114-534: (Redirected from Welds ) [REDACTED] Look up weld in Wiktionary, the free dictionary. Weld may refer to: Welding , a metalworking technique Weld (name) , and persons with the name Port Weld , now Kuala Sepetang , Perak , Malaysia Weld, Maine , United States Weld County, Colorado , United States Weld (album) , 1991, by Neil Young & Crazy Horse Weld (dye) Reseda luteola ,
228-402: 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
342-439: A 3 GHz sound wave could produce resolution comparable to an optical image, was recognized by Sergei Sokolov in 1939. Such frequencies were not possible at the time, and what technology did exist produced relatively low-contrast images with poor sensitivity. Ultrasonic imaging uses frequencies of 2 megahertz and higher; the shorter wavelength allows resolution of small internal details in structures and tissues. The power density
456-502: 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
570-412: A bat, some insects will make evasive manoeuvres to escape being caught. Ultrasonic frequencies trigger a reflex action in the noctuid moth that causes it to drop slightly in its flight to evade attack. Tiger moths also emit clicks which may disturb bats' echolocation, and in other cases may advertise the fact that they are poisonous by emitting sound. Dogs and cats' hearing range extends into
684-481: 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
798-502: A high-frequency hydraulic whistle at the focus of a mirror and use the beam for locating submerged navigational hazards. A prototype was built by Sir Charles Parsons , the inventor of the vapour turbine , but the device was found not to be suitable for this purpose. Langevin's device made use of the piezoelectric effect , which he had been acquainted with whilst a student at the laboratory of Jacques and Pierre Curie . Langevin calculated and built an ultrasound transducer comprising
912-414: 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
1026-409: 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
1140-427: A large grain size that produces a high level of background noise in measurements. Ultrasonic thickness measurement is one technique used to monitor quality of welds. A common use of ultrasound is in underwater range finding ; this use is also called sonar . An ultrasonic pulse is generated in a particular direction. If there is an object in the path of this pulse, part or all of the pulse will be reflected back to
1254-513: 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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#17327646783941368-428: A plant, and intense yellow dye made from it Weld (band) [ no ] , Norwegian rock group See also [ edit ] WELD (disambiguation) Wield Wild (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Weld . If an internal link led you here, you may wish to change the link to point directly to
1482-417: A pulsed-ultrasonic technology is that the transmit signal consists of short bursts of ultrasonic energy. After each burst, the electronics looks for a return signal within a small window of time corresponding to the time it takes for the energy to pass through the vessel. Only a signal received during this window will qualify for additional signal processing. A popular consumer application of ultrasonic ranging
1596-451: A substantial reduction in the reaction time, like in the transesterification of oil into biodiesel . Substantial ultrasonic intensity and high ultrasonic vibration amplitudes are required for many processing applications, such as nano-crystallization, nano-emulsification, deagglomeration, extraction, cell disruption, as well as many others. Commonly, a process is first tested on a laboratory scale to prove feasibility and establish some of
1710-657: A substantial time commitment for continuous data collection and operator training. Nevertheless, this technology has proven useful in managing and running a cattle breeding operation. High-power applications of ultrasound often use frequencies between 20 kHz and a few hundred kHz. Intensities can be very high; above 10 watts per square centimeter, cavitation can be inducted in liquid media, and some applications use up to 1000 watts per square centimeter. Such high intensities can induce chemical changes or produce significant effects by direct mechanical action, and can inactivate harmful microorganisms. Ultrasound has been used since
1824-447: 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
1938-434: 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 ,
2052-523: A thin sheet of quartz sandwiched between two steel plates. Langevin was the first to report cavitation -related bioeffects from ultrasound. 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. Ultrasound can be generated at very high frequencies; ultrasound
2166-524: 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
2280-470: A very fine spray), is a popular type of humidifier. It works by vibrating a metal plate at ultrasonic frequencies to nebulize (sometimes incorrectly called "atomize") the water. Because the water is not heated for evaporation, it produces a cool mist. The ultrasonic pressure waves nebulize not only the water but also materials in the water including calcium, other minerals, viruses, fungi, bacteria, and other impurities. Illness caused by impurities that reside in
2394-413: Is a Real-Time Locating System (RTLS) or Indoor Positioning System (IPS) technology used to automatically track and identify the location of objects in real time using simple, inexpensive nodes (badges/tags) attached to or embedded in objects and devices, which then transmit an ultrasound signal to communicate their location to microphone sensors. The potential for ultrasonic imaging of objects, in which
