JP2008513607A - Copper-boron mother alloy and method of use for making silver-copper alloy - Google Patents

Abstract

The base metal material used to make an alloy containing 77 wt% Ag and 0.5 wt% Ge by mixing with silver is mixed with any additional components used in the alloy, together with Cu and Ge and boron. Including all of things. And any additional components used in the alloy, including 77 wt% or more Ag (silver), 1 to 7.2 wt% Cu (copper), 0.5 wt% or more Ge, and B; There is also provided a method of making a silver alloy containing impurities, which includes pure silver and a parent metal material (eg, 92.5-92.8 wt% Ag) that is a ternary alloy of at least copper, germanium, and boron, Melting 6.0 to 6.3 wt%, about 1.2 wt% Ge, and an alloy of 1 to 15 ppm boron as a crystal refiner. The resulting silver alloy exhibits good anti-fogging properties and resistance to firestain, and can be sufficiently precipitation hardened by slow cooling in air. A further feature of the present invention relates to a method for producing a copper-based master alloy used to make a silver alloy product, in which the molten master alloy is decomposed prior to solidification (such as boron hydride or hydride). Treatment with boron metal hydride).
[Selection figure] None

Description

  The present invention relates to a master metal composition suitable for mixing with silver to form an alloy, and also relates to a method for producing a silver alloy using the parent metal material, for producing a molded product and It also relates to the further optional treatment of the alloy in order to obtain a precipitation hardening action.

(Not mentioned in the original)

  The present invention provides a copper based master alloy for mixing with silver to form an alloy, the master alloy comprising germanium and boron, and optionally other alloy components (silver and / or zinc and / or Or silicon and / or indium).

  The present invention also provides a substantially pure copper or copper alloy (Cu-Ge or Cu-Zn-Ge or Cu-Ge-Si or Cu-Ge-Zn-Si alloy containing less than 2 wt% boron. A copper or copper alloy that is introduced into copper using as a means a compound that can be decomposed in situ in molten copper to form boron. These compounds can be selected from the group consisting of alkyl boron compounds, boron hydrides, boron halides, boron-containing metal hydrides, boron-containing metal halides, and mixtures thereof. In situ decomposition is superior to the current method for making copper-boron master alloys (that is, a method in which copper and boron fine particles are rapidly melted and mixed, making it easy to form boron hard spots). It seems that there is. In some embodiments, to obtain a useful master alloy that can provide a large amount of boron component to the alloy mixed with the master alloy and that the hard spot growth is kept to an acceptable level. Is possible. The boron content in these alloys can be increased to a level of 2 wt% of currently available Cu-B alloys, or more than in the case of noble metal alloys obtained when using boron as a crystal refiner. It can also be reduced. In some embodiments, Ag-Cu-Ge-B, Ag-Cu-B, Ag-Cu-B-Si, or Ag containing a sufficient amount of silver to promote copper melting or casting. -Cu-Ge-B-Si, for example, the amount of silver is 1-30 wt% Ag, typically 1-25 wt% Ag, more typically 10-25 wt% Ag can do.

  An embodiment of the present invention relates to a parent metal material used to obtain a silver alloy that is mixed with silver to contain 77 wt% or more of Ag and 0.5 wt% or more of Ge, the parent metal material comprising Cu And Ge and 0.001 to 0.5 wt% (typically 0.005 to 0.3 wt%) boron, in addition to all of the additional optional components and contaminants for the resulting alloy. .

  Furthermore, the present invention includes 77 wt% or more of Ag, 1 to 7.2 wt% of Cu (copper), 0.5 wt% or more of Ge, and 0.005 to 0.3 wt% of B, and further for a silver alloy. There is also provided a method for making a silver alloy that includes all of the additional optional components and all of the contaminants, the method including melting together pure silver and the parent metal material described above.

  In yet another embodiment of the present invention, a method for making a master alloy for use in the manufacture of silver products, comprising melting copper (and any germanium or other alloy components), and an alkyl boron compound Adding boron in the form of a compound selected from the group consisting of boron hydride, boron halides, boron-containing metal hydrides, boron-containing metal halides, and mixtures thereof to the melt. Provide a simple method. The present invention can also be applied to, for example, the manufacture of a master alloy (such as a Cu—Ge—B master alloy or a Cu—B master alloy).

  The use of the master alloy provides a number of technical advantages. Boron is a very light element and is easily lost during the melting process. If the amount of boron in the alloy is too large or the boron is not sufficiently dissolved, a hard spot of boron is generated and the surface of the silver product is abraded when it is polished. Nevertheless, it is common to add more boron than necessary to compensate for the loss during melting. It is currently unknown what happens to the added boron, but one possibility is that boron reacts with the oxygen present in the silver. Another possibility is that the material of the graphite crucible which normally melts the alloy in it reacts with boron. A third possibility is that boron is released beyond the surface of the melt and is oxidized by oxygen present in the atmosphere. However, when germanium and boron are combined in the master alloy, a protective effect is obtained, and germanium is considered to protect boron in the same manner as germanium protects copper.

  In some embodiments, the order in which the ingredients are alloyed can be important. It is difficult to add boron to a copper alloy first after adding germanium. This is because when copper boride is used as a boron source, a high temperature is required to dissolve boron in the alloy, so that the germanium component of the alloy is exposed to the risk of being overheated. It is a problem. Therefore, in the mother alloy according to the present invention, usually, the element having the highest melting point is first melted and mixed first, and then the processing is performed while adding the element having the lower melting point. Another method is to add boron as boron hydride or boron hydride metal, which decomposes when it touches the molten metal of the master alloy, and disperse boron in the alloy, thereby giving the opportunity to grow hard spots etc. I can take it away.

Furthermore, the present invention also provides a method for casting a master alloy containing at least Cu and B.
(A) forming a precursor master melt containing at least Cu;
(B) A compound selected from the group consisting of alkyl boron compounds, boron hydrides, boron halides, boron-containing metal hydrides, boron-containing metal halides, and mixtures thereof, is dispersed throughout the mother melt. And steps to
(C) solidifying the molten metal.

