There are many classifications of non-ferrous metals, about 80 kinds, which are roughly divided into five categories according to their specific gravity, price, reserves and distribution in the earth's crust, and sooner or later.

(1) Heavy non-ferrous metals; refers to non-ferrous metals with a specific gravity greater than 4.5. Includes copper, nickel, bismuth, lead, zinc, antimony, mercury, cadmium and antimony.

(2) Light non-ferrous metals; refers to non-ferrous metals with a specific gravity of less than 4.5. Includes aluminum, magnesium, calcium, potassium, strontium and barium.

(3) Precious metals; refers to non-ferrous metals that are less abundant in the earth's crust, difficult to mine and extract, stable to oxygen and other reagents, and more expensive than ordinary metals. Including gold and silver. And platinum group elements. Generally, the specific gravity is relatively large, and the melting point is higher at 916-3000 degrees. It has good chemical stability, excellent oxidation resistance and corrosion resistance.

(4) Semi-metal; generally refers to five elements of silicon, selenium, tellurium, arsenic and boron. Its physicochemical properties are between metal and non-metal. For example, arsenic is non-metallic, but it can transfer heat and conduct electricity.

(5) Rare metals; rare metals are not said to be scarce. They only mean that they are not widely distributed in the earth's crust, and mining and smelting are difficult. They are used late in the industry, so they are called rare metals. Rare metals include rare light metals, rare high melting point metals, rare dispersed metals, rare earth metals, and rare radioactive metals.

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