Methods of Welding Metals

Welding is a fabrication process wherein two or more parts are fused together by means of heat, pressure or both forming a join as the parts cool. Welding is typically suited for metals and thermoplastics nevertheless could also be used on wood. A few materials necessitate the employment of specific processes and techniques. Several materials are considered as 'unweldable,' a term not ordinarily present in dictionaries however practical and illustrative in engineering.

The parts nor sections or components that will be joined are termed as parent material. The material added to assist in forming the join is referred to as filler or consumable. The form of these materials often see them labelled as parent plate or pipe, filler wire, consumable electrode, and so on. The completed welded joint is called a weldment.

Consumables are typically selected for being comparable in composition to the parent material, consequently forming a homogeneous weld, yet there can be instances, for example when welding brittle cast irons, when a filler, which has a completely different composition and hence properties, is used. These welds are typically called heterogeneous welds.

Some of the most widespread present-day welding techniques are:

• Arc Welding methods which inturn feature
• Shielded metal arc welding (SMAW), also referred to as "stick welding".
• Gas tungsten arc welding (GTAW), also referred to as TIG (tungsten, inert gas).
• Gas metal arc welding (GMAW), also referred to as MIG (metal, inert gas).
• Flux-cored arc welding (FCAW), nearly the same as MIG.
• Submerged arc welding (SAW), typically referred to as Sub Arc.
• Electroslag welding (ESW), a highly productive technique meant for thicker materials.
• Additional arc welding processes including atomic hydrogen welding, electrogas welding, as well as stud arc welding.
• Resistance Welding
• Gas Welding
• Energy Beam Welding
• Solid-State Welding

List of Welding Processes

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This is a listing of welding processes, segregated onto their respective categorizations. The associated N reference numbers are specified in ISO 4063. Numbers in parentheses are obsolete and have been removed from the latest version of ISO 4063. The AWS reference codes of the American Welding Society are typically utilised in North America.

Arc welding

Oxyfuel gas welding

Resistance welding

Solid-state welding

Other types of welding

Shielded Metal Arc Welding (SMAW

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Shielded metal arc welding (SMAW), also referred to as manual metal arc welding (MMA or MMAW), flux shielded arc welding or informally as stick welding, can be described as a manual arc welding process which utilizes a consumable electrode covered with a flux to make the weld.

An electric current, in the form of either alternating current or direct current, from a welding power supply, is employed to create an electric arc between the electrode and the metals to be joined. The workpiece along with the electrode melts forming a pool of molten metal identified as weld pool which cools to form a joint. As the weld is produced, the flux coating of the electrode disintegrates, giving off vapours which serve as a shielding gas together with providing a layer of slag, both of which protect the weld area from atmospheric contamination.

As a consequence of the versatility of the process along with the simplicity of its equipment in addition to operation, shielded metal arc welding is probably the world's first and the most preferred welding processes. It dominates alternative welding processes within the maintenance and repair industry, in addition to, through flux-cored arc welding, rising in level of popularity, SMAW continues to be made use of extensively within the construction of heavy steel structures as well as in industrial fabrication. The process is employed primarily to weld iron and steels which include stainless steel nevertheless aluminium, nickel and copper alloys can additionally be welded using this method.

Stick Electrodes

The selection of electrode intended for SMAW is dependent upon several factors, for example the weld material, welding position as well as the required weld properties. The electrode is coated in a metal mixture called flux, which gives off gases as it decomposes to prevent weld contamination, introduces deoxidisers to purify the weld, results in weld-protecting slag to form, improves the arc stability, and supplies alloying elements to further improve the weld quality.

Electrodes are generally divided into three groups:

• those designed to melt rapidly are referred to as "fast-fill" electrodes,
• those designed to solidify rapidly are referred to as "fast-freeze" electrodes, and
• intermediate electrodes are generally known as "fill-freeze" or "fast-follow" electrodes.

Fast-fill electrodes are designed to melt rapidly in order that the welding speed can be maximised, whereas fast-freeze electrodes supply filler metal which solidifies rapidly, helping to make welding in a number of positions conceivable as a result of preventing the weld pool from shifting substantially prior to solidifying.

