Low-melting-point 18K gold material and manufacturing process and application thereof

Abstract

The invention discloses a low-melting-point 18K gold material and a manufacturing process and application thereof, belongs to the technical field of alloy materials, and aims to solve the technical problem that the mechanical strength of an alloy is reduced while the melting point is reduced in the prior art. The low-melting-point 18K gold material consists of the following components: 75.0 percent of Au, 8.0 percent to 12.0 percent of Ag, 4.5 percent to 6.5 percent of Cu, 2.0 percent to 3.0 percent of Ge, 1.5 percent to 3.0 percent of Pd, 2.0 percent to 4.0 percent of Zn, 0.1 percent to 0.5 percent of Si, 0.1 percent to 0.3 percent of C and inevitable impurities of which the total amount is not more than 0.2 percent. Niobium pentoxide is added in the smelting process, carbon monoxide can be oxidized into carbon dioxide in the smelting process in gold melt, emission of carbon monoxide is reduced, and the smelting process is more environmentally friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alloy materials, in particular to a low-melting-point 18K gold material, a manufacturing process thereof and an application thereof. BACKGROUND

[0002] 18K gold is an alloy formed by smelting gold and other metals. Its core material is composed of 75 wt% pure alloy and 25 wt% other metals; its specific composition is composed according to color requirements, and common other metal elements include silver, copper, zinc, nickel, palladium, and per. Compared with pure gold, 18K gold can improve hardness, enhance ductility, and reduce cost by adding other metal elements.

[0003] 18K gold (gold content 75 wt%) has become one of the most mainstream materials in the jewelry manufacturing industry due to its good balance of color, hardness, and price. The melting point of traditional 18K gold alloy (such as 18K yellow gold, usually composed of 75% gold, 15% silver, and 10% copper) is usually between 880°C and 920°C. The high melting point brings a series of problems: High energy consumption: higher temperature is required for smelting, increasing energy consumption and production cost.

[0004] Complex process: high temperature requires higher refractoriness of smelting crucible and casting mold, and is easy to cause oxidation and air absorption of the metal liquid, resulting in casting defects such as pores and shrinkage.

[0005] Currently, there have been some studies on reducing the melting point of gold alloy by adding low-melting-point metals (such as zinc, tin, and indium). However, these additions often come at the expense of other properties of the alloy, for example: Excessive addition of zinc and tin will cause the alloy to become brittle and the processing performance to deteriorate.

[0006] Some elements (such as cadmium) can effectively reduce the melting point and improve the flowability, but they are toxic to the human body and have been banned by the industry.

[0007] Some elements (such as indium) are high in cost and are not suitable for large-scale commercial application.

[0008] In order to increase the mechanical strength, hardness, and wear resistance of the alloy, carbon materials are often added during the smelting process, and the addition of carbon materials will cause the generation of CO during the smelting process, which does not meet the environmental protection requirements.

[0009] Therefore, it is a technical problem to be solved in the field to develop a new alloy that can significantly reduce the melting point while maintaining or even improving the casting performance, mechanical properties, and environmental protection of 18K gold alloy. SUMMARY

[0010] The present application aims to provide a low-melting-point 18K gold material, a manufacturing process thereof and an application thereof, and solve the technical problem of reducing the melting point while reducing the mechanical strength of the alloy in the prior art.

[0011] The present application can achieve the above-mentioned purpose by the following technical solution: a low-melting-point 18K gold material, consisting of the following components in percentage by weight: Au 75.0%; Ag 8.0% - 12.0%; Cu 4.5% - 6.5%; Ge 2.0% - 3.0%; Pd 1.5% - 3.0%; Zn 2.0% - 4.0%; Si 0.1% - 0.5%; C 0.1% - 0.3%; and unavoidable impurities in a total amount of not more than 0.2%; The low-melting-point 18K gold material is added with a carbon conversion material in the smelting process, and the carbon conversion material is a metal oxide.

