The Harris ER70S-2 Mild Steel TIG (GTAW) Welding Rod, .045 in × 36 in, 10 lb Package (E70S2H0) is a triple-deoxidized carbon steel filler rod that sets the standard for clean, porosity-free TIG welds on carbon steel, galvanized steel, and marginally prepared base metals. The triple-deoxidizer system — aluminum, titanium, and zirconium (in addition to silicon and manganese) — aggressively scavenges oxygen and sulfur from the weld puddle, making ER70S-2 the preferred choice for pipe root passes, repairs on rusty or mill-scaled plate, and structural work where surface condition cannot be perfectly controlled. At .045 in diameter, this rod is sized for thin wall pipe, sheet metal, and precision TIG work at 40–120 A.
| Specification | Value |
|---|---|
| Manufacturer | Harris Products Group |
| Part Number | E70S2H0 |
| AWS Classification | ER70S-2 (AWS A5.18 / A5.18M) |
| Diameter | .045 in (1.2 mm) |
| Length | 36 in (914 mm) |
| Package Weight | 10 lb (4.5 kg) |
| Deoxidizers | Al + Ti + Zr (triple-deoxidized) plus Mn, Si |
| Tensile Strength (as-welded) | 70,000 psi (483 MPa) minimum |
| Yield Strength (as-welded) | 58,000 psi (400 MPa) minimum |
| Elongation | 22% minimum |
| Charpy Impact | 20 ft-lb (27 J) @ −20°F (−29°C) |
| Process | GTAW (TIG) |
| Polarity | DCEN (DC electrode negative) |
| Shielding Gas | 100% Argon; Ar–He blends |
| Preheat | Not required for mild steel under 1 in thick at low hydrogen conditions |
| Compatible Base Metals | A36, A53, A106, A516, ASTM 1010–1020, 4130 (mild-strength applications) |
| Positions | All (1G, 2G, 3G, 4G, 5G, 6G) |
Source: Harris Products Group ER70S-2 technical data and AWS A5.18/A5.18M Carbon Steel Electrodes and Rods for GTAW Standard.
- Pipe Welding Root Passes: ER70S-2 is the API 1104 and ASME B31.3 workhorse for process pipe root passes. Its triple-deoxidizer chemistry produces a smooth, full-penetration root bead even on base metal with light mill scale or contamination that would cause porosity with ER70S-6. The .045 in diameter is ideal for 2 in–4 in schedule pipe root beads in the 5G and 6G positions.
- Structural Steel Fabrication: A36 and A572 structural shapes, pipe columns, beam connections, and miscellaneous structural ironwork where 70 ksi weld deposit meets AWS D1.1 structural filler requirements.
- Automotive & Sheet Metal: Thin-gauge steel body panels (.045 in diameter gives precise puddle control at 40–80 A), exhaust flanges, fuel tank fabrication, and frame repair on mild-steel unibody structures.
- Repair & Maintenance: Welding over mill scale, rust, or primer where the base metal surface cannot be fully cleaned. The triple-deoxidizer system outperforms ER70S-6 in this scenario by providing additional oxygen scavenging capacity.
- 4130 Chrome-Moly (low-strength): For non-critical or decorative 4130 tube welding (bicycle frames, roll cage cosmetic repairs) where PWHT will not be performed and 70 ksi strength is adequate. For structural or high-strength 4130 applications, use ER80S-B2 or ER80SD-2 filler.
Both are carbon steel TIG fillers meeting 70 ksi tensile strength, but they differ in deoxidizer chemistry:
| Property | ER70S-2 | ER70S-6 |
|---|---|---|
| Deoxidizer system | Al + Ti + Zr + Si + Mn (triple) | High Si + Mn only |
| Tolerance for surface contamination | Excellent (designed for mill scale, light rust) | Moderate (needs clean base metal) |
| Bead appearance | Good, some silica islands possible | Excellent, smooth, glassy bead face |
| Pipe root pass performance | Industry standard choice | Acceptable but less forgiving |
| Preferred for | Pipe roots, repair work, contaminated surfaces | Sheet metal, clean structural, high-bead-appearance applications |
See sibling sizes: Harris ER70S-2 1/16 in. Browse the TIG rod collection for the complete range. Pair with the Lincoln Precision TIG 225 or Aspect 230 for a complete DC TIG carbon steel setup.
Why does ER70S-2 have triple deoxidizers and why does that matter?
The triple deoxidizer system in ER70S-2 (aluminum, titanium, and zirconium, in addition to the silicon and manganese in all ER70S fillers) reacts with oxygen and sulfur in the weld pool and base metal surface contamination. Each element targets slightly different oxides and sulfides, making the combination far more effective than silicon and manganese alone. This is why ER70S-2 produces quality welds on mill-scaled or mildly rusty base metal where ER70S-3 or ER70S-6 would give porosity or lack of fusion.
Is ER70S-2 required for pipe welding per AWS or ASME codes?
ER70S-2 is not the only acceptable filler for pipe welding, but it is the most commonly specified for carbon steel pipe root passes per API 1104 and ASME B31.3 Process Piping because of its consistent performance. Qualification is by welding procedure specification (WPS) tested per ASME Section IX; any AWS A5.18 classified filler can be qualified. Many refinery and petrochemical plant specifications call out ER70S-2 by classification, not by brand.
Can I use .045 ER70S-2 for TIG welding heavy structural plate?
The .045 in diameter is primarily suited for thin-gauge work and pipe root passes at low amperage. For structural plate 1/4 in and thicker, move up to 1/16 in (1.6 mm) or 3/32 in (2.4 mm) diameter ER70S-2 for adequate deposition rate and efficiency. The .045 in diameter can be used for fill and cap passes on any thickness, but it's inefficient for thick-plate work because of the low deposition rate per rod length.
Does Harris ER70S-2 require any preheat for mild steel?
Preheat is generally not required for mild carbon steel (A36, A53) under 1 in thick when the hydrogen content of the welding process is controlled (TIG is inherently low-hydrogen). AWS D1.1 Table 4.2 provides preheat requirements by base metal carbon equivalent and plate thickness. For most shop TIG work on clean mild steel, no preheat is needed. For cold-weather welding below 32°F (0°C), preheat to at least 70°F (21°C) per AWS D1.1.