409L Stainless Steel (UNS S40910)
Ferritic (Ti-stabilized) · ASTM A240/A240M · Density 7.7 g/cm³
409L (UNS S40910) is an 11% chromium, titanium-stabilized ferritic stainless steel — the standard material of automotive exhaust systems. It offers roughly ten times the wet-corrosion life of carbon steel at modest cost, forms and welds easily, and tolerates exhaust-gas temperatures around 700 °C.
Chemical Composition (wt%)
| C | Mn | Si | Cr | Ni | Ti | P | S |
|---|---|---|---|---|---|---|---|
| ≤0.030 | ≤1.00 | ≤1.00 | 10.5–11.7 | ≤0.50 | 6×(C+N)–0.50 | ≤0.045 | ≤0.030 |
Single values are maximums unless a range is shown. Balance: Fe. Per ASTM A240/A240M.
Mechanical Properties
| Tensile strength | ≥380 MPa (55 ksi) |
|---|---|
| Yield strength (0.2%) | ≥170 MPa (25 ksi) |
| Elongation (50 mm) | ≥20% |
| Hardness | ≤179 HBW |
Room-temperature minimum values are summarized for annealed flat product under ASTM A240/A240M unless a condition is named in the property label; product form and thickness can change the requirement.
Physical Properties & Structure
| Density | 7.7 g/cm³ |
|---|---|
| Magnetic response | Magnetic because the room-temperature matrix is ferritic. |
| Microstructure | Ferritic (Ti-stabilized) |
Corrosion Resistance & Limits
- Ferritic grades resist chloride stress-corrosion cracking better than common austenitic grades, while pitting resistance still depends on chromium, molybdenum and exposure.
- Weld condition, section thickness, crevices, deposits and surface contamination can control service performance; validate the actual fabrication and environment.
Fabrication & Heat Treatment
| Welding | Control heat input, interpass temperature and joint design to limit grain growth and loss of toughness; stabilized grades improve but do not remove these controls. |
|---|---|
| Forming | Formability is useful in sheet gauges but lower than common austenitic grades, especially in heavy sections and severe draws. |
| Machining | Machining is generally straightforward with rigid tooling; avoid smearing, overheating and iron contamination of finished surfaces. |
| Heat treatment | Ferritic grades are not hardened by heat treatment. Annealing can restore ductility, but the temperature and cooling route must follow the product specification. |
Equivalent Grades
The closest international equivalents of 409L Stainless Steel are 1.4512 (X2CrTi12) in the EN system, SUH409L in the JIS system, 022Cr11Ti in the GB system.
These are common corresponding designations, not unconditional substitutes. Verify chemistry, mechanical properties, product standard, delivery condition, dimensions and project approval before changing designation.
| System | Designation |
|---|---|
| UNS | S40910 |
| EN | 1.4512 (X2CrTi12) |
| JIS | SUH409L |
| GB | 022Cr11Ti |
Reference Product Forms & Dimensional Ranges
Common reference product forms for 409l stainless steel: Coil / Strip, Sheet / Plate, Pipe / Tube.
| Finishes | No.1, 2B, 2D |
|---|---|
| Sheet / coil thickness | 0.4–3.0 mm |
| Common widths | 1000 / 1219 / 1500 mm |
Common surface and delivery options: No.1, 2B, BA or mechanically polished finish when supported by the product route; Annealed and pickled, descaled or polished tube finish as specified.
These published ranges are engineering references, not a live-stock or production-capability promise. Confirm the required product form, dimensions, condition, finish and supply route in the quotation.
Typical Applications
- Automotive exhaust pipes and mufflers
- Catalytic converter shells
- Heat shields
- Agricultural equipment panels
- Chimney and flue liners
Frequently Asked Questions
Will 409L stainless steel rust?
It can show light surface rust or a brown patina outdoors — with only ~11% chromium and no nickel it is not a cosmetic grade. Functionally the patina is superficial: structural life in exhaust and flue service far exceeds aluminized carbon steel, which is exactly the trade the grade was designed for.
What is the difference between 409 and 430 stainless steel?
430 carries more chromium (16–18% vs 10.5–11.7%), so it stays visibly brighter and resists staining better. 409L counters with titanium stabilization, which makes its welds tougher and immune to sensitization — one reason exhaust tube is 409L while appliance panels are 430.
What temperature can 409L handle?
Continuous exhaust-gas service to roughly 700 °C, with short excursions higher. For hot-end manifold parts running hotter, dual-stabilized ferritics such as 441 or 439 with more chromium are the usual upgrade path.
409L Compared With Other Grades
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.
Other stainless steel grades:
304304L316316L201321310S4104302205202301309S316Ti347904L4204394414442507303317L254 SMO440C17-4 PH2304
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