Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. Fabrication, when used as an industrial term applies to the building of Machines, Structures or Process equipment for the chemical or fertilizer sector In Science, a process is every sequence of changes of a real object/body which is observable using Scientific method. The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across A thermoplastic is a Plastic that Melts to a liquid when heated and freezes to a Brittle, very Glassy state when cooled sufficiently Coalescence is the process by which two or more droplets or particles merge during contact to form a single daughter droplet (or bubble This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld puddle) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. Melting is a process that results in the phase change of a substance from a Solid to a Liquid. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the workpieces to form a bond between them, without melting the workpieces. Soldering is a process in which two or more Metal items are joined together by melting and flowing a filler metal into the joint the filler metal having a relatively low Brazing is a joining process whereby a Filler metal or Alloy is heated to melting temperature above - or by the traditional definition in the United States
Many different energy sources can be used for welding, including a gas flame, an electric arc, a laser, an electron beam, friction, and ultrasound. Energy development is the ongoing effort to provide sufficient Primary energy sources and secondary Energy forms to meet civilization's needs Fire is the heat and light energy released during a Chemical reaction, in particular a combustion reaction. An electric arc is an Electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Friction welding (FW is a class of solid-state Welding processes that generates heat through mechanical friction between a moving workpiece and a stationary component with Not to be confused with Supersonic. Ultrasound is cyclic Sound pressure with a Frequency greater than the upper While often an industrial process, welding can be done in many different environments, including open air, underwater and in space. Underwater welding refers to a number of distinct Welding processes that are performed Underwater. Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another Regardless of location, however, welding remains dangerous, and precautions must be taken to avoid burns, electric shock, eye damage, poisonous fumes, and overexposure to ultraviolet light. "Electrocute" redirects here For the band see Electrocute (band. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays
Until the end of the 19th century, the only welding process was forge welding, which blacksmiths had used for centuries to join metals by heating and pounding them. Forge welding is a Welding process of heating two or more pieces of Metal and then hammering them together Arc welding and oxyfuel welding were among the first processes to develop late in the century, and resistance welding followed soon after. Arc welding uses a Welding power supply to create an Electric arc between an electrode and the base material to melt the metals at the welding point Concerning a. " for the verdict on this matter --> Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding Resistance welding refers to a group of Welding processes that produce coalescence of Faying surfaces where heat to form the weld is generated by the resistance Welding technology advanced quickly during the early 20th century as World War I and World War II drove the demand for reliable and inexpensive joining methods. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including 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. Shielded metal arc welding (SMAW, also known as manual metal arc (MMA welding or informally as stick welding, is a manual Arc welding process that uses Gas metal arc welding (GMAW, sometimes referred to by its subtypes metal inert gas (MIG welding or metal active gas (MAG welding, is a semi-automatic or automatic Submerged Arc Welding (SAW is a common Arc welding process Originally devolved by the Linde - Union Carbide Company Flux-cored arc welding (FCAW is a semi-automatic or automatic Arc welding process Electroslag welding (ESW is a highly productive single pass Welding process for thick (greater than 25mm up to about 300mm materials in a vertical or close Developments continued with the invention of laser beam welding and electron beam welding in the latter half of the century. Laser beam welding (LBW is a Welding technique used to join multiple pieces of metal through the use of a Laser. Electron beam welding (EBW is a fusion Welding process in which a beam of high-velocity Electrons is applied to the materials being joined Today, the science continues to advance. Robot welding is becoming more commonplace in industrial settings, and researchers continue to develop new welding methods and gain greater understanding of weld quality and properties. Robot welding is the use of mechanized programmable tools ( Robots, which completely automate a Welding process by both performing the weld and handling the part
