101-557: The Unión Explosivos Río Tinto ( ERT ) was a Spanish business conglomerate that operated between 1970 and 1989, being present in many industries of the country. At the time, it was the main Spanish business group by size and assets, with a network of companies that included more than forty subsidiaries. The ERT group, which started in 1970, was present in numerous sectors of the economy: mining, metallurgy , chemical industry, petrochemical industry, explosives, etc. In its beginnings, it had
202-402: A square wave pattern instead of the normal sine wave , making rapid zero crossings possible and minimizing the effects of the problem. Resistance welding involves the generation of heat by passing current through the resistance caused by the contact between two or more metal surfaces. Small pools of molten metal are formed at the weld area as high current (1,000–100,000 A ) is passed through
303-502: A Russian, Konstantin Khrenov eventually implemented the first underwater electric arc welding. Gas tungsten arc welding , after decades of development, was finally perfected in 1941, and gas metal arc welding followed in 1948, allowing for fast welding of non- ferrous materials but requiring expensive shielding gases. Shielded metal arc welding was developed during the 1950s, using a flux-coated consumable electrode, and it quickly became
404-513: A burial site located in the western industrial zone of Varna , approximately 4 km from the city centre, internationally considered one of the key archaeological sites in world prehistory. The oldest gold treasure in the world, dating from 4,600 BC to 4,200 BC, was discovered at the site. The gold piece dating from 4,500 BC, found in 2019 in Durankulak , near Varna is another important example. Other signs of early metals are found from
505-410: A ductile to brittle transition and lose their toughness, becoming more brittle and prone to cracking. Metals under continual cyclic loading can suffer from metal fatigue . Metals under constant stress at elevated temperatures can creep . Cold-working processes, in which the product's shape is altered by rolling, fabrication or other processes, while the product is cold, can increase the strength of
606-481: A gas flame (chemical), an electric arc (electrical), a laser , an electron beam , friction , and ultrasound . While often an industrial process, welding may be performed in many different environments, including in open air, under water , and in outer space . Welding is a hazardous undertaking and precautions are required to avoid burns , electric shock , vision damage, inhalation of poisonous gases and fumes, and exposure to intense ultraviolet radiation . Until
707-414: A highly concentrated, limited amount of heat, resulting in a small HAZ. Arc welding falls between these two extremes, with the individual processes varying somewhat in heat input. To calculate the heat input for arc welding procedures, the following formula can be used: where Q = heat input ( kJ /mm), V = voltage ( V ), I = current (A), and S = welding speed (mm/min). The efficiency is dependent on
808-409: A highly focused laser beam, while electron beam welding is done in a vacuum and uses an electron beam. Both have a very high energy density, making deep weld penetration possible and minimizing the size of the weld area. Both processes are extremely fast, and are easily automated, making them highly productive. The primary disadvantages are their very high equipment costs (though these are decreasing) and
909-413: A liquid bath. Metallurgists study the microscopic and macroscopic structure of metals using metallography , a technique invented by Henry Clifton Sorby . In metallography, an alloy of interest is ground flat and polished to a mirror finish. The sample can then be etched to reveal the microstructure and macrostructure of the metal. The sample is then examined in an optical or electron microscope , and
1010-401: A major concern. Cast irons, including ductile iron , are also part of the iron-carbon system. Iron-Manganese-Chromium alloys (Hadfield-type steels) are also used in non-magnetic applications such as directional drilling. Other engineering metals include aluminium , chromium , copper , magnesium , nickel , titanium , zinc , and silicon . These metals are most often used as alloys with
1111-513: A modest amount of training and can achieve mastery with experience. Weld times are rather slow, since the consumable electrodes must be frequently replaced and because slag, the residue from the flux, must be chipped away after welding. Furthermore, the process is generally limited to welding ferrous materials, though special electrodes have made possible the welding of cast iron , stainless steel, aluminum, and other metals. Gas metal arc welding (GMAW), also known as metal inert gas or MIG welding,
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#17327839632381212-627: A smelted copper axe dating from 5,500 BC, belonging to the Vinča culture . The Balkans and adjacent Carpathian region were the location of major Chalcolithic cultures including Vinča , Varna , Karanovo , Gumelnița and Hamangia , which are often grouped together under the name of ' Old Europe '. With the Carpatho-Balkan region described as the 'earliest metallurgical province in Eurasia', its scale and technical quality of metal production in
1313-447: A suitable torch was developed. At first, oxyfuel welding was one of the more popular welding methods due to its portability and relatively low cost. As the 20th century progressed, however, it fell out of favor for industrial applications. It was largely replaced with arc welding, as advances in metal coverings (known as flux ) were made. Flux covering the electrode primarily shields the base material from impurities, but also stabilizes
1414-579: A superior metal could be made, an alloy called bronze . This represented a major technological shift known as the Bronze Age . The extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. The process appears to have been invented by the Hittites in about 1200 BC, beginning the Iron Age . The secret of extracting and working iron was a key factor in
