Atomic hydrogen welding (AHW) is an
arc welding process that uses an arc between two
tungsten electrodes in a shielding atmosphere of
hydrogen. The process was invented by
Irving Langmuir
Irving Langmuir (; January 31, 1881 – August 16, 1957) was an American chemist, physicist, and engineer. He was awarded the Nobel Prize in Chemistry in 1932 for his work in surface chemistry.
Langmuir's most famous publication is the 1919 art ...
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 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 torch can only reach 2800 °C.
This is the third-hottest flame after
dicyanoacetylene at 4987 °C and
cyanogen at 4525 °C. An
acetylene
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
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
tungsten (3422 °C), the most
refractory metal. 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,
nitrogen or
oxygen, which can severely damage the properties of many metals. It eliminates the need of
flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
for this purpose.
The arc is maintained independently of the workpiece or parts being welded. The hydrogen gas is normally diatomic (H
2), 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 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 - 1943The Inside of Atomic Hydrogen Arc Welding, Part 2 - 1943
See also
*
Oxy-fuel welding and cutting#Hydrogen
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
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{{DEFAULTSORT:Atomic Hydrogen Welding
Arc welding
Hydrogen technologies