[Mother alloy]
The master alloy can include 80-95 wt% Cu (or Cu along with further optional components for the alloys described below) and 20-5 wt% Ge. A preferred class of alloys includes 80-86.7 wt% Cu (or Cu along with further optional components for the alloys described below) and 20-13.3 wt% Ge. A still more preferred class of alloys comprises 82-84.55 wt% Cu and further optional components for the alloy and 15.5-18 wt% Ge. An alloy having about 0.03 wt% B can be used to provide the desired boron component to the silver alloy into which the alloy is incorporated. A preferred class of master alloys includes only copper, germanium, boron, and impurities.

  The master alloy can supply all of the copper required for the silver alloy. As another method, a silver alloy can also be made by mixing and melting copper and a master alloy of the type defined above.

[Borne mixing in copper or copper master alloy]
The mother alloy precursor to which boron is added can be pure copper or Cu-Ge, or a small amount of casting aid (casting) that facilitates casting and suppresses surface cracks and roughness. adjuvants) (Si or Ag etc.) and Cu or Cu-Ge. The copper or alloy is usually placed at a nominal temperature for casting or casting (eg about 1150-1200 ° C.). The melting temperature affects the kinetics of boron evaporation and determines the final boron concentration in the cast mother alloy. The temperature to be selected is higher than the liquidus temperature of the alloy in order to suppress solidification in the die during continuous casting or in the grain box during crystal formation. The temperature should be high enough. Alloys can be easily cast at atmospheric pressure, but pressures higher or lower than atmospheric pressure do not affect the advantages of the present invention. However, it can affect the kinetics of boron evaporation. Furthermore, for master alloys that are mixed and melted with precious metals to form casting grains and then further melted to form rods or wires, or investment casting, there are many Desirably, a boron component is included.

  In some embodiments, sufficient boron is added to the master alloy so that an effective amount of boron remains in the noble metal alloy or master alloy to be cast, thereby providing effective crystal refinement and deoxidation effects. be able to. Typically, the boron content of the master alloy is in the range of 100 ppm to 1600 ppm, and the nominal boron content in the casting master alloy is more typically about 250 ppm. Typically, it is effective to add 0.01% to 0.16% boron to the precursor alloy melt.

Boron is mixed in the mother alloy according to the present invention and used as an oxygen scavenger and / or crystal refiner in the final silver alloy. Boron can be added as a metal boride (such as copper boride). Also, a molten mother alloy (Cu, Cu-Ge, Ag-Cu-Ge, Ag-Cu-Si, or Ag-Cu containing boron, for example, 50 wt% or more of Cu (and optionally ancillary components). As another method of adding to -Ge-Si, etc., gas borane (such as diborane) combined with non-reactive gas (such as argon) can be added by passing it through the master alloy. Alternatively, boron can be added by introducing borane (decaborane B ₁₀ H ₁₄ , mp 100 ° C., bp 213 ° C., etc.) that is solid at ambient temperature into the master alloy, or alkylated borane (triethylborane or Boron can also be added by adding tri-n-butylborane, etc. (however, the latter reagent ignites spontaneously and its handling is necessary). However, boron is preferably added as a boron hydride metal, such as an alkali metal borohydride, a pseudo-alkali metal hydride, an alkaline earth metal borohydride, etc. (boron hydride). Boron is preferably added as lithium). Particularly preferred is sodium borohydride, which is widely available on the market and is available in the form of relatively large pills (pellets) and is therefore easy to handle during the noble metal melting process.

  As described above, the gaseous boron compound is introduced into the molten copper or copper alloy. Preferably, however, the gaseous boron compound is mixed with a carrier gas to melt the molten boron or copper alloy. A flow of stirring is created to assist in dispersing the boron component of the gas mixture in the alloy. Suitable carrier gases include, for example, hydrogen, nitrogen, and argon. Gaseous boron compounds and carrier gases can be introduced from above a container containing molten copper or copper alloy. For example, a metallurgical lance (elongated tube made of a heat-resistant material such as graphite, or a metal tube covered with a heat-resistant material for a crucible in a copper melting furnace, a casting bottle, or a storage weir Etc.) is used so that its lower end is immersed in the molten copper or alloy, a gaseous boron compound and a carrier gas can be introduced. This lance is preferably provided with a length sufficient to inject a gaseous boron compound and a carrier gas into the deep portion of the molten copper or copper alloy. Alternatively, the boron-containing gas can be introduced from the side or bottom of the molten copper or copper alloy using, for example, a gas permeable bubbling valve or a submerged injection nozzle. For example, Rautomead International of Dundee, Scotland manufactures horizontal continuous casters (RMK series) for continuous casting of semi-finished products. Copper or alloy to be heated is put in a crucible made of solid graphite and protected with an inert gas atmosphere (such as nitrogen containing less than 5ppm oxygen and less than 2ppm water, oxygen-free nitrogen), and using a graphite block It can be heated by a resistance heating method. Such furnaces have built-in equipment for passing an inert gas through the melt.

By adding a small amount of thermally decomposable boron-containing gas to the inert gas passed through the molten metal, the desired amount of boron in the molten metal or alloy is reduced from several ppm to several hundred ppm, and even several thousand ppm. It can be easily introduced in the range. By introducing the boron compound into the copper or copper alloy as a dilute gas stream over a period of time, the carrier gas in the gas stream agitates the molten copper or alloy, so that the boron compound is a relatively large one. Or it is preferable from the viewpoint of suppressing the generation of boron hard spots in the metal or alloy as compared with the case where it is introduced as a plurality of lumps. Can be used as a master alloy for. Compounds that can be introduced in this way into molten copper or its alloys include boron trifluoride, diborane, or trimethyl boron, which are added to hydrogen, argon, nitrogen, or helium in a high pressure gas container. It is available in the put state. Among these, unlike other boron compounds, diborane can be said to be preferable because the only other element that enters the alloy is hydrogen. Yet another measure is to pass the carrier gas through the molten copper or its alloy, so that the stir action of the carrier gas is reduced while the solid boron compound (NaBH ₄ or NaBF ₄ or the like) is made into a fine powder that constitutes the aerosol. It is also possible to add to the flowing gas stream.

