Classification of non-ferrous metals
There are many classifications of non-ferrous metals, there are about 80 kinds, roughly divided into five categories according to their proportion, price, reserves and distribution in the earth’s crust, and the time when they are discovered and used by people.
(1) Heavy non-ferrous metals; refers to non-ferrous metals with a specific gravity greater than 4.5. Including copper, nickel, indium, lead, zinc, antimony, mercury, cadmium and bismuth.
(2) Light non-ferrous metals; refers to non-ferrous metals with a specific gravity less than 4.5. Including aluminum, magnesium, calcium, potassium, strontium and barium.
(3) Precious metals: refers to non-ferrous metals that are less in the earth’s crust, are difficult to mine and extract, are stable to oxygen and other reagents, and are more expensive than general metals. Including gold and silver. And platinum group elements. Generally, the specific gravity is large, and the melting point is 916-3000 degrees. It has good chemical stability, excellent oxidation resistance and corrosion resistance.
(4) Semi-metal; generally refers to the five elements of silicon, selenium, tellurium, arsenic and boron. Its physical and chemical properties are between metals and non-metals. For example, arsenic is a non-metal, but it can transfer heat and conduct electricity.
(5) Rare metals: Rare metals do not mean that they are scarce, but that they are not widely distributed in the earth’s crust, are difficult to mine and smelt, and are late in industrial application, so they are called rare metals. Rare metals include rare light metals, rare refractory metals, rare dispersed metals, rare earth metals, and rare radioactive metals.