Welding

Fabrication process for joining materials

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"Welded" redirects here. For the play, see Welded (play)

Overhead stick welding

Welding is a fabrication process that joins materials, usually metals or thermoplastics, primarily by using high temperature to melt 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 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 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 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 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 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.[1]

Etymology

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The term weld is derived from the Middle English verb well (wæll; plural/present tense: wælle) or welling (wællen), meaning 'to heat' (to 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 . 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 the 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.[2]

The Old English word for welding iron was samod ('to bring together') or samodwellung ('to bring together hot').[3]

The word 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 the most common English words in everyday use are Scandinavian in origin.[4][5]

History

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The iron pillar of Delhi, India

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".[6] Forge welding was used in the construction of the Iron pillar of Delhi, erected in Delhi, India about 310 AD and weighing 5.4 metric tons.[7]

The Middle Ages brought advances in forge welding, in which blacksmiths pounded heated metal repeatedly until bonding occurred. In , Vannoccio Biringuccio published De la pirotechnia, which includes descriptions of the forging operation.[8] Renaissance craftsmen were skilled in the process, and the industry continued to grow during the following centuries.[8]

In , Sir Humphry Davy discovered the short-pulse electrical arc and presented his results in .[9][10][11] In , Russian scientist Vasily Petrov created the continuous electric arc,[11][12][13] and subsequently published "News of Galvanic-Voltaic Experiments" in , in which he described experiments carried out in . Of great importance in this work was the description of a stable arc discharge and the indication of its possible use for many applications, one being melting metals.[14] In , Davy, who was unaware of Petrov's work, rediscovered the continuous electric arc.[10][11] In &#;82 inventors Nikolai Benardos (Russian) and Stanisław Olszewski (Polish)[15] created the first electric arc welding method known as carbon arc welding using carbon electrodes. The advances in arc welding continued with the invention of metal electrodes in the late s by a Russian, Nikolai Slavyanov (), and an American, C. L. Coffin (). Around , A. P. Strohmenger released a coated metal electrode in Britain, which gave a more stable arc. In , Russian scientist Vladimir Mitkevich proposed using a three-phase electric arc for welding. Alternating current welding was invented by C. J. Holslag in , but did not become popular for another decade.[16]

Resistance welding was also developed during the final decades of the 19th century, with the first patents going to Elihu Thomson in , who produced further advances over the next 15 years. Thermite welding was invented in , and around that time another process, oxyfuel welding, became well established. Acetylene was discovered in by Edmund Davy, but its use was not practical in welding until about , when a suitable torch was developed.[17] 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.[18] Flux covering the electrode primarily shields the base material from impurities, but also stabilizes the arc and can add alloying components to the weld metal.[19]

Bridge of Maurzyce

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.[20][21]:&#;142&#; Arc welding was first applied to aircraft during the war as well, as some German airplane fuselages were constructed using the process.[22] Also noteworthy is the first welded road bridge in the world, the Maurzyce Bridge in Poland ().[23]

Acetylene welding on cylinder water jacket, US Army

During the s, significant advances were made in welding technology, including the introduction of automatic welding in , 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. Porosity and brittleness were the primary problems, and the solutions that developed included the use of hydrogen, argon, and helium as welding atmospheres.[24] 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 the s and then during World War II.[25] In , the first all-welded merchant vessel, M/S Carolinian, was launched.

Portable welder being used for Sydney stormwater infrastructure

During the middle of the century, many new welding methods were invented. In , 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 a Russian, Konstantin Khrenov eventually implemented the first underwater electric arc welding. Gas tungsten arc welding, after decades of development, was finally perfected in , and gas metal arc welding followed in , allowing for fast welding of non-ferrous materials but requiring expensive shielding gases. Shielded metal arc welding was developed during the s, using a flux-coated consumable electrode, and it quickly became the most popular metal arc welding process. In , 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 , and it was followed by its cousin, electrogas welding, in .[26] In , the Soviet scientist N. F. Kazakov proposed the diffusion bonding method.[27]

Other recent developments in welding include the breakthrough of electron beam welding, making deep and narrow welding possible through the concentrated heat source. Following the invention of the laser in , 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 . Friction stir welding was invented in by Wayne Thomas at The Welding Institute (TWI, UK) and found high-quality applications all over the world.[28] 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.[29]

