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Gas metal arc welding
Gas metal arc welding

Arc welding uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. Gas metal arc welding (GMAW, sometimes referred to by its subtypes metal inert gas (MIG welding or metal active gas (MAG welding, is a semi-automatic or automatic A welding power supply is a device that provides an Electric current to perform Welding. An electric arc is an Electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive They can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes. Direct current ( DC) is the unidirectional flow of Electric charge. An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e The welding region is sometimes protected by some type of inert or semi-inert gas, known as a shielding gas, and/or an evaporating filler material. "Inert gases" is also used in a narrower sense for Noble gases An inert gas is any Gas that is not reactive with elements Shielding gases are inert or semi- Inert gases that are commonly used in several Welding processes most notably Gas metal arc welding and Gas tungsten The process of arc welding is widely used because of its low capital and running costs.

Contents

Development

While examples of forge welding go back to the Bronze Age and the Iron Age, arc welding did not come into practice until much later. Forge welding is a Welding process of heating two or more pieces of Metal and then hammering them together The term Bronze Age refers to a period in human cultural development when the most advanced Metalworking (at least in systematic and widespread use included techniques for This article is about the archaeological period known as the Iron Age for the mythological Iron Age see Ages of Man. In 1800, Humphry Davy discovered the electric arc, initiating the development of arc welding which continued with the inventions of metal electrodes by a Russian (N. Sir Humphry Davy 1st Baronet FRS MRIA (17 December 1778 &ndash 29 May 1829 was a British Chemist and inventor An electric arc is an Electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive G. Slavianoff) and an American (C.L. Coffin) in the late 1800s even as carbon arc welding, which used a carbon electrode, gained popularity. CL Coffin of Detroit was awarded for an Arc welding process using a metal Electrode. Carbon Arc Welding ( CAW) is a process which produces coalescence of metals by heating them with an arc between a nonconsumable Carbon ( Graphite) Electrode Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Around 1900, A. P. Strohmenger released in Britain a coated metal electrode which gave a more stable arc. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located In 1919, alternating current welding was invented by C. An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant J. Holslag but did not become popular for another decade. [1]

Competing welding processes such as resistance welding and oxyfuel welding were developed during this time as well,[2] but both, especially the latter, faced stiff competition from arc welding especially after metal coverings (known as flux) for the electrode, to stabilize the arc and shield the base material from impurities, continued to be developed. Resistance welding refers to a group of Welding processes that produce coalescence of Faying surfaces where heat to form the weld is generated by the resistance Concerning a. " for the verdict on this matter --> Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding In Metallurgy, a flux is a chemical cleaning agent which facilitates Soldering, Brazing, and Welding by removing Oxidation from [3] During the surge in the use of welding caused by World War I, arc welding became even more popular as the British constructed a ship, the Fulagar, with an entirely welded hull. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All The Americans also became more accepting of the new technology when the process allowed them to repair their ships quickly after a German attack in the New York Harbor at the beginning of the war. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. New York Harbor, a geographic term refers collectively to the rivers bays and tidal estuaries near the mouth of the Hudson River in the vicinity of New York City Arc welding was first applied to aircraft during the war as well, and some German airplane fuselages were constructed using this process. [4]

During the 1920s, major advances were made in welding technology, including the 1920 introduction of automatic welding in which electrode wire was continuously fed. Shielding gas became a subject receiving much attention as scientists attempted to protect welds from the effects of oxygen and nitrogen in the atmosphere. Shielding gases are inert or semi- Inert gases that are commonly used in several Welding processes most notably Gas metal arc welding and Gas tungsten Porosity and brittleness were the primary problems and the solutions that developed included the use of hydrogen, argon, and helium as welding atmospheres. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 This article pertains to the chemical element For other uses see Argon (disambiguation. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical [5] During the following decade, further advances allowed for the welding of reactive metals such as aluminum and magnesium. WikipediaNaming Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 This, in conjunction with developments in automatic welding, alternating current, and fluxes fed a major expansion of arc welding during the 1930s and then during World War II. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including [6]

