Alloy Steel A335 P11 Pipe
High Performance Alloy Steel Piping
ASTM A335 P11, widely known as "1-1/4 Chrome" pipe, is a standard grade for the power industry and petrochemical plants. The addition of Chromium and Molybdenum provides superior creep strength and resistance to graphitization compared to standard carbon steel. It is specifically designed for high-temperature service where the environment requires high structural stability under thermal stress, making it the primary choice for main steam lines and reheat piping in modern boilers.
Technical Specifications
| Feature | Details |
|---|---|
| Standards | ASTM A335 / ASME SA335 |
| Grade | P11 (1.25% Cr, 0.5% Mo) |
| Size Range | 1/2" NB to 36" NB |
| Schedules | SCH 40, SCH 80, SCH 160, SCH XXS, STD, XS |
| Manufacturing | Seamless (Hot Finished or Cold Drawn) |
| Heat Treatment | Full or Isothermal Anneal, Normalized & Tempered |
Mechanical Properties
| Property | Value (Min) |
|---|---|
| Yield Strength (0.2% Offset) | 205 MPa (30,000 psi) |
| Tensile Strength | 415 MPa (60,000 psi) |
| Elongation | 30% |
| Hardness (Brinell) | Max 163 HBW |
Chemical Composition (%)
| Element | A335 P11 Percentage |
|---|---|
| Carbon (C) | 0.05 - 0.15 |
| Chromium (Cr) | 1.00 - 1.50 |
| Molybdenum (Mo) | 0.44 - 0.65 |
| Manganese (Mn) | 0.30 - 0.60 |
| Silicon (Si) | 0.50 - 1.00 |
| Phosphorus (P) | 0.025 max |
| Sulphur (S) | 0.025 max |
Features and Benefits of Alloy Steel P11 Pipe
- Exceptional creep-rupture strength for service temperatures up to 550°C
- High resistance to hydrogen attack and graphitization in steam systems
- Enhanced thermal stability reducing the risk of brittle fracture over time
- Versatile mechanical properties suitable for both high-pressure and high-heat cycles
- Cost-effective alternative to high-chrome grades for moderate thermal service
- Seamless manufacturing ensures structural uniformity and high pressure-bearing capacity
- Superior weldability compared to higher chromium ferritic alloys
- Reliable performance in thermal cycling environments found in utility boilers
Applications & Uses
Main Steam
Primary choice for main steam and hot reheat lines in thermal power plants.
Process Piping
Widely used in high-temperature refineries and hydrocarbon processing units.
Boiler Headers
Applied in superheater tubes and high-pressure steam headers in power stations.