Voltage, amperage, wire and gas by thickness
Mild steel is the most forgiving metal to MIG weld, but getting the voltage and wire speed wrong is still the most common reason for a bad-looking bead. The right settings depend mainly on thickness — thin sheet needs less heat than it seems, and anything over 6mm needs more passes or amperage than most beginners expect.
| Thickness | Wire | Voltage | Amperage | Gas |
|---|---|---|---|---|
| Up to 1.6mm (16ga) | 0.6mm ER70S-6 | 16-18V | 90-120A | C25 (75/25 Ar/CO2) |
| 1.6-3mm | 0.8mm ER70S-6 | 18-20V | 120-150A | C25 (75/25 Ar/CO2) |
| 3-6mm | 0.8-0.9mm ER70S-6 | 20-24V | 150-200A | C25 (75/25 Ar/CO2) |
| 6mm+ | 0.9-1.2mm ER70S-6 | 24-28V | 200-260A | C25 (75/25 Ar/CO2) |
These are starting points, not fixed rules — every machine calibrates slightly differently, and joint type (butt vs. fillet) shifts things too. Always run a test bead on scrap of the same thickness before starting the actual job.
Want these settings for your exact thickness, plus TIG, Stick and plasma cutting settings in one place?
Use the parameter calculator →Voltage or wire speed is too low for the thickness. Bump voltage up one increment and increase wire speed slightly, then retest on scrap.
Too much heat for the thickness — drop voltage, increase travel speed, or switch to a smaller wire diameter. On sheet under 1.6mm, a slightly cooler setting than the chart's low end is often safer.
Usually voltage set too high relative to wire speed, or poor gas coverage from wind or a low flow rate. Check for drafts and confirm your flow meter reads 15-20 CFH.
Almost always a gas shielding issue — wind, low flow, a leaking hose, or standing too far from the joint. Keep stick-out to around 6-10mm and shield the weld area from drafts.
See the full calculator for TIG, Stick and plasma settings on mild steel, stainless and aluminium, or check the TIG aluminium settings guide if you're switching metals.