Stainless Steel ER409
UNS S40900
ER409 is a titanium-stabilized 11% chromium ferritic stainless bare wire (UNS S40900) that matches 409-type sheet used in exhaust fabrication.
Reference datasheet — ER409 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
ER409 tempers and conditions
ER409 is supplied in 2 conditions, soft to hard. AW is the default FabDigit quotes; the values on this page are for it.
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Post-weld heat treated | Choose when residual stress, HAZ hardness or toughness of thicker joints must be reduced before service or forming. | 270 | 440 | 28 | 150 HB | 3 % IACS |
AWDefault As-welded deposit | Standard condition for exhaust and thin-gauge fabrication: weld and use, with low heat input to limit grain growth. | 320 | 470 | 22 | 165 HB | — |
Supply forms, finishes and certifications
Ways ER409 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
WIRE-CD | Wire | Supply form |
What is ER409?
ER409 is a titanium-stabilized 11% chromium ferritic stainless bare wire (UNS S40900) that matches 409-type sheet used in exhaust fabrication. It is selected for thin-gauge exhaust and light corrosion-resistant assemblies where a ferritic, low-cost deposit is wanted instead of austenitic filler; supplied as cold-drawn spooled wire for GTAW and GMAW. Typical deposits give about 320 MPa yield, 470 MPa tensile, 22% elongation and 165 HB, with service to 675 °C. Corrosion resistance is limited (score 45) and the weld and HAZ coarsen at high heat input; ER409Cb offers better weld ductility, and 308L-type filler is used where austenitic ductility is required. ER409 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,480°C (2,696 °F). ER409 has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 470 MPa (68.2 ksi) — weaker than 60% of stainless steel grades. Elongation at break is 22% and the elastic modulus is 200 GPa (29 Msi).
What is ER409 used for?
- Automotive exhaust systems
- 409 stainless muffler and pipe welding
- Catalytic converter shells and cones
- Exhaust manifolds and downpipes
- Agricultural and heat-shield sheet assemblies
- Fabricated flue and vent components
Advantages
- Easy to machine — 58/100, better than 97% of stainless steel grades
- Low embodied carbon — 3.4 kg CO₂/kg, better than 91% 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
- High electrical conductivity — 2.9 % IACS, better than 87% of stainless steel grades
Limitations
- Hard to polish — 55/100, worse than 89% of stainless steel grades
- Needs corrosion protection — 45/100, worse than 85% of stainless steel grades
- Limited ductility — 22%, worse than 75% of stainless steel grades
ER409 properties
Typical room-temperature values for ER409-AW; bars are the position among stainless steel grades.
Physical3
ER409 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,480°C (2,696 °F).
Mechanical14
ER409 has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 470 MPa (68.2 ksi) — weaker than 60% of stainless steel grades. Elongation at break is 22% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
ER409 is rated for continuous service to 675°C (1,247 °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 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
ER409 conducts electricity at 2.9 % IACS, better than 87% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 85% of stainless steel grades.
Sustainability4
Producing a kilogram of ER409 takes about 45 MJ of energy and emits 3.4 kg of CO₂ — less than 91% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
ER409's machinability is good (58/100, better than 97% of stainless steel grades); weldability very good (75/100); formability good (55/100).
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. ER409 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with ER409
Is ER409 easy to machine?
Weld deposit machines like annealed 409 — gummy, use sharp carbide, positive rake, rigid setup and generous coolant; expect ~60 % of 1212 rates.
Can ER409 be welded?
GTAW/GMAW with 98Ar-2O₂ or Ar-He (short-arc for thin exhaust gauge); keep heat input and interpass low (<150 °C) to limit ferrite grain coarsening, use Ar backing and no preheat on thin sheet.
Can ER409 be formed, bent or molded?
Weldments in thin gauge can be bent and hydroformed, but the coarse-grained weld/HAZ shows lower ductility and possible roping — allow generous bend radii.
ER409 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 ER409 | ≤ 0.08 | 0.03 |
| Cr | 10.5 – 13.5 | 11.8 |
| Ni | ≤ 0.6 | 0.3 |
| Mn | ≤ 0.8 | 0.5 |
| Si | ≤ 0.8 | 0.5 |
| Ti10×C minimum, stabilizer | ≤ 1.5 | 0.5 |
| Cu | ≤ 0.75 | 0.1 |
| Moresidual | ≤ 0.5 | 0.05 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance |
What surface finishes work on ER409?
Passivate or pickle to restore the oxide; aluminized or ceramic exhaust coatings are common — do not anodize; polishing reveals weld grain contrast.
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 ER409 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S40900
How much does ER409 cost?
ER409 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.
ER409 — frequently asked
What is ER409 used for?
ER409 is typically used for automotive exhaust systems, 409 stainless muffler and pipe welding, catalytic converter shells and cones, exhaust manifolds and downpipes, agricultural and heat-shield sheet assemblies and fabricated flue and vent components. In short: matching filler for 409 exhaust; low-cost ferritic deposit; ti-stabilized to 675 °C.
What is the yield strength of ER409?
ER409 has a typical yield strength of 320 MPa (46.4 ksi) and a tensile strength of 470 MPa (68.2 ksi) — weaker than 60% of stainless steel grades. Strength varies by condition: see the 2 listed tempers.
Is ER409 easy to machine?
Reasonably — machinability is rated good (58/100, better than 97% of stainless steel grades). Weld deposit machines like annealed 409 — gummy, use sharp carbide, positive rake, rigid setup and generous coolant; expect ~60 % of 1212 rates.
Can ER409 be welded?
Yes — weldability is rated very good (75/100). GTAW/GMAW with 98Ar-2O₂ or Ar-He (short-arc for thin exhaust gauge); keep heat input and interpass low (<150 °C) to limit ferrite grain coarsening, use Ar backing and no preheat on thin sheet.
What surface finishes work on ER409?
Passivate or pickle to restore the oxide; aluminized or ceramic exhaust coatings are common — do not anodize; polishing reveals weld grain contrast.
Can ER409 be formed, bent or molded?
Weldments in thin gauge can be bent and hydroformed, but the coarse-grained weld/HAZ shows lower ductility and possible roping — allow generous bend radii.
What is the maximum service temperature of ER409?
ER409 is rated for continuous use to about 675°C (1,247 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between ER409-AW and ER409 PWHT?
AW is the default condition — standard condition for exhaust and thin-gauge fabrication: weld and use, with low heat input to limit grain growth. PWHT: choose when residual stress, HAZ hardness or toughness of thicker joints must be reduced before service or forming. Yield strength is 320 MPa in AW versus 270 MPa in PWHT.
How much does ER409 cost?
ER409 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)
- ASTM A240/A240M (Type 409 base metal) — ASTM International (2023)
- ASM Handbook Vol.6 — Welding, Brazing and Soldering (ferritic stainless weld metal) — ASM International (1993)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- Type 409 / 409Ni stainless sheet data — AK Steel / Cleveland-Cliffs (2019)
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.