Stainless Steel ER420
UNS S42080
ER420 is a higher-carbon martensitic stainless filler wire (UNS S42080) for matching hardenable 420-type cutlery and tooling stainless.
Reference datasheet — ER420 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
ER420 tempers and conditions
ER420 is supplied in 6 conditions, soft to hard. AW is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Use when the whole repaired part is fully annealed for extensive machining before final hardening. | 450 | 760 | 18 | 215 HB | — |
PWHT 600–700 °C | Choose when the repair must be machined or when a tougher, less crack-sensitive deposit is required at moderate hardness. | 850 | 1,050 | 13 | 33 HRC | — |
PWHT 350–450 °C | Compromise temper for tools needing ~45 HRC; avoid holding near 475 °C where embrittlement and carbide sensitisation begin. | 1,250 | 1,500 | 7 | 45 HRC | 3.2 % IACS |
AWDefault As-welded deposit | Default condition straight off the arc — maximum hardness for wear surfacing, but brittle and crack-prone until tempered. | 1,350 | 1,650 | 3 | 50 HRC | — |
PWHT 200–300 °C | Pick when maximum wear hardness must be kept but hydrogen/quench stresses need relieving on hardfaced surfaces. | 1,450 | 1,700 | 5 | 49 HRC | 3.1 % IACS |
Q&T | Full re-heat-treatment of the welded assembly to restore uniform cutlery/die hardness of 52–56 HRC. | 1,550 | 1,850 | 4 | 54 HRC | — |
What is ER420?
ER420 is a higher-carbon martensitic stainless filler wire (UNS S42080) for matching hardenable 420-type cutlery and tooling stainless. It is selected when the repair must be hardened with the part: hardened deposits reach roughly 1350 MPa yield, 1650 MPa tensile and 50 HRC at only 3% elongation. Ductility, machinability (score 12) and crack resistance are all poor, so preheat, immediate tempering and grinding instead of cutting are normal practice, and service is limited to about 400 °C. ER410 is the softer, more weldable alternative. ER420 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,450°C (2,642 °F). ER420 has a yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 99% of stainless steel grades. Elongation at break is 3% and the elastic modulus is 200 GPa (29 Msi).
What is ER420 used for?
- Cutlery and blade repair welding
- Hardenable tool component joining
- Die and mould weld build-up
- Plastic-mould steel repair
- Wear surface overlay on 420 shafts
- Valve seat and sealing face rebuilding
Advantages
- High strength — 1,350 MPa (196 ksi), better than 99% of stainless steel grades
- High electrical conductivity — 3.1 % IACS, better than 99% of stainless steel grades
- Polishes to a fine finish — 80/100, better than 89% of stainless steel grades
- Conducts heat well — 24.9 W/m·K (14.4 BTU/hr·ft·°F), better than 87% of stainless steel grades
Limitations
- Limited ductility — 3%, worse than 100% of stainless steel grades
- Low fracture toughness — 20 MPa·√m (18.2 ksi·√in), worse than 100% of stainless steel grades
- Difficult to machine — 12/100, worse than 100% of stainless steel grades
- Limited formability — 10/100, worse than 95% of stainless steel grades
- Needs corrosion protection — 40/100, worse than 93% of stainless steel grades
ER420 properties
Typical room-temperature values for ER420-AW; bars are the position among stainless steel grades.
Physical3
ER420 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
ER420 has a yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 99% of stainless steel grades. Elongation at break is 3% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
ER420 is rated for continuous service to 400°C (752 °F). It conducts heat at 24.9 W/m·K (14.4 BTU/hr·ft·°F), better than 87% of stainless steel grades. Thermal expansion is 10.3 µm/m·K (5.72 µin/in·°F).
Electrical3
ER420 conducts electricity at 3.1 % IACS, better than 99% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (40/100), worse than 93% of stainless steel grades.
Sustainability4
Producing a kilogram of ER420 takes about 53 MJ of energy and emits 4.6 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 55%.
Manufacturability7
ER420's machinability is not recommended (12/100, worse than 100% of stainless steel grades); weldability fair (35/100); formability not recommended (10/100).
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 stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. ER420 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with ER420
Is ER420 easy to machine?
As-welded deposit at ~50 HRC is essentially grind-only; high-temper (650 °C) or full anneal first if turning/milling is needed, then re-harden.
Can ER420 be welded?
GTAW/GMAW/SAW on 410/420 base metal; preheat and interpass 200–300 °C, slow cool, then temper or anneal immediately to avoid hydrogen cracking — never leave untempered overnight.
Can ER420 be formed, bent or molded?
Not a wrought product form — supplied as spooled wire or cut TIG rod; the martensitic deposit has no useful cold formability.
ER420 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 A5.9 ER420 | 0.25 – 0.4 | 0.32 |
| Cr | 12 – 14 | 13 |
| Mn | ≤ 0.6 | 0.45 |
| Si | ≤ 0.5 | 0.35 |
| Ni | ≤ 0.75 | 0.3 |
| Mo | ≤ 0.75 | 0.2 |
| Cu | ≤ 0.75 | 0.15 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance |
What surface finishes work on ER420?
Grind and polish to a fine finish for wear/sealing surfaces, then passivate (nitric or citric) to restore the chromium oxide film; hard chrome or nitriding may be added for extra wear life.
Surface treatments FabDigit runs on stainless 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).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel ER420 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S42080
How much does ER420 cost?
ER420 is a premium-cost stainless 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.
ER420 — frequently asked
What is ER420 used for?
ER420 is typically used for cutlery and blade repair welding, hardenable tool component joining, die and mould weld build-up, plastic-mould steel repair, wear surface overlay on 420 shafts and valve seat and sealing face rebuilding. In short: hardest martensitic stainless filler; 50 HRC as-welded; grind-only after welding.
What is the yield strength of ER420?
ER420 has a typical yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 99% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is ER420 easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 100% of stainless steel grades). As-welded deposit at ~50 HRC is essentially grind-only; high-temper (650 °C) or full anneal first if turning/milling is needed, then re-harden.
Can ER420 be welded?
With care — weldability is rated fair (35/100). GTAW/GMAW/SAW on 410/420 base metal; preheat and interpass 200–300 °C, slow cool, then temper or anneal immediately to avoid hydrogen cracking — never leave untempered overnight.
What surface finishes work on ER420?
Grind and polish to a fine finish for wear/sealing surfaces, then passivate (nitric or citric) to restore the chromium oxide film; hard chrome or nitriding may be added for extra wear life.
Can ER420 be formed, bent or molded?
Not a wrought product form — supplied as spooled wire or cut TIG rod; the martensitic deposit has no useful cold formability.
What is the maximum service temperature of ER420?
ER420 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 ER420-AW and ER420-ANN?
AW is the default condition — default condition straight off the arc — maximum hardness for wear surfacing, but brittle and crack-prone until tempered. ANN: use when the whole repaired part is fully annealed for extensive machining before final hardening. Yield strength is 1,350 MPa in AW versus 450 MPa in ANN.
How much does ER420 cost?
ER420 is a premium-cost stainless 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 A5.9/A5.9M — Bare Stainless Steel Welding Electrodes and Rods — American Welding Society (2017)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- ASM Handbook Vol.6 — Welding, Brazing and Soldering — ASM International (1993)
- Martensitic stainless filler metal ER420 data sheets — Böhler Welding / Metrode / Lincoln Electric (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.