1.
Eugene O'Neill
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Eugene Gladstone ONeill was an American playwright and Nobel laureate in Literature. ONeills plays were among the first to include speeches in American vernacular and they struggle to maintain their hopes and aspirations, but ultimately slide into disillusionment and despair. Of his very few comedies, only one is well-known, nearly all of his other plays involve some degree of tragedy and personal pessimism. ONeill was born in a hotel, the Barrett House, at Broadway and 43rd Street, a commemorative plaque was first dedicated there in 1957. The site is now occupied by 1500 Broadway, which offices, retail. He was the son of Irish immigrant actor James ONeill and Mary Ellen Quinlan and his father suffered from alcoholism, his mother from an addiction to morphine, prescribed to relieve the pains of the difficult birth of her third son, Eugene. ONeill spent his summers at the Monte Cristo Cottage in New London and he attended Princeton University for one year. Accounts vary as to why he left, ONeill spent several years at sea, during which he suffered from depression and alcoholism. Despite this, he had a love for the sea and it became a prominent theme in many of his plays. ONeill joined the Marine Transport Workers Union of the Industrial Workers of the World, ONeills parents and elder brother Jamie died within three years of one another, not long after he had begun to make his mark in the theater. After his experience in 1912–13 at a sanatorium where he was recovering from tuberculosis, ONeill had previously been employed by the New London Telegraph, writing poetry as well as reporting. In the fall of 1914, he entered Harvard University to attend a course in dramatic technique given by Professor George Baker and he left after one year and did not complete the course. During the 1910s ONeill was a regular on the Greenwich Village literary scene, ONeill also had a brief romantic relationship with Reeds wife, writer Louise Bryant. ONeill was portrayed by Jack Nicholson in the 1981 film Reds and his involvement with the Provincetown Players began in mid-1916. ONeill is said to have arrived for the summer in Provincetown with a full of plays. He was not left alone in the dining-room when the reading had finished, the Provincetown Players performed many of ONeills early works in their theaters both in Provincetown and on MacDougal Street in Greenwich Village. Some of these early plays began downtown and then moved to Broadway, ONeills first published play, Beyond the Horizon, opened on Broadway in 1920 to great acclaim, and was awarded the Pulitzer Prize for Drama. His first major hit was The Emperor Jones, which ran on Broadway in 1920 and his best-known plays include Anna Christie, Desire Under the Elms, Strange Interlude, Mourning Becomes Electra, and his only well-known comedy, Ah, Wilderness
2.
Fabrication (metal)
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Metal fabrication is the building of metal structures by cutting, bending, and assembling processes. It is a value added process that involves the construction of machines and structures from various raw materials, a fab shop will bid on a job, usually based on the engineering drawings, and if awarded the contract will build the product. Large fab shops will employ a multitude of value added processes in one plant or facility including welding, cutting, forming and machining and these large fab shops offer additional value to their customers by limiting the need for purchasing personnel to locate multiple vendors for different services. Metal fabrication jobs usually start with shop drawings including precise measurements then move to the fabrication stage, fabrication shops are employed by contractors, OEMs and VARs. Typical projects include loose parts, structural frames for buildings and heavy equipment, cutting is done by sawing, shearing, or chiseling, torching with hand-held torches, and via numerical control cutters. Bending is done by hammering or via press brakes and similar tools, modern metal fabricators use press brakes to either coin or air-bend metal sheet into form. CNC-controlled backgauges use hard stops to position cut parts in order to place bend lines in the correct position, off-line programing software now makes programing the CNC-controlled press brakes seamless and very efficient. Assembling is done by welding, binding with adhesives, riveting, threaded fasteners, structural steel and sheet metal are the usual starting materials for fabrication, along with the welding wire, flux, and fasteners that will join the cut pieces. As with other manufacturing processes, both labor and automation are commonly used. The product resulting from fabrication may be called a fabrication, shops that specialize in this type of metal work are called fab shops. By comparison, machine shops also cut metal, but they are concerned with the machining of parts on machine tools. Firms that encompass both fab work and machining are also common, blacksmithing has always involved fabrication, although it was not always called by that name. The products produced by welders, which are referred to as weldments, are an example of fabrication. Boilermakers originally specialized in boilers, leading to their trades name, similarly, millwrights originally specialized in setting up grain mills and saw mills, but today they may be called upon for a broad range of fabrication work. Ironworkers, also known as steel erectors, also engage in fabrication, often the fabrications for structural work begin as prefabricated segments in a fab shop, then are moved to the site by truck, rail, or barge, and finally are installed by erectors. Standard raw materials used by metal fabricators are, plate metal formed and expanded metal tube stock and this is done with a variety of tools. The most common way to cut material is by Shearing, Special band saws designed for cutting metal have hardened blades, abrasive cut-off saws, also known as chop saws, are similar to miter saws but with a steel cutting abrasive disk. Cutting torches can cut very large sections of steel with little effort, burn tables are CNC cutting torches, usually natural gas powered
3.
Welded sculpture
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Welded sculpture is an art form in which sculpture is made using welding techniques. The Catalan artist Julio González is credited as one of the earliest developers of welded sculpture, Julio González came from a line of metalsmith workers, his grandfather was a goldsmith in Galicia, the established Catalonian capital in the early 19th century. Gonzálezs father, Concordio González, owned a workshop and as a boy, González learned from him the techniques of gold, silver. He is associated with the Spanish circle of artists of Montmartre, including Pablo Gargallo, Juan Gris, in 1918, he developed an interest in the artistic possibilities of welding, after learning the technique whilst working in the Renault Factory at Boulogne-Billancourt. This technique would become his principal contribution to sculpture, though during this period he also painted. In 1920 he renewed his acquaintance with Pablo Picasso, for whom he provided technical assistance in executing sculptures in iron. He also forged the infrastructures of Constantin Brâncușis plasters, in the winter of 1927-28, he showed Picasso how to use oxy-fuel welding and cutting. When their friendship re-established itself, Picasso and González collaborated on a piece called Woman in the Garden between 1928-1930, from October 1928 till 1932, both men worked together. Influenced by Picasso, the fifty-year-old González changed his style, exchanging bronze for iron, González began to formalize a new visual language in sculpture that would change the course of his career. Welding was increasingly used in sculpture from the 1930s as new processes such as arc welding were adapted to aesthetic purposes. Welding techniques, including cutting, can be used to cut. Artist Richard Hunt said The idea of exploiting welding methods and the strength of metals opened up many possibilities to me. Van Wagner Collischan
4.
Metal
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A metal is a material that is typically hard, opaque, shiny, and has good electrical and thermal conductivity. Metals are generally malleable—that is, they can be hammered or pressed permanently out of shape without breaking or cracking—as well as fusible and ductile, about 91 of the 118 elements in the periodic table are metals, the others are nonmetals or metalloids. Some elements appear in both metallic and non-metallic forms, astrophysicists use the term metal to collectively describe all elements other than hydrogen and helium, the simplest two, in a star. The star fuses smaller atoms, mostly hydrogen and helium, to larger ones over its lifetime. In that sense, the metallicity of an object is the proportion of its matter made up of all chemical elements. Many elements and compounds that are not normally classified as metals become metallic under high pressures, the atoms of metallic substances are typically arranged in one of three common crystal structures, namely body-centered cubic, face-centered cubic, and hexagonal close-packed. In bcc, each atom is positioned at the center of a cube of eight others, in fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature, atoms of metals readily lose their outer shell electrons, resulting in a free flowing cloud of electrons within their otherwise solid arrangement. This provides the ability of metallic substances to easily transmit heat, while this flow of electrons occurs, the solid characteristic of the metal is produced by electrostatic interactions between each atom and the electron cloud. This type of bond is called a metallic bond, Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form oxides over various timescales. Examples,4 Na + O2 →2 Na2O2 Ca + O2 →2 CaO4 Al +3 O2 →2 Al2O3, the transition metals are slower to oxidize because they form a passivating layer of oxide that protects the interior. Others, like palladium, platinum and gold, do not react with the atmosphere at all, some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades. The oxides of metals are generally basic, as opposed to those of nonmetals, exceptions are largely oxides with very high oxidation states such as CrO3, Mn2O7, and OsO4, which have strictly acidic reactions. Painting, anodizing or plating metals are good ways to prevent their corrosion, however, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water and the two form an electrochemical cell, and if the coating is less reactive than the coatee. Metals in general have high conductivity, high thermal conductivity. Typically they are malleable and ductile, deforming under stress without cleaving, in terms of optical properties, metals are shiny and lustrous. Sheets of metal beyond a few micrometres in thickness appear opaque, although most metals have higher densities than most nonmetals, there is wide variation in their densities, lithium being the least dense solid element and osmium the densest
5.
Thermoplastic
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A thermoplastic, or thermosoftening plastic, is a plastic material, a polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling. Most thermoplastics have a molecular weight. The polymer chains associate through intermolecular forces, which weaken rapidly with increased temperature, thermoplastics differ from thermosetting polymers, which form irreversible chemical bonds during the curing process. Thermosets do not melt, but decompose and do not reform upon cooling, above its glass transition temperature and below its melting point, the physical properties of a thermoplastic change drastically without an associated phase change. Some thermoplastics do not fully crystallize below the transition temperature. Amorphous and semi-amorphous plastics are used when high optical clarity is necessary, amorphous and semi-amorphous plastics are less resistant to chemical attack and environmental stress cracking because they lack a crystalline structure. Brittleness can be decreased with the addition of plasticizers, which increases the mobility of amorphous chain segments to effectively lowers the transition temperature. Modification of the polymer through copolymerization or through the addition of side chains to monomers before polymerization can also lower it. Naval Research Laboratory developed thermoplastic armor, that can be repaired in the field by a user via tools for pressing irons, acrylic, a polymer called poly, is also known by trade names such as Lucite, Perspex and Plexiglas. It serves as a substitute for glass for items such as aquariums, motorcycle helmet visors, aircraft windows, viewing ports of submersibles. It is extensively used to make signs, including lettering and logos, in medicine, it is used in bone cement and to replace eye lenses. Acrylic paint consists of PMMA particles suspended in water, acrylonitrile butadiene styrene is a terpolymer synthesized from styrene and acrylonitrile in the presence of polybutadiene. ABS is a material that exhibits high impact resistance and mechanical toughness. It poses few risks to health under normal handling. It is used in consumer products, such as toys, appliances. Nylon belongs to a class of polymers called polyamides and it has served as a substitute mainly for hemp, cotton and silk, in products such as parachutes, cords, sails, flak vests and womens clothing. Nylon fibers are useful in making fabrics, rope, carpets and musical strings, whereas in bulk form, Nylon is used for mechanical parts including machine screws, gears, in addition, it is used in the manufacture of heat-resistant composite materials. Polylactic acid is a biodegradable thermoplastic aliphatic polyester derived from renewable resources, such as starch, tapioca roots, chips or starch
6.
