Complete guide to MIG welding for sheet metal fabrication. Learn about wire selection, parameter optimization, and techniques for high-quality production welds.
Introduction
MIG (Metal Inert Gas) welding, also known as GMAW, is the most productive arc welding process for sheet metal fabrication. At Fulei Metal, our 10 welding stations include MIG capabilities for high-volume production serving automotive, machinery, and equipment manufacturers.
What is MIG Welding?
MIG welding uses a continuously fed consumable wire electrode. The arc melts the wire and base metal. Shielding gas protects the weld pool. This provides high deposition rates and fast travel speeds.
Advantages for Sheet Metal
High productivity with continuous wire feed. Easier to learn than TIG. Good for positional welding. Suitable for a wide range of thicknesses. Less distortion than stick welding. Can be automated.
Shielding Gas
Carbon Steel
CO2 or Argon-CO2 mixtures (75% Ar / 25% CO2 is common). CO2 provides deep penetration but more spatter. Argon-CO2 provides smoother arc and less spatter.
Stainless Steel
Argon with 2% oxygen or Argon-CO2 with low CO2 (2-5%). Tri-mix (Ar-He-CO2) for some applications.
Aluminum
Argon for thin materials. Argon-helium for thicker sections. Helium provides hotter arc.
Wire Selection
Carbon Steel
ER70S-6 is the standard choice. Available in diameters: 0.6, 0.8, 1.0, 1.2 mm. For sheet metal: 0.8 mm is most common.
Stainless Steel
ER308L for 304. ER316L for 316. ER309L for dissimilar welding. Diameter: 0.8-1.0 mm for sheet metal.
Aluminum
ER4043 (silicon-based) for general purpose. ER5356 (magnesium-based) for higher strength. Diameter: 0.8-1.0 mm for sheet metal.
Parameters for Sheet Metal
Carbon Steel (0.8 mm wire)
1 mm: 60-80 amps, 15-16V, short-circuit transfer. 2 mm: 100-130 amps, 17-19V. 3 mm: 130-160 amps, 19-21V.
Wire Feed Speed
Directly affects amperage. Faster feed = more amperage. For 0.8 mm wire: 3-8 meters per minute for sheet metal.
Gas Flow
10-15 liters per minute. Too low: porosity. Too high: turbulence, waste.
Transfer Modes
Short-Circuit Transfer
Low heat input. Wire dips into pool creating short circuits. Ideal for thin sheet metal (1-3 mm). Low spatter with proper settings.
Spray Transfer
High heat input. Fine droplets spray across arc. For thicker materials (4 mm+). Smooth, high-deposition welds.
Pulsed Spray
Alternates between high and low current. Combines benefits of spray with lower heat input. Excellent for thin to medium materials. Reduces spatter and distortion.
Technique
Torch Angle
10-15 degrees from vertical. Push technique (torch angled away from weld direction) for thinner materials. Drag technique for thicker materials.
Travel Speed
Match speed to wire feed and amperage. Watch the weld pool size. Consistent speed produces consistent welds.
Stick-Out
Wire extending from contact tip: 6-12 mm for sheet metal. Too long: unstable arc, poor gas coverage. Too short: burn-back to contact tip.
Common Applications
At Fulei Metal, we use MIG welding for: machinery frames, equipment enclosures, automotive brackets, structural assemblies, agricultural equipment, and high-volume production welds.
Common Problems
Porosity: check gas flow, clean material, verify gas type. Spatter: adjust voltage, check wire feed, consider pulsed MIG. Burn-through: reduce amperage, increase speed, use short-circuit transfer. Poor penetration: increase amperage, slow travel, adjust wire feed. Distortion: control heat input, use tack welds, sequence welds properly.
Conclusion
MIG welding offers high productivity for sheet metal fabrication. At Fulei Metal, our MIG capabilities and experienced welders ensure quality production welds for our international clients.
MIG Settings for Sheet Steel, by Thickness and Transfer Mode
MIG is the default process for sheet metal because it is fast and it tolerates the fit-up gaps that would stop an automated laser seam. The window below is for carbon steel with solid wire; the notes underneath cover the two materials that shift it most.
| Sheet thickness | Wire | Transfer mode | Current / voltage | Wire feed speed | Shielding gas | Travel speed |
|---|---|---|---|---|---|---|
| 0.8 mm | 0.8 mm ER70S-6 | Short-circuit or pulsed | 60-90 A / 16-18 V | 2.5-4.0 m/min | Ar + 8-12% CO2 | 40-70 cm/min |
| 1.5 mm | 0.8 mm | Short-circuit or pulsed | 90-140 A / 18-20 V | 4.0-6.0 m/min | Ar + 8-18% CO2 | 35-60 cm/min |
| 3.0 mm | 1.0 mm | Pulsed or spray | 150-200 A / 21-24 V | 6.0-9.0 m/min | Ar + 8-18% CO2 | 30-50 cm/min |
| 5.0 mm | 1.0-1.2 mm | Pulsed or spray | 190-260 A / 24-28 V | 8.0-12 m/min | Ar + 12-20% CO2 | 25-45 cm/min |
| 1.5 mm galvanised | 0.8 mm ER70S-6 or CuSi3 | Pulsed preferred | 10-15% above bare steel | same band | Ar + 8-12% CO2 | 35-60 cm/min |
Heat input is what ties those rows together, and it is worth calculating rather than guessing: H in kJ/mm = voltage x current x 60 / travel speed in mm/min, multiplied by roughly 0.8 for arc efficiency in GMAW. Two settings with identical heat input will not always produce an identical bead, but on thin sheet any change that raises H raises burn-through and distortion risk in step. On galvanised material the extra current compensates for heat lost vaporising zinc; the more important adjustment is a short stick-out and a gun angle that lets zinc vapour escape rather than trapping it as porosity.
Frequently Asked Questions
Why has my MIG weld started spattering more than it used to?
Most often the voltage is too high for the wire feed speed, which pushes the process into globular transfer. Dropping voltage by 1-2 V, or raising wire feed slightly, brings it back to short-circuit. If the setting is right, check stick-out: beyond about 15 mm the wire preheats and the arc becomes unstable regardless of the numbers on the machine.
Can MIG be used on 0.8 mm sheet without burning through?
Yes, but pulsed transfer makes it far easier than short-circuit. Pulse lets the puddle freeze between current peaks, so average heat input stays low while penetration is still achieved. Add a copper backing bar on long seams and keep the travel speed up.
What causes porosity when welding galvanised sheet?
Zinc vapour trapped in the solidifying weld. The practical controls are to remove the coating from the joint faces by grinding where the specification allows it, keep the arc short, raise travel speed slightly, and make sure fume extraction pulls vapour away without blowing across the arc shield.
Questions about a specific part are usually faster to answer against the drawing — send it through the route below.
Before you send the RFQ. Reference welding inspection methods first if this part is still at drawing stage — most cost drivers are decided there. For anything already specified, sheet metal welding service is where to send it. Related: send the drawing for review and welding process comparison.