Stainless Steel ER308LSi vs ER309LSi
Stainless Steel · grade comparison
Stainless Steel ER308LSi and ER309LSi are both stainless steel grades. Both yield at about 400 MPa — strength does not separate them. ER309LSi is harder — 185 HB against 165 HB for ER308LSi — which matters for wear surfaces and threads. ER309LSi runs hotter in service (950°C vs 425°C continuous). On the shop floor, ER308LSi forms better (very good vs good) and ER308LSi sits in a lower cost tier (premium, $$$) than ER309LSi (high, $$$$).
ER308LSiChoose it when cost is the deciding factor.
ER309LSiChoose it when surface hardness matters, or when the part sees heat.
ER308LSi vs ER309LSi: 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
Bulk Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Reduction in Area
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Same in both: Yield Strength (0.2% offset) 400 MPa58 ksi · Elongation at Break 38% · Compressive Strength 400 MPa58 ksi
Physical
Density and transition temperatures.
Same in both: Density 7.9 g/cm³0.29 lb/in³ · Melting Point (Solidus) 1,400°C2,552 °F · Liquidus Temperature 1,450°C2,642 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Max Service Temperature (continuous)
Min Service Temperature
Same in both: Thermal Conductivity 15 W/m·K8.7 BTU/hr·ft·°F · Specific Heat Capacity 500 J/kg·K0.12 BTU/lb·°F
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)
Polishability
Castability
Same in both: Brazeability / Solderability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Water
Typical Recycled Content
Same in both: Embodied Energy (primary production) 60 MJ/kg25,795 BTU/lb · Embodied Carbon (primary production) 5.5 kg CO₂/kg
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Same in both: Thermal Diffusivity 3.8 mm²/s · Thermal Shock Resistance Index 3
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 | ER308LSi | ER309LSi |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$ Premium | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 7 finishes: Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Pickling, Plasma Spray, Silver Plating.
ER308LSi vs ER309LSi — frequently asked
What is the difference between ER308LSi and ER309LSi?
Stainless Steel ER308LSi and ER309LSi are both stainless steel grades. Both yield at about 400 MPa — strength does not separate them. ER309LSi is harder — 185 HB against 165 HB for ER308LSi — which matters for wear surfaces and threads.
Which is cheaper, ER308LSi or ER309LSi?
ER308LSi is the lower-cost material: it sits in the premium tier ($$$) while ER309LSi is high ($$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
When should I choose ER308LSi over ER309LSi?
Pick ER308LSi when cost is the deciding factor. Pick ER309LSi when surface hardness matters, or when the part sees heat.
Ready to make it?
Upload a CAD file and FabDigit prices the part in ER308LSi and ER309LSi 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.