Key Feature

The Steam-Turbine Martensitic Stainless Steel Pipe. Optimized chemistry for high-temperature strength, oxidation resistance, and reliable performance in steam and elevated temperature piping services.

The traditional material choice for steam turbine piping and critical power generation components.

Common Designations

UNS S40300
AISI 403
ASTM A268 TP403 (Seamless Ferritic/Martensitic Pipe)
EN 1.4000, X6Cr13
JIS SUS403
AMS 5614 (Aerospace)

ASTM A268 is the primary specification for general service martensitic stainless steel pipe.

Chemical Composition (Typical wt.%)

C: 0.08 - 0.15
Cr: 11.5 - 13.0
Mn: ≤ 1.00
Si: 0.15 - 0.35P: ≤ 0.040
S: ≤ 0.030

Lower silicon than 410 (0.15-0.35% vs ≤1.00%) improves high-temperature properties and reduces scaling.

Mechanical Properties (Annealed)

Tensile Strength: ≥ 480 MPa
Yield Strength: ≥ 275 MPa
Elongation: ≥ 20%
Hardness: ≤ 217 HB

Moderate properties in annealed condition; designed for enhancement through heat treatment.

Mechanical Properties (Hardened & Tempered)

Tensile Strength: Up to 1300 MPa
Yield Strength: Up to 1100 MPa
Hardness: Up to 42 HRC
Elongation: 10-15%
Impact Toughness: Good

High strength achievable through proper heat treatment; suitable for dynamic loading in piping.

Elevated Temperature Properties

Continuous Service: Up to 700°C
Intermittent Service: Up to 750°C
Creep Strength: Good up to 600°C
Oxidation Resistance: Good up to 650°C

Specifically designed for steam turbine applications (typically 300-600°C).

Physical Properties

Density: 7.70 g/cm³
Melting Range: 1480 - 1530 °C
Thermal Expansion: 10.8 × 10⁻⁶/K (20-400°C)
Thermal Conductivity: 24.9 W/m·K (100°C)
Strongly magnetic

Lower thermal expansion than austenitic grades; beneficial for thermal cycling applications.

Corrosion Resistance

Moderate resistance to atmospheric corrosion, steam, and mild chemicals. Better than carbon steels but inferior to austenitic stainless steels.

Suitable for steam, condensate, and mildly corrosive elevated temperature environments.

Welding Characteristics

Requires pre-heat (200-300°C) and post-weld heat treatment
Possible cracking if not properly handled
Matching filler metals required
Post-weld annealing recommended

More challenging to weld than austenitic grades; requires specialized procedures for piping.

Pressure Ratings

Schedule 40/80: Standard pressure ratings
Heat treated versions have different ratings
ASME B31.1 for power piping applications

Pressure ratings depend on heat treatment condition; particularly suitable for steam service.

Key Standards

ASTM A268 TP403: General Service Pipe
ASTM A731/A731M: Seamless Pipe
AMS 5614 (Aerospace)
EN 10216-5: Seamless Pressure Tubes
ASME SA268: Code Construction

Available in various hardness conditions: annealed, hardened & tempered.

Common Applications

• Steam Turbine Systems: Steam piping, bypass lines, turbine bypass systems
• Power Generation: Feedwater heater tubes, boiler components, steam extraction lines
• Aerospace: Compressor bleed air piping, engine components
• Industrial Equipment: High-temperature steam piping, process steam lines
• Oil & Gas: Steam injection piping, thermal recovery systems
• Mechanical Components: Pump shafts, valve stems in piping systems
• Fastener Systems: High-temperature bolting for piping flanges

Specifically developed for and primarily used in steam and high-temperature piping applications.