Term: Steel
**Steel Composition and Properties**:
– Steel contains 0.02% to 2.14% carbon by weight.
– Alloy steel includes intentional alloying elements like manganese, nickel, and chromium.
– Steel has improved strength and fracture resistance compared to iron.
– Various elements like chromium and nickel are added to modify steel’s properties.
– Steel can be heat-treated to enhance its properties.
– Pure iron exists in BCC alpha iron structure at room temperature.
– Carbon can form cementite when it moves out of solution with iron.
– Different metallurgical structures form in steel based on carbon and iron concentrations.
– Steel density ranges between 7,750 and 8,050kg/m^3 or 7.75 and 8.05g/cm^3.
– Heat treating processes for steel include annealing, quenching, and tempering.
**Steel Production and Recycling**:
– Iron is commonly found in the Earth’s crust as an ore.
– Iron is extracted through smelting, where oxygen is removed.
– Impurities are removed from pig iron to produce steel.
– Steel production involves reducing carbon content in smelted iron.
– Various elements are added to steel to achieve desired properties.
– Steel is one of the most recycled materials globally.
– In the United States in 2008, over 82,000,000 metric tons of steel were recycled, with an overall rate of 83%.
– Recycled raw materials account for about 40% of the total steel produced.
– Steel production exceeds the amount that is scrapped.
– Steel’s recyclability contributes to its sustainability.
**Historical Evolution of Steel**:
– Steel production dates back to antiquity with bloomeries and crucibles.
– Steel was produced in Celtic Europe from 800BC and in Britain from 490-375BC.
– High-carbon steel was produced in the Netherlands from the 2nd-4th centuries AD.
– Evidence of early high carbon steel production in South Asia.
– Wootz steel known for its durability and global exportation.
– Introduction of Henry Bessemer’s steelmaking process in 1855.
– Development of the Gilchrist-Thomas process to remove phosphorus.
– Siemens-Martin process as a complement to the Bessemer process.
– Use of electric arc furnaces (EAF) for reprocessing scrap metal and pig iron into new steel.
– Bethlehem Steel in Pennsylvania was one of the world’s largest steel manufacturers before closing in 2003.
**Steel Industry and Global Impact**:
– The steel industry contributes 8% of global greenhouse gas emissions.
– Major steel producers include ArcelorMittal, Tata Steel, Baosteel Group.
– Increase in global steel demand due to economic growth in China and India.
– Steel is one of the most commonly manufactured materials worldwide.
– China is the top steel producer with one-third of the world share.
– Ranking of other major steel producers like Japan, Russia, and the United States.
– Significant carbon dioxide emissions associated with steel production.
– Downturn in the steel industry at the end of 2008.
– Global greenhouse gas emissions attributed to the steel industry in 2021.
**Types of Steel and Applications**:
– Stainless steel contains at least 11% chromium for corrosion resistance.
– Carbon steel makes up 90% of steel production.
– High strength low alloy steel provides additional strength at a modest price increase.
– Advanced High Strength Steel (AHSS) is a new variety meeting CAFE regulations.
– Stainless steels resist corrosion with added elements like chromium and vanadium.
– Tool steels are alloyed for maximum solution hardening.
– Steel is widely used in construction, infrastructure, appliances, and buildings.
– Major structures like stadiums and skyscrapers are supported by steel skeletons.
– Steel is used in car bodies, shipbuilding, aerospace, and white goods.
– Applications include reinforcing concrete, mining, and office furniture.
Steel is an alloy of iron and carbon with improved strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels, which are resistant to corrosion and oxidation, typically need an additional 11% chromium. Because of its high tensile strength and low cost, steel is used in buildings, infrastructure, tools, ships, trains, cars, bicycles, machines, electrical appliances, furniture, and weapons.
Iron is the base metal of steel. Depending on the temperature, it can take two crystalline forms (allotropic forms): body-centred cubic and face-centred cubic. The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties. In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile, or soft and easily formed. In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations.
The carbon in typical steel alloys may contribute up to 2.14% of its weight. Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in the final steel (either as solute elements, or as precipitated phases), impedes the movement of the dislocations that make pure iron ductile, and thus controls and enhances its qualities. These qualities include the hardness, quenching behaviour, need for annealing, tempering behaviour, yield strength, and tensile strength of the resulting steel. The increase in steel's strength compared to pure iron is possible only by reducing iron's ductility.
Steel was produced in bloomery furnaces for thousands of years, but its large-scale, industrial use began only after more efficient production methods were devised in the 17th century, with the introduction of the blast furnace and production of crucible steel. This was followed by the Bessemer process in England in the mid-19th century, and then by the open-hearth furnace. With the invention of the Bessemer process, a new era of mass-produced steel began. Mild steel replaced wrought iron. The German states saw major steel prowess over Europe in the 19th century, and the American steel production industry was manufactured in Pittsburgh, Bethlehem, Pennsylvania, and Cleveland until the late 20th century.
Further refinements in the process, such as basic oxygen steelmaking (BOS), largely replaced earlier methods by further lowering the cost of production and increasing the quality of the final product. Today, steel is one of the most commonly manufactured materials in the world, with more than 1.6 billion tons produced annually. Modern steel is generally identified by various grades defined by assorted standards organisations. The modern steel industry is one of the largest manufacturing industries in the world, but also one of the most energy and greenhouse gas emission intense industries, contributing 8% of global emissions. However, steel is also very reusable: it is one of the world's most-recycled materials, with a recycling rate of over 60% globally.