The
Modern Steel Manufacturing Process, Steel production involves
removing carbon from iron, by Terrence Bell,
5/13/18.
Steel is the world's most popular construction material
because of its unique combination of durability, workability, and cost. It's an
iron alloy that contains between 0.2 and 2 percent carbon by weight.
According to the World Steel
Association, some of the largest steel producing countries are China, Japan,
US, and India. China accounts for roughly 50 percent of this production.
The world's largest steel producers
include ArcelorMittal, Hebei Steel Group, Baosteel, POSCO and Nippon Steel.
The Modern Steel Production Process - Methods for manufacturing steel have
evolved significantly since industrial production began in the late 19th
century. Modern methods, however, are still based on the same premise as the
original Bessemer Process, which uses oxygen to lower the carbon content in
iron.
Today, steel production makes use of
recycled materials as well as traditional raw materials, such as iron ore,
coal, and limestone. Two processes, basic oxygen steelmaking (BOS) and
electric arc furnaces (EAF), account for virtually all steel production.
Modern steelmaking can be broken down
into six steps:
Ironmaking, which is the first step,
involves the raw inputs of iron ore, coke, and lime being melted in a blast
furnace. The resulting molten iron, also referred to as hot metal, still
contains 4 to 4.5 percent carbon and other impurities that make it brittle.
Primary steelmaking has two primary
methods: BOS (Basic Oxygen Furnace) and the more modern EAF (Electric Arc
Furnace) methods. BOS methods add recycled scrap steel to the molten iron in a
converter.
At high temperatures, oxygen is blown
through the metal, which reduces the carbon content to between 0 and 1.5
percent. EAF methods, however, feed recycled steel scrap through use high-power
electric arcs (temperatures up to 1650 C) to melt the metal and convert it to
high-quality steel.
Secondary steelmaking involves treating
the molten steel produced from both BOS and EAF routes to adjust the steel
composition. This is done by adding or removing certain elements and/or
manipulating the temperature and production environment.
Depending on the types of steel
required, the following secondary steelmaking processes can be used: Stirring,
Ladle
furnace, Ladle injection, Degassing and CAS-OB (composition adjustment by
sealed argon bubbling with oxygen blowing)
Continuous casting sees the molten steel
cast into a cooled mold causing a thin steel shell to solidify. The shell
strand is withdrawn using guided rolls and fully cooled and solidified. The
strand is cut into desired lengths depending on application; slabs for flat products
(plate and strip), blooms for sections (beams), billets for long products
(wires), or thin strips.
In primary forming, the steel that is
cast is then formed into various shapes, often by hot rolling, 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.
Finally, it's time for manufacturing,
fabrication, and finishing. Secondary forming techniques give the steel its
final shape and properties. These techniques include: Shaping (cold rolling), Machining (drilling), Joining (welding),
Coating (galvanizing), Heat treatment (tempering) and Surface treatment
(carburizing)
Norb Leahy, Dunwoody
GA Tea Party Leader
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