sheet or tube of the above alloys Concave articles and are processed by heating to brazing or annealing temperatures as they pass through a continuous mesh belt conveying brazing or annealing furnace. Such conveyors are available from, for example, Lindberg of Watertown, WI, USA and the aforementioned Dynalab of Rochester NY. Typically these articles are welded or brazed assemblies of two or more components.

During annealing, although the furnace atmosphere is protective, it is desirable that it should not consume the surface layer of germanium, as this would reduce the tarnish and fire-spot resistance of the alloy. The atmosphere can be nitrogen, cracked ammonia (nitrogen and hydrogen) or hydrogen. The annealing temperature should preferably be 620-650°C. It is not desirable to exceed the maximum temperature of 680°C. The annealing time in this temperature range is 30-45 minutes.

When brazing, it should be noted that the addition of germanium lowers the melting temperature of the alloy by 59°F (15°C) relative to Sterling silver. It is recommended that "easy" or "very easy" grades of solder should be used. The brazing temperature is preferably not more than 680°C, and preferably 600-660°C. A low melting point solder (BAg-7) that can be used contains 56% silver, 22% copper, 17% zinc and 5% tin. BAg-7 solder (international standard) melts at 1205°F (652°C). Brazing filler metals containing germanium will provide better tarnish protection, as described in patent application UK0326927.1 filed 19 November 2003, which is hereby incorporated by reference. A suitable brazing filler metal melting at 600-650° C. contains about 58 wt. % Ag, 2 wt. % Ge, 2.5 wt. % Sn, 14.5 wt. % Zn, 0.1 wt. % Si, 0.14 wt. A practical variant of the material has 58.15 wt% Ag, 1.51 wt% Ge, 2.4 wt% Sn, 15.1 wt% Zn, 0.07 wt% Si, 0.14 wt% B and the balance Cu.

Of course, the articles brazed through the brazing furnace have been simultaneously annealed. It has been found that precipitation hardening can be achieved without a quenching step by controlled gradual air cooling of the cooling zone downstream of the furnace. For this purpose, it is desirable that the material should be held at a temperature of 200-300°C, which is most favorable for precipitation hardening, for at least about 10-15 minutes. Articles brazed in this manner in a furnace, gradually cooled, and then reheated at 300° C. for 45 minutes had a Vickers hardness of 110-115.

Note that the processing necessary for Argentium sterling silver and other germanium-containing silver alloys involves a reduced number of processing steps compared to that required for sterling silver, and avoids quenching and only mild reheating to precipitate Harden to the required level.

Investment Casting Products

Melt Argentium casting particles (solidus temperature 766°C, liquidus temperature 877°C) using conventional methods, and in a protective atmosphere or together with a protective boric acid additive at a temperature of 950-980°C at a temperature not exceeding 676°C Casting is performed at mold box temperature. The mold box temperature during investment casting can be, for example, 500-700°C, and it has been found that dense castings are relatively sensitive to the mold box temperature. Casting materials with relatively low thermal conductivity provide slow cooling of the casting.

Investment casting with air cooling for 15-20 minutes followed by quenching the mold box in water for 15-20 minutes produced a casting with a Vickers hardness of about 70, which is nearly the same hardness as Sterling silver. Surprisingly, it was found that by cooling the mold in air to ambient temperature a higher hardness casting could be produced, the casting having a Vickers hardness of about 110 when removed from the mold. Most standard investment mold release agents can successfully remove investment powder, as can the vibration of an air hammer to break the investment pattern. A water jet can also be used to remove investment patterns. Combining this hardness with fire-staining and tarnishing resistance properties has not been reported for casting production.

Even more surprisingly, and contrary to the experience with sterling silver, the hardness can be increased further by precipitation hardening if required, for example by placing the casting or the whole tree in a furnace set at about 300°C for About 45 minutes to provide a heat treated casting with a Vickers hardness close to 125.

In practice, as explained on page 41 by Fischer-Buhner (above), for conventional sterling silver, simple and slow cooling of the mold after casting results in the growth of coarse Cu-rich precipitates and eliminates the subsequent Possibility of precipitation hardening during aging. Water quenching is required within a narrow and critical time frame after casting, typically within 4 minutes after casting, either too early or too late quenching will reduce the hardening effect. In the case of casting workpieces on a tree mold, different cooling conditions at different locations on the tree mold before quenching will lead to differences in the hardenability of the individual castings in the subsequent precipitation hardening step. All of these problems of extra processing steps and control difficulties can be avoided by using the Ag-Cu-Ge alloys described herein.

