A bearing is a machine element that constrains relative motion to only the desired motion, reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis. Most bearings facilitate the desired motion by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads applied to the parts. Rotary bearings hold rotating components such as shafts or axles within mechanical systems, transfer axial and radial loads from the source of the load to the structure supporting it; the simplest form of bearing, the plain bearing, consists of a shaft rotating in a hole. Lubrication is used to reduce friction. In the ball bearing and roller bearing, to prevent sliding friction, rolling elements such as rollers or balls with a circular cross-section are located between the races or journals of the bearing assembly. A wide variety of bearing designs exists to allow the demands of the application to be met for maximum efficiency, reliability and performance.
The term "bearing" is derived from the verb "to bear". The simplest bearings are bearing surfaces, cut or formed into a part, with varying degrees of control over the form, size and location of the surface. Other bearings are separate devices installed into a machine part; the most sophisticated bearings for the most demanding applications are precise devices. The invention of the rolling bearing, in the form of wooden rollers supporting, or bearing, an object being moved is of great antiquity, may predate the invention of the wheel. Though it is claimed that the Egyptians used roller bearings in the form of tree trunks under sleds, this is modern speculation, they are depicted in their own drawings in the tomb of Djehutihotep as moving massive stone blocks on sledges with liquid-lubricated runners which would constitute a plain bearing. There are Egyptian drawings of bearings used with hand drills; the earliest recovered example of a rolling element bearing is a wooden ball bearing supporting a rotating table from the remains of the Roman Nemi ships in Lake Nemi, Italy.
The wrecks were dated to 40 BC. Leonardo da Vinci incorporated drawings of ball bearings in his design for a helicopter around the year 1500; this is the first recorded use of bearings in an aerospace design. However, Agostino Ramelli is the first to have published sketches of thrust bearings. An issue with ball and roller bearings is that the balls or rollers rub against each other causing additional friction which can be reduced by enclosing the balls or rollers within a cage; the captured, or caged, ball bearing was described by Galileo in the 17th century. The first practical caged-roller bearing was invented in the mid-1740s by horologist John Harrison for his H3 marine timekeeper; this uses the bearing for a limited oscillating motion but Harrison used a similar bearing in a rotary application in a contemporaneous regulator clock. The first modern recorded patent on ball bearings was awarded to Philip Vaughan, a British inventor and ironmaster who created the first design for a ball bearing in Carmarthen in 1794.
His was the first modern ball-bearing design, with the ball running along a groove in the axle assembly. Bearings have played a pivotal role in the nascent Industrial Revolution, allowing the new industrial machinery to operate efficiently. For example, they saw use for holding wheel and axle to reduce friction over that of dragging an object by making the friction act over a shorter distance as the wheel turned; the first plain and rolling-element bearings were wood followed by bronze. Over their history bearings have been made of many materials including ceramic, glass, bronze, other metals and plastic which are all used today. Watch makers produce "jeweled" watches using sapphire plain bearings to reduce friction thus allowing more precise time keeping. Basic materials can have good durability; as examples, wooden bearings can still be seen today in old clocks or in water mills where the water provides cooling and lubrication. The first patent for a radial style ball bearing was awarded to Jules Suriray, a Parisian bicycle mechanic, on 3 August 1869.
The bearings were fitted to the winning bicycle ridden by James Moore in the world's first bicycle road race, Paris-Rouen, in November 1869. In 1883, Friedrich Fischer, founder of FAG, developed an approach for milling and grinding balls of equal size and exact roundness by means of a suitable production machine and formed the foundation for creation of an independent bearing industry; the modern, self-aligning design of ball bearing is attributed to Sven Wingquist of the SKF ball-bearing manufacturer in 1907, when he was awarded Swedish patent No. 25406 on its design. Henry Timken, a 19th-century visionary and innovator in carriage manufacturing, patented the tapered roller bearing in 1898; the following year he formed a company to produce his innovation. Over a century the company grew to make bearings of all types, including specialty steel and an array of related products and services. Erich Franke invented and patented the wire race bearing in 1934, his focus was on a bearing design with a cross section as small as possible and which could be integrated into the enclosing design.