1515-434: A susceptibility to thermal cracking. Developments in this area include laser-hybrid welding , which uses principles from both laser beam welding and arc welding for even better weld properties, laser cladding , and x-ray welding . Like forge welding (the earliest welding process discovered), some modern welding methods do not involve the melting of the materials being joined. One of the most popular, ultrasonic welding ,
1616-524: A tungsten electrode but uses plasma gas to make the arc. The arc is more concentrated than the GTAW arc, making transverse control more critical and thus generally restricting the technique to a mechanized process. Because of its stable current, the method can be used on a wider range of material thicknesses than can the GTAW process and it is much faster. It can be applied to all of the same materials as GTAW except magnesium, and automated welding of stainless steel
1717-503: A workforce made up of 14,000 employees, as well as a network of facilities, factories and production centers that extended throughout the country. Its name came from the historical Rio Tinto Mines , in the province of Huelva. During the 1970s, the Explosivos Río Tinto group undertook a business diversification that led to an increase of its presence in the real estate, pharmaceutical, petrochemical or publishing sectors. This
1818-401: Is a chemical surface-treatment technique. It involves bonding a thin layer of another metal such as gold , silver , chromium or zinc to the surface of the product. This is done by selecting the coating material electrolyte solution, which is the material that is going to coat the workpiece (gold, silver, zinc). There needs to be two electrodes of different materials: one the same material as
1919-427: Is a highly productive, single-pass welding process for thicker materials between 1 inch (25 mm) and 12 inches (300 mm) in a vertical or close to vertical position. To supply the electrical power necessary for arc welding processes, a variety of different power supplies can be used. The most common welding power supplies are constant current power supplies and constant voltage power supplies. In arc welding,
2020-472: Is a ring surrounding the weld in which the temperature of the welding process, combined with the stresses of uneven heating and cooling, alters the heat-treatment properties of the alloy. The effects of welding on the material surrounding the weld can be detrimental—depending on the materials used and the heat input of the welding process used, the HAZ can be of varying size and strength. The thermal diffusivity of
2121-430: Is a semi-automatic or automatic process that uses a continuous wire feed as an electrode and an inert or semi-inert gas mixture to protect the weld from contamination. Since the electrode is continuous, welding speeds are greater for GMAW than for SMAW. A related process, flux-cored arc welding (FCAW), uses similar equipment but uses wire consisting of a steel electrode surrounding a powder fill material. This cored wire
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#17327839632382222-433: Is allowed to cool, and then another weld is performed on top of it. This allows for the welding of thick sections arranged in a single-V preparation joint, for example. After welding, a number of distinct regions can be identified in the weld area. The weld itself is called the fusion zone—more specifically, it is where the filler metal was laid during the welding process. The properties of the fusion zone depend primarily on
2323-443: Is an industrial coating process that consists of a heat source (flame or other) and a coating material that can be in a powder or wire form, which is melted then sprayed on the surface of the material being treated at a high velocity. The spray treating process is known by many different names such as HVOF (High Velocity Oxygen Fuel), plasma spray, flame spray, arc spray and metalizing. Electroless deposition (ED) or electroless plating
2424-442: Is characterized by a stable arc and high-quality welds, but it requires significant operator skill and can only be accomplished at relatively low speeds. GTAW can be used on nearly all weldable metals, though it is most often applied to stainless steel and light metals. It is often used when quality welds are extremely important, such as in bicycle , aircraft and naval applications. A related process, plasma arc welding, also uses
2525-708: Is collected and processed to extract valuable metals. Ore bodies often contain more than one valuable metal. Tailings of a previous process may be used as a feed in another process to extract a secondary product from the original ore. Additionally, a concentrate may contain more than one valuable metal. That concentrate would then be processed to separate the valuable metals into individual constituents. Much effort has been placed on understanding iron –carbon alloy system, which includes steels and cast irons . Plain carbon steels (those that contain essentially only carbon as an alloying element) are used in low-cost, high-strength applications, where neither weight nor corrosion are
2626-407: Is commonly used for making electrical connections out of aluminum or copper, and it is also a very common polymer welding process. Another common process, explosion welding , involves the joining of materials by pushing them together under extremely high pressure. The energy from the impact plasticizes the materials, forming a weld, even though only a limited amount of heat is generated. The process
2727-627: Is commonly used for welding dissimilar materials, including bonding aluminum to carbon steel in ship hulls and stainless steel or titanium to carbon steel in petrochemical pressure vessels. Other solid-state welding processes include friction welding (including friction stir welding and friction stir spot welding ), magnetic pulse welding , co-extrusion welding, cold welding , diffusion bonding , exothermic welding , high frequency welding , hot pressure welding, induction welding , and roll bonding . Welds can be geometrically prepared in many different ways. The five basic types of weld joints are
