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Performance Characteristics and Uses of Industrial Pure Copper

The reserves of copper in the earth’s crust are relatively small, but copper and its alloys are the earliest metals used in human history. Historians once used copper utensils as a symbol to divide the development stage of human society-the Bronze Age. Copper and copper alloys used in modern industry mainly include industrial pure copper, brass and bronze, and copper-nickel alloys are rarely used.

Industrial pure copper (abbreviated as pure copper) is rose red, and the surface oxide film is purple, so it is also called red copper. Its purity wCu=99.5%~99. 9%, relative density of 8.96, melting point of 1083℃, and solid state Face-centered cubic lattice. Pure copper has excellent electrical and thermal conductivity second only to silver, and is an ideal electrical and thermal conductive material; pure copper is also a diamagnetic material, which is important for making magnetic instruments, positioners and other antimagnetic instruments that are not interfered by external magnetic fields. significance.

Pure copper has high chemical stability, and has good corrosion resistance in non-industrially polluted atmosphere, fresh water and other media. It can also be corrosion resistant in non-oxidizing acid solutions, while it is resistant to oxidizing acids (HNO3, concentrated H2SO4, etc.). ) Solution and various salt solutions (including sea water) are easily corroded.

Pure copper has excellent plasticity (δ=50%), good weldability, and can withstand various cold and hot forming (casting, welding, cutting, pressure processing), but the strength and hardness are not high (σb=200 in the annealed state) ~250MPa, the hardness is 40~50HBW), after the cold plastic deformation, there is obvious work hardening; with the increase of the degree of deformation, the strength can be increased to 400~500MPa. But the plasticity index δ also dropped sharply to 5%. Therefore, if you need to continue cold deformation, intermediate annealing (recrystallization annealing) must be used to restore plasticity.

The main impurities of pure copper are Pb, Bi, O, S, As, P, etc., which can reduce the conductivity and processability, especially Bi and Pb, which must be strictly controlled. Because Bi and Pb are almost insoluble in copper, they form a eutectic (Cu + Bi) with a melting point of 270°C and a eutectic (Cu + Pb) with a melting point of 326°C, respectively. During hot press processing and welding, the co-crystals on these grain boundaries The crystal melts and cracks along the grain boundary, resulting in “hot brittleness”; in addition, Bi itself is very brittle, and it also cracks along the grain boundary during cold press processing, resulting in “cold brittleness”. Oxygen can form CuO with copper, reducing the plasticity of copper and causing cold embrittlement; oxygen-containing copper heated in a reducing atmosphere will also cause “hydrogen embrittlement”.