Copper is a metal with a cubic crystalline structure, a property that allows copper wire to be bent into sharp curves while still holding its shape. Copper wire is useful because of its strength, but it is subject to structural dislocations after being bent multiple times. Over time, the wire will remain strong but become tougher to bend. The annealing process makes copper wire easier to bend once again.
In the annealing process, copper wire is heated. The metal has a high melting point, but annealing heats the wire to only halfway toward its melting point. Just enough heat is applied to reform the wire's physical structure into cubic crystals, as it was prior to being bent. This process is applied after the wire has been bent into the desired final shape.
Unbent copper is originally soft; bending and forming it hardens it over time. Copper has a melting point of about 1,984 F. In the annealing process, the copper is heated to roughly 1,300 to 1,450 F. Oxidation causes copper wire to degrade over time and after much annealing.
Annealing copper wire returns it to its initial physical structure -- before it was work-hardened. Work hardening occurs when physical stress, whether bending or forming, is applied to copper wire. Precipitation hardening can occur as a result of metals being combined, forming an alloy that is much stronger than a pure, unalloyed metal. Annealing is best used on pure copper wires.
Annealed copper wire is used for a variety of purposes, including electronic components, jewelry and to hold the shape of bonsai trees. A jeweler forms certain metal pieces into desired shapes. Electronic components require perfectly formed wire for efficient structures. Annealed copper wire is important to bonsai artists, who use it to shape the trees, which constantly grow and change shape.