Fusion welding
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Fusion welding is a generic term for welding processes that rely upon melting to join materials of similar compositions and melting points. Due to the phase transitions inherent to these processes, a heat-affected zone is created in the material,755. In contrast to fusion welding, solid-state welding does not involve the melting of materials, fusion welding was a key factor of in the creation of modern civilization. It is also important for maintaining civilization. Fusion welding holds a key role in construction, besides bolts and rivets there are no other practical method for joining pieces of metal securely. Fusion welding is used to make many everyday items, from construction to airplanes to cars fusion welding is very common. Another common use of welding is in artwork. There is a community that uses both arc and flame contact welding artwork. Arc welding is one of the types of fusion welding. Arc welding joins two pieces of metal together by using an intermediate filler metal, the way this works is by completing an electrical circuit to create an electrical arc. This electrical arc is 6500oF in its center and this electrical arc is created at the tip of the filler metal. As the arc melts the metal it is moved either by a person or a machine along the gap in the creating a bond. This method is common as it is typically done with a hand held machine. Arc welding machines are portable and can be brought on to job sites, arc welding is also the most common method of underwater welding. Electrical arcs form between points separated by a gas, in the process of underwater welding a bubble of gas is blown around the area being welded so that an electrical arc may form. Ship hulls are repaired and oil rigs are maintained with underwater arc welding, resistance welding is done using two electrodes. Each electrode comes into contact with one of the pieces being welded, the two pieces of metal are then pressed together between the electrodes. While they are being pressed an electric current is ran through them, as this happens the pieces of metal begin to heat up at the point where they come into contact
7.
Brazing
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The filler metal flows into the gap between close-fitting parts by capillary action. The filler metal is slightly above its melting temperature while protected by a suitable atmosphere. It then flows over the metal and is then cooled to join the work pieces together. It is similar to soldering, except for the use of higher temperatures, a major advantage of brazing is the ability to join the same or different metals with considerable strength. High-quality brazed joints require that parts be closely fitted, and the base metals exceptionally clean, in most cases, joint clearances of 0.03 to 0.08 mm are recommended for the best capillary action and joint strength. However, in some brazing operations it is not uncommon to have joint clearances around 0.6 mm, cleanliness of the brazing surfaces is also important, as any contamination can cause poor wetting. The two main methods for cleaning parts, prior to brazing, are cleaning and abrasive or mechanical cleaning. In the case of mechanical cleaning, it is important to maintain the surface roughness as wetting on a rough surface occurs much more readily than on a smooth surface of the same geometry. Another consideration is the effect of temperature and time on the quality of brazed joints, as the temperature of the braze alloy is increased, the alloying and wetting action of the filler metal increases as well. In general, the brazing temperature selected must be above the point of the filler metal. However, several factors influence the joint designers temperature selection, the effect of time on the brazed joint primarily affects the extent to which these effects are present. In general, however, most production processes are selected to minimize brazing time and this is not always the case, however, since in some non-production settings, time and cost are secondary to other joint attributes. Unless brazing operations are contained within an inert or reducing atmosphere environment, the flux also serves the purpose of cleaning any contamination left on the brazing surfaces. Flux can be applied in any number of forms including flux paste, liquid, flux can also be applied using brazing rods with a coating of flux, or a flux core. In either case, the flows into the joint when applied to the heated joint and is displaced by the molten filler metal entering the joint. Excess flux should be removed when the cycle is completed because flux left in the joint can lead to corrosion, impede joint inspection, phosphorus-containing brazing alloys can be self-fluxing when joining copper to copper. Fluxes are generally selected based on their performance on particular base metals, to be effective, the flux must be chemically compatible with both the base metal and the filler metal being used. Self-fluxing phosphorus filler alloys produce brittle phosphides if used on iron or nickel, as a general rule, longer brazing cycles should use less active fluxes than short brazing operations
8.
Soldering
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Soldering, is a process in which two or more items are joined together by melting and putting a filler metal into the joint, the filler metal having a lower melting point than the adjoining metal. Soldering differs from welding in that soldering does not involve melting the work pieces, in brazing, the filler metal melts at a higher temperature, but the work piece metal does not melt. In the past, nearly all solders contained lead, but environmental and health concerns have increasingly dictated use of alloys for electronics. There is evidence that soldering was employed as early as 5000 years ago in Mesopotamia, soldering and brazing are thought to have originated very early in the history of metal-working, probably before 4000 BC. Sumerian swords from ~3000 BC were assembled using hard soldering, soldering was historically used to make jewelry items, cooking ware and tools, as well as other uses such as in assembling stained glass. Soldering is used in plumbing, electronics, and metalwork from flashing to jewelry, jewelry components, machine tools and some refrigeration and plumbing components are often assembled and repaired by the higher temperature silver soldering process. Small mechanical parts are often soldered or brazed as well, soldering is also used to join lead came and copper foil in stained glass work. Electronic soldering connects electrical wiring and electronic components to printed circuit boards, soldering filler materials are available in many different alloys for differing applications. In electronics assembly, the alloy of 63% tin and 37% lead has been the alloy of choice. Other alloys are used for plumbing, mechanical assembly, and other applications, a eutectic formulation has advantages when applied to soldering, the liquidus and solidus temperatures are the same, so there is no plastic phase, and it has the lowest possible melting point. Having the lowest possible melting point minimizes heat stress on electronic components during soldering, and, having no plastic phase allows for quicker wetting as the solder heats up, and quicker setup as the solder cools. A non-eutectic formulation must remain still as the temperature drops through the liquidus and solidus temperatures, any movement during the plastic phase may result in cracks, resulting in an unreliable joint. Common solder formulations based on tin and lead are listed below and they are also suggested anywhere young children may come into contact with, or for outdoor use where rain and other precipitation may wash the lead into the groundwater. Unfortunately, most lead-free solders are not eutectic formulations, melting at around 250 °C, alloying silver with other metals changes the melting point, adhesion and wetting characteristics, and tensile strength. Of all the brazing alloys, silver solders have the greatest strength, specialty alloys are available with properties such as higher strength, the ability to solder aluminum, better electrical conductivity, and higher corrosion resistance. The purpose of flux is to facilitate the soldering process, one of the obstacles to a successful solder joint is an impurity at the site of the joint, for example, dirt, oil or oxidation. The impurities can be removed by mechanical cleaning or by chemical means and this effect is accelerated as the soldering temperatures increase and can completely prevent the solder from joining to the workpiece. One of the earliest forms of flux was charcoal, which acts as a reducing agent, some fluxes go beyond the simple prevention of oxidation and also provide some form of chemical cleaning
9.
Melting
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Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the energy of the solid increases, typically by the application of heat or pressure. At the melting point, the ordering of ions or molecules in the solid breaks down to an ordered state. Substances in the state generally have reduced viscosity as the temperature increases. An exception to this principle is the element sulfur, whose viscosity increases to a point due to polymerization, some organic compounds melt through mesophases, states of partial order between solid and liquid. Melting is therefore classified as a phase transition. Melting occurs when the Gibbs free energy of the liquid becomes lower than the solid for that material, the temperature at which this occurs is dependent on the ambient pressure. Low-temperature helium is the only exception to the general rule. Helium-3 has an enthalpy of fusion at temperatures below 0.3 K. Helium-4 also has a very slightly negative enthalpy of fusion below 0.8 K. This means that, at appropriate constant pressures, heat must be removed from these substances in order to melt them, among the theoretical criteria for melting, the Lindemann and of Born criteria are those most frequently used as a basis to analyse the melting conditions. The Lindemann melting criterion is supported by experimental data both for crystalline materials and for transitions in amorphous materials. The Born criterion is based on rigidity catastrophe caused by the elastic shear modulus. Under a standard set of conditions, the point of a substance is a characteristic property. The melting point is equal to the freezing point. However, under carefully created conditions, supercooling or superheating past the melting or freezing point can occur, water on a very clean glass surface will often supercool several degrees below the freezing point without freezing. Fine emulsions of pure water have been cooled to −38 degrees Celsius without nucleation to form ice, nucleation occurs due to fluctuations in the properties of the material. If the material is still there is often nothing to trigger this change. Thermodynamically, the liquid is in the metastable state with respect to the crystalline phase
10.
Pressure
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Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the relative to the ambient pressure. Various units are used to express pressure, Pressure may also be expressed in terms of standard atmospheric pressure, the atmosphere is equal to this pressure and the torr is defined as 1⁄760 of this. Manometric units such as the centimetre of water, millimetre of mercury, Pressure is the amount of force acting per unit area. The symbol for it is p or P, the IUPAC recommendation for pressure is a lower-case p. However, upper-case P is widely used. The usage of P vs p depends upon the field in one is working, on the nearby presence of other symbols for quantities such as power and momentum. Mathematically, p = F A where, p is the pressure, F is the normal force and it relates the vector surface element with the normal force acting on it. It is incorrect to say the pressure is directed in such or such direction, the pressure, as a scalar, has no direction. The force given by the relationship to the quantity has a direction. If we change the orientation of the element, the direction of the normal force changes accordingly. Pressure is distributed to solid boundaries or across arbitrary sections of normal to these boundaries or sections at every point. It is a parameter in thermodynamics, and it is conjugate to volume. The SI unit for pressure is the pascal, equal to one newton per square metre and this name for the unit was added in 1971, before that, pressure in SI was expressed simply in newtons per square metre. Other units of pressure, such as pounds per square inch, the CGS unit of pressure is the barye, equal to 1 dyn·cm−2 or 0.1 Pa. Pressure is sometimes expressed in grams-force or kilograms-force per square centimetre, but using the names kilogram, gram, kilogram-force, or gram-force as units of force is expressly forbidden in SI. The technical atmosphere is 1 kgf/cm2, since a system under pressure has potential to perform work on its surroundings, pressure is a measure of potential energy stored per unit volume. It is therefore related to density and may be expressed in units such as joules per cubic metre. Similar pressures are given in kilopascals in most other fields, where the prefix is rarely used
11.