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#17327646783942508-427: 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,
2622-472: 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
2736-430: 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
2850-433: 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
2964-609: Is also increasingly being used in trauma and first aid cases, with emergency ultrasound being used by some EMT response teams. Furthermore, ultrasound is used in remote diagnosis cases where teleconsultation is required, such as scientific experiments in space or mobile sports team diagnosis. According to RadiologyInfo, ultrasounds are useful in the detection of pelvic abnormalities and can involve techniques known as abdominal (transabdominal) ultrasound, vaginal (transvaginal or endovaginal) ultrasound in women, and also rectal (transrectal) ultrasound in men. Diagnostic ultrasound
3078-449: Is also used to visualize fetuses during routine and emergency prenatal care . Such diagnostic applications used during pregnancy are referred to as obstetric sonography . As currently applied in the medical field, properly performed ultrasound poses no known risks to the patient. Sonography does not use ionizing radiation , and the power levels used for imaging are too low to cause adverse heating or pressure effects in tissue. Although
3192-565: Is an ultrasound-based diagnostic medical imaging technique used to visualize muscles, tendons, and many internal organs to capture their size, structure and any pathological lesions with real time tomographic images. Ultrasound has been used by radiologists and sonographers to image the human body for at least 50 years and has become a widely used diagnostic tool. The technology is relatively inexpensive and portable, especially when compared with other techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT). Ultrasound
3306-494: Is applied. These frequencies range between 25 and 55 kHz, with the displacement amplitude of the resonant body of between 22 and 50 μm (0.00087 and 0.0020 in). UIT devices rely on magnetostrictive transducers. Ultrasonication offers great potential in the processing of liquids and slurries, by improving the mixing and chemical reactions in various applications and industries. Ultrasonication generates alternating low-pressure and high-pressure waves in liquids, leading to
3420-420: Is called "direct scalability". It is important to point out that increasing the power of the ultrasonic processor alone does not result in direct scalability, since it may be (and frequently is) accompanied by a reduction in the ultrasonic amplitude and cavitation intensity. During direct scale-up, all processing conditions must be maintained, while the power rating of the equipment is increased in order to enable
3534-442: 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
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3648-407: 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
3762-627: 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
3876-545: 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, because in humans the upper limit pitch of hearing tends to decrease with age. An American cell phone company has used this to create ring signals that supposedly are only audible to younger humans, but many older people can hear
3990-598: Is generally less than 1 watt per square centimetre to avoid heating and cavitation effects in the object under examination. Ultrasonic imaging applications include industrial nondestructive testing, quality control and medical uses. Acoustic microscopy is the technique of using sound waves to visualize structures too small to be resolved by the human eye. High and ultra high frequencies up to several gigahertz are used in acoustic microscopes. The reflection and diffraction of sound waves from microscopic structures can yield information not available with light. Medical ultrasound
4104-484: 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
4218-433: 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
4332-420: 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
4446-430: 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
4560-720: 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
4674-607: Is shared by the molecule as a whole. In both ionic and covalent bonding the location of the ions and electrons are constrained relative to each other, thereby resulting in the bond being characteristically brittle . Ultrasound Ultrasound is sound with frequencies greater than 20 kilohertz . This frequency is the approximate upper audible limit of human hearing in healthy young adults. The physical principles of acoustic waves apply to any frequency range, including ultrasound. Ultrasonic devices operate with frequencies from 20 kHz up to several gigahertz. Ultrasound
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4788-400: 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
4902-438: 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
5016-455: Is used externally in horses for evaluation of soft tissue and tendon injuries, and internally in particular for reproductive work – evaluation of the reproductive tract of the mare and pregnancy detection. It may also be used in an external manner in stallions for evaluation of testicular condition and diameter as well as internally for reproductive evaluation (deferent duct etc.). By 2005, ultrasound technology began to be used by
