There are strict requirements on the resistivity, so the chemical composition of the raw material must ensure that the resistivity of the finished wire is qualified. The surface treatment, drawing and heat treatment process of steel wire is similar to that of general-purpose low-carbon steel wire, but requires a thicker zinc layer, and some passivation treatment is required after galvanizing, that is, the galvanized steel wire is immersed in chromic acid and sulfuric acid. In the mixed solution of nitric acid and nitric acid, a passivation protective film with iridescent or light yellow, light green, light red and other mixed colors is formed on the surface of the zinc layer to further improve the corrosion resistance of the steel wire. The steel wire is annealed before galvanizing. The finished galvanized low carbon steel wire for armored cables with a tensile strength of 345 to 490 MPa also requires a thicker zinc layer, and some require passivation after galvanizing.
It is made of carbon structural steel and delivered in hard or soft state. The tensile strength of the hard steel wire is between 540 and 980 MPa; the tensile strength of the soft steel wire is between 440 and 785 MPa. The specific requirements are determined by the steel grade and the diameter of the steel wire. The cross-sections of steel wires are round, square and hexagonal. The surface state of the steel wire is divided into cold drawn and silver bright. The silver bright steel wire should have higher dimensional accuracy and surface quality, smooth and shiny surface, and no surface defects harmful to use. The diameter of the steel wire delivered in the coil state is generally below 1mm or 1mrr-.
