Atomic Hydrogen Welding (AHW)

Shows the AEI welding power source

My job often involves working on interesting and unusual welding related projects and can take me to many a far-flung corner of the world. One such welding project involved a welding process you may have never even heard of, and I will confess, up to a few years ago I was only aware of it in books. The process is called Atomic Hydrogen.

A client of mine for many years, part of the BDC Group, is involved with welding and repairing lifting chains and continues to use this welding process, even today, because it offers a perfect solution for his application. Although, I am aware that they are on their last machine, after robbing parts from all their other machines for some time now.

This is not just a nostalgic, historical look about a welding process that has all but passed us by, but more to show you a process that was common place in the 1930’s, and even today offers the best solution to a welding problem, in this case, welding of lifting chains.

It is true I wanted to provide some information, for those of you whom are interested, and shoot some video footage, as I am acutely aware that when their welder retires, this may be the end for this process, at least for me, and it is most unlikely I shall ever come across the use of Atomic Hydrogen welding in a commercial environment ever again.

The process was invented by Dr Irving Langmuir in 1926 and was used extensively before WW2, particularly in Germany.

AHW is an arc welding process that uses an arc between two tungsten electrodes in a shielding gas atmosphere of hydrogen. Filler may or may not be used. A jet of hydrogen is disassociated as it passes through an electric arc. H2 > H + H = 422kJ. The temperature of the arc is in excess of 3700 °C.

The arc is maintained entirely independently of the work. The work is part of the electrical circuit only to the extent that a portion of the arc comes into contact with the work, at which time, a voltage exists between the work and the electrodes. The hydrogen can be thought of as simply a transport mechanism to extract energy from the arc plasma and transferring it to the work. It produces a flame as heat is liberated by the chemical reaction. Iron can be melted without contamination with carbon, oxygen or nitrogen. Because of the powerful reducing action of the atomic hydrogen, alloys can be melted without fluxes and without surface oxidation.

A feature of the flame is the speed by which it can deliver heat to the workpiece. When an arc is established in hydrogen, between two electrodes, the molecular hydrogen dissociates into atomic hydrogen. In the process of disassociation, large amounts of heat is absorbed from the arc by the hydrogen. This heat is released on recombination of the hydrogen atoms at the work surface due to hydrogen atoms recombining in their molecule form.

The operator can control the heat by varying the distance of the arc stream between the two electrodes and the distance to the workpiece.

Shows macro of completed weld in a 12mm steel bar

The power source is a transformer that has an open circuit voltage (OCV) of up to 300 volts to strike the arc, but welding current is low, with generally amperages of 10-20 being used, although this particular AEI model offers a maximum of 50 amps.

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