1.
Cast-iron cookware
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Cast iron cookware are valued for their heat retention properties, and can be produced and formed with a relatively low level of technology. Seasoning is used to protect bare cast iron from rust and to create a non-stick surface. Types of bare cast iron cookware include panini presses, waffle irons, crepe makers, dutch ovens, frying pans, deep fryers, tetsubin, woks, potjies, karahi, flattop grills, bare cast iron vessels have been used for cooking for over two thousand years. Cast iron cauldrons and cooking pots were valued as items for their durability and their ability to retain heat. In Europe, before the introduction of the stove in the middle of the 19th century, meals were cooked in the hearth or fireplace. This meant that all cooking vessels had to be designed to be suspended on, or in, Cast iron pots were made with handles to allow them to be hung over a fire, or with legs so that they could stand up in the fireplace. Cooking pots and pans with legless, flat bottoms were designed when cooking stoves became popular, Cast iron cookware was especially popular among homemakers and housekeepers during the first half of the 20th century. Most American households had at least one cast iron cooking pan, the Lodge Manufacturing company is currently the only major manufacturer of cast iron cookware in the United States, as most other cookware suppliers use pots and pans made in Asia or Europe. The 20th century also saw the introduction and popularization of enamel-coated cast iron cookware, Cast iron fell out of favor in the 1960s and 1970s, as teflon-coated aluminum non-stick cookware was introduced and quickly became the item of choice in many kitchens. Today, a selection of cookware can be purchased from kitchen suppliers. Because cast iron skillets can develop a non-stick surface, they are also a choice for egg dishes. Other uses of cast iron pans include baking, for instance for making cornbread, cobblers, most bare cast iron pots and pans are cast as a single piece of metal, including the handle. This allows them to be used on both the stovetop and in the oven, likewise, cast iron skillets can double as baking dishes. This differs from other cooking pots, which have varying components that may be damaged by the excessive temperatures of 400 °F or more. An American Dietetic Association study found that cast iron cookware can leach significant amounts of iron into food. The amounts of iron absorbed varied greatly depending on the food, its acidity, its content, how long it was cooked. The iron in spaghetti sauce increased 2,109 percent, while other foods increased less dramatically, for example, people with hemochromatosis should avoid using cast iron cookware because of the iron leaching effect into the food. A seasoned pan has a stick-resistant coating created by polymerized oils, seasoning is a process by which a layer of animal fat or vegetable oil is applied and cooked onto cast iron or carbon steel cookware
2.
Steel
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Steel is an alloy of iron and other elements, primarily carbon, that is widely used in construction and other applications because of its high tensile strength and low cost. Steels base metal is iron, which is able to take on two forms, body centered cubic and face centered cubic, depending on its temperature. It is the interaction of those allotropes with the elements, primarily carbon. In the body-centred cubic arrangement, there is an atom in the centre of each cube. Carbon, other elements, and inclusions within iron act as hardening agents that prevent the movement of dislocations that otherwise occur in the lattices of iron atoms. The carbon in steel alloys may contribute up to 2. 1% of its weight. Steels strength compared to pure iron is possible at the expense of irons ductility. With the invention of the Bessemer process in the mid-19th century and this was followed by Siemens-Martin process and then Gilchrist-Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron, further refinements in the process, such as basic oxygen steelmaking, largely replaced earlier methods by further lowering the cost of production and increasing the quality of the product. Today, steel is one of the most common materials in the world and it is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations, the noun steel originates from the Proto-Germanic adjective stakhlijan, which is related to stakhla. The carbon content of steel is between 0. 002% and 2. 1% by weight for plain iron–carbon alloys and these values vary depending on alloying elements such as manganese, chromium, nickel, iron, tungsten, carbon and so on. Basically, steel is an alloy that does not undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction, too little carbon content leaves iron quite soft, ductile, and weak. Carbon contents higher than those of steel make an alloy, commonly called pig iron, while iron alloyed with carbon is called carbon steel, alloy steel is steel to which other alloying elements have been intentionally added to modify the characteristics of steel. Common alloying elements include, manganese, nickel, chromium, molybdenum, boron, titanium, vanadium, tungsten, cobalt, and niobium. Additional elements are important in steel, phosphorus, sulfur, silicon, and traces of oxygen, nitrogen, and copper. Alloys with a higher than 2. 1% carbon content, depending on other element content, cast iron is not malleable even when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties
3.
Allotropes of iron
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Iron represents perhaps the best-known example for allotropy in a metal. At atmospheric pressure, there are three forms of iron, alpha iron a. k. a. ferrite, gamma iron a. k. a. austenite. At very high pressure, a form exists, called epsilon iron hexaferrum. Some controversial experimental evidence exists for another form that is stable at very high pressures and temperatures. The phases of iron at atmospheric pressure are important because of the differences in solubility of carbon, the high-pressure phases of iron are important as models for the solid parts of planetary cores. The inner core of the Earth is generally assumed to consist essentially of a crystalline iron-nickel alloy with ε structure, the outer core surrounding the solid inner core is believed to be composed of liquid iron mixed with nickel and trace amounts of lighter elements. As molten iron cools down, it solidifies at 1,538 °C into its δ allotrope, δ-iron can dissolve as much as 0. 09% of carbon by mass at 1,493 °C. As the iron cools further to 1,394 °C its crystal structure changes to a face centered cubic crystalline structure, in this form it is called gamma iron or Austenite. γ-iron can dissolve considerably more carbon and this γ form of carbon saturation is exhibited in stainless steel. Beta ferrite and beta iron are obsolete terms for the form of ferrite. The primary phase of low-carbon or mild steel and most cast irons at room temperature is ferromagnetic ferrite, the A2 forms the low-temperature boundary of the beta iron field in the phase diagram in Figure 1. For this reason, the phase is not usually considered a distinct phase. At 912 °C the crystal structure again becomes BCC as α-iron is formed, the substance assumes a paramagnetic property. α-iron can dissolve only a small concentration of carbon, at 770 °C, the Curie point, the iron is a fairly soft metal and becomes ferromagnetic. As the iron passes through the Curie temperature there is no change in crystalline structure and this is the stable form of iron at room temperature. Antiferromagnetism in alloys of epsilon-Fe with Mn, Os and Ru has been observed. An alternate stable form, if it exists, may appear at pressures of at least 50 GPa and temperatures of at least 1,500 K, as of December 2011, recent and ongoing experiments are being conducted on high-pressure and Superdense carbon allotropes. Superdense carbon allotropes Allotropy Austenite Curie point Eutectic system Ferrite Tempering
4.
Austenite
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Austenite, also known as gamma-phase iron, is a metallic, non-magnetic allotrope of iron or a solid solution of iron, with an alloying element. In plain-carbon steel, austenite exists above the eutectoid temperature of 1000 K. The austenite allotrope exists at room temperature in stainless steel and it is named after Sir William Chandler Roberts-Austen. From 912 to 1,394 °C alpha iron undergoes a transition from body-centred cubic to the face-centred cubic configuration of gamma iron. This is similarly soft and ductile but can dissolve considerably more carbon and this gamma form of iron is exhibited by the most commonly used type of stainless steel for making hospital and food-service equipment. Austenitization means to heat the iron, iron-based metal, or steel to a temperature at which it changes crystal structure from ferrite to austenite, the more open structure of the austenite is then able to absorb carbon from the iron-carbides in carbon steel. An incomplete initial austenitization can leave undissolved carbides in the matrix, for some irons, iron-based metals, and steels, the presence of carbides may occur during the austenitization step. The term commonly used for this is two-phase austenitization, austempering is a hardening process that is used on iron-based metals to promote better mechanical properties. The metal is heated into the region of the iron-cementite phase diagram. The metal is annealed in this temperature range until the austenite turns to bainite or ausferrite, by changing the temperature for austenitization, the austempering process can yield different and desired microstructures. A higher austenitization temperature can produce a carbon content in austenite. The carbon content in austenite as a function of austempering time has been established, as austenite cools, the carbon diffuses out of the austenite and forms carbon rich iron-carbide and leaves behind carbon poor ferrite. Depending on alloy composition, a layering of ferrite and cementite, called pearlite and this is a very important case, as the carbon does not have time to diffuse due to the high cooling rate, which results in carbon being trapped and as a result forms hard martensite. Too high a rate of thick sections may cause the outer layers of the heat treated part to transform from austenite while the inner portion is still in its less dense austenite form. The difference in rates of the inner and outer portion of the part may cause cracks to develop in the outer portion. By alloying the steel with tungsten, the diffusion is slowed. Such a material is said to have its hardenability increased, tempering following quenching will transform some of the brittle martensite into tempered martensite. Heating white cast iron above 727 °C causes the formation of austenite in crystals of primary cementite and this austenisation of white iron occurs in primary cementite at the interphase boundary with ferrite
5.
Cementite
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Cementite, also known as iron carbide, is an intermetallic compound of iron and carbon, more precisely an intermediate transition metal carbide with the formula Fe3C. By weight, it is 6. 67% carbon and 93. 3% iron and it has an orthorhombic crystal structure. It is a hard, brittle material, normally classified as a ceramic in its pure form, therefore, in carbon steels and cast irons that are slowly cooled, a portion of the carbon is in the form of cementite. Cementite forms directly from the melt in the case of white cast iron, in carbon steel, cementite precipitates from austenite as austenite transforms to ferrite on slow cooling, or from martensite during tempering. An intimate mixture with ferrite, the product of austenite. Cementite changes from ferromagnetic to paramagnetic at its Curie temperature of approximately 480 K, a natural iron carbide occurs in iron meteorites and is called cohenite after the German mineralogist Emil Cohen, who first described it. The figure shows the behaviour at room temperature. There are other forms of iron carbides that have been identified in tempered steel. These include Epsilon carbide, hexagonal close-packed Fe2-3C, precipitates in plain-carbon steels of carbon content >0. 2%, non-stoichiometric ε-carbide dissolves above ~200 °C, where Hägg carbides and cementite begin to form. Hägg carbide, monoclinic Fe5C2, precipitates in hardened tool steels tempered at 200-300 °C, characterization of different iron carbides is not at all a trivial task, and often X-ray diffraction is complemented by Mössbauer spectroscopy. Foundations of Materials Science and Engineering, microstructure of Steels and Cast Irons. Ester Esna du Plessis The Crystal Structures of Iron Carbides, Ph. D, formation of Fe7C3 and Fe5C2 type metastable carbides during the crystallization of an amorphous Fe75C25 alloy
6.