2828-455: Is defined as the autocatalytic process through which metals and metal alloys are deposited onto nonconductive surfaces. These nonconductive surfaces include plastics, ceramics, and glass etc., which can then become decorative, anti-corrosive, and conductive depending on their final functions. Electroless deposition is a chemical processes that create metal coatings on various materials by autocatalytic chemical reduction of metal cations in
2929-654: Is found in the Balkans and Carpathian Mountains , as evidenced by findings of objects made by metal casting and smelting dated to around 6000-5000 BC. Certain metals, such as tin, lead, and copper can be recovered from their ores by simply heating the rocks in a fire or blast furnace in a process known as smelting. The first evidence of copper smelting, dating from the 6th millennium BC, has been found at archaeological sites in Majdanpek , Jarmovac and Pločnik , in present-day Serbia . The site of Pločnik has produced
3030-504: Is known as a metallurgist. The science of metallurgy is further subdivided into two broad categories: chemical metallurgy and physical metallurgy . Chemical metallurgy is chiefly concerned with the reduction and oxidation of metals, and the chemical performance of metals. Subjects of study in chemical metallurgy include mineral processing , the extraction of metals , thermodynamics , electrochemistry , and chemical degradation ( corrosion ). In contrast, physical metallurgy focuses on
3131-484: Is made of filler material (typical steel) and is covered with a flux that protects the weld area from oxidation and contamination by producing carbon dioxide (CO 2 ) gas during the welding process. The electrode core itself acts as filler material, making a separate filler unnecessary. The process is versatile and can be performed with relatively inexpensive equipment, making it well suited to shop jobs and field work. An operator can become reasonably proficient with
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3232-433: Is more expensive than the standard solid wire and can generate fumes and/or slag, but it permits even higher welding speed and greater metal penetration. Gas tungsten arc welding (GTAW), or tungsten inert gas (TIG) welding, is a manual welding process that uses a non-consumable tungsten electrode, an inert or semi-inert gas mixture, and a separate filler material. Especially useful for welding thin materials, this method
3333-420: Is obtained by a metallic or chemical bond that is formed between the constituent atoms. Chemical bonds can be grouped into two types consisting of ionic and covalent . To form an ionic bond, either a valence or bonding electron separates from one atom and becomes attached to another atom to form oppositely charged ions . The bonding in the static position is when the ions occupy an equilibrium position where
3434-430: Is one important application of the process. A variation of the process is plasma cutting , an efficient steel cutting process. Submerged arc welding (SAW) is a high-productivity welding method in which the arc is struck beneath a covering layer of flux. This increases arc quality since contaminants in the atmosphere are blocked by the flux. The slag that forms on the weld generally comes off by itself, and combined with
3535-720: Is related to the Old Swedish word valla , meaning 'to boil', which could refer to joining metals, as in valla järn (literally "to boil iron"). Sweden was a large exporter of iron during the Middle Ages , so the word may have entered English from the Swedish iron trade, or may have been imported with the thousands of Viking settlements that arrived in England before and during the Viking Age , as more than half of
3636-400: Is sometimes protected by some type of inert or semi- inert gas , known as a shielding gas, and filler material is sometimes used as well. One of the most common types of arc welding is shielded metal arc welding (SMAW); it is also known as manual metal arc welding (MMAW) or stick welding. Electric current is used to strike an arc between the base material and consumable electrode rod, which
3737-438: Is still widely used for welding pipes and tubes, as well as repair work. The equipment is relatively inexpensive and simple, generally employing the combustion of acetylene in oxygen to produce a welding flame temperature of about 3100 °C (5600 °F). The flame, since it is less concentrated than an electric arc, causes slower weld cooling, which can lead to greater residual stresses and weld distortion, though it eases
3838-545: Is the more common one in the United Kingdom . The / ˈ m ɛ t əl ɜːr dʒ i / pronunciation is the more common one in the United States US and is the first-listed variant in various American dictionaries, including Merriam-Webster Collegiate and American Heritage . The earliest metal employed by humans appears to be gold , which can be found " native ". Small amounts of natural gold, dating to
3939-470: Is used to connect thin sheets or wires made of metal or thermoplastic by vibrating them at high frequency and under high pressure. The equipment and methods involved are similar to that of resistance welding, but instead of electric current, vibration provides energy input. When welding metals, the vibrations are introduced horizontally, and the materials are not melted; with plastics, which should have similar melting temperatures, vertically. Ultrasonic welding
4040-403: The science and the technology of metals, including the production of metals and the engineering of metal components used in products for both consumers and manufacturers. Metallurgy is distinct from the craft of metalworking . Metalworking relies on metallurgy in a similar manner to how medicine relies on medical science for technical advancement. A specialist practitioner of metallurgy
4141-461: The 1590 version this was changed to " ...thei shullen welle togidere her swerdes in-to scharris... " (they shall weld together their swords into plowshares), suggesting this particular use of the word probably became popular in English sometime between these periods. The Old English word for welding iron was samod ('to bring together') or samodwellung ('to bring together hot'). The word