Processes

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Gas welding

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The most common gas welding process is oxyfuel welding,[18] 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 is still widely used for welding pipes and tubes, as well as repair work.[18]

The equipment is relatively inexpensive and simple, generally employing the combustion of acetylene in oxygen to produce a welding flame temperature of about  °C ( °F).[18] 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.[18]

Arc welding

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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 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.[30]

Arc welding processes

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One of the most common types of arc welding is shielded metal arc welding (SMAW);[31] 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 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 (CO2) gas during the welding process. The electrode core itself acts as filler material, making a separate filler unnecessary.[31]

Shielded metal arc welding

The process is versatile and can be performed with relatively inexpensive equipment, making it well suited to shop jobs and field work.[31][32] 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.[31] 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.[32]

Diagram of arc and weld area, in shielded metal arc welding:

1. Coating Flow
2. Rod
3. Shield Gas
4. Fusion
5. Base metal
6. Weld metal
7. Solidified Slag

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. Since the electrode is continuous, welding speeds are greater for GMAW than for SMAW.[33]

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 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.[34]

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.[35] 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.[35]

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.[35] A related process, plasma arc welding, also uses 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 is one important application of the process. A variation of the process is plasma cutting, an efficient steel cutting process.[36]

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 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.[37] Other arc welding processes include atomic hydrogen welding, electroslag welding (ESW), electrogas welding, and stud arc welding.[38] ESW 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.

Arc welding power supplies

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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, 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.[39]

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 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.[40] 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 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.[41] 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 a square wave pattern instead of the normal sine wave, making rapid zero crossings possible and minimizing the effects of the problem.[42]

Resistance welding

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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 the metal.[43] In general, resistance welding methods are efficient and cause little pollution, but their applications are somewhat limited and the equipment cost can be high.[43]

Spot welder

Spot welding is a popular resistance welding method used to join overlapping metal sheets of up to 3 mm thick.[43] 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. A specialized process called shot welding, can be used to spot weld stainless steel.[43]

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 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.[43] Other resistance welding methods include butt welding,[44] flash welding, projection welding, and upset welding.[43]

Energy beam welding

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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 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 cladding, and x-ray welding.[45]

Solid-state welding

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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, is used to connect thin sheets or wires made of metal or thermoplastic by vibrating them at high frequency and under high pressure.[47] 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 is commonly used for making electrical connections out of aluminum or copper, and it is also a very common polymer welding process.[47]

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 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.[47]

Other solid-state welding processes include friction welding (including friction stir welding and friction stir spot welding),[48] magnetic pulse welding,[49] co-extrusion welding, cold welding, diffusion bonding, exothermic welding, high frequency welding, hot pressure welding, induction welding, and roll bonding.[47]

Geometry

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Common welding joint types:

1. Square butt joint
2. V butt joint
3. Lap joint
4. T-joint

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 (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 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.[50]

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 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.[51]

The cross-section of a welded butt joint, with the darkest gray representing the weld or fusion zone, the medium gray the heat-affected zone, and the lightest gray the base material.

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. 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.[52]

Quality

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The blue area results from oxidation at a corresponding temperature of 600 °F (316 °C). This is an accurate way to identify temperature, but does not represent the HAZ width. The HAZ is the narrow area that immediately surrounds the welded base metal.

Many distinct factors influence 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.[53]

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 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 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.[53] 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.

Heat-affected zone

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The heat-affected zone (HAZ) 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 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 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.[54][55] To calculate the heat input for arc welding procedures, the following formula can be used:

Q = ( V × I × 60 S × ) × E f f i c i e n c y {\displaystyle Q=\left({\frac {V\times I\times 60}{S\times }}\right)\times {\mathit {Efficiency}}}

where Q = heat input (kJ/mm), V = voltage (V), I = current (A), and S = welding speed (mm/min). 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.[56] Methods of alleviating the stresses and brittleness created in the HAZ include stress relieving and tempering.[57]

One major defect concerning the HAZ would be cracking at the toes , due to the rapid expansion (heating) and contraction (cooling) 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 [58]

Lifetime extension with after treatment methods

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Example: High Frequency Impact Treatment for lifetime extension

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. the durability of many designs increases significantly.

