OMG! That's one of the dangers of this art and craft.
I severally heard of fatal accidents where a tradesman is welding an empty petroleum tank without first evacuating (don't know the technical term for it) the remnant gaseous amount.
Cheapest and relatively easiest to learn is arc welding, other names: MMA, SMAW, stick welding. The welding set up is more economically affordable than others. You need either transformer or inverter welding machine.
MIG (GMAW), TIG (GTAW), SMAW (MMA), FCAW are electric arc welding...
What I know is that is a 1st order ODE can be solved by 'Seperating the Variables' method. So, #ydy=x^2dx# just take the integral of both side.
Is that what you meant in the OP?