Graphite
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Graphite, archaically referred to as plumbago, is a crystalline form of carbon, a semimetal, a native element mineral, and one of the allotropes of carbon. Graphite is the most stable form of carbon under standard conditions, therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds. Highly ordered pyrolytic graphite or more correctly highly oriented pyrolytic graphite refers to graphite with a spread between the graphite sheets of less than 1°. The name graphite fiber is sometimes used to refer to carbon fibers or carbon fiber-reinforced polymer. Graphite occurs in rocks as a result of the reduction of sedimentary carbon compounds during metamorphism. It also occurs in rocks and in meteorites. Minerals associated with graphite include quartz, calcite, micas and tourmaline, in meteorites it occurs with troilite and silicate minerals. Small graphitic crystals in meteoritic iron are called cliftonite, Graphite is not mined in the United States, but U. S. production of synthetic graphite in 2010 was 134 kt valued at $1.07 billion. Graphite has a layered, planar structure, the individual layers are called graphene. In each layer, the atoms are arranged in a honeycomb lattice with separation of 0.142 nm. Atoms in the plane are bonded covalently, with three of the four potential bonding sites satisfied. The fourth electron is free to migrate in the plane, making graphite electrically conductive, however, it does not conduct in a direction at right angles to the plane. Bonding between layers is via weak van der Waals bonds, which allows layers of graphite to be easily separated, the two known forms of graphite, alpha and beta, have very similar physical properties, except for that the graphene layers stack slightly differently. The alpha graphite may be flat or buckled. The alpha form can be converted to the form through mechanical treatment. The acoustic and thermal properties of graphite are highly anisotropic, since phonons propagate quickly along the tightly-bound planes, graphites high thermal stability and electrical and thermal conductivity facilitate its widespread use as electrodes and refractories in high temperature material processing applications. However, in oxygen containing atmospheres graphite readily oxidizes to form CO2 at temperatures of 700 °C, Graphite is an electric conductor, consequently, useful in such applications as arc lamp electrodes. It can conduct electricity due to the vast electron delocalization within the carbon layers and these valence electrons are free to move, so are able to conduct electricity
7.
Martensite
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It includes a class of hard minerals occurring as lath- or plate-shaped crystal grains. When viewed in section, the lenticular crystal grains may be incorrectly described as acicular. Austenite is γ-Fe, a solution of iron and alloying elements. As a result of the quenching, the cubic austenite transforms to a highly strained body-centered tetragonal form called martensite that is supersaturated with carbon. The shear deformations that result produce a number of dislocations. The highest hardness of a steel is 400 Brinell whereas martensite can achieve 700 Brinell. The martensitic reaction begins during cooling when the austenite reaches the start temperature. For a eutectoid steel, between 6 and 10% of austenite, called retained austenite, will remain. The percentage of retained austenite increases from insignificant for less than 0. 6% C steel, to 13% retained austenite at 0. 95% C, a very rapid quench is essential to create martensite. For steel 0-0. 6% carbon the martensite has the appearance of lath, for steel greater than 1% carbon it will form a plate like structure called plate martensite. Between those two percentages, the appearance of the grains is a mix of the two. The strength of the martensite is reduced as the amount of retained austenite grows, the process produces dislocation densities up to 1013/cm2. The great number of dislocations, combined with precipitates that originate and pin the dislocations in place, thus, martensite can be thermally induced or stress induced. One of the differences between the two phases is that martensite has a tetragonal crystal structure, whereas austenite has a face-centered cubic structure. Martensite has a lower density than austenite, so that the martensitic transformation results in a change of volume. Of considerably greater importance than the change is the shear strain which has a magnitude of about 0.26. Martensite is not shown in the phase diagram of the iron-carbon system because it is not an equilibrium phase. Equilibrium phases form by slow cooling rates that allow sufficient time for diffusion, since chemical processes accelerate at higher temperature, martensite is easily destroyed by the application of heat
8.
Microstructure
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Microstructure is the small scale structure of a material, defined as the structure of a prepared surface of material as revealed by a microscope above 25× magnification. The microstructure of a material can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance and these properties in turn govern the application of these materials in industrial practice. Microstructure at scales smaller than can be viewed with optical microscopes is often called nanostructure, the nanostructure of biological specimens is referred to as ultrastructure. A microstructure’s influence on the mechanical and physical properties of a material is governed by the different defects present or absent of the structure. These defects can take many forms but the ones are the pores. Even if those pores play an important role in the definition of the characteristics of a material. In fact, for materials, different phases can exist at the same time. These phases have different properties and if managed correctly, can prevent the fracture of the material, the concept of microstructure is observable in macrostructural features in commonplace objects. Galvanized steel, such as the casing of a lamp post or road divider, each polygon is a single crystal of zinc adhering to the surface of the steel beneath. Zinc and lead are two metals which form large crystals visible to the naked eye. The atoms in each grain are organized one of seven 3d stacking arrangements or crystal lattices. The direction of alignment of the matrices differ between adjacent crystals, leading to variance in the reflectivity of each presented face of the grains on the galvanized surface. The average grain size can be controlled by processing conditions and composition and this is to increase the strength of the material. To quantify microstructural features, both morphological and material property must be characterized, image processing is a robust technique for determination of morphological features such as volume fraction, inclusion morphology, void and crystal orientations. To acquire micrographs, optical as well as electron microscopy are commonly used, to determine material property, Nanoindentation is a robust technique for determination of properties in micron and submicron level for which conventional testing are not feasible. Conventional mechanical testing such as tensile testing or dynamic analysis can only return macroscopic properties without any indication of microstructural properties. However, nanoindentation can be used for determination of local properties of homogeneous as well as heterogeneous materials. When a polished flat sample reveals traces of its microstructure, it is normal to capture the image using macrophotography
9.
Carbon steel
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The term carbon steel may also be used in reference to steel which is not stainless steel, in this use carbon steel may include alloy steels. As the carbon percentage content rises, steel has the ability to become harder and stronger through heat treating, however, regardless of the heat treatment, a higher carbon content reduces weldability. In carbon steels, the carbon content lowers the melting point. Mild steel, also known as steel and Low carbon steel. It is now the most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications, mild steel contains approximately 0. 05–0. 25% carbon making it malleable and ductile. Mild steel has a low tensile strength, but it is cheap and easy to form. It is often used large quantities of steel are needed. The density of steel is approximately 7.85 g/cm3. Low-carbon steels suffer from yield-point runout where the material has two yield points, the first yield point is higher than the second and the yield drops dramatically after the upper yield point. If a low-carbon steel is only stressed to some point between the upper and lower yield point then the surface develop Lüder bands, low-carbon steels contain less carbon than other steels and are easier to cold-form, making them easier to handle. Carbon steels which can successfully undergo heat-treatment have a content in the range of 0. 30–1. 70% by weight. Trace impurities of other elements can have a significant effect on the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short, that is, brittle, low-alloy carbon steel, such as A36 grade, contains about 0. 05% sulfur and melts around 1, 426–1,538 °C. Manganese is often added to improve the hardenability of low-carbon steels and these additions turn the material into a low-alloy steel by some definitions, but AISIs definition of carbon steel allows up to 1. 65% manganese by weight. Carbon steel is broken down into four classes based on content,0.05 to 0. 25% carbon content. Balances ductility and strength and has good resistance, used for large parts, forging. Very strong, used for springs, swords, and high-strength wires, steels that can be tempered to great hardness. Used for special purposes like knives, axles or punches, most steels with more than 2. 5% carbon content are made using powder metallurgy
10.
Pearlite
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Pearlite is a two-phased, lamellar structure composed of alternating layers of ferrite and cementite that occurs in some steels and cast irons. During slow cooling of an alloy, pearlite forms by a eutectoid reaction as austenite cools below 727 °C. Pearlite is a microstructure occurring in many grades of steels. The eutectoid composition of austenite is approximately 0, likewise steels with higher carbon content will form cementite before reaching the eutectoid point. The proportion of ferrite and cementite forming above the point can be calculated from the iron/iron—carbide equilibrium phase diagram using the lever rule. Steels with pearlitic or near-pearlitic microstructure can be drawn into thin wires, such wires, often bundled into ropes, are commercially used as piano wires, ropes for suspension bridges, and as steel cord for tire reinforcement. High degrees of wire drawing leads to pearlitic wires with yield strengths of several gigapascals and it makes pearlite one of the strongest structural bulk materials on earth. Some hypereutectoid pearlitic steel wires, when cold wire drawn to true strains above 5, although pearlite is used in many engineering applications, the origin of its extreme strength is not well understood. Bainite is a structure with lamellae much smaller than the wavelength of visible light. It is prepared by rapid cooling. Unlike pearlite, whose formation involves the diffusion of all atoms, eutectoid steel can in principle be transformed completely into pearlite, hypoeutectoid steels can also be completely pearlitic if transformed at a temperature below the normal eutectoid. Pearlite can be hard and strong but is not particularly tough and it can be wear resistant because of a strong lamellar network of ferrite and cementite. Examples of applications include cutting tools, high strength wires, knives, chisels, comprehensive information on pearlite Introduction to Physical metallurgy by Sidney H. Avner, second edition, McGraw hill publications. Steels, Processing, Structure, and Performance, Chapter 15 High-Carbon Steels, Fully Pearlitic Microstructures and Applications by George Krauss,2005 Edition, ASM International
11.