The composition of the electrode core usually is comparable and occasionally identical to that of the base material. Nevertheless, despite the fact that several feasible alternatives exist, a slight difference in alloy composition could strongly have an impact on the properties of the resulting weld. This is especially valid involving alloy steels including HSLA steels. Similarly, electrodes of compositions comparable to those of the base materials are frequently used for welding nonferrous materials including aluminium and copper. Nonetheless, frequently it's desirable to utilise electrodes having core materials substantially distinctive from the base material.

Electrode coatings can comprise of a number of different compounds, which include rutile, calcium fluoride, cellulose, as well as iron powder. Rutile electrodes, coated with 25%–45% TiO₂, are characterised by simplicity of use in addition to excellent appearance of the resulting weld. However, they generate welds having high hydrogen content, promoting embrittlement and cracking. Electrodes that contain calcium fluoride (CaF₂), occasionally referred to as basic or low-hydrogen electrodes, are hygroscopic and additionally will have to be stored in dry conditions. They generate strong welds, however having a coarse and convex-shaped joint surface. Electrodes coated with cellulose, particularly when combined with rutile, deliver deep weld penetration, however because of their high moisture content, special procedures must be made use of to counteract excessive risk of cracking. Lastly, iron powder is a prevalent coating additive which improves the rate at which the electrode fills the weld joint, as much as doubly fast.

To distinguish different electrodes, the American Welding Society established a system which assigns electrodes using a four- or five-digit number. Covered electrodes composed of mild or low alloy steel have the prefix E, followed by their number. The first two or three digits of the number specify the tensile strength of the weld metal, in thousand pounds per square inch (ksi). The penultimate digit typically identifies the welding positions permissible when using the electrode, generally making use of the values 1 (usually fast-freeze electrodes, implying all position welding) and 2 (usually fast-fill electrodes, implying horizontal welding only). The welding current in addition to form of electrode covering are specified through the last two digits together. Whenever applicable, a suffix is employed to denote the alloying element being contributed by the electrode.

Common electrodes include the -

• E6010, a fast-freeze, all-position electrode having a minimum tensile strength of 60 ksi that is operated making use of DCEP, and provides deep weld penetration along with a forceful arc efficient at burning through light rust or oxides on the workpiece.
• E6011 is comparable with the exception that its flux coating enables it to be used in combination with alternating current in addition to DCEP.
• E7024 is a fast-fill electrode, employed predominantly to produce flat or horizontal fillet welds making use of AC, DCEN, or DCEP.
• E6012, E6013, and E7014 are all instances of fill-freeze electrodes, all of which offer a compromise between fast welding speeds and all-position welding.

Gas Tungsten Arc Welding (GTAW)

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Gas tungsten arc welding (GTAW), also referred to as tungsten inert gas (TIG) welding, is an arc welding process which uses a non-consumable tungsten electrode to produce the weld. The weld area along with the electrode are protected from oxidation or other sorts of atmospheric contamination by means of an inert shielding gas, argon or helium, and also a filler metal is commonly made use of, although certain welds, identified as autogenous welds, tend not to require it. Anytime helium is employed, this is identified as heliarc welding. A constant-current welding power supply generates electrical energy, that is conducted across the arc through a column of highly ionised gas and metal vapours identified as a plasma. GTAW is most frequently employed to weld thin sections of stainless steel in addition to non-ferrous metals including aluminium, magnesium, and copper alloys. The process permits the operator improved control during the weld as compared to competing processes including shielded metal arc welding and gas metal arc welding, making it possible for stronger, higher quality welds. Nevertheless, GTAW is comparatively more complex and also challenging to master, and moreover, it's considerably slower when compared to the majority of welding techniques. A similar process, called plasma arc welding, relies on a slightly different welding torch to generate a more focused welding arc and consequently is normally automated.