The history of joining metals goes back several millennia, with the earliest examples of welding from the Bronze Age and the Iron Age in Europe and the Middle East. The term Bronze Age refers to a period in human cultural development when the most advanced Metalworking (at least in systematic and widespread use included techniques for This article is about the archaeological period known as the Iron Age for the mythological Iron Age see Ages of Man. The Middle East is a Subcontinent with no clear boundaries often used as a synonym to Near East, in opposition to Far East. Welding was used in the construction of the Iron pillar in Delhi, India, erected about 310 and weighing 5. The iron pillar of Delhi, India, located in the Qutb complex, is an important testimony of the History of metallurgy in the Indian subcontinent Delhi (दिल्ली ਦਿੱਲੀ دلی d̪ɪlːiː sometimes referred to as Dilli) is the second largest metropolis of India, with a population India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country 4 metric tons. This article is about the tonne or metric ton For other tons see Ton.  The Middle Ages brought advances in forge welding, in which blacksmiths pounded heated metal repeatedly until bonding occurred. Forge welding is a Welding process of heating two or more pieces of Metal and then hammering them together In 1540, Vannoccio Biringuccio published De la pirotechnia, which includes descriptions of the forging operation. Vannoccio Biringuccio, sometimes spelt Vannocio Biringuccio, (1480–c De la Pirotechnia is considered to be the first book on Metallurgy to have been published in Europe. Renaissance craftsmen were skilled in the process, and the industry continued to grow during the following centuries. The Renaissance (from French Renaissance, meaning "rebirth" Italian: Rinascimento, from re- "again" and nascere  Welding, however, was transformed during the 19th century—in 1800, Sir Humphry Davy discovered the electric arc, and advances in arc welding continued with the inventions of metal electrodes by a Russian, Nikolai Slavyanov, and an American, C. L. Coffin in the late 1800s, even as carbon arc welding, which used a carbon electrode, gained popularity. Sir Humphry Davy 1st Baronet FRS MRIA (17 December 1778 &ndash 29 May 1829 was a British Chemist and inventor An electric arc is an Electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive CL Coffin of Detroit was awarded for an Arc welding process using a metal Electrode. Carbon Arc Welding ( CAW) is a process which produces coalescence of metals by heating them with an arc between a nonconsumable Carbon ( Graphite) Electrode Around 1900, A. P. Strohmenger released a coated metal electrode in Britain, which gave a more stable arc, and in 1919, alternating current welding was invented by C. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant J. Holslag, but did not become popular for another decade. 
Resistance welding 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. Resistance welding refers to a group of Welding processes that produce coalescence of Faying surfaces where heat to form the weld is generated by the resistance Elihu Thomson ( March 29, 1853  – March 13, 1937) was an engineer and Inventor who was instrumental in the founding Thermite welding was invented in 1893, and around that time, another process, oxyfuel welding, became well established. Thermite is a Pyrotechnic composition of Aluminium powder and a metal oxide which produces an Aluminothermic reaction known as a Concerning a. " for the verdict on this matter --> Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding Acetylene was discovered in 1836 by Edmund Davy, but its use was not practical in welding until about 1900, when a suitable blowtorch was developed. Acetylene ( IUPAC name ethyne), C2H2 is a Hydrocarbon belonging to the group of Alkynes It is the simplest of all alkynes Edmund Davy FRS (1785 - 5 Nov[[ 857]] was a professor of Chemistry at the Royal Cork Institution from 1813 and professor of chemistry at the Concerning a. " for the verdict on this matter --> Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding  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 metal coverings (known as flux) for the electrode that stabilize the arc and shield the base material from impurities continued to be developed. In Metallurgy, a flux is a chemical cleaning agent which facilitates Soldering, Brazing, and Welding by removing Oxidation from 
World War I caused a major surge in the use of welding processes, with the various military powers attempting to determine which of the several new welding processes would be best. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All The British primarily used arc welding, even constructing a ship, the Fulagar, with an entirely welded hull. The Americans were more hesitant, but began to recognize the benefits of arc welding when the process allowed them to repair their ships quickly after German attacks in the New York Harbor at the beginning of the war. The Second Happy Time was the informal name for a phase in the Second Battle of the Atlantic during which Axis Submarines attacked Merchant shipping New York Harbor, a geographic term refers collectively to the rivers bays and tidal estuaries near the mouth of the Hudson River in the vicinity of New York City Arc welding was first applied to aircraft during the war as well, as some German airplane fuselages were constructed using the process.  Also noteworthy is the first welded road bridge in the world built across the river Słudwia Maurzyce near Łowicz, Poland) in 1929, but designed by Stefan Bryła of the Warsaw University of Technology in 1927. A bridge is a Structure built to span a Gorge, Valley, Road, railroad track, River, Body of water Łowicz Radomsko County Łowicz is a town in central Poland with 30383 inhabitants (2004 Stefan Bryła (b August 17, 1886 in Kraków - December 3, 1943 in Warsaw, Poland) was a Polish construction Warsaw University of Technology ( Polish: Politechnika Warszawska) is the largest academic school of technology in Poland, and one of the largest in 
