GOLD ALLOY INCLUDING HARDNESS IMPROVING ELEMENTS

Abstract

The present disclosure provides for a gold alloy composition that has a greater hardness than conventional gold alloys of the same composition. The gold alloy composition includes 96.4-97% gold by weight. The composition also includes elements improving hardness and golden yellow color in the proportion of 3-3.6% by weight, which are one or more elements among: silver, copper, zinc, nickel, cobalt, gallium, tin, antimony, and iron. The composition also includes elements improving the flowing of melted gold alloy and surface smoothness, which are one or more elements among: iridium, palladium, aluminum, indium, silicon, germanium and lead. An example procedure is also provided to increase the hardness of gold alloys.

Claims

1. A gold alloy composition with hardness improving elements comprising: gold (Au), wherein gold is 96.4-97% by weight of the composition; one or more hardness improving elements selected from the group including: copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), gallium (Ga), tin (Sn), antimony (Sb) and iron (Fe), wherein the one or more hardness improving elements is between 0.1-3.6% by weight of the composition; one or more flow improving elements selected from the group including: iridium (Ir), palladium (Pd), aluminum (Al), indium (In), silicon (Si), germanium (Ge) and lead (Pb), wherein the one or more flow improving elements is between 0.0-0.1% by weight of the composition; and silver (Ag), wherein the silver (Ag) is a percentage by weight of the composition that refines the proportion of all components to 100%.

2. The gold alloy composition of claim 1, wherein the one or more hardness improving elements selected from a group consisting of copper (Cu) or zinc (Zn) or both, and wherein the copper (Cu), zinc (Zn), or both is between 0.5-3.6% by weight of the composition.

3. The gold alloy composition of claim 1, wherein the gold is 96.5% of the composition by weight.

4. The gold alloy composition of claim 1, wherein the one or more hardness improving elements is 0.5-2.1% by weight of the composition.

5. The gold alloy composition of claim 1, wherein the silver (Ag) is between 1.4-3% by weight of the composition.

6. The gold alloy composition of claim 1, wherein gold (Au) is 96.5%, the one or more hardness improving elements is between 0.5-2.1%, and the silver (Ag) is between 1.4-3% by weight of the composition, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present disclosure provides for a gold alloy including 96.4% to 97% gold by weight and the remaining percentage including other elements, such as hardness improving elements. The other elements may improve various properties of the gold alloy or the production of the gold alloy. In some examples of the present disclosure, the gold is mixed or diluted with the hardness improving elements.

[0016] In some examples, hardness improving elements are provided in the proportion of 0.1-3.6% by weight. The hardness improving elements are selected from one or more elements among: copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), gallium (Ga), tin (Sn), antimony (Sb), and iron (Fe). In some examples, if only copper (Cu) or zinc (Zn) or both are selected, then the proportion by weight of copper (Cu) and zinc (Zn) is 0.5 to 3.6%.

[0017] In some examples, elements improving the flowing of a melted gold alloy in the production process, reducing the shrinkage, and/or improving the surface quality of a workpiece are provided in a proportion of 0.0-0.1% by weight. These elements are selected from one or more of: iridium (Ir), palladium (Pd), aluminum (Al), indium (In), silicon (Si), germanium (Ge) and lead (Pb).

[0018] In some examples, silver (Ag) is used as a composition to refine the proportion of all components in the gold alloy to 100% by weight. In such examples, silver (Ag) is provided in proportion of 0-3.5% by weight. For example, if the above described elements compose 98% of the gold alloy composition by weight, then silver (Ag) is 2% by weight of the composition.

[0019] In at least one aspect of the present disclosure, an example gold alloy includes 96.5% gold by weight. The example gold alloy also includes 0.5-2.1% by weight of one or more elements among: copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), gallium (Ga), tin (Sn), antimony (Sb), and iron (Fe). The selected combination of copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), gallium (Ga), tin (Sn), antimony (Sb), and iron (Fe) is at least 0.5% by weight in order to achieve the desired hardness of the gold alloy but does not exceed 2.1% by weight to maintain the desired color of the gold alloy. The example gold alloy also includes 0.0-0.1% by weight of one or more elements among: iridium (Ir), palladium (Pd), aluminum (Al), indium (In), silicon (Si), germanium (Ge) and lead (Pb). The example gold alloy also includes 1.4-3% by weight of silver (Ag). If silver (Ag) is less than 1.75% by weight, the color of the gold alloy changes and is not as shiny yellow. If silver (Ag) is more than 3% by weight, the combination of hardness improving elements i.e., copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), gallium (Ga), tin (Sn), antimony (Sb) and iron (Fe) decreases resulting in reduced hardness of the gold alloy.