Metallurgy

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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.[59]

Crystalline solids cohesion 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 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.[59]

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 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.[59]

Metallic bonding can be classified as a type of covalent bonding for which the constituent atoms are of the same type and do not combine with one another to form a chemical bond. Atoms will lose an electron(s) forming an array of positive ions. These electrons are shared by the lattice which makes the electron cluster mobile, as the electrons are free to move as well as the ions. For this, it gives metals their relatively high thermal and electrical conductivity as well as being characteristically ductile.[59]

Three of the most commonly used crystal lattice structures in metals are the body-centred cubic, face-centred cubic and close-packed hexagonal. Ferritic steel has a body-centred cubic structure and austenitic steel, non-ferrous metals like aluminium, copper and nickel have the face-centred cubic structure.[59]

Ductility is an important factor in ensuring the integrity of structures by enabling them to sustain local stress concentrations without fracture. In addition, structures are required to be of an acceptable strength, which is related to a material's yield strength. In general, as the yield strength of a material increases, there is a corresponding reduction in fracture toughness.[59]

A reduction in fracture toughness may also be attributed to the embrittlement effect of impurities, or for body-centred cubic metals, from a reduction in temperature. Metals and in particular steels have a transitional temperature range where above this range the metal has acceptable notch-ductility while below this range the material becomes brittle. Within the range, the materials behavior is unpredictable. The reduction in fracture toughness is accompanied by a change in the fracture appearance. When above the transition, the fracture is primarily due to micro-void coalescence, which results in the fracture appearing fibrous. When the temperatures falls the fracture will show signs of cleavage facets. These two appearances are visible by the naked eye. Brittle fracture in steel plates may appear as chevron markings under the microscope. These arrow-like ridges on the crack surface point towards the origin of the fracture.[59]

Fracture toughness is measured using a notched and pre-cracked rectangular specimen, of which the dimensions are specified in standards, for example ASTM E23. There are other means of estimating or measuring fracture toughness by the following: The Charpy impact test per ASTM A370; The crack-tip opening displacement (CTOD) test per BS &#;1; The J integral test per ASTM E; The Pellini drop-weight test per ASTM E208.[59]

Unusual conditions

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Underwater welding

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). 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. Welding in space is also possible&#;it was first attempted in by Russian cosmonauts during the Soyuz 6 mission, when they performed experiments to test shielded metal arc welding, plasma arc welding, and electron beam welding in a depressurized environment. 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. Advances in these areas may be useful for future endeavours similar to the construction of the International Space Station, which could rely on welding for joining in space the parts that were manufactured on Earth.[60]

Safety issues

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A stick welding booth equipped with local exhaust system (LEV) that removes the toxic fumes, gases, vapours and dusts before they can mix with the room air. Besides toxic emissions, the booth also helps protect bystanders from UV light. With a well-ventilated booth, personal protective equipment is still needed for the welder. Arc welding with a welding helmet, gloves, and other protective clothing ()

Welding can be dangerous and unhealthy if the proper precautions are not taken. However, using new technology and proper protection greatly reduces risks of injury and death associated with welding.[61]

Since many common welding procedures involve an open electric arc or flame, the risk of burns and fire is significant; this is why it is classified as a hot work process. To prevent injury, 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. Synthetic clothing such as polyester should not be worn since it may burn, causing injury.[62] Additionally, the brightness of the weld area leads to a condition called arc eye or flash burns in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Goggles and welding helmets with dark UV-filtering face plates are worn to prevent this exposure.[63] Since the s, some helmets have included a face plate which instantly darkens upon exposure to the intense UV light. To protect bystanders, the welding area is often surrounded with translucent welding curtains. These curtains, made of a polyvinyl chloride plastic film, shield people outside the welding area from the UV light of the electric arc, but cannot replace the filter glass used in helmets.[64]

A chamber designed to contain welding fumes for analysis

A video describing research on welding helmets and their ability to limit fume exposure

