Jewelry materials are generally divided into three categories: metal materials, non-metal materials and various synthetic materials such as synthetic glass, gum, plastic, etc. Here we focus on metal materials, including precious metal materials such as gold, silver, platinum, etc. for jewelry, non-precious metal materials such as copper, zinc, etc., and metal alloy material flux for jewelry welding.

1. Precious metal materials

Precious metal materials refer to the eight elements of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), oh (Os), iridium (Ir), ruthenium (Ru), and rhodium (Rh).

In the production of jewelry, the most commonly used precious metal materials are gold, silver and platinum and their alloys. Commonly used gold alloys are mainly 18K gold, 14K gold, 12K gold and 9K gold; commonly used silver is 925 silver; commonly used platinum is Platinum 900 (marked as Pt900), platinum 950 (marked as Pt950), and now platinum 990 (marked as Pt990) has begun to appear in the market. Among these precious metal materials, platinum has the most stable properties, which has become the pulse point for merchants to promote platinum jewelry in the current jewelry market. However, too pure platinum (such as Pt990) can easily lead to loose claws when setting diamonds and cause gemstones to fall off. Gold is a traditional jewelry material, and various K gold colors add brilliance to jewelry. Silver is a relatively cheap precious metal material for jewelry, but because the properties of silver are not as stable as gold and platinum, and the surface is easy to oxidize, it needs to be treated on the surface of silver jewelry, usually plated with metal rhodium. How to solve the firmness of the rhodium-plated layer is a difficult point in the process.

1.1 The precious metal element gold (Au)

Gold and its alloys are the most familiar precious metal materials in the jewelry market, and have long dominated the jewelry market. Its characteristics are as follows:

1. The specific gravity of gold is larger (19.3), the melting point is higher (1064), and the hardness is lower (2.5-3).

2. The chemical properties of gold are stable, not easy to be oxidized, insoluble in acid and alkali, but soluble in aqua regia (nitric acid: hydrochloric acid = 1:3) and cyanide. Can form gold amalgam (white) with mercury.

3. Gold has good ductility and is suitable for machining. In modern times, it has been able to produce 2.3um gold foil and 10um diameter gold wire.

4. Gold is golden yellow, stable and does not fade. In the jewelry industry, in order to increase its color, hardness and wear resistance, other filling elements (copper, silver, cobalt, palladium, etc.) are often added to make various K gold materials, which greatly enriches the types of gold jewelry. In general, the higher the gold content, the better the malleability and ductility of the gold material. The gold content of any 18K gold is 75%, adding 25% silver makes it green; adding 25% copper makes it light red; adding 12.5 silver and 12.5 copper makes it rose; adding 16.7 silver and 8.3 copper It becomes light yellow; adding 5% silver and 20% palladium, it becomes milky white…

5. Gold (whether pure gold or K gold) contains some trace elements, iron, bismuth, lead, tin, etc. can easily embrittle gold; silver, copper, nickel, aluminum, titanium can change the tone and properties of gold; zinc And cadmium has a duality on the properties of gold.

6. What is patching: patching is a term used for alloy preparation. For example, to melt 18K gold, 75% of the pure gold is needed, and the remaining 25% of the metal is made of copper, silver, palladium and other relatively cheap metal accessories. After heating and fusion, what is obtained is 18K gold. The 25% weight of the auxiliary alloy is called the fillet.