After World War II he founded together with Gerh
A tool is an object used to extend the ability of an individual to modify features of the surrounding environment. Although many animals use simple tools, only human beings, whose use of stone tools dates back hundreds of millennia, use tools to make other tools; the set of tools needed to perform different tasks that are part of the same activity is called gear or equipment. While one may apply the term tool loosely to many things that are means to an end speaking an object is a tool only if, besides being constructed to be held, it is made of a material that allows its user to apply to it various degrees of force. If repeated use wears part of the tool down, it may be possible to restore it, thus tool falls under the taxonomic category implement, is on the same taxonomic rank as instrument, device, or ware. Anthropologists believe; because tools are used extensively by both humans and wild chimpanzees, it is assumed that the first routine use of tools took place prior to the divergence between the two species.
These early tools, were made of perishable materials such as sticks, or consisted of unmodified stones that cannot be distinguished from other stones as tools. Stone artifacts only date back to about 2.5 million years ago. However, a 2010 study suggests the hominin species Australopithecus afarensis ate meat by carving animal carcasses with stone implements; this finding pushes back the earliest known use of stone tools among hominins to about 3.4 million years ago. Finds of actual tools date back at least 2.6 million years in Ethiopia. One of the earliest distinguishable stone tool forms is the hand axe. Up until weapons found in digs were the only tools of “early man” that were studied and given importance. Now, more tools are recognized as culturally and relevant; as well as hunting, other activities required tools such as preparing food, “…nutting, grain harvesting and woodworking…” Included in this group are “flake stone tools". Tools are the most important items that the ancient humans used to climb to the top of the food chain.
“Man the hunter” as the catalyst for Hominin change has been questioned. Based on marks on the bones at archaeological sites, it is now more evident that pre-humans were scavenging off of other predators' carcasses rather than killing their own food. Mechanical devices experienced a major expansion in their use in Ancient Greece and Ancient Rome with the systematic employment of new energy sources waterwheels, their use expanded through the Dark Ages with the addition of windmills. Machine tools occasioned a surge in producing new tools in the industrial revolution. Advocates of nanotechnology expect a similar surge. One can classify tools according to their basic functions: Cutting and edge tools, such as the knife, scythe or sickle, are wedge-shaped implements that produce a shearing force along a narrow face. Ideally, the edge of the tool needs to be harder than the material being cut or else the blade will become dulled with repeated use, but resilient tools will require periodic sharpening, the process of removing deformation wear from the edge.
Other examples of cutting tools include gouges and drill bits. Moving tools move tiny items. Many are levers. Examples of force-concentrating tools include the hammer which moves a nail or the maul which moves a stake; these operate by applying physical compression to a surface. In the case of the screwdriver, the force called torque. By contrast, an anvil concentrates force on an object being hammered by preventing it from moving away when struck. Writing implements deliver a fluid to a surface via compression to activate the ink cartridge. Grabbing and twisting nuts and bolts with pliers, a glove, a wrench, etc. move items by some kind of force. Tools that enact chemical changes, including temperature and ignition, such as lighters and blowtorches. Guiding and perception tools include the ruler, set square, straightedge, microscope, clock, printer Shaping tools, such as molds, trowels. Fastening tools, such as welders, rivet nail guns, or glue guns. Information and data manipulation tools, such as computers, IDE, spreadsheetsSome tools may be combinations of other tools.
