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 0.2-2% carbon by weight.
According to the World Steel Association, some of the largest steel-producing countries are China, India, Japan, and the U.S. China accounts for roughly 50% of this production. The world's largest steel producers include ArcelorMittal, ChinaBaowu Group, Nippon Steel Corporation, and HBIS Group.
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.
Ironmaking, the first step in making steel, involves the raw inputs of iron ore, co*ke, and lime being melted in a blast furnace. The resulting molten iron—also referred to as hot metal—still contains 4-4.5% carbon and other impurities that make it brittle.
Primary steelmaking has two methods: BOS (Basic Oxygen Furnace) and the more modern EAF (Electric Arc Furnace) methods. The BOS method adds 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 0-1.5%.
The EAF method, however, feeds recycled steel scrap through high-power electric arcs (with temperatures of up to 1,650 degrees Celsius) to melt the metal and convert it into 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
CAS-OB (composition adjustment by sealed argon bubbling with oxygen blowing)
Continuous casting sees the molten steel castinto a cooled mold, causing a thin steel shell to solidify. The shell strand is withdrawn using guided rolls, then it's fully cooled and solidified. Next, the strand is cut 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), which is done below the metal's recrystallization point, meaning mechanical stress—not heat—affects change
Today there are two major commercial processes for making steel, namely basic oxygen steelmaking, which has liquid pig-iron from the blast furnace and scrap steel as the main feed materials, and electric arc furnace
electric arc furnace
An electric arc furnace (EAF) is a furnace that heats material by means of an electric arc.
https://en.wikipedia.org › wiki › Electric_arc_furnace
(EAF) steelmaking, which uses scrap steel or direct reduced iron
direct reduced iron
Direct reduced iron (DRI), also called sponge iron, is produced from the direct reduction of iron ore (in the form of lumps, pellets, or fines) into iron by a reducing gas which either contains elemental carbon (produced from natural gas or coal) or hydrogen.
https://en.wikipedia.org › wiki › Direct_reduced_iron
The raw materials for steelmaking are mined and then transformed into steel using two different processes: the blast furnace/basic oxygen furnace route, and the electric arc furnace route. Both processes are being continually improved to meet the challenge of low-emission steelmaking.
Today, steel is produced through one of three methods: 1) an Integrated Blast Furnace (BF) and Basic Oxygen Furnace (BOF), 2) an Electric Arc Furnace (EAF), or 3) Direct Reduced Iron (DRI) with electric arc furnaces.
Primary steelmaking has two methods: BOS (Basic Oxygen Furnace) and the more modern EAF (Electric Arc Furnace) methods. Basic oxygen process (BOP), a steelmaking method in which pure oxygen is blown into a bath of molten blast-furnace iron and scrap.
Of the three major steelmaking processes—basic oxygen, open hearth, and electric arc—the first two, with few exceptions, use liquid blast-furnace iron and scrap as raw material and the latter uses a solid charge of scrap and DRI.
In most industries, the manufacturing process begins with the acquisition of raw materials – either natural resources or pre-processed materials. Once received, those raw materials are cut, shaped, refined, or blended with other materials to create a saleable item.
The Bessemer process was so fast (10–20 minutes for a heat) that it allowed little time for chemical analysis or adjustment of the alloying elements in the steel.
In the mid-1850s, Henry Bessemer invented the Bessemer process, a way to manufacture steel quickly and cheaply by blasting hot air through melted iron to quickly remove impurities. It took only 10 or 20 minutes to do, and it helped increase steel production. US mills had produced 77,000 tons of steel in 1870.
Low carbon: A carbon content of . 30% and under is considered low-carbon steel. This is the most common and the least expensive type of steel. Thanks to its elasticity under strain, manufacturers use low-carbon steel for wires, bolts and pipes.
Is there a way of making steel without using coal, apart from using carbon-neutral charcoal? Yes, Actually DRI- Direct Reduced Iron- can be made without a blast furnace and without coal if you have a suitable iron ore and locally available cheap natural gas.
In order to produce high-quality steel, it is imperative that scrap metal is well sorted. It is also imperative that any coating is removed before entering the furnace as these coatings typically contain tramp metals, which cannot be removed by pyro-metallurgical processes in a high-temperature furnace.
Steel is stronger than iron in the domains of yield and tensile strength, but it's also significantly tougher. For applications across various industries, steel is obviously a superior material; it doesn't crack, warp, twist, rot, or split.
Basic oxygen steelmaking and continuous casting processes developed in the early 1950s are considered the most innovative technologies in the history of the steel industry. The two processes replaced the open hearth furnace and the slabbing and blooming process in integrated steel mills.
Its primary uses range from the infrastructure industry to product manufacturing of appliances, medical equipment, and even artworks like outdoor sculptures. There are various types of steel, but the most common ones are carbon steel, stainless steel, alloy steel, and tool steel.
In the basic oxygen process (BOP), molten iron from a blast furnace and iron scrap are refined in a furnace by lancing (or injecting) high-purity oxygen. The input material is typically 70 percent molten metal and 30 percent scrap metal. The oxygen reacts with carbon and other impurities to remove them from the metal.
The steel production process begins by smelting iron ore to produce metallic iron, which is then converted to steel by removing excess carbon and adding various alloys in a furnace. It is then constantly cast and rolled into a variety of shapes for different purposes and applications.
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