5130-484: Is used for sonochemistry at frequencies up to multiple hundreds of kilohertz. Medical imaging equipment uses frequencies in the MHz range. UHF ultrasound waves have been generated as high as the gigahertz range. Characterizing extremely high-frequency ultrasound poses challenges, as such rapid movement causes waveforms to steepen and form shock waves . The upper frequency limit in humans (approximately 20 kHz)
5244-463: 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 accelerating chemical processes. Animals such as bats and porpoises use ultrasound for locating prey and obstacles. Acoustics ,
5358-470: 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
5472-461: 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
5586-421: 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
5700-581: The 1940s by physical and occupational therapists for treating connective tissue : ligaments , tendons , and fascia (and also scar tissue ). Conditions for which ultrasound may be used for treatment include the follow examples: ligament sprains , muscle strains , tendonitis , joint inflammation, plantar fasciitis , metatarsalgia , facet irritation, impingement syndrome , bursitis , rheumatoid arthritis , osteoarthritis , and scar tissue adhesion. Relatively high power ultrasound can break up stony deposits or tissue, increase skin permeability , accelerate
5814-528: The 1960s. Ultrasonic inspection eliminates the use of ionizing radiation, with safety and cost benefits. Ultrasound can also provide additional information such as the depth of flaws in a welded joint. Ultrasonic inspection has progressed from manual methods to computerized systems that automate much of the process. An ultrasonic test of a joint can identify the existence of flaws, measure their size, and identify their location. Not all welded materials are equally amenable to ultrasonic inspection; some materials have
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#17327646783945928-580: The School of Physics and Chemistry in Paris, to evaluate it. Chilowski's proposal was to excite a cylindrical, mica condenser by a high-frequency Poulsen arc at approximately 100 kHz and thus to generate an ultrasound beam for detecting submerged objects. The idea of locating underwater obstacles had been suggested prior by L. F. Richardson, following the Titanic disaster. Richardson had proposed to position
6042-564: 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
6156-469: The UIT tool, made up of the ultrasonic transducer, pins and other components, comes into contact with the work piece it acoustically couples with the work piece, creating harmonic resonance. This harmonic resonance is performed at a carefully calibrated frequency, to which metals respond very favorably. Depending on the desired effects of treatment a combination of different frequencies and displacement amplitude
6270-469: 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
6384-437: 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
6498-433: 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
6612-516: 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
6726-466: The beef cattle industry to improve animal health and the yield of cattle operations. Ultrasound is used to evaluate fat thickness, rib eye area, and intramuscular fat in living animals. It is also used to evaluate the health and characteristics of unborn calves. Ultrasound technology provides a means for cattle producers to obtain information that can be used to improve the breeding and husbandry of cattle. The technology can be expensive, and it requires
6840-402: 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
6954-759: The collapse of millions of microscopic cavitation bubbles near the dirty surface. The collapsing bubbles form tiny shockwaves that break up and disperse contaminants on the object's surface. Similar to ultrasonic cleaning, biological cells including bacteria can be disintegrated. High power ultrasound produces cavitation that facilitates particle disintegration or reactions. This has uses in biological science for analytical or chemical purposes ( sonication and sonoporation ) and in killing bacteria in sewage. High power ultrasound can disintegrate corn slurry and enhance liquefaction and saccharification for higher ethanol yield in dry corn milling plants. The ultrasonic humidifier, one type of nebulizer (a device that creates
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#17327646783947068-419: 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
7182-518: 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
7296-443: 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
7410-763: The effect of drugs in a targeted area, assist in the measurement of the elastic properties of tissue, and can be used to sort cells or small particles for research. Ultrasonic impact treatment (UIT) uses ultrasound to enhance the mechanical and physical properties of metals. It is a metallurgical processing technique in which ultrasonic energy is applied to a metal object. Ultrasonic treatment can result in controlled residual compressive stress, grain refinement and grain size reduction. Low and high cycle fatigue are enhanced and have been documented to provide increases up to ten times greater than non-UIT specimens. Additionally, UIT has proven effective in addressing stress corrosion cracking , corrosion fatigue and related issues. When
7524-600: 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