An alarm-clock is for example a combination of a perception tool. This enables the alarm-clock to be a tool. There is some debate on whether to consider protective gear items as tools, because they do not directly help perform work, just protect the worker like ordinary clothing, they do meet the general definition of tools and in many cases are necessary for the completion of the work. Personal protective equipment includes such items as gloves, safety glasses, ear defenders and biohazard suits. A simple machine is a mechanical device that changes the magnitude of a force. In general, they are the simplest mechanisms; the six classical simple machines which were defined by Renaissance scientists are: Lever Wheel and axle Pulley Inclined plane Wedge Screw Often, by design or coincidence, a tool may share key functional attributes with one or more other tools. In this case, s
An ironworks or iron works is a building or site where iron is smelted and where heavy iron and steel products are made. The term is both singular and plural, i.e. the singular of ironworks is ironworks. Ironworks succeed bloomeries. An integrated ironworks in the 19th century included one or more blast furnaces and a number of puddling furnaces or a foundry with or without other kinds of ironworks. After the invention of the Bessemer process, converters became widespread, the appellation steelworks replaced ironworks; the processes carried at ironworks are described as ferrous metallurgy, but the term siderurgy is occasionally used. This is derived from the Greek words sideros - ergon or ergos - work; this is an unusual term in English, it is best regarded as an anglicisation of a term used in French and other Romance languages. Ironworks is used as an omnibus term covering works undertaking one or more iron-producing processes; such processes or species of ironworks where they were undertaken include the following: Blast furnaces — which made pig iron from iron ore.
A thin film of metal oxide forms on the anode in the intense heat. The oxide forms a protective layer. Finery forges — which fined pig iron to produce bar iron, using charcoal as fuel in a finery and coal or charcoal in a chafery, it was necessary for there to be a preliminary refining process in a coke refinery. After puddling, the puddled ball needed shingling and to be drawn out into bar iron in a rolling mill. From the 1850s, pig iron might be decarburised to produce mild steel using one of the following: The Bessemer process in a Bessemer converter, improved by the Gilchrist-Thomas process; the mills operating converters of any type are better called steelworks, ironworks referring to former processes, like puddling. After bar iron had been produced in a finery forge or in the forge train of a rolling mill, it might undergo further processes in one of the following: A slitting mill - which cut a flat bar into rod iron suitable for making into nails. A tinplate works - where rolling mills made sheets of iron, which were coated with tin.
A plating forge with a tilt hammer, a lighter hammer with a rapid stroke rate, enabling the production of thinner iron, suitable for the manufacture of knives, other cutlery, so on. A cementation furnace might be used to convert the bar iron into blister steel by the cementation process, either as an end in itself or as the raw material for crucible steel. Most of these processes did not produce finished goods. Further processes were manual, including Manufacturing by blacksmiths or more specialist kind of smith, it might be used in shipbuilding. In the context of the iron industry, the term manufacture is best reserved for this final stage; the notable ironworks of the world are described here by country. See above for the largest producers and the notable ironworks in the alphabetical order. Cape Town Iron and Steel Works in Kuilsrivier, Western Cape American Iron Works in Hyattsville, Maryland Bath Iron Works in Maine Burden Iron Works in Troy, New York Cambria Iron Company in Johnstown, Pennsylvania Falling Creek Ironworks, Virginia.
Saugus Iron Works in Saugus, Massachusetts Toledo Iron Works in Miami, Florida Tredegar Iron Works at Richmond, Virginia U. S. Steel Fairfield Works, near Birmingham, Alabama Gary Works, near Chicago, Illinois Granite City Works, near St. Louis, Missouri Great Lakes Works, near Detroit, Michigan Mon Valley Works, near Pittsubutgh, Pennsylvania Vulcan Iron Works in Pennsylvania and other places Anben Group, Anshan & Benxi, Liaoning Baosteel, Shanghai Baotou Steel, Inner Mongolia Shougang Group, Beijing Wuhan Steel, Hebei Five major steel works of Steel Authority of India, Ltd Kalinganagar Works of Tata Steel in Kalinganagar, Odisha Vijayanagar Works of JSW Steel in Bellary, Karnataka The largest Japanese steel companies' main works are as follows: JFE Steel Chiba Works, Chiba, of JFE Eastern Works Keihin Works, Kanagawa, of JFE Eastern Works Fukuyama Works, Hiroshima, of JFE Western Works Kurashiki Works, Okayama, of JFE Western Works Kobe Steel Kakogawa Steel Works, Hyogo Nippon Steel & Sumitomo Metal Hirohata Works, Hyogo Kimitsu Steel Works, of former Nippon Steel), Chiba Nagoya Works, Aichi Ōita Works, Ōita, Ōita Yawata Steel Works, Chiba Kashima Works, Ibaraki Wakayama Works, Wakayama POSCO Gwangyang Steelworks, south coast Pohang Steelworks, east coast
The Bessemer process was the first inexpensive industrial process for the mass production of steel from molten pig iron before the development of the open hearth furnace. The key principle is removal of impurities from the iron by oxidation with air being blown through the molten iron; the oxidation raises the temperature of the iron mass and keeps it molten. Related decarburizing with air processes had been used outside Europe for hundreds of years, but not on an industrial scale. One such process has existed since the 11th century in East Asia, where the scholar Shen Kuo of that era described its use in the Chinese iron and steel industry. In the 17th century, accounts by European travelers detailed its possible use by the Japanese; the modern process is named after its inventor, the Englishman Henry Bessemer, who took out a patent on the process in 1856. The process was said to be independently discovered in 1851 by the American inventor William Kelly, though there is little to back up this claim.
