Atomic hydrogen welding (AHW) is an

arc welding Arc welding 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 powe ...

process that uses an arc between two

tungsten Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials d ...

s in a shielding atmosphere of

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

. The process was invented by Irving Langmuir in the course of his studies of

atomic hydrogen A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively charged proton and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constit ...

. The

electric arc An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such as air produces a plasma; the plasma may produce visible light. An ...

efficiently breaks up the hydrogen molecules, which later recombine with tremendous release of heat, reaching temperatures from 3400 to 4000 °C. Without the arc, an

oxyhydrogen Oxyhydrogen is a mixture of hydrogen (H2) and oxygen (O2) gases. This gaseous mixture is used for torches to process refractory materials and was the first gaseous mixture used for welding. Theoretically, a ratio of 2:1 hydrogen:oxygen is enough ...

torch can only reach 2800 °C. This is the third-hottest flame after

dicyanoacetylene Dicyanoacetylene, also called carbon subnitride or but-2-ynedinitrile (IUPAC), is a compound of carbon and nitrogen with chemical formula . It has a linear molecular structure, (often abbreviated as ), with alternating triple and single covalen ...

at 4987 °C and

cyanogen Cyanogen is the chemical compound with the formula ( C N)2. It is a colorless and highly toxic gas with a pungent odor. The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups – analogous to diatomic halogen molecu ...

at 4525 °C. An acetylene torch merely reaches 3300 °C. This device may be called an atomic hydrogen torch, nascent hydrogen torch or Langmuir torch. The process was also known as arc-atom welding. The heat produced by this torch is sufficient to weld

(3422 °C), the most

refractory metal Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The expression is mostly used in the context of materials science, metallurgy and engineering. The definition of which elements belong to this group diff ...

. The presence of hydrogen also acts as a

shielding gas 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 arc welding (GMAW and GTAW, more popularly known as MIG (Metal Inert Gas) and TIG (Tungsten Iner ...

, preventing oxidation and contamination by

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

, which can severely damage the properties of many metals. It eliminates the need of flux for this purpose. The arc is maintained independently of the workpiece or parts being welded. The hydrogen gas is normally diatomic (H₂), but where the temperatures are over near the arc, the hydrogen breaks down into its atomic form, absorbing a large amount of heat from the arc. When the hydrogen strikes a relatively cold surface (i.e. the weld zone), it recombines into its diatomic form, releasing the energy associated with the formation of that bond. The energy in AHW can be varied easily by changing the distance between the arc stream and the workpiece surface. In atomic hydrogen welding,

filler metal A filler metal is a metal added in the making of a joint through welding, brazing, or soldering. Soldering Soldering and brazing processes rely on a filler metal added to the joint to form the junction between the base metal parts. Soft solderin ...

may or may not be used. In this process, the arc is maintained entirely independent of the work or parts being welded. The work is a part of the electrical circuit only to the extent that a portion of the arc comes in contact with the work, at which time a voltage exists between the work and each electrode. This process is being replaced by gas metal-arc welding, mainly because of the availability of inexpensive inert gases.

Video documentation

The Inside of Atomic Hydrogen Arc Welding, Part 1 - 1943

The Inside of Atomic Hydrogen Arc Welding, Part 2 - 1943

References

* Norton science encyclopedia 1st and 6th edition copyright 1921–1950 and 1976 * Van Nostrand's Encyclopedia of Science (Pg. 1311) * Welding Handbook Vol. 2 Library of Congress number 90-085465 copyright 1991 by American Welding Society * Kalpkjian, Serope and Steven R. Schmid. ''Manufacturing Engineering and Technology'' textbook Fifth edition. Upper Saddle River: Pearson Education, Inc., 2006 * * * {{DEFAULTSORT:Atomic Hydrogen Welding Arc welding Hydrogen technologies

Video documentation

See also

References