During the 1920s, major 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 the atmosphere. Shielding gases are inert or semi- Inert gases that are commonly used in several Welding processes most notably Gas metal arc welding and Gas tungsten Porosity and brittleness were the primary problems, and the solutions that developed included the use of hydrogen, argon, and helium as welding atmospheres. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 This article pertains to the chemical element For other uses see Argon (disambiguation. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical  During the following decade, further advances allowed for the welding of reactive metals like aluminum and magnesium. WikipediaNaming Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 This, in conjunction with developments in automatic welding, alternating current, and fluxes fed a major expansion of arc welding during the 1930s and then during World War II. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including 
During the middle of the century, many new welding methods were invented. 1930 saw the release of stud welding, which soon became popular in shipbuilding and construction. Stud welding is a form of Spot welding where a bolt or specially formed nut is welded onto another metal part Submerged arc welding was invented the same year, and continues to be popular today. Submerged Arc Welding (SAW is a common Arc welding process Originally devolved by the Linde - Union Carbide Company 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. Gas tungsten arc welding ( GTAW) also known as tungsten inert gas (TIG welding, is an Arc welding process that uses a nonconsumable Tungsten Gas metal arc welding (GMAW, sometimes referred to by its subtypes metal inert gas (MIG welding or metal active gas (MAG welding, is a semi-automatic or automatic Ferrous, in the chemical science realm indicates a bivalent iron compound (+2 oxidation state (as opposed to Ferric, which indicates a trivalent iron compound (+3 oxidation Shielded metal arc welding was developed during the 1950s, using a flux coated consumable electrode, and it quickly became the most popular metal arc welding process. Shielded metal arc welding (SMAW, also known as manual metal arc (MMA welding or informally as stick welding, is a manual Arc welding process that uses 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. Flux-cored arc welding (FCAW is a semi-automatic or automatic Arc welding process Plasma arc welding (PAW is an arc Welding process similar to Gas tungsten arc welding (GTAW Electroslag welding was introduced in 1958, and it was followed by its cousin, electrogas welding, in 1961. Electroslag welding (ESW is a highly productive single pass Welding process for thick (greater than 25mm up to about 300mm materials in a vertical or close Electrogas welding (EGW is a continuous vertical position Arc welding process developed in 1961, in which an arc is struck between a consumable Electrode 
Other recent developments in welding include the 1958 breakthrough of electron beam welding, making deep and narrow welding possible through the concentrated heat source. Electron beam welding (EBW is a fusion Welding process in which a beam of high-velocity Electrons is applied to the materials being joined 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. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. Laser beam welding (LBW is a Welding technique used to join multiple pieces of metal through the use of a Laser. Both of these processes, however, continue to be quite expensive due the high cost of the necessary equipment, and this has limited their applications. 
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. Arc welding uses a Welding power supply to create an Electric arc between an electrode and the base material to melt the metals at the welding point A welding power supply is a device that provides an Electric current to perform Welding. They can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes. Direct current ( DC) is the unidirectional flow of Electric charge. An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e The welding region 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. "Inert gases" is also used in a narrower sense for Noble gases An inert gas is any Gas that is not reactive with elements Shielding gases are inert or semi- Inert gases that are commonly used in several Welding processes most notably Gas metal arc welding and Gas tungsten
To supply the electrical energy necessary for arc welding processes, a number of different power supplies can be used. The most common classification is constant current power supplies and constant voltage power supplies. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical In arc welding, 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 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 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 in arc welding also plays an important role in welding. Consumable electrode processes such as shielded metal arc welding and gas metal arc welding generally use direct current, but the electrode can be charged either positively or negatively. In welding, the positively charged anode will have a greater heat concentration, and as a result, changing the polarity of the electrode has an impact on weld properties. An anode is an Electrode through which Electric current flows into a polarized electrical device 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.  Nonconsumable 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 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 crossing, has been addressed with the invention of special power units that produce a square wave pattern instead of the normal sine wave, making rapid zero crossings possible and minimizing the effects of the problem. A square wave is a kind of Non-sinusoidal waveform, most typically encountered in Electronics and Signal processing. 