Welders are often exposed to dangerous gases and particulate matter. Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides. The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. This is because smaller particles have the ability to cross the blood&#;brain barrier. Fumes and gases, such as carbon dioxide, ozone, and fumes containing heavy metals, can be dangerous to welders lacking proper ventilation and training.[65] Exposure to manganese welding fumes, for example, even at low levels (<0.2 mg/m3), may lead to neurological problems or to damage to the lungs, liver, kidneys, or central nervous system.[66] Nano particles can become trapped in the alveolar macrophages of the lungs and induce pulmonary fibrosis.[67] 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.[65]

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Costs and trends

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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.[68] 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 time spent fitting, 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.[68]

For manual welding methods, labor costs generally make up the vast majority of the total cost. As a result, many cost-saving measures are focused on minimizing 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 automation 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.[68]

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[69] and at first, spot welding was its most common application, but robotic arc welding increases in popularity as technology advances. 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. 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.[70]

The trend of accelerating the speed at which welds are performed in the steel erection industry comes at a risk to the integrity of the connection. Without proper fusion to the base materials provided by sufficient arc time on the weld, a project inspector cannot ensure the effective diameter of the puddle weld therefore he or she cannot guarantee the published load capacities unless they witness the actual installation.[71] This method of puddle welding is common in the United States and Canada for attaching steel sheets to bar joist and structural steel members. Regional agencies are responsible for ensuring the proper installation of puddle welding on steel construction sites. Currently there is no standard or weld procedure which can ensure the published holding capacity of any unwitnessed connection, but this is under review by the American Welding Society.

Glass and plastic welding

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The welding together of two tubes made from lead glass A bowl made from cast-glass. The two halves are joined together by the weld seam, running down the middle.

Glasses and certain types of plastics are commonly welded materials. Unlike metals, which have a specific melting point, glasses and plastics have a melting range, called the glass transition. When heating the solid material past the glass-transition temperature (Tg) into this range, it will generally become softer and more pliable. When it crosses through the range, above the glass-melting temperature (Tm), it will become a very thick, sluggish, viscous liquid, slowly decreasing in viscosity as temperature increases. Typically, this viscous liquid will have very little surface tension compared to metals, becoming a sticky, taffy to honey-like consistency, so welding can usually take place by simply pressing two melted surfaces together. The two liquids will generally mix and join at first contact. Upon cooling through the glass transition, the welded piece will solidify as one solid piece of amorphous material.

Glass welding

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Glass welding is a common practice during glassblowing. It is used very often in the construction of lighting, neon signs, flashtubes, scientific equipment, and the manufacture of dishes and other glassware. It is also used during glass casting for joining the halves of glass molds, making items such as bottles and jars. Welding glass is accomplished by heating the glass through the glass transition, turning it into a thick, formable, liquid mass. Heating is usually done with a gas or oxy-gas torch, or a furnace, because the temperatures for melting glass are often quite high. This temperature may vary, depending on the type of glass. For example, lead glass becomes a weldable liquid at around 1,600 °F (870 °C), and can be welded with a simple propane torch. On the other hand, quartz glass (fused silica) must be heated to over 3,000 °F (1,650 °C), but quickly loses its viscosity and formability if overheated, so an oxyhydrogen torch must be used. Sometimes a tube may be attached to the glass, allowing it to be blown into various shapes, such as bulbs, bottles, or tubes. When two pieces of liquid glass are pressed together, they will usually weld very readily. Welding a handle onto a pitcher can usually be done with relative ease. However, when welding a tube to another tube, a combination of blowing and suction, and pressing and pulling is used to ensure a good seal, to shape the glass, and to keep the surface tension from closing the tube in on itself. Sometimes a filler rod may be used, but usually not.

Because glass is very brittle in its solid state, it is often prone to cracking upon heating and cooling, especially if the heating and cooling are uneven. This is because the brittleness of glass does not allow for uneven thermal expansion. Glass that has been welded will usually need to be cooled very slowly and evenly through the glass transition, in a process called annealing, to relieve any internal stresses created by a temperature gradient.

There are many types of glass, and it is most common to weld using the same types. Different glasses often have different rates of thermal expansion, which can cause them to crack upon cooling when they contract differently. For instance, quartz has very low thermal expansion, while soda-lime glass has very high thermal expansion. When welding different glasses to each other, it is usually important to closely match their coefficients of thermal expansion, to ensure that cracking does not occur. Also, some glasses will simply not mix with others, so welding between certain types may not be possible.