Although the aerospace industry is amongst the primary users of gas tungsten arc welding, the process is employed in several other areas. Several industries make use of GTAW for the purpose of welding thin workpieces, specifically nonferrous metals. It's made use of extensively during the manufacture of space vehicles, and is furthermore regularly used to weld small-diameter, thin-wall tubing including that made use of in the bicycle industry. Additionally, GTAW is oftentimes employed to produce root or first-pass welds for the purpose of piping of assorted sizes. In maintenance and repair work, the process is frequently utilized to repair tools and dies, particularly components constructed from aluminium and magnesium. Considering that the weld metal is not transferred directly across the electric arc similar to most open arc welding processes, a vast choice of welding filler metal is accessible to the welding engineer. Actually, no alternative welding process enables the welding of so many alloys in so many product configurations. Filler metal alloys, including elemental aluminium and chromium, could be lost through the electric arc as a consequence of volatilisation. This particular loss doesn't take place while using GTAW process. Considering that the resulting welds possess the same chemical integrity as the original base metal or match the base metals more closely, GTAW welds tend to be remarkably resistant to corrosion and cracking across long time periods, making GTAW the welding procedure of preference with regard to critical operations, for instance, sealing spent nuclear fuel canisters prior to burial.

TIG Electrodes

The electrode utilised in GTAW is manufactured out of tungsten or a tungsten alloy, due to the fact that tungsten has got the highest melting temperature involving pure metals, at 3,422 °C. Consequently, the electrode isn't consumed during welding, although some erosion identified as burn-off can happen. Electrodes can have either a clean finish or a ground finish - clean finish electrodes have been completely chemically cleaned, whereas ground finish electrodes have been completely ground to a uniform size and have a polished surface, making them optimal for heat conduction. The diameter of the electrode varies between 0.5 and 6.4 millimetres, and their length can range from 75 to 610 millimetres.

Several tungsten alloys have already been standardised by the International Organisation for Standardisation in ISO 6848 and the American Welding Society in AWS A5.12, respectively, intended for use in GTAW electrodes, and are summarised below.

• Pure tungsten electrodes (classified as WP or EWP) are general purpose and low cost electrodes. They have inferior heat resistance and electron emission. They find restricted use in AC welding of, for example, magnesium and aluminium.
• Thorium oxide (or thoria) alloy electrodes feature excellent arc performance and starting, making them popular general purpose electrodes. Nevertheless, thorium is to some degree radioactive, making inhalation of vapours and dust a health risk, together with disposal an environmental risk.
• Cerium oxide (or ceria) as an alloying element improves arc stability in addition to ease of starting whilst decreasing burn-off. Cerium addition is not as effective as thorium nonetheless is effective, and additionally cerium is not radioactive.
• An alloy of lanthanum oxide (or lanthana) provides a comparable effect as cerium, and is also not radioactive.
• Electrodes containing zirconium oxide (or zirconia) increase the current capacity whilst improving arc stability and starting at the same time additionally increasing electrode life.

Filler metals are likewise utilised in the majority of applications of GTAW, the significant exception being the welding of thin materials. Filler metals are obtainable having different diameters and tend to be manufactured from a variety of materials. In most instances, the filler metal in the form of a rod is added to the weld pool manually, however, many applications require an automatically fed filler metal, which frequently is stored on spools or coils.

Gas Metal Arc Welding (GMAW)

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Gas metal arc welding (GMAW), occasionally referred to by way of its sub-types metal inert gas (MIG) welding or metal active gas (MAG) welding, can be described as welding process wherein an electric arc forms between a consumable MIG wire electrode and the workpiece metals, which in turn heats the workpiece metals, causing them to melt and join. In addition to the wire electrode, a shielding gas feeds through the welding gun, which shields the process from atmospheric contamination.

The process can be semi-automatic or automatic. A constant voltage, direct current power source is typically used in combination with GMAW, however constant current systems, not to mention alternating current, can be employed. There are four primary methods of metal transfer in GMAW, identified as globular, short-circuiting, spray, and pulsed-spray, every one of which includes distinct properties as well as corresponding advantages and limitations.

Originally developed for the purpose of welding aluminium besides other non-ferrous materials, GMAW ended up being subsequently used on steels since it delivered faster welding time in comparison to alternative welding processes. The expense of inert gas restricted its use in steels until the usage of semi-inert gases including carbon dioxide started to be widespread. Additional advancements presented the process further versatility consequently it ended up being a highly utilised industrial process. Nowadays, GMAW is the most widespread industrial welding process, favored due to its versatility, speed along with the relative simplicity of adapting the process to robotic automation. As opposed to welding processes that don't use a shielding gas, which includes shielded metal arc welding, it's almost never made use of outdoors or in other areas of moving air. A associated process, called flux cored arc welding, typically doesn't employ a shielding gas, but alternatively uses an electrode wire which is hollow and filled with flux.

