A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. Concrete is the most widely used material in existence and is behind only water as the planet's most-consumed resource.
Steel is an alloy of iron and carbon with improved strength and fracture resistance compared to other forms of iron. Because of its high tensile strength and low cost, steel is one of the most commonly manufactured materials in the world. Steel is used in buildings, as concrete reinforcing rods, in bridges, infrastructure, tools, ships, trains, cars, bicycles, machines, electrical appliances, furniture, and weapons.
Stainless steel, also known as inox, corrosion-resistant steel (CRES), and rustless steel, is an alloy of iron that is resistant to rusting and corrosion. It contains iron with chromium and other elements such as molybdenum, carbon, nickel and nitrogen depending on its specific use and cost. Stainless steel's resistance to corrosion results from the 10.5%, or more, chromium content which forms a passive film that can protect the material and self-heal in the presence of oxygen.
Smelting is a process of applying heat and a chemical reducing agent to an ore to extract a desired base metal product. It is a form of extractive metallurgy that is used to obtain many metals such as iron, copper, silver, tin, lead and zinc. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal behind. The reducing agent is commonly a fossil-fuel source of carbon, such as carbon monoxide from incomplete combustion of coke—or, in earlier times, of charcoal. The oxygen in the ore binds to carbon at high temperatures, as the chemical potential energy of the bonds in carbon dioxide is lower than that of the bonds in the ore.
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials by chemical or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and preventing corrosion.
Heat treating is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve the desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching. Although the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.
Steelmaking is the process of producing steel from iron ore and/or scrap. In steelmaking, impurities such as nitrogen, silicon, phosphorus, sulfur, and excess carbon are removed from the sourced iron, and alloying elements such as manganese, nickel, chromium, carbon, and vanadium are added to produce different grades of steel.
The general term slag may be a by-product or co-product of smelting (pyrometallurgical) ores and recycled metals depending on the type of material being produced. Slag is mainly a mixture of metal oxides and silicon dioxide. Broadly, it can be classified as ferrous, ferroalloy or non-ferrous/base metals. Within these general categories, slags can be further categorized by their precursor and processing conditions. Slag generated from the EAF process can contain toxic metals, which can be hazardous to human and environmental health.
Basic oxygen steelmaking, also known as Linz-Donawitz steelmaking or the oxygen converter process, is a method of primary steelmaking in which carbon-rich molten pig iron is made into steel. Blowing oxygen through molten pig iron lowers the carbon content of the alloy and changes it into low-carbon steel. The process is known as basic because fluxes of calcium oxide or dolomite, which are chemical bases, are added to promote the removal of impurities and protect the lining of the converter.
Ferromanganese is an alloy of iron and manganese, with other elements such as silicon, carbon, sulfur, nitrogen and phosphorus. The primary use of ferromanganese is as a type of processed manganese source to add to different types of steel, such as stainless steel. Global production of low-carbon ferromanganese reached 1.5 megatons in 2010.
An open-hearth furnace or open hearth furnace is any of several kinds of industrial furnace in which excess carbon and other impurities are burnt out of pig iron to produce steel. Because steel is difficult to manufacture owing to its high melting point, normal fuels and furnaces were insufficient for mass production of steel, and the open-hearth type of furnace was one of several technologies developed in the nineteenth century to overcome this difficulty. Compared with the Bessemer process, which it displaced, its main advantages were that it did not expose the steel to excessive nitrogen, was easier to control, and permitted the melting and refining of large amounts of scrap iron and steel.
An electric arc furnace (EAF) is a furnace that heats material by means of an electric arc.
Shielding gases are inert or semi-inert gases that are commonly used in several welding processes, most notably gas metal arc welding and gas tungsten arc welding. Their purpose is to protect the weld area from oxygen, and water vapour. Depending on the materials being welded, these atmospheric gases can reduce the quality of the weld or make the welding more difficult. Other arc welding processes use alternative methods of protecting the weld from the atmosphere as well – shielded metal arc welding, for example, uses an electrode covered in a flux that produces carbon dioxide when consumed, a semi-inert gas that is an acceptable shielding gas for welding steel.
Decarburization is the process of decreasing carbon content, which is the opposite of carburization.
Electrometallurgy is a method in metallurgy that uses electrical energy to produce metals by electrolysis. It is usually the last stage in metal production and is therefore preceded by pyrometallurgical or hydrometallurgical operations. The electrolysis can be done on a molten metal oxide which is used for example to produce aluminium from aluminium oxide via the Hall-Hérault process. Electrolysis can be used as a final refining stage in pyrometallurgical metal production (electrorefining) and it is also used for reduction of a metal from an aqueous metal salt solution produced by hydrometallurgy (electrowinning).
Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. These processes are most commonly used on low-alloy steels. They are also used on titanium, aluminium and molybdenum.
Deoxidization is a method used in metallurgy to remove the rest of oxygen content from previously reduced iron ore during steel manufacturing. In contrast, antioxidants are used for stabilization, such as in the storage of food. Deoxidation is important in the steelmaking process as oxygen is often detrimental to the quality of steel produced. Deoxidization is mainly achieved by adding a separate chemical species to neutralize the effects of oxygen or by directly removing the oxygen.
Deoxidized steel is steel that has some or all of the oxygen removed from the melt during the steelmaking process. Liquid steels contain dissolved oxygen after their conversion from molten iron, but the solubility of oxygen in steel decreases with cooling. As steel cools, excess oxygen can cause blowholes or precipitate FeO. Therefore, several strategies have been developed for deoxidation. This may be accomplished by adding metallic deoxidizing agents to the melt either before or after it is tapped, or by vacuum treatment, in which carbon dissolved in the steel is the deoxidizer.
Cobalt extraction refers to the techniques used to extract cobalt from its ores and other compound ores. Several methods exist for the separation of cobalt from copper and nickel. They depend on the concentration of cobalt and the exact composition of the ore used.
The HIsarna ironmaking process is a direct reduced iron process for iron making in which iron ore is processed almost directly into liquid iron (pig iron). The process combines two process units, the Cyclone Converter Furnace (CCF) for ore melting and pre-reduction and a Smelting Reduction Vessel (SRV) where the final reduction stage to liquid iron takes place. The process does not require the manufacturing of iron ore agglomerates such as pellets and sinter, nor the production of coke, which are necessary for the blast furnace process. Without these steps, the HIsarna process is more energy-efficient and has a lower carbon footprint than traditional ironmaking processes. In 2018 Tata Steel announced it has demonstrated that more than 50% CO2 emission reduction is possible with HIsarna technology, without the need for carbon capture technology.
