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Gas tungsten arc welding

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133-578: Gas tungsten arc welding ( GTAW , also known as tungsten inert gas welding or TIG , and heliarc welding when helium is used) is an arc welding process that uses a non-consumable tungsten electrode to produce the weld . The weld area and electrode are protected from oxidation or other atmospheric contamination by an inert shielding gas ( argon or helium ). A filler metal is normally used, though some welds, known as ' autogenous welds ', or ' fusion welds ' do not require it. A constant-current welding power supply produces electrical energy, which

266-473: A liquid crystal -type face plate that self-darkens upon exposure to the bright light of the struck arc. Transparent welding curtains, made of a strongly colored polyvinyl chloride plastic film, are often used to shield nearby workers and bystanders from exposure to the UV light from the electric arc. Welders are also often exposed to dangerous gases and particulate matter. While the process doesn't produce smoke,

399-452: A clean finish or a ground finish—clean finish electrodes have been chemically cleaned, while ground finish electrodes have been ground to a uniform size and have a polished surface, making them optimal for heat conduction. The diameter of the electrode can vary between 0.5 and 6.4 millimetres (0.02 and 0.25 in), and their length can range from 75 to 610 millimetres (3.0 to 24.0 in). A number of tungsten alloys have been standardized by

532-489: A clean weld pool during welding, the shielding gas flow should be sufficient and consistent so that the gas covers the weld and blocks impurities in the atmosphere. GTAW in windy or drafty environments increases the amount of shielding gas necessary to protect the weld, increasing the cost and making the process unpopular outdoors. The level of heat input also affects weld quality. Low heat input, caused by low welding current or high welding speed, can limit penetration and cause

665-421: A coated metal electrode which gave a more stable arc. In 1905, Russian scientist Vladimir Mitkevich proposed the usage of three-phase electric arc for welding. In 1919, alternating current welding was invented by C. J. Holslag but did not become popular for another decade. Competing welding processes such as resistance welding and oxyfuel welding were developed during this time as well; but both, especially

798-415: A cold or hot filler wire into the weld area and dabbing (or oscillating) it into the welding arc. It can be used in conjunction with pulsed current, and is used to weld a variety of alloys, including titanium, nickel, and tool steels. Common applications include rebuilding seals in jet engines and building up saw blades, milling cutters , drill bits , and mower blades. Arc welding Arc welding

931-477: A condition called arc eye in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Welding goggles and helmets with dark face plates—much darker than those in sunglasses or oxy-fuel goggles —are worn to prevent this exposure. In recent years, new helmet models have been produced featuring a face plate which automatically self-darkens electronically. To protect bystanders, transparent welding curtains often surround

1064-412: A constant current power supply with a stick electrode operates at about 20 volts. 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 general, the positively charged anode will have

1197-422: A consumable electrode and a carbon dioxide atmosphere as a shielding gas, it quickly became the most popular metal arc welding process. 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. In that same year, plasma arc welding was invented. Electroslag welding was released in 1958 and

1330-488: 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. As the arc is not visible, it is typically automated. SAW is only possible in the 1F (flat fillet), 2F (horizontal fillet), and 1G (flat groove) positions. Gas tungsten arc welding (GTAW), or tungsten/inert-gas (TIG) welding,

1463-426: A continuously fed consumable wire acting as both electrode and filler metal, along with an inert or semi-inert shielding gas flowed around the wire to protect the weld site from contamination. Constant voltage, direct current power source is most commonly used with GMAW, but constant current alternating current are used as well. With continuously fed filler electrodes, GMAW offers relatively high welding speeds; however

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1596-613: A danger of the low welding voltage being "stepped up" to much higher voltages, so extra grounding cables may be required. Certain welding machines which use a high frequency alternating current component have been found to affect pacemaker operation when within 2 meters of the power unit and 1 meter of the weld site. 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. In 1800, Humphry Davy discovered

1729-399: 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 from heat and sparks is significant. To prevent them, welders wear protective clothing in

1862-408: A drying oven. Flux used has to be kept dry as well. Some austenitic stainless steels and nickel -based alloys are prone to intergranular corrosion . When subjected to temperatures around 700 °C (1,300 °F) for too long a time, chromium reacts with carbon in the material, forming chromium carbide and depleting the crystal edges of chromium, impairing their corrosion resistance in

1995-402: A filler metal into the weld area with one hand while manipulating the welding torch in the other. Maintaining a short arc length, while preventing contact between the tungsten electrode and the workpiece, is also important. To strike the welding arc, a high-frequency generator (similar to a Tesla coil ) provides an electric spark . This spark is a conductive path for the welding current through

2128-408: A given arc welder can safely be used. For example, an 80 A welder with a 60% duty cycle must be "rested" for at least 4 minutes after 6 minutes of continuous welding. Failure to observe duty cycle limitations could damage the welder. Commercial- or professional-grade welders typically have a 100% duty cycle. One of the most common types of arc welding is shielded metal arc welding (SMAW), which

2261-524: A greater heat concentration (around 60%). "Note that for stick welding in general, DC+ polarity is most commonly used. It produces a good bead profile with a higher level of penetration. DC− polarity results in less penetration and a higher electrode melt-off rate. It is sometimes used, for example, on thin sheet metal in an attempt to prevent burn-through." "With few exceptions, electrode-positive (reversed polarity) results in deeper penetration. Electrode-negative (straight polarity) results in faster melt-off of