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4242-421: The 1930s and then during World War II. In 1930, the first all-welded merchant vessel, M/S Carolinian , was launched. During the middle of the century, many new welding methods were invented. In 1930, Kyle Taylor was responsible for the release of stud welding , which soon became popular in shipbuilding and construction. Submerged arc welding was invented the same year and continues to be popular today. In 1932
4343-527: The 6th–5th millennia BC totally overshadowed that of any other contemporary production centre. The earliest documented use of lead (possibly native or smelted) in the Near East dates from the 6th millennium BC, is from the late Neolithic settlements of Yarim Tepe and Arpachiyah in Iraq . The artifacts suggest that lead smelting may have predated copper smelting. Metallurgy of lead has also been found in
4444-664: The Balkans during the same period. Copper smelting is documented at sites in Anatolia and at the site of Tal-i Iblis in southeastern Iran from c. 5000 BC. Copper smelting is first documented in the Delta region of northern Egypt in c. 4000 BC, associated with the Maadi culture . This represents the earliest evidence for smelting in Africa. The Varna Necropolis , Bulgaria , is
4545-564: The Soviet scientist N. F. Kazakov proposed the diffusion bonding method. Other recent developments in welding include the 1958 breakthrough of electron beam welding, making deep and narrow welding possible through the concentrated heat source. Following the invention of the laser in 1960, laser beam welding debuted several decades later, and has proved to be especially useful in high-speed, automated welding. Magnetic pulse welding (MPW) has been industrially used since 1967. Friction stir welding
4646-512: The amount of phases present as well as the degree of strain to which a sample has been subjected. Current advanced characterization techniques, which are used frequently in this field are: Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Electron Backscattered Diffraction (EBSD) and Atom-Probe Tomography (APT). Welding Welding is a fabrication process that joins materials, usually metals or thermoplastics , primarily by using high temperature to melt
4747-469: The arc and can add alloying components to the weld metal. World War I caused a major surge in the use of welding, with the various military powers attempting to determine which of the several new welding processes would be best. The British primarily used arc welding, even constructing a ship, the "Fullagar" with an entirely welded hull. Arc welding was first applied to aircraft during the war as well, as some German airplane fuselages were constructed using
4848-437: The atmosphere. Porosity and brittleness were the primary problems, and the solutions that developed included the use of hydrogen , argon , and helium as welding atmospheres. During the following decade, further advances allowed for the welding of reactive metals like aluminum and magnesium . This in conjunction with developments in automatic welding, alternating current, and fluxes fed a major expansion of arc welding during
4949-433: The base material plays a large role—if the diffusivity is high, the material cooling rate is high and the HAZ is relatively small. Conversely, a low diffusivity leads to slower cooling and a larger HAZ. The amount of heat injected by the welding process plays an important role as well, as processes like oxyacetylene welding have an unconcentrated heat input and increase the size of the HAZ. Processes like laser beam welding give
5050-516: The base metal (parent metal) and instead require flowing a filler metal to solidify their bonds. In addition to melting the base metal in welding, a filler material is typically added to the joint to form a pool of molten material (the weld pool ) that cools to form a joint that can be stronger than the base material. Welding also requires a form of shield to protect the filler metals or melted metals from being contaminated or oxidized . Many different energy sources can be used for welding, including
5151-402: The butt joint, lap joint, corner joint, edge joint, and T-joint (a variant of this last is the cruciform joint ). Other variations exist as well—for example, double-V preparation joints are characterized by the two pieces of material each tapering to a single center point at one-half their height. Single-U and double-U preparation joints are also fairly common—instead of having straight edges like
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#17327839632385252-416: The coating material and one that is receiving the coating material. Two electrodes are electrically charged and the coating material is stuck to the work piece. It is used to reduce corrosion as well as to improve the product's aesthetic appearance. It is also used to make inexpensive metals look like the more expensive ones (gold, silver). Shot peening is a cold working process used to finish metal parts. In
5353-419: The demand for reliable and inexpensive joining methods. Following the wars, several modern welding techniques were developed, including manual methods like shielded metal arc welding , now one of the most popular welding methods, as well as semi-automatic and automatic processes such as gas metal arc welding , submerged arc welding , flux-cored arc welding and electroslag welding . Developments continued with
5454-518: The distance between the wire and the base material is quickly rectified by a large change in current. For example, if the wire and the base material get too close, the current will rapidly increase, which in turn causes the heat to increase and the tip of the wire to melt, returning it to its original separation distance. The type of current used plays an important role in arc welding. Consumable electrode processes such as shielded metal arc welding and gas metal arc welding generally use direct current, but