Heat
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WWE Heat was a professional wrestling television program produced by World Wrestling Entertainment. Heat was most recently streamed on WWE. com on Friday afternoons for North American viewers, the final episode was uploaded to WWE. com. The show was replaced internationally with WWE Vintage Collection, a program featuring classic matches, the show was originally introduced on the USA Network on August 2,1998 in the United States. The one-hour show would be broadcast on Sunday nights, it would be live most weeks and it was the second primary program of the WWFs weekly television show line-up, serving as a supplement to the Monday Night Raw program. On scheduled WWF pay-per-view event nights, Heat would also serve as a show to the events. The show was signed for only 6 episodes but was very popular and was continued. With the premiere of SmackDown. in August 1999, coverage of Heat was significantly reduced in favor of the newer show, also led to Heat being taped before SmackDown. With matches for WWF syndication programs like Jakked/Metal being taped before Raw broadcasts, premiered, also Heat briefly became a complete weekly summary show, featuring occasional interviews and music videos. After only a few weeks following the change, Heat began airing exclusive matches again. Occasionally, special editions of the show aired heavily promoted, for Super Bowl XXXIII in 1999, Heat aired as Halftime Heat on the USA Network during halftime of the Super Bowl. These specials ended following the move to MTV in 2000. When the show started airing on MTV in late 2000, it was broadcast live from WWF New York, WWF personalities and performers would appear at the restaurant as special guests while Michael Cole and Tazz provided commentary to matches. The United Kingdoms coverage of Heat began in January 2000, when Channel 4 started broadcasting the show at 4pm on Sundays and these one-hour shows were a magazine-type show, usually featuring three or four brief matches as well as highlights from Raw and SmackDown. Were aired on this version of the show, a separate commentary team was used on airings in the United Kingdom, with references aimed more at that specific audience. The two-person announce team was a mix of individuals including Kevin Kelly, Michael Cole, Michael Hayes, during the middle of 2000, Heat started to get moved around the Channel 4 schedule, usually between the afternoon and midnight. Towards the end of 2000, the show was moved to being broadcast in the early-hours of Monday mornings. The show stayed in the time-slot until December 2001 when Channel 4s deal with the World Wrestling Federation expired in the United Kingdom, in April 2002, the show returned to its original filming schedule, again before Raw. Eventually, the live from WWF New York format was retired, ratings were still moderate for Heat, although the show lost some popularity once SmackDown
12.
Oxidation
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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
13.
Oxy-fuel welding
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Oxy-fuel welding and oxy-fuel cutting are processes that use fuel gases and oxygen to weld and cut metals, respectively. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903, pure oxygen, instead of air, is used to increase the flame temperature to allow localized melting of the workpiece material in a room environment. In recent decades it has been obsolesced in almost all industrial uses due to various arc welding methods offering more consistent mechanical weld properties, gas welding is still used for metal-based artwork and in smaller home based shops, as well as situations where accessing electricity would present difficulties. In oxy-fuel welding, a torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal, the molten pool is generally supplied with additional metal called filler. Filler material depends upon the metals to be welded, in oxy-fuel cutting, a torch is used to heat metal to its kindling temperature. A stream of oxygen is then trained on the metal, burning it into an oxide that flows out of the kerf as slag. Torches that do not mix fuel with oxygen are not considered oxy-fuel torches, most metals cannot be melted with a single-tank torch. Consequently, single-tank torches are typically suitable for soldering and brazing, oxy-gas torches are or have been used for, Welding metal, see below. Depositing metal to build up a surface, as in hardfacing, also, oxy-hydrogen flames are used, in stone working for flaming where the stone is heated and a top layer crackles and breaks. A steel circular brush is attached to a grinder and used to remove the first layer leaving behind a bumpy surface similar to hammered bronze. In the glass industry for fire polishing, in jewelry production for water welding using a water torch. in automotive repair, removing a seized bolt. Formerly, to heat lumps of quicklime to obtain a white light called limelight. Formerly, in works, as platinum is fusible only in the oxyhydrogen flame. The apparatus used in gas welding consists basically of an oxygen source and this sort of torch can also be used for soldering and brazing. The cylinders are carried in a special wheeled trolley. There have been examples of oxyhydrogen cutting sets with small gas cylinders worn on the back in a backpack harness, for rescue work. There are also examples of pressurized liquid fuel cutting torches, usually using gasoline and these are used for their increased portability
14.
Shielded metal arc welding
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An electric current, in the form of either alternating current or direct current from a welding power supply, is used to form an electric arc between the electrode and the metals to be joined. The workpiece and the electrode melts forming a pool of molten metal that cools to form a joint, because of the versatility of the process and the simplicity of its equipment and operation, shielded metal arc welding is one of the worlds first and most popular welding processes. The process is used primarily to iron and steels but aluminium, nickel. In 1885, Nikolay Benardos and Stanisław Olszewski developed carbon arc welding, obtaining American patents from 1887 showing a rudimentary electrode holder, in 1888, the consumable metal electrode was invented by Nikolay Slavyanov. Later in 1890, C. L. Coffin received U. S, patent 428,459 for his arc welding method that utilized a metal electrode. The process, like SMAW, deposited melted electrode metal into the weld as filler, around 1900, A. P. Strohmenger and Oscar Kjellberg released the first coated electrodes. Strohmenger used clay and lime coating to stabilize the arc, while Kjellberg dipped iron wire into mixtures of carbonates and silicates to coat the electrode, in 1912, Strohmenger released a heavily coated electrode, but high cost and complex production methods prevented these early electrodes from gaining popularity. In 1927, the development of an extrusion process reduced the cost of coating electrodes while allowing manufacturers to produce more complex coating mixtures designed for specific applications, in the 1950s, manufacturers introduced iron powder into the flux coating, making it possible to increase the welding speed. In 1938 K. K. Madsen described a variation of SMAW. It briefly gained popularity in the 1960s after receiving publicity for its use in Japanese shipyards though today its applications are limited, another little used variation of the process, known as firecracker welding, was developed around the same time by George Hafergut in Austria. To strike the arc, the electrode is brought into contact with the workpiece by a very light touch with the electrode to the base metal then is pulled back slightly. This initiates the arc and thus the melting of the workpiece and the consumable electrode, striking an arc, which varies widely based upon electrode and workpiece composition, can be the hardest skill for beginners. The tip of the needs to be at a lower angle to the workpiece. As the electrode melts, the flux covering disintegrates, giving off shielding gases that protect the area from oxygen. In addition, the flux provides molten slag which covers the metal as it travels from the electrode to the weld pool. Once part of the pool, the slag floats to the surface. Once hardened, it must be chipped away to reveal the finished weld, as welding progresses and the electrode melts, the welder must periodically stop welding to remove the remaining electrode stub and insert a new electrode into the electrode holder. This activity, combined with chipping away the slag, reduces the amount of time that the welder can spend laying the weld, in general, the operator factor, or the percentage of operators time spent laying weld, is approximately 25%
15.
Electrode
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An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit. The word was coined by William Whewell at the request of the scientist Michael Faraday from the Greek words elektron, meaning amber, and hodos, an electrode in an electrochemical cell is referred to as either an anode or a cathode. The anode is now defined as the electrode at which electrons leave the cell and oxidation occurs, each electrode may become either the anode or the cathode depending on the direction of current through the cell. A bipolar electrode is an electrode that functions as the anode of one cell, a primary cell is a special type of electrochemical cell in which the reaction cannot be reversed, and the identities of the anode and cathode are therefore fixed. The anode is always the negative electrode, the cell can be discharged but not recharged. A secondary cell, for example a rechargeable battery, is a cell in which the reactions are reversible. When the cell is being charged, the anode becomes the positive and this is also the case in an electrolytic cell. When the cell is being discharged, it behaves like a cell, with the anode as the negative. In a vacuum tube or a semiconductor having polarity the anode is the positive electrode, the electrons enter the device through the cathode and exit the device through the anode. Many devices have other electrodes to control operation, e. g. base, gate, control grid. In a three-electrode cell, an electrode, also called an auxiliary electrode, is used only to make a connection to the electrolyte so that a current can be applied to the working electrode. The counter electrode is made of an inert material, such as a noble metal or graphite. In arc welding an electrode is used to conduct current through a workpiece to fuse two pieces together. Depending upon the process, the electrode is either consumable, in the case of gas metal arc welding or shielded metal arc welding, or non-consumable, such as in gas tungsten arc welding. For a direct current system the weld rod or stick may be a cathode for a filling type weld or an anode for other welding processes, for an alternating current arc welder the welding electrode would not be considered an anode or cathode. Electrodes are used to provide current through nonmetal objects to them in numerous ways. These electrodes are used for advanced purposes in research and investigation
16.
Flux (metallurgy)
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In metallurgy, a flux is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time and they are used in both extractive metallurgy and metal joining. Some of the earliest known fluxes were carbonate of soda, potash, charcoal, coke, borax, lime, lead sulfide, iron ore was also used as a flux in the smelting of copper. As cleaning agents, fluxes facilitate soldering, brazing, and welding by removing oxidation from the metals to be joined, the slag is a liquid mixture of ash, flux, and other impurities. This reduction of slag viscosity with temperature, increasing the flow of slag in smelting, is the origin of the word flux in metallurgy. Fluxes are also used in foundries for removing impurities from molten nonferrous metals such as aluminium, in high-temperature metal joining processes, the primary purpose of flux is to prevent oxidation of the base and filler materials. Tin-lead solder attaches very well to copper, but poorly to the oxides of copper. Flux is a substance which is inert at room temperature. Additionally, flux allows solder to flow easily on the piece rather than forming beads as it would otherwise. In some applications molten flux also serves as a heat transfer medium, fluxes for soft soldering are typically of organic nature, though inorganic fluxes, usually based on halogenides and/or acids, are also used in non-electronics applications. Fluxes for brazing operate at higher temperatures and are therefore mostly inorganic. Organic fluxes typically consist of four components, Activators - chemicals disrupting/dissolving the metal oxides. Their role is to expose unoxidized, easily wettable metal surface and aid soldering by other means, highly active fluxes contain chemicals that are corrosive at room temperature. The compounds used include metal halides, hydrochloric acid, phosphoric acid, Salts of mineral acids with amines are also used as aggressive activators. Aggressive fluxes typically facilitate corrosion, require careful removal, and are unsuitable for finer work, Activators for fluxes for soldering and brazing aluminium often contain fluorides. Milder activators begin to react with oxides only at elevated temperature, typical compounds used are carboxylic acids and sometimes amino acids. Some milder fluxes also contain halides or organohalides, vehicles - high-temperature tolerant chemicals in the form of non-volatile liquids or solids with suitable melting point, they are generally liquid at soldering temperatures. Solid vehicles tend to be based on natural or modified rosin or natural or synthetic resins, water-soluble organic fluxes tend to contain vehicles based on high-boiling polyols - glycols, diethylene glycol and higher polyglycols, polyglycol-based surfactants and glycerol
17.
