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EP-4735656-A1 - USE OF A SILVER ALLOY FOR THE REALIZATION OF PRECIOUS OBJECTS BY MEANS OF A PROCESSES BASED ON SINTERIZATION, AS WELL AS THE PRECIOUS OBJECT OBTAINED THEREWITH

EP4735656A1EP 4735656 A1EP4735656 A1EP 4735656A1EP-4735656-A1

Abstract

The use of a silver alloy for manufacturing precious objects by means of a process which includes the following steps: a) adding a polymeric binder to the silver alloy for providing a semi-finished product; and b) sintering the semi-finished product. Besides the common impurities, silver alloy consists of: 80.00 % by weight - 97.50 % by weight of Silver (Ag); 0.01 % by weight - 15.00 % by weight of Indium (In); 0.01 % by weight - 15.00 % by weight of at least one first further element consisting of: Tin (Sn), Gallium (Ga), Copper (Cu), Palladium (Rd), Platinum (Pt), Zinc (Zn), Silicon (Si). A precious object made starting from such silver alloy.

Inventors

  • FRISO, Andrea
  • BERTONCELLO, Riccardo
  • LAGO, Mattia

Assignees

  • Legor Group S.p.A.

Dates

Publication Date
20260506
Application Date
20240806

Claims (13)

  1. 1. The use of a silver alloy in powdered form for manufacturing precious objects through a process which includes the following steps: a) adding a binder to the silver alloy for providing a semi-finished product; b) sintering said semi-finished product; the silver alloy consisting of: (A) 80.00% by weight - 97.50% by weight of Silver (Ag); (B) 0.01% by weight - 15.00% by weight of Indium (In); (C) 0.01% by weight - 15.00% by weight of at least one first further element selected from the group consisting of: Tin (Sn), Gallium (Ga), Copper (Cu), Palladium (Pd), Platinum (Pt), Zinc (Zn), Silicon (Si); and the usual impurities; wherein if said at least one first further element (C) is Tin (Sn): • if the silver alloy contains (A) 80.00 % by weight - 85,00 % by weight of Silver (Ag), then (B) Indium (In) is comprised between 5.00 % by weight and 15.00 % by weight; (C) Tin (Sn) is comprised between 1.00 % by weight and 3.00 % by weight; (D) the silver alloy further comprises at least one second further element selected from the group consisting of: Copper (Cu), Palladium (Pd), Platinum (Pt); wherein said at least one first and one second further element (C + D) are present in the alloy in a percentage comprised between 5.00 % by weight and 15.00 % by weight; or • if the silver alloy contains (A) 90.00 % by weight - 97,50 % by weight of Silver (Ag), then (B) Indium (In) is comprised between 1.00 % by weight and 6.00 % by weight and (C) Tin (Sn) is comprised between 1.00 % by weight and 5.00 % by weight; wherein the percentages by weight are percentages by weight with respect to the total weight of the alloy.
  2. 2. Use according to the preceding claim, wherein: - if said at least a first further element (C) is Gallium (Ga), it is present in said silver alloy in a range comprised between 0.01% by weight and 4.00% by weight, and preferably comprised between 0. 01% by weight and 2.00% by weight; - if said at least one first further element (C) is Copper (Cu), it is present in said silver alloy in a range comprised between 0.01% by weight and 6.00% by weight; - if said at least one first further element (C) is Palladium (Pd), it is present in said silver alloy in a range comprised between 0.01% by weight and 5.00% by weight; - if said at least one first further element (C) is Platinum (Pt), it is present in said silver alloy in a range comprised between 0.01% by weight and 4.00% by weight; - if said at least one first further element (C) is Zinc (Zn), it is present in said silver alloy in a range comprised between 0.01% by weight and 1.00% by weight; - if said at least one first further element (C) is Silicon (Si), it is present in said silver alloy in a range comprised between 0.01% by weight and 0.20% by weight.
  3. 3. Use according to claim 1 or 2, wherein said at least one first further element (C) is tin (Sn), the silver alloy containing 80.00 % by weight - 85.00 % by weight of Silver (Ag), wherein: - if said at least one second further element (D) is Copper (Cu), it is present in said silver alloy in a range comprised between 2.00% by weight and 6.00% by weight; - if said at least one second further element (D) is Palladium (Pd), it is present in said silver alloy in a range comprised between 1.00% by weight and 5.00% by weight.
  4. 4. Use according to claim 1 or 2, wherein the silver alloy consists of: (A) 80.00% by weight - 85.00% by weight of Silver (Ag); (B) 5.00 % by weight - 15.00 % by weight, preferably 8.00 % by weight - 15.00 % by weight, of Indium (In); (C) 5.00 % by weight - 15.00 % by weight, preferably 8.00 % by weight - 15,00 % by weight, of said at least one first further element; wherein: - if said at least one first further element (C) is Copper (Cu), it is present in said silver alloy in a range comprised between 2.00% by weight and 6.00% by weight; - if said at least one first further element (C) is Palladium (Pd), it is present in said silver alloy in a range comprised between 1.00% by weight and 5.00% by weight.
  5. 5. Use according to claim 1 or 2, wherein the silver alloy consists of: (A) 90.00% by weight - 97.50% by weight of Silver (Ag); (B) 1.00 % by weight - 6.00 % by weight, preferably 1.50 % by weight - 5.00 % by weight, of Indium (In); (C) 1.00 % by weight - 6.00 % by weight, preferably 1.50 % by weight - 5,00 % by weight, of said at least one first further element; wherein: - if said at least one first further element (C) is Copper (Cu), it is present in said silver alloy in a range comprised between 1.00% by weight and 4.00% by weight; - if said at least one first further element (C) is Palladium (Pd), it is present in said silver alloy in a range comprised between 1.00% by weight and 4.50% by weight.
  6. 6. Use according to any one of the preceding claims, wherein said at least one first further element (C) is Tin (Sn).
  7. 7. Use according to any one of the preceding claims, wherein said alloy further comprises at least one second further element (D), the latter and said at least one first further element (C) being selected from the group consisting of Tin (Sn), Copper (Cu), Palladium (Pd) and Platinum (Pt).
  8. 8. Use according to any one of the preceding claims, wherein said silver alloy has a particle size measured in accordance with the ISO 13320:2020 standard comprised between 0.1 pm and 65 pm, and preferably comprised between 0.1 pm and 30 pm.
  9. 9. Use according to any one of the preceding claims, wherein in said silver alloy: - when the Silver (Ag) is comprised between 80.00 % by weight and 85.00 % by weight, Vickers as cast hardness measured in accordance with the ISO 6507-1:2018 standard is comprised between 100 HV and 130 HV; - when the Silver (Ag) is comprised between 90.00 % by weight and 97.50 % by weight, the Vickers as cast hardness measured in accordance with the ISO 6507-1:2018 standard is comprised between 40 HV and 60 HV.
  10. 10. Use according to any one of the preceding claims, wherein said process is selected from the group consisting of: binder jetting (BJ), metal injection moulding (MIM), lithographybased metal manufacturing (LMM), fused deposition modelling (FDM).
  11. 11. Use according to the preceding claim, wherein said sintering step is preceded by a de-binding step, the latter being carried out at a working temperature above 400 °C and preferably comprised between 400 °C and 500 °C, the sintering step being carried out at a working temperature above 800 °C and preferably comprised between 800 °C and 1000 °C.
  12. 12. A precious object obtained by means of a method comprising the steps of: a) providing the silver alloy defined in one or more of the preceding claims; b) adding a polymeric binder to said the silver alloy for providing a semi-finished product; c) sintering said semi-finished product.
  13. 13. Object according to the preceding claim, wherein the average residual porosity is less than 3%.