One of the most common types of arc welding is shielded metal arc welding (SMAW), which is also known as manual metal arc welding (MMA) or stick welding. Shielded metal arc welding (SMAW, also known as manual metal arc (MMA welding or informally as stick welding, is a manual Arc welding process that uses Electric current is used to strike an arc between the base material and consumable electrode rod, which is made of steel and is covered with a flux that protects the weld area from oxidation and contamination by producing CO2 gas during the welding process. In Metallurgy, a flux is a chemical cleaning agent which facilitates Soldering, Brazing, and Welding by removing Oxidation from Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single 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 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, nickel, aluminium, copper, and other metals. Cast iron usually refers to grey cast iron, but identifies a large group of Ferrous Alloys which solidify with a Eutectic. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 WikipediaNaming Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Inexperienced operators may find it difficult to make good out-of-position welds with this process.
Gas metal arc welding (GMAW), also known as metal inert gas or MIG welding, 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. Gas metal arc welding (GMAW, sometimes referred to by its subtypes metal inert gas (MIG welding or metal active gas (MAG welding, is a semi-automatic or automatic As with SMAW, reasonable operator proficiency can be achieved with modest training. Since the electrode is continuous, welding speeds are greater for GMAW than for SMAW. Also, the smaller arc size compared to the shielded metal arc welding process makes it easier to make out-of-position welds (e. Shielded metal arc welding (SMAW, also known as manual metal arc (MMA welding or informally as stick welding, is a manual Arc welding process that uses g. , overhead joints, as would be welded underneath a structure).
The equipment required to perform the GMAW process is more complex and expensive than that required for SMAW, and requires a more complex setup procedure. Therefore, GMAW is less portable and versatile, and due to the use of a separate shielding gas, is not particularly suitable for outdoor work. However, owing to the higher average rate at which welds can be completed, GMAW is well suited to production welding. The process can be applied to a wide variety of metals, both ferrous and non-ferrous. 
A related process, flux-cored arc welding (FCAW), uses similar equipment but uses wire consisting of a steel electrode surrounding a powder fill material. Flux-cored arc welding (FCAW is a semi-automatic or automatic Arc welding process This cored wire 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 (also sometimes erroneously referred to as heliarc welding), is a manual welding process that uses a nonconsumable tungsten electrode, an inert or semi-inert gas mixture, and a separate filler material. Gas tungsten arc welding ( GTAW) also known as tungsten inert gas (TIG welding, is an Arc welding process that uses a nonconsumable Tungsten Gas tungsten arc welding ( GTAW) also known as tungsten inert gas (TIG welding, is an Arc welding process that uses a nonconsumable Tungsten Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 Especially useful for welding thin materials, this method 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. In Metallurgy, stainless steel is defined as a Steel Alloy with a minimum of 11 It is often used when quality welds are extremely important, such as in bicycle, aircraft and naval applications. The bicycle, cycle, or bike is a pedal-driven, human-powered vehicle with two wheels attached to a frame, one behind  A related process, plasma arc welding, also uses a tungsten electrode but uses plasma gas to make the arc. Plasma arc welding (PAW is an arc Welding process similar to Gas tungsten arc welding (GTAW 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 furthermore, it is much faster. It can be applied to all of the same materials as GTAW except magnesium, and automated welding of stainless steel is one important application of the process. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 A variation of the process is plasma cutting, an efficient steel cutting process. This article is about the common Manufacturing process For various fictional weapons see Plasma rifle and Directed-energy weapon. 
Submerged arc welding (SAW) is a high-productivity welding method in which the arc is struck beneath a covering layer of flux. Submerged Arc Welding (SAW is a common Arc welding process Originally devolved by the Linde - Union Carbide Company 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 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, carbon arc welding, electroslag welding, electrogas welding, and stud arc welding. Carbon Arc Welding ( CAW) is a process which produces coalescence of metals by heating them with an arc between a nonconsumable Carbon ( Graphite) Electrode Electroslag welding (ESW is a highly productive single pass Welding process for thick (greater than 25mm up to about 300mm materials in a vertical or close Electrogas welding (EGW is a continuous vertical position Arc welding process developed in 1961, in which an arc is struck between a consumable Electrode Stud welding is a form of Spot welding where a bolt or specially formed nut is welded onto another metal part
The most common gas welding process is oxyfuel welding, also known as oxyacetylene welding. Concerning a. " for the verdict on this matter --> Oxy-fuel welding (commonly called oxyacetylene welding, oxy 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 is still widely used for welding pipes and tubes, as well as repair work. It is also frequently well-suited, and favored, for fabricating some types of metal-based artwork. Oxyfuel equipment is versatile, lending itself not only to some sorts of iron or steel welding but also to brazing, braze-welding, metal heating (for bending and forming), and also oxyfuel cutting.
