My total guess is that to generate the arc, you need to ionize the electrons to make them flow free from the atom, and where that happens has the most heat?
I’m intrigued too.
It could be the Peltier Effect?
https://amadaweldtech.com/wp-conten...rity-on-the-Resistance-Welding-ProcessWeb.pdf
Part of my problem is that I do know a fair bit about spot welding. I even hold a few patents. Basically, I know enough to know how little I really know.
But Spot welding is totally a resistance welding process. Basically, you pump enough current through the two layers that the power generated by their internal resistance melts and fuses the two layers together. There is no arc or plasma involved.
I don't know enough about the other kinds of welding to have any slightest idea about how the process works much less how heat manages to flow with or against the flow of electrons. But I would like to.
I do know that those above who describe the current as one electron being added in at one end for every one that pops out the other end are mostly correct. They all sort of shuffle over so to speak like a big crowd of people moving through a wide corridor - some entering, and some leaving. Interestingly though, the ones at the outside on the surface of the conductor move faster than the ones inside - quite the opposite of the way liquids flow in pipes.
Pure theoretical physics folks prefer to describe the process in quantum probability terms. I like to read that stuff, but in my own mind I prefer the applied science (engineering) way of thinking. When I used to teach electrical I liked to use the water hose analogy. The wire is analogous to a hose, The flow of water in the hose is analogous to current, the pressure to voltage, a container to capacitance, the inertia and water hammer in a long pipe to inductance, a transistor to a tap, a valve to a switch, etc. For most students, that works well to open the door to understanding.
It's very hard for the majority of us to understand or even comprehend the physics because the relative distances are so huge. If the nucleus of a hydrogen atom was a ping-pong ball, it's electrons would be invisible points with mass and energy but no size a kilometer away. Attempting to imagine the flow of electrons in a conductor or an arc becomes somewhat challenging to say the least.
My library doesn't seem to have anything in it to explain the science of welding arcs so I have reached out to a few colleagues. TBD here.
