Ordinary pure copper is a copper with a mass fraction of not less than 99.7%, and oxygen-containing copper with very few impurities. The appearance is purple-red, so it is also known as red copper. Pure copper annealing refers to the pure copper heat treatment process, which refers to slowly heating pure copper to a certain temperature, maintaining it for a sufficient time, and then cooling at an appropriate rate. The purpose is to reduce the hardness and improve the machinability; eliminate residual stress, stabilize the size, reduce the tendency of deformation and cracks; refine the grain, adjust the structure, and eliminate the defects of the structure. To be precise, annealing is a heat treatment process for materials, including metallic materials and non-metallic materials.

Pure copper annealing purpose：

　　(1)Reduce hardness and improve machinability.

　　(2)Eliminate residual stress, stabilize dimensions, reduce deformation and crack tendency；

　　(3)Refine the crystal grains, adjust the structure, and eliminate the structure defects.

　　(4)Uniform material structure and composition, improve material performance or make preparation for subsequent heat treatment.

　　In production, the annealing process is widely used. According to the different purposes of annealing required by the workpiece, there are a variety of annealing process specifications, commonly used are complete annealing, spheroidizing annealing, and stress relief annealing.