Steel ER309L vs ER70S-3
Steel · grade comparison
Steel ER309L and ER70S-3 are both steel grades. ER70S-3 is the stronger of the two: yield strength 460 MPa (66.7 ksi) against 400 MPa (58 ksi) for ER309L, about 15% more. In exchange, ER309L is the more ductile: elongation 38% versus 28% for ER70S-3, and ER309L is harder (185 HB vs 160 HB). ER309L runs hotter in service (1,000°C vs 400°C continuous) and ER70S-3 conducts heat better (48 W/m·K vs 15.5 W/m·K). On the shop floor, ER70S-3 machines more easily (good vs fair) and ER70S-3 sits in a lower cost tier (budget, $) than ER309L (high, $$$$).
ER309LChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
ER70S-3Choose it when strength drives the design, or when the part is machined in volume.
ER309L vs ER70S-3: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all 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 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
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Rockwell C
Hardness, Vickers
Same in both: Bulk Modulus 160 GPa23.2 Msi · Fatigue Strength (Endurance Limit) 230 MPa33.4 ksi
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
Castability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
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 steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | ER309L | ER70S-3 |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $ Budget |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 9 finishes: Copper Plating, Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Manganese Phosphate, Plasma Spray, Silver Plating, Zinc Phosphate.
ER309L vs ER70S-3 — frequently asked
Is ER70S-3 stronger than ER309L?
Yes. ER70S-3 has a typical yield strength of 460 MPa (66.7 ksi) against 400 MPa (58 ksi) for ER309L — about 15% more. Tensile strength is 550 MPa (79.8 ksi) vs 580 MPa (84.1 ksi).
Which is cheaper, ER309L or ER70S-3?
ER70S-3 is the lower-cost material: it sits in the budget tier ($) while ER309L is high ($$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, ER309L or ER70S-3?
ER70S-3. Its machinability rates good (58/100) against fair (35/100) for ER309L; for welding the order is ER70S-3 first (excellent, 95/100) then ER309L (excellent, 90/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in ER309L and ER70S-3 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.