Slag (welding)
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Slag is formed when flux, the solid shielding material used in the welding process, melts in or on top of the weld zone. Slag is the solidified remaining flux after the weld area cools, Welding flux is a combination of carbonate and silicate materials used in welding processes to shield the weld from atmospheric gases. When the heat of the zone reaches the flux, the flux melts. The gases produced push the gas back, preventing oxidation. The melted flux covers the metal in the weld zone. Flux materials may contribute to metal behavior in the molten metal. The flux cover also helps insulate the weld and reduce the cooling rate. It is possible for areas of slag to become embedded within the solidified metal and these are called inclusions and are a form of welding defect. Inclusions may be visible on the surface after cleaning, or may be contained within the metal. Removal is usually done using manual or power tools, manual tools may include a welding or chipping hammer, which has a pointed tip on one end to break up large chunks of slag efficiently, or wire brushes. Power tools include angle grinders with grinder disks or wire brush wheels, slag - the similar byproduct of metal production processes Flux Welding
18.
Gas tungsten arc welding
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Gas tungsten arc welding, also known as tungsten inert gas welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from contamination by an inert shielding gas. A constant-current welding power supply produces electrical energy, which is conducted across the arc through a column of highly ionized gas, GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminum, magnesium, and copper alloys. The process grants the operator control over the weld than competing processes such as shielded metal arc welding. However, GTAW is comparatively more complex and difficult to master, a related process, plasma arc welding, uses a slightly different welding torch to create a more focused welding arc and as a result is often automated. After the discovery of the pulsed electric arc in 1800 by Humphry Davy and of the continuous electric arc in 1802 by Vasily Petrov. C. L. Processes using flux-covered electrodes did not satisfactorily protect the area from contamination. To solve the problem, bottled inert gases were used in the beginning of the 1930s, a few years later, a direct current, gas-shielded welding process emerged in the aircraft industry for welding magnesium. Russell Meredith of Northrop Aircraft perfected the process in 1941, Meredith named the process Heliarc because it used a tungsten electrode arc and helium as a shielding gas, but it is often referred to as tungsten inert gas welding. The American Welding Societys official term is gas tungsten arc welding, linde Air Products developed a wide range of air-cooled and water-cooled torches, gas lenses to improve shielding, and other accessories that increased the use of the process. Initially, the electrode overheated quickly and, despite tungstens high melting temperature, to address this problem, the polarity of the electrode was changed from positive to negative, but the change made it unsuitable for welding many non-ferrous materials. Finally, the development of alternating current units made it possible to stabilize the arc, developments continued during the following decades. Linde developed water-cooled torches that helped prevent overheating when welding with high currents, the use of any shielding gas containing an oxygen compound, such as carbon dioxide, quickly contaminates the tungsten electrode, making it unsuitable for the TIG process. In 1953, a new process based on GTAW was developed, called plasma arc welding, development within the GTAW process has continued as well, and today a number of variations exist. Among the most popular are the pulsed-current, manual programmed, hot-wire, dabber, manual gas tungsten arc welding is a relatively difficult welding method, due to the coordination required by the welder. Maintaining a short arc length, while preventing contact between the electrode and the workpiece, is also important, to strike the welding arc, a high frequency generator provides an electric spark. Once the arc is struck, the moves the torch in a small circle to create a welding pool, the size of which depends on the size of the electrode. While maintaining a constant separation between the electrode and the workpiece, the operator moves the torch back slightly and tilts it backward about 10–15 degrees from vertical
19.
Tungsten
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Tungsten, also known as wolfram, is a chemical element with symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten, which translates to heavy stone. Its name in Swedish is volfram, however, in order to distinguish it from scheelite, a hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth almost exclusively in chemical compounds. It was identified as a new element in 1781, and first isolated as a metal in 1783 and its important ores include wolframite and scheelite. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the elements discovered, melting at 3,422 °C,6,192 °F. Its high density is 19.3 times that of water, comparable to that of uranium and gold, polycrystalline tungsten is an intrinsically brittle and hard material, making it difficult to work. However, pure single-crystalline tungsten is more ductile, and can be cut with a hard-steel hacksaw, tungstens many alloys have numerous applications, including incandescent light bulb filaments, X-ray tubes, electrodes in TIG welding, superalloys, and radiation shielding. Tungstens hardness and high density give it military applications in penetrating projectiles, tungsten compounds are also often used as industrial catalysts. Tungsten is the metal from the third transition series that is known to occur in biomolecules. It is the heaviest element known to be essential to any living organism, tungsten interferes with molybdenum and copper metabolism and is somewhat toxic to animal life. In its raw form, tungsten is a hard metal that is often brittle. If made very pure, tungsten retains its hardness, and becomes malleable enough that it can be worked easily and it is worked by forging, drawing, or extruding. Tungsten objects are commonly formed by sintering. Of all metals in pure form, tungsten has the highest melting point, lowest vapor pressure, although carbon remains solid at higher temperatures than tungsten, carbon sublimes, rather than melts, so tungsten is considered to have a higher melting point. Tungsten has the lowest coefficient of expansion of any pure metal. The low thermal expansion and high melting point and tensile strength of tungsten originate from strong covalent bonds formed between tungsten atoms by the 5d electrons, alloying small quantities of tungsten with steel greatly increases its toughness. Tungsten exists in two crystalline forms, α and β. The former has a cubic structure and is the more stable form
20.
Argon
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Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the table and is a noble gas. Argon is the third-most abundant gas in the Earths atmosphere, at 0. 934% and it is more than twice as abundant as water vapor,23 times as abundant as carbon dioxide, and more than 500 times as abundant as neon. Argon is the most abundant noble gas in Earths crust, comprising 0. 00015% of the crust, nearly all of the argon in Earths atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earths crust. In the universe, argon-36 is by far the most common argon isotope, the name argon is derived from the Greek word ἀργόν, neuter singular form of ἀργός meaning lazy or inactive, as a reference to the fact that the element undergoes almost no chemical reactions. The complete octet in the atomic shell makes argon stable. Its triple point temperature of 83.8058 K is a fixed point in the International Temperature Scale of 1990. Argon is produced industrially by the distillation of liquid air. Argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes, Argon makes a distinctive blue-green gas laser. Argon is also used in fluorescent glow starters, Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas, Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature. Although argon is a gas, it can form some compounds under extreme conditions. Argon fluorohydride, a compound of argon with fluorine and hydrogen that is stable below 17 K, has been demonstrated. Although the neutral ground-state chemical compounds of argon are presently limited to HArF, ions, such as ArH+, and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable but have not yet been synthesized, Argon was suspected to be a component of air by Henry Cavendish in 1785. Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water and they had determined that nitrogen produced from chemical compounds was 0. 5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months and they concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall, each observed new lines in the color spectrum of air that did not match known elements
21.
Helium
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Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and its boiling point is the lowest among all the elements. Its abundance is similar to figure in the Sun and in Jupiter. This is due to the high nuclear binding energy of helium-4 with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of nuclear fusion and radioactive decay. Most helium in the universe is helium-4, and is believed to have formed during the Big Bang. Large amounts of new helium are being created by fusion of hydrogen in stars. Helium is named for the Greek god of the Sun, Helios and it was first detected as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by French astronomer Jules Janssen. Janssen is jointly credited with detecting the element along with Norman Lockyer, Janssen observed during the solar eclipse of 1868 while Lockyer observed from Britain. Lockyer was the first to propose that the line was due to a new element, the formal discovery of the element was made in 1895 by two Swedish chemists, Per Teodor Cleve and Nils Abraham Langlet, who found helium emanating from the uranium ore cleveite. In 1903, large reserves of helium were found in gas fields in parts of the United States. Liquid helium is used in cryogenics, particularly in the cooling of superconducting magnets, a well-known but minor use is as a lifting gas in balloons and airships. As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre, on Earth it is relatively rare—5.2 ppm by volume in the atmosphere. Most terrestrial helium present today is created by the radioactive decay of heavy radioactive elements. Previously, terrestrial helium—a non-renewable resource, because once released into the atmosphere it readily escapes into space—was thought to be in short supply. The first evidence of helium was observed on August 18,1868, the line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. This line was assumed to be sodium. He concluded that it was caused by an element in the Sun unknown on Earth, Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος
22.