MIG Electrodes

The electrode is a metallic alloy wire, called a MIG wire, whose selection, alloy and size, is dependent predominantly on the composition of the metal being welded, the process variation made use of, joint design, along with the material surface conditions. Electrode selection considerably has influence on the mechanical properties of the weld and is particularly a critical factor of weld quality. Usually the finished weld metal requires mechanical properties comparable to those of the base material without having any kind of defects which includes discontinuities, entrained contaminants or porosity within the weld. To accomplish these objectives, a multitude of electrodes have been in existence. The different commercially obtainable electrodes incorporate deoxidising metals, for instance, silicon, manganese, titanium and aluminium, in small percentages intended for facilitating prevent oxygen porosity. Several contain denitriding metals which include titanium and zirconium to prevent nitrogen porosity. Conditional upon the process variation along with base material being welded, the diameters of the electrodes utilized in GMAW typically range between 0.7 and 2.4 mm, nonetheless could be as large as 4 mm. The smallest electrodes, normally up to 1.14 mm, are associated with the short-circuiting metal transfer process, whilst the most widespread spray-transfer process mode electrodes are typically at a minimum 0.9 mm.

MIG Shielding Gases

Shielding gases are crucial when it comes to gas metal arc welding to protect the welding area from atmospheric gases which include nitrogen and oxygen, which can lead to fusion defects, porosity, and weld metal embrittlement should they come in contact with the electrode, the arc, or the welding metal. This problem is typical to all arc welding processes; for instance, in the older Shielded-Metal Arc Welding process (SMAW), the electrode is coated with a solid flux that builds up a protective cloud of carbon dioxide when melted by the arc. In GMAW, on the other hand, the electrode wire does not possess a flux coating, and a separate shielding gas is needed to protect the weld. This eliminates slag, the hard residue from the flux which builds up subsequent to welding and is required to be chipped off to uncover the completed weld.

The selection of a shielding gas is dependent upon various factors, most significantly the type of material being welded along with the process variation being employed. The desirable rate of shielding-gas flow is dependent predominantly upon weld geometry, speed, current, the type of gas, and the metal transfer mode. Welding flat surfaces necessitates higher flow as compared to welding grooved materials, considering that the gas disperses more rapidly. Faster welding speeds, typically, mean that more gas is required to be supplied to deliver adequate coverage. Furthermore, higher current necessitates greater flow, and typically, more helium is necessary to produce adequate coverage as opposed to if argon is employed. Probably most importantly, the four primary variations of GMAW need differing shielding gas flow requirements.

Flux-Cored Arc Welding (FCAW)

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Flux-cored arc welding (FCAW or FCA) is a semi-automatic or automatic arc welding process. FCAW requires a continuously-fed consumable tubular electrode containing a flux in addition to a constant-voltage or, less typically, a constant-current welding power supply. An externally supplied shielding gas is occasionally employed, although usually the flux itself is relied upon to generate the necessary protection from the atmosphere, delivering both gaseous protection as well as liquid slag protecting the weld. The process is commonly employed in construction due to its high welding speed and portability.

FCAW was developed as an alternative to shielded metal arc welding (SMAW). The main advantage of FCAW over SMAW is the fact that usage of the stick electrodes utilised in SMAW is unnecessary. This aided FCAW to overcome the majority of the restrictions related to SMAW.

Types of FCAW

One version of FCAW requires no shielding gas. This is made possible by way of the flux core in the tubular consumable electrode. However, this particular core contains more than just flux. In addition, it contains a variety of ingredients which when exposed to the high temperatures of welding generate a shielding gas for protecting the arc. This type of FCAW is attractive considering that it is portable and typically has good penetration into the base metal. Additionally, windy conditions do not need to be considered. Several disadvantages usually are that this process can generate excessive, noxious smoke which makes it difficult to see the weld pool. Similar to all welding processes, the suitable electrode is required to be selected to obtain the required mechanical properties.