  Moreover, the boron compound which is a liquid can also be introduce | transduced in the molten copper or copper alloy, In that case, you may introduce | transduce as it is or you may melt | dissolve in an inert organic solvent and introduce | transduce. Compounds that can be introduced in this manner include alkylboranes or alkoxy-alkylboranes, such as triethylborane, tripropylborane, tri-n-butylborane, and methoxydiethylborane. In order to handle these safely, it is better to dissolve in hexane or THF. Liquid boron compounds can be used in containers made of copper foil in the form of capsules or sachets, as well as devices for filling known liquids / capsules or liquids / capsules, filled capsules or capsules or other It can be filled and sealed using a protective atmosphere to create a small container (usually 0.5-5 ml in volume, more preferably about 1-1.5 ml). Alternatively, the capsule or sachet can be made of a polymer such as polyethylene or polypropylene. The appropriate number of capsules or wraps so filled may be placed individually in molten copper or alloys thereof, or may be placed in one or more groups. As yet another alternative, a liquid boron-containing compound can be sprayed into a carrier gas stream used to stir the molten copper or copper alloy as described above. The boron-containing compound droplets can be in the form of an aerosol in a carrier gas or volatilize in the carrier gas.

As described above, the boron compound is preferably introduced into the molten copper or copper alloy as a solid. For example, solid borane such as decaborane B ₁₀ H ₁₄ (mp 100 ° C, bp 213 ° C) should be used. Can do. However, it is preferred to use any form of boron-containing metal hydride or boron-containing metal fluoride or other halide when adding boron. When boron-containing metal hydrides are used, suitable metals include sodium, lithium, potassium, calcium, zinc, and mixtures thereof. Sodium is the preferred metal when boron-containing metal fluorides are used. Most preferred is sodium borohydride NaBH ₄ (molecular weight 37.85), which contains boron in a proportion of 28.75% and is available in the form of relatively large pellets that are easy to handle during the precious metal melting process. .

  Boron is likely to be volatilized and lost from high-temperature molten copper or copper alloys, so it may be necessary to add boron later to maintain a sufficient concentration for crystal refinement. is there. A thin copper foil or thin inert material (that is, a material that decomposes in molten silver with virtually no residue left) to make it easier for boron compounds to mix in copper or copper alloys. Alternatively, the boron compound can be wrapped with a foil of a resin sheet or the like. The preferred metal for forming the foil is copper, but silver may also be used as the foil because it has the effect of supplementing the casting properties. The thickness of the foil is preferably in the range of about 0.01 mm to about 0.3 mm, and the boron compound wrapped in the foil is sufficiently submerged in the molten copper or alloy before the foil melts, so that the boron Allow the compound to be released. When released, the boron compound combines with the oxygen in the melt and effectively deoxidizes the melt. Boron reacts with some of the elements in the melt to form scattered insoluble particles and is dispersed throughout the substrate (although the effect of the present invention is not dependent on the correctness of this theory). This insoluble particle is considered to function as a crystal nucleation part, promoting the formation of fine crystals that are uniform in size and difficult to grow.

For example, when diborane is used to add boron to the molten metal, the compound is decomposed into boron and hydrogen (for example) as follows.

B ₂ H ₆ → 2B (s) + 3H ₂ (g)

This hydrogen effectively deoxidizes the molten metal.

When sodium borohydride is first added to the molten metal, the first reaction is considered to be decomposition of the boron-containing crystal refiner.

(1) NaBH ₄ (s) → Na (g) + B (s) + 2H ₂ (g)

All of the sodium, hydrogen and boron produced after decomposition is useful for deoxidizing the melt as follows.

(2) Na (g) + 0.5O ₂ (g) → Na ₂ O (s)
(3) H ₂ (g) + 0.5O ₂ (g) → H ₂ O (g)
(4) B (s) + 0.5O ₂ (g) + 0.5H ₂ (g) → HBO (g)

In order to perform uniform casting, it is preferable to stir for more than 1 minute (usually 1 to 5 minutes) to disperse boron throughout the molten metal. Stirring can be performed using any means that does not contaminate the molten metal (such as a graphite stirring rod).

  The resulting master alloy is cast using a method suitable for forming the desired product. One such useful product is a casting crystal. A casting crystal is a small grain sold to a jewelry manufacturer, and a desired jewelry is formed by investment casting in which a master alloy crystal and a precious metal crystal are combined. is there. After stirring, the molten master alloy is poured into a crystal box, which is a container having an opening at the bottom, and a liquid metal is poured through the crystal box to produce a desired shape and crystal size. The crystal box can be made of the same material as the crucible. For example, graphite, clay / graphite, ceramic, silicon carbide, and the like can be used, but the invention is not limited thereto. By melting the molten master alloy into small droplets scattered in the crystal box and flowing from the opening, by dropping the master alloy droplet into the water of the crystal tank (water) containing water and solidifying it, Solidify as roughly spherical particles. Thereafter, the casting crystal of the mother alloy is taken out of the crystal tank and dried (by centrifugal force and hot air). The diameter of the roughly spherical crystals obtained is usually in the range of about 0.1 mm to about 5 mm.

[Alloy that can be produced from the master alloy according to the present invention]
The mother alloy according to the present invention can be used for producing a silver alloy.

  The master alloy according to the present invention has an Ag component of 75 wt% or more, a Ge component of 0.5 to 3 wt%, and copper as a residue excluding all incidental components and impurities, and crystal refinement It can be used to make silver / germanium alloys containing boron as an agent. If desired, part of this copper component can be replaced with Al, Ba, Be, Cd, Co, Cr, Er, Ga, In, Mg, Mn, Ni, Pb, Pd, Pt, Si, Sn, Ti, V Replace with one or more incidental elements selected from Y, Yb, Zn, and Zr that do not unduly affect germanium's effect on firestain and haze resistance You can also. The weight ratio of the incidental component to germanium can be in the range of 100: 0 to 80:20, preferably in the range of 100: 0 to 60:40. The term "incidental ingredients" can be used to refer to ingredients that have an auxiliary functionality within the alloy (such as a tint or improved appearance when cast) The term can include a certain amount of metal or metalloid, for example, Si, Zn, Sn, or In suitable for “deox”.