Description

USE OF A SILVER ALLOY FOR THE REALIZATION OF PRECIOUS OBJECTS BY MEANS OF A PROCESSED BASED ON SINTERIZATION, AS WELL AS THE PRECIOUS OBJECT OBTAINED THEREWITH DESCRIPTION Technical field of the invention The present invention generally relates to the technical field of jewellery, and it relates to the use of a silver alloy for manufacturing precious objects by means of a process based on sintering, as well as a precious object thus obtained. Definitions In the present document, the expression “Binder Jetting” also abbreviated with "BJ" is used to indicate an additive manufacturing process in which the powder is selectively soaked, after it has been spread a surface, with a binder in multiple layers to obtain a semi-finished product, called raw workpiece. Subsequently, the obtained raw workpiece should be densified through a thermal process referred to as sintering. In the present document, the expression “Metal Injection Moulding” also abbreviated with “MIM” is used to indicate a manufacturing process starting from powders where the metal powder is mixed with an appropriate binder and then injected into a pressing machine to obtain a semi-finished product, referred to as raw workpiece. The raw workpiece thus obtained is then densified by sintering. In the present document, the expression “Lithography-based Metal Manufacturing” also abbreviated with "LMM" is used to indicate a manufacturing process starting from powders based on the selective lithographic polymerisation of a binder to obtain a semifinished product, referred to as raw workpiece. The workpiece thus obtained is then densified by sintering. In the present document, the expression “Fused Deposition Modelling” also abbreviated with "FDM" is used to indicate a manufacturing process starting from powders based on the construction of three-dimensional shapes starting from thermoplastic polymer filaments containing metal powder. The raw workpiece thus obtained is then densified by sintering. In the present document, the expression "Semi-finished product" also referred to as "raw workpiece" is used to indicate an object resulting from the mould or injection process, consisting of a mixture of metal powder and binder, which already has the shape of the end object, but with lower mechanical strength than the end workpiece, which will result from the sintering process. In the present document, the expression "Debinding" is used to indicate an initial step of the sintering process, in which the polymeric binder required to hold the mass of metal powder together after the moulding, is removed. In the present document, the expression "Sintering" is used to indicate a process that is thermally activated due to which semi-finished product consisting of a mixture of metal powders and a binder is densified until there is obtained a compact solid object, by removing the binder and thermally or thermal-mechanically joining the powder particles. In the present document, the expression "consists" or its derivatives associated with a composition or product of interest made up of two or more components is used to indicate, unless indicated otherwise, that the product or composition in question is entirely made up of the listed components, that is the total of the listed components amount to 100% of the composition or of the product, except for the usual impurities generally present in that product or composition. In the present document, the expression "precious object" or its derivatives is used to indicate, unless indicated otherwise, a finished product, of any shape and size, resulting from the processing an alloy in a predefined manner. In the present document, the expression "percentage by weight" or "% by weight" or its derivatives is used to indicate, unless indicated otherwise, the percentage by weight of a component of interest with respect to the total weight of the composition in which the component of interest is included. State of the Art It is known that the conventional jewellery manufacturing technologies reveal problems relating to the type of drawings that can be obtained, the efficiency of the manufacturing processes in terms of proportion between the amount of alloy used and weight of the end object and surface quality. Various techniques have been designed to overcome these drawbacks. Among these, there is known the technology called binder jetting or metal binder jetting which enables, starting from a CAD drawing uploaded on a special printer, to obtain a large amount of semi-finished products called "raw workpieces" within a short time and with ultra-high repeatability due to the speed of the printer, then followed by a sintering process, which can also be carried out on a large number of workpieces. With an optimised process, the workpieces that are obtained are characterised by good surface quality and controlled dimensional tolerances. Sterling, the silver alloy conventionally used in the jewellery industry when used in the binder jetti