The present invention is now further illustrated in conjunction with the following examples.

Examples 1-8

The alloys shown in the table below were prepared by melting the listed components together and subjected to the tests shown below. Compositions showing boron content were believed to contain about 4 ppm boron, but were not examined individually. It is worth noting that a very significant increase in hardness is observed for alloys containing germanium, with the exception of alloys containing no copper, in which case no hardening is observed. Surprisingly, effective hardening of the initially very soft Example 4 alloy was observed.

Example number Ag% Zn% Ge% B Cu% Cooling method 1*HV Cooling method 2*HV Annealed hardness*HV 1 95.44 0 1.5 4ppm Surplus 108 115 67 2** 96 0 1.55 yes Surplus 107 110 64 3** 96 0 2 yes Surplus 110 106 63 4** 97.30 0 1 yes Surplus 93 99 40 5** 98.66 0 1.2 yes 0 28 No precipitation hardening 28 No precipitation hardening 28 6** 95 1 1.5 yes Surplus 109 114 74 7** 93.2 0.7 1.3 yes Surplus 113 117 56 8** 92.7 2 1.3 yes Surplus 113 117 72

*Cooling Method 1 - Samples were annealed in red heat (approximately 600°C), air cooled, then heated at 300°C for 45 minutes.

Cooling Method 2 - Samples were annealed in red heat (approximately 600°C), quenched in water, then heated at 300°C for 45 minutes.

Annealed Hardness - Samples were annealed (approximately 600°C), air cooled, without additional heat treatment.

** Final inspection results not available. The table shows the composition of the alloy before melting.

Example 9-10

The alloys of Examples 9 and 10 were prepared by melting using the following compositions: Example 9 Example 10 Ag 92.5 92.5 Cu 2.35 3.0 Zn 2.82 3.14 Si 0.19 0.15 B 0.01 0.01 In 0.23 0.2 Ge 1.9 1.0

Both alloys were cast and tested for Vickers hardness as cast and annealed in red heat (approximately 600°C), air cooled and then heated at 300°C for 45 minutes. After the above annealing and post-treatment without quenching, the hardness increases to above 100 Vickers hardness.

Examples 11-12

The alloys of Examples 11 and 12 were prepared by melting using the following compositions: Example 11 Example 12 Ag 92.5 92.5 Cu 3.25 4.78 Zn 3.75 2.25 Si 0.2 0.2 B 0.01 0.01 In 0.25 0.075 Ge 0.04 0.125 sn - 0.075

The above alloys were cast and tested for Vickers hardness in the as-cast state, annealed in a red hot state (about 600°C), air cooled, and then heated at 300°C for 45 minutes. The hardness increases significantly after the above-mentioned annealing and post-treatment without quenching.

Claims (27)

1. method for preparing silver alloys finished product or crude product, described method comprises step:

The silver alloys that comprises at least 77 weight % silver, copper and at least 0.5 weight % germanium is provided, and this germanium amount can effectively reduce tarnishing and/or fiery spot;

By being heated to the finished product or the crude product of annealing temperature preparation at least or processing alloy;

Progressively refrigerated product is to envrionment temperature; With

Heating product is to cause its precipitation-hardening once more.

2. according to the process of claim 1 wherein that these goods are ternary alloys of silver, copper and germanium.

3. according to the method for claim 2, outside the wherein removal of impurity, subsidiary composition and all crystal grains fining agent, this ternary alloy comprises 80-98% silver, 0.5-3% germanium and 1-19.9% copper based on the weight of alloy.

4. according to the method for claim 2, outside the wherein removal of impurity, subsidiary composition and the grain-refining agent, this ternary alloy comprises 92.5-98% silver, 0.5-3% germanium and 1-7.2% copper based on the weight of alloy, and 1-40ppm is as the boron of grain-refining agent.