Gas metal arc welding
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Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the process from contaminants in the air. The process can be semi-automatic or automatic, a constant voltage, direct current power source is most commonly used with GMAW, but constant current systems, as well as alternating current, can be used. Originally developed for welding aluminium and other materials in the 1940s. The cost of inert gas limited its use in steels until several years later, further developments during the 1950s and 1960s gave the process more versatility and as a result, it became a highly used industrial process. Today, GMAW is the most common industrial welding process, preferred for its versatility, speed, unlike welding processes that do not employ a shielding gas, such as shielded metal arc welding, it is rarely used outdoors or in other areas of air volatility. A related process, flux cored arc welding, often does not use a shielding gas, the principles of gas metal arc welding began to be understood in the early 19th century, after Humphry Davy discovered the short pulsed electric arcs in 1800. Vasily Petrov independently produced the electric arc in 1802. It was not until the 1880s that the technology developed with the aim of industrial usage. At first, carbon electrodes were used in arc welding. By 1890, metal electrodes had been invented by Nikolay Slavyanov, in 1920, an early predecessor of GMAW was invented by P. O. Nobel of General Electric. It used an electrode wire and direct current, and used arc voltage to regulate the feed rate. It did not use a gas to protect the weld. In 1926 another forerunner of GMAW was released, but it was not suitable for practical use, in 1948, GMAW was developed by the Battelle Memorial Institute. It used a smaller diameter electrode and a constant voltage power source developed by H. E. Kennedy and it offered a high deposition rate, but the high cost of inert gases limited its use to non-ferrous materials and prevented cost savings. In 1953, the use of carbon dioxide as an atmosphere was developed. It quickly became the most popular GMAW variation, the spray-arc transfer variation was developed in the early 1960s, when experimenters added small amounts of oxygen to inert gases. More recently, pulsed current has been applied, giving rise to a new method called the pulsed spray-arc variation, GMAW is one of the most popular welding methods, especially in industrial environments. It is used extensively by the metal industry and, by extension
23.
Flux-cored arc welding
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Flux-cored arc welding is a semi-automatic or automatic arc welding process. FCAW requires a continuously-fed consumable tubular electrode containing a flux and a constant-voltage or, less commonly, the process is widely used in construction because of its high welding speed and portability. FCAW was first developed in the early 1950s as an alternative to shielded metal arc welding, the advantage of FCAW over SMAW is that the use of the stick electrodes used in SMAW is unnecessary. This helped FCAW to overcome many of the associated with SMAW. One type of FCAW requires no shielding gas and this is made possible by the flux core in the tubular consumable electrode. However, this contains more than just flux, it also contains various ingredients that when exposed to the high temperatures of welding generate a shielding gas for protecting the arc. This type of FCAW is attractive because it is portable and generally has good penetration into the base metal, also, windy conditions need not be considered. Some disadvantages are that this process can produce excessive, noxious smoke, As with all welding processes, operator skill is a major factor as improper electrode manipulation or machine setup can cause porosity. Another type of FCAW uses a gas that must be supplied by an external supply. This is known informally as dual shield welding and this type of FCAW was developed primarily for welding structural steels. In fact, since it both a flux-cored electrode and an external shielding gas, one might say that it is a combination of gas metal. This particular style of FCAW is preferable for welding thicker and out-of-position metals, the slag created by the flux is also easy to remove. In practice it also allows a production rate, since the operator does not need to stop periodically to fetch a new electrode. However, like GMAW, it cannot be used in an environment as the loss of the shielding gas from air flow will produce porosity in the weld. The amount of smoke generated can far exceed that of SMAW, GMAW, changing filler metals requires changing an entire spool. This can be slow and difficult as compared to changing filler metal for SMAW or GTAW, american Welding Society, Welding Handbook, Vol 2 Flux Cored Welding. New York City, John Wiley & Sons, INC,2002, solid Wire Versus Flux-Cored Wire - When to Use Them and Why. Miller Electric Mfg. Co.13 Sep 2006 <http, //www. millerwelds. com/education/articles/article62. html>
24.
Submerged arc welding
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Submerged arc welding is a common arc welding process. The first patent on the welding process was taken out in 1935. Originally developed and patented by Jones, Kennedy and Rothermund, the process requires a continuously fed consumable solid or tubular electrode, when molten, the flux becomes conductive, and provides a current path between the electrode and the work. SAW is normally operated in the automatic or mechanized mode, however, the process is normally limited to the flat or horizontal-fillet welding positions. Deposition rates approaching 45 kg/h have been reported — this compares to ~5 kg/h for shielded arc welding. Although currents ranging from 300 to 2000 A are commonly utilized, single or multiple electrode wire variations of the process exist. SAW strip-cladding utilizes a flat strip electrode, DC or AC power can be used, and combinations of DC and AC are common on multiple electrode systems. Constant voltage welding power supplies are most commonly used, however and it feeds flux and filler metal to the welding joint. It stores the flux and controls the rate of deposition on the welding joint. The granulated flux shields and thus protects molten weld from atmospheric contamination, the flux cleans weld metal and can also modify its chemical composition. The flux is granulated to a definite size and it may be of fused, bonded or mechanically mixed type. The flux may consist of fluorides of calcium and oxides of calcium, magnesium, silicon, aluminium, alloying elements may be added as per requirements. Substances evolving large amount of gases during welding are never mixed with the flux, flux with fine and coarse particle sizes are recommended for welding heavier and smaller thickness respectively. SAW filler material usually is a wire as well as other special forms. This wire normally has a thickness of 1.6 mm to 6 mm, in certain circumstances, twisted wire can be used to give the arc an oscillating movement. This helps fuse the toe of the weld to the base metal, the electrode composition depends upon the material being welded. Alloying elements may be added in the electrodes, electrodes are available to weld mild steels, high carbon steels, low and special alloy steels, stainless steel and some of the nonferrous of copper and nickel. Electrodes are generally copper coated to prevent rusting and to increase their electrical conductivity, electrodes are available in straight lengths and coils
25.
Electroslag welding
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Electroslag welding is a highly productive, single pass welding process for thick materials in a vertical or close to vertical position. Is similar to welding, but the main difference is the arc starts in a different location. An electric arc is struck by wire that is fed into the desired weld location. Additional flux is added until the slag, reaching the tip of the electrode. The wire and tube then move up along the workpiece while a copper retaining shoe that was put into place before starting is used to keep the weld between the plates that are being welded. Electroslag welding is used mainly to low carbon steel plates and/or sections that are very thick. It can also be used on structural steel if certain precautions are observed and this process uses a direct current voltage usually ranging from about 600 A and 40-50 V, higher currents are needed for thicker materials. Because the arc is extinguished, this is not an arc process, the process was patented by Robert K Hopkins in the United States in February 1940 and developed and refined at the Paton Institute, Kiev, USSR during the 1940s. The Paton method was released to the west at the Bruxelles Trade Fair of 1950, the first widespread use in the U. S. was in 1959, by General Motors Electromotive Division, Chicago, for the fabrication of traction motor frames. In 1968 Hobart Brothers of Troy, Ohio, released a range of machines for use in the shipbuilding, bridge construction, between the late 1960s and late 1980s, it is estimated that in California alone over a million stiffeners were welded with the electroslag welding process. The Northridge earthquake and the Loma Prieta earthquakes provided a real world test to all of the welding processes. Not one failure or one crack propagation was initiated in any of the hundreds-of-thousands of welds made on continuity plates welded with the Electroslag welding process, the FHWA commissioned research from universities and industry and Narrow Gap Improved Electro Slag Welding was developed as a replacement. The FHWA moratorium was rescinded in 2000, benefits of the process include its high metal deposition rates—it can lay metal at a rate between 15 and 20 kg per hour per electrode—and its ability to weld thick materials. Many welding processes require more than one pass for welding thick workpieces, the process is also very efficient, since joint preparation and materials handling are minimized while filler metal utilization is high. The process is safe and clean, with no arc flash. Electroslag welding easily lends itself to mechanization, thus reducing the requirement for skilled manual welders, one electrode is commonly used to make welds on materials with a thickness of 25 to 75 mm, and thicker pieces generally require more electrodes. The maximum workpiece thickness that has ever been successfully welded was a 0.91 m piece that required the use of six electrodes to complete. Cary, Howard B. and Scott C, upper Saddle River, New Jersey, Pearson Education
26.
Electric resistance welding
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Small pools of molten metal are formed at the point of most electrical resistance as an electrical current is passed through the metal. In general, resistance welding methods are efficient and cause pollution, but their applications are limited to relatively thin materials. Spot welding is a resistance welding method used to two or more overlapping metal sheets, studs, projections, electrical wiring hangers, some heat exchanger fins. Usually power sources and welding equipment are sized to the specific thickness, the thickness is limited by the output of the welding power source and thus the equipment range due to the current required for each application. Care is taken to eliminate contaminants between the faying surfaces, usually, two copper electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. When the current is passed through the electrodes to the sheets, as the heat dissipates throughout the workpiece in less than a second the molten or plastic state grows to meet the welding tips. When the current is stopped the copper tips cool the spot weld, the water cooled copper electrodes remove the surface heat quickly, accelerating the solidification of the metal, since copper is an excellent conductor. Resistance spot welding typically employs electrical power in the form of current, alternating current, medium frequency half-wave direct current. This burst of molten metal is called expulsion, and when this occurs the metal will be thinner and have less strength than a weld with no expulsion, the common method of checking a welds quality is a peel test. An alternative test is the tensile test, which is much more difficult to perform. Because both tests are destructive in nature, non-destructive methods such as ultrasound evaluation are in states of early adoption by many OEMs. The advantages of the method include efficient energy use, limited workpiece deformation, high rates, easy automation. When high strength in shear is needed, spot welding is used in preference to more costly mechanical fastening and it is used extensively in the automotive industry— cars can have several thousand spot welds. A specialized process, called shot welding, can be used to weld stainless steel. There are three types of resistance welding bonds, solid state, fusion, and reflow braze. There is little melting and minimum grain growth, but a definite bond, thus the materials actually bond while still in the solid state. The bonded materials typically exhibit excellent shear and tensile strength, in a fusion bond, either similar or dissimilar materials with similar grain structures are heated to the melting point of both. The subsequent cooling and combination of the forms a “nugget” alloy of the two materials with larger grain growth
27.