2394-407: A hazard of electric shock for the operators. Locations such as ship's hulls, storage tanks, metal structural steel, or in wet areas are usually at earth ground potential and operators may be standing or resting on these surfaces during operating of the electric arc. Welding machines operating off AC power distribution systems must isolate the arc circuit from earth ground to prevent insulation faults in

2527-518: A metal coated in oil to prevent the rod oxidising if needed or in more complicated welding of metals the rod would be coated in a "flux" that was not an active flux but a method of protecting the welding rods from oxidisation during storage (the major examples of this were rods for welding; pure aluminium, duralumin, magnesium/aluminium alloy and stainless steel rods used for repairing ultra high grade carbon steel as in WW2 Sherman tanks). At this time

2660-410: A number of other areas. Many industries use GTAW for welding thin workpieces, especially nonferrous metals. It is used extensively in the manufacture of space vehicles and is also frequently employed to weld small-diameter, thin-wall tubing such as that used in the bicycle industry. In addition, GTAW is often used to make root or first-pass welds for piping of various sizes. In maintenance and repair work,

2793-400: A number of variations exist. Among the most popular are the pulsed-current, manual programmed, hot-wire, dabber, and increased penetration GTAW methods. Manual gas tungsten arc welding is a relatively difficult welding method, due to the coordination required by the welder. Similar to torch welding, GTAW normally requires two hands, since most applications require that the welder manually feed

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2926-478: A process called sensitization . 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 . Niobium and niobium carbide dissolves in steel at very high temperatures. At some cooling regimes, niobium carbide does not precipitate, and

3059-492: 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

3192-435: A result is often automated. After the discovery of the short pulsed electric arc in 1801 by Humphry Davy and of the continuous electric arc in 1802 by Vasily Petrov , arc welding developed slowly. C. L. Coffin had the idea of welding in an inert gas atmosphere in 1890, but even in the early 20th century, welding non-ferrous materials such as aluminum and magnesium remained difficult because these metals react rapidly with

3325-410: A self-cleaning effect, removing the thin, refractory aluminum oxide layer that forms on aluminum within minutes of exposure to air. This oxide layer must be removed for welding to occur. When alternating current is used, pure tungsten electrodes or zirconiated tungsten electrodes are preferred over thoriated electrodes, as the latter are more likely to "spit" electrode particles across the welding arc into

3458-419: A shielding gas source. GTAW welding torches are designed for either automatic or manual operation and are equipped with cooling systems using air or water. The automatic and manual torches are similar in construction, but the manual torch has a handle while the automatic torch normally comes with a mounting rack. The angle between the centerline of the handle and the centerline of the tungsten electrode, known as

3591-470: A stainless steel wire brush or chemical process can remove oxides from the surfaces of metals like aluminum. Rust on steels can be removed by first grit blasting the surface and then using a wire brush to remove any embedded grit. These steps are especially important when negative polarity direct current is used, because such a power supply provides no cleaning during the welding process, unlike positive polarity direct current or alternating current. To maintain

3724-441: A torch are made of hard alloys of copper or brass so it can transmit current and heat effectively. The tungsten electrode must be held firmly in the center of the torch with an appropriately sized collet , and ports around the electrode provide a constant flow of shielding gas. Collets are sized according to the diameter of the tungsten electrode they hold. The body of the torch is made of heat-resistant, insulating plastics covering

3857-550: A variety of other-than-flat positions, depending on the skill of the welder and the materials being welded. Aluminum and magnesium are most often welded using alternating current, but the use of direct current is also possible, depending on the properties desired. Before welding, the work area should be cleaned and may be preheated to 175 to 200 °C (347 to 392 °F) for aluminum or to a maximum of 150 °C (302 °F) for thick magnesium workpieces to improve penetration and increase travel speed. Alternating current can provide

3990-418: A varying arc length. When used with alternating current, argon shielding results in high weld quality and good appearance. Another common shielding gas, helium, is most often used to increase the weld penetration in a joint, to increase the welding speed, and to weld metals with high heat conductivity, such as copper and aluminum. A significant disadvantage is the difficulty of striking an arc with helium gas, and

4123-411: A weld with pinholes, which is weaker than a typical weld. If the amount of current used exceeds the capability of the electrode, tungsten inclusions in the weld may result. Known as tungsten spitting, this can be identified with radiography and can be prevented by changing the type of electrode or increasing the electrode diameter. In addition, if the electrode is not well protected by the gas shield or

Gas tungsten arc welding - Misplaced Pages Continue

4256-473: Is a welding process that is used to join metal to metal by using electricity to create enough heat to melt metal, and the melted metals, when cool, result in a binding of the metals. It is a type of welding that uses a welding power supply to create an electric arc between a metal stick (" electrode ") and the base material to melt the metals at the point of contact. Arc welding power supplies can deliver either direct (DC) or alternating (AC) current to

4389-523: Is a great deal brighter, subjecting operators to strong ultraviolet light. The welding arc has a different range and strength of UV light wavelengths from sunlight, but the welder is very close to the source and the light intensity is very strong. Potential arc light damage includes accidental flashes to the eye or arc eye and skin damage similar to strong sunburn . Operators wear opaque helmets with dark eye lenses and full head and neck coverage to prevent this exposure to UV light. Modern helmets often feature

4522-421: 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. 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

4655-405: Is also known as manual metal arc welding (MMAW) or stick welding. 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 gives off vapors that serve as a shielding gas and provide a layer of slag, both of which protect

