Steel production today makes use of ferrous steel scrap as well as traditional raw materials, such as iron ore, coal and limestone. There are two processes; basic oxygen furnaces (BOF) and electric arc furnaces (EAF) that account for nearly all steel production.
Ironmaking, the first step in making steel, involves the raw material inputs of iron ore, coke and limestone being melted in a blast furnace. The resulting molten iron will contain 4.0%-4.5% carbon and other impurities. In the BOF process, recycled ferrous scrap is added to the molten iron in a converter. At temperatures exceeding 1600 degrees Celsius, oxygen is blown through the metal to reduce the carbon content to between 0-1.5%.
In the EAF method, recycled ferrous scrap is fed through high-power electric arcs to melt the metal and convert it to high-quality steel.
In both processes there is secondary steelmaking that treats the molten steel of adding or removing certain elements and/or altering the temperature and production environment. Some of the following steps can be used depending on the type of steel required:
- Ladle furnace
- Ladle injection
- Sealed argon bubbling with oxygen blowing
Continuous casting of the molten metal into a cooled mold allows a thin steel shell to solidify. The shell strand is withdrawn using guided rolls, then it is fully cooled and solidified. The strand is cut depending on the application. The metal may be solidified into semi-finished goods such as steel slabs for flat products including plate and strip, blooms for beams, and billets for rod and wire.
With primary forming, the steel slabs are reheated and hot-rolled in a process that eliminates cast defects and achieves the required shape and surface quality. Hot-rolled products are divided into flat products, long products, seamless tubes and specialty products.
Secondary forming is accomplished through cold-rolling, which is done below the metal’s recrystallization point, where mechanical stress, not heat, affects change.
Role of Metal Service Centers
A metals service center acquires primary metals like carbon steel, aluminum, stainless steel, brass, copper, titanium and alloy steel from metals producers and importers. The role of a metal service center is to warehouse mill-dimension products and sell in less-than-mill loads and/or process mill-dimension products into customized sizes or shapes for an end user. Service centers stock various product forms such as plates, coils, sheets, pipes and tubes, rods, flat products, angle or round bars and beams. Capabilities can include slitting, leveling and tension leveling, shearing, saw cutting, plasma cutting, annealing, turning and polishing, pipe threading, roll-forming, coil coating, warehousing and repackaging to customer specifications. The metals service center may have stocking programs, Kanban programs and inventory management procedures.