UltraCore® 121K3M-H Plus is Lincoln Electric's highest-strength low-alloy, all-positions gas-shielded flux-cored (FCAW-G) wire in the UltraCore "Plus" family, classified AWS A5.29 E121T1-GM-H4 and, under the combined specification, AWS A5.36 E121T1-M21A6-K3-H4 and E111T1-M21P4-K3-H4. Lincoln describes it as an innovative design capable of superior toughness at −60 °F in both the as-welded and stress-relieved conditions, at H4 diffusible hydrogen levels, running on a 75–80% Argon / balance CO₂ mixed gas. It is a 120 ksi tensile class consumable — a different structural proposition entirely from the 70 and 80 ksi wires that make up most flux-cored inventory. WeldingMart is an authorized Lincoln Electric distributor; every spool ships factory-sealed.
This page is the family hub for the 121K3M-H Plus line. Lincoln publishes it in 0.045 in (1.1 mm) — part number ED035423 and 0.052 in (1.3 mm) — part number ED035424, both on the 33 lb (15 kg) vacuum-foil-bagged fiber spool. Both are stocked here as individual listings, linked at the bottom of this page. Browse the wider range in the Welding Wire collection.
| AWS Classification | AWS A5.29 E121T1-GM-H4 |
|---|---|
| AWS A5.36 Classification | E121T1-M21A6-K3-H4; E111T1-M21P4-K3-H4 |
| Wire Type | Low alloy, gas-shielded flux-cored (FCAW-G) |
| Welding Positions | All |
| Shielding Gas | 75–80% Argon / balance CO₂ (M21); flow rate 40–50 CFH |
| Polarity | DC+ (DCEP — DC Electrode Positive) |
| Strength Class | 120 ksi tensile class |
| Diffusible Hydrogen | H4 (4.0 mL/100 g maximum); 1–3 mL/100 g typical |
| Available Diameters | 0.045 in (1.1 mm), 0.052 in (1.3 mm) |
| Package | 33 lb (15 kg) fiber spool, vacuum foil bag (VFB) |
| Part Numbers | ED035423 (0.045 in), ED035424 (0.052 in) |
| Lot Documentation | Q2 Lot® — certificate showing actual deposit chemistry and mechanical properties per lot, available online |
| Packaging Protection | ProTech® foil bag packaging |
| Brand / Manufacturer | Lincoln Electric |
Source: Lincoln Electric UltraCore 121K3M-H Plus product page and the published UltraCore 121K3M-H Plus datasheet.
- 120 ksi class strength with all-position operability: Published requirement is 745 MPa (108 ksi) minimum yield and 825–965 MPa (120–140 ksi) tensile — and it still runs vertical-up and overhead as a T1 rutile wire.
- Toughness at −60 °F in both conditions: Lincoln states superior toughness at −60 °F as-welded and stress-relieved, with published Charpy data for both states.
- H4 diffusible hydrogen: Typical measured hydrogen is 1–3 mL/100 g of weld deposit — well inside the 4.0 mL maximum, which matters greatly on a consumable this strong, because hydrogen cracking risk climbs with weld metal strength.
- Mixed-gas design: Formulated for 75–80% Argon / balance CO₂ (M21) rather than straight CO₂, which is part of how the alloy recovery and toughness are achieved.
- Q2 Lot® certification: Actual deposit chemistry and mechanical properties published per lot and retrievable online.
- ProTech® vacuum foil bag: Moisture-barrier packaging to preserve the low-hydrogen rating in storage.
- Offshore drilling rigs: Lincoln's first-listed application. High-strength nodes and heavy structural connections at low service temperature.
- Low-temperature storage tanks: Where both strength class and −60 °F impact performance are specified.
- Shipbuilding: High-strength hull and structural weldments requiring an all-position, high-deposition consumable.
- Construction: Heavy structural steel in the 120 ksi class — the strength range where undermatched filler is not an option and where hydrogen control becomes a controlling variable.
- Stress-relieved high-strength fabrication: Because Lincoln publishes properties after 1 hour at 620 °C (1150 °F), the wire can be specified where PWHT is mandatory without guessing at the post-PWHT result.
UltraCore 121K3M-H Plus runs DC+ (DCEP) on 75–80% Argon / balance CO₂ at 40–50 CFH. This is a gas-shielded wire and requires shielding gas.
The gas is not a convenience choice here. The published mechanical and chemical results were established on 75% Ar / 25% CO₂; the "M" in E121T1-GM-H4 designates the mixed-gas requirement. Running this wire on 100% CO₂ takes it outside its classification and outside the data Lincoln publishes. If your shop currently runs straight CO₂ for its 70 and 80 ksi flux-cored wires, plan for a second gas supply before adopting this consumable.
| Requirement — yield strength (0.2% offset) | 745 MPa (108 ksi) minimum |
|---|---|
| Requirement — tensile strength | 825–965 MPa (120–140 ksi) |
| Requirement — elongation | 14% minimum |
| Typical as-welded (75% Ar / 25% CO₂) — yield | 815–840 MPa (118–122 ksi) |
| Typical as-welded — tensile | 850–875 MPa (123–127 ksi) |
| Typical as-welded — elongation | 17–18% |
| Typical as-welded — CVN at −40 °C (−40 °F) | 65–67 J (48–50 ft·lbf) |
| Typical as-welded — CVN at −51 °C (−60 °F) | 59–61 J (44–45 ft·lbf) |
| Typical stress-relieved (1 hr at 620 °C / 1150 °F) — yield | 745–765 MPa (108–111 ksi) |
| Typical stress-relieved — tensile | 805–820 MPa (116–119 ksi) |
| Typical stress-relieved — elongation | 18–23% |
| Typical stress-relieved — CVN at −40 °C (−40 °F) | 32–37 J (23–27 ft·lbf) |
Typical values are Lincoln Electric published all-weld-metal test results, not lot guarantees. Yield strength is measured at 0.2% offset. Note that stress relief lowers both strength and impact values on this wire: as-welded Charpy at −40 °C is 65–67 J but 32–37 J after PWHT. If your procedure includes stress relief, design to the stress-relieved column.