[0012] The present application also provides a manufacturing process of a low-melting-point 18K gold material, comprising the following steps: a) proportionally weighing gold, silver, copper and palladium raw materials according to the mass percentage of the formula; b) heating and melting the raw materials in step a) under vacuum or a protective atmosphere to form a mother alloy liquid; c) adding zinc, silicon and germanium elements to the mother alloy liquid, stirring and mixing uniformly, then adding a carbon conversion material, stirring and mixing uniformly, and after the reaction is completed, filtering the carbon conversion material to obtain an alloy melt; d) pouring the alloy melt into an ingot; e) performing homogenization heat treatment on the ingot.

[0013] Further, the protective atmosphere in step b) is argon, and the smelting temperature is 1000-1050℃.

[0014] Further, the zinc and silicon elements in step c) are added in the form of a zinc-silicon intermediate alloy.

[0015] Further, the carbon and germanium in step c) are added in the form of a germanium and reduced graphene oxide composite material, and the preparation method of the germanium and reduced graphene oxide composite material is as follows: The dry powder mixture is heated to 900℃ at a heating rate of 5℃ / min in a continuous argon stream and held for 1 hour, then cooled to room temperature at a cooling rate of 5℃ / min to obtain a composite of germanium and reduced graphene oxide.

[0016] Further, the carbon conversion material in step c) is niobium pentoxide.

[0017] Further, the pouring temperature in step d) is 880-920℃.

[0018] Further, the homogenization heat treatment condition in step e) is: holding at 680-720℃ for 3-5 hours, followed by cooling.

[0019] The present application has the following advantages: 1. The melting point of the alloy is generally lower than that of the constituent metal. The addition of other metal atoms increases the crystal lattice defects, thereby reducing the melting point. By introducing a metal with a lower melting point, a eutectic mixture or solid solution is formed.

[0020] 2. Through the synergistic melting point reduction effect of Pd-Si-Zn, the solidus temperature of the 18K gold alloy of the present application can be reduced to 800-820℃, and the liquidus temperature can be reduced to 850-870℃, which is about 60℃ lower than that of the traditional 18K gold alloy.

[0021] 3. The addition of palladium effectively neutralizes the copper red color, and the obtained alloy has pure color, which meets the aesthetic demand of the market for gold jewelry.

[0022] 4. The lower melting point and the addition of silicon greatly improve the fluidity of the molten liquid and the filling ability of the casting, reduce casting defects, and have good surface finish, which is very suitable for precision jewelry casting.

[0023] 5. After smelting and heat treatment of the alloy with increased graphene material, the alloy has good strength and moderate toughness, which meets the requirements of jewelry processing (such as filing, sawing, and forging).

[0024] 6. The addition of niobium pentoxide in the smelting process can oxidize carbon monoxide to carbon dioxide in the gold melt during smelting, reducing carbon monoxide emissions and making the smelting process more environmentally friendly. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] Example 1 The present example provides a manufacturing process of low melting point 18K gold material, comprising the following steps: a) proportionally weigh gold 75%, silver 10.7%, copper 6%, palladium 2% raw materials according to the formula mass percentage; b) heat the raw materials of step a) to 1050℃ under nitrogen atmosphere to melt and form a master alloy liquid; c) add zinc 3%, silicon 0.3% zinc-silicon intermediate alloy and 3.0% germanium and reduced graphene oxide composite to the master alloy liquid, stir and mix uniformly, then add 1% niobium pentoxide of the added amount of germanium and reduced graphene oxide composite, stir and mix uniformly, continue to react for 30 min, filter the niobium pentoxide to obtain an alloy melt; d) pour the alloy melt into ingots, the pouring temperature is 900℃; e) homogenize the ingot by heat treatment, the homogenization heat treatment condition is: 700℃ for 4 hours, then cool down.