  Alloys that can be made in accordance with the present invention include coin casting grade, grade 800 (including grade 830 and grade 850, etc.), and standard sterling silver, and amounts effective to reduce fire and / or haze A silver alloy containing germanium. The Ag-Cu-Ge ternary alloy, Ag-Cu-Zn-Ge quaternary alloy, and Ag-Cu-Ge-Si quaternary alloy that can be appropriately produced by the method according to the present invention are based on the weight of the alloy. 80% or more, preferably 92.5% or more, and has a silver component with 98% as the upper limit (preferably 97% as the upper limit). The germanium content of the Ag-Cu- (Zn) -Ge alloy or Ag-Cu- (Si) -Ge alloy should be 0.1 wt% or more, preferably 0.5 wt% or more, more preferably 1.1 wt% That's it. It is preferable that the germanium component does not exceed 1.5% with respect to the weight of the alloy, more preferably 4 wt% or less, and the upper limit is preferably 6.5 wt%.

  In particular, silicon can be added to the silver alloy at, for example, 0.5 wt% or less, typically 0.5-3 wt%, more universally 0.1-0.2 wt%, preferably about 10 wt%, for example. Available in the form of a copper-silicon master alloy containing 1% Si. For example, by incorporating silicon into a casting crystal of a silver-copper-germanium ternary alloy, an investment casting with a lustrous appearance can be readily removed from the mold. For example, silicon can be added to the casting crystals prior to investment casting, or an alloy can be made by mixing silicon into silver during the initial melting.

  The remainder of the Ag-Cu-Ge ternary alloy, excluding impurities, ancillary components, and all grain refiners, will consist of copper, 0.5% of the final alloy weight. % Should be present, preferably 1% or more, more preferably 2% or more, and most preferably 4% or more. For a ternary silver alloy of “Grade 800”, a suitable copper content is, for example, 18.5%. When an appropriate amount of copper is mixed into the master alloy, copper usually accounts for more than 50 wt% of the master alloy.

  The remainder of the Ag-Cu-Zn-Ge quaternary alloy, excluding impurities and all crystal refiners, should be copper (0.5% or more based on the weight of the alloy, preferably 1% or more, more preferably 2% or more, most preferably 4% or more) and zinc (should be present so that the weight ratio to copper does not exceed 1: 1). Therefore, zinc is optionally present in the silver-copper alloy, the amount of which is 0-100% of the weight of the copper component. For a “grade 800” quaternary silver alloy, for example, it is appropriate that the copper content is 10.5% and the zinc content is 8%. If zinc is present, it can be mixed into the master alloy.

  In addition to silver, copper, germanium, and optional zinc, the silver alloy preferably further includes a crystal refining agent that suppresses crystal growth during the processing of the alloy. Add as part of the master alloy. Suitable crystal refiners include boron, iridium, iron, and nickel, with boron being particularly preferred. The grain refiner (preferably boron) is present in the Ag-Cu- (Zn) -Ge alloy or Ag-Cu- (Si) -Ge alloy in the range of 1 ppm to 100 ppm relative to the weight of the alloy. Preferably, the range is 2 ppm to 50 ppm, more preferably 4 ppm to 20 ppm.

  In a preferred embodiment, the silver alloy is 80% to 96% silver, 0.1% to 5% germanium and 1% to 19.9%, based on the weight of the silver alloy, excluding impurities and all grain refiners. A ternary alloy consisting of copper. In a more preferred embodiment, the silver alloy, excluding impurities and crystal refiners, is 92.5% to 98% silver, 0.3% to 3% germanium and 1% to 7.2% copper, based on the weight of the alloy. And a ternary alloy consisting of 1 ppm to 40 ppm boron as a crystal refiner. In a more preferred embodiment, the silver alloy, excluding impurities and crystal refiner, is 92.5% to 96% silver, 0.5% to 2% germanium and 1% to 7% copper, based on the weight of the alloy. And a ternary alloy consisting of 1 ppm to 40 ppm boron as a crystal refiner. A particularly preferred silver ternary alloy is commercially available as Argentium ™ and contains 92.7-93.2 wt% Ag, 6.1-6.3 wt% Cu, and about 1.2 wt% Ge.

  Specific examples of alloys (Cu-B or Cu-Ge-B) that can benefit from the addition of boron using the master alloy according to the present invention include the following.

(I) US-A-3811876 (Harigawa et al., K. K. Suwa Seikosha, the description of which is included in this disclosure by this reference). Disclosed is a silver alloy that reduces fogging by the synergistic action of Sn, In, and Zn. Here, an alloy consisting essentially of 4-10 wt% Sn, 0.5-12 wt% In, 0.1-5 wt% Zn, and the balance silver is described and claimed. Here too, Ti, Zr, Be, Cr, Si, Al, Ge, and / or Sb are added to protect the surface of the silver alloy by preferentially oxidizing to form a stable oxide. It is also claimed that mechanical strength and anti-fogging are increased. When the amount of these additive elements is less than 0.001 wt%, it is not effective. It is also stated that adding Ti, Zr, Be, Cr, or Si in an amount exceeding 1 wt% will make the alloy brittle, and that insoluble components will be formed, affecting polishing. Yes. It is stated that the addition of 0.001 to 5 wt% Al, Ge, and Sb can increase the anti-fogging property without reducing the workability. Although it is stated that the alloy does not contain copper and is not subject to fire burns, it is soft.

(Ii) US-A-4973446 (Bernhard et al., United Precious Metal Refining, the disclosure of which is hereby incorporated by reference). A silver alloy material of Sn, In, Zn type and further containing copper and boron is disclosed. This silver alloy is composed of 89-93.5 wt% Ag, 0.01-2 wt% Si, about 0.001-2 wt% B, about 0.5-5 wt% Zn, about 0.5-6 wt% Cu, about 0.25 to 2 wt% Sn and about 0.01 to 1.25 wt% In. Silicon is added as a de-oxidant. Boron is added to reduce the surface tension of the molten alloy so that it can be mixed uniformly. Zinc is added to lower the melting point of the alloy, to add whiteness, to replace copper, as a deoxidizer, and to improve the fluidity of the alloy. Copper is added to function as a conventionally known silver curing agent and also as a main carrier for other substances. Tin is added to improve anti-fogging property and to obtain the hardening action of tin. Indium is added as a crystal refiner and to improve the wetability of the alloy. Silver must be present in the minimum percentage necessary to be recognized as coin-casting silver or sterling silver. Also disclosed is a master alloy used to make the silver alloy material described above, 0.91 to 30.77 wt% Si, 0.001 to 30.77 wt% B, 4.54 to 76.93 wt% Zn, 4.54 to It is said that it can contain 92.31 wt% Cu, 2.27-30.77 wt% Sn, and 0.09-19.24 wt% In. Typical master alloys include about 25 wt% Zn, about 54 wt% Sn, about 0.75 wt% In, about 19.44 wt% Cu, about 0.135 wt% B, and about 0.675 wt%. Si and included. According to the experience of the inventors of the present invention, this alloy not only shows a certain degree of anti-fogging, but also reduces the burns during investment casting to some extent, while the copper component Insufficient resistance to burning during soldering or annealing. The same applies to the description of US-A-5039479 (Bernhard et al., Incorporated herein by reference).

