In this welding, arc is created between two non-consumable electrodes (as shown in Figure 20.40) by supplying AC current. When hydrogen gas is passed through the arc, the heat of arc is absorbed by hydrogen molecules and dissociate into hydrogen atoms. When hydrogen atoms reach at cold work surface recombines to form hydrogen molecules with releasing a large amount of heat. Thus, work surface melts by the heat of hydrogen atoms recombination. If filler material is required a filler rod is fed into the arc. The temperature is of the order of 3,000°C.
Figure 20.40 Atomic Hydrogen Welding
- It gives high heat concentration as hydrogen gas can be passed through narrow slit.
- There is no need to provide additional shielding gas as hydrogen also shields the molten metal pool.
- It is used successfully for many alloys which are difficult to weld by other processes due to need of high heat generation.
Limitations
- It is outdated and rarely used in industry.
- There is hydrogen induced cracking problem.
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