ER70S-2 and ER70S-3 are separate AWS A5.18 carbon-steel solid-filler classifications, not interchangeable labels for “seventy-series TIG rod.” Buy the grade named by the qualified welding procedure or approved job requirement. When comparing off-the-shelf GTAW rods, ER70S-2 offers a documented multi-deoxidizer chemistry in Lincoln’s example; ESAB also sells a distinct ER70S-3 TIG cut-length product. Neither is permission to weld contaminated metal or substitute a grade without approval.
This article addresses the actual TIG/GTAW cut-length purchasing decision. It does not turn every ER70S-3 MIG/GMAW wire spool into a suitable TIG package. Verify the welding process, cut-length form, diameter, manufacturer order number, selling unit and any material traceability requirement before making a substitution or writing a purchase order.
The chemistry distinction matters
Lincoln Electric’s ER70S-2 TIG datasheet describes deoxidizers that include silicon and manganese plus zirconium, titanium and aluminum. That is the source of its commonly described triple-deoxidized behavior. It can influence selection for certain carbon-steel fit-up and repair work, but the manufacturer’s application notes do not waive cleaning or the welding procedure’s limitations.
ESAB’s TIG Weld 70S-3 product page identifies a copper-coated TIG rod classified AWS A5.18 ER70S-3 and offers named cut-length packages. The existence of a real ER70S-3 TIG rod is different from assuming a similarly titled spool wire is the same selling item. Use the exact manufacturer’s product line, not an abstract grade alone.
Both may appear in carbon-steel fabrication conversations, but their chemistry and classification suffixes differ. A buyer should never reduce this to “both are seventy-thousand-pound strength” without confirming the governing WPS and inspection requirements. A project may have chemical composition, impact or traceability obligations that are not captured by the broad family name.
Classification strength is not a substitute for a weld procedure
The ER70S family indicates a nominal filler-metal tensile-strength class under the cited specification. It does not promise that every deposited weld on every base metal will have identical mechanical behavior. Manufacturer test sheets contain either specification thresholds or typical results for specific conditions. Do not carry a manufacturer’s typical property into a purchase specification as a guaranteed acceptance figure.
If the job involves pressure-containing equipment, a structural connection, repair to material with uncertain grade, elevated temperature, impact toughness or a customer-controlled procedure, identify the required filler and any essential variables in the actual documentation. Whether an alternative classification can be used is a technical approval decision, not a retailer substitute suggestion.
Confirm the actual GTAW product form
Suppliers may carry ER70S-2 TIG cut lengths and ER70S-3 GMAW spools under very similar search terms. For TIG, confirm that a product is sold as straight GTAW rods, with the required diameter, length and package quantity or weight. Lincoln’s published ER70S-2 sheet lists specific diameter/packaging combinations; ESAB’s TIG Weld 70S-3 similarly lists identified rods and manufacturer product numbers.
Do not order from an image alone. A marketplace photo of loose filler rods does not establish whether the delivered article is a ten-pound tube, a different diameter or a GMAW coil. Match the actual manufacturer stock number to the purchase order and confirm the package description on the seller’s current offer.
How the surface condition enters the decision
The deoxidizer discussion is often misunderstood as permission to weld over paint, oil, scale or unidentified coatings. It is not. The work must meet the cleaning, fit-up and shielding requirements of the procedure and manufacturer. Poor preparation can defeat the intended purpose of a correctly selected filler and cause quality problems independent of the nominal AWS classification.
Ask whether the part is clean carbon steel or an uncertain repair, whether the steel grade is documented, and whether the joint has service requirements beyond routine shop fabrication. If those facts are unknown, label them “Unknown — verify” before choosing one grade over another. A low-effort assumption at ordering time can create a high-effort deviation report later.
What a buyer should verify for ER70S-2
Lincoln’s ER70S-2 material references include mild and low-alloy-steel repair, small-diameter tubing, sheet-metal work and pipe root-pass applications as typical examples. These are informative, not blanket permission for every form of those joints. Use the product classification, diameter, package and lot certificate only after the job’s actual material and WPS requirements are confirmed.
The WSP ER70S-2 TIG grade page is a useful classification starting point, but should not be treated as an approved welding procedure. Check the source manufacturer’s current datasheet and an actual certified product where documentation is required. Do not infer acceptance from a label on an older unopened tube.
What a buyer should verify for ER70S-3
ESAB provides a named TIG Weld 70S-3 line for steel applications. Read its current document for the exact item, diameter, length and package. An ER70S-3 MIG wire product can belong to the same classification family without having the appropriate supplied form for the job. That matters in a shop receiving department where the product description may be shortened to the grade and diameter.
Also verify that the customer or WPS permits ER70S-3 in the first place. Do not use the fact that a producer markets it for clean butt or fillet joints as an approval for a specific code-controlled assembly. The decision to change a grade may require review by the welding coordinator or responsible engineer.
A purchasing and receiving checklist
- Approval: WPS number, controlling AWS specification, base-metal identification, customer rules and any alternative filler approval.
- Classification: ER70S-2 versus ER70S-3 must be explicit, including the proper process.
- Product: manufacturer, actual catalog number, cut length versus spool wire, diameter and order package.
- Traceability: lot or batch information, certificate availability and receiving documentation when required.
- Fit for duty: service temperature, required toughness/inspection, cleanliness, joint type and proper gas-shielding controls.
Write the purchase request in a way that receiving staff can verify: “AWS A5.18 ER70S-3 GTAW cut-length rod, specified diameter and manufacturer’s part number, package as approved by the WPS,” rather than the vague “70S rod.” That record also makes later batch or substitution investigations more straightforward.
Use selection tools as a starting point only
The WSP Filler Metal Finder helps narrow candidate classifications and product families; the WSP Alloy Support directory provides additional grade routes. Both are navigation and education resources, not substitutes for formal WPS, engineering or code approvals. See also WSP’s ER70S-2 TIG selection notes for related verification questions.
Decision: buy the documented grade and the correct physical product, not a near-matching description. ER70S-2 has Lincoln-documented multiple deoxidizers; ER70S-3 exists in an ESAB-documented TIG rod. Neither can be treated as a universal substitute for the other. Resolve an unknown material, WPS, diameter or package before releasing the order.
Sources checked October 26, 2026: Lincoln Electric ER70S-2 TIG; ESAB TIG Weld 70S-3. Manufacturer data applies to the exact documented product and is not independent job qualification.
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