Types of Welding Processes

The links to the topics below are the best informational articles that I could find on each of the subjects.

Carbon Arc Gouging
Carbon Arc Gouging or Air Arc Gouging is not a welding process, but is an effective process to quickly remove base or weld metal where needed. A copper coated carbon electrode is placed into a gouging rig that is designed for that purpose. A high voltage and amperage power source coupled with an air source of about 80-100 psi melts the metal and expels the molten metal from the work piece. The process is loud, smokey, and sprays molten metal in the direction that the air jet is pointed at. The process is normally used for weld repairs, back gouging the back side of full penetration welds, beveling plate edges, and removing excess weld.
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Cold welding
Cold or contact welding was first recognized as a general materials phenomenon in the 1940s. It was then discovered that two clean, flat surfaces of similar metal would strongly adhere if brought into contact under vacuum. It is now known that the force of adhesion following first contact can be augmented by pressing the metals tightly together, increasing the duration of contact, raising the temperature of the work pieces, or any combination of the preceding.
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Electron beam welding
Electron beam welding is a welding process where the energy to melt the material is applied by an electron beam. To avoid dispersion of the electron beam, the workpiece is typically placed in a vacuum chamber, although electron beam welding under atmospheric pressure is attempted too. Electron beam welding is an established branch of Electron Beam Technology.
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Explosive welding
Explosive welding uses the force of a controlled detonation to atomically fuse one metal object to another. The process is popular for the joining of dissimilar metals. Explosive welding is considered a cold welding process that allows metals to be joined without losing their pre-welded metalurgical properties. This process allows the joining of different metals that would be impossible by any other welding process.
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Forge welding
Forge welding , the oldest known form of welding, is a welding process of heating two or more pieces of wrought iron or steel until their surfaces are malleable and then hammering them together. Often a flux is used to keep the welding surfaces from oxidizing and producing a poor quality weld. A simple flux can be made from borax, sometimes with the addition of iron filings. Care must be taken to avoid "burning" the metal, which is overheating to the point that it gives off sparks from rapid oxidation.
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Friction welding
Friction welding Rotary friction welding was the first of the friction welding methods to be developed and commercially used. There are two method variations: continuous drive rotary friction welding and stored energy friction welding. In the first method, a piece is rotated at a set speed while the joining stationary piece is fed into it at a pre-determined pressure until the metal in the joint area reaches a temperature high enough to melt it. The other method, also known as inertia welding adds a flywheel to the rotating piece and power is cut as the two pieces are forced together with the same end result-a welded joint. Parts with a non-rotational geometry can be joined by linear reciprocating frictional welding which is similar in form to a reciprocating saw.
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Friction-stir welding
Friction-stir welding was invented and experimentally proven by Wayne Thomas and a team of his colleagues at the TWI Welding Institute, U. K., in December 1991. TWI holds a patent for the process. In FSW, a cylindrical-shouldered tool, with a profiled threaded / unthreaded probe (nib) is rotated at a constant speed and fed at a constant traverse rate into the joint line between two pieces
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Fusion welding
Fusion welding is any welding process that uses a heat source to weld a material and also usually uses a protective shield from the atmosphere by a gas shield or flux or both. This would include gas, stick, mig, tig, sub-arc, laser, orbital, plasma, spot, stud, thermite, and electron beam welding.
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Gas welding
In gas welding, the heat energy and high temperature needed to melt the metal is obtained by the combustion of a fuel gas with oxygen. Gas Fuels--The most commonly used fuel gas is acetylene. Other gases used are liquified petroleum gas (LPG), natural gas, hydrogen and MAPP gas. Acetylene is obtained from the action of water upon calcium carbide. Calcium carbide and water combine to yield acetylene gas and lime as a by-product.
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Induction welding
Induction welding is a form of welding that uses electromagnetic induction to heat the workpiece. The welding apparatus contains an induction coil that is energized with a radio-frequency electric current. This generates a high-frequency electromagnetic field that acts on either an electrically conductive or a ferromagnetic workpiece. In an electrically conductive workpiece, such as steel, the main heating effect is resistive heating, which is due to magnetically induced currents called eddy currents. Nonmagnetic materials such as plastics can be induction-welded by implanting them with metallic or ferro-magnetic compounds called susceptors, that absorb the electromagnetic energy from the induction coil, become hot, and lose their heat energy to the surrounding material by thermal conduction.
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Laser welding
Laser welding was in its infancy 20 years ago. Today, laser welding is an integral part of the plastics and metal working industries. A wide variety of cutting and welding operations can be performed on a variety of hard to weld and dissimilar materials with this process. A benefit of laser cutting is the ability to cut a wide range of materials such as metal, polymers, ceramics, wood, leather, cloth, and more. Cladding, heat-treating and hard-surfacing can also be accomplished with laser welding.
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Manual Metal Arc Welding
Manual Metal Arc welding, also known as stick or SMAW-Shielded Metal Arc Welding is one of the most common and reliable forms of welding. An electric current (either alternating current or direct current) is used to form an arc between an electrode coated in flux and the metals to be joined. The flux gives off gases to prevent oxygen reacting with the weld metal. The flux then solidifies to form slag on top of the weld. Once cool the slag can easily be chipped off provided that the weld is properly applied.
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Gas Metal Arc Welding
Metal Inert Gas or MIG welding, also known as gas metal arc welding, is a type of welding which utilizes a welding gun through which a continuous wire electrode and a shielding gas is fed. The wires used in the electrodes are typically 0.7, 1.0, 1.2 or 1.6 mm diameter, either solid or 'flux' filled. To prevent nitrogen and oxygen contaminating the weld, an inert shielding gas is fed around the arc, either argon or helium.
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Plasma welding
Plasma welding
is a process that utilizes a stream of ionized particles. It originated in 1955 as an aluminum cutting process and used as such until the first successful welds were produced in 1963. The plasma torch uses a water-cooled copper nozzle and tungsten electrode. An electric arc is produced between the electrode and copper nozzle while a gas suchas helium or hydrogen is forced through the arc. The gas becomes super-heated and ionizes into a plasma stream. Click the link for more information.