Yet another kind of FCAW relies on a shielding gas that needs to be supplied by an external source. This is referred to informally as dual shield" welding. This type of FCAW was developed principally for welding structural steels. Actually, considering that it makes use of both a flux-cored electrode as well as an external shielding gas, it could be claimed that it's a combination of gas metal (GMAW) along with flux-cored arc welding (FCAW). The foremost utilised shielding gases are either straight carbon dioxide or argon carbon dioxide blends. This particular form of FCAW is more effective for welding thicker and out-of-position metals. The slag created by the flux is additionally straightforward to remove. The primary advantages of this technique is that in a closed shop environment, it typically generates welds of improved and more consistent mechanical properties, with fewer weld defects as compared to either the SMAW or GMAW processes. In practice, furthermore, it enables a higher production rate, considering the fact that the operator doesn't have to halt periodically to get a new electrode, as is the scenario in SMAW. Nonetheless, similar to GMAW, it cannot be made use of in a windy environment for the reason that the loss of the shielding gas from air flow will produce porosity in the weld.

Submerged Arc Welding (SAW)

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Submerged arc welding (SAW) is a widespread arc welding process. The process requires a continuously fed consumable solid or tubular metal cored electrode. The molten weld and the arc zone are protected from atmospheric contamination by being "submerged" underneath a blanket of granular fusible flux composed of lime, silica, manganese oxide, calcium fluoride, and other compounds. When molten, the flux becomes conductive, and provides a current path between the electrode and the work. This particular thick layer of flux completely covers the molten metal consequently preventing spatter and sparks in addition to suppressing the intense ultraviolet radiation along with fumes which are associated with the shielded metal arc welding (SMAW) process.

SAW is generally operated in the automatic or mechanised mode, nonetheless, semi-automatic hand-held SAW guns along with pressurised or gravity flux feed delivery can be found. The process is commonly restricted to the flat or horizontal-fillet welding positions. Despite the fact that currents ranging from 300 to 2000 Amps are typically made use of, currents as high as 5000 Amps are also used in combination with multiple arcs.

Single or multiple (2 to 5) electrode wire variations of the process are in existence. SAW strip-cladding uses a flat strip electrode. DC or AC power can be utilized, and combinations of DC and AC are widespread on multiple electrode systems. Constant voltage welding power supplies are typically made use of; nonetheless, constant current systems in conjunction with a voltage sensing wire-feeder can be obtained.

SAW Electrodes

SAW filler material typically is a standard wire together with other special forms. This particular wire typically features a thickness of 1.6 mm to 6 mm. In certain scenarios, twisted wire could be employed to give the arc an oscillating movement. This helps fuse the toe of the weld to the base metal. The electrode composition is dependent upon the material being welded. Alloying elements can be added in the electrodes. Electrodes are obtainable to weld mild steels, high carbon steels, low and special alloy steels, stainless steel in addition to certain nonferrous alloys of copper and nickel. Electrodes are typically copper coated to counteract rusting and also to increase their electrical conductivity. Electrodes are available in straight lengths and coils. Their diameters can be 1.6, 2.0, 2.4, 3, 4.0, 4.8, and 6.4 mm. The approximate value of currents to weld using 1.6, 3.2 and 6.4 mm diameter electrodes are typically 150–350, 250–800 and 650–1350 Amps respectively.

Electroslag Welding (ESW)

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Electroslag welding (ESW) is a remarkably productive, single pass welding process for thick materials in a vertical or close to vertical position. ESW is comparable to electrogas welding, though the main distinction is the fact that the arc starts in a different location. An electric arc is initially struck by wire which is fed into the desired weld location and thereafter flux is added. Additional flux is added until the molten slag, reaching the tip of the electrode, extinguishes the arc. The wire is subsequently continuously fed through a consumable guide tube which is able to oscillate if required into the surfaces of the metal workpieces, and the filler metal are subsequently melted making use of the electrical resistance of the molten slag to cause coalescence. The wire along with tube subsequently progress along the workpiece while a copper retaining shoe which was put into position prior to starting, that can be water-cooled if required, is used to keep the weld between the plates which are being welded. Electroslag welding is employed predominantly to join low carbon steel plates and/or sections which are very thick. It can also be utilized on structural steel in case specific precautions are observed, and for large cross-section aluminium busbars. This technique utilizes a direct current (DC) voltage typically ranging from approximately 600 Amps and 40-50 Volts, higher currents are essential for thicker materials. Considering that the arc is extinguished, this isn't an arc process.

