Key Feature

The Economical Titanium-Stabilized Ferritic Stainless Steel Pipe. Lower chromium content and titanium stabilization provide cost-effective corrosion resistance for automotive and moderate temperature piping applications.

The most economical stainless steel pipe for automotive exhaust systems and similar applications.

Common Designations

UNS S40900
AISI 409
ASTM A268 TP409 (Seamless Ferritic Pipe)
ASTM A554 (Welded Mechanical Tubing)
EN 1.4512, X6CrTi12
JIS SUS409
SAE J409

ASTM A268 is the primary specification for ferritic stainless steel pressure pipe.

Chemical Composition (Typical wt.%)

C: ≤ 0.08
Cr: 10.5 - 11.7Ti: ≥ 6×C (min 0.15%)Mn: ≤ 1.00
Si: ≤ 1.00
P: ≤ 0.045
S: ≤ 0.030

Lower chromium than 430/304; titanium stabilization prevents sensitization.

Mechanical Properties

Tensile Strength: ≥ 380 MPa
Yield Strength: ≥ 205 MPa
Elongation: ≥ 20%
Hardness: ≤ 183 HB

Adequate strength for most automotive and industrial piping applications.

Physical Properties

Density: 7.70 g/cm³
Melting Range: 1425 - 1510 °C
Thermal Expansion: 10.8 × 10⁻⁶/K (20-400°C)
Thermal Conductivity: 25.0 W/m·K (100°C)
Strongly magnetic

Low thermal expansion similar to carbon steel; beneficial for exhaust systems.

Corrosion Resistance

Moderate resistance to atmospheric corrosion, exhaust gases, and mild chemicals. Not suitable for marine or severe chemical environments.

Adequate for automotive exhaust and many industrial applications; inferior to 304/430.

Welding Characteristics

Good weldability with proper techniques
No post-weld heat treatment requiredTitanium prevents sensitizationMatching filler metals recommended

Suitable for most welding methods; maintains corrosion resistance in weld zone.

Pressure Ratings

Schedule 10/40: Standard piping
Limited to moderate pressuresNot for high-pressure service

Generally used for low-pressure applications; verify with manufacturer for specific ratings.

Temperature Limits

Continuous Service: Up to 700°C
Intermittent Service: Up to 815°C
Minimum Service: -30°C
Avoid: 475-900°C (embrittlement)

Suitable for exhaust temperatures typically encountered in automotive applications.

Key Standards

ASTM A268 TP409: Seamless Ferritic Pipe
ASTM A554: Welded Mechanical Tubing
ASTM A791: Welded Ferritic Pipe
EN 10216-5: Seamless Pressure Tubes
JIS G3463: Stainless Steel Pipe
SAE J409: Automotive Standards

Specifically referenced in automotive industry standards.

Common Applications

• Automotive Exhaust Systems: Muffler piping, catalytic converter housings, tailpipes, exhaust manifolds
• Industrial Exhaust: Chimney liners, exhaust stacks, pollution control ducting
• Heat Exchangers: Low-cost heat exchanger tubes, automotive radiator headers
• Agricultural Equipment: Structural piping, exhaust systems, equipment frames
• Construction: Ventilation ducting, architectural trim (non-coastal)
• Containers: Chemical tanks (mild service), storage container frames
• Furniture: Outdoor furniture frames, structural pipe components

Specifically designed for cost-sensitive piping applications requiring better corrosion resistance than carbon steel.