Bainite
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Bainite is a plate-like microstructure that forms in steels at temperatures of 250–550 °C. First described by E. S. Davenport and Edgar Bain and this critical temperature is 1000K in plain carbon steels. Davenport and Bain originally described the microstructure as being similar in appearance to tempered martensite, a fine non-lamellar structure, bainite commonly consists of cementite and dislocation-rich ferrite. The high concentration of dislocations in the present in bainite makes this ferrite harder than it normally would be. The temperature range for transformation of austenite to bainite is between those for pearlite and martensite, when formed during continuous cooling, the cooling rate to form bainite is more rapid than that required to form pearlite, but less rapid than is required to form martensite. Most alloying elements will lower the temperature required for the rate of formation of bainite. The microstructures of martensite and bainite at first seem quite similar and this is a consequence of the two microstructures sharing many aspects of their transformation mechanisms. However, morphological differences do exist that require a TEM to see, under a light microscope, the microstructure of bainite appears darker than martensite due to its low reflectivity. Bainite is an intermediate of pearlite and martensite in terms of hardness, Bain and Davenport also noted the existence of two distinct forms, upper-range bainite which formed at higher temperatures and lower-range bainite which formed near the martensite start temperature. At 900 °C a typical low-carbon steel is composed entirely of austenite, in addition to the thermodynamic considerations indicated by the phase diagram, the phase transformations in steel are heavily influenced by the chemical kinetics. This leads to the complexity of steel microstructures which are influenced by the cooling rate. However, the transformation from austenite to pearlite is a time-dependent reconstructive reaction which requires the large movement of the iron and carbon atoms. As a consequence a rapidly cooled steel may reach a temperature where pearlite can no longer form despite the reaction being incomplete and the remaining austenite being thermodynamically unstable. This non-equilibrium phase can only form at low temperatures, where the force for the reaction is sufficient to overcome the considerable lattice strain imposed by the transformation. The transformation is essentially time-independent with the phase fraction depending only the degree of cooling below the martensite start temperature. Further, it occurs without the diffusion of either substitutional or interstitial atoms, Bainite occupies a region between these two process in a temperature range where iron self-diffusion is limited but there is insufficient driving force to form martensite. A further distinction is made between so-called lower-bainite, which forms at temperatures closer to the martensite start temperature, and upper-bainite which forms at higher temperatures. This distinction arises from the rates of carbon at the temperature at which the bainite is forming
12.
Ledeburite
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In iron and steel metallurgy, ledeburite is a mixture of 4. 3% carbon in iron and is a eutectic mixture of austenite and cementite. It is named after the metallurgist Karl Heinrich Adolf Ledebur and he was the first professor of metallurgy at the Bergakademie Freiberg. Ledeburite arises when the content is between 2. 06% and 6. 67%. The eutectic mixture of austenite and cementite is 4. 3% carbon, Fe3C, 2Fe, ledeburite-II is composed of cementite-I with recrystallized secondary cementite and of pearlite. The pearlite results from the decay of the austenite that comes from the ledeburite-I at 723 °C. During more rapid cooling, bainite can develop instead of pearlite, and with very rapid cooling martensite can develop
13.
Tempering (metallurgy)
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Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. The exact temperature determines the amount of hardness removed, and depends on both the composition of the alloy and on the desired properties in the finished product. For instance, very hard tools are often tempered at low temperatures, tempering is a heat treatment technique applied to ferrous alloys, such as steel or cast iron, to achieve greater toughness by decreasing the hardness of the alloy. The reduction in hardness is usually accompanied by an increase in ductility, tempering is usually performed after quenching, which is rapid cooling of the metal to put it in its hardest state. Tempering is accomplished by controlled heating of the quenched work-piece to a temperature below its critical temperature. Heating above this temperature is avoided, so as not to destroy the very-hard, quenched microstructure, precise control of time and temperature during the tempering process is crucial to achieve the desired balance of physical properties. Low tempering temperatures may only relieve the stresses, decreasing brittleness while maintaining a majority of the hardness. Higher tempering temperatures tend to produce a reduction in the hardness, sacrificing some yield strength. In carbon steels, tempering alters the size and distribution of carbides in the martensite, tempering is also performed on normalized steels and cast irons, to increase ductility, machinability, and impact strength. Tempering is an ancient heat-treating technique, the oldest known example of tempered martensite is a pick axe which was found in Galilee, dating from around 1200 to 1100 BC. The process was used throughout the ancient world, from Asia to Europe, tempering was often confused with quenching and, often, the term was used to describe both techniques. I shall employ the word tempering in the sense as softening. In metallurgy, one may encounter many terms that have specific meanings within the field. Terms such as hardness, impact resistance, toughness, and strength can carry many different connotations, some of the terms encountered, and their specific definitions are, Strength, also called rigidity, this is resistance to permanent deformation and tearing. Strength, in metallurgy, is still a vague term, so is usually divided into yield strength, tensile strength, shear strength. Toughness, Resistance to fracture, as measured by the Charpy test, toughness often increases as strength decreases, because a material that bends is less likely to break. Hardness, Hardness is often used to strength or rigidity but, in metallurgy. In conventional metal alloys, there is a relation between indentation hardness and tensile strength, which eases the measurement of the latter
14.
Crucible steel
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Crucible steel is a term that applies to steel made by two different methods in the modern era, although it has been produced in varying locales throughout history. It is made by melting iron and other materials in a crucible, Crucible steel was produced in South and Central Asia during the medieval era. The homogeneous crystal structure of this cast steel improved its strength, only recently it has become apparent that places in Central Asia like Merv in Turkmenistan and Akhsiket in Uzbekistan were important centres of production of crucible steel. The Central Asian finds are all from excavations and date from the 8th to 12th centuries AD, while crucible steel is more attributed to the Middle East in early times, there have been swords discovered in Europe, particularly in Scandinavia. The swords in question have the ambiguous name inlaid into it and these swords actually date to a 200-year period from the 9th century to the early 11th century. It is speculated by many that the process of making the blades originated in the Middle East, in the first centuries of the Islamic period, there appear some scientific studies on swords and steel. The best known of these are by Jabir ibn Hayyan 8th century, al-Kindi 9th century, Al-Biruni in the early 11th century, al-Tarsusi in the late 12th century, and Fakhr-i-Mudabbir 13th century. Any of these far more information about Indian and damascene steels than appears in the entire surviving literature of classical Greece. Indian/Sri Lankan crucible steel is commonly referred to as wootz, which is agreed to be an English corruption of the word ukko or hookoo. As yet the scale of excavations and surface surveys is too limited to link the literary accounts to archaeometallurgical evidence. The known sites of crucible steel production in south India, i. e. at Konasamudram and Gatihosahalli, date from at least the medieval period. One of the earliest known sites, which shows some promising evidence that may be linked to ferrous crucible processes in Kodumanal. The site is dated between the third century BC and the third century AD, by the seventeenth century the main centre of crucible steel production seems to have been in Hyderabad. The process was quite different from that recorded elsewhere. Wootz from Hyderabad or the Decanni process for making watered blades involved a co-fusion of two different kinds of iron, one was low in carbon and the other was a steel or cast iron. Wootz steel was exported and traded throughout ancient Europe, China, the Arab world, and became particularly famous in the Middle East. Recent archaeological investigations have suggested that Sri Lanka also supported innovative technologies for iron, the Sri Lankan system of crucible steel making was partially independent of the various Indian and Middle Eastern systems. Their method was something similar to the method of carburization of wrought iron, the earliest confirmed crucible steel site is located in the knuckles range in the northern area of the Central Highlands of Sri Lanka dated to 6th −10th centuries AD
15.
Spring steel
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Spring steel is a name given to a wide range of steels used widely in the manufacture of springs, prominently in automotive and industrial suspension applications. These steels are generally low-alloy, medium-carbon steel or high-carbon steel with a high yield strength. This allows objects made of spring steel to return to their original shape despite significant deflection or twisting, many grades of steel can be hardened and tempered to suit application as a spring, however, some steels exhibit more desirable characteristics for spring applications. Applications include piano wire such as ASTM A228, spring clamps, antennas, springs, and vehicle coil springs, leaf springs, and s-tines. Spring steel is commonly used in the manufacture of metal swords both historically and for stage combat due to its resistance to bending, snapping or shattering. Spring steel is one of the most popular used in the fabrication of lockpicks due to its pliability. Tubular spring steel is used in the gear of some small aircraft due to its ability to absorb the impact of landing. It is also used in the making of knives, especially for the Nepalese kukri. It is used in binder clips, martensite Bibliography Oberg, Erik, Franklin D. Jones, Holbrook L. Horton, Henry H. Ryffel. Christopher J. McCauley, Riccardo Heald, Muhammed Iqbal Hussain, eds
16.
Alloy steel
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Alloy steel is steel that is alloyed with a variety of elements in total amounts between 1. 0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups, low-alloy steels and high-alloy steels, the difference between the two is somewhat arbitrary, Smith and Hashemi define the difference at 4. 0%, while Degarmo, et al. define it at 8. 0%. Most commonly, the alloy steel refers to low-alloy steels. Strictly speaking, every steel is an alloy, but not all steels are called alloy steels, the simplest steels are iron alloyed with carbon. However, the alloy steel is the standard term referring to steels with other alloying elements added deliberately in addition to the carbon. Common alloyants include manganese, nickel, chromium, molybdenum, vanadium, silicon, less common alloyants include aluminum, cobalt, copper, cerium, niobium, titanium, tungsten, tin, zinc, lead, and zirconium. The following is a range of improved properties in alloy steels, strength, hardness, toughness, wear resistance, corrosion resistance, hardenability, to achieve some of these improved properties the metal may require heat treating. Some of these uses in exotic and highly-demanding applications, such as in the turbine blades of jet engines, in spacecraft. Because of the properties of iron, some steel alloys find important applications where their responses to magnetism are very important, including in electric motors. A few common low alloy steels are, D6AC 300M 256A Alloying elements are added to certain properties in the material. Manganese, silicon, or aluminum are added during the process to remove dissolved oxygen, sulfur. Manganese, silicon, nickel, and copper are added to increase strength by forming solid solutions in ferrite, chromium, vanadium, molybdenum, and tungsten increase strength by forming second-phase carbides. Nickel and copper improve corrosion resistance in small quantities, zirconium, cerium, and calcium increase toughness by controlling the shape of inclusions. Sulfur lead, bismuth, selenium, and tellurium increase machinability, the alloying elements tend to form either solid solutions or compounds or carbides. Nickel is very soluble in ferrite, therefore, it forms compounds, aluminium dissolves in the ferrite and forms the compounds Al2O3 and AlN. Silicon is also very soluble and usually forms the compound SiO2•MxOy, manganese mostly dissolves in ferrite forming the compounds MnS, MnO•SiO2, but will also form carbides in the form of 3C. Chromium forms partitions between the ferrite and carbide phases in steel, forming C, Cr7C3, and Cr23C6, the type of carbide that chromium forms depends on the amount of carbon and other types of alloying elements present. Tungsten and molybdenum form carbides if there is enough carbon and an absence of stronger carbide forming elements, they form the carbides W2C and Mo2C, vanadium, titanium, and niobium are strong carbide forming elements, forming vanadium carbide, titanium carbide, and niobium carbide, respectively
17.