Benefits associated with the process comprise of its high metal deposition rates - it can lay metal at a rate between 15 and 20 kg per hour per electrode - as well as its capability to weld thick materials. Several welding processes necessitate several pass for welding thick workpieces, however ordinarily a single pass is sufficient for electroslag welding. The process is furthermore very efficient, considering that joint preparation along with materials handling are minimised whereas filler metal utilisation is high. The process is additionally safe as well as clean, without any arc flash and low weld splatter or distortion. Electroslag welding effortlessly lends itself to mechanisation, subsequently reducing the necessity for skilled manual welders. One electrode is normally employed to generate welds on materials having a thickness of 25 to 75 mm, and thicker pieces typically necessitate more electrodes. The maximum workpiece thickness which has ever been successfully welded has been a 0.91 m piece which required the simultaneous usage of six electrodes in order to complete.

Gas Welding

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The most widespread gas welding process is actually oxy-fuel welding, In oxy-fuel welding, a welding torch is employed to weld metals. Welding metal results when two pieces are heated to a temperature which produces a shared pool of molten metal. The molten pool is frequently supplied with additional metal called filler. Filler material selection depends upon the metals to be welded.

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. 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.

The level of heat applied to the metal is a function of the welding tip size, the speed of travel, along with the welding position. The flame size is dependent upon the welding tip size. The proper tip size is determined by the metal thickness as well as the joint design.

The welder will need to add the filler rod to the molten puddle. The welder also need to maintain the filler metal in the hot outer flame zone when not adding it to the puddle to protect filler metal from oxidation. The welding flame should not be permitted to burn off the filler metal. The metal is not going to wet into the base metal and will resemble a series of cold dots on the base metal. There is almost no strength in a cold weld. In the event the filler metal is effectively added to the molten puddle, the resulting weld is going to be stronger compared to the original base metal.

Electric Resistance Welding (ERW)

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Electric resistance welding (ERW) is a welding process in which metal parts in contact are permanently joined by way of heating them with an electric current, melting the metal at the joint. The electric current will be supplied to electrodes which additionally apply clamping pressure, or possibly can be induced by way of an external magnetic field. The electric resistance welding process may be additionally classified by way of the geometry of the weld along with the method of applying pressure to the joint: spot welding, seam welding, flash welding, projection welding, and so forth.

Various factors impacting heat or welding temperatures include the proportions of the workpieces, the metal coating or the lack of coating, the electrode materials, electrode geometry, electrode pressing force, electrical current and length of welding time. Smallish pools of molten metal are created at the point of maximum electrical resistance, the connecting or "faying" surfaces, as an electrical current of around 100 to 100,000 Amp is passed through the metal. Typically, resistance welding methods are efficient and additionally contribute to minimal pollution, nevertheless their applications are generally restricted to comparatively thin materials.

Spot welding is a widely used resistance welding method employed to join overlapping metal sheets upto 3 mm thick. Two electrodes are simultaneously employed to clamp the metal sheets together and also to pass current through the sheets. The main advantages of the method feature efficient energy usage, limited workpiece deformation, superior production rates, convenient automation, without any necessary filler materials. Weld strength is considerably lower than using alternative welding methods, making the process appropriate for merely specific applications. It's utilised extensively within the automotive industry - standard cars have thousands of spot welds made using industrial robots. A specialised method, called shot welding, are often used to spot weld stainless steel.

Similar to spot welding, seam welding relies upon a pair of electrodes in order to apply pressure together with current to join metal sheets. However, rather then pointed electrodes, wheel-shaped electrodes roll along the length of and frequently feed the workpiece, making it possible to create long continuous welds. This technique has been employed in the manufacture of beverage cans, although currently its applications are more limited. Other resistance welding methods comprise of butt welding, flash welding, projection welding, and upset welding.

Energy beam welding (EBW)

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Energy beam welding methods, specifically laser beam welding and electron beam welding, are comparatively cutting edge processes which have become prominent in high production applications. The two processes are very similar, differing especially in their source of power. Laser beam welding makes use of an extremely focused laser beam, while electron beam welding is performed within a vacuum and employs an electron beam. Each of these have a very high energy density, making deep weld penetration achievable along with minimizing the dimensions of the weld area. Both processes are exceedingly fast, as they are conveniently automated, making them remarkably productive. The most crucial disadvantages are their extremely high equipment costs, nonetheless these are decreasing along with increasing usage, in addition to a susceptibility to thermal cracking. Advancements in this field consist of laser-hybrid welding, that makes use of concepts from both laser beam welding as well as arc welding for the purpose of more enhanced weld properties, laser cladding, and x-ray welding.