Energy source
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Energy development is a field of endeavor focused on making available sufficient primary energy sources and secondary energy forms to meet the needs of society. These endeavors encompass those which provide for the production of conventional, alternative and renewable sources of energy, Energy conservation and efficiency measures reduce the effect of energy development, and can have benefits to society with changes in economic cost and with changes in the environmental issues. Contemporary industrial societies use primary and secondary sources for transportation. Also, large populations have various generation and delivery services for energy distribution. This energy is used by people who can afford the cost to live under various climatic conditions through the use of heating, ventilation, and/or air conditioning. Level of use of energy sources differs across societies, along with the convenience, levels of traffic congestion, pollution sources. Thousands of people in society are employed in the energy industry, the conventional industry comprises the petroleum industry the gas industry, the electrical power industry the coal industry, and the nuclear power industry. New energy industries include the energy industry, comprising alternative and sustainable manufacture, distribution. Illustrative of this can be the emanations from the sun, which with its nuclear fusion is the most important energy source for the Earth and which provides its energy in the form of radiation. The natural elements of the world exist in forms that can be converted into usable energy and are resources from which society can obtain energy to produce heat, light. According to their nature, the plants can be classified into, Primary, They are found in nature, wind, water, solar, wood, coal, oil. Secondary, Are those obtained from primary sources, electricity. The principle stated by Antoine Lavoisier on the conservation of matter applies to energy development, thus any energy production is actually a recovery transformation of the forms of energy whose origin is that of the universe. This material itself constitutes a form of energy, called mass energy, fossil fuel sources burn coal or hydrocarbon fuels, which are the remains of the decomposition of plants and animals. There are three types of fossil fuels, coal, petroleum, and natural gas. Another fossil fuel, liquefied gas, is principally derived from the production of natural gas. Heat from burning fuel is used either directly for space heating and process heating, or converted to mechanical energy for vehicles, industrial processes. Fossil energy is from recovered fossils and are originated in degradated products of dead plants and these fossil fuels are based on the carbon cycle and thus allow stored energy to be recycled today
28.
Fire
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Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition, at a certain point in the combustion reaction, called the ignition point, flames are produced. The flame is the portion of the fire. Flames consist primarily of carbon dioxide, water vapor, oxygen and nitrogen, if hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, and any impurities outside, the color of the flame, Fire in its most common form can result in conflagration, which has the potential to cause physical damage through burning. Fire is an important process that affects ecological systems around the globe, the positive effects of fire include stimulating growth and maintaining various ecological systems. The negative effects of fire hazard to life and property, atmospheric pollution. If fire removes protective vegetation, heavy rainfall may lead to an increase in soil erosion by water and this is commonly called the fire tetrahedron. Fire cannot exist without all of elements in place and in the right proportions. For example, a liquid will start burning only if the fuel. Some fuel-oxygen mixes may require a catalyst, a substance that is not consumed, when added, in any chemical reaction during combustion, but which enables the reactants to combust more readily. Without gravity, a fire rapidly surrounds itself with its own products and non-oxidizing gases from the air. Because of this, the risk of fire in a spacecraft is small when it is coasting in inertial flight, of course, this does not apply if oxygen is supplied to the fire by some process other than thermal convection. Fire can be extinguished by removing any one of the elements of the fire tetrahedron, consider a natural gas flame, such as from a stovetop burner. In contrast, fire is intensified by increasing the rate of combustion. In many cases, such as the burning of organic matter, for wood, or the incomplete combustion of gas. This light has a continuous spectrum, complete combustion of gas has a dim blue color due to the emission of single-wavelength radiation from various electron transitions in the excited molecules formed in the flame. Usually oxygen is involved, but hydrogen burning in chlorine produces a flame
29.
Electric arc
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An electric arc or arc discharge is an electrical breakdown of a gas that produces an ongoing electrical discharge. The current through a normally nonconductive medium such as air produces a plasma, an arc discharge is characterized by a lower voltage than a glow discharge, and it relies on thermionic emission of electrons from the electrodes supporting the arc. An archaic term is voltaic arc, as used in the voltaic arc lamp. The phenomenon is believed to be first described by Sir Humphry Davy in an 1801 paper published in William Nicholsons Journal of Natural Philosophy, Chemistry and the Arts. However, Davys description was not an arc as this phenomenon is considered by the modern science, This is evidently the description, not of an arc. For the essence of an arc is that it should be continuous, in the same year Davy publicly demonstrated the effect, before the Royal Society, by transmitting an electric current through two touching carbon rods and then pulling them a short distance apart. The demonstration produced a feeble arc, not readily distinguished from a sustained spark, the Society subscribed for a more powerful battery of 1000 plates and in 1808 he demonstrated the large-scale arc. He is credited with naming the arc and he called it an arc because it assumes the shape of an upward bow when the distance between the electrodes is not small. This is due to the buoyant force on the hot gas, in the late nineteenth century, electric arc lighting was in wide use for public lighting. The tendency of electric arcs to flicker and hiss was a major problem, in 1895, Hertha Marks Ayrton wrote a series of articles for the Electrician, explaining that these phenomena were the result of oxygen coming into contact with the carbon rods used to create the arc. In 1899, she was the first woman ever to read her own paper before the Institution of Electrical Engineers and her paper was entitled The Hissing of the Electric Arc. Shortly thereafter, Ayrton was elected the first female member of the IEE and she petitioned to present a paper before the Royal Society but was not allowed because of her sex, and The Mechanism of the Electric Arc was read by John Perry in her stead in 1901. An electric arc is the form of discharge with the highest current density. The maximum current through an arc is limited only by the external circuit, an arc between two electrodes can be initiated by ionization and glow discharge, as the current through the electrodes is increased. The breakdown voltage of the gap is a function of the pressure. When an arc starts, its voltage is much less than a glow discharge. An arc in gases near atmospheric pressure is characterized by light emission, high current density. A drawn arc can be initiated by two electrodes initially in contact and drawn apart, this can initiate an arc without the high-voltage glow discharge
30.
Laser
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A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term laser originated as an acronym for light amplification by stimulated emission of radiation, the first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light coherently, spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances, Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i. e. they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond, Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have very low divergence in order to concentrate their power at a great distance. Temporal coherence implies a polarized wave at a single frequency whose phase is correlated over a great distance along the beam. A beam produced by a thermal or other incoherent light source has an amplitude and phase that vary randomly with respect to time and position. Lasers are characterized according to their wavelength in a vacuum, most single wavelength lasers actually produce radiation in several modes having slightly differing frequencies, often not in a single polarization. Although temporal coherence implies monochromaticity, there are lasers that emit a broad spectrum of light or emit different wavelengths of light simultaneously, there are some lasers that are not single spatial mode and consequently have light beams that diverge more than is required by the diffraction limit. However, all devices are classified as lasers based on their method of producing light. Lasers are employed in applications where light of the spatial or temporal coherence could not be produced using simpler technologies. The word laser started as an acronym for light amplification by stimulated emission of radiation, in the early technical literature, especially at Bell Telephone Laboratories, the laser was called an optical maser, this term is now obsolete. A laser that produces light by itself is technically an optical rather than an optical amplifier as suggested by the acronym. It has been noted that the acronym LOSER, for light oscillation by stimulated emission of radiation. With the widespread use of the acronym as a common noun, optical amplifiers have come to be referred to as laser amplifiers. The back-formed verb to lase is frequently used in the field, meaning to produce light, especially in reference to the gain medium of a laser. Further use of the laser and maser in an extended sense, not referring to laser technology or devices, can be seen in usages such as astrophysical maser
31.
Electron beam welding
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Compare the main article Elektronenstrahl-Materialbearbeitung within the German Wikipedia. Electron beam welding is a welding process in which a beam of high-velocity electrons is applied to two materials to be joined. The workpieces melt and flow together as the energy of the electrons is transformed into heat upon impact. EBW is often performed under vacuum conditions to prevent dissipation of the electron beam, Electron beam welding was developed by the German physicist Karl-Heinz Steigerwald, who was at the time working on various electron beam applications. Steigerwald conceived and developed the first practical electron beam welding machine, american inventor James T. Russell has also been credited with designing and building the first electron-beam welder. Electrons are elementary particles possessing a mass m =9.1 · 10−31 kg and they exist either bound to an atomic nucleus, as conduction electrons in the atomic lattice of metals, or as free electrons in vacuum. Free electrons in vacuum can be accelerated, with their paths controlled by electric and magnetic fields, in this way narrow beams of electrons carrying high kinetic energy can be formed, which upon collision with atoms in solids transform their kinetic energy into heat. Electron beam welding provides excellent welding conditions because it involves, Strong electric fields, thus, the electron beam can carry high power, equal to the product of beam current and accelerating voltage. By increasing the current and the accelerating voltage, the beam power can be increased to practically any desired value. Using magnetic lenses, by which the beam can be shaped into a narrow cone and this allows for a very high surface power density on the surface to be welded. Values of power density in the crossover of the beam can be as high as 104 –106 W/mm2, shallow penetration depths in the order of hundredths of a millimeter. This allows for a high volumetric power density, which can reach values of the order 105 –107 W/mm3. Consequently, the temperature in this volume increases extremely rapidly,108 –1010 K/s, the effectiveness of the electron beam depends on many factors. The most important are the properties of the materials to be welded. Electron beam welding can be so intense that loss of material due to evaporation or boiling during the process must be taken into account when welding, at lower values of surface power density the loss of material by evaporation is negligible for most metals, which is favorable for welding. At higher power density, the affected by the beam can totally evaporate in a very short time. Cathode - the source of free electrons Conduction electrons move in a lattice of metals with velocities distributed according to Gausss law. They cannot leave the metal unless their kinetic energy is higher than the barrier at the metal surface
32.
Ultrasound
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Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is no different from normal sound in its physical properties and this limit varies from person to person and is approximately 20 kilohertz in healthy, young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz, Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances, Ultrasound imaging or sonography is often used in medicine. In the nondestructive testing of products and structures, ultrasound is used to detect invisible flaws, industrially, ultrasound is used for cleaning, mixing, and to accelerate chemical processes. Animals such as bats and porpoises use ultrasound for locating prey, scientist are also studying ultrasound using graphene diaphragms as a method of communication. Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound and not vision. The first technological application of ultrasound was an attempt to detect submarines by Paul Langevin in 1917, the piezoelectric effect, discovered by Jacques and Pierre Curie in 1880, was useful in transducers to generate and detect ultrasonic waves in air and water. Ultrasound is defined by the American National Standards Institute as sound at frequencies greater than 20 kHz, in air at atmospheric pressure ultrasonic waves have wavelengths of 1.9 cm or less. The upper frequency limit in humans is due to limitations of the middle ear, auditory sensation can occur if high‐intensity ultrasound is fed directly into the human skull and reaches the cochlea through bone conduction, without passing through the middle ear. Children can hear some high-pitched sounds that older adults cannot hear, the Mosquito is an electronic device that uses a high pitched frequency to deter loitering by young people. Bats use a variety of ultrasonic ranging techniques to detect their prey and they can detect frequencies beyond 100 kHz, possibly up to 200 kHz. Many insects have good hearing and most of these are nocturnal insects listening for echolocating bats. This includes many groups of moths, beetles, praying mantids, upon hearing a bat, some insects will make evasive manoeuvres to escape being caught. Ultrasonic frequencies trigger an action in the noctuid moth that cause it to drop slightly in its flight to evade attack. Tiger moths also emit clicks which may disturb bats echolocation, dogs and cats hearing range extends into the ultrasound, the top end of a dogs hearing range is about 45 kHz, while a cats is 64 kHz. The wild ancestors of cats and dogs evolved this higher hearing range to hear sounds made by their preferred prey. A dog whistle is a whistle that emits ultrasound, used for training and calling dogs, porpoises have the highest known upper hearing limit, at around 160 kHz
33.