Maraging steel
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Maraging steels are steels that are known for possessing superior strength and toughness without losing malleability, although they cannot hold a good cutting edge. Aging refers to the extended heat-treatment process and these steels are a special class of low-carbon ultra-high-strength steels that derive their strength not from carbon, but from precipitation of intermetallic compounds. The principal alloying element is 15 to 25 wt. % nickel, secondary alloying elements, which include cobalt, molybdenum, and titanium, are added to produce intermetallic precipitates. Original development was carried out on 20 and 25 wt. % nickel, 8–12 wt. % cobalt, 3–5 wt. % molybdenum, addition of chromium produces stainless grades resistant to corrosion. Alternative variants of Ni-reduced maraging steels are based on alloys of Fe and Mn plus minor additions of Al, Ni, the Mn has a similar effect as Ni, i. e. it stabilizes the austenite phase. Hence, depending on their Mn content, Fe-Mn maraging steels can be fully martensitic after quenching them from the high temperature austenite phase or they can contain retained austenite, the latter effect enables the design of maraging-TRIP steels where TRIP stands for Transformation-Induced-Plasticity. Due to the low carbon content maraging steels have good machinability, prior to aging, they may also be cold rolled to as much as 90% without cracking. Maraging steels offer good weldability, but must be aged afterward to restore the properties to the heat affected zone. When heat-treated the alloy has very little change, so it is often machined to its final dimensions. Due to the alloy content maraging steels have a high hardenability. Since ductile FeNi martensites are formed upon cooling, cracks are non-existent or negligible, the steels can be nitrided to increase case hardness, and polished to a fine surface finish. Non-stainless varieties of maraging steel are moderately corrosion-resistant, and resist stress corrosion, corrosion-resistance can be increased by cadmium plating or phosphating. There is also a family of cobalt-free maraging steels which are cheaper but not quite as strong, there has been Russian and Japanese research in Fe-Ni-Mn maraging alloys. The steel is first annealed at approximately 820 °C for 15–30 minutes for thin sections and for 1 hour per 25 mm thickness for heavy sections and this is followed by air cooling to room temperature to form a soft, heavily-dislocated iron-nickel lath martensite. Overaging leads to a reduction in stability of the primary, metastable, coherent precipitates, leading to their dissolution, further excessive heat-treatment brings about the decomposition of the martensite and reversion to austenite. Maraging steels strength and malleability in the stage allows it to be formed into thinner rocket and missile skins than other steels. Maraging steels have very stable properties, and, even after overaging due to excessive temperature and these alloys retain their properties at mildly elevated operating temperatures and have maximum service temperatures of over 400 °C. They are suitable for engine components, such as crankshafts and gears, and their uniform expansion and easy machinability before aging make maraging steel useful in high-wear components of assembly lines and dies
18.
Stainless steel
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In metallurgy, stainless steel, also known as inox steel or inox from French inoxydable, is a steel alloy with a minimum of 10. 5% chromium content by mass. Stainless steel is notable for its resistance, and it is widely used for food handling. Stainless steel does not readily corrode, rust or stain with water as ordinary steel does, however, it is not fully stain-proof in low-oxygen, high-salinity, or poor air-circulation environments. There are various grades and surface finishes of stainless steel to suit the environment the alloy must endure, Stainless steel is used where both the properties of steel and corrosion resistance are required. Stainless steel differs from carbon steel by the amount of chromium present, unprotected carbon steel rusts readily when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by making it easier for more iron oxide to form, since iron oxide has lower density than steel, the film expands and tends to flake and fall away. In comparison, stainless steels contain sufficient chromium to undergo passivation and this layer prevents further corrosion by blocking oxygen diffusion to the steel surface and stops corrosion from spreading into the bulk of the metal. Passivation occurs only if the proportion of chromium is high enough, Stainless steel’s resistance to corrosion and staining, low maintenance, and familiar lustre make it an ideal material for many applications. Storage tanks and tankers used to transport orange juice and other food are made of stainless steel. This also influences its use in kitchens and food processing plants, as it can be steam-cleaned and sterilized. High oxidation resistance in air at ambient temperature is achieved with addition of a minimum of 13% chromium. The chromium forms a layer of chromium oxide when exposed to oxygen. The layer is too thin to be visible, and the metal remains lustrous, the layer is impervious to water and air, protecting the metal beneath, and this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, corrosion resistance can be adversely affected if the component is used in a non-oxygenated environment, a typical example being underwater keel bolts buried in timber. When stainless steel parts such as nuts and bolts are forced together, when forcibly disassembled, the welded material may be torn and pitted, a destructive effect known as galling. Galling can be avoided by the use of materials for the parts forced together, for example bronze and stainless steel. However, two different alloys electrically connected in a humid, even mildly acidic environment may act as a voltaic pile, nitronic alloys, made by selective alloying with manganese and nitrogen, may have a reduced tendency to gall. Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling, low-temperature carburizing is another option that virtually eliminates galling and allows the use of similar materials without the risk of corrosion and the need for lubrication
19.
Weathering steel
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U. S. Steel holds the registered trademark on the name COR-TEN. Although USS sold its discrete plate business to International Steel Group in 2003, it still sells COR-TEN branded material in strip-mill plate, the original COR-TEN received the standard designation A242 from the ASTM International standards group. Newer ASTM grades are A588 and A606 for thin sheet, all alloys are in common production and use. Weathering refers to the composition of these steels, allowing them to exhibit increased resistance to atmospheric corrosion compared to other steels. This is because the forms a protective layer on its surface under the influence of the weather. The corrosion-retarding effect of the layer is produced by the particular distribution and concentration of alloying elements in it. The layer protecting the surface develops and regenerates continuously when subjected to the influence of the weather, in other words, the steel is allowed to rust in order to form the protective coating. The mechanical properties of weathering steels depend on which alloy and how thick the material is. The original A242 alloy has a strength of 50 kilopounds per square inch. It has yield strength of 46 ksi and ultimate strength of 67 ksi for medium weight rolled shapes and plates from 0. 75–1 inch thick. The thickest rolled sections and plates – from 1. 5–4 in thick have yield strength of 42 ksi, a 588 has a yield strength of at least 50 ksi, and ultimate tensile strength of 70 ksi for all rolled shapes and plate thicknesses up to 4 in thick. It is very used in marine transportation, in the construction of intermodal containers as well as visible sheet piling along recently widened sections of Londons M25 motorway. The first use of weathering steel for architectural applications was the John Deere World Headquarters in Moline, the building was designed by architect Eero Saarinen, and completed in 1964. The main buildings of Odense University, designed by Knud Holscher and Jørgen Vesterholt and built 1971–1976, are clad in weathering steel, earning them the nickname Rustenborg. In 1977, Robert Indiana created a Hebrew version of the Love sculpture made from weathering steel using the four-letter word ahava for the Israel Museum Art Garden in Jerusalem, in Denmark, all masts for supporting the catenary on electrified railways are made of weathering steel for aesthetic reasons. Weathering steel was used in 1971 for the Highliner electric cars built by the St. Louis Car Company for Illinois Central Railroad, the use of weathering steel was seen as a cost-cutting move in comparison with the contemporary railcar standard of stainless steel. A subsequent order in 1979 was built to similar specs, including weathering steel bodies, the cars were painted, a standard practice for weathering steel railcars. The durability of weathering steel did not live up to expectations and these cars have been retired by 2016
20.
Tool steel
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Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion and deformation, as a result, tool steels are suited for their use in the shaping of other materials. With a carbon content between 0. 5% and 1. 5%, tool steels are manufactured under controlled conditions to produce the required quality. The presence of carbides in their plays the dominant role in the qualities of tool steel. The four major alloying elements in tool steel that form carbides are, tungsten, the rate of dissolution of the different carbides into the austenite form of the iron determines the high temperature performance of steel. Proper heat treatment of these steels is important for adequate performance, the manganese content is often kept low to minimize the possibility of cracking during water quenching. There are six groups of tool steels, water-hardening, cold-work, shock-resistant, high-speed, hot-work, the choice of group to select depends on cost, working temperature, required surface hardness, strength, shock resistance, and toughness requirements. The more severe the service condition, the higher the content and consequent amount of carbides required for the tool steel. Tool steels are used for cutting, pressing, extruding, and coining of metals, the AISI-SAE grades of tool steel is the most common scale used to identify various grades of tool steel. Individual alloys within a grade are given a number, for example, A2, O1, W-group tool steel gets its name from its defining property of having to be water quenched. W-grade steel is essentially high carbon plain-carbon steel and this group of tool steel is the most commonly used tool steel because of its low cost compared to others. They work well for parts and applications where high temperatures are not encountered. Its hardenability is low, so W-group tool steels must be subjected to a rapid quenching, requiring the use of water and these steels can attain high hardness and are rather brittle compared to other tool steels. W-steels are still sold, especially for springs, but are less widely used than they were in the 19th. This is partly because W-steels warp and crack much more during quench than oil-quenched or air hardening steels, the toughness of W-group tool steels are increased by alloying with manganese, silicon and molybdenum. Up to 0. 20% of vanadium is used to fine grain sizes during heat treating. 0. 76–0. 90% carbon, forging dies, hammers,0. 91–1. 10% carbon, general purpose tooling applications that require a good balance of wear resistance and toughness, such as rasps, drills, cutters, and shear blades. 1. 11–1. 30% carbon, files, small drills, lathe tools, razor blades, and other light-duty applications where more wear resistance is required without great toughness
21.
