What is the third kind of copper used in industry alongside hard-drawn and medium-drawn copper?

The third kind of copper used in industry, alongside hard-drawn and medium-drawn copper, is annealed copper. This type of copper undergoes a heat treatment process called annealing, which involves heating the metal to a certain temperature and then allowing it to cool slowly. This treatment enhances the ductility and softness of the copper, making it more workable for various applications.

Annealed copper is particularly useful in situations where flexibility and ease of shaping are essential, such as in electrical wiring and plumbing applications. The annealing process eliminates internal stresses and allows for greater deformation without risk of cracking, which is a critical performance characteristic for certain industrial uses.

In contrast, hard-drawn copper is known for its strength and rigidity, making it suitable for applications that require high tensile strength. Medium-drawn copper falls in between hard-drawn and annealed in terms of hardness and workability. The other choices do not accurately represent a recognized category of copper in industrial usage, reinforcing that annealed is indeed the correct option in this context.