4788-548: Is chosen to help form the bond, and this filler metal can be the same as one of the base materials (for example, using a stainless steel filler metal with stainless steel and carbon steel as base materials), or a different metal (such as the use of a nickel filler metal for joining steel and cast iron ). Very different materials may be coated or "buttered" with a material compatible with particular filler metal, and then welded. In addition, GTAW can be used in cladding or overlaying dissimilar materials. When welding dissimilar metals,

4921-497: Is commonly used as a shielding gas for DCEN welding of aluminum. Shielding gases with high helium contents are often used for higher penetration in thicker materials. Thoriated electrodes are suitable for use in DCEN welding of aluminum. Direct current with a positively charged electrode (DCEP) is used primarily for shallow welds, especially those with a joint thickness of less than 1.6 mm (0.063 in). A thoriated tungsten electrode

5054-500: Is commonly used, along with pure argon shielding gas. For GTAW of carbon and stainless steels, the selection of filler material is important to prevent excessive porosity. Oxides on the filler material and workpieces must be removed before welding to prevent contamination, and immediately prior to welding, alcohol or acetone should be used to clean the surface. Preheating is generally not necessary for mild steels less than one inch thick, but low alloy steels may require preheating to slow

5187-471: Is conducted across the arc through a column of highly ionized gas and metal vapors known as a plasma . The process grants the operator greater control over the weld than competing processes such as shielded metal arc welding and gas metal arc welding , allowing stronger, higher-quality welds. However, TIG welding is comparatively more complex and difficult to master, and furthermore, it is significantly slower than most other welding techniques. TAG welding

5320-402: Is gas tungsten arc welding (GTAW). Linde Air Products developed a wide range of air-cooled and water-cooled torches, gas lenses to improve shielding, and other accessories that increased the use of the process. Initially, the electrode overheated quickly and, despite tungsten's high melting temperature , particles of tungsten were transferred to the weld. To address this problem, the polarity of

5453-404: 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. Under normal arc length conditions,

Gas tungsten arc welding - Misplaced Pages Continue

5586-461: Is known as the pulse current, while the lower current level is called the background current. During the period of pulse current, the weld area is heated and fusion occurs. Upon dropping to the background current, the weld area is allowed to cool and solidify. Pulsed-current GTAW has a number of advantages, including lower heat input and consequently a reduction in distortion and warpage in thin workpieces. In addition, it allows for greater control of

5719-465: Is most commonly used to weld stainless steel and nonferrous materials, such as aluminum and magnesium, but it can be applied to nearly all metals, with a notable exception being zinc and its alloys. Its applications involving carbon steels are limited not because of process restrictions, but because of the existence of more economical steel welding techniques, such as gas metal arc welding and shielded metal arc welding. Furthermore, GTAW can be performed in

5852-461: 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 marine applications. 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

5985-525: Is not important. Filler metal (electrode material) improperly chosen for the environmental conditions can make them corrosion -sensitive as well. There are also issues of galvanic corrosion if the electrode composition is sufficiently dissimilar to the materials welded, or the materials are dissimilar themselves. 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. Welding can be

6118-507: Is the manufacturing and distribution of atmospheric gases, including oxygen , nitrogen , argon , rare gases , and process gases, including carbon dioxide , helium , hydrogen , ammonia, electronic gases, specialty gases, and acetylene . The company was formed by the 2018 merger of Linde AG of Germany (founded in 1879) and Praxair (founded in 1907 as Linde Air Products Company) of the United States. The resulting holding company

6251-414: Is used for thin workpieces, but helium can be introduced as thickness increases. Welding dissimilar metals often introduce new difficulties to GTAW welding, because most materials do not easily fuse to form a strong bond. However, welds of dissimilar materials have numerous applications in manufacturing, repair work, and the prevention of corrosion and oxidation . In some joints, a compatible filler metal

6384-437: Is used in the mechanized welding of light gauge stainless steel, but because hydrogen can cause porosity, its uses are limited. Similarly, nitrogen can sometimes be added to argon to help stabilize the austenite in austenitic stainless steels and increase penetration when welding copper. Due to porosity problems in ferritic steels and limited benefits, however, it is not a popular shielding gas additive. Gas Tungsten Arc Welding

6517-404: Is widely used in construction because of its high welding speed and portability. Submerged arc welding (SAW) is a high-productivity welding process in which the arc is struck beneath a covering layer of granular 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

6650-481: The Forbes Global 2000 . The company has two principal business areas: gas ( industrial gases and medical gases), and engineering, procurement, and construction . In the industrial gas area, the company uses the brand names Linde, AGA, BOC , TIG, Mox-Linde Gases , Afrox, Sigas and PanGas. HiQ is used as an identifier for high purity and premium specialty gases across all of these business brand names. In

6783-654: The Heylandt Works . Following World War I , Linde's U.S. assets were confiscated. They were incorporated into the Union Carbide Corporation (UCC) as the Linde Air Products division in 1917. Eventually, in 1992, this part of Union Carbide was spun off as Union Carbide Industrial Gases Inc., and renamed Praxair. In 2018 this became part of Linde when Linde merged with Praxair. In the years of Nazi Germany , Linde AG benefited from

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6916-633: The International Organization for Standardization and the American Welding Society in ISO 6848 and AWS A5.12, respectively, for use in GTAW electrodes, and are summarized in the adjacent table. Filler metals are also used in nearly all applications of GTAW, the major exception being the welding of thin materials. Filler metals are available with different diameters and are made of a variety of materials. In most cases,

