Stainless Steel 409Cb
UNS S40940
409Cb (UNS S40940) is a niobium-stabilized 11% chromium ferritic stainless steel in which Nb replaces the titanium of standard 409 to raise high-temperature strength and suppress sensitization.
Reference datasheet — 409Cb 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 ANN condition
409Cb tempers and conditions
409Cb is supplied in 3 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard stocked condition for exhaust sheet, strip and welded tube — maximum ductility and formability. | 255 | 430 | 32 | 150 HB | 2.9 % IACS |
Temper Rolled / skin-passed | Choose for clip, bracket and clamp strip where slightly higher yield and flatness beat maximum ductility. | 380 | 480 | 16 | 175 HB | 2.9 % IACS |
Cold Worked 1/4 Hard | Higher-strength strip or cold-drawn tube for stiffness-driven parts; forming must be limited. | 450 | 550 | 9 | 16 HRC | 2.9 % IACS |
Supply forms, finishes and certifications
Ways 409Cb is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
Tube-AW | Welded tube, as-welded | Supply form |
2B | Cold rolled, annealed, pickled and skin passed | Surface finish |
2D | Cold rolled, annealed and pickled | Surface finish |
BA | Bright annealed | Surface finish |
HRAP | Hot Rolled Annealed & Pickled | Surface finish |
What is 409Cb?
409Cb (UNS S40940) is a niobium-stabilized 11% chromium ferritic stainless steel in which Nb replaces the titanium of standard 409 to raise high-temperature strength and suppress sensitization. It is used mainly as sheet, strip and welded tube for automotive exhaust hardware, with annealed properties of 255 MPa yield, 430 MPa tensile, 32% elongation and 150 HB (78 HRB) and service to 760 °C. It welds and forms well (formability 72) but is not a wet-corrosion grade — surface rusting occurs in road salt — and it cannot be hardened by heat treatment. 439 or 441 are the usual step up for hotter or wetter exhaust positions. 409Cb has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,450°C (2,642 °F). 409Cb has a yield strength of 255 MPa (37 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 87% of stainless steel grades. Elongation at break is 32% and the elastic modulus is 200 GPa (29 Msi).
What is 409Cb used for?
- exhaust manifolds
- catalytic converter housings
- underbody automotive parts
Advantages
- Low embodied carbon — 2.7 kg CO₂/kg, better than 99% of stainless steel grades
- Easy to machine — 55/100, better than 94% 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
- Readily welded — 85/100, better than 87% of stainless steel grades
Limitations
- Hard to polish — 50/100, worse than 93% of stainless steel grades
- Low strength — 255 MPa (37 ksi), worse than 87% of stainless steel grades
- Needs corrosion protection — 45/100, worse than 85% of stainless steel grades
409Cb properties
Typical room-temperature values for 409Cb-ANN; bars are the position among stainless steel grades.
Physical3
409Cb has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,450°C (2,642 °F).
Mechanical15
409Cb has a yield strength of 255 MPa (37 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 87% of stainless steel grades. Elongation at break is 32% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
409Cb is rated for continuous service to 760°C (1,400 °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
409Cb 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 409Cb takes about 40 MJ of energy and emits 2.7 kg of CO₂ — less than 97% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
409Cb's machinability is good (55/100, better than 94% of stainless steel grades); weldability excellent (85/100); formability very good (72/100).
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. 409Cb is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 409Cb
Is 409Cb easy to machine?
Machines like a soft low-carbon stainless — use sharp, positive-rake tools, rigid setups and generous coolant to avoid built-up edge and work-hardened skin; roughly 65 % of B1112 speed.
Can 409Cb be welded?
Excellent weldability by GTAW/GMAW/laser/HF resistance welding; Nb stabilization prevents weld-decay and keeps HAZ ductility, but keep heat input low to limit grain coarsening and use 409Cb/430Nb or 309L filler.
Can 409Cb be formed, bent or molded?
Good cold formability for stamping, roll forming and tube bending; watch for ridging/roping on deep draws and allow more springback than austenitic grades.
409Cb 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 |
|---|---|---|
| CC+N ≤ 0.045 typical mill practice | ≤ 0.03 | 0.02 |
| Mn | ≤ 1 | 0.4 |
| Si | ≤ 1 | 0.45 |
| P | ≤ 0.04 | 0.03 |
| S | ≤ 0.02 | 0 |
| Cr | 10.5 – 11.7 | 11.2 |
| Ni | ≤ 0.5 | 0.25 |
| N | ≤ 0.03 | 0.02 |
| NbNb ≥ 10×C (Cb stabilization); some mills use Nb ≥ 0.30 | 0.17 – 0.75 | 0.35 |
| Tiresidual only in the pure Nb-stabilized version | ≤ 0.15 | 0.02 |
| Fe | balance |
What surface finishes work on 409Cb?
Not anodizable; normally supplied as mill 2B/No.1 finish, and can be aluminized, painted with high-temperature coatings or lightly polished for non-decorative service.
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 409Cb in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S40940
How much does 409Cb cost?
409Cb is a budget-cost stainless steel ($), cheaper than about 90% 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.
409Cb — frequently asked
What is 409Cb used for?
409Cb is typically used for exhaust manifolds, catalytic converter housings and underbody automotive parts. In short: nb-stabilized exhaust ferritic; weldable to 760 °C; nickel-free, low cost.
What is the yield strength of 409Cb?
409Cb has a typical yield strength of 255 MPa (37 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 87% of stainless steel grades. Strength varies by condition: see the 3 listed tempers.
Is 409Cb easy to machine?
Reasonably — machinability is rated good (55/100, better than 94% of stainless steel grades). Machines like a soft low-carbon stainless — use sharp, positive-rake tools, rigid setups and generous coolant to avoid built-up edge and work-hardened skin; roughly 65 % of B1112 speed.
Can 409Cb be welded?
Yes — weldability is rated excellent (85/100). Excellent weldability by GTAW/GMAW/laser/HF resistance welding; Nb stabilization prevents weld-decay and keeps HAZ ductility, but keep heat input low to limit grain coarsening and use 409Cb/430Nb or 309L filler.
What surface finishes work on 409Cb?
Not anodizable; normally supplied as mill 2B/No.1 finish, and can be aluminized, painted with high-temperature coatings or lightly polished for non-decorative service.
Can 409Cb be formed, bent or molded?
Good cold formability for stamping, roll forming and tube bending; watch for ridging/roping on deep draws and allow more springback than austenitic grades.
What is the maximum service temperature of 409Cb?
409Cb is rated for continuous use to about 760°C (1,400 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 409Cb-ANN and 409Cb-CW14?
ANN is the default condition — standard stocked condition for exhaust sheet, strip and welded tube — maximum ductility and formability. CW14: higher-strength strip or cold-drawn tube for stiffness-driven parts; forming must be limited. Yield strength is 255 MPa in ANN versus 450 MPa in CW14.
How much does 409Cb cost?
409Cb is a budget-cost stainless steel ($), cheaper than about 90% 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
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip (S40940) — ASTM International (2023)
- ASTM A268/A268M — Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing — ASTM International (2022)
- SAE J405 / ASTM A959 — Stainless steel designations (UNS S40940) — SAE / ASTM (2020)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- 409Cb / 11 Cr Nb-stabilized ferritic stainless product data — AK Steel / Cleveland-Cliffs, Outokumpu (2021)
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.