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. Acetylene ( IUPAC name ethyne), C2H2 is a Hydrocarbon belonging to the group of Alkynes It is the simplest of all alkynes Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 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 the welding of high alloy steels. A similar process, generally called oxyfuel cutting, is used to cut metals.  Other gas welding methods, such as air acetylene welding, oxygen hydrogen welding, and pressure gas welding are quite similar, generally differing only in the type of gases used. A water torch is sometimes used for precision welding of small items such as jewelry. Gas welding is also used in plastic welding, though the heated substance is air, and the temperatures are much lower. Plastic welding is the process of Welding Plastic parts together
Resistance welding involves the generation of heat by passing current through the resistance caused by the contact between two or more metal surfaces. Resistance welding refers to a group of Welding processes that produce coalescence of Faying surfaces where heat to form the weld is generated by the resistance Small pools of molten metal are formed at the weld area as high current (1000–100,000 A) is passed through the metal. The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second 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. Spot welding is a type of Resistance welding used to weld various sheet Metal products Two electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. The advantages of 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. An industrial robot is officially defined by ISO as an automatically controlled reprogrammable multipurpose manipulator programmable in three or more axes. A specialized process, called shot welding, can be used to spot weld stainless steel. Shot welding is a specific type of Spot welding used to join two pieces of Metal together In Metallurgy, stainless steel is defined as a Steel Alloy with a minimum of 11
Like spot welding, seam welding relies on two electrodes to apply pressure and current to join metal sheets. Resistance Seam Welding is a Resistance welding process that produces a weld at the Faying surfaces of overlapped parts along a length of a joint However, instead of pointed electrodes, wheel-shaped electrodes roll along and often feed 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 flash welding, projection welding, and upset welding. Flash Welding is a form of resistance welding that involves pressing two ends together while simultaneously running a current between them Upset welding is a special way of Welding, in which two pieces of material are forged together at elevated temperatures 
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. Laser beam welding (LBW is a Welding technique used to join multiple pieces of metal through the use of a Laser. Electron beam welding (EBW is a fusion Welding process in which a beam of high-velocity Electrons is applied to the materials being joined The two processes are quite similar, differing most notably in their source of power. Laser beam welding employs 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 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 Hybrid welding is a type of welding process that combines the principles of Laser beam welding and Arc welding. 
Like the first welding process, forge welding, some modern welding methods do not involve the melting of the materials being joined. Forge welding is a Welding process of heating two or more pieces of Metal and then hammering them together One of the most popular, ultrasonic welding, is used to connect thin sheets or wires made of metal or thermoplastic by vibrating them at high frequency and under high pressure. Ultrasonic welding is an industrial technique whereby high-frequency Ultrasonic acoustic Vibrations are locally applied to workpieces The equipment and methods involved are similar to that of resistance welding, but instead of electric current, vibration provides energy input. Welding metals with this process does not involve melting the materials; instead, the weld is formed by introducing mechanical vibrations horizontally under pressure. When welding plastics, the materials should have similar melting temperatures, and the vibrations are introduced vertically. Ultrasonic welding 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. Explosion Welding ( EXW) is a solid state Process where Welding is accomplished by accelerating one of the components at extremely high velocity The energy from the impact plasticizes the materials, forming a weld, even though only a limited amount of heat is generated. The process is commonly used for welding dissimilar materials, such as the welding of aluminum with steel in ship hulls or compound plates. Other solid-state welding processes include co-extrusion welding, cold welding, diffusion welding, friction welding (including friction stir welding), high frequency welding, hot pressure welding, induction welding, and roll welding. Cold or contact welding was first recognized as a general materials phenomenon in the 1940s Operation definition Diffusion welding (DFW is a solid state welding process by which two dissimilar metals can be bond together Friction welding (FW is a class of solid-state Welding processes that generates heat through mechanical friction between a moving workpiece and a stationary component with Friction-stir welding ( FSW) is a solid-state joining process (meaning the metal is not melted during the process and is used for applications Induction welding is a form of Welding that uses Electromagnetic induction to heat the workpiece 
Welds can be geometrically prepared in many different ways. The five basic types of weld joints are the butt joint, lap joint, corner joint, edge joint, and T-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 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. 