7049-769: The Linde Air Products Factory , his first plant in America at Buffalo, New York . In addition to plants for air separation , in 1906, Linde engineers started working with others on processes to separate the constituents of water gas . This work lead to the 1909 invention of the Linde–Frank–Caro process to produce hydrogen and carbon monoxide , which were further key feedstocks for the emerging chemicals industry. In addition to his interests in refrigeration, Carl von Linde had also partnered with Hugo Güldner and Georg Krauß and others in 1904 to form

7182-399: The toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, many processes produce various gases (most commonly carbon dioxide and ozone , but others as well) that can prove dangerous if ventilation is inadequate. While the open-circuit voltage of an arc welding machine may be only a few tens of volts up to about 120 volts, even these low voltages can present

7315-428: The 1950s, as the process continued to gain popularity, some users turned to carbon dioxide as an alternative to the more expensive welding atmospheres consisting of argon and helium , but this proved unacceptable for welding aluminum and magnesium because it reduced weld quality, so it is rarely used with GTAW today. The use of any shielding gas containing an oxygen compound, such as carbon dioxide, quickly contaminates

7448-854: The Americas, Asia & Eastern Europe, and South Pacific & Africa. These segments are subdivided into eight Regional Business Units (RBUs). The Gases Division also includes the two Global Business Units (GBUs) – Healthcare (medical gases) and Tonnage (on-site) – and the two Business Areas (BAs) – Merchant & Packaged Gases (liquefied and cylinder gases) and Electronics (electronic gases). The product range includes hydrogen, acetylene, carbon monoxide , carbon dioxide , shielding gases for welding applications, noble gases and specialty gases, oxygen, nitrogen, and argon, all of which are manufactured in Linde's air separation plants. Linde Healthcare provides pharmaceutical and medical gas products and services for

7581-681: The Güldner Motoren-Gesellschaft mbH in Munich, which was moved to Aschaffenburg in 1906. Linde took full ownership of the company in 1929, and from this origin developed a business manufacturing first engines and tractors, and then from the 1950s onwards, a range of mechanical handling equipment such as fork lift trucks. Linde also acquired the Aktiengesellschaft für Industriegasverwertung ( English : Corporation for Industry Gas Utilization), commonly referred to as

7714-524: The Linde name from Praxair . In 2000, the company completed the acquisition of AGA AB of Sweden for $ 3.71 billion. In the early 2000, Brazilian auction was invented as a new type of auctions to trade gas by electronic auctions for Linde plc in Brazil . In 2004, the company sold its refrigeration division to Carrier Corporation for €325 million. In September 2006, Linde acquired BOC for €11.7 billion in cash. Linde's forklift business

7847-507: The Praxair merger. On 31 October 2018, the merger was completed except finalising divestitures required by the respective antitrust authorities. On 1 March 2019 the company completed divestitures required by US antitrust authorities. On 28 February 2019, Matheson acquired Linde HyCO, divested to comply with the regulatory terms of the Praxair merger. On 9 August 2019 Linde partnered with CarbonCure Technologies. On 29 August 2019,

7980-451: The TAG name as not specific and has fallen out of favour although the basic revolutionary process remains the same. TIG welding is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminium , magnesium , and copper alloys. A related process, plasma arc welding , uses a slightly different welding torch to create a more focused welding arc and as

8113-597: The acquisition of Air Liquide Korea's industrial merchant & electronics and liquid bulk air gases divisions, based in South Korea. In early June 2017, after almost a year of on-and-off negotiations, Linde and Praxair , the successor to UCC's Linde Air Products division, agreed to merge. In July 2018, the company agreed to sell certain business in North and South American assets to Messer Group and CVC Capital Partners for $ 3.3 billion to gain regulator approval for

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8246-399: The air, resulting in porous, dross -filled welds. Processes using flux-covered electrodes did not satisfactorily protect the weld area from contamination. To solve the problem, bottled inert gases were used in the beginning of the 1930s. A few years later, a direct current , gas-shielded welding process emerged in the aircraft industry for welding magnesium. In early 1940s Northrop Aircraft

8379-407: The arc distance and voltage change. This is important because most applications of GTAW are manual or semiautomatic, requiring that an operator hold the torch. Maintaining a suitably steady arc distance is difficult if a constant voltage power source is used instead since it can cause dramatic heat variations and make welding more difficult. The preferred polarity of the GTAW system depends largely on

8512-521: The armaments production: The Heylandt-Gesellschaft für Apparatebau supplied the German rocket program , other branches produced welding equipment and engines for the armaments industry. In 1941, Linde manufactured oxygen and helium installations for IG Farben at the Auschwitz concentration camp . Three further planned installations were not installed due to the course of war. According to estimates of

8645-749: The brewing and food industries. Following success in this market, he moved on to developing lower temperature systems resulting in 1895 in a patent covering the liquefaction of air. Out of this work his company developed equipment for the separation of air and other gases. Linde's process was patented in 1902 and immediately exploited by the first large-scale air separation plant installed in Linde's works in Höllriegelskreuth , near Munich in 1903. In 1906, Carl Von Linde decided to expand his oxygen extraction company overseas, targeting America, where no other companies had attempted industrial scale oxygen extraction. Along with Cecil Lightfoot, in 1907, he opened

8778-450: The brightness of the arc in GTAW can break down surrounding air to form ozone and nitric oxides. The ozone and nitric oxides react with lung tissue and moisture to create nitric acid and ozone burn. Ozone and nitric oxide levels are moderate, but exposure duration, repeated exposure, and the quality and quantity of fume extraction, and air change in the room must be monitored. Welders who do not work safely can contract emphysema and oedema of

