Stainless Steel ER308Si vs ER420
Stainless Steel · grade comparison
Stainless Steel ER308Si and ER420 are both stainless steel grades. ER420 is the stronger of the two: yield strength 1,350 MPa (196 ksi) against 400 MPa (58 ksi) for ER308Si, about 3.4 times as much; tensile strength follows at 1,650 MPa (239 ksi) vs 600 MPa (87 ksi). In exchange, ER308Si is the more ductile: elongation 38% versus 3% for ER420, and ER420 is harder (500 HB vs 175 HB). ER420 is lighter (7.7 g/cm³ vs 7.95 g/cm³ for ER308Si) and ER308Si runs hotter in service (760°C vs 400°C continuous). On the shop floor, ER308Si machines more easily (fair vs not recommended) and ER308Si welds better (excellent vs fair).
ER308SiChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
ER420Choose it when strength drives the design, or when weight is the constraint.
ER308Si vs ER420: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all stainless steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all stainless steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Hardness, Rockwell C
Same in both: Bulk Modulus 160 GPa23.2 Msi
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Liquidus Temperature
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Max Service Temperature (continuous)
Min Service Temperature
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Brazeability / Solderability
Polishability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 55%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every stainless steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | ER308Si | ER420 |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$ Premium | $$$ Premium |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 7 finishes: Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Pickling, Plasma Spray, Silver Plating.
ER308Si vs ER420 — frequently asked
Is ER420 stronger than ER308Si?
Yes. ER420 has a typical yield strength of 1,350 MPa (196 ksi) against 400 MPa (58 ksi) for ER308Si — about 3.4 times as much. Tensile strength is 1,650 MPa (239 ksi) vs 600 MPa (87 ksi).
Which is cheaper, ER308Si or ER420?
Both sit in the same relative cost tier ($$$, premium); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, ER308Si or ER420?
ER308Si. Its machinability rates fair (40/100) against not recommended (12/100) for ER420; for welding the order is ER308Si first (excellent, 95/100) then ER420 (fair, 35/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in ER308Si and ER420 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.