What are annealed conductors?

When metal is cold worked or formed it becomes work hardened or strain hardened. Copper conductors go through a considerable amount of work hardening as the copper rod is drawn down through ever decreasing die sizes until the required conductor dimension is achieved. Copper in this state is known as hard drawn copper.

Hard drawn copper is difficult to work with and stranding and bunching of the finer wires in this state would be very difficult. By heat treating the copper at the correct temperatures the ductility can be restored to make the cable soft and flexible again. The heat treating process is known as annealing and the resulting metal is known as soft annealed copper. The degree of annealing is controlled by temperature and time, copper wire is used with different degrees of annealing depending on the application.

Hard drawn copper has significantly higher tensile strength than soft annealed copper and is used as overhead wire whereas the soft annealed copper is flexible and has somewhat improved conductivity over hard drawn copper conductor.  

Annealed copper - Tensile strength 300-400 ksi (kilopound per square inch). Conductivity 100.00 % IACS

Hard drawn copper - 500-700 ksi. Conductivity 97 % IACS

Copper wire has several important properties that make it a “natural” for electrical wiring. More than any other non-precious metal, it is the best conductor of electricity, packing more power into a given diameter of wire than any substitute material. Copper wire is also easier to bend. With copper wire, connections are easy and sure. And, because it has a high melting point, it can take surprisingly heavy overloads or current surges without damage or danger.