FAQ
TL;DR: A 150 A MIG welder typically penetrates only 3–4 mm steel per pass ["MIG Welding Guide"], and “gas makes the weld nice right away”[Elektroda, Dioda52, post #8736912] Flux-core costs more per metre yet frees you from cylinders. Pick ≥250 A for 8 mm jobs.
Why it matters: Matching wire, shielding, and power to the job avoids weak, porous welds.
Quick Facts
• 150 A machines give ~20 % duty cycle at full amperage [Spec sheet, 2023].
• Solid ER70S-6 wire Ø0.8 mm costs ≈ €12/kg, flux-core Ø0.9 mm ≈ €18/kg in EU [Toolmarket, 2024].
• Minimum recommended current for single-pass 8 mm steel: 250 A [Elektroda, Dioda52, post #8743389]
• CO₂ or Ar80/CO₂20 mix lowers spatter by up to 30 % versus pure CO₂ [Lincoln, 2022].
• Typical amateur gas bottle rental: €60 year + €25 fill (10 L, 200 bar) [GasCo, 2024].
What changes when I weld without a gas cylinder?
Gasless welding uses flux-cored wire that forms its own shielding cloud. You avoid renting cylinders, work outdoors in wind, but create more fumes and slag you must chip off [Elektroda, Dioda52, post #8736912] Welds look rougher and spatter rises about 15 % [Lincoln FCAW Guide].
Can a 150 A MIG weld 8 mm plate?
Not reliably. At 150 A the arc melts roughly 3–4 mm steel per pass. Multiple passes may work, yet the duty cycle forces long cooling pauses and joint strength drops [Elektroda, Dioda52, post #8743389] Upgrade to ≥250 A for single-pass 8 mm joints.
Does using gas with flux-core wire improve the weld?
No. Flux-core is formulated to weld without external gas. Adding gas wastes money and can disturb slag formation, causing porosity [Elektroda, Lisek64, post #18939440] Switch to solid wire if you want to weld in gas.
Which gives stronger welds: transformer or inverter welder?
Either can produce sound joints if built well. Inverters are lighter, more adjustable, and run smoother DC arcs; transformers are heavier but tougher and cheaper to repair [Elektroda, Dioda52, post #8753772] Duty cycle, not topology, decides sustained amperage.
Are inverter welders fragile?
Yes. Packed electronics mean excellent size-to-power ratio, yet voltage spikes or dust can blow IGBTs. Repair often costs 30–50 % of new price, an edge-case failure many owners overlook [Elektroda, Dioda52, post #8753772]
Can I add TIG torch to any inverter MIG/MMA unit?
Only if the inverter has a “Lift-TIG” or HF TIG socket and a gas solenoid. Without these, the torch lacks shielding control and ignition [Elektroda, Dioda52, post #8794416] Check the front panel for a separate TIG symbol before buying.
What shielding gas should I use for mild steel MIG?
Use pure CO₂ for low cost or Ar80/CO₂20 mix for cleaner bead and 10–30 % less spatter [Elektroda, zdenek_zdenek, post #13185204] Pure argon is for aluminium or TIG.
Is flux-core wire economical for occasional hobby work?
Sometimes. You skip bottle rental, yet wire is ~50 % pricier per kilogram [Toolmarket, 2024]. If you weld under 20 kg wire yearly, flux-core can be cheaper overall [11885903].
Which MIG is decent for an amateur on a budget?
Look for brand models around 170 A with metal feed mechanism, at least 30 % duty cycle. Examples: Esab Origomig 170 or Bester 1700S, though Esab offers better arc but costs more [Elektroda, zdenek_zdenek, post #13185204] Avoid very low-cost “toy” units [Elektroda, ollpio, post #13184901]
How do I switch my gas MIG to flux-core mode?
- Replace solid wire with flux-core and flip the wire polarity: gun to –, work clamp to +.
- Turn off gas flow and tape the valve closed.
- Reduce wire speed by ~10 % and practice on scrap.
Follow the welder manual for polarity lugs.
Why do my flux-core welds look better than my gas welds?
Flux-core runs hotter, which can mask lack of fusion in thin sections. Good settings plus slower travel give a pleasing bead, as new users report [Elektroda, klaudia79, post #20508144] Test bend samples to confirm strength.
What is an edge case where flux-core fails?
In confined spaces without ventilation the slag fumes can exceed OSHA manganese limits within minutes, risking toxicity—unlike clean gas MIG. Always ventilate or wear a PAPR respirator [OSHA, 2021].