Resistance Welding
Resistance Spot Welding is a quick and simple method of welding metal. It uses two large electrodes which are placed on either side of the surface to be welded, and passes a large electrical current through them that heats up the metal in-between. The result is a small "spot" that is quickly heated to the melting point, forming a small dot of welded metal. Applying the current for too long can burn a hole right through the material.
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Stud welding

Stud welding is an electric arc process for attaching studs and other fasteners to steel and other surfaces. Stud welding eliminates the need for drilling or punching holes in the structure. A special collet on the stud gun holds a ceramic ferrule in place around the stud. This ferrule holds the molten metal in place and helps form the fillet weld as the stud cools after it is shot onto the structure. Click the link for more information.

Submerged arc welding Submerged arc welding is a type of welding which utilises a large diameter wire electrode, typically 3 or 4mm diameter. The electode is fed into the arc at a controlled rate. The arc is shielded by a granular flux which is poured to form a pile of flux surrounding the arc. Unlike other types of arc welding, eye protection is not required, since the arc is covered by the flux. Some of the flux is converted to slag by the arc, which protects the weld as it cools. The slag can easily be chipped off the weld when cool. Surplus flux is collected for re-use.
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Thermite
A thermite or thermit reaction is one in which aluminum metal is oxidized by an oxide of another metal, most commonly that of iron. (The name thermite is also used to refer to a mixture of two such chemicals.) The products are aluminium oxide, free elemental metal and a great deal of heat. The reactants are commonly powdered and mixed with a binder to keep the material solid and prevent separation.
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Tungsten Inert Gas Welding
Tungsten inert gas welding or TIG is also known as gas tungsten arc welding (GTAW) or HELIARC, a trade name of Linde. A fixed tungsten electrode protected by a shielding gas is used to create an arc that melts the metal of the parts to be joined. As there is no continuous feed wire electrode as with MIG welding, a filler rod is dipped in the puddle of molten metal to join the two parts.
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(TIG)
Ultrasonic welding In ultrasonic welding, energy is delivered to the joint area in the form of high-power ultrasound. This type of welding is used to build assemblies that are too small, complex, or delicate for more common welding techniques to be appropriate. It is also used to weld plastics and materials that are dissimilar. For joining complex injection molded parts, ultrasonic welding requires expensive custom equipment specially designed for the parts being welded. The parts are sandwiched between shaped mandrel and the horn. One of the plastic parts has a spiked energy director which contacts the second plastic part. The ultrasonic energy melts the point contact between and the parts and they are joined. This process replaces a glued joint.
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Underwater SMAW Welding In underwater SMAW welding, a coated welding electrode along with an insulated electrode holder is used to make sound welds. This type of welding is used to weld assemblies that are impractical or too expensive to move above water. Specific techniques are used to insure a sound weld.
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Welding differs from soldering Soldering is a method of applying a lower melting point metal to join other metal parts using solder. Soldering can be performed in a number of ways, including bulk liquification, or by using a point source such as an electric soldering iron or brazing torch. One application of soldering is making connections between electronic parts and printed circuit boards, another is in plumbing.
..... Click the link for more information. brazing Brazing is a joining process whereby a non-ferrous filler metal and an alloy are heated to melting temperature (above 450 °C) and distributed between two or more close-fitting parts by capillary attraction. At its liquidus temperature, the molten filler metal interacts with a thin layer of the base metal, cooling to form an exceptionally strong, sealed joint due to grain structure interaction. The brazed joint becomes a sandwich of different layers, each metallurgicaly linked to each other. If silver alloy is used, brazing can be referred to as Silver Brazing or Sil-brazing. Colloquially, the inaccurate terms "Silver Soldering" or "Hard Soldering" are used.
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Silver (Brazing) Soldering uses a material called silver solder. A solder is a metal alloy (often of silver, tin and lead), usually with a low melting point, that is melted and used to join metallic surfaces, especially in the fields of electronics and plumbing, in a process called soldering. In electronics, tin/lead solders are normally 60/40 by weight in order to produce a near-eutectic mixture (lowest melting point - below 190°C).
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