The process using a basic refractory lining is known as the "basic Bessemer process" or Gilchrist–Thomas process after the English discoverers Percy Gilchrist and Sidney Gilchrist Thomas. A system akin to the Bessemer process has existed since the 11th century in East Asia. Economic historian Robert Hartwell writes that the Chinese of the Song Dynasty innovated a "partial decarbonization" method of repeated forging of cast iron under a cold blast. Sinologist Joseph Needham and historian of metallurgy Theodore A. Wertime have described the method as a predecessor to the Bessemer process of making steel; this process was first described by the prolific scholar and polymath government official Shen Kuo in 1075, when he visited Cizhou. Hartwell states that the earliest center where this was practiced was the great iron-production district along the Henan–Hebei border during the 11th century. In the 15th century the finery process, another process which shares the air-blowing principle with the Bessemer process, was developed in Europe.
In 1740 Benjamin Huntsman developed the crucible technique for steel manufacture, at his workshop in the district of Handsworth in Sheffield. This process had an enormous impact on the quantity and quality of steel production, but it was unrelated to the Bessemer-type process employing decarburization; the Japanese may have made use of a Bessemer-type process, observed by European travelers in the 17th century. The adventurer Johan Albrecht de Mandelslo describes the process in a book published in English in 1669, he writes, "They have, among others, particular invention for the melting of iron, without the using of fire, casting it into a tun done about on the inside without about half a foot of earth, where they keep it with continual blowing, take it out by ladles full, to give it what form they please." According to historian Donald Wagner, Madelslo did not visit Japan, so his description of the process is derived from accounts of other Europeans who had traveled to Japan. Wagner believes that the Japanese process may have been similar to the Bessemer process, but cautions that alternative explanations are plausible.
In the early 1850s, the American inventor William Kelly experimented with a method similar to the Bessemer process. Wagner writes that Kelly may have been inspired by techniques introduced by Chinese ironworkers hired by Kelly in 1854; when Bessemer's patent for the process was reported by Scientific American, Kelly responded by writing a letter to the magazine. In the letter, Kelly states that he had experimented with the process and claimed that Bessemer knew of Kelly's discovery, he wrote that "I have reason to believe my discovery was known in England three or four years ago, as a number of English puddlers visited this place to see my new process. Several of them have since returned to England and may have spoken of my invention there."Sir Henry Bessemer described the origin of his invention in his autobiography written in 1890. During the outbreak of the Crimean War, many English industrialists and inventors became interested in military technology. According to Bessemer, his invention was inspired by a conversation with Napoleon III in 1854 pertaining to the steel required for better artillery.
Bessemer claimed that it "was the spark which kindled one of the greatest revolutions that the present century had to record, for during my solitary ride in a cab that night from Vincennes to Paris, I made up my mind to try what I could to improve the quality of iron in the manufacture of guns." At the time steel was used to make only small items like cutlery and tools, but was too expensive for cannons. Starting in January 1855 he began working on a way to produce steel in the massive quantities required for artillery and by October he filed his first patent related to the Bessemer process, he patented the method a year in 1856. Bessemer licensed the patent for his process to four ironmasters, for a total of £27,000, but the licensees failed to produce the quality of steel he had promised—it was "rotten hot and rotten cold", according to his friend, William Clay—and he bought them back for £32,500, his plan had been to offer the licenses to one company in each of several geographic areas, at a royalty price per ton that included a lower rate on a proportion of their output in order to encourage production, but not so large a proportion that they might decide to reduce their selling prices.
