AWS A5.18/A5.18M · Carbon & Mild Steel
ER70S-6 Welding Electrode
ER70S-6 is the default solid MIG wire for carbon steel — high silicon and manganese let it weld over mill scale and light rust with good wetting.
- 70 ksi tensile
- Polarity DCEP
- 4 positions
- Medium, varies strongly with gas and transfer mode penetration
- MIG (GMAW)
What ER70S-6 means
| Part | Meaning |
|---|---|
| ER | Electrode or rod — usable as a continuously fed electrode (MIG) or a hand-fed rod (TIG) |
| 70 | 70,000 psi minimum tensile strength of the deposited weld metal |
| S | Solid wire |
| 6 | Chemistry classification with the highest silicon and manganese levels in the S-series |
ER70S-6 specifications
| AWS specification | AWS A5.18/A5.18M |
|---|---|
| Process | MIG (GMAW) |
| Form | Solid wire |
| Polarity | DCEP |
| Welding positions | Flat, Horizontal, Vertical, Overhead |
| Tensile strength (min) | 70 ksi (480 MPa) |
| Yield strength (min) | 58 ksi (400 MPa) |
| Elongation (min) | 22% |
| Impact toughness | 20 ft·lb at -20 °F (27 J at -29 °C) |
| Coating / core | None — bare solid wire, often copper coated for feedability and contact |
| Penetration | Medium, varies strongly with gas and transfer mode |
| Deposition rate | High, continuous feed with no stub loss |
| Slag | None; silicon islands float to the surface and are brushed off |
| Arc character | Smooth and stable; crackling bacon in short circuit, hissing in spray |
| Shielding gas | 75% argon / 25% CO2 (C25) |
ER70S-6 amperage by diameter
Typical operating ranges. Start near the middle of the range, then adjust by sound and bead profile. Reduce 10–15% for vertical and overhead work.
| Diameter | Amperage range | Typical start |
|---|---|---|
| 0.023 in (0.6 mm) | 30–90 A | 60 A |
| 0.030 in (0.8 mm) | 50–180 A | 115 A |
| 0.035 in (0.9 mm) | 70–220 A | 145 A |
| 0.045 in (1.2 mm) | 120–320 A | 220 A |
Polarity: DCEP for GMAW — this is standard for all solid MIG wire and is usually not adjustable on small machines. Used as a TIG rod it is hand-fed and the polarity is set by the tungsten (DCEN).
Shielding gas for ER70S-6
| Gas | Notes |
|---|---|
| 75% Ar / 25% CO2 | The shop standard. Least spatter, good bead appearance, works in short circuit and spray. |
| 100% CO2 | Deeper penetration and lower cost, but more spatter and a harsher arc. Short-circuit transfer only. |
| 90% Ar / 10% CO2 | Used for spray and pulsed transfer on thicker material. |
| 98% Ar / 2% O2 | Spray transfer with excellent wetting on plate. |
Flow rate: 20–25 CFH (9–12 L/min); increase outdoors or raise a windscreen
What ER70S-6 is used for
- General fabrication and shop welding on carbon steel
- Automotive body and chassis work
- Structural and miscellaneous metal fabrication
- Robotic and semi-automatic production welding
- Repair welding over mill scale or lightly rusted steel
Base metals
- A36 structural steel
- 1018 and other low-carbon steels
- HSLA steels up to 70 ksi
- Automotive sheet and tubing
Characteristics
- Highest silicon and manganese content in the ER70S family, which is what lets it handle surface oxides
- Silicon deoxidizers leave glassy islands on the bead that brush off easily
- Excellent wetting and a flat-to-slightly-convex bead profile
- Interchangeable with ER70S-3 for clean steel; ER70S-6 is the safer default on real-world material
- Also sold as a TIG rod under the same classification
Storage and handling
Keep spools dry and covered. Bare wire rusts, and rusty wire means porosity and feed problems.
- Leave the spool in the machine only if the cabinet is closed; otherwise bag it with a desiccant.
- Do not touch the wire with bare hands — skin oils and salts contaminate the surface.
- A spool with visible surface rust should be discarded; it will feed poorly and leave porosity.
- Store in a heated area to avoid condensation when the shop warms up in the morning.
Welding tips
- For short-circuit on 1/8 in plate, start around 19–20 V and 250–280 ipm wire speed with 0.035 in wire.
- Stickout of about 3/8 in is the sweet spot for short circuit; too long and the arc gets cold and ropey.
- Listen for a steady crackle in short circuit — popping means the voltage is too low, hissing and spatter means too high.
- Spray transfer needs at least 80% argon and roughly 24–28 V; it will not work on CO2.
- Push the gun for a flatter bead on thin material, drag for more penetration on plate.
ER70S-6 frequently asked questions
What gas do you use with ER70S-6?
75% argon / 25% CO2 is the shop standard — a smooth arc with minimal spatter. Straight CO2 costs less and penetrates deeper but spatters more and is limited to short-circuit transfer.
What is the difference between ER70S-6 and ER70S-3?
ER70S-6 has more silicon and manganese, so it tolerates mill scale, rust and surface oxides better and wets out flatter. ER70S-3 is fine on clean steel and costs slightly less. Most shops stock only ER70S-6.
Can ER70S-6 be used as a TIG rod?
Yes. The ER prefix means it qualifies as both a continuously fed electrode and a hand-fed rod, and it is commonly sold in 36 in TIG lengths.
What settings for 0.035 in ER70S-6 on 1/8 in steel?
Roughly 19–20 V with 250–280 ipm wire feed in short-circuit transfer on C25 gas, which works out near 140–160 A. Fine-tune by sound and bead profile.
Can you weld rusty metal with ER70S-6?
Light mill scale and surface rust, yes — that is what the extra silicon and manganese are for. Heavy rust, paint or oil will still cause porosity; grind the joint clean when you can.
Compare ER70S-6 with
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