[0020] The presently disclosed gold alloy including hardness improving elements has a higher hardness than conventional 96.5% gold alloys which contain the same gold proportion (as shown in Table 2). In some aspects of the present disclosure, the gold alloy is produced using a procedure to increase the hardness of the gold alloy. The procedure includes forming the gold alloy by solution treatment at a temperature of 750-800 C. for 1 hour, then quenching the gold alloy in water and aging it again at a temperature of 250-350 C. for 1-2 hours. The procedure then includes cooling the gold alloy down in water or air. The preceding steps help increase the hardness of the whole work piece. The procedure then includes processing the gold alloy through a general tumbling machine which helps increase the hardness of the workpiece surface.

[0021] In the jewelry industry, the hardness of metal is generally indicated by the Vickers Hardness Test, which is measured in units of HV. Table 2 below shows samples of gold alloy compositions and the corresponding results for each of a Vickers hardness test in units of HV. Process A included a solution treatment at 760 C. for 1 hour then quenching the gold alloy in water and aging it again at 300 C. for 90 minutes. Process B included a solution treatment at 760 C. for 1 hour then quenching the gold alloy in water, aging it again at 300 C. for 90 minutes, and then grinding the gold alloy by a tumbling machine for 2 hours.

TABLE-US-00002 TABLE 2 Vickers hardness of each metal alloy Compositions (HV 0.05) (by weight in After Post Post Gold Alloy percentage) casting Process A Process B 1 Au 75, Ag 11.5, 161.8 (18K Gold) Cu 12.52 2 Au 96.5, Ag 3.4, 37.9 38.9 61 (23.16K Gold) Cu 0.1 Conventional 3. Au 96.5, Ag 1.4, 79.3 133.6 182.8 (23.16K Gold) Ni 1.57, Ga 0.53 4 Au 96.5, Ag 1.4, 69.4 79.5 100.7 (23.16K Gold) Cu 0.26, Zn 0.26, Ni 0.26, Co 0.26, Ga 0.26, Sn 0.26, Sb 0.26, Fe 0.26 5 Au 96.5, Ag 2.1, 49.6 56.1 106.1 (23.16K Gold) Cu 0.17, Zn 0.17, Ni 0.17, Co 0.17, Ga 0.17, Sn 0.17, Sb 0.17, Fe 0.17

[0022] Sample 1 in the above Table 2 is a conventional 18K gold alloy with a hardness of 161.8 HV after a casting process. Sample 2 is a conventional 23.16K (i.e., 96.5% gold) gold alloy with a hardness of 37.9 HV after a casting process.

[0023] Even after being processed through processes A and B, the conventional 23.16K gold alloy only had a hardness of 38.9 HV and 61 HV, respectively.

[0024] The example samples 3-5 in the above Table 2 are example gold alloy compositions according to the present disclosure. In each example, the hardness of the presently disclosed gold alloy was greater than the conventional gold alloy of the same composition. In other examples, the compositions of the gold alloy may be different than the compositions in Table 2 according to the present disclosure.

[0025] Sample 3 is a 23.16K gold alloy with a hardness of 79.3 HV after a casting process. When sample 3 was processed through processes A or B, it had an even higher hardness of 133.6 HV and 182.8 HV, respectively. The level of hardness for sample 3 is very high, especially the B-processed gold alloy, as the hardness was almost at the same level with 18K gold alloy after casting.

[0026] Sample 4 is a 23.16K gold alloy with a hardness of 69.4 HV after a casting process. When it had been processed through processes A or B, the hardness increased to 79.5 HV and 100.7 HV, respectively.

[0027] Sample 5 is 23.16K gold alloy with a hardness of 49.6 HV after a casting process. When it had been processed through processes A or B, the hardness increased to 56.1 HV and 106.1 HV, respectively.

[0028] The presently disclosed gold alloy composition as described has a higher level of hardness compared to a conventional 23.16K gold alloy, which allows it to be formed into slim and complicated designs without breaking. The presently disclosed gold alloy composition additionally maintains physical characteristics (e.g., beautiful color, smooth surface) that are generally accepted in the gold market and the Thailand Office of the Consumer Protection Board (OCPB).