White gold alloy for high-temperature enamelled jewellery and preparation method of white gold alloy

Abstract

The invention discloses white gold alloy for high-temperature enamelled jewellery and a preparation method of the white gold alloy. The white gold alloy is prepared from, by weight, 75.0%-75.5% of gold, 7.0%-8.0% of nickel, 3.0%-4.0% of silver, 9.5%-10.5% of copper, 3.0%-3.5% of zinc, 0.3%-0.8% of palladium, 0.01%-0.03% of silicon, 0.008%-0.02% of scandium and other inevitable impurities. The preparation method of the white gold alloy comprises the steps that 1, raw materials are smelted under the protective atmosphere; 2, after all the materials are melted down, the temperature of molten metal is adjusted, and an ingot casting is obtained through casting; and 3, the ingot casting is rolled and then annealed. The color of the white gold alloy meets the requirement for the color index of K white gold well, and excellent vulcanization color change resistance is achieved; excellent high-temperature oxidation resistance is achieved, high-temperature firing can be borne better, and a transparent enameled layer obtained through firing has good transparency; the expansion factor is close to the heat expansion factor of common high-temperature glaze for gold; and the requirement of inlaid jewellery can be met well, the white gold alloy is fine in grain, and a highly-polished surface can be obtained.

Description

technical field [0001] The invention relates to a white gold alloy used for high-temperature enamel jewelry and a preparation method thereof. Background technique [0002] As a substitute for platinum, white gold alloy (commonly known as K platinum) has the advantages of cheaper price, higher strength, and better processing performance. It has been widely used in inlaid jewelry and has become the main material in gold alloy jewelry. Since gold is a golden yellow element, in order to effectively bleach the gold alloy, it is necessary to add alloy elements capable of effective bleaching to the alloy. Among all metal elements in nature, although except for a few elements such as Au and Cu, most of the other metal elements are white or gray, but there are very few metals that can be effectively used as bleaching elements for K platinum. Nickel and palladium are the main whitening elements of K platinum, silver and zinc are generally used as auxiliary whitening elements, and the...

AI Technical Summary

Problems solved by technology

However, the white grade of many K platinum on the market is poor. When the coating on the surface of the jewelry is worn, the original color of the base metal is exposed, which has a large contrast with the color of the coating, causing complaints or doubts from customers.

[0004] The second is that in the cold processing production of K platinum, it is easy to be troubled by two problems. Due to its higher hardness and lower ductility, intermediate annealing is required during processing

On the one hand, if the alloy is cooled slowly from the annealing temperature, it will form a two-phase structure, which will lead to cracks in the subsequent processing, so the amount of cold working deformation allowed between two annealings is reduced, and this will lead to a certain degree of deformation of the material section. The difference is that the processing deformation on the surface is large, while the central part is smaller, so that the internal stress distribution is uneven

This stress gradient can produce non-uniform grain size when the material is annealed, further affecting its cold workability

On the other hand, if the material is cooled rapidly from the annealing temperature, it is easy to generate significant quenching stress

[0005] The third is casting defects

When using commercial K platinum to fire transparent enamel, it is easy to have a large number of bubbles on the bottom of the enamel, the enamel surface is hazy, etc., and the serious oxidation of the base metal will also affect the color of the enamel.

When the combination of the fired enamel layer and the metal substrate is not strong enough, problems such as bursting and peeling will occur, especially in the electroplating process.

Once the enamel surface cracks or peels off, it takes a lot of effort to repair, which significantly increases the production cost

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