8911-573: The company acquired a 10% stake in Hydrospider, a Swiss producer and supplier of hydrogen derived from renewable energy sources. In October 2019, the company invested £28 million in ITM Power , a British manufacturer of polymer electrolyte membrane electrolyzers for hydrogen production via electro-chemical splitting of water into hydrogen and oxygen. In January 2020, the company sold its LifeGas division. In April 2020, Gasum acquired

9044-683: The company acquired the Belgium, France, Germany, Portugal and Spain homecare business of Air Products & Chemicals for €590 million. In August 2012, the company acquired Lincare Holdings , a healthcare gas provider in the US for US$ 4.6 billion to become the largest home care gas supplier in North America. In December 2012, the company acquired homecare company Calea France SAS. In February 2016, Lincare Holdings acquired American HomePatient, Inc. In December 2016, Linde Korea completed

9177-406: The company for mid-1944, between 400 and 500 people were used as forced labourers in production plants. The company claimed that 75% of its production facilities were destroyed during the war. In 1958, the company tested a hydraulic drive system in the "Hydrocar". In 1989, the company acquired Lansing Bagnall , a British forklift manufacturer. In 1996, the company acquired the rights to

9310-609: The company's LNG and Biogas business in Sweden and Norway. In 2021 Linde and the Turkish construction company Renaissance Heavy Industries were awarded a contract to build a Liquified Natural Gas terminal at Ust-Luga in Russia. Following the 2022 Russian invasion of Ukraine , sanctions were introduced which restricted Linde completing the contract. Russia accordingly froze assets of Linde in Russia, who has an exposure of €1 billion in

9443-411: The cooling process and prevent the formation of martensite in the heat-affected zone . Tool steels should also be preheated to prevent cracking in the heat-affected zone. Austenitic stainless steels do not require preheating, but martensitic and ferritic chromium stainless steels do. A DCEN power source is normally used, and thoriated electrodes, tapered to a sharp point, are recommended. Pure argon

9576-421: The country's attempt to become self-sufficient by refraining from imports of synthetic fuel and rubber . In 1935, general manager Friedrich Linde received the title of Wehrwirtschaftsführer , which underlined the national importance of Linde AG and allowed the company to further benefit from the German rearmament . Before and during World War II , all departments of Linde AG were in some way involved in

9709-545: The decreased weld quality associated with a varying arc length. Argon-helium mixtures are also frequently utilized in GTAW, since they can increase control of the heat input while maintaining the benefits of using argon. Normally, the mixtures are made with primarily helium (often about 75% or higher) and a balance of argon. These mixtures increase the speed and quality of the AC welding of aluminum, and also make it easier to strike an arc. Another shielding gas mixture, argon- hydrogen ,

9842-404: The diameter of the electrode, but there are no hard rules. The welder judges the effectiveness of the shielding and increases the nozzle size to increase the area protected by the external gas shield as needed. The nozzle must be heat resistant and thus is normally made of alumina or a ceramic material, but fused quartz , a high purity glass, offers greater visibility. Devices can be inserted into

9975-489: The electric arc from volatilization. This loss does not occur with the GTAW process. Because the resulting welds have the same chemical integrity as the original base metal or match the base metals more closely, GTAW welds are highly resistant to corrosion and cracking over long time periods, making GTAW the welding procedure of choice for critical operations like sealing spent nuclear fuel canisters before burial. Gas tungsten arc welding, because it affords greater control over

10108-417: The electrode advances, but it is always kept inside the gas shield to prevent oxidation of its surface and contamination of the weld. Filler rods composed of metals with a low melting temperature, such as aluminum, require that the operator maintain some distance from the arc while staying inside the gas shield. If held too close to the arc, the filler rod can melt before it makes contact with the weld puddle. As

10241-399: The electrode and the workpiece. In order to initially create the arc, the welding area is flooded with inert gas and a high strike voltage (typically 1 kV per 1 mm) is generated by the welding machine to overcome the electric resistivity of the atmosphere surrounding the welding area. With the arc established, the voltage is lowered and current flows between the work piece and electrode. Despite

10374-543: The electrode and, therefore, faster deposition rate." Non-consumable electrode processes, such as gas tungsten arc welding, can use either type of direct current (DC), as well as alternating current (AC). 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. Alternating current rapidly moves between these two, resulting in medium-penetration welds. One disadvantage of AC,

10507-548: The electrode to the base material, as in DCEN, electrons go the other direction, causing the electrode to reach very high temperatures. To help it maintain its shape and prevent softening, a larger electrode is often used. As the electrons flow toward the electrode, ionized shielding gas flows back toward the base material, cleaning the weld by removing oxides and other impurities and thereby improving its quality and appearance. Alternating current, commonly used when welding aluminum and magnesium manually or semi-automatically, combines

10640-439: The electrode was changed from positive to negative, but the change made it unsuitable for welding many non-ferrous materials. Finally, the development of alternating current units made it possible to stabilize the arc and produce high quality aluminum and magnesium welds. Developments continued during the following decades. Linde developed water-cooled torches that helped prevent overheating when welding with high currents. During

10773-413: The electrode, the arc, or the welding metal. The gas also transfers heat from the tungsten electrode to the metal, and it helps start and maintain a stable arc. The selection of a shielding gas depends on several factors, including the type of material being welded, joint design, and desired final weld appearance. Argon is the most commonly used shielding gas for GTAW, since it helps prevent defects due to