During the middle of the century, many new welding methods were invented. Submerged arc welding was invented in 1930 and continues to be popular today. Submerged Arc Welding (SAW is a common Arc welding process Originally devolved by the Linde - Union Carbide Company Gas tungsten arc welding, after decades of development, was finally perfected in 1941 and gas metal arc welding followed in 1948, allowing for fast welding of non-ferrous materials but requiring expensive shielding gases. Gas tungsten arc welding ( GTAW) also known as tungsten inert gas (TIG welding, is an Arc welding process that uses a nonconsumable Tungsten Gas metal arc welding (GMAW, sometimes referred to by its subtypes metal inert gas (MIG welding or metal active gas (MAG welding, is a semi-automatic or automatic Ferrous, in the chemical science realm indicates a bivalent iron compound (+2 oxidation state (as opposed to Ferric, which indicates a trivalent iron compound (+3 oxidation Using a consumable electrode and a carbon dioxide atmosphere as a shielding gas, it quickly became the most popular metal arc welding process. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single In 1957, the flux-cored arc welding process debuted in which the self-shielded wire electrode could be used with automatic equipment, resulting in greatly increased welding speeds. Flux-cored arc welding (FCAW is a semi-automatic or automatic Arc welding process In that same year, plasma arc welding was invented. Plasma arc welding (PAW is an arc Welding process similar to Gas tungsten arc welding (GTAW Electroslag welding was released in 1958 and was followed by its cousin, electrogas welding, in 1961. Electroslag welding (ESW is a highly productive single pass Welding process for thick (greater than 25mm up to about 300mm materials in a vertical or close Electrogas welding (EGW is a continuous vertical position Arc welding process developed in 1961, in which an arc is struck between a consumable Electrode [7]

Power supplies

A constant current welding power supply capable of AC and DC
A constant current welding power supply capable of AC and DC

To supply the electrical energy necessary for arc welding processes, a number of different power supplies can be used. The most common classification is constant current power supplies and constant voltage power supplies. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical In arc welding, the voltage is directly related to the length of the arc, and the current is related to the amount of heat input. 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. [8]

The direction of current used in arc welding also plays an important role in welding. Consumable electrode processes such as shielded metal arc welding and gas metal arc welding generally use direct current, but the electrode can be charged either positively or negatively. In welding, the positively charged anode will have a greater heat concentration and, as a result, changing the polarity of the electrode has an impact on weld properties. An anode is an Electrode through which Electric current flows into a polarized electrical device If the electrode is positively charged, it will melt more quickly, increasing weld penetration and welding speed. Alternatively, a negatively charged electrode results in more shallow welds. [9] Non-consumable electrode processes, such as gas tungsten arc welding, can use either type of direct current, as well as alternating current. With direct current however, 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. [10] Alternating current rapidly moves between these two, resulting in medium-penetration welds. One disadvantage of AC, the fact that the arc must be re-ignited after every zero crossing, has been addressed with the invention of special power units that produce a square wave pattern instead of the normal sine wave, eliminating low-voltage time after the zero crossings and minimizing the effects of the problem. A square wave is a kind of Non-sinusoidal waveform, most typically encountered in Electronics and Signal processing. [11]

Consumable electrode methods

Shielded metal arc welding
Shielded metal arc welding

One of the most common types of arc welding is shielded metal arc welding (SMAW), which is also known as manual metal arc welding (MMA) or stick welding. Shielded metal arc welding (SMAW, also known as manual metal arc (MMA welding or informally as stick welding, is a manual Arc welding process that uses An electric current is used to strike an arc between the base material and a consumable electrode rod or 'stick'. The electrode rod is made of a material that is compatible with the base material being welded and is covered with a flux that protects the weld area from oxidation and contamination by producing CO2 gas during the welding process. In Metallurgy, a flux is a chemical cleaning agent which facilitates Soldering, Brazing, and Welding by removing Oxidation from Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single The electrode core itself acts as filler material, making a separate filler unnecessary. The process is very versatile, requiring little operator training and inexpensive equipment. However, 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. [12] Furthermore, the process is generally limited to welding ferrous materials, though specialty electrodes have made possible the welding of cast iron, nickel, aluminium, copper and other metals. Cast iron usually refers to grey cast iron, but identifies a large group of Ferrous Alloys which solidify with a Eutectic. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 WikipediaNaming Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 The versatility of the method makes it popular in a number of applications including repair work and construction. [13]

