Question

Two non-consumable tungsten electrodes are used in process.

• A. Atomic hydrogen welding
• B. Plasma arc welding
• C. Submerged arc welding
• D. Tungsten inert gas welding

Hint:

Remember: Atomic Hydrogen Welding uses A pair of electrodes. This is a unique setup compared to almost all other common arc welding methods which use a single electrode.

Answer 1

The Correct Option is A

Atomic Hydrogen Welding (AHW) is a specialized arc welding process that utilizes two non-consumable tungsten electrodes to maintain an electric arc. Unlike standard TIG welding, the arc is maintained between the two electrodes rather than between an electrode and the workpiece. 1. The Mechanism of AHW:

• Electrode Configuration: Two tungsten electrodes are slanted toward each other. An AC arc is struck and maintained in the gap between their tips.

• Hydrogen Interaction: A stream of hydrogen gas is passed through the arc. The intense heat of the arc (exceeding 6000 K) causes the molecular hydrogen ($H_2$) to dissociate into atomic hydrogen ($H$).

• Exothermic Recombination: As the atomic hydrogen leaves the arc and touches the relatively cooler workpiece, it recombines back into molecular hydrogen. This recombination is a highly exothermic reaction, releasing a massive amount of heat concentrated on the weld area.

2. Comparing Other Processes:

• TIG (Tungsten Inert Gas) Welding: Uses only

one non-consumable tungsten electrode. The arc is formed between that single electrode and the base metal.

• Plasma Arc Welding: Similar to TIG, it primarily uses a single tungsten electrode located within a torch nozzle to create a constricted arc.

• Submerged Arc Welding: Typically uses a

consumable wire electrode that is buried under a layer of granular flux.

3. Conclusion: Because Atomic Hydrogen Welding is specifically designed to use an arc between two separate electrodes to dissociate gas, it is the only process among the options that requires two tungsten electrodes.