Stainless Steel ER409-AW (As-welded deposit)
Heat-treated state · default condition
UNS S40900
Standard condition for exhaust and thin-gauge fabrication: weld and use, with low heat input to limit grain growth.
Values for the AW condition
Other ER409 tempers and conditions
ER409 is listed in 2 conditions; see the grade overview at ER409.
- PWHT
- AW
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 |
AWDefaultThis page 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 | — |
What is ER409-AW?
ER409-AW is ER409 heat treated to AW — standard condition for exhaust and thin-gauge fabrication: weld and use, with low heat input to limit grain growth. ER409-AW 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). ER409-AW 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).
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-AW properties
Typical room-temperature values for ER409-AW; 11 are specific to this condition. Other listed values are ER409 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
ER409-AW 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-AW 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-AW 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-AW 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-AW 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-AW'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. Confirm any required mill or lot documentation when quoting.
Working with ER409-AW
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.
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.
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 | — |
ER409-AW — frequently asked
What is ER409-AW used for?
ER409-AW 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-AW?
ER409-AW 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-AW 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-AW 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-AW?
Passivate or pickle to restore the oxide; aluminized or ceramic exhaust coatings are common — do not anodize; polishing reveals weld grain contrast.
Can ER409-AW 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-AW?
ER409-AW 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.