10906-519: The electrode-negative portion of the cycle. Some power supplies enable operators to use an unbalanced alternating current wave by modifying the exact percentage of time that the current spends in each state of polarity, giving them more control over the amount of heat and cleaning action supplied by the power source. In addition, operators must be wary of rectification , in which the arc fails to reignite as it passes from straight polarity (negative electrode) to reverse polarity (positive electrode). To remedy

11039-501: 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. Stick electrodes for such materials, with special low-hydrogen coating, are delivered in sealed moisture-proof packaging. 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 450 to 550 °C or 840 to 1,020 °F) in

11172-575: The fabrication of steel structures and vehicles. 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. 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

11305-427: 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. Duty cycle is a welding equipment specification which defines the number of minutes, within a 10-minute period, during which

11438-472: The filler metal in the form of a rod is added to the weld pool manually, but some applications call for an automatically fed filler metal, which often is stored on spools or coils. As with other welding processes such as gas metal arc welding, shielding gases are necessary in GTAW to protect the welding area from atmospheric gases such as nitrogen and oxygen , which can cause fusion defects, porosity, and weld metal embrittlement if they come in contact with

11571-417: The form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat, flames, and sparks. The use of compressed gases and flames in many welding processes also 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. Exposure to the brightness of the weld area leads to

11704-440: The head angle, can be varied on some manual torches according to the preference of the operator. Air cooling systems are most often used for low-current operations (up to about 200  A ), while water cooling is required for high-current welding (up to about 600 A). The torches are connected with cables to the power supply and with hoses to the shielding gas source and where used, the water supply. The internal metal parts of

11837-460: The healthcare industry such as oxygen therapy , aerosol therapy, anaesthesia , and gas for chronic obstructive pulmonary disease , asthma , sleep apnoea and pain. Linde Engineering designs and builds large-scale chemical plants for the production of industrial gases including oxygen , nitrogen , argon , hydrogen and carbon monoxide , as well as large plants associated with the processing of natural gas, LNG , Liquefied petroleum gas and

11970-495: The high temperatures of this electric arc, the main heat transfer mechanism in GTAW is the joule heating resulting from this current flow. Welders wear protective clothing , including light and thin leather gloves and protective long sleeve shirts with high collars, to avoid exposure to strong ultraviolet light . Due to the absence of smoke in GTAW, the electric arc light is not covered by fumes and particulate matter as in stick welding or shielded metal arc welding , and thus

12103-775: The industrial gas business of BOC Gazy to Air Products & Chemicals for €370 million or about $ 503 million. In 2008, the head office of Linde AG was relocated from its historic headquarters in Wiesbaden to the Angerhof building in downtown Munich. In 2010, the company acquired over 95% of the shares of Sri Lanka –based Ceylon Oxygen Ltd. In June 2011, PT Linde Indonesia , a subsidiary of Linde, announced its plan to build an air separation plant worth Rp.1 trillion ($ 117.33 million) in Cilegon , Banten to supply industrial gas to PT Krakatau Steel 's steel plant. In May 2012,

12236-480: The joint must have an accurate fit, with proper gap dimensions and bevel angles. Care should be taken to avoid melting excessive base material. Pulsed current is particularly useful for these applications, as it helps limit the heat input. The filler metal should be added quickly, and a large weld pool should be avoided to prevent dilution of the base materials. In the pulsed-current mode, the welding current rapidly alternates between two levels. The higher current state

12369-470: 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. During World War I , welding started to be used in shipbuilding in Great Britain in place of riveted steel plates. The Americans also became more accepting of the new technology when

12502-407: The lungs, which can lead to early death. Similarly, the heat from the arc can cause poisonous fumes to form from cleaning and degreasing materials. Cleaning operations using these agents should not be performed near the site of welding, and proper ventilation is necessary to protect the welder. While the aerospace industry is one of the primary users of gas tungsten arc welding, the process is used in

12635-575: The machine from exposing operators to high voltage. The return clamp of the welding machine is located near to the work area, to reduce the risk of stray current traveling a long way to create heating hazards or electric shock exposure, or to cause damage to sensitive electronic devices. Welding operators are careful to install return clamps so that welding current cannot pass through the bearings of electric motors, conveyor rollers, or other rotating components, which would cause damage to bearings. Welding on electrical buswork connected to transformers presents

12768-527: The manufacture of olefins . The Engineering Division develops process plants in the engineering, procurement and construction (EPC) business worldwide. The group has more than 1,000 process engineering patents and 4,000 completed plant projects. The product range includes: On 21 June 1879, Carl von Linde founded the Gesellschaft für Linde's Eismaschinen Aktiengesellschaft to develop further his work in developing mechanical refrigeration systems for

12901-529: The medical gas area, the company uses the brand names Linde Gas Therapeutics, AGA Medical, INO Therapeutics, Linde Homecare, and Farmadomo. Linde Gas supplies industrial gases, medical gases, specialty gases, refrigerants and other chemicals. Depending on the gas and the quantity required, these may be supplied in portable high-pressure gas cylinders, in liquefied form by road tanker, from on-site gas generators or in gaseous form via pipeline to large customers. This division has four operating segments, Western Europe,

13034-402: The metal components, providing insulation from heat and electricity to protect the welder. The size of the welding torch nozzle depends on the amount of shielded area desired. The size of the gas nozzle depends upon the diameter of the electrode, the joint configuration, and the availability of access to the joint by the welder. The inside diameter of the nozzle is preferably at least three times

