NEW AEI WELDING POWER SOURCE
05 November 2006 - Speciality Welds

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 the torch and the position of the two tungsten’s. The power source is a transformer that has an open circuit voltage 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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Underwater Contractor International 23 Speciality Welds’ new system, which has been named Hammerhead in keeping with the company’s ‘fish’ brand, addresses problems in obtaining high quality wet welds in nil visibility, without the need for experienced (skilled) welder-divers.

By removing the individual welding skills from the operation, there’s no need for the
diver-welder to control parameters that affect quality, such as travel speed, electrode
angle, arc length and accurate deposition. Because the operator no longer needs to control these parameters, it is not essential to have good visibility.

So, even in nil visibility conditions high quality repeatable welds can be produced
time after time. How the system works In removing the skills necessary to carry out underwater wet welding, Speciality has modified the fundamental approach to how ‘stick’ welding is carried out. The company’s system allows the operator a far more simplified role.

How is all this achieved? In simple terms, by creating a spot/plug weld rather than
having to deposit a fillet weld within a specified joint. By removing the need for a
fillet weld deposit Speciality has also simplified the joint configuration (simple lap
joint) and all the preparation that goes with it, while also removing the need for extensive cleaning of the joint area and chipping off metres of slag prior to additional passes.

http://www.specialwelds.com/

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