Flux-Core vs MIG: Which Process Should You Use?

Flux-core and MIG welding use the same basic equipment, a wire feeder pushes wire through a gun. The difference is whether the shielding comes from the wire itself (flux-core) or from an external gas bottle (MIG). This affects where you can weld, how the weld looks, and what it costs.

MIG (Solid Wire + Gas)

MIG welding uses solid wire (like ER70S-6) with external shielding gas, typically 75% argon / 25% CO2. The gas protects the weld pool from atmospheric contamination.

Advantages: Clean welds with minimal spatter. No slag to chip. Better appearance. Easier to weld thin material. Lower fume levels.

Disadvantages: Cannot weld in wind. Gas bottle adds cost and is one more thing to transport. Gas flow rates need to be correct.

Wind tolerance is the primary advantage of self-shielded flux-core. In open-air structural work, pipeline construction, and field repairs, maintaining gas coverage with MIG is impractical or impossible. Self-shielded FCAW was designed specifically for these conditions.

Self-Shielded Flux-Core

Self-shielded flux-core (FCAW-S) uses tubular wire with flux inside that generates its own shielding gas. Common wires: E71T-11, E71T-GS.

Advantages: Works outdoors in wind. No gas bottle needed. Deeper penetration on thicker steel. Simpler setup.

Disadvantages: Heavy slag that must be removed. More spatter. Rougher bead appearance. Higher fume levels. Not as clean on thin material.

Gas-Shielded Flux-Core

Gas-shielded flux-core (FCAW-G) uses tubular wire with external gas shielding. Common wire: E71T-1. This is a production process used in fabrication shops.

Advantages: Highest deposition rate of any semi-automatic process. Excellent mechanical properties. D1.1 prequalified. All-position.

Disadvantages: Requires gas like MIG. Equipment and wire cost more. Produces slag. Not for beginners.

Decision Framework

Welding outdoors or in wind? Self-shielded flux-core. Thin material or auto body? MIG. Thick structural steel in a shop? Gas-shielded flux-core or MIG. Budget setup, no gas bottle? Self-shielded flux-core. Cleanest welds with least cleanup? MIG. Maximum speed on heavy plate? Gas-shielded flux-core.

Many small welders can run both MIG and self-shielded flux-core by switching the polarity and drive rolls. Having both options available is the most versatile setup.

Classification system defined by .