Definition of copper
Copper is a chemical element, its chemical symbol is Cu, its atomic number is 29, and it is a transition metal. The most common use of copper is to make wires. Usually, the wires used now are made of pure copper. This is because its electrical conductivity and thermal conductivity are second only to silver, but it is much cheaper than silver.
Common classification
Many people think that there is only one kind of copper. It is the only one. But there are actually other different types of copper. For example, alloy copper; brass is an alloy composed of copper and zinc; white copper is an alloy of copper and nickel; bronze is an alloy formed by copper and elements other than zinc and nickel, mainly tin bronze, aluminum bronze, etc.; red copper is copper with a high copper content, and the total content of other impurities is less than 1%.
Classification of copper processing materials: copper sulfate, copper chloride, copper rods, copper bars, copper ingots, copper plates, copper wires, copper alloys, crude copper, copper strips, copper oxide, copper foil, copper pipes, copper foil, copper mud, copper castings, electrolytic copper, and other copper alloy copper materials.
Copper materials are made of pure copper or copper alloy in various shapes, including rods, wires, plates, strips, bars, tubes, foils, etc. Copper materials are processed by rolling, extrusion and drawing. Plates and bars are hot-rolled and cold-rolled; strips and foils are cold-rolled; tubes and bars are divided into extruded products and drawn products; wires are all drawn products.
1 Pure copper
Pure copper is a rose-red metal, which turns purple after a copper oxide film is formed on the surface, so industrial pure copper is often called red copper or electrolytic copper. The density is 8~9g/cm?, and the melting point is 1083℃. Pure copper has good electrical conductivity and is widely used in the manufacture of wires, cables, brushes, etc.; it has good thermal conductivity and is often used to manufacture magnetic instruments and meters that must be protected from magnetic interference, such as compasses, aviation instruments, etc.; it has excellent plasticity and is easy to be hot-pressed and cold-forced, and can be made into copper tubes, copper rods, copper wires, copper bars, copper strips, copper plates, copper foils and other copper materials. There are two types of pure copper products: smelted products and processed products.
According to the composition, Chinese copper processing materials can be divided into four categories: ordinary copper (T1, T2, T3, T4), oxygen-free copper (TU1, TU2 and high-purity, vacuum oxygen-free copper), deoxidized copper (TUP, TUMn), and special copper with a small amount of alloy elements (arsenic copper, tellurium copper, silver copper).
The electrical and thermal conductivity of pure copper is second only to silver, and it is widely used to make conductive and thermal conductive equipment. Copper has good corrosion resistance in the atmosphere, seawater, certain non-oxidizing acids (hydrochloric acid, dilute sulfuric acid), alkalis, salt solutions and various organic acids (acetic acid, citric acid), and is used in the chemical industry. In addition, copper has good weldability and can be processed into various semi-finished and finished products through cold and hot plastic processing. In the 1970s, the output of copper exceeded the total output of other types of copper alloys.
Trace impurities in pure copper have a serious impact on the electrical and thermal conductivity of copper. Among them, titanium, phosphorus, iron, silicon, etc. significantly reduce the electrical conductivity, while cadmium, zinc, etc. have little effect. Oxygen, sulfur, selenium, tellurium, etc. have very low solid solubility in copper and can form brittle compounds with copper. They have little effect on conductivity, but can reduce processing plasticity. When ordinary copper is heated in a reducing atmosphere containing hydrogen or carbon monoxide, hydrogen or carbon monoxide easily reacts with cuprous oxide (Cu2O) at the grain boundary to produce high-pressure water vapor or carbon dioxide gas, which can cause copper to crack. This phenomenon is often called the "hydrogen disease" of copper. Oxygen is harmful to the weldability of copper. Bismuth or lead forms a low-melting-point eutectic with copper, making copper hot and brittle; and when brittle bismuth is distributed in the form of a thin film at the grain boundary, it makes copper cold and brittle. Phosphorus can significantly reduce the conductivity of copper, but it can increase the fluidity of copper liquid and improve weldability. Appropriate amounts of lead, tellurium, sulfur, etc. can improve machinability.
