Stainless Steel ER409 PWHT
Heat-treated state
UNS S40900
PWHT = post-weld heat treated
Choose when residual stress, HAZ hardness or toughness of thicker joints must be reduced before service or forming.
Values for the PWHT 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 |
|---|---|---|---|---|---|---|
PWHTThis page 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 | — |
What is ER409 PWHT?
ER409 PWHT is ER409 heat treated to PWHT — choose when residual stress, HAZ hardness or toughness of thicker joints must be reduced before service or forming. ER409 PWHT has a yield strength of 270 MPa (39.2 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 79% of stainless steel grades. Elongation at break is 28% and the elastic modulus is 200 GPa (29 Msi). ER409 PWHT 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). AW is the default condition FabDigit quotes; PWHT is available on request or by drawing note.
Advantages
- Easy to machine — 62/100, better than 98% of stainless steel grades
- Conducts heat well — 25.2 W/m·K (14.6 BTU/hr·ft·°F), better than 95% of stainless steel grades
- High electrical conductivity — 3 % IACS, better than 95% of stainless steel grades
- Low embodied carbon — 3.4 kg CO₂/kg, better than 91% of stainless steel grades
Limitations
- Hard to polish — 55/100, worse than 89% of stainless steel grades
- Needs corrosion protection — 47/100, worse than 81% of stainless steel grades
- Low strength — 270 MPa (39.2 ksi), worse than 79% of stainless steel grades
ER409 PWHT properties
Typical room-temperature values for ER409 PWHT; 22 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 PWHT 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 PWHT has a yield strength of 270 MPa (39.2 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 79% of stainless steel grades. Elongation at break is 28% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
ER409 PWHT is rated for continuous service to 675°C (1,247 °F). It conducts heat at 25.2 W/m·K (14.6 BTU/hr·ft·°F), better than 95% of stainless steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
ER409 PWHT conducts electricity at 3 % IACS, better than 95% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (47/100), worse than 81% of stainless steel grades.
Sustainability4
Producing a kilogram of ER409 PWHT 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 PWHT's machinability is good (62/100, better than 98% of stainless steel grades); weldability very good (75/100); formability good (65/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ER409 PWHT
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 PWHT — frequently asked
What is ER409 PWHT used for?
ER409 PWHT 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 PWHT?
ER409 PWHT has a typical yield strength of 270 MPa (39.2 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 79% of stainless steel grades. Strength varies by condition: see the 2 listed tempers.
Is ER409 PWHT easy to machine?
Reasonably — machinability is rated good (62/100, better than 98% 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 PWHT 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 PWHT?
Passivate or pickle to restore the oxide; aluminized or ceramic exhaust coatings are common — do not anodize; polishing reveals weld grain contrast.
Can ER409 PWHT 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 PWHT?
ER409 PWHT 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.