Jaja si, soy de Argentina. Vos de Guatemala? Eso dice el usuario :P
By "argon tube" i meant the high pressure vessel, the tank, which in our case works at 140 bar of pressure. Argon regulators often deliver 5 bar, and some can be setted to lower pressures. If you don´t have it, consider it can be expensive.
Adding a dimmer is something electrically "incorrect" but works; I´ve seen commercial welders with them. A dimmer for a welder should be designed for inductive loads. And yes, dimmers work better at the primary, because of the lower currents.
If you make or buy a dimmer, remember that their cases, heatsinks and even perhaps knobs can be connected directly or somehow to the mains (TRIAC and SCR heat dissipation tabs are often connected to a terminal), so electrocution risk is high.
*** BE VERY CAREFUL! *** , don't take risks and don't use it if you don't fully understand it. Ask the seller for the dimmer's instalation procedure or standar housing, also.
Here's a homemade design:
Homebuilt arc welder · Dan's Workshop Blog
Selecting voltage capability of a dimmer or its components is not so hard: If your mains is 220V, that is it's RMS value, kind of a power equivalent to DC voltage. If you want to select a SCR/TRIAC, it´s datasheet will probably specificate peak voltage; sine wave AC has a peak voltage of 1.41 ( = sqrt(2)) the mains RMS voltage: 220Vrms * 1.41 = 311Vpk, so any 400Vpk component should work okay.... at least from what i know.
The current capability of the dimmer needed to control a welder is a bit hard to estimate, at least for me. First of all, you should look at the plate of the welder and try to figure out peak primary current, "I1max" probably.
If that is impossible, you can measure the current with a clamp inductive amp meter, and try every possible use (vary power, weld with a long arc, a short arc, and stick the electrodes in short circuit). As a last resource, you can calculate power output of your welder, calculate amps needed at the primary, and apply a generous safety coefficient. Stick welders usually deliver around 20V at medium amperages, TIGs are around 14V @ 30A. Be warned that welder are highly inductive loads, so their power factor is poor and draw extra current that flows but -due to not being in phase with voltage- does not deliver active power; that means that a welder delivering 2200W@220V will need 10 amps of "active" current and some more (some times a lot more) of "reactive" current... if the welder data plate specificates power factor or Cos(phi), you can calculate the reactive current.
Safety considerations and design of the circuit can be found in many websites.. google it. Again, be careful -even if you just buy it- and don't use it until you fully understand it. Take into account the heat dissipation requirements of the dimmer, they dissipate about P = 1.5 Volts * I ... if i'm right.
If the result goes up many amps, it can be too expensive, so you might consider using a smaller but detachable dimmer, only when requiring low power, and protect it with a fuse or thermomagnetic switch (it might not be enough, but it's something). I´ve seen a commercial welder with a rather small triac.
bye!