(Iii) GB-B-2255348 (Rateau, Albert and Johns; Metaleurop Recherche, the disclosure of which is hereby incorporated by this reference). Disclosed is a silver alloy that reduces the problems caused by the oxidization of copper components while inheriting the hardening and gloss properties unique to Ag-Cu alloys. This alloy is an Ag—Cu—Ge ternary alloy containing 92.5 wt% or more of Ag, 0.5 to 3 wt% of Ge, and copper as a remainder excluding impurities. This alloy does not rust in the open air during the conventional production process, deformation process, and finishing process, is easy to cold deform, is easy to braze, and has a large shrinkage. Do not wake up. Furthermore, this alloy also exhibits excellent ductility and tensile strength. Germanium exhibits a protective function, which can be usefully combined with the properties exhibited by the novel alloys. Further, germanium was dissolved in both the silver phase and the copper phase. The microstructure of this alloy is composed of two phases, and a solid solution of germanium and copper in silver is surrounded by a filamentous solid solution of germanium, silver and copper. The germanium in the copper-rich phase forms a thin protective film of GeO and / or GeO ₂ to suppress the oxidation of the surface of this phase and suppress the occurrence of burning during brazing and flame annealing. In addition, the addition of germanium can greatly delay the haze expansion, the surface blackish turns slightly yellow, and the resulting haze can be easily removed using normal tap water. . This alloy is particularly useful as a jewelry.

(Iv) US-A-6168071 (Johns, the disclosure of which is hereby incorporated by this reference). In particular, a silver / germanium alloy having an Ag component of 77 wt% or more with respect to the alloy weight, a Ge component of 0.5 to 3 wt% with respect to the alloy weight, and copper as a remainder excluding all impurities, Alloys are described and claimed which contain boron as a grain refiner in concentrations up to about 20 ppm. If desired, alloys can be used in place of the disclosed CuB master alloy by using alkyl boron compounds, boron hydrides, boron halides, boron-containing metal hydrides, boron-containing metal halides, and mixtures thereof. A boron component can also be provided.

(V) US-A-6406664 (Diamond, the disclosure of which is hereby incorporated by reference). It is said to be resistant to fire and cloudiness and is 92.5-96 wt% Ag, 0.1-0.38 wt% Ge, 0.5-3.8 wt% Sn, 0.001-0.008 wt% B, 0.001 Disclosed is a silver alloy comprising -0.1 wt% Ni, copper as the balance, boron used as a crystal refiner, and tin and nickel components said to reduce the amount of germanium . This alloy is said to be age hardened, soldered, welded, molded, cast, and mechanically processed. It is said that the product does not shrink, does not become rough, and does not cause a fire scale in a process involving an increase in temperature.

(Vi) US 6726877 (Eccles, the disclosure of which is hereby incorporated by this reference). Disclosed is a silver alloy material for jewelry with work-hardening properties that is alleged to be resistant to scorching. This alloy has more than 86wt% Ag, 0.5-7.5wt% Cu, 0.07-6wt% Zn and Si mixture (where Si is 0.02-2wt%), 0.01-2.0wt% Including Ge. The alloy can also include flow modifiers and other additives added to improve the castability and / or wettability of the molten alloy. For example, a refinement additive selected from In, B, or mixtures thereof may be added to the alloy up to about 3.5% based on the weight of the alloy to refine the crystal and / or wet the alloy. Can be increased. This material can be made by adding pure silver to the master alloy, where, for example, the master alloy contains 52.5-99.85 wt% Cu, 0.1-35 wt% Zn, and 0.05-12.5 wt% Ge.

(Vii) US 6841012 (Croce; Steridyne Laboratories, the disclosure of which is hereby incorporated by reference). About 85% or more of silver by weight of silver and zinc, copper, indium, tin, and iron, and optionally further at least of gold, silicon, manganese, boron, bismuth, cobalt, chromium, and lead Disclosed is a silver alloy having high antifogging properties, including the remainder of the alloy including one. It is stated that the presence of zinc can add whiteness to the alloy. Copper is said to function as a hardener according to the prior art and to add malleability. Indium is said to give the alloy shine and ductility, further facilitating the casting of the alloy. Tin is stated to be added for the hardness, malleability, ductility and ease of soldering of the alloy. Iron is said to be added for the hardness of the alloy. Boron is said to contribute to the removal of burnt haze.

(Viii) US 6913657 (Ogasa, the description of which is hereby incorporated by reference). Various noble metal alloys are disclosed. In certain embodiments, this document discloses a composition of a hard noble metal alloy mainly composed of a silver alloy, the silver alloy comprising 80.0 wt% or more of a silver component and an amount of gadolinium of 50 ppm or more and less than 15000 ppm. including. An amount of 0.01-0.1 wt% boron is added to some of the alloys.

(Ix) US-A-2004 / 0219055 (Croce, the description of which is included in this disclosure by this reference). A Zn, Cu, In, Sn group anti-fogging silver alloy is disclosed, this alloy has an Ag of 85 wt% or more and also contains Fe as a balance. Boron is an optional additive component.

[Post-processing of products made using the master alloy]
Ag-Cu-Ge silver alloy workpieces and molded products made with the master alloy described above and heated to annealing temperatures can be self-cured using controlled air cooling, annealed and / or precipitated. It is possible to obtain a product with useful hardness without requiring reheating to obtain a curing effect. Moreover, in the present invention, it is possible to further cure by reheating to, for example, 180 to 350 ° C. (preferably 250 to 300 ° C.). Even if the overaging of the Ag-Cu-Ge silver alloy occurs during precipitation hardening, the obtained hardness does not drop significantly. The processing of the workpiece can be performed, for example, in a mesh belt conveyor furnace or as part of soldering or annealing during investment casting, thus reducing the number of steps required to produce the required hardness product, In particular, it is not necessary to perform the quenching work using water, which is necessary for Ag-Cu sterling silver.

