Carbon steel wire is made from one of two practices, Basic Oxygen Furnace (BOF) steelmaking or Electric Arc Furnace (EAF) steelmaking. In BOF steelmaking, iron ore is one of the ingredients utilized in what is called a blast furnace to generate “pig iron”, which in turn is transformed into steel by blowing oxygen into a vessel containing the pig iron, in this manner refining the pig iron. In EAF steelmaking, most or indeed all of the raw material is simply purchased scrap steel, which is remelted using electric energy passing between large electrodes immersed into the scrap / melt mix
In BOF steelmaking, you will find that the content of what are called residual elements (for example – copper, nickel, chromium, and molybdenum) are significantly lower than in EAF steelmaking. Furthermore, the variation of the content of these elements from one heat to the next is generally more consistent in the case of BOF steel. It is the lower level of these residual elements, as well as the consistency of their levels in the steel, that results in the wires made from BOF steel being a bit lower in tensile strength and having not much in the way of variation. Lower residual levels are also one of the factors (there can be others) that relate to formability of the wire. The lower residual BOF steel is viewed as more formable and softer than wire made from EAF steel.
EAF steel tends to have higher residual levels, which can vary from heat to heat, due to the presence of residuals in the scrap steel, both within the steel and in the form of foreign contaminants (i.e. stuff like copper wiring) that did not get 100% removed from the scrap steel. Furthermore, the most “noble” of elements (copper and tin) cannot be removed by the steel making process. So the steelmaker utilizing an EAF must do one of two things to keep his residual levels low, 1) dilute or in large part replace the charge to the furnace with something other than scrap steel (ex. pig iron) or 2)restrict the scrap being used to the highest quality (and cost).
Most mills use EAF steelmaking that uses up to 100% scrap with higher impurities, resulting in more tensile variation, harder and less formable wire.
At Western Steel & Wire, we stock primarily S. Korean BOF steelmaking wire as our customers prefer consistent tensile strength, softer and more formable wire. We spec out 18” – 20” core diameters to allow for easy handling and “clean and dry” wire so there is no residue or oil that comes off on your hands. To the best of our knowledge, Western Steel & Wire is the exclusive supplier for Black Annealed BOF wire and Galvanized BOF wire