Well I once saw a video in which a guy made a spot welder using a step down transformer and in another video I saw someone make arcer using a step up transformer. Why using a step up to jump arcs and step down to cause heat in transmission metal
It is all about electrical power and energy. An arc need a higher voltage so that the jolt of electricity can jump over(or through) air. This is why more voltage is needed than current. And a heater needs more current than voltage. When current goes through a wire it can produce heat. The heat power is p=I^2.R More the current is there, more the conductor is hot. That is why a step down transformer is used for situations like this to increase the current.