Underwater welding
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Hyperbaric welding is the process of welding at elevated pressures, normally underwater. Hyperbaric welding can either take place wet in the water itself or dry inside a specially constructed positive pressure enclosure and it is predominantly referred to as hyperbaric welding when used in a dry environment, and underwater welding when in a wet environment. The applications of hyperbaric welding are diverse—it is often used to ships, offshore oil platforms. Steel is the most common material welded and this improved environmental control leads directly to improved process performance and a generally much higher quality weld than a comparative wet weld. Thus, when a high quality weld is required, dry hyperbaric welding is normally utilized. Research into using dry hyperbaric welding at depths of up to 1,000 metres is ongoing, underwater hyperbaric welding was invented by the Russian metallurgist Konstantin Khrenov in 1932. Welding processes have become important in almost all manufacturing industries. It is also an important technique for emergency repairs which allow the structure to be safely transported to dry facilities for permanent repair or scrapping. Underwater welding is applied in both inland and offshore environments, though seasonal weather inhibits offshore underwater welding during winter, in either location, surface supplied air is the most common diving method for underwater welders. Dry hyperbaric welding involves the weld being performed at raised pressure in a filled with a gas mixture sealed around the structure being welded. Gas tungsten arc welding is most commonly used, the degradation is associated with physical changes of the arc behaviour as the gas flow regime around the arc changes and the arc roots contract and become more mobile. Of note is a increase in arc voltage which is associated with the increase in pressure. Overall a degradation in capability and efficiency results as the pressure increases, wet underwater welding directly exposes the diver and electrode to the water and surrounding elements. Divers usually use around 300–400 amps of current to power their electrode. This practice commonly uses a variation of shielded metal arc welding, employing a waterproof electrode, other processes that are used include flux-cored arc welding and friction welding. In each of these cases, the power supply is connected to the welding equipment through cables and hoses. The process is limited to low carbon equivalent steels, especially at greater depths. Wet welding with an electrode is done with similar equipment to that used for dry welding
34.
Outer space
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Outer space or just space, is the void that exists between celestial bodies, including Earth. The baseline temperature, as set by the radiation from the Big Bang, is 2.7 kelvins. In most galaxies, observations provide evidence that 90% of the mass is in a form, called dark matter. Data indicates that the majority of the mass-energy in the universe is a poorly understood vacuum energy of space which astronomers label dark energy. Intergalactic space takes up most of the volume of the Universe, there is no firm boundary where outer space starts. However the Kármán line, at an altitude of 100 km above sea level, is used as the start of outer space in space treaties. The framework for international law was established by the Outer Space Treaty. This treaty precludes any claims of sovereignty and permits all states to freely explore outer space. Despite the drafting of UN resolutions for the uses of outer space. Humans began the exploration of space during the 20th century with the advent of high-altitude balloon flights. Earth orbit was first achieved by Yuri Gagarin of the Soviet Union in 1961, due to the high cost of getting into space, manned spaceflight has been limited to low Earth orbit and the Moon. Outer space represents an environment for human exploration because of the dual hazards of vacuum. Microgravity also has an effect on human physiology that causes both muscle atrophy and bone loss. In addition to health and environmental issues, the economic cost of putting objects, including humans. In 350 BCE, Greek philosopher Aristotle suggested that nature abhors a vacuum and this concept built upon a 5th-century BCE ontological argument by the Greek philosopher Parmenides, who denied the possible existence of a void in space. Based on this idea that a vacuum could not exist, in the West it was held for many centuries that space could not be empty. As late as the 17th century, the French philosopher René Descartes argued that the entirety of space must be filled, in ancient China, there were various schools of thought concerning the nature of the heavens, some of which bear a resemblance to the modern understanding. In the 2nd century, astronomer Zhang Heng became convinced that space must be infinite, extending well beyond the mechanism that supported the Sun, the surviving books of the Hsüan Yeh school said that the heavens were boundless, empty and void of substance
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Ultraviolet radiation
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Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is also produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan, freckling and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects, mammals, and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV also allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established. The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann
36.
Blacksmith
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A blacksmith is a metalsmith who creates objects from wrought iron or steel by forging the metal, using tools to hammer, bend, and cut. Blacksmiths produce objects such as gates, grilles, railings, light fixtures, furniture, sculpture, tools, agricultural implements, decorative and religious items, cooking utensils and weapons. The black in blacksmith refers to the black fire scale, a layer of oxides that forms on the surface of the metal during heating. The origin of smith is debated, it may come from the old English word smythe meaning to strike or it may have originated from the Proto-German smithaz meaning skilled worker. Blacksmiths work by heating pieces of iron or steel until the metal becomes soft enough for shaping with hand tools, such as a hammer, anvil. Heating generally takes place in a forge fueled by propane, natural gas, coal, charcoal, some modern blacksmiths may also employ an oxyacetylene or similar blowtorch for more localized heating. Induction heating methods are gaining popularity among modern blacksmiths, color is important for indicating the temperature and workability of the metal. As iron heats to higher temperatures, it first glows red, then orange, yellow, the ideal heat for most forging is the bright yellow-orange color that indicates forging heat. Because they must be able to see the color of the metal, some blacksmiths work in dim, low-light conditions. The key is to have consistent lighting, but not too bright, the techniques of smithing can be roughly divided into forging, welding, heat-treating, and finishing. Forging—the process smiths use to shape metal by hammering—differs from machining in that forging does not remove material, instead, the smith hammers the iron into shape. Even punching and cutting operations by smiths usually re-arrange metal around the hole, drawing lengthens the metal by reducing one or both of the other two dimensions. As the depth is reduced, or the width narrowed, the piece is lengthened or drawn out, as an example of drawing, a smith making a chisel might flatten a square bar of steel, lengthening the metal, reducing its depth but keeping its width consistent. Drawing does not have to be uniform, a taper can result as in making a wedge or a woodworking chisel blade. If tapered in two dimensions, a point results, drawing can be accomplished with a variety of tools and methods. Two typical methods using only hammer and anvil would be hammering on the anvil horn, another method for drawing is to use a tool called a fuller, or the peen of the hammer, to hasten the drawing out of a thick piece of metal. Fullering consists of hammering a series of indentations with corresponding ridges, the resulting effect looks somewhat like waves along the top of the piece. Then the smith turns the hammer over to use the face to hammer the tops of the ridges down level with the bottoms of the indentations
37.
Arc welding
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Arc welding is a process that is used to join metal to metal by using electricity to create enough heat to melt metal, and the melted metals when cool result in a binding of the metals. It is a type of welding that uses a power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct or alternating current, and consumable or non-consumable electrodes, the welding region is usually protected by some type of shielding gas, vapor, or slag. Arc welding processes may be manual, semi-automatic, or fully automated, first developed in the late part of the 19th century, arc welding became commercially important in shipbuilding during the Second World War. Today it remains an important process for the fabrication of steel structures and vehicles, to supply the electrical energy necessary for arc welding processes, a number of different power supplies can be used. The most common classification is constant current power supplies and constant voltage power supplies, in arc welding, the voltage is directly related to the length of the arc, and the current is related to the amount of heat input. This is important because in manual welding, it can be difficult to hold the electrode perfectly steady, and as a result, the arc length and thus voltage tend to fluctuate. In these processes, arc length is constant, since any fluctuation in the distance between the wire and the base material is quickly rectified by a large change in current. The direction of current used in arc welding also plays an important role in welding, consumable electrode processes such as shielded metal arc welding and gas metal arc welding generally use direct current, but the electrode can be charged either positively or negatively. In welding, the positively charged anode will have a greater concentration and, as a result. If the electrode is charged, it will melt more quickly, increasing weld penetration. Alternatively, a negatively charged electrode results in more shallow welds, non-consumable electrode processes, such as gas tungsten arc welding, can use either type of direct current, as well as alternating current. Alternating current rapidly moves between two, resulting in medium-penetration welds. Duty cycle is an equipment specification which defines the number of minutes, within a 10-minute period. For example, an 80 A welder with a 60% duty cycle must be rested for at least 4 minutes after 6 minutes of continuous welding, failure to observe duty cycle limitations could damage the welder. Commercial- or professional-grade welders typically have a 100% duty cycle, one of the most common types of arc welding is shielded metal arc welding, which is also known as manual metal arc welding or stick welding. An electric current is used to strike an arc between the material and a consumable electrode rod or stick. The electrode core itself acts as filler material, making a separate filler unnecessary, the process is very versatile, requiring little operator training and inexpensive equipment
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Oxy-fuel welding and cutting
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Oxy-fuel welding and oxy-fuel cutting are processes that use fuel gases and oxygen to weld and cut metals, respectively. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903, pure oxygen, instead of air, is used to increase the flame temperature to allow localized melting of the workpiece material in a room environment. In recent decades it has been obsolesced in almost all industrial uses due to various arc welding methods offering more consistent mechanical weld properties, gas welding is still used for metal-based artwork and in smaller home based shops, as well as situations where accessing electricity would present difficulties. In oxy-fuel welding, a torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal, the molten pool is generally supplied with additional metal called filler. Filler material depends upon the metals to be welded, in oxy-fuel cutting, a torch is used to heat metal to its kindling temperature. A stream of oxygen is then trained on the metal, burning it into an oxide that flows out of the kerf as slag. Torches that do not mix fuel with oxygen are not considered oxy-fuel torches, most metals cannot be melted with a single-tank torch. Consequently, single-tank torches are typically suitable for soldering and brazing, oxy-gas torches are or have been used for, Welding metal, see below. Depositing metal to build up a surface, as in hardfacing, also, oxy-hydrogen flames are used, in stone working for flaming where the stone is heated and a top layer crackles and breaks. A steel circular brush is attached to a grinder and used to remove the first layer leaving behind a bumpy surface similar to hammered bronze. In the glass industry for fire polishing, in jewelry production for water welding using a water torch. in automotive repair, removing a seized bolt. Formerly, to heat lumps of quicklime to obtain a white light called limelight. Formerly, in works, as platinum is fusible only in the oxyhydrogen flame. The apparatus used in gas welding consists basically of an oxygen source and this sort of torch can also be used for soldering and brazing. The cylinders are carried in a special wheeled trolley. There have been examples of oxyhydrogen cutting sets with small gas cylinders worn on the back in a backpack harness, for rescue work. There are also examples of pressurized liquid fuel cutting torches, usually using gasoline and these are used for their increased portability
39.