Gas metal arc welding (GMAW) is a semi-automatic or automatic welding process that uses a continuous wire feed as an electrode and an inert or semi-inert shielding gas to protect the weld from contamination. Gas metal arc welding (GMAW, sometimes referred to by its subtypes metal inert gas (MIG welding or metal active gas (MAG welding, is a semi-automatic or automatic Shielding gases are inert or semi- Inert gases that are commonly used in several Welding processes most notably Gas metal arc welding and Gas tungsten When using an inert gas as shield it is known as Metal Inert Gas (MIG) welding. A constant voltage, direct current power source is most commonly used with GMAW, but constant current systems as well as alternating current can be used. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical Direct current ( DC) is the unidirectional flow of Electric charge. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant GMAW welding speeds are relatively high due to the automatically fed continuous electrode, but is less versatile because it requires more equipment than the simpler SMAW process. Originally developed for welding aluminium and other non-ferrous materials in the 1940s, GMAW was soon applied to steels because it allowed for lower welding time compared to other welding processes. WikipediaNaming Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 Today, GMAW is commonly used in industries such as the automobile industry, where it is preferred for its versatility and speed. The automotive industry is the industry involved in the design development manufacture marketing and sale of Motor vehicles In 2007 more than 73 million motor vehicles Because it employs a shielding gas, however, it is rarely used outdoors or in areas of air volatility. [14]

A related process, flux-cored arc welding (FCAW), uses similar equipment but uses wire consisting of a steel electrode tube surrounding a powder fill material. Flux-cored arc welding (FCAW is a semi-automatic or automatic Arc welding process This cored wire is more expensive than the standard solid wire and generates extra shielding gas and/or slag, but it permits higher welding speed and greater metal penetration. [15]

Submerged arc welding (SAW) is a high-productivity automatic welding method in which the arc is struck beneath a covering layer of flux. Submerged Arc Welding (SAW is a common Arc welding process Originally devolved by the Linde - Union Carbide Company This increases arc quality, since contaminants in the atmosphere are blocked by the flux. The slag that forms on the weld generally comes off by itself and, combined with the use of a continuous wire feed, the weld deposition rate is high. Working conditions are much improved over other arc welding processes since the flux hides the arc and no smoke is produced. The process is commonly used in industry, especially for large products. [16] As the arc is not visible, it requires full automatization. In-position welding is not possible with SAW.

Non-consumable electrode methods

Gas tungsten arc welding (GTAW), or tungsten inert gas (TIG) welding, is a manual welding process that uses a non-consumable electrode made of tungsten, an inert or semi-inert gas mixture, and a separate filler material. Gas tungsten arc welding ( GTAW) also known as tungsten inert gas (TIG welding, is an Arc welding process that uses a nonconsumable Tungsten Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 Especially useful for welding thin materials, this method is characterized by a stable arc and high quality welds, but it requires significant operator skill and can only be accomplished at relatively low speeds. It can be used on nearly all weldable metals, though it is most often applied to stainless steel and light metals. In Metallurgy, stainless steel is defined as a Steel Alloy with a minimum of 11 It is often used when quality welds are extremely important, such as in bicycle, aircraft and naval applications. The bicycle, cycle, or bike is a pedal-driven, human-powered vehicle with two wheels attached to a frame, one behind [17] A related process, plasma arc welding, also uses a tungsten electrode but uses plasma gas to make the arc. Plasma arc welding (PAW is an arc Welding process similar to Gas tungsten arc welding (GTAW In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound 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 is much faster. It can be applied to all of the same materials as GTAW except magnesium; automated welding of stainless steel is one important application of the process. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 A variation of the process is plasma cutting, an efficient steel cutting process. This article is about the common Manufacturing process For various fictional weapons see Plasma rifle and Directed-energy weapon. [18]

Other arc welding processes include atomic hydrogen welding, carbon arc welding, electroslag welding, electrogas welding, and stud arc welding. Carbon Arc Welding ( CAW) is a process which produces coalescence of metals by heating them with an arc between a nonconsumable Carbon ( Graphite) Electrode Electroslag welding (ESW is a highly productive single pass Welding process for thick (greater than 25mm up to about 300mm materials in a vertical or close Electrogas welding (EGW is a continuous vertical position Arc welding process developed in 1961, in which an arc is struck between a consumable Electrode Stud welding is a form of Spot welding where a bolt or specially formed nut is welded onto another metal part