5555-443: The durability of many designs increases significantly. Most solids used are engineering materials consisting of crystalline solids in which the atoms or ions are arranged in a repetitive geometric pattern which is known as a lattice structure . The only exception is material that is made from glass which is a combination of a supercooled liquid and polymers which are aggregates of large organic molecules. Crystalline solids cohesion
5656-600: The electrode can be charged either positively or negatively. In welding, the positively charged anode will have a greater heat concentration, and as a result, changing the polarity of the electrode affects weld properties. If the electrode is positively charged, the base metal will be hotter, increasing weld penetration and welding speed. 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. However, with direct current, because
5757-442: The electrode only creates the arc and does not provide filler material, a positively charged electrode causes shallow welds, while a negatively charged electrode makes deeper welds. Alternating current rapidly moves between these two, resulting in medium-penetration welds. One disadvantage of AC, the fact that the arc must be re-ignited after every zero crossings, has been addressed with the invention of special power units that produce
5858-404: The electrode perfectly steady, and as a result, the arc length and thus voltage tend to fluctuate. Constant voltage power supplies hold the voltage constant and vary the current, and as a result, are most often used for automated welding processes such as gas metal arc welding, flux-cored arc welding, and submerged arc welding. In these processes, arc length is kept constant, since any fluctuation in
5959-408: The end of the 19th century, the only welding process was forge welding , which blacksmiths had used for millennia to join iron and steel by heating and hammering. Arc welding and oxy-fuel welding were among the first processes to develop late in the century, and electric resistance welding followed soon after. Welding technology advanced quickly during the early 20th century, as world wars drove
6060-438: The filler metal used, and its compatibility with the base materials. It is surrounded by the heat-affected zone , the area that had its microstructure and properties altered by the weld. These properties depend on the base material's behavior when subjected to heat. The metal in this area is often weaker than both the base material and the fusion zone, and is also where residual stresses are found. Many distinct factors influence
6161-619: The highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. Agricola has been described as the "father of metallurgy". Extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. In order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically , or electrolytically . Extractive metallurgists are interested in three primary streams: feed, concentrate (metal oxide/sulphide) and tailings (waste). After mining, large pieces of
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#17327839632386262-402: The image contrast provides details on the composition, mechanical properties, and processing history. Crystallography , often using diffraction of x-rays or electrons , is another valuable tool available to the modern metallurgist. Crystallography allows identification of unknown materials and reveals the crystal structure of the sample. Quantitative crystallography can be used to calculate
6363-582: The invention of laser beam welding , electron beam welding , magnetic pulse welding , and friction stir welding in the latter half of the century. Today, as the science continues to advance, robot welding is commonplace in industrial settings, and researchers continue to develop new welding methods and gain greater understanding of weld quality. The term weld is derived from the Middle English verb well ( wæll ; plural/present tense: wælle ) or welling ( wællen ), meaning 'to heat' (to
6464-536: The invention of metal electrodes in the late 1800s by a Russian, Nikolai Slavyanov (1888), and an American, C. L. Coffin (1890). Around 1900, A. P. Strohmenger released a coated metal electrode in Britain , which gave a more stable arc. In 1905, Russian scientist Vladimir Mitkevich proposed using a three-phase electric arc for welding. Alternating current welding was invented by C. J. Holslag in 1919, but did not become popular for another decade. Resistance welding
6565-508: The joining of metals (including welding , brazing , and soldering ). Emerging areas for metallurgists include nanotechnology , superconductors , composites , biomedical materials , electronic materials (semiconductors) and surface engineering . Metallurgy derives from the Ancient Greek μεταλλουργός , metallourgós , "worker in metal", from μέταλλον , métallon , "mine, metal" + ἔργον , érgon , "work" The word
6666-505: The late Paleolithic period, 40,000 BC, have been found in Spanish caves. Silver , copper , tin and meteoric iron can also be found in native form, allowing a limited amount of metalworking in early cultures. Early cold metallurgy, using native copper not melted from mineral has been documented at sites in Anatolia and at the site of Tell Maghzaliyah in Iraq , dating from the 7th/6th millennia BC. The earliest archaeological support of smelting (hot metallurgy) in Eurasia
6767-412: The length of the arc is directly related to the voltage, and the amount of heat input is related to the current. Constant current power supplies are most often used for manual welding processes such as gas tungsten arc welding and shielded metal arc welding, because they maintain a relatively constant current even as the voltage varies. This is important because in manual welding, it can be difficult to hold
6868-532: The material may not have the ability to withstand the stress and could cause cracking, one method the control these stress would be to control the heating and cooling rate, such as pre-heating and post- heating The durability and life of dynamically loaded, welded steel structures is determined in many cases by the welds, in particular the weld transitions. Through selective treatment of the transitions by grinding (abrasive cutting) , shot peening , High-frequency impact treatment , Ultrasonic impact treatment , etc.
