Atomic hydrogen welding (
AHW) is an
arc welding process that uses an arc between two metal
tungsten electrodes in a shielding atmosphere of
hydrogen. The process was invented by
Irving Langmuir in the course of his studies of atomic hydrogen. 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 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.