Copper is a non-ferrous metal closely related to human beings. Pure copper is a soft metal. When the surface is just cut, it is red-orange with a metallic luster, and the single substance is purple-red. Good ductility, high thermal conductivity and electrical conductivity, so it is the most commonly used material in cables, electrical and electronic components, and is also widely used in electrical, light industry, machinery manufacturing, construction industry, defense industry and other fields. The consumption of metal materials is second only to aluminum. Copper is also a green metal. It is said to be a green metal mainly because it has a low melting point and is easy to remelt and resmelt, so recycling is quite cheap. In ancient times, it was mainly used for casting utensils, works of art and weapons. The more famous utensils and works of art such as Houmuwu Ding and Siyang Fangzun. Copper can form a wide variety of alloys.

Copper alloys have excellent mechanical properties and low resistivity, the most important of which are bronze and brass The important alloys of copper are as follows:

(1) Brass: Brass is an alloy of copper and zinc, named for its yellow color. Brass has good mechanical properties and wear resistance, and can be used to manufacture precision instruments, parts of ships, shell casings of guns, etc. Brass sounds good when knocked, so musical instruments such as gongs, cymbals, bells, and horns are all made of brass.

(2) Nautical brass: an alloy of copper, zinc, and tin, resistant to seawater erosion, and can be used to make ship parts and balancers.
(3) Bronze: The alloy of copper and tin is called bronze, named for its blue color. It was a common alloy in ancient times (such as China's Bronze Age). Bronze generally has good corrosion resistance, wear resistance, castability and excellent mechanical properties. Used in the manufacture of precision bearings, high pressure bearings, seawater corrosion-resistant mechanical parts on ships, and various plates, pipes, bars, etc. Bronze also has an anomalous property - "heat shrinks and expands with cold", which is used to cast statues and expands after cooling, which can make eyebrows clearer.
(4) Phosphor bronze: an alloy of copper, tin, and phosphorus, which is hard and can be used to make springs.
(5) Cupronickel: Cupronickel is an alloy of copper and nickel, its color is the same as that of silver, shiny silver, not easy to rust. Commonly used in the manufacture of coins, electrical appliances, instruments and decorations.
(6) 18K gold (rose gold): an alloy of 6/24 copper and 18/24 gold. Red-yellow, hard, can be used to make jewelry and decorations.