Submerged arc welding is an ordinary process that involves joining two metals using heat.
However, once you look at it closely, it looks extraordinary!
The process is carried out in the following steps:
An arc is formed between the electrode and the piece that you are working upon.
The arc is below the flux so it is not even visible via: Youtube
A thin layer of flux powder is maintained on the work piece.
An arc is welding between two metal pipes with flux powder via: Youtube
As the arc moves, the excess flux powder is displaced and recycled.
(the flux powder is basically a binding agent.)
The hopper, black in color, is picking up the excess flux powder via: Youtube