Cast iron
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Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. Its usefulness derives from its low melting temperature. Carbon ranging from 1. 8–4 wt%, and silicon 1–3 wt% are the main alloying elements of cast iron, Iron alloys with less carbon content are known as steel. While this technically makes the Fe–C–Si system ternary, the principle of cast iron solidification can be understood from the simpler binary iron–carbon phase diagram, cast iron tends to be brittle, except for malleable cast irons. It is resistant to destruction and weakening by oxidation, the earliest cast iron artefacts date to the 5th century BC, and were discovered by archaeologists in what is now Jiangsu in China. Cast iron was used in ancient China for warfare, agriculture, during the 15th century, cast iron became utilized for artillery in Burgundy, France, and in England during the Reformation. The first cast iron bridge was built during the 1770s by Abraham Darby III, cast iron is also used in the construction of buildings. Cast iron is made by re-melting pig iron, often along with quantities of iron, steel, limestone, carbon. Phosphorus and sulfur may be burnt out of the iron, but this also burns out the carbon. Depending on the application, carbon and silicon content are adjusted to the desired levels, other elements are then added to the melt before the final form is produced by casting. Cast iron is melted in a special type of blast furnace known as a cupola. After melting is complete, the molten cast iron is poured into a furnace or ladle. Cast irons properties are changed by adding various alloying elements, or alloyants, next to carbon, silicon is the most important alloyant because it forces carbon out of solution. A low percentage of silicon allows carbon to remain in solution forming iron carbide, a high percentage of silicon forces carbon out of solution forming graphite and the production of grey cast iron. Other alloying agents, manganese, chromium, molybdenum, titanium and vanadium counteracts silicon, promotes the retention of carbon, nickel and copper increase strength, and machinability, but do not change the amount of graphite formed. The carbon in the form of graphite results in an iron, reduces shrinkage, lowers strength. Sulfur, largely a contaminant when present, forms iron sulfide, the problem with sulfur is that it makes molten cast iron viscous, which causes defects. To counter the effects of sulfur, manganese is added because the two form into manganese sulfide instead of iron sulfide, the manganese sulfide is lighter than the melt so it tends to float out of the melt and into the slag
22.
Ductile iron
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While most varieties of cast iron are brittle, ductile iron has much more impact and fatigue resistance, due to its nodular graphite inclusions. On October 25,1949, Keith Dwight Millis, Albert Paul Gagnebin, Ductile iron is not a single material but part of a group of materials which can be produced with a wide range of properties through control of their microstructure. The common defining characteristic of this group of materials is the shape of the graphite, in ductile irons, graphite is in the form of nodules rather than flakes as in grey iron. Nodule formation is achieved by adding nodulizing elements, most commonly magnesium and, less often now, yttrium, often a component of mischmetal, has also been studied as a possible nodulizer. Austempered Ductile Iron was discovered in the 1950s but was commercialized and achieved only some years later. In ADI, the structure is manipulated through a sophisticated heat treating process. The aus portion of the name refers to austenite, improved corrosion resistance can be achieved by replacing 15% to 30% of the iron in the alloy with varying amounts of nickel, copper, or chromium. Much of the production of ductile iron is in the form of ductile iron pipe. Ductile iron is specifically useful in automotive components, where strength needs surpass that of aluminum. Other major industrial applications include off-highway diesel trucks, Class 8 trucks, agricultural tractors, in wind power industry nodular cast iron is used for hubs and structural parts like machine frames. Nodular cast iron is suitable for large and complex shapes and high loads, SG iron is used in many grand piano harps. Malleable iron Smith, William F. Hashemi, Javad, Foundations of Materials Science and Engineering, McGraw-Hill, media related to Ductile iron at Wikimedia Commons Ductile Iron Society Ductile Iron Pipe Research Association
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Malleable iron
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Malleable iron is cast as white iron, the structure being a metastable carbide in a pearlitic matrix. Through an annealing heat treatment, the structure as first cast is transformed into the malleable form. Carbon agglomerates into small roughly spherical aggregates of graphite leaving a matrix of ferrite or pearlite according to the heat treatment used. Three basic types of iron are recognized within the casting industry, blackheart malleable iron, whiteheart malleable iron. Malleable iron was used as early as the 4th century BCE, by the Tang Dynasty, the use of malleable iron in China waned, although there are malleable iron artifacts dating to the 9th century. Malleable iron is mentioned in England in a patent dating to the 1670s, réaumur conducted extensive research on malleable iron in 1720. He discovered that iron castings which were too hard to be worked could be softened by packing them into iron ore or hammer slag, creating malleable iron began in the United States in 1826 when Seth Boyden started a foundry for the production of harness hardware and other small castings. Like similar irons with the carbon formed into spherical or nodular shapes, incorrectly considered by some to be an old or dead material, malleable iron still has a legitimate place in the design engineers toolbox. Malleable iron is a choice for small castings or castings with thin cross sections. Other nodular irons produced with graphite in the shape can be difficult to produce in these applications. Malleable iron also exhibits better fracture toughness properties in low temperature environments than other nodular irons, the ductile to brittle behavior transformation temperature is lower than many other ductile iron alloys. Thicker sections of a casting will cool slowly, allowing some primary graphite to form and this graphite forms random flake-like structures and will not transform to carbide during heat treatment. When stress is applied to such a casting in application, the strength will be lower than expected for white iron. Such iron is said to have a mottled appearance, some countermeasures can be applied to enhance the formation of the all white structure, but malleable iron foundries often avoid producing heavy sections. After the casting and heat treatment processes, malleable iron can be shaped through cold working and this is possible due to malleable irons desirable property of being less strain rate sensitive than other materials. It is often used for small castings requiring good tensile strength, uses include electrical fittings, hand tools, pipe fittings, washers, brackets, fence fittings, power line hardware, farm equipment, mining hardware, and machine parts
24.
Wrought iron
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Wrought iron is an iron alloy with a very low carbon content in contrast to cast iron. It is a mass of iron with fibrous slag inclusions which gives it a grain resembling wood. Wrought iron is tough, malleable, ductile, corrosion-resistant and easily welded, before the development of effective methods of steelmaking and the availability of large quantities of steel, wrought iron was the most common form of malleable iron. A wrought product is one that has been worked by forging, extruding, rolling, hammering, etcetera, to change its form. Wrought iron is a worked iron product that is seldom produced today as other cheaper. Historically, a modest amount of iron was refined into steel. The demand for wrought iron reached its peak in the 1860s with the adaptation of ironclad warships, however, as properties such as brittleness of mild steel improved, it became less costly and more widely available than wrought iron, whose usage then declined. Wrought iron is no longer produced on a commercial scale, many products described as wrought iron, such as guard rails, garden furniture and gates, are actually made of mild steel. They retain that description because they are made to resemble objects which in the past were wrought by hand by a blacksmith, the word wrought is an archaic past participle of the verb to work, and so wrought iron literally means worked iron. Wrought iron is a term for the commodity, but is also used more specifically for finished iron goods. It was used in that sense in British Customs records. Cast iron, unlike wrought iron, is brittle and cannot be worked either hot or cold, Cast iron can break if struck with a hammer. In the 17th, 18th, and 19th centuries, wrought iron went by a variety of terms according to its form, origin. While the bloomery process produced wrought iron directly from ore, cast iron or pig iron were the materials used in the finery forge. Pig iron and cast iron have higher content than wrought iron. Cast and especially pig iron have excess slag which must be at least partially removed to produce quality wrought iron, at foundries it was common to blend scrap wrought iron with cast iron to improve the physical properties of castings. Fusion eventually became accepted as relatively more important than composition below a given low carbon concentration. Another difference is that steel can be hardened by heat treating, historically, wrought iron was known as commercially pure iron, however, it no longer qualifies because current standards for commercially pure iron require a carbon content of less than 0.008 wt%
25.
Iron
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Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements, ruthenium and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is also the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin, and transport in plasma. The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have also been studied extensively
26.
Carbon
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Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature. Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
27.
Alloy
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An alloy is a mixture of metals or a mixture of a metal and another element. Alloys are defined by a metallic bonding character, an alloy may be a solid solution of metal elements or a mixture of metallic phases. Intermetallic compounds are alloys with a stoichiometry and crystal structure. Zintl phases are sometimes considered alloys depending on bond types. Alloys are used in a variety of applications. In some cases, a combination of metals may reduce the overall cost of the material while preserving important properties, in other cases, the combination of metals imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength. Examples of alloys are steel, solder, brass, pewter, duralumin, bronze, the alloy constituents are usually measured by mass. Alloys are usually classified as substitutional or interstitial alloys, depending on the arrangement that forms the alloy. They can be classified as homogeneous, or heterogeneous or intermetallic. An alloy is a mixture of elements, which forms an impure substance that retains the characteristics of a metal. Alloys are made by mixing two or more elements, at least one of which is a metal and this is usually called the primary metal or the base metal, and the name of this metal may also be the name of the alloy. The other constituents may or may not be metals but, when mixed with the base, they will be soluble. The mechanical properties of alloys will often be different from those of its individual constituents. A metal that is very soft, such as aluminium, can be altered by alloying it with another soft metal. Although both metals are soft and ductile, the resulting aluminium alloy will have much greater strength. Adding a small amount of carbon to iron trades its great ductility for the greater strength of an alloy called steel. Due to its strength, but still substantial toughness, and its ability to be greatly altered by heat treatment, steel is one of the most useful. By adding chromium to steel, its resistance to corrosion can be enhanced, creating stainless steel, while adding silicon will alter its electrical characteristics, producing silicon steel
28.
Carbide
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In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be classified by chemical bonding type as follows, salt-like, covalent compounds, interstitial compounds. Examples include calcium carbide, silicon carbide, tungsten carbide, and cementite, the naming of ionic carbides is not systematic. Salt-like carbides are composed of highly electropositive elements such as the metals, alkaline earth metals, and group 3 metals, including scandium, yttrium. Aluminium from group 13 forms carbides, but gallium, indium and these materials feature isolated carbon centers, often described as C4−, in the methanides or methides, two-atom units, C22−, in the acetylides, and three-atom units, C34−, in the sesquicarbides. The graphite intercalation compound KC8, prepared from vapour of potassium and graphite, carbides of this class decompose in water producing methane. Three such examples are aluminium carbide Al 4C3, magnesium carbide Mg 2C, transition metal carbides are not saline carbides but their reaction with water is very slow and is usually neglected. For example, depending on surface porosity, 5–30 atomic layers of titanium carbide are hydrolyzed, forming methane within 5 minutes at ambient conditions, several carbides are assumed to be salts of the acetylide anion C22–, which has a triple bond between the two carbon atoms. Alkali metals, alkaline metals, and lanthanoid metals form acetylides, e. g. sodium carbide Na2C2, calcium carbide CaC2. Lanthanides also form carbides with formula M2C3, metals from group 11 also tend to form acetylides, such as copper acetylide and silver acetylide. Carbides of the elements, which have stoichiometry MC2 and M2C3, are also described as salt-like derivatives of C22−. The C-C triple bond length ranges from 119.2 pm in CaC2, the bonding in LaC2 has been described in terms of LaIII with the extra electron delocalised into the antibonding orbital on C22−, explaining the metallic conduction. The polyatomic ion C34−, sometimes called sesquicarbide or allylenide, is found in Li4C3 and Mg2C3, the ion is linear and is isoelectronic with CO2. The C-C distance in Mg2C3 is 133.2 pm, Mg2C3 yields methylacetylene, CH3CCH, and propadiene, CH2CCH2, on hydrolysis, which was the first indication that it contains C34−. The carbides of silicon and boron are described as covalent carbides, silicon carbide has two similar crystalline forms, which are both related to the diamond structure. Boron carbide, B4C, on the hand, has an unusual structure which includes icosahedral boron units linked by carbon atoms. In this respect boron carbide is similar to the boron rich borides, both silicon carbide and boron carbide are very hard materials and refractory. Boron also forms other covalent carbides, e. g. B25C, the carbides of the group 4,5 and 6 transition metals are often described as interstitial compounds
29.