6969-715: The maximum temperature possible); 'to bring to a boil'. The modern word was probably derived from the past-tense participle welled ( wællende ), with the addition of d for this purpose being common in the Germanic languages of the Angles and Saxons . It was first recorded in English in 1590. A fourteenth century translation of the Christian Bible into English by John Wycliffe translates Isaiah 2:4 as " ...thei shul bete togidere their swerdes into shares... " (they shall beat together their swords into plowshares). In
7070-427: The mechanical properties of metals, the physical properties of metals, and the physical performance of metals. Topics studied in physical metallurgy include crystallography , material characterization , mechanical metallurgy, phase transformations , and failure mechanisms . Historically, metallurgy has predominately focused on the production of metals. Metal production begins with the processing of ores to extract
7171-917: The metal, and includes the mixture of metals to make alloys . Metal alloys are often a blend of at least two different metallic elements. However, non-metallic elements are often added to alloys in order to achieve properties suitable for an application. The study of metal production is subdivided into ferrous metallurgy (also known as black metallurgy ) and non-ferrous metallurgy , also known as colored metallurgy. Ferrous metallurgy involves processes and alloys based on iron , while non-ferrous metallurgy involves processes and alloys based on other metals. The production of ferrous metals accounts for 95% of world metal production. Modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. Some traditional areas include mineral processing, metal production, heat treatment, failure analysis , and
7272-426: The metal. In general, resistance welding methods are efficient and cause little pollution, but their applications are somewhat limited and the equipment cost can be high. Spot welding is a popular resistance welding method used to join overlapping metal sheets of up to 3 mm thick. Two electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. The advantages of
7373-697: The method include efficient energy use , limited workpiece deformation, high production rates, easy automation, and no required filler materials. Weld strength is significantly lower than with other welding methods, making the process suitable for only certain applications. It is used extensively in the automotive industry—ordinary cars can have several thousand spot welds made by industrial robots . A specialized process called shot welding , can be used to spot weld stainless steel. Like spot welding, seam welding relies on two electrodes to apply pressure and current to join metal sheets. However, instead of pointed electrodes, wheel-shaped electrodes roll along and often feed
7474-650: The most common English words in everyday use are Scandinavian in origin. The history of joining metals goes back several millennia. The earliest examples of this come from the Bronze and Iron Ages in Europe and the Middle East . The ancient Greek historian Herodotus states in The Histories of the 5th century BC that Glaucus of Chios "was the man who single-handedly invented iron welding". Forge welding
7575-415: The most popular metal arc welding process. In 1957, the flux-cored arc welding process debuted, in which the self-shielded wire electrode could be used with automatic equipment, resulting in greatly increased welding speeds, and that same year, plasma arc welding was invented by Robert Gage. Electroslag welding was introduced in 1958, and it was followed by its cousin, electrogas welding , in 1961. In 1953,
7676-553: The noted exception of silicon, which is not a metal. Other forms include: In production engineering , metallurgy is concerned with the production of metallic components for use in consumer or engineering products. This involves production of alloys, shaping, heat treatment and surface treatment of product. The task of the metallurgist is to achieve balance between material properties, such as cost, weight , strength , toughness , hardness , corrosion , fatigue resistance and performance in temperature extremes. To achieve this goal,
7777-512: The operating environment must be carefully considered. Determining the hardness of the metal using the Rockwell, Vickers, and Brinell hardness scales is a commonly used practice that helps better understand the metal's elasticity and plasticity for different applications and production processes. In a saltwater environment, most ferrous metals and some non-ferrous alloys corrode quickly. Metals exposed to cold or cryogenic conditions may undergo
7878-482: The ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or mostly waste. Concentrating the particles of value in a form supporting separation enables the desired metal to be removed from waste products. Mining may not be necessary, if the ore body and physical environment are conducive to leaching . Leaching dissolves minerals in an ore body and results in an enriched solution. The solution
7979-440: The parts together and allow them to cool, causing fusion . Common alternative methods include solvent welding (of thermoplastics) using chemicals to melt materials being bonded without heat, and solid-state welding processes which bond without melting, such as pressure, cold welding , and diffusion bonding . Metal welding is distinct from lower temperature bonding techniques such as brazing and soldering , which do not melt