13167-546: The middle of the century, many new welding methods were invented. Submerged arc welding was invented in 1930 and continues to be popular today. In 1932, a Russian, Konstantin Khrenov successfully implemented the first underwater electric arc welding . 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. Using

13300-479: The more complicated equipment reduces convenience and versatility in comparison to the SMAW process. Originally developed for welding aluminum and other non-ferrous materials in the 1940s, GMAW was soon economically applied to steels . Today, GMAW is commonly used in industries such as the automobile industry for its quality, versatility and speed. Because of the need to maintain a stable shroud of shielding gas around

13433-484: The most prevalent use of TAG welding is in the production of higher end aluminium alloy bicycles, these welds are clearly visible as ripples in the welded joint. Other than mostly bicycle production TAG has been surpassed by the use of tungsten alloy tips and argon gas combined with other inert gasses. TAG welding rods are now highly specific project metal alloy rods or more frequently mass production flexible "flux" cable/wire fed drum machines. These developments have rendered

13566-436: The nozzle for special applications, such as gas lenses or valves to improve the control shielding gas flow to reduce turbulence and the introduction of contaminated atmosphere into the shielded area. Hand switches to control welding current can be added to the manual GTAW torches. Gas tungsten arc welding uses a constant current power source, meaning that the current (and thus the heat flux ) remains relatively constant, even if

13699-427: The operator accidentally allows it to contact the molten metal, it can become dirty or contaminated. This often causes the welding arc to become unstable, requiring that the electrode be ground with a diamond abrasive to remove the impurity. The equipment required for the gas tungsten arc welding operation includes a welding torch utilizing a non-consumable tungsten electrode, a constant-current welding power supply, and

13832-415: The problem, a square wave power supply can be used, as can high-frequency to encourage arc stability. The electrode used in GTAW is made of tungsten or a tungsten alloy, because tungsten has the highest melting temperature among pure metals, at 3,422 °C (6,192 °F). As a result, the electrode is not consumed during welding, though some erosion (called burn-off) can occur. Electrodes can have either

13965-587: The process allowed them to repair their ships quickly after a German attack in the New York Harbor at the beginning of the war. Arc welding was first applied to aircraft during the war as well, and some German airplane fuselages were constructed using this process. In 1919, the British shipbuilder Cammell Laird started construction of a merchant ship, the Fullagar , with an entirely welded hull; she

14098-490: The process is commonly used to repair tools and dies, especially components made of aluminum and magnesium. Because the weld metal is not transferred directly across the electric arc like most open arc welding processes, a vast assortment of welding filler metal is available to the welding engineer. In fact, no other welding process permits the welding of so many alloys in so many product configurations. Filler metal alloys, such as elemental aluminum and chromium, can be lost through

14231-437: The process is generally limited to welding ferrous materials, though specialty electrodes have made possible the welding of cast iron , nickel , aluminum , copper and other metals. The versatility of the method makes it popular in a number of applications including repair work and construction. Gas metal arc welding (GMAW), commonly called MIG (for metal/inert-gas ), is a semi-automatic or automatic welding process with

14364-408: The shielding gas and allows the arc to be initiated while the electrode and the workpiece are separated, typically about 1.5–3 mm (0.06–0.12 in) apart. Once the arc is struck, the welder moves the torch in a small circle to create a welding pool, the size of which depends on the size of the electrode and the amount of current. While maintaining a constant separation between the electrode and

14497-399: The shielding gas and increasing the temperature of the base material. The ionized shielding gas flows toward the electrode, not the base material, and this can allow oxides to build on the surface of the weld. Direct current with a positively charged electrode (DCEP) is less common, and is used primarily for shallow welds since less heat is generated in the base material. Instead of flowing from

14630-484: The short pulsed electric arcs. Independently, a Russian physicist named Vasily Petrov discovered the continuous electric arc in 1802 and subsequently proposed its possible practical applications, including welding. Arc welding was first developed when Nikolai Benardos presented arc welding of metals using a carbon electrode at the International Exposition of Electricity, Paris in 1881, which

14763-421: The solutions that developed included the use of hydrogen , argon , and helium as welding atmospheres. During the following decade, further advances allowed for the welding of reactive metals such as aluminum and magnesium . 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 . During

14896-435: 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 1,000 °C (1,830 °F), when the chromium carbide dissolves and niobium carbide forms. The cooling rate after this treatment

15029-704: 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. A variation of the process is plasma cutting , an efficient steel cutting process. Other arc welding processes include atomic hydrogen welding , carbon arc welding , electroslag welding , electrogas welding , and stud arc welding . Some materials, notably high-strength steels, aluminum, and titanium alloys, are susceptible to hydrogen embrittlement . If

15162-464: The tungsten electrode, making it unsuitable for the TIG process. In 1953, a new process based on GTAW was developed, called plasma arc welding. It affords greater control and improves weld quality by using a nozzle to focus the electric arc, but is largely limited to automated systems, whereas GTAW remains primarily a manual, hand-held method. Development within the GTAW process has continued as well, and today

15295-408: The two direct currents by making the electrode and base material alternate between positive and negative charge. This causes the electron flow to switch directions constantly, preventing the tungsten electrode from overheating while maintaining the heat in the base material. Surface oxides are still removed during the electrode-positive portion of the cycle and the base metal is heated more deeply during

15428-404: The type of metal being welded. Direct current with a negatively charged electrode (DCEN) is often employed when welding steels , nickel , titanium , and other metals. It can also be used in automatic GTAW of aluminum or magnesium when helium is used as a shielding gas. The negatively charged electrode generates heat by emitting electrons, which travel across the arc, causing thermal ionization of