By this method he hoped to cause the new process to gain in market share. He realised that the technical problem was due to impurities in the iron and concluded that the solution lay in knowing when to turn off the flow of air in his process so that the impurities were burned off but just the right amount of carbon remained. However, despite spending tens of thousands of poun
Crucible steel is steel made by melting pig iron and sometimes steel along with sand, glass and other fluxes, in a crucible. In ancient times steel and iron were impossible to melt using charcoal or coal fires, which could not produce temperatures high enough. However, pig iron, having a higher carbon content thus a lower melting point, could be melted, by soaking wrought iron or steel in the liquid pig-iron for long periods of time, the carbon content of the pig iron could be reduced as it diffused into the iron. Crucible steel of this type was produced in Central Asia during the medieval era; this produced a hard steel, but a composite steel, inhomogeneous, consisting of a high-carbon steel and a lower-carbon steel. This resulted in an intricate pattern when the steel was forged, filed or polished, with the most well-known examples coming from the wootz steel used in Damascus swords. Due to the use of fluxes the steel was much higher in quality and in carbon content compared to other methods of steel production of the time.
Techniques for production of high quality steel were developed by Benjamin Huntsman in England in the 18th century. Huntsman used coke rather than coal or charcoal, achieving temperatures high enough to melt steel and dissolve iron. Huntsman's process differed from some of the wootz processes in that it took a longer time to melt the steel and to cool it down and allowed more time for the diffusion of carbon. Huntsman's process used iron and steel as raw materials, in the form of blister steel, rather than direct conversion from cast iron as in puddling or the Bessemer process; the ability to melt the steel removed any inhomogeneities in the steel, allowing the carbon to dissolve evenly into the liquid steel and negating the prior need for extensive blacksmithing in an attempt to achieve the same result. It allowed steel to be poured into molds, or cast, for the first time; the homogeneous crystal structure of this cast steel improved its strength and hardness compared to preceding forms of steel.
The use of fluxes allowed nearly complete extraction of impurities from the liquid, which could simply float to the top for removal. This produced the first steel of modern quality, providing a means of efficiently changing excess wrought iron into useful steel. Huntsman's process increased the European output of quality steel suitable for use in items like knives and machinery, helping to pave the way for the Industrial revolution. Iron alloys are most broadly divided by their carbon content: cast iron has 2-4% carbon impurities; the much more valuable steel has a delicately intermediate carbon fraction, its material properties range according to the carbon percentage: high carbon steel is stronger but more brittle than low carbon steel. Crucible steel sequesters the raw input materials from the heat source, allowing precise control of carburization or oxidation. Fluxes, such as limestone, could be added to the crucible to remove or promote sulfur and other impurities, further altering its material qualities.
Various methods were used to produce crucible steel. According to Islamic texts such as al-Tarsusi and Abu Rayhan Biruni, three methods are described for indirect production of steel; the medieval Islamic historian Abu Rayhan Biruni provides the earliest reference of the production of Damascus steel. The first, the most common, traditional method is solid state carburization of wrought iron; this is a diffusion process in which wrought iron is packed in crucibles or a hearth with charcoal heated to promote diffusion of carbon into the iron to produce steel. Carburization is the basis for the wootz process of steel; the second method is the decarburization of cast iron by removing carbon from the cast iron. The third method uses wrought cast iron. In this process, wrought iron and cast iron may be heated together in a crucible to produce steel by fusion. In regard to this method Abu Rayhan Biruni states: "this was the method used in Hearth", it is proposed. Variations of co-fusion process have been found in Persia and Central Asia but have been found in Hyderabad, India called Deccani or Hyderabad process.