Often, particular joint designs are used exclusively or almost exclusively by certain welding processes. For example, resistance spot welding, laser beam welding, and electron beam welding are most frequently performed on lap joints. However, some welding methods, like shielded metal arc welding, are extremely versatile and can weld virtually any type of joint. Additionally, some processes can be used to make multipass welds, in which one weld 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 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. The heat-affected zone (HAZ is the area of base material either a Metal or a Thermoplastic, which has had its microstructure and properties altered by 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. 
Most often, the major metric used for judging the quality of a weld is its strength and the strength of the material around it. Many distinct factors influence this, including the welding method, the amount and concentration of energy input, the base material, the filler material, the flux material, the design of the joint, and the interactions between all these factors. To test the quality of a weld, either destructive or nondestructive testing methods are commonly used to verify that welds are defect-free, have acceptable levels of residual stresses and distortion, and have acceptable heat-affected zone (HAZ) properties. In destructive testing, tests are carried out to the specimen's failure in order to understand a specimen's structural performance or material behaviour under different loads Nondestructive testing ( NDT) also called nondestructive examination ( NDE) and nondestructive inspection ( NDI) is testing that does Welding codes and specifications exist to guide welders in proper welding technique and in how to judge the quality of welds.
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 the base material plays a large role—if the diffusivity is high, the material cooling rate is high and the HAZ is relatively small. In Heat transfer analysis thermal diffusivity (symbol \alpha\ but note that the symbols \kappa D and k are all commonly 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 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 joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force. The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second The efficiency is dependent on 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. 
Welding methods that involve the melting of metal at the site of the joint necessarily are prone to shrinkage as the heated metal cools. Shrinkage, in turn, can introduce residual stresses and both longitudinal and rotational distortion. Distortion can pose a major problem, since the final product is not the desired shape. To alleviate rotational distortion, the workpieces can be offset, so that the welding results in a correctly shaped piece.  Other methods of limiting distortion, such as clamping the workpieces in place, cause the buildup of residual stress in the heat-affected zone of the base material. These stresses can reduce the strength of the base material, and can lead to catastrophic failure through cold cracking, as in the case of several of the Liberty ships. Cold cracking is a defect that occurs in Welding and requires all the following preconditions susceptible microstructure ( e History and service In 1936 the American Merchant Marine Act was passed to subsidize the annual construction of 50 commercial merchant vessels to be used in wartime by Cold cracking is limited to steels, and is associated with the formation of martensite as the weld cools. Steel 035 water quenchedpng|thumb|200px|035%C Steel water-quenched from 870°C]] Martensite, named after the German metallurgist Adolf Martens (1850–1914 The cracking occurs in the heat-affected zone of the base material. To reduce the amount of distortion and residual stresses, the amount of heat input should be limited, and the welding sequence used should not be from one end directly to the other, but rather in segments. The other type of cracking, hot cracking or solidification cracking, can occur with all metals, and happens in the fusion zone of a weld. To diminish the probability of this type of cracking, excess material restraint should be avoided, and a proper filler material should be utilized. 
The quality of a weld is also dependent on the combination of materials used for the base material and the filler material. Not all metals are suitable for welding, and not all filler metals work well with acceptable base materials.
