Harris ER70S-6 is a copper-coated, solid MIG wire engineered for gas metal arc welding (GMAW) of mild and low-alloy carbon steels. Classified per AWS A5.18/A5.18M: ER70S-6, this wire carries the highest silicon and manganese deoxidizer package in the ER70S family — making it the top choice whenever base metal shows light mill scale, rust, or minor surface contamination. The elevated Mn (1.40–1.85 %) and Si (0.80–1.15 %) scavenge oxygen from the weld pool, yielding a clean, fluid bead with excellent wet-in at both joint toes. Whether you are running short-circuit transfer on sheet metal or spray transfer on structural plate, ER70S-6 delivers consistent arc stability, low spatter, and a smooth bead profile that minimizes post-weld cleanup.
| Parameter | Value |
|---|---|
| AWS Classification | ER70S-6 (AWS A5.18 / ASME SFA A5.18) |
| Available Diameters | 0.023 in, 0.030 in, 0.035 in, 0.045 in (0.6, 0.8, 0.9, 1.1 mm) |
| Shielding Gas | 75% Ar / 25% CO₂ (C25) preferred; 100% CO₂ acceptable |
| Polarity | DCEP (electrode positive) |
| Tensile Strength (typical) | 78,000–85,000 psi (538–586 MPa) |
| Yield Strength (typical) | 62,000–70,000 psi (427–483 MPa) |
| Elongation | 26–30 % in 2 in |
| Charpy V-Notch Impact | 40–60 ft-lbf at −20 °F (54–81 J at −29 °C) |
| Carbon (C) | 0.06–0.15 % |
| Manganese (Mn) | 1.40–1.85 % |
| Silicon (Si) | 0.80–1.15 % |
| Copper Coating | Yes — improves electrical contact and feedability |
ER70S-6 is the most widely used solid MIG wire in North America for carbon steel fabrication. Its broad deoxidizer package handles real-world base metal conditions that would cause porosity with lower-tier wires.
- Structural steel fabrication — beam-to-column fillet welds, gusset plates, and decking per AWS D1.1 Structural Welding Code
- Heavy equipment and agriculture — bucket rebuilds, frame repairs, loader arms, and trailer frames on medium-carbon plate
- Automotive and transportation — chassis components, exhaust hangers, and tubing on pickled-and-oiled or hot-rolled steel
- General fabrication shops — brackets, enclosures, conveyors, and furniture on ASTM A36, A572-50, and A516 grades
- Shipbuilding and railcar — stiffener-to-plate fillets on Class 1 hull plates where moderate deoxidation and fast travel speeds are required
- Pipe and pressure vessel — root and fill passes on P1 carbon steel up to 70 ksi with proper joint preparation
The ER70S-6 classification (per AWS A5.18) specifies a minimum 70,000 psi (480 MPa) tensile strength from the deposited weld metal, measured in the as-welded condition with 75 Ar / 25 CO₂ shielding gas. The "-6" suffix identifies the highest-deoxidizer variant in the family, containing both silicon and manganese above the levels found in ER70S-3 or ER70S-2. This additional chemistry provides two key advantages: (1) it tolerates base metal with up to light mill scale without causing porosity, and (2) it produces superior wetting action that results in flatter, wider beads with smoother toe transitions — reducing stress risers on loaded joints.
For short-circuit transfer (thin gauge, 24–11 gauge), target wire feed speeds of 150–250 in/min at 15–19 V. For globular and spray transfer on structural plate (3/16 in and heavier), run 280–450 in/min at 24–28 V with 75/25 gas. A 100 % CO₂ shielding gas is acceptable — it delivers deeper penetration at lower cost but produces more spatter and a narrower, more convex bead profile. For the cleanest production welds, use C25 (75 % Ar / 25 % CO₂).
| Diameter | Polarity | Gas | Voltage (V) | Wire Feed (in/min) | Amps (approx.) | Transfer Mode |
|---|---|---|---|---|---|---|
| 0.030 in | DCEP | 75/25 Ar/CO₂ | 16–19 | 150–300 | 60–130 | Short-circuit |
| 0.035 in | DCEP | 75/25 Ar/CO₂ | 17–22 | 150–350 | 80–175 | Short-circuit / Globular |
| 0.045 in | DCEP | 75/25 Ar/CO₂ | 22–28 | 200–450 | 130–280 | Globular / Spray |
| 0.045 in | DCEP | 100 % CO₂ | 24–29 | 200–450 | 140–290 | Globular |
Harris ER70S-6 is classified per AWS A5.18 / ASME SFA A5.18 as ER70S-6. The "ER" prefix means the wire can serve as both an electrode and a filler rod; "70" is the 70,000 psi minimum tensile strength; "S" denotes solid wire; and "6" identifies the high-Si/Mn deoxidizer chemistry group.
The standard recommendation is 75 % Argon / 25 % CO₂ (C25). This blend supports all transfer modes — short-circuit, globular, and spray — and produces low spatter with a flat bead profile. 100 % CO₂ also works and costs less per cubic foot, but it generates more spatter and a more convex bead. Never use 100 % Argon with steel MIG wire — the arc becomes unstable and silicon islands form excessively on the weld surface.
Yes — ER70S-6 is specifically formulated to tolerate light mill scale and minor surface rust better than ER70S-3 or ER70S-2 due to its elevated silicon and manganese deoxidizer levels. For heavy rust, grinder preparation is still required. ER70S-6 should not be used on heavily corroded or painted surfaces without proper prep.
Per AWS A5.18, ER70S-6 must meet a minimum 70,000 psi (480 MPa) tensile strength in the as-welded condition. Typical values with C25 gas run 78,000–85,000 psi (538–586 MPa) with yield strength of 62,000–70,000 psi and elongation of 26–30 %. These values exceed the base metal strength of ASTM A36 (58–80 ksi) — meaning welds routinely overmatch the plate.
ER70S-6 uses DCEP (DC Electrode Positive), also called reverse polarity. This is the standard polarity for all solid MIG wires. Connect the wire feed torch lead to the positive terminal and the work clamp to the negative terminal of your welder.
Both wires meet the 70 ksi minimum tensile requirement, but ER70S-6 contains significantly more silicon (0.80–1.15 % vs 0.45–0.75 %) and manganese (1.40–1.85 % vs 0.90–1.40 %). The extra deoxidizers in ER70S-6 make it better suited for dirty base metal, deliver superior bead wetting and toe wash-in, and allow faster travel speeds. Use ER70S-3 on clean, pickled steel when you want minimum silicon island buildup; use ER70S-6 for everything else.
Explore the full welding wire collection or see related Lincoln Electric wires: Innershield NR-211-MP for self-shielded outdoor work, or SuperArc L-56 for premium copper-coated MIG performance.