8080-402: The piece being treated. The compression stress in the surface of the material strengthens the part and makes it more resistant to fatigue failure, stress failures, corrosion failure, and cracking. Thermal spraying techniques are another popular finishing option, and often have better high temperature properties than electroplated coatings. Thermal spraying, also known as a spray welding process,
8181-445: The process of shot peening, small round shot is blasted against the surface of the part to be finished. This process is used to prolong the product life of the part, prevent stress corrosion failures, and also prevent fatigue. The shot leaves small dimples on the surface like a peen hammer does, which cause compression stress under the dimple. As the shot media strikes the material over and over, it forms many overlapping dimples throughout
8282-436: The process, and the industry continued to grow during the following centuries. In 1800, Sir Humphry Davy discovered the short-pulse electrical arc and presented his results in 1801. In 1802, Russian scientist Vasily Petrov created the continuous electric arc, and subsequently published "News of Galvanic-Voltaic Experiments" in 1803, in which he described experiments carried out in 1802. Of great importance in this work
8383-553: The process. Also noteworthy is the first welded road bridge in the world, the Maurzyce Bridge in Poland (1928). During the 1920s, significant advances were made in welding technology, including the introduction of automatic welding in 1920, in which electrode wire was fed continuously. Shielding gas became a subject receiving much attention, as scientists attempted to protect welds from the effects of oxygen and nitrogen in
8484-666: The product by a process called work hardening . Work hardening creates microscopic defects in the metal, which resist further changes of shape. Metals can be heat-treated to alter the properties of strength, ductility, toughness, hardness and resistance to corrosion. Common heat treatment processes include annealing, precipitation strengthening , quenching, and tempering: Often, mechanical and thermal treatments are combined in what are known as thermo-mechanical treatments for better properties and more efficient processing of materials. These processes are common to high-alloy special steels, superalloys and titanium alloys. Electroplating
8585-442: The quality of welding procedure specification , how to judge the skill of the person performing the weld, and how to ensure the quality of a welding job. Methods such as visual inspection , radiography , ultrasonic testing , phased-array ultrasonics , dye penetrant inspection , magnetic particle inspection , or industrial computed tomography can help with detection and analysis of certain defects. The heat-affected zone (HAZ)
8686-650: The quality of a weld, either destructive or nondestructive testing methods are commonly used to verify that welds are free of defects, have acceptable levels of residual stresses and distortion, and have acceptable heat-affected zone (HAZ) properties. Types of welding defects include cracks, distortion, gas inclusions (porosity), non-metallic inclusions, lack of fusion, incomplete penetration, lamellar tearing, and undercutting. The metalworking industry has instituted codes and specifications to guide welders , weld inspectors , engineers , managers, and property owners in proper welding technique, design of welds, how to judge
8787-428: The resulting force between them is zero. When the ions are exerted in tension force, the inter-ionic spacing increases creating an electrostatic attractive force, while a repulsing force under compressive force between the atomic nuclei is dominant. Covalent bonding takes place when one of the constituent atoms loses one or more electrons, with the other atom gaining the electrons, resulting in an electron cloud that
8888-667: The single-V and double-V preparation joints, they are curved, forming the shape of a U. Lap joints are also commonly more than two pieces thick—depending on the process used and the thickness of the material, many pieces can be welded together in a lap joint geometry. Many welding processes require the use of a particular joint design; for example, resistance spot welding, laser beam welding, and electron beam welding are most frequently performed on lap joints. Other welding methods, like shielded metal arc welding, are extremely versatile and can weld virtually any type of joint. Some processes can also be used to make multipass welds, in which one weld
8989-604: The strength of welds and the material around them, including the welding method, the amount and concentration of energy input, the weldability of the base material, filler material, and flux material, the design of the joint, and the interactions between all these factors. For example, the factor of welding position influences weld quality, that welding codes & specifications may require testing—both welding procedures and welders—using specified welding positions: 1G (flat), 2G (horizontal), 3G (vertical), 4G (overhead), 5G (horizontal fixed pipe), or 6G (inclined fixed pipe). To test
