ER70S-6 — What It Is and Why It Matters
ER70S-6 is the most commonly used solid MIG wire for welding mild and low-carbon steel. It is also widely used as TIG filler rod. The designation breaks down as: E (electrode), R (rod), 70 (70,000 PSI minimum tensile strength), S (solid wire), and 6 (highest silicon and manganese deoxidizer content in the AWS classification).
The higher silicon and manganese content in the "-6" classification provides better wetting, reduced porosity, and improved bead appearance compared to lower-deoxidizer variants like ER70S-2 and ER70S-3. This makes ER70S-6 more tolerant of mill scale, light rust, and surface contamination on the base metal — important for real-world shop conditions where material is not always perfectly clean.
ER70S-6 is available in all common diameters: .023", .030", .035", and .045" for MIG wire, and 1/16" through 1/8" for TIG rod. It is the default choice for mild steel welding and the wire you will find pre-loaded in most MIG welders sold to the consumer market.
Frequently Asked Questions
What is the difference between ER70S-6 and ER70S-2?
Both are solid steel MIG wires with 70,000 PSI tensile strength. ER70S-6 has higher silicon and manganese for better tolerance of contaminated surfaces. ER70S-2 has lower deoxidizer content but includes titanium, zirconium, and aluminum, making it slightly better for TIG applications on very clean material.
What size MIG wire should I buy?
For home and light shop use, .030" is the most versatile — it handles 22-gauge sheet metal up to about 3/16" plate. For material 3/16" and thicker, .035" provides better productivity. Production shops on heavy material often use .045" wire for maximum deposition rate.