Silicon
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Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a metallic luster. It is a member of group 14 in the table, along with carbon above it and germanium, tin, lead. It is not very reactive, although more reactive than germanium, Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earths crust. It is most widely distributed in dusts, sands, planetoids, over 90% of the Earths crust is composed of silicate minerals, making silicon the second most abundant element in the Earths crust after oxygen. Most silicon is used commercially without being separated, and often with little processing of the natural minerals, such use includes industrial construction with clays, silica sand, and stone. Silicate is used in Portland cement for mortar and stucco, and mixed with sand and gravel to make concrete for walkways, foundations. Silicates are used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass, Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics. Elemental silicon also has an impact on the modern world economy. Most free silicon is used in the refining, aluminium-casting. Silicon is the basis of the widely used synthetic polymers called silicones, Silicon is an essential element in biology, although only tiny traces are required by animals. However, various sea sponges and microorganisms, such as diatoms and radiolaria, silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa, horsetails and many grasses. Silicon is a solid at room temperature, with a point of 1,414 °C. Like water, it has a density in a liquid state than in a solid state and it expands when it freezes. With a relatively high conductivity of 149 W·m−1·K−1, silicon conducts heat well. In its crystalline form, pure silicon has a gray color, like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a cubic crystal structure with a lattice spacing of 0.5430710 nm. The outer electron orbital of silicon, like that of carbon, has four valence electrons, the 1s, 2s, 2p and 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six
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Ternary compound
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In chemistry, a ternary compound is a compound containing three different elements. An example of this is sodium phosphate, Na3PO4, the sodium ion has a charge of 1+ and the phosphate ion has a charge of 3-. Therefore, three sodium ions are needed to balance the charge of one phosphate ion, another example of a ternary compound is calcium carbonate. In naming and writing the formulae for ternary compounds, we follow rules that are similar to binary compounds, according to Rustum Roy and Olaf Müller, the chemistry of the entire mineral world informs us that chemical complexity can easily be accommodated within structural simplicity. The example of zircon is cited, where various metal atoms are replaced in the crystal structure. Remains ternary in character and is able to accommodate a range of chemical elements. It is an instance of natures simplexity. Letting A and B represent cations and X an anion, these groupings are organized by stoichiometric types A2BX4, ABX4. Brackets are used to identify a structure by an enclosed typical ternary compound, a ternary compound of type A2BX4 may be in the class of olivine, the spinel group, phenakite, or. One of type ABX4 may be of the class of zircon, in the ABX3 class of ternary compounds, there are the structures of perovskite, calcium carbonate, pyroxenes, corundum and hexagonal ABX2 types. Other ternary compounds are described as crystals of types A B X2, A2 B2 X7, A B X5, A2 B X6, A3 B X5
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Eutectic system
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It is only in this atomic/molecular ratio that the eutectic system melts as a whole, at a specific temperature the super-lattice releasing at once all its components into a liquid mixture. The eutectic temperature is the lowest possible melting temperature over all of the ratios for the involved component species. Conversely, as a non-eutectic mixture cools down, each component will solidify at a distinct temperature. The coordinates defining a eutectic point on a phase diagram are the percentage ratio. Not all binary alloys have eutectic points because the electrons of the component species are not always compatible, in any mixing ratio. The term eutectic was coined in 1884 by British physicist and chemist Frederick Guthrie, tangibly, this means the liquid and two solid solutions all coexist at the same time and are in chemical equilibrium. There is also a thermal arrest for the duration of the change of phase during which the temperature of the system does not change, the resulting solid macrostructure from a eutectic reaction depends on a few factors. The most important factor is how the two solid solutions nucleate and grow, the most common structure is a lamellar structure, but other possible structures include rodlike, globular, and acicular. Compositions of eutectic systems that are not at the composition can be classified as hypoeutectic or hypereutectic. As the temperature of a composition is lowered the liquid mixture will precipitate one component of the mixture before the other. In a hypereutectic solution, there will be a phase of species β whereas a hypoeutectic solution will have a proeutectic α phase. Eutectic alloys have two or more materials and have a eutectic composition, when a non-eutectic alloy solidifies, its components solidify at different temperatures, exhibiting a plastic melting range. Conversely, when a well-mixed, eutectic alloy melts, it does so at a single, some uses include, NEMA Eutectic Alloy Overload Relays for electrical protection of 3-phase motors for pumps, fans, conveyors, and other factory process equipment. The eutectic nature of salt and water is exploited when salt is spread on roads to aid snow removal, ethanol–water has an unusually biased eutectic point, i. e. it is close to pure ethanol, which sets the maximum proof obtainable by fractional freezing. Solar salt, 60% NaNO3 and 40% KNO3, forms a eutectic molten salt mixture which is used for energy storage in concentrated solar power plants. To reduce the melting point in the solar molten salts calcium nitrate is used in the following proportion, 42% Ca2, 43% KNO3. Lidocaine and prilocaine—both are solids at room temperature—form a eutectic that is an oil with a 16 °C melting point that is used in mixture of local anesthetic preparations. Menthol and camphor, both solids at room temperature, form a eutectic that is a liquid at room temperature in the proportions,8,2,7,3,6,4
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Brittleness
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A material is brittle if, when subjected to stress, it breaks without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength, breaking is often accompanied by a snapping sound. Brittle materials include most ceramics and glasses and some polymers, such as PMMA, many steels become brittle at low temperatures, depending on their composition and processing. When used in science, it is generally applied to materials that fail when there is little or no evidence of plastic deformation before failure. One proof is to match the broken halves, which should fit exactly since no plastic deformation has occurred, when a material has reached the limit of its strength, it usually has the option of either deformation or fracture. Improving material toughness is therefore a balancing act and this principle generalizes to other classes of material. Naturally brittle materials, such as glass, are not difficult to toughen effectively, the first principle is used in laminated glass where two sheets of glass are separated by an interlayer of polyvinyl butyral, which as a viscoelastic polymer absorbs the growing crack. The second method is used in toughened glass and pre-stressed concrete, a demonstration of glass toughening is provided by Prince Ruperts Drop. Brittle polymers can be toughened by using metal particles to initiate crazes when a sample is stressed, the least brittle structural ceramics are silicon carbide and transformation-toughened zirconia. A different philosophy is used in materials, where brittle glass fibres. When strained, cracks are formed at the interface, but so many are formed that much energy is absorbed. The same principle is used in creating metal matrix composites, generally, the brittle strength of a material can be increased by pressure. Supersonic fracture is crack motion faster than the speed of sound in a brittle material and this phenomenon was first discovered by scientists from the Max Planck Institute for Metals Research in Stuttgart and IBM Almaden Research Center in San Jose, California. Izod impact strength test Charpy impact test Fractography Forensic engineering Ductility Strengthening mechanisms of materials Lewis, Peter Rhys, Reynolds, K, Gagg, rösler, Joachim, Harders, Harald, Bäker, Martin. Mechanical behaviour of engineering materials, metals, ceramics, polymers, and composites
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Wear
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Wear is related to interactions between surfaces and specifically the removal and deformation of material on a surface as a result of mechanical action of the opposite surface. In materials science, wear is erosion or sideways displacement of material from its derivative, Wear of metals occurs by the plastic displacement of surface and near-surface material and by the detachment of particles that form wear debris. The size of the particles may vary from millimeter range down to an ion range. This process may occur by contact with metals, nonmetallic solids, flowing liquids. Secondary stage or mid-age process, where a rate of ageing is in motion. Most of the operational life is comprised in this stage. Tertiary stage or old-age period, where the components are subjected to rapid failure due to a rate of ageing. The secondary stage is shortened with increasing severity of conditions such as higher temperatures, strain rates, stress. Note that, wear rate is influenced by the operating conditions. Specifically, normal loads and sliding speeds play a role in determining wear rate. In addition, tribo-chemical reaction is important in order to understand the wear behavior. Different oxide layers are developed during the sliding motion, the layers are originated from complex interaction among surface, lubricants, and environmental molecules. In general, a plot, namely wear map. Demonstrating wear rate under different loading condition is used for operation and this graph also represents dominating wear modes under different loading conditions. Surface engineering and treatments are used to wear and extend the components working life. The study of the processes of wear is part of the discipline of tribology, the complex nature of wear has delayed its investigations and resulted in isolated studies towards specific wear mechanisms or processes. Impact-, cavitation-, diffusive- and corrosive- wear are all such examples and these wear mechanisms, however, do not necessarily act independently and wear mechanisms are not mutually exclusive. Industrial Wear are commonly described as incidence of multiple wear mechanisms occurring in unison, another way to describe Industrial Wear is to define clear distinctions in how different friction mechanisms operate, for example distinguish between mechanisms with high or low energy density
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Materials science
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The interdisciplinary field of materials science, also commonly termed materials science and engineering, involves the discovery and design of new materials, with an emphasis on solids. Materials science still incorporates elements of physics, chemistry, and engineering, as such, the field was long considered by academic institutions as a sub-field of these related fields. Materials science is a syncretic discipline hybridizing metallurgy, ceramics, solid-state physics and it is the first example of a new academic discipline emerging by fusion rather than fission. Many of the most pressing scientific problems humans currently face are due to the limits of the materials that are available, thus, breakthroughs in materials science are likely to affect the future of technology significantly. Materials scientists emphasize understanding how the history of a material influences its structure, the understanding of processing-structure-properties relationships is called the § materials paradigm. This paradigm is used to advance understanding in a variety of areas, including nanotechnology, biomaterials. Such investigations are key to understanding, for example, the causes of various accidents and incidents. The material of choice of a given era is often a defining point, phrases such as Stone Age, Bronze Age, Iron Age, and Steel Age are great examples. Originally deriving from the manufacture of ceramics and its putative derivative metallurgy, materials science is one of the oldest forms of engineering, modern materials science evolved directly from metallurgy, which itself evolved from mining and ceramics and the use of fire. Materials science has driven, and been driven by, the development of technologies such as rubbers, plastics, semiconductors. Before the 1960s, many materials science departments were named metallurgy departments, reflecting the 19th, a material is defined as a substance that is intended to be used for certain applications. There are a myriad of materials around us—they can be found in anything from buildings to spacecraft, Materials can generally be divided into two classes, crystalline and non-crystalline. The traditional examples of materials are metals, semiconductors, ceramics, New and advanced materials that are being developed include nanomaterials and biomaterials, etc. The basis of science involves studying the structure of materials. Once a materials scientist knows about this structure-property correlation, they can go on to study the relative performance of a material in a given application. The major determinants of the structure of a material and thus of its properties are its constituent chemical elements and these characteristics, taken together and related through the laws of thermodynamics and kinetics, govern a materials microstructure, and thus its properties. As mentioned above, structure is one of the most important components of the field of materials science, Materials science examines the structure of materials from the atomic scale, all the way up to the macro scale. Characterization is the way materials scientists examine the structure of a material, structure is studied at various levels, as detailed below