Laser beam welding
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Laser beam welding is a welding technique used to join multiple pieces of metal through the use of a laser. The beam provides a heat source, allowing for narrow, deep welds. The process is used in high volume applications using automation. It is based on keyhole or penetration mode welding, like electron beam welding, laser beam welding has high power density resulting in small heat-affected zones and high heating and cooling rates. The spot size of the laser can vary between 0.2 mm and 13 mm, though only smaller sizes are used for welding, millisecond-long pulses are used to weld thin materials such as razor blades while continuous laser systems are employed for deep welds. LBW is a process, capable of welding carbon steels, HSLA steels, stainless steel, aluminum. Due to high cooling rates, cracking is a concern when welding high-carbon steels, the weld quality is high, similar to that of electron beam welding. The speed of welding is proportional to the amount of power supplied but also depends on the type, the high power capability of gas lasers make them especially suitable for high volume applications. LBW is particularly dominant in the automotive industry, weld quality tends to be higher as well, since the potential for undercutting is reduced. Although laser beam welding can be accomplished by hand, most systems are automated use a system of computer aided manufacturing based on computer aided designs, laser welding can also be coupled with milling to form a finished part. Recently the RepRap project, which worked on fused filament fabrication. Such systems have been characterized and can be used in a wide scale of applications while reducing conventional manufacturing costs. The two types of commonly used are solid-state lasers and gas lasers. The first type uses one of several media, including synthetic ruby, neodymium in glass. Gas lasers use mixtures of such as helium, nitrogen. Regardless of type, however, when the medium is excited, it emits photons, Nd, YAG lasers can operate in both pulsed and continuous mode, but the other types are limited to pulsed mode. The original and still popular solid-state design is a single crystal shaped as a rod approximately 20 mm in diameter and 200 mm long, and this rod is surrounded by a flash tube containing xenon or krypton. When flashed, a pulse of light lasting about two milliseconds is emitted by the laser, disk shaped crystals are growing in popularity in the industry, and flashlamps are giving way to diodes due to their high efficiency
40.
Magnetic pulse welding
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Magnetic pulse welding is a solid state welding process that uses magnetic forces to weld two workpieces together. The welding mechanism is most similar to that of explosion welding, magnetic pulse welding started in the early 1970s, when the automotive industry began to use solid state welding. The biggest advantage using magnetic pulse welding is that the formation of brittle intermetallic phases is avoided, therefore, dissimilar metals can be welded, which cannot be joined by fusion welding. With magnetic pulse welding high quality welds in similar and dissimilar metals can be made in microseconds without the need for shielding gases or welding consumables. Magnetic pulse welding is based on a very short electromagnetic pulse, the pulsed current with a very high amplitude and frequency produces a high-density magnetic field, which creates an eddy current in one of the work pieces. During magnetic pulse welding a high plastic deformation is developed along with high shear strain and oxide disruption thanks to the jet and this leads to solid state weld due to the microstructure refinement, dislocation cells, slip bends, micro twins and local recrystallization. In order to get a strong weld, several conditions have to be reached, Jetting condition, high pressure regime, the impact velocity has to be sufficient to obtain a hydrodynamic regime, otherwise the parts will only be crimped or formed. No fusion during the collision, If the pressure is too high and this can cause a weak weld. Allows welding of designs which with other processes are challenging or not possible, high-speed pulse lasts from 10 to 100 µs, the only time limitation is loading and unloading and capacitor charge time. High repeat Suited to mass-production, typically 1-5 million welds per year, green process, no smoke, no radiation and no extraction equipment required. Mechanical strength of the joint is stronger than that of the parent material, high precision obtainable by adjustment of magnetic field. No corrosion development in the welding area, the Electromagnetic Pulse Technology, Forming, Welding, Crimping and Cutting by R. Schäfer, P. A. Pasquale and S. W. Kallee Automotive Applications of Electromagnetic Pulse Technology by S. W. Kallee, R. Schäfer, pasquale New materials, processes, and methods technology by Mel M. Schwartz
41.
Friction stir welding
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Friction stir welding is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material. Heat is generated by friction between the tool and the workpiece material, which leads to a softened region near the FSW tool. It is primarily used on wrought or extruded aluminium and particularly for structures which need very high weld strength and it was invented and experimentally proven at The Welding Institute in the UK in December 1991. TWI held patents on the process, the first being the most descriptive, the probe is slightly shorter than the weld depth required, with the tool shoulder riding atop the work surface. After a short time, the tool is moved forward along the joint line at the pre-set welding speed. Frictional heat is generated between the wear-resistant tool and the work pieces and this heat, along with that generated by the mechanical mixing process and the adiabatic heat within the material, cause the stirred materials to soften without melting. As the tool is moved forward, a profile on the probe forces plasticised material from the leading face to the rear. This process of the tool traversing along the line in a plasticised tubular shaft of metal results in severe solid state deformation involving dynamic recrystallization of the base material. The solid-state nature of the FSW process, combined with its unusual shape and asymmetric speed profile. The microstructure can be broken up into the following zones, The stir zone is a region of heavily deformed material that roughly corresponds to the location of the pin during welding. The grains within the zone are roughly equiaxed and often an order of magnitude smaller than the grains in the parent material. A unique feature of the zone is the common occurrence of several concentric rings which has been referred to as an onion-ring structure. The precise origin of these rings has not been established, although variations in particle number density, grain size. The thermo-mechanically affected zone occurs on either side of the stir zone, in this region the strain and temperature are lower and the effect of welding on the microstructure is correspondingly smaller. Unlike the stir zone the microstructure is recognizably that of the parent material, although the term TMAZ technically refers to the entire deformed region it is often used to describe any region not already covered by the terms stir zone and flow arm. The heat-affected zone is common to all welding processes, as indicated by the name, this region is subjected to a thermal cycle but is not deformed during welding. The temperatures are lower than those in the TMAZ but may still have a significant effect if the microstructure is thermally unstable, in fact, in age-hardened aluminium alloys this region commonly exhibits the poorest mechanical properties. The solid-state nature of FSW leads to several advantages over fusion welding methods as problems associated with cooling from the phase are avoided
42.
Robot welding
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Robot welding is the use of mechanized programmable tools, which completely automate a welding process by both performing the weld and handling the part. Processes such as gas metal arc welding, while often automated, are not necessarily equivalent to robot welding, robot welding is commonly used for resistance spot welding and arc welding in high production applications, such as the automotive industry. Robot welding is a new application of robotics, even though robots were first introduced into US industry during the 1960s. The use of robots in welding did not take off until the 1980s, since then, both the number of robots used in industry and the number of their applications has grown greatly. In 2005, more than 120,000 robots were in use in North American industry, growth is primarily limited by high equipment costs, and the resulting restriction to high-production applications. Robot arc welding has begun growing quickly just recently, and already it commands about 20% of industrial robot applications, the major components of arc welding robots are the manipulator or the mechanical unit and the controller, which acts as the robots brain. The robot may weld a pre-programmed position, be guided by machine vision, weld quality assurance FANUC KUKA Robotic welding video FANUC welding robots FANUC arc welding robots FANUC spot welding robots Robotic Friction Stir Welding video
43.
Bronze Age
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The Bronze Age is a historical period characterized by the use of bronze, proto-writing, and other early features of urban civilization. The Bronze Age is the principal period of the three-age Stone-Bronze-Iron system, as proposed in modern times by Christian Jürgensen Thomsen. An ancient civilization is defined to be in the Bronze Age either by smelting its own copper and alloying with tin, arsenic, or other metals, or by trading for bronze from production areas elsewhere. Copper-tin ores are rare, as reflected in the fact there were no tin bronzes in Western Asia before trading in bronze began in the third millennium BC. Worldwide, the Bronze Age generally followed the Neolithic period, with the Chalcolithic serving as a transition, although the Iron Age generally followed the Bronze Age, in some areas, the Iron Age intruded directly on the Neolithic. Bronze Age cultures differed in their development of the first writing, according to archaeological evidence, cultures in Mesopotamia and Egypt developed the earliest viable writing systems. The overall period is characterized by use of bronze, though the place and time of the introduction. Human-made tin bronze technology requires set production techniques, tin must be mined and smelted separately, then added to molten copper to make bronze alloy. The Bronze Age was a time of use of metals. The dating of the foil has been disputed, the Bronze Age in the ancient Near East began with the rise of Sumer in the 4th millennium BC. Societies in the region laid the foundations for astronomy and mathematics, the usual tripartite division into an Early, Middle and Late Bronze Age is not used. Instead, a division based on art-historical and historical characteristics is more common. The cities of the Ancient Near East housed several tens of thousands of people, ur in the Middle Bronze Age and Babylon in the Late Bronze Age similarly had large populations. The earliest mention of Babylonia appears on a tablet from the reign of Sargon of Akkad in the 23rd century BC, the Amorite dynasty established the city-state of Babylon in the 19th century BC. Over 100 years later, it took over the other city-states. Babylonia adopted the written Semitic Akkadian language for official use, by that time, the Sumerian language was no longer spoken, but was still in religious use. Elam was an ancient civilization located to the east of Mesopotamia, in the Old Elamite period, Elam consisted of kingdoms on the Iranian plateau, centered in Anshan, and from the mid-2nd millennium BC, it was centered in Susa in the Khuzestan lowlands. Its culture played a role in the Gutian Empire and especially during the Achaemenid dynasty that succeeded it
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