For the carbon, a variety of organic materials are specified by the contemporary Islamic authorities, including pomegranate rinds, fruit skins like orange peel, leaves as well as the white of egg and shells. Slivers of wood are mentioned in some of the Indian sources, but none of the sources mention charcoal. Crucible steel is attributed to production centres in India and Sri Lanka where it was produced using the so-called "wootz" process, it is assumed that its appearance in other locations was due to long distance trade. Only 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 CE, while the Indian/Sri Lankan material is as early as 300 BCE. India's iron ore had trace vanadium and other alloying elements leading to increased hardenability in Indian crucible steel, famous throughout the middle east for its ability to retain an edge.
While crucible steel is more attributed to the Middle East in early times, swords forged from crucible steel have been discovered in Europe in Scandinavia. The swords in question have an am
Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. Its usefulness derives from its low melting temperature; the alloy constituents affect its colour when fractured: white cast iron has carbide impurities which allow cracks to pass straight through, grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing. Carbon ranging from 1.8 to 4 wt%, silicon 1–3 wt% are the main alloying elements of cast iron. Iron alloys with lower 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. Since the compositions of most cast irons are around the eutectic point of the iron–carbon system, the melting temperatures range from 1,150 to 1,200 °C, about 300 °C lower than the melting point of pure iron of 1,535 °C.
Cast iron tends to be brittle, except for malleable cast irons. With its low melting point, good fluidity, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes and automotive industry parts, such as cylinder heads, cylinder blocks and gearbox cases, it is resistant to weakening by oxidation. The earliest cast-iron artifacts date to the 5th century BC, were discovered by archaeologists in what is now Jiangsu in China. Cast iron was used in ancient China for warfare and architecture. During the 15th century, cast iron became utilized for cannon in Burgundy, in England during the Reformation; the amounts of cast iron used for cannon required large scale production. The first cast-iron bridge was built during the 1770s by Abraham Darby III, is known as The Iron Bridge. Cast iron was used in the construction of buildings. Cast iron is made from pig iron, the product of smelting iron ore in a blast furnace.
Cast iron can be made directly from the molten pig iron or by re-melting pig iron along with substantial quantities of iron, limestone and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this burns out the carbon, which must be replaced. Depending on the application and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are added to the melt before the final form is produced by casting. Cast iron is sometimes melted in a special type of blast furnace known as a cupola, but in modern applications, it is more melted in electric induction furnaces or electric arc furnaces. After melting is complete, the molten cast iron is poured into ladle. Cast iron's properties alloyants. Next to carbon, silicon is the most important alloyant. A low percentage of silicon allows carbon to remain in solution forming iron carbide and the production of white cast iron.
A high percentage of silicon forces carbon out of solution forming graphite and the production of grey cast iron. Other alloying agents, chromium, molybdenum and vanadium counteracts silicon, promotes the retention of carbon, the formation of those carbides. Nickel and copper increase strength, machinability, but do not change the amount of graphite formed; the carbon in the form of graphite results in a softer iron, reduces shrinkage, lowers strength, decreases density. Sulfur a contaminant when present, forms iron sulfide, which prevents the formation of graphite and increases hardness; the problem with sulfur is. 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. The amount of manganese required to neutralize sulfur is 1.7 × sulfur content + 0.3%. If more than this amount of manganese is added manganese carbide forms, which increases hardness and chilling, except in grey iron, where up to 1% of manganese increases strength and density.
Nickel is one of the most common alloying elements because it refines the pearlite and graphite structure, improves toughness, evens out hardness differences between section thicknesses. Chromium is added in small amounts to reduce free graphite, produce chill, because it is a powerful carbide stabilizer. A small amount of tin can be added as a substitute for 0.5% chromium. Copper is added in the ladle or in the furnace, on the order of 0.5–2.5%, to decrease chill, refine graphite, increase fluidity. Molybdenum is added on the order of 0.3–1% to increase chill and refine the graphite and pearlite structure. Titanium is added as a degasser and deoxidizer, but it increases fluidity. 0.15–0.5% vanadium is added to cast iron to stabilize cementite, increase hardness, increase resistance to wear and heat. 0.1–0.3% zirconium helps to form graphite and increase fluidity. In malleable iron melts, bismuth is added, on the scale of 0.002–0.01%, to increase how much silicon can be added. In white iron, boron is added to aid in the production of malleable iron.
