Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the United States) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline) and oxygen to weld or cut metals. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903.[1] Pure oxygen, instead of air, is used to increase the flame temperature to allow localized melting of the workpiece material (e.g. steel) in a room environment. A common propane/air flame burns at about 2,250 K (1,980 °C; 3,590 °F),[2] a propane/oxygen flame burns at about 2,526 K (2,253 °C; 4,087 °F),[3]an oxyhydrogen flame burns at 3,073 K (2,800 °C; 5,072 °F) and an acetylene/oxygen flame burns at about 3,773 K (3,500 °C; 6,332 °F).[4]
During the early 20th century, before the development and availability of coated arc welding electrodes in the late 1920s that were capable of making sound welds in steel, oxy-acetylene welding was the only process capable of making welds of exceptionally high quality in virtually all metals in commercial use at the time. These included not only carbon steel but also alloy steels, cast iron, aluminium, and magnesium. In recent decades it has been superseded in almost all industrial uses by various arc welding methods offering greater speed and, in the case of gas tungsten arc welding, the capability of welding very reactive metals such as titanium. Oxy-acetylene welding is still used for metal-based artwork and in smaller home-based shops, as well as situations where accessing electricity (e.g., via an extension cord or portable generator) would present difficulties. The oxy-acetylene (and other oxy-fuel gas mixtures) welding torch remains a mainstay heat source for manual brazing and braze welding, as well as metal forming, preparation, and localized heat treating. In addition, oxy-fuel cutting is still widely used, both in heavy industry and light industrial and repair operations.
In oxy-fuel welding, a welding torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal. The molten pool is generally supplied with additional metal called filler. Filler material selection depends upon the metals to be welded.
In oxy-fuel cutting, a torch is used to heat metal to its kindling temperature. A stream of oxygen is then trained on the metal, burning it into a metal oxide that flows out of the kerf as dross.[5]
Torches that do not mix fuel with oxygen (combining, instead, atmospheric air) are not considered oxy-fuel torches and can typically be identified by a single tank (oxy-fuel cutting requires two isolated supplies, fuel and oxygen). Most metals cannot be melted with a single-tank torch. Consequently, single-tank torches are typically suitable for soldering and brazing but not for welding.
https://en.wikipedia.org/wiki/Oxy-fuel_welding_and_cutting
https://en.wikipedia.org/wiki/Gas_tungsten_arc_welding
https://en.wikipedia.org/wiki/Titanium
https://en.wikipedia.org/wiki/Acetylene
https://en.wikipedia.org/wiki/Oxyhydrogen
https://en.wikipedia.org/wiki/Dross
https://en.wiktionary.org/wiki/kerf
https://en.wikipedia.org/wiki/Autoignition_temperature
https://en.wikipedia.org/wiki/1,2-Epoxybutane
https://en.wikipedia.org/wiki/Butene
https://en.wikipedia.org/wiki/Fluid_catalytic_cracking
https://en.wikipedia.org/wiki/Fractional_distillation
https://en.wikipedia.org/wiki/-yne
https://en.wikipedia.org/wiki/3-Hexyne
https://en.wikipedia.org/wiki/Octyne
https://en.wikipedia.org/wiki/Hydroxy_group
https://en.wikipedia.org/wiki/Radical_(chemistry)
https://en.wikipedia.org/wiki/Triplet_oxygen
In 1785, the Dutch chemist Martinus van Marum was conducting experiments involving electrical sparking above water when he noticed an unusual smell, which he attributed to the electrical reactions, failing to realize that he had in fact created ozone.[6]