The weldability of steels is inversely proportional to a property known as the hardenability of the steel, which measures the probability of forming martensite during welding or heat treatment. The weldability of a material refers to its ability to be welded. Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 The hardenability of a Metal Alloy is its capability to be hardened by Heat treatment. Steel 035 water quenchedpng|thumb|200px|035%C Steel water-quenched from 870°C]] Martensite, named after the German metallurgist Adolf Martens (1850–1914 The hardenability of steel depends on its chemical composition, with greater quantities of carbon and other alloying elements resulting in a higher hardenability and thus a lower weldability. An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has In order to be able to judge alloys made up of many distinct materials, a measure known as the equivalent carbon content is used to compare the relative weldabilities of different alloys by comparing their properties to a plain carbon steel. The equivalent carbon content of a Steel Alloy refers to method of measuring the maximum Hardness and the Weldability of the alloy based on the Carbon steel, also called plain carbon steel, is Steel where the main alloying constituent is Carbon. The effect on weldability of elements like chromium and vanadium, while not as great as carbon, is more significant than that of copper and nickel, for example. Chromium (ˈkroʊmiəm is a Chemical element which has the symbol Cr and Atomic number 24 Vanadium (vəˈneɪdiəm is a Chemical element that has the symbol V and Atomic number 23 Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 As the equivalent carbon content rises, the weldability of the alloy decreases.  The disadvantage to using plain carbon and low-alloy steels is their lower strength—there is a trade-off between material strength and weldability. High strength, low-alloy steels were developed especially for welding applications during the 1970s, and these generally easy to weld materials have good strength, making them ideal for many welding applications. High strength low alloy ( HSLA) steel is a type of Steel alloy that provides better mechanical properties or greater resistance to corrosion than Carbon 
Stainless steels, because of their high chromium content, tend to behave differently with respect to weldability than other steels. In Metallurgy, stainless steel is defined as a Steel Alloy with a minimum of 11 Austenitic grades of stainless steels tend to be the most weldable, but they are especially susceptible to distortion due to their high coefficient of thermal expansion. Some alloys of this type are prone to cracking and reduced corrosion resistance as well. Hot cracking is possible if the amount of ferrite in the weld is not controlled—to alleviate the problem, an electrode is used that deposits a weld metal containing a small amount of ferrite. Ferrite or alpha iron ( α-Fe) is a Materials science term for Iron, or a Solid solution with iron as the main constituent with a Other types of stainless steels, such as ferritic and martensitic stainless steels, are not as easily welded, and must often be preheated and welded with special electrodes. 
The weldability of aluminum alloys varies significantly, depending on the chemical composition of the alloy used. WikipediaNaming Aluminum alloys are susceptible to hot cracking, and to combat the problem, welders increase the welding speed to lower the heat input. Preheating reduces the temperature gradient across the weld zone and thus helps reduce hot cracking, but it can reduce the mechanical properties of the base material and should not be used when the base material is restrained. The design of the joint can be changed as well, and a more compatible filler alloy can be selected to decrease the likelihood of hot cracking. Aluminum alloys should also be cleaned prior to welding, with the goal of removing all oxides, oils, and loose particles from the surface to be welded. An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element An oil is a substance that is in a viscous Liquid state ( "oily") at ambient temperatures or slightly warmer and is This is especially important because of an aluminum weld's susceptibility to porosity due to hydrogen and dross due to oxygen. Porosity is a measure of the void spaces in a material and is measured as a fraction between 0–1 or as a Percentage between 0–100% Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Dross is a Mass of Solid impurities floating on a molten metal Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 
While many welding applications are done in controlled environments such as factories and repair shops, some welding processes are commonly used in a wide variety of conditions, such as open air, underwater, and vacuums (such as space). This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. In open-air applications, such as construction and outdoors repair, shielded metal arc welding is the most common process. Processes that employ inert gases to protect the weld cannot be readily used in such situations, because unpredictable atmospheric movements can result in a faulty weld. Shielded metal arc welding is also often used in underwater welding in the construction and repair of ships, offshore platforms, and pipelines, but others, such as flux cored arc welding and gas tungsten arc welding, are also common. Underwater welding refers to a number of distinct Welding processes that are performed Underwater. Welding in space is also possible—it was first attempted in 1969 by Russian cosmonauts, when they performed experiments to test shielded metal arc welding, plasma arc welding, and electron beam welding in a depressurized environment. Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending Further testing of these methods was done in the following decades, and today researchers continue to develop methods for using other welding processes in space, such as laser beam welding, resistance welding, and friction welding. Friction welding (FW is a class of solid-state Welding processes that generates heat through mechanical friction between a moving workpiece and a stationary component with Advances in these areas could prove indispensable for projects like the construction of the International Space Station, which will likely rely heavily on welding for joining in space the parts that were manufactured on Earth. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 
