Steel ER120S-1
UNS K21030
ER120S-1 (K21030) is a Ni-Cr-Mo alloyed solid welding wire for GMAW and GTAW, depositing roughly 120 ksi (830 MPa) class weld metal in the low-alloy steel filler family.
Reference datasheet — ER120S-1 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the AW condition
ER120S-1 tempers and conditions
ER120S-1 is supplied in 3 conditions, soft to hard. AW is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Post-weld heat treated | Use when code or distortion control requires stress relief; expect a strength drop of roughly 50–100 MPa with slightly higher ductility. | 740 | 810 | 20 | 23 HRC | 7 % IACS |
AWDefault As-welded deposit | Standard qualification and production condition for 120 ksi joints on HY-100/HSLA-100 and armor plate. | 810 | 880 | 18 | 27 HRC | — |
As-welded, GTAW with 100% argon | Pick for root passes, thin sections and repair where the lowest oxygen/highest-toughness deposit is wanted. | 830 | 900 | 19 | 28 HRC | 7 % IACS |
Supply forms, finishes and certifications
Ways ER120S-1 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
WIRE | Filler wire as supplied | Supply form |
What is ER120S-1?
ER120S-1 (K21030) is a Ni-Cr-Mo alloyed solid welding wire for GMAW and GTAW, depositing roughly 120 ksi (830 MPa) class weld metal in the low-alloy steel filler family. It is selected to match quenched and tempered base metals such as HY-100 and armor plate, with typical deposit properties of 810 MPa yield, 880 MPa tensile, 18 % elongation, 270 HB (27 HRC) and service to 400 °C; it is supplied as spooled wire and cut TIG lengths. At this strength level low-hydrogen practice, preheat and heat-input control are mandatory, and the deposit has no corrosion resistance. Where 100 ksi weld metal is sufficient, a lower-strength Ni-Mo wire is the usual alternative. ER120S-1 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,450°C (2,642 °F). ER120S-1 has a yield strength of 810 MPa (117 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 87% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
What is ER120S-1 used for?
- high-strength structural steel welding
- military/armor plate repair
- high-pressure vessel welds
- off-highway equipment
Advantages
- High strength — 810 MPa (117 ksi), better than 87% of steel grades
Limitations
- Difficult to machine — 35/100, worse than 84% of steel grades
ER120S-1 properties
Typical room-temperature values for ER120S-1-AW; bars are the position among steel grades.
Physical3
ER120S-1 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
ER120S-1 has a yield strength of 810 MPa (117 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 87% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
ER120S-1 is rated for continuous service to 400°C (752 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
ER120S-1 conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of ER120S-1 takes about 32 MJ of energy and emits 2.4 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 25%.
Manufacturability6
ER120S-1's machinability is fair (35/100, worse than 84% of steel grades); weldability good (65/100); formability fair (35/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. ER120S-1 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with ER120S-1
Is ER120S-1 easy to machine?
Weld deposit at ~270 HB machines like Q&T 4340 at low hardness — use carbide, rigid setups and modest speeds; grind rather than mill for cap dressing.
Can ER120S-1 be welded?
Low-hydrogen practice is mandatory: dry gas, clean plate, preheat/interpass per base-metal carbon equivalent (typically 100–150 °C for HY-100), controlled heat input to keep both strength and −51 °C toughness.
Can ER120S-1 be formed, bent or molded?
Not a forming grade; the product is drawn wire supplied on spools or as cut TIG lengths — protect from moisture and mechanical damage to preserve feedability.
ER120S-1 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CAWS A5.28 max | ≤ 0.1 | 0.08 |
| Mn | 1.4 – 1.8 | 1.6 |
| Si | 0.25 – 0.6 | 0.45 |
| Ni | 1.9 – 2.6 | 2.25 |
| Cr | 0.3 – 0.65 | 0.45 |
| Mo | 0.4 – 0.65 | 0.55 |
| V | ≤ 0.03 | |
| Tideoxidizer/microalloy | ≤ 0.1 | 0.03 |
| Zr | ≤ 0.1 | 0.03 |
| Al | ≤ 0.1 | 0.03 |
| Cuincluding copper coating | ≤ 0.25 | |
| P | ≤ 0.01 | |
| S | ≤ 0.01 | |
| Fe | balance |
What surface finishes work on ER120S-1?
Weld metal rusts quickly; blast or grind, then prime/paint or metallize. Avoid electroplating without baking due to hydrogen embrittlement risk at this strength level.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel ER120S-1 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- K21030
- Other
- ER83S-1
How much does ER120S-1 cost?
ER120S-1 is a premium-cost steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
ER120S-1 — frequently asked
What is ER120S-1 used for?
ER120S-1 is typically used for high-strength structural steel welding, military/armor plate repair, high-pressure vessel welds and off-highway equipment. In short: 120 ksi class weld metal; matches HY-100 and armor; toughness rated to −51 °C.
What is the yield strength of ER120S-1?
ER120S-1 has a typical yield strength of 810 MPa (117 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is ER120S-1 easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of steel grades). Weld deposit at ~270 HB machines like Q&T 4340 at low hardness — use carbide, rigid setups and modest speeds; grind rather than mill for cap dressing.
Can ER120S-1 be welded?
Yes — weldability is rated good (65/100). Low-hydrogen practice is mandatory: dry gas, clean plate, preheat/interpass per base-metal carbon equivalent (typically 100–150 °C for HY-100), controlled heat input to keep both strength and −51 °C toughness.
What surface finishes work on ER120S-1?
Weld metal rusts quickly; blast or grind, then prime/paint or metallize. Avoid electroplating without baking due to hydrogen embrittlement risk at this strength level.
Can ER120S-1 be formed, bent or molded?
Not a forming grade; the product is drawn wire supplied on spools or as cut TIG lengths — protect from moisture and mechanical damage to preserve feedability.
What is the maximum service temperature of ER120S-1?
ER120S-1 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between ER120S-1-AW and ER120S-1 PWHT?
AW is the default condition — standard qualification and production condition for 120 ksi joints on HY-100/HSLA-100 and armor plate. PWHT: use when code or distortion control requires stress relief; expect a strength drop of roughly 50–100 MPa with slightly higher ductility. Yield strength is 810 MPa in AW versus 740 MPa in PWHT.
How much does ER120S-1 cost?
ER120S-1 is a premium-cost steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- AWS A5.28/A5.28M — Low-Alloy Steel Electrodes and Rods for Gas Shielded Arc Welding — American Welding Society (2020)
- ASM Handbook Vol. 6 — Welding, Brazing and Soldering — ASM International (1993)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- High-strength low-alloy GMAW/GTAW wire datasheets (120 ksi class) — Lincoln Electric / ESAB / voestalpine Böhler Welding (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.