Laser beam welding (LBW) can be described as welding technique employed to join pieces of metal or thermoplastics by making use of a laser. The laser beam supplies a concentrated heat source, enabling narrow, deep welds in addition to high welding rates. The process is generally employed in high volume applications employing automation, like for example the automotive industry. It's based on keyhole or penetration mode welding.

Laser beam welding features high power density, around the order of 1 MW/cm², which results in small heat-affected zones in addition to high heating and cooling rates. The spot size of the laser varies between 0.2 mm and 13 mm, although primarily smaller sizes are used for welding. The depth of penetration is proportional to the degree of power supplied, however is in addition also dependent upon the positioning of the focal point: penetration is maximised in the event the focal point is slightly below the surface of the workpiece. A continuous or pulsed laser beam can be employed depending upon the application. Millisecond-long pulses are used to weld thin materials which include razor blades whereas continuous laser systems are used for deep welds.

LBW is a versatile process, capable of welding carbon steels, HSLA steels, stainless steel, aluminium, and titanium. As a consequence of high cooling rates, cracking is often a challenge whenever welding high-carbon steels. The weld quality is high, comparable to that of electron beam welding. The speed of welding is proportional to the degree of power supplied but additionally depends upon the type and thickness of the workpieces. The high power capability of gas lasers make them specifically appropriate for high volume applications.

Electron-beam welding (EBW) can be described as fusion welding process where a beam of high-velocity electrons is applied to two materials to be joined. The workpieces melt and flow together given that the kinetic energy of the electrons is transformed into heat upon impact. EBW is normally conducted using vacuum conditions to circumvent dissipation of the electron beam.

The effectiveness of the electron beam is dependent upon several factors. The most crucial are the physical properties of the materials being welded, specifically the convenience with that they can be melted or vaporise under low-pressure conditions. Electron-beam welding is often so intense that loss of material as a consequence of evaporation or boiling during the process is required to be taken into consideration whenever welding. At lower values of surface power density, within the range of approximately 103 W/mm², the loss of material as a result of evaporation is negligible for the majority of metals, that is definitely favourable for welding. At higher power density, the material impacted by the beam could entirely evaporate in an exceedingly short time; if that's the case, it will be no longer electron-beam welding but turns into electron-beam machining.

To cover the diverse requirements, a multitude of variations are specially designed, differing in construction, working space volume, workpiece manipulators and beam power. Electron-beam generators or electron guns developed for welding applications will supply beams having power ranging from a few watts upto approximately one hundred kilowatts. "Micro-welds" involving tiny components can be actualised, together with deep welds upto 300 mm or higher, if required. Vacuum working chambers of various design ranging from volumes of only a few litres to the volume of several hundreds cubic meters are constructed.

Solid-state Welding

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Similar to other sorts of welding process, certain advanced welding methods don't entail the melting of the materials being joined. Probably the most widely used, ultrasonic welding, is employed to connect thin sheets or wires composed of metal or thermoplastic by means of vibrating them at high frequency as well as under high pressure. The equipment along with methods associated resemble that of resistance welding, but instead of electric current, vibration supplies the energy input. Welding metals utilizing this type of process doesn't require melting the materials; rather, the weld is created as a result of introducing mechanical vibrations horizontally under pressure. Whenever welding plastics, the materials need to have matching melting temperatures, and also the vibrations are introduced vertically. Ultrasonic welding is typically employed for generating electrical connections using aluminium or copper, along with being a really typical polymer welding process.

Yet another widespread process, explosion welding, involves the joining of materials by means of pushing them together under extremely high pressure. The energy from the impact plasticises the materials, creating a weld, despite the fact that only a limited amount of heat is generated. The process is typically employed for welding dissimilar materials, which include bonding aluminium to carbon steel inside ship hulls and stainless steel or titanium to carbon steel within petrochemical pressure vessels.

Other solid-state welding techniques consist of friction welding which include friction stir welding and friction stir spot welding, magnetic pulse welding, co-extrusion welding, cold welding, diffusion bonding, exothermic welding, high frequency welding, hot pressure welding, induction welding, and roll bonding.