9090-728: The success of the Philistines . Historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. This includes the ancient and medieval kingdoms and empires of the Middle East and Near East , ancient Iran , ancient Egypt , ancient Nubia , and Anatolia in present-day Turkey , Ancient Nok , Carthage , the Celts , Greeks and Romans of ancient Europe , medieval Europe, ancient and medieval China , ancient and medieval India , ancient and medieval Japan , amongst others. A 16th century book by Georg Agricola , De re metallica , describes
9191-568: The third millennium BC in Palmela , Portugal, Los Millares , Spain, and Stonehenge , United Kingdom. The precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing. In approximately 1900 BC, ancient iron smelting sites existed in Tamil Nadu . In the Near East , about 3,500 BC, it was discovered that by combining copper and tin,
9292-468: The use of a continuous wire feed, the weld deposition rate is high. Working conditions are much improved over other arc welding processes, since the flux hides the arc and almost no smoke is produced. The process is commonly used in industry, especially for large products and in the manufacture of welded pressure vessels. Other arc welding processes include atomic hydrogen welding , electroslag welding (ESW), electrogas welding , and stud arc welding . ESW
9393-415: The welding of high alloy steels. A similar process, generally called oxyfuel cutting, is used to cut metals. These processes use a welding power supply to create and maintain an electric arc between an electrode and the base material to melt metals at the welding point. They can use either direct current (DC) or alternating current (AC), and consumable or non-consumable electrodes . The welding region
9494-420: The welding process used, with shielded metal arc welding having a value of 0.75, gas metal arc welding and submerged arc welding, 0.9, and gas tungsten arc welding, 0.8. Methods of alleviating the stresses and brittleness created in the HAZ include stress relieving and tempering . One major defect concerning the HAZ would be cracking at the toes , due to the rapid expansion (heating) and contraction (cooling)
9595-585: The workpiece, making it possible to make long continuous welds. In the past, this process was used in the manufacture of beverage cans, but now its uses are more limited. Other resistance welding methods include butt welding , flash welding , projection welding , and upset welding . Energy beam welding methods, namely laser beam welding and electron beam welding , are relatively new processes that have become quite popular in high production applications. The two processes are quite similar, differing most notably in their source of power. Laser beam welding employs
9696-415: Was also developed during the final decades of the 19th century, with the first patents going to Elihu Thomson in 1885, who produced further advances over the next 15 years. Thermite welding was invented in 1893, and around that time another process, oxyfuel welding , became well established. Acetylene was discovered in 1836 by Edmund Davy , but its use was not practical in welding until about 1900, when
9797-442: Was carried out through loans and significant indebtedness. In 1989, after many years of crisis due to financial problems, ERT was integrated into the holding Ercros . Metallurgy Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements , their inter-metallic compounds , and their mixtures, which are known as alloys . Metallurgy encompasses both
9898-519: Was invented in 1991 by Wayne Thomas at The Welding Institute (TWI, UK) and found high-quality applications all over the world. All of these four new processes continue to be quite expensive due to the high cost of the necessary equipment, and this has limited their applications. The most common gas welding process is oxyfuel welding, also known as oxyacetylene welding. It is one of the oldest and most versatile welding processes, but in recent years it has become less popular in industrial applications. It
9999-434: Was originally an alchemist 's term for the extraction of metals from minerals, the ending -urgy signifying a process, especially manufacturing: it was discussed in this sense in the 1797 Encyclopædia Britannica . In the late 19th century, metallurgy's definition was extended to the more general scientific study of metals, alloys, and related processes. In English , the / m ɛ ˈ t æ l ər dʒ i / pronunciation
10100-457: Was the description of a stable arc discharge and the indication of its possible use for many applications, one being melting metals. In 1808, Davy, who was unaware of Petrov's work, rediscovered the continuous electric arc. In 1881–82 inventors Nikolai Benardos (Russian) and Stanisław Olszewski (Polish) created the first electric arc welding method known as carbon arc welding using carbon electrodes. The advances in arc welding continued with
10201-532: Was used in the construction of the Iron pillar of Delhi , erected in Delhi , India about 310 AD and weighing 5.4 metric tons . The Middle Ages brought advances in forge welding , in which blacksmiths pounded heated metal repeatedly until bonding occurred. In 1540, Vannoccio Biringuccio published De la pirotechnia , which includes descriptions of the forging operation. Renaissance craftsmen were skilled in
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