I learned some welding 20 years ago at school (not certified), but after watching probably most of the welding channels on youtube and collecting some problems at hand that can be done by welding, a couple of weeks ago i bought a relatively modern 200A AC/DC pulsed TIG/MMA/Plasma machine with a 5 year warranty on the machine itself and a pedal. Chinese manufacturer, german brand distributor. Also bought the safety gear (jacket, gloves, auto darkening helmet, welding blanket) and exchanged the gas cooled torch against a flexible one (several types are compatible), plus a gas lens kit. Some quick connectors for the gas were useful, as the machine only has one inlet for pressurized air and argon. Price range for all of it roundabout 1400 Euro.
I already finished a few little things here and there, the learning curve is quite steep and it was fun to learn. For aluminum the pedal was really important to adjust the current while you go and not screw stuff up, blow holes into the material and control the puddle, the hotter the parts get the less current is needed to melt - or just pre-heat.
If you want to cut and weld containers we are talking about steel sheet metal and a bit square tubing, maybe working on a ladder on some distance away from the power. I don´t get why you would want TIG, as your job sounds right for MMA or MIG anyway - with MIG you could use shielded flux wire and therefore work without gas, as you do with stick. You can even work one-handed, which in this case is a huge advantage over TIG. Most TIG machines do come with MMA, but a MMA/Plasma combo is probably cheaper. If you already know the maximum thickness to weld, you might even get away with a lower amperage requirement (160A for up to 4mm?!).
I don´t know how you want to weld these together, but when running beads on sheet metal always take the shrinkage into account, otherwise it might deform drastically or simply crack. The grinder will still be your best friend, as you need to bevel thicker materials to really have penetration down to the root of a joint.
My advice for buying a machine:
- if you never want to weld aluminum, you can skip machines with AC completely, it will drop the price significantly
- check the inrush current to match your power supply (in my case i got a single phase 230V, slow 16A B-characteristic breaker, that works fine even under full load), the cheaper models have the tendency to pop the breaker, maybe you could use an inrush current limiter or have access to good three phase power
- check which duty cycle you get, a 20% rating means out of 10 minutes, you can operate it 2 minutes and need 8 minutes cooldown, the higher the better, may also mean it is more reliable in the lower ranges
- check for DINSE connectors (cylindrical with a notch) on the machine, or at least one that is useful, so you can replace the cable package with a longer one
- check minimum current setting as mentioned by BradC, should you want to work with finer gage sheet metal (rule of thumb for steel: 40A/1 mm for welding)
- for TIG you might want the amperage control next to the place you weld, so for working on a ladder you should consider a torch with control included in the torch
- a pulse machine helps controlling how much heat goes into the part, but the helmet should be able to work with it (helmet delay > maximum pulse off duration ... so you don´t flash yourself at the restart)
- the TIG torches are mostly compatible to the consumables you can find on ebay (for compatibility watch this:
www.youtube.com/watch?v=3KroGM5e1dE)
- the plasma torches that come with it use pretty much standard consumables
- pressurized air supply should be sufficient (in my case 4.5 bar, 80 litres/minute)
- a 50A plasma cutter is rated for 12mm thick construction steel
for the actual job i´d say:
- practice various positions you will need to do (e.g. vertical up welding) with test pieces to find settings that work for you as much as you can before you start
- practice open root welding
- practice, practice, practice
- stay away from critical, potentially dangerous stuff, anything that people walk on or under
Really good channels for welding are ChuckE2009, weldingtipsandtricks, weld.com, the Fabrication series, This Old Tony and all i forgot. They all cover some aspects, but of course do not replace practice.
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