Stainless Steel 304 vs 309S
Stainless Steel · grade comparison
Stainless Steel 304 and 309S are both stainless steel grades. 309S is the stronger of the two: yield strength 280 MPa (40.6 ksi) against 250 MPa (36.3 ksi) for 304, about 12% more. In exchange, 304 is the more ductile: elongation 55% versus 45% for 309S, and 309S is harder (165 HB vs 150 HB). 309S runs hotter in service (1,000°C vs 870°C continuous). On the shop floor, 304 sits in a lower cost tier (standard, $$) than 309S (premium, $$$).
304Choose it when the part is bent, formed or impact-loaded, or when cost is the deciding factor.
309SChoose it when strength drives the design, or when the part sees heat.
304 vs 309S: 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
Bulk 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, Vickers
Same in both: Shear Modulus 77 GPa11.2 Msi · Fatigue Strength (Endurance Limit) 250 MPa36.3 ksi
Physical
Density and transition temperatures.
Density
Same in both: 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 Conductivity
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 500 J/kg·K0.12 BTU/lb·°F · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.05 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Polishability
Same in both: Machinability Rating (AISI 1212 = 100 %) 45% · Brazeability / Solderability 65 / 100
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
Same in both: 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 | 304 | 309S |
|---|---|---|
| Casting & forging | Yes | — |
| Default condition | Annealed | Solution Annealed |
| Relative cost | $$ Standard | $$$ Premium |
| Min. machined wall | 0.8 mm | 0.8 mm |
| Best machined surface | Ra 1.6 µm | Ra 1.6 µm |
Both are offered for CNC machining and Sheet metal. Both take the same 32 finishes: AlCrN, AlTiN, Black Oxide, CVD Al2O3, CVD TiCN, CVD TiN, Cerakote, Chrome Plating, CrN, DLC, Electroless Nickel (EN), Electropolishing and 20 more.
304 vs 309S — frequently asked
Is 309S stronger than 304?
Yes. 309S has a typical yield strength of 280 MPa (40.6 ksi) against 250 MPa (36.3 ksi) for 304 — about 12% more. Tensile strength is 550 MPa (79.8 ksi) vs 585 MPa (84.8 ksi).
Which is cheaper, 304 or 309S?
304 is the lower-cost material: it sits in the standard tier ($$) while 309S is premium ($$$). 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, 304 or 309S?
304, by a small margin. Both rate fair for machinability — 45/100 against 38/100 for 309S; for welding the order is 304 first (excellent, 88/100) then 309S (very good, 80/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 304 and 309S 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.