Glass can also be welded to metals and ceramics, although with metals the process is usually more adhesion to the surface of the metal rather than a commingling of the two materials. However, certain glasses will typically bond only to certain metals. For example, lead glass bonds readily to copper or molybdenum, but not to aluminum. Tungsten electrodes are often used in lighting but will not bond to quartz glass, so the tungsten is often wetted with molten borosilicate glass, which bonds to both tungsten and quartz. However, care must be taken to ensure that all materials have similar coefficients of thermal expansion to prevent cracking both when the object cools and when it is heated again. Special alloys are often used for this purpose, ensuring that the coefficients of expansion match, and sometimes thin, metallic coatings may be applied to a metal to create a good bond with the glass.[72][73][failed verification]

Plastic welding

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Plastics are generally divided into two categories, which are "thermosets" and "thermoplastics." A thermoset is a plastic in which a chemical reaction sets the molecular bonds after first forming the plastic, and then the bonds cannot be broken again without degrading the plastic. Thermosets cannot be melted, therefore, once a thermoset has set it is impossible to weld it. Examples of thermosets include epoxies, silicone, vulcanized rubber, polyester, and polyurethane.

Thermoplastics, by contrast, form long molecular chains, which are often coiled or intertwined, forming an amorphous structure without any long-range, crystalline order. Some thermoplastics may be fully amorphous, while others have a partially crystalline/partially amorphous structure. Both amorphous and semicrystalline thermoplastics have a glass transition, above which welding can occur, but semicrystallines also have a specific melting point which is above the glass transition. Above this melting point, the viscous liquid will become a free-flowing liquid (see rheological weldability for thermoplastics). Examples of thermoplastics include polyethylene, polypropylene, polystyrene, polyvinylchloride (PVC), and fluoroplastics like Teflon and Spectralon.

Welding thermoplastic with heat is very similar to welding glass. The plastic first must be cleaned and then heated through the glass transition, turning the weld-interface into a thick, viscous liquid. Two heated interfaces can then be pressed together, allowing the molecules to mix through intermolecular diffusion, joining them as one. Then the plastic is cooled through the glass transition, allowing the weld to solidify. A filler rod may often be used for certain types of joints. The main differences between welding glass and plastic are the types of heating methods, the much lower melting temperatures, and the fact that plastics will burn if overheated. Many different methods have been devised for heating plastic to a weldable temperature without burning it. Ovens or electric heating tools can be used to melt the plastic. Ultrasonic, laser, or friction heating are other methods. Resistive metals may be implanted in the plastic, which respond to induction heating. Some plastics will begin to burn at temperatures lower than their glass transition, so welding can be performed by blowing a heated, inert gas onto the plastic, melting it while, at the same time, shielding it from oxygen.[74]

Solvent welding

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Many thermoplastics can also be welded using chemical solvents. When placed in contact with the plastic, the solvent will begin to soften it, bringing the surface into a thick, liquid solution. When two melted surfaces are pressed together, the molecules in the solution mix, joining them as one. Because the solvent can permeate the plastic, the solvent evaporates out through the surface of the plastic, causing the weld to drop out of solution and solidify. A common use for solvent welding is for joining PVC (polyvinyl chloride) or ABS (acrylonitrile butadiene styrene) pipes during plumbing, or for welding styrene and polystyrene plastics in the construction of models. Solvent welding is especially effective on plastics like PVC which burn at or below their glass transition, but may be ineffective on plastics like Teflon or polyethylene that are resistant to chemical decomposition.[75]

See also

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References

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Sources

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• Cary, Howard B; Helzer, Scott C. (). Modern Welding Technology. Upper Saddle River, New Jersey: Pearson Education. ISBN 0-13--3.

• Kalpakjian, Serope; Schmid, Steven R. (). Manufacturing Engineering and Technology. Prentice Hall. ISBN 0-201--0.

• Lincoln Electric (). The Procedure Handbook of Arc Welding. Cleveland: Lincoln Electric. ISBN -25-82-2.

• Weman, Klas (). Welding processes handbook. New York, NY: CRC Press LLC. ISBN 0---8.

Welders are one of the essential tools in the manufacturing industry for joining metals and other materials. So many welding processes could be needed, and no single welding machine fits them all. As a result, at least ten different welder types are available to handle most welding projects.

