Black annealed carbon steel wire is a type of steel wire that has undergone a specific heat treatment process called annealing. Annealing is a controlled heating and cooling process used to alter the physical and mechanical properties of metal, in this case, carbon steel wire. The term "black" in black annealed refers to the appearance of the wire after annealing, which typically has a dark or blackened surface.

The annealing process involves heating the carbon steel wire to a specific temperature and then allowing it to cool slowly. This process relieves internal stresses, improves ductility, and softens the wire, making it more malleable and easier to work with. The slow cooling during annealing also helps in achieving a uniform and fine-grained microstructure in the steel.

Black annealed carbon steel wire is often used in applications where flexibility and formability are important, such as in the manufacturing of wire mesh, baling wire, and other products that require pliability. The blackened appearance is a result of the formation of a thin layer of iron oxide on the surface during the annealing process.

This type of wire is distinct from galvanized steel wire, as it lacks the zinc coating provided by galvanization. While black annealed carbon steel wire does not have the corrosion resistance of galvanized wire, it is preferred in applications where the wire's physical properties and malleability are more critical than corrosion resistance.