Iron and Steel

It is common today to talk about "the iron and steel industry" as if it were a single entity, but historically iron and steel were separate products. The steel industry is often considered to be an indicator of economic progress, because of the critical role played by steel in infrastructural and overall economic development. The economic boom in China and India has caused a massive increase in the demand for steel in recent years. Between 2000 and 2005, world steel demand increased by 6%. In 2008, steel started to be traded as a commodity in the London Metal Exchange. At the end of 2008, the steel industry faced a sharp downturn that led to many cut-backs. Iron is a chemical element. It is a strong, hard, heavy gray metal. It is found in meteorites. Iron is also found combined in many mineral compounds in the earth's crust. Iron rusts easily and can be magnetized and is strongly attracted to magnets. It is used to make many things such as gates and railings. Iron is also used to make steel, an even harder and tougher metal compound. Steel is formed by treating molten (melted) iron with intense heat and mixing it (alloying) with carbon. Steel is used to make machines, cars, tools, knives, and many other things.

Harder - The exact date at which people first discovered how to smelt iron ore and produce usable metal is not known. Archaeologists have found early iron tools that were used in Egypt from about 3000 bc. Iron objects of ornamentation were used even earlier. By about 1000 BC, the ancient Greeks are known to have used heat treatment techniques to harden their iron weaponry. These historical iron alloys, all iron alloys produced until about the fourteenth century ad, were forms of wrought iron.

Wrought iron was made by first heating a mass of iron ore and charcoal in a forge or furnace using a forced draft of air. This generated enough heat to reduce the iron ore to a hot, glowing, spongy mass of metallic iron filled with slag materials. The slag contained metallic impurities and charcoal ash. This iron sponge was then removed from the furnace and while still glowing hot, it was pounded with heavy sledges to separate the slag impurities and to weld and form the purer mass of iron. The iron produced in this way almost always contained slag particles and other impurities, but occasionally this technique of small batch iron making yielded a true steel product rather than wrought iron. These early iron makers also learned to make steel by reheating wrought iron and charcoal in clay boxes for several days, until the iron absorbed enough carbon to become a true hardened steel.

By the end of the fourteenth century, iron furnaces used in smelting were becoming larger with increased draft from large bellows being used to force air through the “charge” (mixture of raw materials). These larger furnaces first freed the molten iron in its upper levels. This metallic iron then combined with higher amounts of carbon because of the heated combustion blast produced by the air forced up through the furnace. The product of these furnaces was pig iron, an alloy that melts at a lower temperature than steel or even wrought iron. Pig iron was then further processed to make steel.

Today, giant steel mills are essential for producing steel from iron ore. Steel making still uses blast furnaces that are merely refinements of the furnaces used by the old ironworkers. Improvements in the refinement of molten iron with blasts of air was accomplished by the 1855 Bessemer converter. Since the 1960s, electric arc furnaces have also been producing steel from scrap metal.

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but is also less ductile.

Alloys with a higher carbon content are known as cast iron because of their lower melting point and castability. Steel is also distinguished from wrought iron, which can contain a small amount of carbon, but it is included in the form of slag inclusions. Two distinguishing factors are steel's increased rust resistance and better weldability.

Though steel had been produced by various inefficient methods long before the Renaissance, its use became more common after more efficient production methods were devised in the 17th century. With the invention of the Bessemer process in the mid-19th century, steel became an inexpensive mass-produced material. Further refinements in the process, such as basic oxygen steelmaking, further lowered the cost of production while increasing the quality of the metal. Today, steel is one of the most common materials in the world, with more than 1300 million tons produced annually. It is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades of steel defined by various standards organizations.

Iron, like most metals, is found in the Earth's crust only in the form of an ore, ie. combined with other elements such as oxygen or sulfur. Typical iron-containing minerals include Fe2O3—the form of iron oxide found as the mineral hematite, and FeS2—pyrite (fool's gold). Iron is extracted from ore by removing oxygen and combining the ore with a preferred chemical partner such as carbon. This process, known as smelting, was first applied to metals with lower melting points, such as tin, which melts at approximately 250 °C (482 °F) and copper, which melts at approximately 1,000 °C (1,830 °F). In comparison, cast iron melts at approximately 1,370 °C (2,500 °F). All of these temperatures could be reached with ancient methods that have been used since the Bronze Age. Since the oxidation rate itself increases rapidly beyond 800 °C, it is important that smelting take place in a low-oxygen environment. Unlike copper and tin, liquid iron dissolves carbon quite readily. Smelting results in an alloy (pig iron) containing too much carbon to be called steel. The excess carbon and other impurities are removed in a subsequent step.

Other materials are often added to the iron/carbon mixture to produce steel with desired properties. Nickel and manganese in steel add to its tensile strength and make austenite more chemically stable, chromium increases hardness and melting temperature, and vanadium also increases hardness while reducing the effects of metal fatigue. To prevent corrosion, at least 11% chromium is added to steel so that a hard oxide forms on the metal surface; this is known as stainless steel. Tungsten interferes with the formation of cementite, allowing martensite to form with slower quench rates, resulting in high speed steel. On the other hand, sulfur, nitrogen, and phosphorus make steel more brittle, so these commonly found elements must be removed from the ore during processing.

Perhaps the most important polymorphic form is martensite, a metastable phase which is significantly stronger than other steel phases. When the steel is in an austenitic phase and then quenched it forms into martensite, because the atoms "freeze" in place when the cell structure changes from FCC to BCC. Depending on the carbon content the martensitic phase takes different forms.

JSW Steel

Forging ahead, JSW Steel Ltd. is one among the largest Indian Steel Companies in India today with capacity of 7.8MT. India's second largest steelmaker, JSW Steel Ltd. consists of the most modern, eco-friendly steel plants with the latest technologies for both upstream & downstream processes.

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Iron and steel in history

It is believed that iron in pre-historic times may have been obtained from fragments of meteorites and it remained a rare metal for many centuries. Even after man learned how to extract iron from its ores, the product probably was so relatively soft and unpredictable, that bronze continued to be preferred for tools and weapons. Eventually iron replaced the non-ferrous metal for these purposes when man learned how to master the difficult arts of smelting, forging, hardening and tempering iron.

Man's use of iron in antiquity is attested by references to the metal in fragmentary writing and inscriptions from the ancient civilizations of Babylon, Egypt, China, India, Greece and Rome. Archeological finds in Mesopotamia and Egypt are proof that iron, and later steel, have been in the service of mankind for almost 6000 years. In early times, iron was melted with the use of charcoal made from wood. Later coal was discovered as a great source of heat. Subsequently, it was converted into coke, which was found to be ideal for smelting of iron ore.

Iron kept its dominant position for around 200 or more years after the Saugus works, the first successful iron works in America, was founded in 1646. With the advance of the Industrial Revolution, iron formed the rails for the newly invented railroad trains. It was also used to armour the sides of the fighting ships. About the mid-19th century, the age of steel began with the invention of the Bessemer process (1856), which allowed steel to be made in large quantities and at reasonable cost.