Corrosion issues

Some materials, notably high-strength steels, aluminium, and titanium alloys, are susceptible to hydrogen embrittlement. Hydrogen embrittlement (or hydrogen grooving) is the process by which various metals most importantly high-strength Steel, become brittle and crack following exposure If the electrodes used for welding contain traces of moisture, the water decomposes in the heat of the arc and the liberated hydrogen enters the lattice of the material, causing its brittleness. Electrodes for such materials, with special low-hydrogen coating, are delivered in sealed moisture-proof packagings. New electrodes can be used straight from the can, but when moisture absorption may be suspected, they have to be dried by baking (usually at 800-1000 °F) in a drying oven. Flux used has to be kept dry as well. In Metallurgy, a flux is a chemical cleaning agent which facilitates Soldering, Brazing, and Welding by removing Oxidation from [19]

Some austenitic stainless steels and nickel-based alloys are prone to intergranular corrosion. Austenite (or gamma phase iron is a metallic non-magnetic solid solution of Iron and an Alloying element In Metallurgy, stainless steel is defined as a Steel Alloy with a minimum of 11 Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has Intergranular corrosion ( IGC) also termed intergranular attack ( IGA) is a form of Corrosion where the boundaries of Crystallites When subjected to temperatures around 700 °C for too long time, chromium reacts with carbon in the material, forming chromium carbide and depleting the crystal edges of chromium, impairing their corrosion resistance in a process called sensitization. Chromium (ˈkroʊmiəm is a Chemical element which has the symbol Cr and Atomic number 24 Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Chromium carbide ( Cr 3 C 2 is an extremely hard refractory Ceramic material Such sensitized steel undergoes corrosion in the areas near the welds where the temperature-time was favorable for forming the carbide. This kind of corrosion is often termed weld decay.

Knifeline attack (KLA) is another kind of corrosion affecting welds, impacting steels stabilized by niobium. Intergranular corrosion ( IGC) also termed intergranular attack ( IGA) is a form of Corrosion where the boundaries of Crystallites Niobium (naɪˈoʊbiəm or columbium (/kəˈlʌmbiəm/ is a Chemical element that has the symbol Nb and Atomic number 41 Niobium and niobium carbide dissolves in steel at very high temperatures. Niobium carbide ( Nb[[Carbon C]] and Nb2C is an extremely hard refractory Ceramic material commercially used in Tool bits At some cooling regimes, niobium carbide does not precipitate, and the steel then behaves like unstabilized steel, forming chromium carbide instead. This affects only a thin zone several millimeters wide in the very vicinity of the weld, making it difficult to spot and increasing the corrosion speed. Structures made of such steels have to be heated in a whole to about 1950 °F, when the chromium carbide dissolves and niobium carbide forms. The cooling rate after this treatment is not important. [20]

Filler metal (electrode material) improperly chosen for the environmental conditions can make them corrosion-sensitive as well. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings There are also issues of galvanic corrosion if the electrode composition is sufficiently dissimilar to the materials welded, or the materials are dissimilar themselves. Galvanic corrosion is an Electrochemical process in which one Metal Corrodes preferentially when in electrical contact with a different type of metal Even between different grades of nickel-based stainless steels, corrosion of welded joints can be severe, despite that they rarely undergo galvanic corrosion when mechanically joined. [21]

Safety issues

Welding can be a dangerous and unhealthy practice without the proper precautions; however, with the use of new technology and proper protection the risks of injury or death associated with welding can be greatly reduced. Because many common welding procedures involve an open electric arc or flame, the risk of burns is significant. To prevent them, welders wear protective clothing in the form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat, flames, and sparks. A welder (also weldor, which term distinguishes the Tradesman from the equipment used to make welds is a Tradesman who specialises in Welding Personal protective equipment (PPE refers to protective Clothing, Helmets, Goggles, or other garment designed to protect the wearer's body or Leather is a material created through the Tanning of hides and Skins of Animals primarily Cattlehide The Tanning process A glove ( Middle English from Old English glof) is a type of Garment (and more specifically a Fashion Additionally, the brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes the inflammation of the cornea and can burn the retinas of the eyes. Arc eye, also known as welder's flash, bake eyes, corneal flash burns, or flash burns, is a painful ocular condition sometimes experienced by Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays The cornea is the transparent front part of the Eye that covers the iris, Pupil, and Anterior chamber. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Goggles and helmets with dark face plates are worn to prevent this exposure and, in recent years, new helmet models have been produced featuring a face plate that self-darkens upon exposure to high amounts of UV light. Goggles or safety glasses are forms of protective eyewear that usually enclose or protect the eye area in order to prevent particulates water or chemicals from Welding helmets are headgear used when performing certain types of Welding to protect the eyes face and neck from flash burn Ultraviolet light, sparks and heat To protect bystanders, transparent welding curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets. [22]