A half century later, Christian Friedrich Schönbein noticed the same pungent odour and recognized it as the smell often following a bolt of lightning. In 1839, he succeeded in isolating the gaseous chemical and named it "ozone", from the Greek word ozein (ὄζειν) meaning "to smell".[7][8] For this reason, Schönbein is generally credited with the discovery of ozone.[9][10][11][6] The formula for ozone, O3, was not determined until 1865 by Jacques-Louis Soret[12] and confirmed by Schönbein in 1867.[7][13]
For much of the second half of the nineteenth century and well into the twentieth, ozone was considered a healthy component of the environment by naturalists and health-seekers. Beaumont, California had as its official slogan "Beaumont: Zone of Ozone", as evidenced on postcards and Chamber of Commerce letterhead.[14] Naturalists working outdoors often considered the higher elevations beneficial because of their ozone content. "There is quite a different atmosphere [at higher elevation] with enough ozone to sustain the necessary energy [to work]", wrote naturalist Henry Henshaw, working in Hawaii.[15] Seaside air was considered to be healthy because of its believed ozone content; but the smell giving rise to this belief is in fact that of halogenated seaweed metabolites.[16]
Much of ozone's appeal seems to have resulted from its "fresh" smell, which evoked associations with purifying properties. Scientists, however, noted its harmful effects. In 1873 James Dewar and John Gray McKendrick documented that frogs grew sluggish, birds gasped for breath, and rabbits' blood showed decreased levels of oxygen after exposure to "ozonized air", which "exercised a destructive action".[17][9] Schönbein himself reported that chest pains, irritation of the mucous membranes and difficulty breathing occurred as a result of inhaling ozone, and small mammals died.[18] In 1911, Leonard Hill and Martin Flack stated in the Proceedings of the Royal Society B that ozone's healthful effects "have, by mere iteration, become part and parcel of common belief; and yet exact physiological evidence in favour of its good effects has been hitherto almost entirely wanting ... The only thoroughly well-ascertained knowledge concerning the physiological effect of ozone, so far attained, is that it causes irritation and œdema of the lungs, and death if inhaled in relatively strong concentration for any time."[9][19]
During World War I, ozone was tested at Queen Alexandra Military Hospital in London as a possible disinfectant for wounds. The gas was applied directly to wounds for as long as 15 minutes. This resulted in damage to both bacterial cells and human tissue. Other sanitizing techniques, such as irrigation with antiseptics, were found preferable.[9][20]
Until the 1920s, it was still not certain whether small amounts of oxozone, O
4, were also present in ozone samples due to the difficulty of applying analytical chemistry techniques to the explosive concentrated chemical.[21][22] In 1923, Georg-Maria Schwab (working for his doctoral thesis under Ernst Hermann Riesenfeld) was the first to successfully solidify ozone and perform accurate analysis which conclusively refuted the oxozone hypothesis.[21][22] Further hitherto unmeasured physical properties of pure concentrated ozone were determined by the Riesenfeld group in the 1920s.[21]
https://en.wikipedia.org/wiki/Ozone
https://en.wikipedia.org/wiki/Ozonolysis
https://en.wikipedia.org/wiki/Molecular_symmetry
https://en.wikipedia.org/wiki/Tetraoxygen
https://en.wikipedia.org/wiki/Solid_oxygen
https://en.wikipedia.org/wiki/Ozone_depletion
https://en.wikipedia.org/wiki/Halocarbon
https://en.wikipedia.org/wiki/Ozone_depletion
https://en.wikipedia.org/wiki/Refrigerant
https://en.wikipedia.org/wiki/Blowing_agent
https://en.wikipedia.org/wiki/Propellant
https://en.wikipedia.org/wiki/Solvent
https://en.wikipedia.org/wiki/Jet_stream
https://en.wikipedia.org/wiki/Thermal_wind
https://en.wikipedia.org/wiki/Haloalkane
https://en.wikipedia.org/wiki/Photodissociation
https://en.wikipedia.org/wiki/Solid_oxygen
https://en.wikipedia.org/wiki/Ozone–oxygen_cycle
https://en.wikipedia.org/wiki/Jet_stream
https://en.wikipedia.org/wiki/Astrophysical_jet
No comments:
Post a Comment