Grade 409
Ferritic stainless · AISI 409 / SAE J405, UNS S40900, EN 1.4512
Type 409 Ferritic Stainless Steel (Automotive Exhaust), ferritic stainless steel.
Data sheet
| Designations | AISI 409 / SAE J405 · UNS S40900 · EN 1.4512 (X2CrTi12) |
|---|---|
| Standards | ASTM A240, EN 10088-2 |
Metallurgy
Reference data for Type 409 Ferritic Stainless Steel (Automotive Exhaust), against ASTM A240, EN 10088-2.
Elemental composition
X2CrTi12 to 1.4512
- Chromium 11,13%10,50–11,75%
- Nickel 0,25%max 0,50%
- Carbon 0,030%max 0,080%
- Other additions 1,38%Ti, Mn, Si, P, S
- Iron 87,22%Balance
Proportions use the normalised midpoint of each specified range. The midpoint is a derived figure, not something the standard states: read the table for what is actually specified.
Performance profile
Comparative scores out of ten, for weighing one grade against another
These are relative ratings, not measured properties, and they carry no units. Use them to narrow a shortlist, then work from the specified values.
Composition as specified
| Element | Specified | Nominal |
|---|---|---|
| Iron Fe | Balance | 87,22% |
| Carbon C | max 0,080%cap | 0,030% |
| Chromium Cr | 10,50–11,75% | 11,13% |
| Nickel Ni | max 0,50%cap | 0,25% |
| Titanium Ti | 0,18–0,75% | 0,35% |
| Manganese Mn | max 1,00%cap | 0,50% |
| Silicon Si | max 1,00%cap | 0,50% |
| Phosphorus P | max 0,040%cap | 0,020% |
| Sulphur S | max 0,020%cap | 0,010% |
A cap is a ceiling, not a quantity: a heat may contain far less. The nominal column is the midpoint of each range, used for the chart's proportions only.
Mechanical and physical properties
| Property | Value |
|---|---|
| Tensile strength, ultimate | 430 MPa62,4 ksi |
| Yield strength, 0,2% offset | 230 MPa33,4 ksi |
| Elongation at break | 25% |
| Hardness | 140 HBW / 75 HRB |
| Modulus of elasticity | 200 GPa29 Mpsi |
| Density | 7,7 g/cm³0,28 lb/in³ |
| Thermal conductivity | 25,8 W/(m·K)178,9 BTU·in/(hr·ft²·°F) |
| Thermal expansion | 11 µm/(m·K)6,1 µin/(in·°F) |
Test condition not yet confirmed. These figures are typical values for the grade; the condition a bar was supplied in changes them materially, so ask us for the mill certificate before designing to a number.
Pitting resistance
PREN 11,13
Cr + 3,3 Mo + 16 N, across the full specified composition
- Freshwater0–20
- Brackish20–32
- Seawater32–40
- Extreme offshoreover 40
A standard states its elements as ranges, so a grade has a window rather than a single score. The bar is that window; the tick is the midpoint.
Corrosion and fabrication
Chloride and marine service
Low resistance; rusts and pits readily in marine atmosphere; not suitable for cosmetic architectural uses.
Acidic and chemical media
Resistant to atmospheric corrosion and automotive exhaust gas condensate (sulfuric/carbonic condensates).
Sensitisation and thermal behaviour
Titanium stabilized; prevents chromium depletion in the heat-affected zone during exhaust cycling.
Welding
Fair to Good; low carbon/stabilized chemistry prevents martensite formation, but grain growth in HAZ reduces toughness.
Machining and cold forming
Machinability index 60% relative to AISI 1212. Moderate; good bending and roll forming, but lower elongation and drawability than 304.
Where it is used
- Automotive exhaust pipes, mufflers, and catalytic converter shells
- Agricultural fertilizer spreaders and grain elevators
- Home furnace heat exchangers
- Culverts and bus structural framing
Automotive · Agriculture · HVAC · Heavy Transport
Performance scores in full
The same six scores the profile plots, as numbers.
| Property | 409 |
|---|---|
| Corrosion resistance | 5.2 / 10 |
| Weldability | 7.5 / 10 |
| High-temperature resistance | 6.5 / 10 |
| Tensile strength | 5 / 10 |
| Cold formability | 7 / 10 |
| Machinability | 6.5 / 10 |
This page is guidance for selecting a grade, not a specification. Design to the governing standard and the mill certificate for the heat you are supplied.
The specifications and data on this site are provided for general information only. Verify any real-world project with a qualified metallurgist before relying on these figures. We take no responsibility for the use and application of this information.