Each machine type has its unique features and capabilities with variations in price and characteristics. Here is a look at the most popular welding machine types and some you might not be as familiar with, along with their uses:

1. Shielded Metal Arc Welding Machine (Stick)

Also known as manual metal stick welding (MMAW or MMA) is a welding process that uses a flux-coated electrode to join metals.
Image credit: https://blog.thepipingmart.com

Stick welding uses an electric current between the base metal and the stick (filler rod) to generate heat for welding. The filler rod is covered with a flux that prevents oxidation and contamination by producing carbon dioxide gas during welding. SMAW machines are operated by both AC and DC currents.

SMAW welders are among the most economical welders recommended for steel, inox steel
, and cast iron. Stick welding is ideal for open spaces and outdoor use, such as pipeline welding, construction, farm equipment repairs, steel erection, and maintenance.

2. MIG Welding Machine

Metal inert gas&#;welding is generally used for large and thick materials.
Image credit: https://www.weldman.net

MIG welding is one of the more accessible types of welding to learn. Metal inert gas welding, as it&#;s officially called, is typically used for large and thick materials. MIG machines use a consumable wire as an electrode and a filler material, resulting in a faster process and lower production costs.

The machines are usually accompanied by an external gas tank containing a shielding gas, typically Argon. A MIG welders works well with stainless steel, aluminum, magnesium, carbon steel, copper, and other metals. You&#;ll find these machines in the automotive, construction, shipyards, robotics, farms, and home workshops.

MIG Welders:

MIG (Metal Inert Gas) welding machines are one of the most commonly used welders in the industry. They use a consumable wire electrode that is fed through the machine, and a shielding gas, typically a mixture of argon and carbon dioxide, to protect the weld pool from contamination. MIG welders are versatile and can be used to weld a variety of materials, including carbon steel, stainless steel, and aluminum.

MIG Welder Types:

There are various types of MIG welders, including basic MIG welders, multi-process welders, and pulse MIG welders. Basic MIG welders are ideal for light-duty welding projects, while multi-process welders can handle a range of welding techniques, including MIG, TIG, and stick welding. Pulse MIG welders are designed for high-quality, precision welding projects, and use advanced technology to regulate the welding current and voltage.

3. TIG Welding Machine

Tungsten inert gas&#;welding is highly versatile, enabling industry professionals to join a wide range of small and thin materials.
Image credit: https://ipotools.eu

Tungsten inert gas welding (TIG) machines are preferred for thin metals and smaller projects. They produce precise and clean welds but require more experience and some multitasking compared to other techniques. The machine operator must hold the welding torch in one hand while feeding the filler wire with the other. The process requires a non-consumable tungsten electrode to produce a weld.

Unlike stick welding, TIG machines need a clean, rust-free surface to create a quality weld. The machines are used to weld steel, inox steel
, Chromoly, aluminum, nickel alloys, magnesium, Titanium, copper, brass, and bronze.

TIG helps repair lawnmowers, bike frames, door handles, fenders, etc. TIG&#;s other applications include pipeline welding, aerospace, race car fabrication, artwork, and motorcycles.

4. Flux-Cored Arc Welding Machine

FCAW is a type of Gas Metal stick welding (GMAW) having a cored wire instead of a solid wire.
Picture credit: https://www.diytrade.com

Flux core welders are generally used for thick metals and out-of-position welding. FCAW machines work equally well indoors and outdoors, and because they use a continuously-fed flux-filled electrode, there is no need for external shielding gas or to stop and restart the weld.

These welders produce less electrode waste and fewer fumes than other methods while operating at extremely hot temperatures, approaching amps. Although similar to the MIG welding process, FCAW is considered more powerful and uses a different gas shield.

Flux-cored arc machines are recommended for carbon steels, cast iron, nickel-based alloys, and some inox steel. They are popular in construction and fabrication applications.

5. Energy Beam Welding Machine

Energy beam welding otherwise referred to as electron-beam welding, is a fusion welding process.
Picture credit: https://www.techbriefs.com

The EWB machine employs a high-speed stream of tightly-focused electrons using magnetic fields and is applied to the base materials. The machine can join thick metals with thin metals or fuse different metals, and EWB can also weld specific points on the metals with little or no heat distortion in the welded areas.