Wrought iron is an iron alloy with a low carbon content in contrast to cast iron. It is a semi-fused mass of iron with fibrous slag inclusions, which gives it a "grain" resembling wood, visible when it is etched or bent to the point of failure. Wrought iron is tough, ductile, corrosion-resistant and 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, it was given the name wrought because it was hammered, rolled or otherwise worked while hot enough to expel molten slag. The modern functional equivalent of wrought iron is low carbon steel. Neither wrought iron nor mild steel contain enough carbon to be hardenable by quenching, it is a refined iron with a small amount of slag forged out into fibres. The chemical analysis of the metal shows as much as 99 percent of iron; the slag characteristic of wrought iron is useful in blacksmithing operations and gives the material its peculiar fibrous structure.
The non-corrosive slag constituent causes wrought iron to be resistant to progressive corrosion. Moreover, the presence of slag produces a structure which diminishes the effect of fatigue caused by shocks and vibrations. A modest amount of wrought iron was refined into steel, used to produce swords, chisels and other edged tools as well as springs and files; the demand for wrought iron reached its peak in the 1860s, being in high demand for ironclad warships and railway use. However, as properties such as brittleness of mild steel improved with better ferrous metallurgy and as steel became less costly to make thanks to the Bessemer process and the Siemens-Martin process, the use of wrought iron declined. Many items, before they came to be made of mild steel, were produced from wrought iron, including rivets, wire, rails, railway couplings and steam pipes, bolts, handrails, wagon tires, straps for timber roof trusses, ornamental ironwork, among many other things. 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 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" means "worked iron". Wrought iron is a general term for the commodity, but is used more for finished iron goods, as manufactured by a blacksmith, it was used in that narrower sense in British Customs records, such manufactured iron was subject to a higher rate of duty than what might be called "unwrought" iron. Cast iron, unlike wrought iron, can not be worked either hot or cold. Cast iron can break. In the 17th, 18th, 19th centuries, wrought iron went by a wide variety of terms according to its form, origin, or quality. While the bloomery process produced wrought iron directly from ore, cast iron or pig iron were the starting materials used in the finery forge and puddling furnace.
Pig iron and cast iron have higher carbon content than wrought iron, but have a lower melting point than iron or steel. Cast and pig iron have excess slag which must be at least 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. For several years after the introduction of Bessemer and open hearth steel, there were different opinions as to what differentiated iron from steel. Fusion became accepted as more important than composition below a given low carbon concentration. Another difference is. 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%. Bar iron is a generic term sometimes used to distinguish it from cast iron, it is the equivalent of an ingot of cast metal, in a convenient form for handling, storage and further working into a finished product. The bars were the usual product of the finery forge, but not made by that process.
Rod iron—cut from flat bar iron in a slitting mill provided the raw material for spikes and nails. Hoop iron—suitable for the hoops of barrels, made by passing rod iron through rolling dies. Plate iron—sheets suitable for use as boiler plate. Blackplate—sheets thinner than plate iron, from the black rolling stage of tinplate production. Voyage iron—narrow flat bar iron, made or cut into bars of a particular weight, a commodity for sale in Africa for the Atlantic slave trade; the number of bars per ton increased from 70 per ton in the 1660s to 75–80 per ton in 1685 and "near 92 to the ton" in 1731. Charcoal iron—until the end of the 18th century, wrought iron was smelted from ore using charcoal, by the bloomery process. Wrought iron was produced from pig iron using a finery forge or in a Lancashire hearth; the resulting metal was variable, both in chemistry and slag content. Puddled iron—the puddling process was the first large-scale process to produce wrought iron. In the puddling process, pig iron is refined in a reverberatory furnace to prevent contamination of the iron from the sulfur in the coal or coke.