[0027] Example 2 The present example provides a manufacturing process of low melting point 18K gold material, comprising the following steps: a) proportionally weigh gold 75%, silver 11%, copper 6%, palladium 2.2% raw materials according to the formula mass percentage; b) heat the raw materials of step a) to 1050℃ under nitrogen atmosphere to melt and form a master alloy liquid; c) add zinc 3%, silicon 0.3% zinc-silicon intermediate alloy and 2.5% germanium and reduced graphene oxide composite to the master alloy liquid, stir and mix uniformly, then add 1% niobium pentoxide of the added amount of germanium and reduced graphene oxide composite, stir and mix uniformly, continue to react for 30 min, filter the niobium pentoxide to obtain an alloy melt; d) pour the alloy melt into ingots, the pouring temperature is 900℃; e) homogenize the ingot by heat treatment, the homogenization heat treatment condition is: 700℃ for 4 hours, then cool down.

[0028] Example 3 The present example provides a manufacturing process of low melting point 18K gold material, comprising the following steps: a) proportionally weigh gold 75%, silver 10%, copper 6.7%, palladium 2% raw materials according to the formula mass percentage; b) heat the raw materials of step a) to 1050℃ under nitrogen atmosphere to melt and form a master alloy liquid; c) adding 3% zinc, 0.3% silicon zinc-silicon intermediate alloy and 3.0% germanium and reduced graphene oxide composite to the mother alloy liquid, stirring and mixing uniformly, then adding 1% niobium pentoxide of the amount of germanium and reduced graphene oxide composite, stirring and mixing uniformly, continuing to react for 30 min, filtering the niobium pentoxide to obtain an alloy melt; d) pouring the alloy melt into an ingot, and the pouring temperature is 900°C; e) subjecting the ingot to homogenization heat treatment, and the homogenization heat treatment conditions are: 700°C for 4 hours, and then cooling.

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is that no carbon conversion material is added in step c).

[0030] Comparative Example 2 The difference between this comparative example and Example 1 is that the germanium is added in the form of germanium alloy in step c), and no carbon element is added.

[0031] Performance test: The performance of the alloy of Example 1 and the comparative example is tested, I. Hardness test: equipment (name: microhardness tester; model: HV-1000Z).

[0032] Detection method: 1. The sample is made into a sample size of 0.5*0.5*1mm; 2. The sample is inlaid and molded; 3. The sample is polished with 1000, 2000, 3000 and 5000 mesh sandpaper in turn; 4. The sample hardness is detected by a microhardness tester; equipment parameter setting: test force 50g; magnification 40X; holding time 10s; measurement scale HV.

[0033] II. Tensile strength test: equipment (name: desktop tensile testing machine; model: HD-601).

[0034] Detection method: 1. The sample is made into a sample bar of 4*4*30mm; 2. The sample is clamped to the equipment clamp; 3. The value is recorded by the testing machine; equipment parameter setting: test speed 0.1-1mm / min (displacement speed); stop condition is to be pulled apart.

[0035] The results are shown in Table 1 below: Table 1

[0036] The melting point (liquid / solidus) of the alloy of Example 1 is significantly lower than that of Comparative Example 3, with a decrease of more than 60°C.

[0037] The mechanical strength is higher than traditional 18K gold, the elongation rate is slightly decreased, but still in excellent level (20%), fully meeting the requirements of all jewelry manufacturing processes. The casting fluidity is increased by 20%, which means that more complex structure and more exquisite details of jewelry can be produced.

[0038] The CO oxidation catalysis test was carried out in a fixed bed glass reactor loaded with 0.15 g of carbon conversion material sample (weight hourly space velocity (WHSV) = 20000 mL h -1 g -1 ), and the reaction gas containing 1vol% CO in air was directly sent from a steel cylinder without purification. In all cases, the pretreatment was carried out at 250℃ for 1 hour in a dry air stream at a flow rate of 50 mL / min. After pretreatment, the carbon conversion material sample was cooled to room temperature, and then the raw material gas was converted into reaction gas at various temperatures under a total pressure of 0.1 MPa. The inlet and outlet gases were analyzed by online gas chromatography (Shimadzu GC-8A equipped with TCD and molecular sieve 13X chromatographic column) to obtain the conversion rate of CO, which was calculated to be 34%, which means that the carbon conversion material prepared in the application has a certain effect in the oxidation of CO.