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Automotive industry
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The automotive industry is a wide range of companies and organizations involved in the design, development, manufacturing, marketing, and selling of motor vehicles, some of them are called automakers. It is one of the worlds most important economic sectors by revenue, the term automotive was created from Greek autos, and Latin motivus to represent any form of self-powered vehicle. This term was proposed by Elmer Sperry, the automotive industry began in the 1890s with hundreds of manufacturers that pioneered the horseless carriage. For many decades, the United States led the world in automobile production. In 1929, before the Great Depression, the world had 32,028,500 automobiles in use, at that time the U. S. had one car per 4.87 persons. After World War II, the U. S. produced about 75 percent of auto production. In 1980, the U. S. was overtaken by Japan, in 2006, Japan narrowly passed the U. S. in production and held this rank until 2009, when China took the top spot with 13.8 million units. With 19.3 million units manufactured in 2012, China almost doubled the U. S. production, with 10.3 million units, from 1970 over 1998 to 2012, the number of automobile models in the U. S. has grown exponentially. Safety is a state that implies to be protected from any risk, danger, in the automotive industry, safety means that users, operators or manufacturers do not face any risk or danger coming from the motor vehicle or its spare parts. Safety for the automobiles themselves, implies there is no risk of damage. Safety in the industry is particularly important and therefore highly regulated. Automobiles and other vehicles have to comply with a certain number of norms and regulations, whether local or international. The standard ISO26262, is considered as one of the best practice framework for achieving automotive functional safety. In case of safety issues, danger, product defect or faulty procedure during the manufacturing of the motor vehicle and this procedure is called product recall. Product recalls happen in every industry and can be production-related or stem from the raw material, however, the automotive industry is still particularly concerned about product recalls, which cause considerable financial consequences. Around the world, there were about 806 million cars and light trucks on the road in 2007, consuming over 980 billion litres of gasoline, the automobile is a primary mode of transportation for many developed economies. The Detroit branch of Boston Consulting Group predicts that, by 2014, meanwhile, in the developed countries, the automotive industry has slowed down. It is also expected that this trend will continue, especially as the generations of people no longer want to own a car anymore
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Cylinder head
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In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber and this joint is sealed by a head gasket. In most engines, the head also provides space for the passages that feed air and fuel to the cylinder, the head can also be a place to mount the valves, spark plugs, and fuel injectors. With a chain drive to a camshaft, the extra length of chain needed for an overhead cam design could give trouble from wear. Early sidevalve engines were in use at a time of simple fuel chemistry, low octane ratings and this made their combustion chamber design less critical and there was less need to design their ports and airflow carefully. One difficulty experienced at this time was that the low compression ratio also implied a low expansion ratio during the power stroke, exhaust gases were thus still hot, hotter than a contemporary engine, and this led to frequent trouble with burnt exhaust valves. A major improvement to the engine was the advent of Ricardos turbulent head design. This reduced the space within the chamber and the ports. Most importantly, it used turbulence within the chamber to thoroughly mix the fuel and this, of itself, allowed the use of higher compression ratios and more efficient engine operation. Despite common knowledge, the limit on performance is not the gas flow through the valves. With high speed engines and high compression, the limiting difficulty becomes that of achieving complete and efficient combustion, modern, efficient engines thus tend towards the pent roof or hemi designs, where the valves are brought close in to the centre of the space. Where fuel quality is low and octane rating is poor, compression ratios will be restricted, in these cases, the sidevalve engine still has much to offer. Such engines remained in production into the 1990s, only being replaced when the fuels available in the field became more likely to be diesel than petrol. In the overhead valve design, the head contains the poppet valves. In the overhead camshaft design, the head contains the valves, spark plugs and inlet/exhaust tracts just like the OHV engine. The number of heads in an engine is a function of the engine configuration. Almost all inline engines today use a cylinder head that serves all the cylinders. A V engine has two heads, one for each cylinder bank of the V
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Cylinder block
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A cylinder block is an integrated structure comprising the cylinder of a reciprocating engine and often some or all of their associated surrounding structures. The term engine block is used synonymously with cylinder block. In the basic terms of elements, the various main parts of an engine are conceptually distinct. However, it is no longer the way of building most petrol engines and diesel engines, because for any given engine configuration. These generally involve integrating multiple machine elements into one discrete part and this yields lower unit cost of production. Thus engine block, cylinder block, or simply block are the likely to be heard in the garage or on the street. This evolution has occurred throughout the history of reciprocating engines, with instances of every conceptual variation coexisting here and there. The increase in prevalence of ever-more-integrated designs relied on the development of foundry. For example, a practical low-cost V8 engine was not feasible until Ford developed the techniques used to build the Ford flathead V8 engine, which soon also disseminated to the larger society. Today the foundry and machining processes for manufacturing engines are highly automated. A cylinder block is a unit comprising several cylinders, in the earliest decades of internal combustion engine development, monobloc cylinder construction was rare, cylinders were usually cast individually. Combining their castings into pairs or triples was a win of monobloc design. A wet liner cylinder block features cylinder walls that are entirely removable and they are referred to as wet liners because their outer sides come in direct contact with the engines coolant. In other words, the liner is the wall, rather than being merely a sleeve. Wet liner designs are popular with European manufacturers, most notably Renault and Peugeot, dry liner designs use either the blocks material or a discrete liner inserted into the block to form the backbone of the cylinder wall. Additional sleeves are inserted within, which dry on their outside. It is likelier to be scrapped, with new equipment—engine or entire vehicle—replacing it, most early engines, particularly those with more than four cylinders, had their cylinders cast as pairs or triplets of cylinders, then bolted to a single crankcase. As casting techniques improved, a cylinder block of 4,6
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Gearbox
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A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term refers simply to the gearbox that uses gears and gear trains to provide speed. In British English, the term refers to the whole drivetrain, including clutch, gearbox, prop shaft, differential. In American English, however, the term more specifically to the gearbox alone. The most common use is in vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a high rotational speed, which is inappropriate for starting, stopping. The transmission reduces the engine speed to the slower wheel speed. Transmissions are also used on bicycles, fixed machines. Often, a transmission has multiple gear ratios with the ability to switch between them as speed varies and this switching may be done manually or automatically. Directional control may also be provided, single-ratio transmissions also exist, which simply change the speed and torque of motor output. The output of the transmission is transmitted via the driveshaft to one or more differentials, while a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds as it changes the direction of rotation. Conventional gear/belt transmissions are not the mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation, automatic transmissions use a valve body to shift gears using fluid pressures in conjunction with an ecm. Early transmissions included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, in support of pumping, milling, most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft. This means that the shaft of a gearbox rotates at a slower rate than the input shaft. A gearbox can be set up to do the opposite and provide an increase in speed with a reduction of torque. Some of the simplest gearboxes merely change the rotational direction of power transmission. Many typical automobile transmissions include the ability to select one of several gear ratios, in this case, most of the gear ratios are used to slow down the output speed of the engine and increase torque
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Redox
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Redox is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a process and a complementary oxidation process, two key concepts involved with electron transfer processes. Redox reactions include all chemical reactions in which atoms have their oxidation state changed, in general, the chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. It can be explained in terms, Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom. Reduction is the gain of electrons or a decrease in state by a molecule, atom. As an example, during the combustion of wood, oxygen from the air is reduced, the reaction can occur relatively slowly, as in the case of rust, or more quickly, as in the case of fire. Redox is a portmanteau of reduction and oxidation, the word oxidation originally implied reaction with oxygen to form an oxide, since dioxygen was historically the first recognized oxidizing agent. Later, the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions, ultimately, the meaning was generalized to include all processes involving loss of electrons. The word reduction originally referred to the loss in weight upon heating a metallic ore such as an oxide to extract the metal. In other words, ore was reduced to metal, antoine Lavoisier showed that this loss of weight was due to the loss of oxygen as a gas. Later, scientists realized that the atom gains electrons in this process. The meaning of reduction then became generalized to all processes involving gain of electrons. Even though reduction seems counter-intuitive when speaking of the gain of electrons, it help to think of reduction as the loss of oxygen. Since electrons are charged, it is also helpful to think of this as reduction in electrical charge. The electrochemist John Bockris has used the words electronation and deelectronation to describe reduction and oxidation processes respectively when they occur at electrodes and these words are analogous to protonation and deprotonation, but they have not been widely adopted by chemists. The term hydrogenation could be used instead of reduction, since hydrogen is the agent in a large number of reactions. But, unlike oxidation, which has been generalized beyond its root element, the word redox was first used in 1928. The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another, the oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction
