Do not replace ER70S-2 TIG rod with ER80S-D2 just because the latter begins with 80. They are different AWS filler classifications with different chemistry and intended applications. The correct choice comes from the approved welding procedure specification (WPS), identified base metal, required weld properties and service conditions. A purchasing shortcut based on strength alone is not an engineering substitution.
This guide compares two specific TIG/GTAW cut-length filler classifications, not an unspecified MIG spool or a named maker’s every package. Its purpose is to help a buyer or fabricator ask the right questions before a tube, rod or purchase order changes hands.
Start with the specification family, not the last digit
Lincoln lists its ER70S-2 TIG product under AWS A5.18/A5.18M, the carbon-steel solid-electrode and rod family. It describes ER70S-2 as a deoxidized mild-steel filler containing aluminum, titanium and zirconium along with silicon and manganese. Lincoln lists its ER80S-D2 TIG cut lengths under AWS A5.28/A5.28M, a low-alloy filler family, and identifies molybdenum as part of the product chemistry. Those differences are substantive, not a packaging-label preference.
The published Lincoln data for ER80S-D2 identifies a deposit-strength capability around 550 MPa (80 ksi) and highlights selected applications requiring strength after stress relief, including particular high-temperature-service pipe, fittings and forgings. That does not mean every ER80S-D2 weld meets that figure in every joint, nor that this filler is acceptable on any higher-strength steel.
A practical side-by-side decision check
| Question | ER70S-2 TIG | ER80S-D2 TIG |
|---|---|---|
| AWS filler family | A5.18/A5.18M | A5.28/A5.28M |
| Product character | Carbon-steel, multiple-deoxidizer filler | Low-alloy filler with molybdenum |
| Manufacturer examples | Mild-steel repair, sheet and small pipe/root work | Selected higher-strength and stress-relieved service |
| Selection gate | Approved WPS and job properties | Approved WPS, alloy/service and heat-treatment requirements |
| Safe to substitute by name? | No | No |
This comparison uses manufacturer product information as examples. The controlling code, edition, procedure qualification, actual consumable certificate and joint requirements still govern the job. A classification indicates the specified filler family; it does not itself authorize a change to the approved procedure.
What the deoxidizers do—and what they do not do
The “-2” in ER70S-2 relates to a formulation that includes aluminum, titanium and zirconium deoxidizers. In Lincoln’s TIG product description, these ingredients accompany silicon and manganese. Deoxidation can help manage oxygen-related weld quality concerns; it is not a license to weld through oil, paint, galvanizing or unidentified contamination. Fit-up, cleaning, gas coverage and procedure compliance still matter.
ER80S-D2 is not simply ER70S-2 with more of the same deoxidizers. Its low-alloy chemistry, notably molybdenum, is intended to address different weld-metal requirements. The D2 suffix is a classification detail worth checking against the exact wire chemistry and current manufacturer data sheet. Treat a seller’s short title such as “80K TIG rod” as incomplete evidence.
Why a higher nominal tensile class may be the wrong choice
A repair drawing might specify a base material and a WPS already qualified with ER70S-2. Upgrading on paper to an ER80 classification can change the weld-metal chemistry and potentially affect strength matching, hardness, ductility, toughness, heat-treatment response and procedure qualification. The direction and importance of those changes depend on the actual joint and service; this page does not assert a universal result.
Similarly, seeing “low alloy” on a bar or fitting does not prove ER80S-D2 is suitable. Low-alloy materials include different chromium, nickel and molybdenum combinations, and the required filler can vary substantially. Refer the question to the responsible welding engineer or procedure owner when the exact material, WPS or service conditions are unknown.
When ER70S-2 deserves consideration
A permitted ER70S-2 route may suit a carbon-steel TIG repair or root-pass application when the WPS specifies that classification, the relevant base-metal and property requirements agree, and the rod’s product form and diameter fit the procedure. Lincoln specifically identifies mild/low-alloy repair, small-diameter pipe/tubing and root-pass applications for its ER70S-2 cut lengths. That list is a description of typical uses, not blanket code approval.
For a shop changing from one supplier’s ER70S-2 rod to another’s, compare the full classification, applicable lot certification, diameter, length, surface condition, source specification and package quantity. Even a same-class replacement can require review under a particular customer or code-controlled purchasing process.
When ER80S-D2 deserves consideration
ER80S-D2 belongs in the discussion when the job explicitly calls for the D2 low-alloy classification or when engineering evaluates a molybdenum-bearing filler for higher-strength requirements. Lincoln’s product sheet includes applications involving strength after stress relieving. It does not support choosing ER80S-D2 simply because the word “stronger” sounds desirable.
If a specification names postweld heat treatment, elevated-temperature service or a particular low-alloy pipe/fitting grade, verify the procedure and base metal before ordering. Do not replace a chromium-molybdenum filler such as an approved B-series classification with D2 merely because both appear under AWS A5.28.
Six checks before the purchasing order
- Base metal: record the exact ASTM/ASME grade or other identified material, not just “carbon steel.”
- WPS: identify the approved process, filler specification/classification, any essential variables and qualification restrictions.
- Service: determine the required strength, toughness, operating temperature, corrosion conditions and any specified heat treatment.
- Consumable: confirm manufacturer, actual AWS designation, TIG cut-length form, diameter, length and certification requirements.
- Packaging: verify rods per tube or tube weight, order unit and lot traceability before copying a catalog line.
- Release: obtain the required engineering/quality acceptance for any substitution rather than interpreting this article as authorization.
Use the WSP tools without confusing lookup with approval
Start with the WSP Alloy Support directory, narrow the process through the Filler Metal Finder, and open the ER80S-D2 TIG classification reference. These tools help locate relevant grade information and possible catalog paths. They do not verify an exact buyable package or replace the WPS.
For context on a different carbon-steel choice, see our ER70S-2 versus ER70S-6 TIG guide. Its discussion of carbon-steel deoxidizers does not establish ER80S-D2 substitution rules.
Primary sources and final decision
Compare the current Lincoln ER80S-D2 TIG product sheet with the Lincoln ER70S-2 TIG product sheet. Match the product edition to your purchasing record, and consult the governing AWS A5.18 or A5.28 edition and qualified procedure when required.
Bottom line: ER70S-2 and ER80S-D2 answer different application and chemistry questions. When the job specifies a classification, buy that verified classification and package. When it does not, mark the selection Unknown—verify with the WPS or responsible engineer rather than guessing from a strength number.
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