5. according to the method for claim 2, outside the wherein removal of impurity, subsidiary composition and the grain-refining agent, this ternary alloy comprises 92.5-96% silver, 1-2% germanium and 1-7% copper based on the weight of alloy, and 1-20ppm is as the boron of grain-refining agent.

6. according to the method for claim 2, wherein this ternary alloy comprises 92.5-92.7 weight % silver, 6.1-6.3 weight % copper, about 1.2 weight % germanium and the 1-15ppm boron as grain-refining agent.

7. according to the method for arbitrary aforementioned claim, wherein in stove, goods are carried out annealing in the air cooled process behind the brazing and following.

8. according to the method for claim 7, wherein by in stove, alloy being annealed or soldering 600-680 ℃ of heating.

9. according to the method for claim 7, wherein by in stove, alloy being annealed or soldering 600-660 ℃ of heating.

10. according to claim 7,8 or 9 method, wherein use the solder that comprises 56%Ag, 22%Cu, 17% zinc and 5% tin that alloy is carried out soldering.

11., wherein use the solder that comprises 58 weight %Ag, 2 weight %Ge, 2.5 weight %Sn, 14.5 weight %Zn, 0.1 weight %Si, 0.14 weight %B and surplus Cu that alloy is carried out soldering according to claim 7,8 or 9 method.

12., wherein under 600-650 ℃ temperature, anneal and/or soldering according to each method among the claim 7-11.

13., wherein goods are carried out investment cast and air cooling according to each method among the claim 1-6.

14. according to the method for claim 13, wherein goods are jewelry or gift.

15., wherein under 180-350 ℃, heat once more according to the method for arbitrary aforementioned claim.

16., wherein under 200-300 ℃, heat once more according to the method for arbitrary aforementioned claim.

17. a method for preparing silver alloys finished product or crude product, described method comprises step:

The Zn that comprises at least 86 weight %Ag, 0.5-7.5 weight %Cu, 0.07-6 weight % and Si mixture and about 0.01 weight % are provided the silver alloys to no more than 3.0 weight %Ge (preferred no more than 2.0 weight %Ge), and the content of wherein said Si is the about 2.0 weight % of about 0.02-.

By being heated to the finished product or the crude product of annealing temperature preparation at least or processing alloy;

Refrigerated product progressively; With

Heating product is to cause its precipitation-hardening once more.

18., wherein have the silver of at least 92.5 weight % according to the method for claim 17.

19., wherein have 2-4 weight %Cu according to the method for claim 17 or 18.

20., wherein have 2-4 weight %Zn according to claim 17,18 or 19 method.

21., wherein have 0.04-3.0 weight %Ge according to each method among the claim 17-20.

22., wherein have at the most at least a In of being selected from, the B of 3.5 weight % and the additive of In and B mixture according to each method among the claim 17-21.

23. according to each method among the claim 17-22, wherein said mixture comprises the In of the B of about at the most 2 weight % and about at the most 1.5 weight %.

24., wherein have the Sn of 0.25-6 weight % according to each method among the claim 17-24.

25. according to the method for claim 17, wherein said alloy comprises 81-95.409 weight %Ag, 0.5-6 weight %Cu, 0.05-5 weight %Zn, 0.02-2 weight %Si, 0.01-2 weight %B, 0.01-1.5 weight %In and 0.01-3 weight %Ge.

25. according to the method for claim 17, wherein said alloy comprises 75-99.159 weight %Ag, 0.5-6 weight %Cu, 0.05-5 weight %Zn, 0.02-2 weight %Si, 0.01-2 weight %B, 0.01-1.5 weight %In, 0.25-6 weight %Sn and 0.01-3 weight %Ge.

26. a method for preparing silver alloys finished product or crude product, described method comprises step:

Provide and comprise any silver alloys of following alloy: (a) 92.5 weight %Ag, 7.0 weight %Cu, 0.2 weight %Si and 0.3 weight %Ge, (b) 92.5 weight %Ag, 6.8 weight %Cu, 0.3 weight %Si and 0.2 weight %Ge and 0.2 weight %Sn, (c) 83.0 weight %Ag, 16.5 weight %Cu, 0.2 weight %Si and 0.3 weight %Ge

By being heated to the finished product or the crude product of annealing temperature preparation at least or processing alloy;

Refrigerated product progressively; With

Heating product is to cause its precipitation-hardening once more.