  There are surprising differences in properties between prior art sterling silver alloys and sometimes other Ag-Cu binary alloys and sometimes Ag-Cu-Ge alloys. The difference is that when the binary Stirling type alloy is slowly cooled, coarse precipitation occurs and only limited precipitation hardening is obtained, while the Ag-Cu-Ge alloy is gradually reduced. When cooled (especially when containing an effective amount of a crystal refiner), fine precipitation occurs and useful precipitation hardening is obtained. Furthermore, the addition of germanium to sterling silver changes the thermal conductivity of the silver alloy, making it different from standard sterling silver. The International Annealed Copper Scale (IAS) is a standard for metal conductivity. According to this standard, if the value of copper is 100%, pure silver is 106% and standard sterling silver is 96%, but a sterling alloy containing 1.1% germanium has a conductivity of 56%. This fact is important because the heat dissipation rate of Argentium sterling and other germanium-containing silver alloys is slower than that of standard sterling silver or its similar germanium-free material, so that the workpiece cools down. Since it takes time, it is deposited to a commercially useful level (preferably 110 Vickers hardness or higher, more preferably 115 Vickers hardness or higher) while it is allowed to cool in the atmosphere as it is or slowly cooled with controlled air cooling. It depends on being curable.

  For alloys formed after the master alloy defined above is mixed with a silver alloy obtained from a bullion manufacturer, for example 999 pure silver or 9999 pure silver, the molded product of the alloy is annealed in a furnace and / or It is possible to apply a further step of brazing and a subsequent curing step by air cooling. Thus, the alloy can be annealed and / or brazed by heating in a furnace at 600-680 ° C (preferably 600-660 ° C, more preferably 600-650 ° C). Annealing can take place during investment casting and can be cured by air cooling the air or allowing it to cool in air. The finished product can be a jewelery or gift.

  Since the silver alloy according to the present invention can be precipitation hardened, the copper component in the alloy can be reduced. In the case of an alloy having a copper component even in a small amount, it becomes relatively soft at the time of casting, so reheating it to a lower temperature such as 200 to 300 ° C. can give a hardness equivalent to or higher than that of ordinary sterling silver. Trying to get. Actually, from the viewpoint of corrosion resistance, it can be said that the copper component is the most harmful among the alloys, but in standard Stirling alloys, if the copper component is reduced, the hardness falls to an unacceptable level. This property of the alloy according to the invention is therefore a great advantage. When reducing the copper component, simply increasing the silver component is the preferred choice. Other options include increasing the germanium component or adding zinc or other alloying elements. A silver alloy having Ag at 973/1000 and containing about 1.0 wt% Ge and the remainder copper has been shown to precipitate and harden well by slow air cooling from the annealing temperature. Ag-Cu-Ge alloys containing a certain amount of silver component are also considered to be precipitation hardenable. Copper in the mother alloy can be adjusted by the silver component.

  The advantage of not requiring quenching to obtain a hardening action is of great utility for silver alloys made from the master alloy according to the present invention. In actual manufacturing, it is unlikely that a silver piece craftsman can safely quench a metal piece that has been processed close to the finish. This quenching process may not be commercially appropriate due to the risk of distortion and damage to the soldered weld when quenched from high temperatures. In fact, standard Stirling can only be precipitation hardened after quenching. This is one reason why precipitation hardening cannot be used for sterling silver.

  The techniques for practicing the present invention will be described in further detail in the following examples, for the purpose of illustration only.

Example 1
79wt% Cu, 18wt% Ge and 3wt% Cu / B alloy (including 2wt% boron) are melted and mixed to make a master alloy. Cu melts with the Cu / B master alloy. High temperatures can be used because there are no other elements to be damaged. The temperature is then lowered, and germanium is added when the temperature reaches just above the melting point of Ge. Then, melting occurs in the descending order of the melting point, that is, in the order of copper / copper-boron mother alloy / germanium. The resulting master alloy contains about 82 wt% Cu, about 18 wt% Ge, and about 0.03 wt% boron, excluding impurities and taking into account the 50% boron content lost by melting, In addition, all impurities are included.

  After that, 72g of the above-mentioned master alloy and 928g of pure silver with a purity of 9999 were melted and mixed at a temperature just above the melting point of pure silver (eg about 960-1200 ° C), resulting in a 50% boron loss. To obtain the desired silver / copper / germanium ternary alloy which is a composition of about 92.8 wt% Ag, 5.90 wt% Cu, 1.30 wt% Ge, and about 11 ppm boron. To melt the master alloy, weigh it and put it in a crucible, weigh pure silver and put it in the crucible, and then heat it while flowing natural gas to protect it from unwanted oxidation. Melt. It is known that silver has an affinity for oxygen, and that the affinity increases as the temperature rises. When exposed to the atmosphere, molten silver can absorb about 22 times its volume of oxygen. Also, like silver, copper has a high affinity for oxygen and usually forms copper oxide. Therefore, care must be taken to prevent oxidation when forming or remelting sterling silver and other silver-copper alloys. When the mixture is melted, it is stirred with, for example, a carbon rod and cast into water through a storage weir, so that the silver has a diameter of about 3 to 6 mm, which is a normal sales form of sterling silver. Solidify as bullet-shaped granules or pellets.

  The obtained alloy particles are used for investment casting by a technique according to the prior art, and are cast at a temperature of 950 to 980 ° C., a mold temperature of 676 ° C. or less, and a protective atmosphere. Using an investment material with a relatively low thermal conductivity, the cast piece can be cooled slowly. After casting for 15 to 25 minutes with air casting for 15 to 25 minutes and quenching the investment casting frame with water, a cast piece with about 70 Vickers hardness is obtained, which is almost equal to the hardness of sterling silver equal. This product has an excellent resistance to fogging and burning, and has a fine crystal structure because it has a boron component. Further, it has been discovered that a cast piece with higher hardness can be produced by allowing the cast frame to cool to room temperature in the atmosphere, and this cast piece taken out from the mold has a hardness of about 110 Vickers. In contrast to experimental results performed with sterling silver, the hardness can be further increased by precipitation hardening if necessary, for example, casting or the entire tree in a furnace set at about 300 ° C. for 20-45 minutes. It is possible to raise the hardness of the heat-treated casting to 125 Vickers by putting it over the range. The germanium content is close to the upper limit considered desirable for the 0.925 type alloy according to the present invention.