Welding, without the proper precautions, can be a dangerous and unhealthy practice. However, with the use of new technology and proper protection, risks of injury and death associated with welding can be greatly reduced. Because many common welding procedures involve an open electric arc or flame, the risk of burns is significant. To prevent them, welders wear personal protective equipment in the form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat and flames. A welder (also weldor, which term distinguishes the Tradesman from the equipment used to make welds is a Tradesman who specialises in Welding Personal protective equipment (PPE refers to protective Clothing, Helmets, Goggles, or other garment designed to protect the wearer's body or Leather is a material created through the Tanning of hides and Skins of Animals primarily Cattlehide The Tanning process A glove ( Middle English from Old English glof) is a type of Garment (and more specifically a Fashion Additionally, the brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Arc eye, also known as welder's flash, bake eyes, corneal flash burns, or flash burns, is a painful ocular condition sometimes experienced by Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays The cornea is the transparent front part of the Eye that covers the iris, Pupil, and Anterior chamber. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Goggles and welding helmets with dark face plates are worn to prevent this exposure, and in recent years, new helmet models have been produced that feature a face plate that self-darkens upon exposure to high amounts of UV light. Goggles or safety glasses are forms of protective eyewear that usually enclose or protect the eye area in order to prevent particulates water or chemicals from Welding helmets are headgear used when performing certain types of Welding to protect the eyes face and neck from flash burn Ultraviolet light, sparks and heat To protect bystanders, translucent welding curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets. An optical filter is a device which selectively transmits light having certain properties (often a particular range of Wavelengths that is range of Colours 
Welders are also often exposed to dangerous gases and particulate matter. Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides, which in some cases can lead to medical conditions like metal fume fever. Smoke is the collection of airborne solid and liquid Particulates and Gases ref> ''Smoke Production and Properties'' - SFPE Handbook of Fire Protection Engineering An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element Metal fume fever is illness caused primarily by exposure to certain metal fumes The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Toxicity is the degree to which a substance is able to damage an exposed organism Additionally, many processes produce fumes and various gases, most commonly carbon dioxide, ozone and heavy metals, that can prove dangerous without proper ventilation and training. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single OZONE is an object oriented Operating system written in the C programming language. Furthermore, because the use of compressed gases and flames in many welding processes poses an explosion and fire risk, some common precautions include limiting the amount of oxygen in the air and keeping combustible materials away from the workplace. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the  Welding fume extractors are often used to remove the fume from the source and filter the fumes through a HEPA filter.
As an industrial process, the cost of welding plays a crucial role in manufacturing decisions. Many different variables affect the total cost, including equipment cost, labor cost, material cost, and energy cost. Electric power is defined as the rate at which Electrical energy is transferred by an Electric circuit. Depending on the process, equipment cost can vary, from inexpensive for methods like shielded metal arc welding and oxyfuel welding, to extremely expensive for methods like laser beam welding and electron beam welding. Because of their high cost, they are only used in high production operations. Similarly, because automation and robots increase equipment costs, they are only implemented when high production is necessary. Labor cost depends on the deposition rate (the rate of welding), the hourly wage, and the total operation time, including both time welding and handling the part. The cost of materials includes the cost of the base and filler material, and the cost of shielding gases. Finally, energy cost depends on arc time and welding power demand.
For manual welding methods, labor costs generally make up the vast majority of the total cost. As a result, many cost-savings measures are focused on minimizing the operation time. To do this, welding procedures with high deposition rates can be selected, and weld parameters can be fine-tuned to increase welding speed. Mechanization and automatization are often implemented to reduce labor costs, but this frequently increases the cost of equipment and creates additional setup time. Material costs tend to increase when special properties are necessary, and energy costs normally do not amount to more than several percent of the total welding cost. 
In recent years, in order to minimize labor costs in high production manufacturing, industrial welding has become increasingly more automated, most notably with the use of robots in resistance spot welding (especially in the automotive industry) and in arc welding. In robot welding, mechanized devices both hold the material and perform the weld, and at first, spot welding was its most common application. Robot welding is the use of mechanized programmable tools ( Robots, which completely automate a Welding process by both performing the weld and handling the part But robotic arc welding has been increasing in popularity as technology has advanced. Other key areas of research and development include the welding of dissimilar materials (such as steel and aluminum, for example) and new welding processes, such as friction stir, magnetic pulse, conductive heat seam, and laser-hybrid welding. Friction-stir welding ( FSW) is a solid-state joining process (meaning the metal is not melted during the process and is used for applications Magnetic pulse welding is a Welding process in which a very high AC current (the " primary current " is passed through a Conductive coil Laser Hybrid welding is a type of welding process that combines the principles of Laser beam welding and Arc welding. Furthermore, progress is desired in making more specialized methods like laser beam welding practical for more applications, such as in the aerospace and automotive industries. Researchers also hope to better understand the often unpredictable properties of welds, especially microstructure, residual stresses, and a weld's tendency to crack or deform. Residual stresses are stresses that remain after the original cause of the stresses (external forces heat gradient has been removed