Because the welder must perform this welding in a vacuum to prevent the electron beam from being absorbed by the air, the machine is not for home use. However, EWB is frequently used in power generation environments, plus the automotive, defense, medical, aerospace, and oil and gas industries.

6. Plasma Arc Welding Machine

The electric arc is formed in between the work piece and the electrode.
Picture credit: https://weldguru.com

Plasma-transferred stick welding machines (PTAW) are industrial-sized machines similar to TIG welders but with an anode surrounding the tungsten electrode. This anode constricts the arc to a laser-like precision and acts as a shield for the electrode, protecting it from the filler used in this process. Primarily used in the aircraft manufacturing industry, these welders are much more expensive than those we have discussed.

7. Submerged Arc Welding Machine

SAW refers to an arc welding process using a continuous melting wire or strip electrode with high deposition rate.
Image credit: https://www.cruxweld.com

Submerged arc welding machines involve creating an electric arc between a continuously fed electrode and the workpiece. A reusable powder flux replaces the gas shield, and the machines produce high-quality welds.

Because this is an automatic or semi-automatic system, the operator only needs a little experience with the machine. The primary downside to this machine is that it is not portable. These machines work well with steel, stainless steel, and steel and nickel alloys and are often found in plumbing, pipeline, and pressure vessel applications.

8. Atomic Hydrogen Welding Machine

AHW basic equipment.
Image credit: https://www.weldinginfo.org

Atomic hydrogen welding (AHW) machines use an arc generated between two tungsten electrodes and hydrogen shielding gas from an external cylinder. It&#;s called atomic hydrogen welding because the arc separates the hydrogen into atomic form.

These welding machines require an experienced operator, and they are being replaced by the more popular MIG welders, partly because AHW is more costly. AHW machines are suitable for thin and thick materials and rapid welding situations.

Stainless steel, ferrous metals, non-ferrous metals, and some alloys are compatible with AHW.

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9. Oxyacetylene Gas Welding Machine

Oxy-Acetylene Gas Welding.
Picture credit: https://extrudesign.com

The oxyacetylene welder uses a fuel gas (usually acetylene) and oxygen as the heating medium. The flame is the main component produced at the end of the torch since it melts the base metal and possible filler to form the weld.

Gas welding works better for thin materials and not as well for thick ones. Operators can control the temperature and weld beads by adjusting the oxygen-to-fuel gas ratio on the machine. These welders are still used worldwide because of their relatively low cost and portability.

The recommended metals to use with this machine are restricted to iron-based and ferrous. You can still find oxyacetylene welding in fabrication projects, plumbing, automotive repair, and fieldwork.

10. Multipurpose Welding Machines

Portable Multi-Process Welder (Lincoln Electric Power MIG Welder) &#; has a number of welding modes suitable for multiple welding processes
Picture credit: https://www.thomasnet.com

In addition to welder performing one type, multi-process welders can do two or three types on one machine. For example, 3-in-1 welders will perform TIG, MIG, and stick welding on the same machine, and others are capable of TIG and stick with a plasma cutter included.

You might need to purchase additional accessories to change the process, but you will not need to buy three separate machines!

A Few Lesser-Known Welding Machines

Although MIG, TIG, and stick welding dominate today&#;s welding, they do not perform all of it. Here are a few machines you may have heard of&#;or perhaps not:

• Spot welder Spot welding is a type of resistance welding that combines two or more metal sheets by applying heat and pressure to the weld area with an electric current.
  
• Thyristor MIG welder: These machines are ideal for steel and aluminum because of their high output and precise work. Thyristors are often used in automotive repair shops, construction sites, and manufacturing plants for joining sheet metal or repairing machinery.
  
• Transformer welder: Within the welding machine, the transformer converts the high-voltage input from the wall plug, usually from 208 to 600 volts, with a low alternating current (AC) from 15 to 55 amps.
  
• Rectifier welder: This machine is an electric device that joins two pieces of metal. It is composed of a power source that converts AC into DC and then sends it through electrodes attached to the joined metal pieces. The DC creates heat and melts the metal pieces together, forming a solid bond.
  
• Converter welder: A converter welding machine is an advanced technology using electrical current to create heat and melt metals. It is frequently used for stick welding since it makes higher-quality welds than most traditional methods.