7638-442: 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
7752-404: 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
7866-408: 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
7980-438: 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
8094-474: The formation and violent collapse of small vacuum bubbles. This phenomenon is termed cavitation and causes high speed impinging liquid jets and strong hydrodynamic shear-forces. These effects are used for the deagglomeration and milling of micrometre and nanometre-size materials as well as for the disintegration of cells or the mixing of reactants. In this aspect, ultrasonication is an alternative to high-speed mixers and agitator bead mills. Ultrasonic foils under
8208-545: The hearing range of humans and other animals, demonstrating that many animals could hear sounds above the hearing range of humans. The first article on the history of ultrasound was written in 1948. According to its author, during the First World War , a Russian engineer named Chilowski submitted an idea for submarine detection to the French Government. The latter invited Paul Langevin , then Director of
8322-570: The highest known upper hearing limit at around 160 kHz. Several types of fish can detect ultrasound. In the order Clupeiformes , members of the subfamily Alosinae ( shad ) have been shown to be able to detect sounds up to 180 kHz, while the other subfamilies (e.g. herrings ) can hear only up to 4 kHz. No bird species have been reported to be sensitive to ultrasound. Commercial ultrasonic systems have been sold for supposed indoors electronic pest control and outdoors ultrasonic algae control . However, no scientific evidence exists on
8436-465: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Weld&oldid=1245524893 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Welding Welding is a fabrication process that joins materials, usually metals or thermoplastics , primarily by using high temperature to melt
8550-582: 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
8664-536: 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
8778-571: The layout of rooms. Although range finding underwater is performed at both sub-audible and audible frequencies for great distances (1 to several kilometers), ultrasonic range finding is used when distances are shorter and the accuracy of the distance measurement is desired to be finer. Ultrasonic measurements may be limited through barrier layers with large salinity, temperature or vortex differentials. Ranging in water varies from about hundreds to thousands of meters, but can be performed with centimeters to meters accuracy Ultrasound Identification (USID)
8892-412: 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
9006-545: The long-term effects due to ultrasound exposure at diagnostic intensity are still unknown, currently most doctors feel that the benefits to patients outweigh the risks. The ALARA (As Low As Reasonably Achievable) principle has been advocated for an ultrasound examination – that is, keeping the scanning time and power settings as low as possible but consistent with diagnostic imaging – and that by that principle nonmedical uses, which by definition are not necessary, are actively discouraged. Ultrasound
9120-532: 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.
9234-715: 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
9348-426: 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
9462-697: 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
9576-650: 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
9690-415: 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,
9804-470: The moving wire in a paper machine will use the shock waves from the imploding bubbles to distribute the cellulose fibres more uniformly in the produced paper web, which will make a stronger paper with more even surfaces. Furthermore, chemical reactions benefit from the free radicals created by the cavitation as well as from the energy input and the material transfer through boundary layers. For many processes, this sonochemical (see sonochemistry ) effect leads to
9918-546: The operation of a larger ultrasonic horn. A researcher at the Industrial Materials Research Institute, Alessandro Malutta, devised an experiment that demonstrated the trapping action of ultrasonic standing waves on wood pulp fibers diluted in water and their parallel orienting into the equidistant pressure planes. The time to orient the fibers in equidistant planes is measured with a laser and an electro-optical sensor. This could provide
10032-778: The paper industry a quick on-line fiber size measurement system. A somewhat different implementation was demonstrated at Pennsylvania State University using a microchip which generated a pair of perpendicular standing surface acoustic waves allowing to position particles equidistant to each other on a grid. This experiment, called acoustic tweezers , can be used for applications in material sciences, biology, physics, chemistry and nanotechnology. Ultrasonic cleaners , sometimes mistakenly called supersonic cleaners , are used at frequencies from 20 to 40 kHz for jewellery, lenses and other optical parts, watches, dental instruments , surgical instruments , diving regulators and industrial parts. An ultrasonic cleaner works mostly by energy released from
10146-440: 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
10260-436: 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
10374-553: 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
