Anti-tarnish silver alloy and method for manufacturing the same

Abstract

Disclosed is a tarnish resistant silver alloy with the composition of (by wt%): silver 82.5-92.5%, cobalt 1.5-7.5%, nickel 0.5-2.5%, and copper 0.5-15%, wherein the weight ratio of cobalt and nickel is controlled within 2.5~3.5:1. The method for producing the silver alloy comprises the following steps: mixing raw materials according to the ratio, melting in a vacuum induction melting furnace, and then cooling to room-temperature to form cast ingot. The silver alloy comprises no noble metal and rare metal; has simple composition and low cost. The alloy can form a thin and dense intercalation oxide CoNiO on surface in atmosphere, has high tarnish resistance and can maintain the gloss of silver. The alloy has a hardness similar to that of sterling silver usually used at present and good machinability, and adapts to jewellry industry. The process of electric plating to the alloy is unnecessary.

Description

technical field

[0001] The invention relates to the technical field of metal materials, in particular to an anti-tarnish silver alloy suitable for jewelry, decorations and the like and a preparation method thereof. Background technique

[0002] Silver is located between gold and copper in the periodic table of elements, and its chemical properties are stable. It is not easy to oxidize even if it is heated in the air. However, silver alloys are prone to discoloration. This seriously affects the appearance of the jewelry. The discoloration of silver alloys is mainly due to the fact that silver easily reacts with sulfur to form black silver sulfide. In addition, sulfate, chloride, oxide, organic carbon and carbonate on the surface of silver jewelry. Both affect the apparent quality of silver alloys. In short, the discoloration of silver is a common phenomenon, and the exposure of corrosive media and water, sulfur and sulfide, oxygen, and light will cause and aggravate the ...

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