  As another method, a master alloy and small granular pure silver are mixed in a crucible and directly cast into an investment mold to obtain the same as described above.

(Example 2)
Pure silver particles and the mother alloy having the ratio described in Example 1 are formed as sheet metal by continuous casting at 1150 to 1200 ° C. Sheet metal pieces are brazed together to form a molded product through the path of the brazing furnace and simultaneously annealed. In the cooling region downstream in the furnace, controlled slow air cooling is performed, so that precipitation hardening proceeds without performing a quenching step. For this purpose, it is desirable to expose the material to a temperature in the range of 200-300 ° C. (most preferred for precipitation hardening) for at least 8-30 minutes. Products that are brazed in the furnace in this manner and cooled slowly can obtain a hardness of 110 to 115 Vickers.

Example 3
The second master alloy is made by melting and mixing 81.5 wt% Cu, 15.5 wt% Ge, and 3 wt% Cu / B alloy (containing 2 wt% boron). The resulting master alloy contains about 84.5 wt% Cu, about 15.5 wt% Ge, and about 0.03 wt% boron, excluding impurities and taking into account the 50% boron content lost by melting. Including impurities.

  After that, 72 g of the second mother alloy and 928 g of 9999 silver were melted and mixed at about 960-1200 ° C., and after loss of 50% boron, about 92.8 wt% Ag and 6.08 wt% Cu And the desired silver / copper / germanium ternary alloy which is a composition of 1.12 wt% Ge and about 11 ppm boron. The performance of the alloy thus obtained is the same as that of Example 1. The germanium content is close to the lower limit considered desirable for the 0.925 type alloy according to the present invention.

(Example 4)
A mother alloy is made by melting and mixing copper and germanium according to the ratio shown in Example 1. Copper is melted by heating to about 1150 ° in a gas flame furnace or induction furnace while flowing a melt cover with charcoal that gives a reducing atmosphere. Germanium is added to copper by wrapping a piece of germanium in copper foil and placing it in the bottom of the melt using a graphite or graphite stir bar. When the copper addition is complete, lower the temperature to 1100 ° C, wrap the pellets of sodium borohydride giving 0.5wt% boron in copper foil, and use the graphite or graphite stir bar as described above to the bottom of the melt And put in. Sodium borohydride decomposes in 1-2 minutes while generating hydrogen, leaving boron and some sodium in the melt.

  After adding boron, the crucible is tilted so that the molten alloy can be cast into a reservoir weir with very fine holes in the bottom. The molten alloy is cast into a reservoir weir so that it flows in a thin stream through the pores, falls into a water agitation tank, is scattered in small particles and solidified to be cooled. The cast grain is taken out from the water tank and dried to obtain a mother alloy as a crystal for casting. The mother alloy described above can be used to produce an Ag—Cu—Ge alloy containing boron as a crystal refiner, and can be produced, for example, using the procedure described in the previous examples. The technique of using boron hydride to disperse boron in the master alloy is very efficient, and the resulting silver alloy can contain up to 20 ppm boron, or more than 20 ppm if desired. Boron can also be included without hard spot growth.

  In particular, the example procedure can be used to produce Ag-Cu-Ge casting crystals for a Stirling type alloy containing about 40 ppm boron. Boron loss in the remelting process reduces the boron content of the finished cast alloy to less than 20 ppm, but it is still sufficient for crystal refinement, and this boron component also contributes to castings, The possibility to create more consistent microstructure and properties in castings or other products.

Example 5
The procedure of Example 4 is repeated except that silicon is added in an amount such that 0.05-0.2 wt% Si is included as an incidental component in the alloy to be finished before boron is added.

Example 6
56 wt% Cu, 28 wt% Ag, 13 wt% Ge, and 3 wt% Cu / B alloy (including 2 wt% boron) are melted and mixed to make a master alloy. Cu (mp 1085 ° C) melts together with the Cu / B master alloy. High temperatures can be used because there are no other elements to be damaged. The temperature is then lowered, silver (mp 962 ° C.) is added, and germanium is added when the temperature reaches just above the melting point of Ge (mp 938 ° C.). Then, melting occurs in the descending order of the melting point, that is, in the order of copper / copper-boron mother alloy / silver / germanium. The resulting master alloy contains about 0.03 wt% boron.

  Then, 100 g of the above-mentioned master alloy and 900 g of pure silver of 9999 purity are melted and mixed at a temperature just above the melting point of pure silver (for example, about 960 to 1200 ° C.), resulting in a loss of 50% boron. Then, the desired silver / copper / germanium ternary alloy is obtained in the same manner as in Example 1. In the same manner as described in Example 1, the mother alloy is added to pure silver, and as described in Example 1, alloy particles that can be used for investment casting are formed as described in Example 1.

Example 7
59 wt% Cu, 28 wt% Ag, and 13 wt% Ge are melted and mixed to make a master alloy. Thereafter, sodium borohydride is introduced into the alloy as described in Example 4 so that the boron content is about 1000-1100 ppm. The mother alloy is used to produce Sterling grade jewelry or silverworking alloys as described in Example 7.

(Example 8)
While following the method of Example 7, modification is made so that sodium borohydride is wrapped in silver foil and introduced into the mother alloy.