Samples of lesser-known welding machines

Thyristor MIG Welding Machine Automated Torque Converters Welding Machine Welding Rectifier machine Transformer Welding Machine

Carbon Dioxide Welders
Carbon dioxide (CO2) welders are a type of welding machine that utilize CO2 gas to shield the welding arc and protect the weld pool from atmospheric contamination. These machines are often used for MIG welding, a popular welding process that uses a consumable wire electrode and a shielding gas to join two pieces of metal. CO2 welders are widely used in the automotive industry and are suitable for welding a variety of materials, including stainless steel and aluminum.

Welding Helmets
Welding helmets are essential pieces of protective equipment that shield the welder&#;s face and eyes from harmful radiation and debris. They come in a range of styles and designs, from basic models that cover the face to advanced auto-darkening helmets that adjust the shade of the lens based on the welding arc&#;s intensity.

Arc Length
Arc length is an important consideration when welding. It is the distance between the end of the welding wire and the workpiece. Keeping the correct arc length is crucial for producing a strong and consistent weld. A longer arc length can cause excessive spatter, while a shorter arc length can lead to a shallow weld.
Welding Table
A welding table is a specialized piece of equipment designed for holding the workpiece during welding. It provides a stable and secure surface for welding projects, allowing for precise and accurate welds. Welding tables are typically made of heat-resistant materials and can withstand the high temperatures generated during welding.
Welding Wire
Welding wire is the consumable material used in welding machines to join two pieces of metal. The type of welding wire used depends on the welding project&#;s requirements and the welding machine being used. For example, MIG welding wire is typically used in MIG welding machines and requires a shielding gas, such as CO2 or a mixture of argon and CO2.
Welding Project
A welding project refers to any welding work that needs to be completed, whether it is a small DIY project or a large-scale industrial project. The type of welding machine and welding equipment used will depend on the requirements of the project and the materials being welded.
MIG Welding Gas
MIG welding gas is a shielding gas used in MIG welding machines. It helps to protect the weld pool from atmospheric contamination and ensure a clean and strong weld. The type of MIG welding gas used will depend on the welding project&#;s requirements and the materials being welded.
Welding Torch
A welding torch is a handheld tool used in various welding machines, such as MIG welding machines and TIG welding machines. It is used to direct the heat and flame to the workpiece and welding wire, creating the weld. The type of welding torch used will depend on the welding machine being used and the welding project&#;s requirements.
Welding Equipment
Welding equipment refers to the various tools and machines used in welding, such as welding machines, welding torches, welding tables, and welding helmets. Choosing the right welding equipment is crucial for achieving optimal results and ensuring the safety of the welder.
Filler Metal
Filler metal is a type of welding wire used to fill gaps in the weld joint or add additional material to the weld. It is typically used in MIG welding and TIG welding machines and is available in various types and sizes, depending on the welding project&#;s requirements.
Weld Metal
Weld metal is the metal that is fused together during the welding process. It is created by melting the welding wire and the workpiece, allowing them to combine and solidify.
Flux Core Wire
Flux core wire is a type of welding wire that contains a flux compound, eliminating the need for a separate shielding gas in the welding process. It is commonly used in MIG welding machines for welding projects in outdoor or windy conditions.
Weld Bead
A weld bead is the visible seam created by the welding process. It is formed by the molten metal that has cooled and solidified, creating a strong and durable weld.
Welding Gun
A welding gun is a handheld tool used in MIG welding machines. It is attached to the welding wire and directs the heat and shielding gas to the workpiece

Conclusion

There are too many welding processes and machines to cover in one article, just as there are endless areas using welding in their manufacturing projects.
Suffice it to say that for every welding task in construction, aerospace, pipelines, rail lines, tubes, steel, automobile, shipbuilding, electronics, solar, and storage tanks, a welding machine will be available to handle it.

In addition, we recommend checking out a very popular YouTube channel with extensive welding content by Jody Collier. His channel offers: &#;Clear arc shots and plain talk to help you pass a test&#;, &#;fix stuff&#;, &#;build stuff&#;, &#;get a raise&#;.
Watch this informative video about various welding machine types and techniques on Jody Collier&#;s YouTube channel.

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