[0039] In summary, the application successfully provides a low-melting-point 18K gold material with excellent comprehensive performance, which has great application potential and market prospect in the field of jewelry manufacturing.

[0040] The above is only an example and description of the structure of the application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the structure of the application or exceed the scope defined by the claims.

[0041] In the description of the present specification, the description referring to the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0042] The preferred embodiments of the application disclosed above are only to facilitate the elucidation of the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments. Obviously, many modifications and variations can be made in light of the teachings above. The description is chosen and described in order to provide the best illustration of the application and its practical application to those skilled in the art and to enable those skilled in the art to utilize the application in its best mode. The application is only limited by the claims and their full scope and equivalents.

Claims

1. A low melting point 18K gold material, characterized in that: In terms of weight percentage, the low melting point 18K gold material consists of the following components: Au 75.0%; Ag 8.0% - 12.0%; Cu 4.5% - 6.5%; Ge 2.0% - 3.0%; Pd 1.5% - 3.0%; Zn 2.0% - 4.0%; Si 0.1% - 0.5%; C 0.1% - 0.3%； and unavoidable impurities not exceeding 0.2% in total; The low-melting-point 18K gold material is added with a carbon conversion material during the smelting process, and the carbon conversion material is a metal oxide.

2. The manufacturing process of the low melting point 18K gold material according to claim 1, characterized in that: The following steps are involved: a) Weighing gold, silver, copper and palladium raw materials according to the formula mass percentage; b) heating and melting the raw materials from step a) under vacuum or protective atmosphere to form a master alloy liquid; c) adding zinc, silicon, carbon, and germanium to the master alloy liquid, stirring and mixing uniformly, then adding a carbon conversion material, stirring and mixing uniformly, and filtering the carbon conversion material after the reaction is completed to obtain an alloy melt; d) pouring the alloy melt into an ingot; e) performing a homogenization heat treatment on the ingot.

3. The manufacturing process of the low melting point 18K gold material according to claim 2, characterized in that: In step b), the protective atmosphere is argon, and the melting temperature is 1000-1050°C.

4. The manufacturing process of the low melting point 18K gold material according to claim 2, characterized in that: In step c), the zinc and silicon elements are added in the form of zinc-silicon master alloy.

5. The manufacturing process of the low melting point 18K gold material according to claim 2, characterized in that: In step c), the carbon and germanium are added in the form of a composite material of germanium and reduced graphene oxide, wherein the composite material of germanium and reduced graphene oxide is prepared as follows: Germanium dioxide and graphene oxide dry powders were mechanically mixed in a molar ratio of 1:4 to obtain a dry powder mixture. The dry powder mixture was heated to 900°C in a continuous argon flow at a heating rate of 5°C / min and maintained for 1 hour, and then cooled to room temperature at a cooling rate of 5°C / min to obtain a composite material of germanium and reduced graphene oxide.

6. The manufacturing process of the low melting point 18K gold material according to claim 2, characterized in that: The carbon conversion material in step c) is niobium pentoxide.

7. The manufacturing process of the low melting point 18K gold material according to claim 2, characterized in that: The pouring temperature in step d) is 880-920°C.

8. The manufacturing process of the low melting point 18K gold material according to claim 2, characterized in that: The homogenization heat treatment conditions in step e) are: keeping the temperature at 680-720° C. for 3-5 hours, and then cooling.

9. A jewelry product, characterized in that: Made of the low-melting-point 18K gold material according to claim 1 or 2.

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