This guide provides practical guidance for selecting MIG welding wire for mild steel.
Wire: ER70S-6
Diameter: 0.035" (general purpose)
Shielding Gas: 75% Argon / 25% CO₂ (C25)
Process: MIG (GMAW)
This combination works well for most fabrication tasks involving mild steel.
Mild steel is a type of carbon steel with relatively low carbon content (typically 0.05–0.25%).
Suppliers may list:
These are generally referring to the same category of filler metals.
The most important specification is the AWS classification, not the marketing label.
Example: ER70S-6
| Code | Meaning |
|---|---|
| ER | Electrode or Rod |
| 70 | 70,000 psi tensile strength |
| S | Solid wire |
| 6 | Chemical composition variant |
All common MIG mild steel wires are part of the ER70 family.
Most widely used wire for general fabrication.
Designed for use on clean base material without scale or rust.
The Miller 212 can run multiple wire diameters.
| Diameter | Typical Use |
|---|---|
| 0.023" | thin sheet metal (auto body) |
| 0.030" | general purpose |
| 0.035" | general purpose, thicker material |
| 0.045" | heavy industrial fabrication |
0.035" ER70S-6 provides a good balance between control and penetration.
Solid MIG wire requires shielding gas.
C25 (75% Argon / 25% CO₂)
Benefits:
100% CO₂
Characteristics:
Requires shielding gas.
Advantages:
Does not require shielding gas.
Advantages:
Disadvantages:
Solid wire with shielding gas is typically preferred in shared shop environments.
Look for:
Common manufacturers:
Avoid very low-cost wire, which can cause feeding inconsistencies.
| Goal | Recommendation |
|---|---|
| General shop wire | ER70S-6 |
| Best all-around diameter | 0.030" or 0.035" |
| Cleanest weld appearance | ER70S-6 with C25 gas |
| Outdoor welding | Flux core E71T-11 |
| Beginner-friendly setup | ER70S-6 with C25 gas |