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Archaeology
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Archaeology, or archeology, is the study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, Archaeology can be considered both a social science and a branch of the humanities. In North America, archaeology is considered a sub-field of anthropology, archaeologists study human prehistory and history, from the development of the first stone tools at Lomekwi in East Africa 3.3 million years ago up until recent decades. Archaeology as a field is distinct from the discipline of palaeontology, Archaeology is particularly important for learning about prehistoric societies, for whom there may be no written records to study. Prehistory includes over 99% of the human past, from the Paleolithic until the advent of literacy in societies across the world, Archaeology has various goals, which range from understanding culture history to reconstructing past lifeways to documenting and explaining changes in human societies through time. The discipline involves surveying, excavation and eventually analysis of data collected to learn more about the past, in broad scope, archaeology relies on cross-disciplinary research. Archaeology developed out of antiquarianism in Europe during the 19th century, Archaeology has been used by nation-states to create particular visions of the past. Nonetheless, today, archaeologists face many problems, such as dealing with pseudoarchaeology, the looting of artifacts, a lack of public interest, the science of archaeology grew out of the older multi-disciplinary study known as antiquarianism. Antiquarians studied history with attention to ancient artifacts and manuscripts. Tentative steps towards the systematization of archaeology as a science took place during the Enlightenment era in Europe in the 17th and 18th centuries, in Europe, philosophical interest in the remains of Greco-Roman civilization and the rediscovery of classical culture began in the late Middle Age. Antiquarians, including John Leland and William Camden, conducted surveys of the English countryside, one of the first sites to undergo archaeological excavation was Stonehenge and other megalithic monuments in England. John Aubrey was a pioneer archaeologist who recorded numerous megalithic and other monuments in southern England. He was also ahead of his time in the analysis of his findings and he attempted to chart the chronological stylistic evolution of handwriting, medieval architecture, costume, and shield-shapes. Excavations were also carried out in the ancient towns of Pompeii and Herculaneum and these excavations began in 1748 in Pompeii, while in Herculaneum they began in 1738. The discovery of entire towns, complete with utensils and even human shapes, however, prior to the development of modern techniques, excavations tended to be haphazard, the importance of concepts such as stratification and context were overlooked. The father of archaeological excavation was William Cunnington and he undertook excavations in Wiltshire from around 1798, funded by Sir Richard Colt Hoare. Cunnington made meticulous recordings of neolithic and Bronze Age barrows, one of the major achievements of 19th century archaeology was the development of stratigraphy. The idea of overlapping strata tracing back to successive periods was borrowed from the new geological and paleontological work of scholars like William Smith, James Hutton, the application of stratigraphy to archaeology first took place with the excavations of prehistorical and Bronze Age sites
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Jiangsu
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Jiangsu, formerly romanized as Kiangsu, is an eastern-central coastal province of the Peoples Republic of China. It is one of the provinces in manufacturing electronics and apparel items. Jiangsu is the third smallest, but the fifth most populous, Jiangsu has the second-highest GDP of Chinese provinces, after Guangdong. Jiangsu borders Shandong in the north, Anhui to the west, Jiangsu has a coastline of over 1,000 kilometres along the Yellow Sea, and the Yangtze River passes through the southern part of the province. Since the Sui and Tang dynasties, Jiangsu has been an economic and commercial center. Cities such as Yangzhou, Nanjing, Wuxi, Suzhou and Shanghai are all major Chinese economic hubs, since the initiation of economic reforms in 1990, Jiangsu has become a focal point for economic development. It is widely regarded as Chinas most developed province measured by its Human Development Index, Jiangsu is home to many of the worlds leading exporters of electronic equipment, chemicals and textiles. It has also been Chinas largest recipient of foreign investment since 2006. Its 2014 nominal GDP was more than 1 trillion US dollars and its name is a compound of the first elements of the names of the two cities of Jiangning and Suzhou. The abbreviation for this province is 苏, the character of its name. The state of Wu was subjugated in 473 BC by the state of Yue, Yue was in turn subjugated by the powerful state of Chu from the west in 333 BC. Eventually the state of Qin swept away all the other states, during the Three Kingdoms period, southern Jiangsu became the base of the Eastern Wu whose capital, Jiankang, is modern Nanjing. When nomadic invasions overran northern China in the 4th century, the court of the Jin Dynasty moved to Jiankang. Cities in southern and central Jiangsu swelled with the influx of migrants from the north, Jiankang remained as the capital for four successive Southern Dynasties and became the largest commercial and cultural center in China. The Tang Dynasty relied on southern Jiangsu for annual deliveries of grain and it was during the Song Dynasty, which saw the development of a wealthy mercantile class and emergent market economy in China, that south Jiangsu emerged as a center of trade. From then onwards, south Jiangsu, especially cities like Suzhou or Yangzhou, would be synonymous with opulence. Today south Jiangsu remains one of the richest parts of China, the Mongols took control of China in the thirteenth century. The Ming Dynasty, which was established in 1368 after driving out the Mongols who had occupied China, following a coup by Zhu Di, however, the capital was moved to Beijing, far to the north
42.
Burgundy
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Burgundy is a historical territory and a former administrative region of east-central France, entities that trace their name from the Burgundians, a Germanic people. Historically, Burgundy has referred to political entities, including kingdoms. The first known inhabitants of the area that became Burgundy were Celts, during the 4th century, the Burgundians, a Germanic people, who may have originated in Bornholm, settled in the western Alps. They founded the Kingdom of the Burgundians, which was conquered in the 6th century by another Germanic tribe, under Frankish dominion, the Kingdom of Burgundy continued for several centuries. Later, the region was divided between the Duchy of Burgundy and the Free County of Burgundy, burgundys modern existence is rooted in the dissolution of the Frankish Empire. In the 880s, there were four Burgundies, which were the Kingdom of Upper and Lower Burgundy, the duchy, during the Middle Ages, Burgundy was the seat of some of the most important Western churches and monasteries, among them Cluny, Cîteaux, and Vézelay. During the Hundred Years War, King John II of France gave the duchy to his youngest son, the duchy soon became a major rival to the crown. The court in Dijon outshone the French court both economically and culturally, in 1477, at the battle of Nancy during the Burgundian Wars, the last duke Charles the Bold was killed in battle, and the Duchy itself was annexed by France and became a province. However the northern part of the empire was taken by the Austrian Habsburgs, with the French Revolution in the end of the 18th century, the administrative units of the provinces disappeared, but were reconstituted as regions during the Fifth Republic in the 1970s. The modern-day administrative region comprises most of the former duchy, as of he region of Burgundy is both larger than the old Duchy of Burgundy and smaller than the area ruled by the Dukes of Burgundy, from the modern Netherlands to the border of Auvergne. Today, Burgundy is made up of the old provinces, Burgundy, Côte-dOr, Saône-et-Loire and this corresponds to the old duchy of Burgundy. However, the old county of Burgundy is not included inside the Burgundy region, also, a small part of the duchy of Burgundy is now inside the Champagne-Ardenne region. Nivernais, now the department of Nièvre, the climate of this region is essentially oceanic, with a continental influence. The regional council of Burgundy is the legislative assembly, the council has been chaired by the Socialist François Patriat since 2004. The councils seat is in the capital city Dijon, at 17 boulevard de la Trémouille, Burgundy is one of Frances main wine producing areas. The region is divided into the Côte-dOr, where the most expensive and prized Burgundies are found, and Beaujolais, Chablis, with regard to cuisine, the region is famous for the Burgundian dishes coq au vin, beef bourguignon, and époisses de Bourgogne cheese. Earlier, the part of Burgundy was heavily industrial, with coal mines near Montceau-les-Mines and iron foundries. These industries declined in the half of the twentieth century
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Reformation
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The period is usually considered to have begun with the publication of the Ninety-five Theses by Luther in 1517 to the Thirty Years War and ended with the Peace of Westphalia in 1648. The Protestant position, however, would come to incorporate doctrinal changes such as sola scriptura, the initial movement within Germany diversified, and other reform impulses arose independently of Luther. The spread of Gutenbergs printing press provided the means for the dissemination of religious materials in the vernacular. The largest groups were the Lutherans and Calvinists, Lutheran churches were founded mostly in Germany, the Baltics and Scandinavia, while the Reformed ones were founded in Switzerland, Hungary, France, the Netherlands and Scotland. The new movement influenced the Church of England decisively after 1547 under Edward VI and Elizabeth I, there were also reformation movements throughout continental Europe known as the Radical Reformation, which gave rise to the Anabaptist, Moravian and other Pietistic movements. The Roman Catholic Church responded with a Counter-Reformation initiated by the Council of Trent, much work in battling Protestantism was done by the well-organised new order of the Jesuits. In general, Northern Europe, with the exception of most of Ireland, southern Europe remained Roman Catholic, while Central Europe was a site of a fierce conflict, culminating in the Thirty Years War, which left it devastated. The oldest Protestant churches, such as the Unitas Fratrum and Moravian Church, the later Protestant Churches generally date their doctrinal separation from the Roman Catholic Church to the 16th century. The Reformation began as an attempt to reform the Roman Catholic Church, by priests who opposed what they perceived as false doctrines and ecclesiastic malpractice. They especially objected to the teaching and the sale of indulgences, and the abuses thereof, and to simony, the reformers saw these practices as evidence of the systemic corruption of the Churchs hierarchy, which included the pope. Unrest due to the Great Schism of Western Christianity excited wars between princes, uprisings among the peasants, and widespread concern over corruption in the Church, New perspectives came from John Wycliffe at Oxford University and from Jan Hus at the Charles University in Prague. Hus rejected indulgences and adopted a doctrine of justification by grace through faith alone, the Roman Catholic Church officially concluded this debate at the Council of Constance by condemning Hus, who was executed by burning despite a promise of safe-conduct. Wycliffe was posthumously condemned as a heretic and his corpse exhumed and burned in 1428, the Council of Constance confirmed and strengthened the traditional medieval conception of church and empire. The council did not address the national tensions or the theological tensions stirred up during the century and could not prevent schism. Pope Sixtus IV established the practice of selling indulgences to be applied to the dead, Pope Alexander VI was one of the most controversial of the Renaissance popes. He was the father of seven children, including Lucrezia and Cesare Borgia, in response to papal corruption, particularly the sale of indulgences, Luther wrote The Ninety-Five Theses. The Reformation was born of Luthers dual declaration – first, the discovering of Jesus and salvation by faith alone, the Protestant reformers were unanimous in agreement and this understanding of prophecy furnished importance to their deeds. It was the point and the battle cry that made the Reformation nearly unassailable