| Carbon (C) | Typical 0.06–0.07% |
|---|---|
| Manganese (Mn) | Typical 1.61–1.80% |
| Silicon (Si) | Requirement 1.00% max; typical 0.26–0.35% |
| Nickel (Ni) | Typical 2.21–2.46% |
| Chromium (Cr) | Typical 0.04–0.07% |
| Molybdenum (Mo) | Typical 0.58–0.65% |
| Vanadium (V) | Typical 0.00% |
| Boron (B) | Typical 0.004–0.005% |
| Phosphorus (P) | Requirement 0.030% max; typical 0.010–0.011% |
| Sulfur (S) | Requirement 0.030% max; typical 0.007–0.012% |
| Diffusible hydrogen | Requirement 4.0 mL/100 g max; typical 1–3 mL/100 g |
The nickel-molybdenum-boron combination is the strengthening and toughening system that gets a T1 rutile flux-cored wire to 120 ksi while holding usable impact values at −60 °F. It is also why this wire is not a drop-in substitute in a procedure that limits alloy content or preheat.
Lincoln's published operating windows, 75–80% Argon / balance CO₂, DC+:
| 0.045 in (1.1 mm) | 175–500 in/min wire feed speed, 24–33 volts, approximately 120–220 amps, at 85–87% deposition efficiency. |
|---|---|
| 0.052 in (1.3 mm) | From 150 in/min wire feed speed, 26–29 volts, approximately 160 amps at the published low end, at 82–84% deposition efficiency. |
These are manufacturer-published windows, not a qualified procedure. On a 120 ksi consumable, heat input and interpass temperature control usually matter more to the outcome than reaching the top of the current range.
| 0.045 in (1.1 mm) — ED035423 | The wider operating window of the two (120–220 A) and the more controllable diameter out of position. Preferred for root and fill passes, thinner high-strength sections, and procedures with a heat-input cap. |
|---|---|
| 0.052 in (1.3 mm) — ED035424 | Higher deposition for fill and cap passes on heavier sections, at slightly lower published deposition efficiency (82–84% versus 85–87%). Still an all-position wire, but less forgiving vertical-up than 0.045 in. |
Lincoln does not publish a 1/16 in size in this product; if you need more deposition than 0.052 in provides, that is a process discussion rather than a diameter change.
- What does E121T1-GM-H4 mean?
- Under AWS A5.29: "E" electrode, "12" the 120 ksi tensile strength class, "1" all positions, "T1" tubular rutile flux running spray transfer, "G" general classification (chemistry as agreed between supplier and purchaser), "M" mixed argon-bearing shielding gas required, and "H4" diffusible hydrogen not exceeding 4 mL per 100 g of deposited metal.
- Can I run it on 100% CO₂?
- No. The classification specifies mixed gas and Lincoln publishes 75–80% Argon / balance CO₂ at 40–50 CFH. All published mechanical and chemical results were established on 75% Ar / 25% CO₂. Straight CO₂ puts the deposit outside both the classification and the published data.
- What happens to the properties after stress relief?
- Lincoln publishes both conditions. After 1 hour at 620 °C (1150 °F): yield 745–765 MPa (108–111 ksi), tensile 805–820 MPa (116–119 ksi), elongation 18–23%, and Charpy V-notch 32–37 J (23–27 ft·lbf) at −40 °C. Strength drops toward the specification minimum and impact values fall roughly by half versus as-welded, so PWHT work must be designed against the stress-relieved numbers.
- How does it compare to UltraCore 81K2C-H Plus and 81Ni1C-H Plus?
- Those are 80 ksi class wires designed for 100% CO₂. This is a 120 ksi class wire designed for 75–80% argon mixed gas, with roughly 2.2–2.5% nickel and 0.58–0.65% molybdenum in the deposit. They are not interchangeable: the gas, the strength class, and the alloy content are all different.
- Why is the H4 rating important on this wire specifically?
- Hydrogen-assisted cracking risk rises with weld metal strength. At 120 ksi class, hydrogen control stops being good practice and becomes a design requirement — which is why the typical 1–3 mL/100 g measured hydrogen and the vacuum foil bag packaging are called out as features rather than footnotes.
- What certification is available?
- Q2 Lot® — a certificate showing actual deposit chemistry and mechanical properties for the specific lot, available online from Lincoln. Request it for the exact part number when code, class society, or customer documentation is required.
- Which diameters and packages exist?
- 0.045 in (ED035423) and 0.052 in (1.3 mm) (ED035424), both on the 33 lb (15 kg) vacuum-foil-bagged fiber spool. Those are the only two published sizes.
Both published diameters are stocked as individual listings: 0.045 in, 33 lb spool (ED035423) | 0.052 in, 33 lb spool (ED035424) | All Welding Wire
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