Helium is very common in the universe (according to current estimates of over 20% of the cosmic mass accounts for helium), but on Earth it is not enough. Helium is found in the air (about 0.0005%) and in the earth's crust, which is formed by the decay of radioactive elements.
Helium is produced by fractional condensation from natural gas produced in the decay of uranium-containing rocks.
Gaseous helium is not flammable, not toxic, not explosive. However, in the case of high concentration in the air can cause a state of oxygen deficiency and asthma. Liquid Helium - a colorless low-boiling liquids that can cause frostbite of the skin and mucous membrane of the eye lesion.
Safety precautions when handling the helium:
- premises for the storage or use of helium should be well ventilated;
- Helium balloons must not be subjected to excessive heat;
- balloons with helium valves must be opened slowly;
- when working with liquid helium is necessary to use protective equipment for the body, special gloves, goggles and protective footwear.
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Helium can be used as an inert shielding gas for welding stainless steels, nonferrous metals and alloys are chemically pure and active material. He has the ability to provide high penetration, and therefore it is sometimes used for the penetration of large thicknesses or obtain a special form of joint. However, due to increased consumption and the high cost of helium compared with argon, its scope is limited.
Helium is also used for laser welding in a mixture with other gases to create a working environment in gas lasers, as plazmopodavlyayuschego gas supplied to the area of laser welding with plasma welding is usually as a supplement to the plasma-forming gas - argon.
See also:
laser welding technology
plasma welding
Welding materials:
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