Claims (40)

A base metal material for making a silver alloy containing 77 wt% or more of Ag and 0.5 wt% or more of Ge mixed with silver,
Base metal comprising Cu, Ge, optionally 0-30 wt% Ag, and 0.001-0.3 wt% boron, together with all further optional components and contaminants for the alloy material. Metal according to claim 1, characterized in that it contains 80-95wt% Cu (or Cu with further components for the alloy) and 20-5wt% Ge. Metal according to claim 1, characterized in that it contains 80-86.7wt% Cu (or Cu with further components for the alloy) and 20-13.3wt% Ge. The metal according to claim 1, characterized in that it comprises 82 to 84.5 wt% Cu and further optional components for said alloy and 15.5 to 18 wt% Ge.   A metal according to any one of the preceding claims, characterized in that it contains about 0.03 wt% B.   The metal according to any one of the preceding claims, characterized in that it contains only copper, germanium, boron and impurities. Contains 77 wt% or more of Ag, 1 to 7.2 wt% of Cu (copper), 0.5 wt% or more of Ge, 0.005 to 0.3 wt% of B, and further contamination with further optional components for the alloy A method for making a silver alloy that contains everything together,
A method comprising melting together pure silver and a base metal material which is a ternary alloy of at least copper, germanium and boron.   The method of claim 7, wherein the silver alloy is an alloy of silver, copper, and germanium.   The alloy is 80 to 96% silver, 0.1 to 5% germanium, and 1 to 19.9%, based on the weight of the alloy, except for impurities, incidental components, and all grain refiners. 9. A method according to claim 8, characterized in that it consists of   The alloy is 92.5 to 98% silver, 0.3 to 3% germanium, and 1 to 7.2% copper, based on the weight of the alloy, excluding impurities, incidental components and crystal refining agents. And further comprising 1 to 40 ppm of boron as a crystal refining agent.   The alloy is 92.5 to 96% silver, 0.5 to 2% germanium, and 1 to 7% copper, based on the weight of the alloy, excluding impurities, incidental components and crystal refining agents. And further comprising 1 to 20 ppm boron as a crystal refiner.   The alloy includes 92.5-92.8 wt% Ag, 6.0-6.3 wt% Cu, about 1.2 wt% Ge, and 1-15 ppm boron as a crystal refining agent, The method of claim 8. 13. The method according to any one of claims 7 to 12, further comprising the step of air cooling and hardening the silver alloy product after annealing and / or brazing in a furnace.   The method according to claim 13, characterized in that the silver alloy is annealed and / or brazed by heating to 600-680 ° C. in a furnace.   The method according to claim 13, characterized in that the silver alloy is annealed and / or brazed by heating to 600-660 ° C. in a furnace.   The method according to any one of claims 13 to 15, characterized in that the silver alloy is annealed and / or brazed at a temperature of 600 to 650 ° C.   14. A method according to claim 13, characterized in that annealing is performed during investment casting and then the investment is cured by air cooling or by cooling in air.   The method according to claim 17, wherein the product is a jewelry or a gift. A base metal material used to make a silver alloy containing 77 wt% or more of Ag and 0.5 wt% or more of Ge mixed with silver,
A base metal material comprising Cu, Ge and 0.005-0.5 wt% boron, together with all further optional components and impurities for the alloy. A method for producing a master alloy used to make a precious metal product,
The molten master alloy prior to solidification with a compound selected from the group consisting of alkylated boron compounds, boron hydrides, boron halides, boron-containing metal hydrides, boron-containing metal halides, and mixtures thereof A method characterized by processing.   The mother alloy is based on Cu, Cu-Ge, Cu-Ag, or Cu-Ag-Ge, and Al, Ba, Be, Cd, Co, Cr, Er, Ga, In, Mg, Mn, Ni, 21. The method according to claim 20, characterized by optionally including one or more incidental component elements selected from Pb, Pd, Pt, Si, Sn, Ti, V, Y, Yb, Zn, and Zr. Method.   The method according to claim 20 or 21, characterized in that the master alloy is treated with borane which is solid at ambient temperature.   The method according to claim 20 or 21, characterized in that the mother alloy before solidification is treated with a metal borohydride.   The method according to claim 20 or 21, characterized in that the mother alloy before solidification is treated with sodium borohydride. The mother alloy before solidifying,
Borane or borohydride metal that is solid at ambient temperature is wrapped in copper foil or silver foil, and then the wrapped borane or borohydride metal is treated by being put into the molten noble metal. 26. A method according to any one of claims 20 to 25, characterized in that 26. A method according to any one of claims 20 to 25, further comprising solidifying the molten metal as casting grains. A method for casting a master alloy containing at least Cu and B,
(A) forming a precursor master melt containing at least Cu;
(B) Dispersing a compound selected from the group consisting of alkyl boron compounds, boron hydrides, boron halides, boron-containing metal hydrides, boron-containing metal halides, and mixtures thereof throughout the mother melt. And steps to
And (c) solidifying the molten metal. The step of dispersing the boron compound in the precursor melt by passing an inert carrier gas containing gaseous boron hydride or boron halide through the melt. 27. The method according to 27.   29. The method of claim 28, wherein the boron compound is one or more selected from boron trifluoride, diborane, and trimethyl boron.   The boron compound is dissolved in a liquid phase and optionally in an inert organic solvent and introduced into the precursor melt, and the boron compound is made of silver foil or copper foil. 28. The method of claim 27, wherein the method is enclosed in one or more containers made of an inert pyrolytic substance.   The boron compound is selected from triethylborane, tripropylborane, tri-n-butylborane, methoxydiethylborane, and a system in which any of them is dispersed in hexane or THF. 30. The method according to 30.   28. The method of claim 27, wherein the boron compound is a higher borane that is solid at ambient temperature.   33. A method according to claim 32, characterized in that the boron compound is decaborane. The metal component of the boron-containing metal hydride is selected from the group consisting of sodium, lithium, potassium, calcium, zinc, and mixtures thereof; and
The method of claim 32, wherein the metal component of the boron-containing metal fluoride is sodium.   The process according to claim 32, characterized in that sodium borohydride is selected as the compound. The method further includes wrapping the boron hydride, the boron-containing hydride metal, or the boron-containing metal halide in a copper foil or a silver foil before being dispersed in the precursor alloy melt. 35. The method of claim 32.   37. The method according to claim 36, wherein a thickness of 0.01 mm to 0.3 mm is selected as the metal foil. The dispersing step (b)
33. The method of claim 32, comprising stirring for an amount of time effective to disperse boron throughout the noble metal alloy or the master alloy. 28. The method of claim 27, further comprising transferring the noble metal alloy or the master alloy to a grain box.   The precursor alloy melt is 0-30 wt% Ag, 0-20 wt% Ge, 0-2 wt% Si, and as a balance, the weight ratio of copper or copper to zinc is 1: 1. 28. A method according to claim 27, comprising a mixture of copper and zinc not exceeding.