10488-442: 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)
10602-650: 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
10716-423: The required ultrasonic exposure parameters. After this phase is complete, the process is transferred to a pilot (bench) scale for flow-through pre-production optimization and then to an industrial scale for continuous production. During these scale-up steps, it is essential to make sure that all local exposure conditions (ultrasonic amplitude, cavitation intensity, time spent in the active cavitation zone, etc.) stay
10830-428: 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
10944-480: The same. If this condition is met, the quality of the final product remains at the optimized level, while the productivity is increased by a predictable "scale-up factor". The productivity increase results from the fact that laboratory, bench and industrial-scale ultrasonic processor systems incorporate progressively larger ultrasonic horns , able to generate progressively larger high-intensity cavitation zones and, therefore, to process more material per unit of time. This
11058-488: The science of sound , starts as far back as Pythagoras in the 6th century BC, who wrote on the mathematical properties of stringed instruments . Echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound, not vision. Francis Galton in 1893 invented the Galton whistle , an adjustable whistle that produced ultrasound, which he used to measure
11172-518: The signals, which may be because of the considerable variation of age-related deterioration in the upper hearing threshold. Bats use a variety of ultrasonic ranging ( echolocation ) techniques to detect their prey. They can detect frequencies beyond 100 kHz, possibly up to 200 kHz. Many insects have good ultrasonic hearing, and most of these are nocturnal insects listening for echolocating bats. These include many groups of moths , beetles , praying mantises and lacewings . Upon hearing
11286-667: 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
11400-604: 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
11514-421: The success of such devices for these purposes. An ultrasonic level or sensing system requires no contact with the target. For many processes in the medical, pharmaceutical, military and general industries this is an advantage over inline sensors that may contaminate the liquids inside a vessel or tube or that may be clogged by the product. Both continuous wave and pulsed systems are used. The principle behind
11628-547: The thickness of objects. Frequencies of 2 to 10 MHz are common, but for special purposes other frequencies are used. Inspection may be manual or automated and is an essential part of modern manufacturing processes. Most metals can be inspected as well as plastics and aerospace composites . Lower frequency ultrasound (50–500 kHz) can also be used to inspect less dense materials such as wood, concrete and cement . Ultrasound inspection of welded joints has been an alternative to radiography for nondestructive testing since
11742-495: The transmitter as an echo and can be detected through the receiver path. By measuring the difference in time between the pulse being transmitted and the echo being received, it is possible to determine the distance. The measured travel time of Sonar pulses in water is strongly dependent on the temperature and the salinity of the water. Ultrasonic ranging is also applied for measurement in air and for short distances. For example, hand-held ultrasonic measuring tools can rapidly measure
11856-467: The ultrasound can cover a wide area from a single point. The flow in pipes or open channels can be measured by ultrasonic flowmeters, which measure the average velocity of flowing liquid. In rheology , an acoustic rheometer relies on the principle of ultrasound. In fluid mechanics , fluid flow can be measured using an ultrasonic flow meter . Ultrasonic testing is a type of nondestructive testing commonly used to find flaws in materials and to measure
11970-594: The ultrasound; the top end of a dog's hearing range is about 45 kHz, while a cat's is 64 kHz. The wild ancestors of cats and dogs evolved this higher hearing range to hear high-frequency sounds made by their preferred prey, small rodents. A dog whistle is a whistle that emits ultrasound, used for training and calling dogs. The frequency of most dog whistles is within the range of 23 to 54 kHz. Toothed whales , including dolphins , can hear ultrasound and use such sounds in their navigational system ( biosonar ) to orient and to capture prey. Porpoises have
12084-468: 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
12198-415: 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
12312-420: 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)
12426-585: 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
12540-415: 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
12654-519: 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
12768-481: Was the Polaroid SX-70 camera, which included a lightweight transducer system to focus the camera automatically. Polaroid later licensed this ultrasound technology and it became the basis of a variety of ultrasonic products. A common ultrasound application is an automatic door opener, where an ultrasonic sensor detects a person's approach and opens the door. Ultrasonic sensors are also used to detect intruders;
12882-457: 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
12996-532: 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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