In 1970, a Swedish doctor, Åke Sandén, developed a new type of welding goggles that used a multilayer interference filter to block most of the light from the arc. In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern He had observed that most welders could not see well enough, with the mask on, to strike the arc, so they would flip the mask up, then flip it down again once the arc was going: this exposed their naked eyes to intense light. By coincidence, the spectrum of an electric arc has a notch in it, which coincides with the yellow sodium line. A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 Thus, a welding shop could be lit by sodium vapor lamps or daylight, and the welder could see well to strike the arc. A sodium vapor lamp is a Gas discharge lamp which uses Sodium in an excited state to produce Light The Swedish government required these masks to be used for arc welding, but they were not used in the United States. They may have disappeared. [23]

Welders are also often exposed to dangerous gases and particulate matter. Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides. Smoke is the collection of airborne solid and liquid Particulates and Gases ref> ''Smoke Production and Properties'' - SFPE Handbook of Fire Protection Engineering An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Toxicity is the degree to which a substance is able to damage an exposed organism Additionally, many processes produce various gases (most commonly carbon dioxide and ozone, but others as well) that can prove dangerous if ventilation is inadequate. OZONE is an object oriented Operating system written in the C programming language. Furthermore, the use of compressed gases and flames in many welding processes pose 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. [24]

See also

References

  1. ^ Cary, Howard B. Robot welding is the use of mechanized programmable tools ( Robots, which completely automate a Welding process by both performing the weld and handling the part Signature Image Processing (SIP is a technology for analysing electrical data collected from welding processes—usually automated robotic welding A welder (also weldor, which term distinguishes the Tradesman from the equipment used to make welds is a Tradesman who specialises in Welding and Scott C. Helzer (2005). Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Modern Welding Technology. Upper Saddle River, New Jersey: Pearson Education. New Jersey ( is a state in the Mid-Atlantic and Northeastern regions of the United States. ISBN 0131130293 p. 5-6.
  2. ^ Cary & Helzer, p. 6
  3. ^ Weman, Klas (2003). Welding processes handbook. New York: CRC Press LLC. ISBN 0-8493-1773-8. p. 26.
  4. ^ Lincoln Electric (1994). Lincoln Electric ( is a company in Cleveland, Ohio, United States that manufactures Arc welding equipment Year 1994 ( MCMXCIV) was a Common year starting on Saturday (link will display full 1994 Gregorian calendar) The Procedure Handbook of Arc Welding. Cleveland: Lincoln Electric. Cleveland is a City in the US state of Ohio and the County seat of Cuyahoga County, the most populous county in the state ISBN 99949-25-82-2. p. 1. 1-5.
  5. ^ Cary & Helzer, p. 7.
  6. ^ Lincoln Electric, 1. 1-6.
  7. ^ Cary and Helzer, p. 9
  8. ^ Cary and Helzer, p. 246-49.
  9. ^ Kalpakjian, Serope and Steven R. Schmid (2001). Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Manufacturing Engineering and Technology. Prentice Hall. ISBN 0-201-36131-0. p. 780.
  10. ^ Lincoln Electric, 5. 4. 5.
  11. ^ Weman, p. 16.
  12. ^ Weman, 63.
  13. ^ Cary & Helzer, p. 103.
  14. ^ Lincoln Electric, 5. 4. 3.
  15. ^ Weman, p. 53.
  16. ^ Weman, p. 68.
  17. ^ Weman, p. 31.
  18. ^ Weman, p. 37-38.
  19. ^ Drive Off Moisture and Get Better Welds
  20. ^ Intergranular Corrosion
  21. ^ Galvanic Corrosion
  22. ^ Cary & Helzer, p. 42, 49-51.
  23. ^ Papers of the International Shipyard Health Conference, U. S. C. School of Medicine, 1973
  24. ^ Cary & Helzer, p. 52-62.

Further reading

External links


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