15561-419: The weld area from atmospheric contamination. 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. Furthermore,

15694-434: The weld area than other welding processes, can produce high-quality welds when performed by skilled operators. Maximum weld quality is assured by maintaining cleanliness—all equipment and materials used must be free from oil, moisture, dirt and other impurities, as these cause weld porosity and consequently a decrease in weld strength and quality. To remove oil and grease, alcohol or similar commercial solvents may be used, while

15827-406: The weld bead to lift away from the surface being welded. If there is too much heat input, however, the weld bead grows in width while the likelihood of excessive penetration and spatter (emission of small, unwanted droplets of molten metal) increases. Additionally, if the welding torch is too far from the workpiece the shielding gas becomes ineffective, causing porosity within the weld. This results in

15960-420: The weld nears completion, the arc current is often gradually reduced to allow the weld crater to solidify and prevent the formation of crater cracks at the end of the weld. The physics of GTAW involves several complex processes, including thermodynamics, plasma physics, and fluid dynamics. The non-consumable tungsten electrode can be operated as a Cathode or Anode and is used to produce an electric arc between

16093-404: The weld pool, and can increase weld penetration, welding speed, and quality. A similar method, manual programmed GTAW, allows the operator to program a specific rate and magnitude of current variations, making it useful for specialized applications. The dabber variation is used to precisely place weld metal on thin edges. The automatic process replicates the motions of manual welding by feeding

16226-476: The weld site, it can be problematic to use the GMAW process in areas of high air movement such as outdoors. Flux-cored arc welding (FCAW) is a variation of the GMAW technique. FCAW wire is actually a fine metal tube filled with powdered flux materials. An externally supplied shielding gas is sometimes used, but often the flux itself is relied upon to generate the necessary protection from the atmosphere. The process

16359-428: The weld. Blunt electrode tips are preferred, and pure argon shielding gas should be employed for thin workpieces. Introducing helium allows for greater penetration in thicker workpieces, but can make arc starting difficult. Direct current of either polarity, positive or negative, can be used to weld aluminum and magnesium as well. Direct current with a negatively charged electrode (DCEN) allows for high penetration. Argon

16492-425: 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. Welders are also 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

16625-497: The work, while consumable or non-consumable electrodes are used. The welding area is usually protected by some type of shielding gas (e.g. an inert gas), vapor, or slag. Arc welding processes may be manual, semi-automatic, or fully automated. First developed in the late part of the 19th century, arc welding became commercially important in shipbuilding during the Second World War. Today it remains an important process for

16758-402: The workpiece, the operator then moves the torch back slightly and tilts it backward about 10–15 degrees from vertical. Filler metal is added manually to the front end of the weld pool as it is needed. Welders often develop a technique of rapidly alternating between moving the torch forward (to advance the weld pool) and adding filler metal. The filler rod is withdrawn from the weld pool each time

16891-568: Was developing an experimental aircraft from magnesium designated XP-56 , for which Vladimir Pavlecka , Tom Piper and Russell Meredith developed a welding process named Heliarc because it used a tungsten electrode arc and helium as a shielding gas (the torch design was patented by Meredith in 1941). It is now often referred to as tungsten inert gas welding (TIG), especially in Europe, but the American Welding Society's official term

17024-766: Was followed by its cousin, electrogas welding , in 1961. Linde Air Products Linde plc is a global multinational chemical company founded in Germany and, since 2018, domiciled in Ireland and headquartered in the United Kingdom. Linde is the world's largest industrial gas company by market share and revenue. It serves customers in the healthcare, petroleum refining, manufacturing, food, beverage carbonation, fiber-optics, steel making, aerospace, material handling equipment (MHE), chemicals, electronics and water treatment industries. The company's primary business

17157-649: Was incorporated in Ireland , with principal executive offices in Woking , UK . The company is a member of the Hydrogen Council , a group of companies investing in hydrogen vehicles . The company expects hydrogen vehicles to compete with electric vehicles and has invested in wind powered plants that convert water to hydrogen. The company is ranked 463rd on the Fortune Global 500 and 187th on

17290-404: Was launched in 1921. 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. Porosity and brittleness were the primary problems and

17423-562: Was patented together with Stanisław Olszewski in 1887. In the same year, French electrical inventor Auguste de Méritens also invented a carbon arc welding method, patented in 1881, which was successfully used for welding lead in the manufacture of lead–acid batteries . The advances in arc welding continued with the invention of metal electrodes in the late 19th century by a Russian, Nikolai Slavyanov (1888), and an American, C. L. Coffin . Around 1900, A. P. Strohmenger released in Britain

17556-578: Was rebranded as KION Group and sold to KKR and Goldman Sachs for €4bn in January 2007. In March 2007, the BOC Edwards semiconductor equipment business was sold to private equity firm CCMP Capital for €685m. Also in March 2007, eight air separation units and related bulk gas business, with about 300 employees, were sold to Airgas for $ 495 million in cash. In April 2007, the company sold

17689-458: Was the name given in the early 1970's to the then novel and revolutionary method of rod welding previously problematic metals. TAG welding was then the use of a tungsten tipped arc creating welding machine. The tip was centred in shroud that fed argon gas around tungsten tip to prevent the composition of the weld becoming oxidised and fragile. TAG welding used rods of a metal suitable for the material to be welded permanently together. The rods could be

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