What is the composition of SA 335 P11 Chrome Moly Pipe
Jul 02, 2025
SA335 P11 is a chromium-molybdenum alloy seamless steel pipe, and its core definition and chemical composition specifications are as follows:
1. Material nature and positioning
Standard affiliation: Ferritic heat-resistant steel in the American ASTM A335/A335M standard, belonging to the chromium-molybdenum alloy steel system, designed for high-temperature pressure equipment.
Core characteristics: Through chromium (Cr)-molybdenum (Mo) synergistic strengthening, it has both oxidation resistance and medium and high temperature strength, suitable for steam, oil and gas transportation scenarios ≤540℃.
Domestic equivalent grade: Similar to the national standard 15CrMo composition (nominal composition is 1.25Cr-0.5Mo).
2.Chemical composition (wt%)
| Element | Content Range | Functions |
|---|---|---|
| C | 0.05–0.15% | Balance between strength and weldability |
| Cr | 1.00–1.50% | Forming dense Cr₂O₃ oxide film to resist high temperature corrosion (nominal value 1.25%) |
| Mo | 0.44–0.65% | Solid solution strengthening, improving creep resistance (nominal value 0.5%) |
| Element | Content Range | Functions |
|---|---|---|
| Mn | 0.30–0.60% | Improve hot workability, desulfurization |
| Si | 0.50–1.00% | Deoxidizer, enhance high temperature oxidation resistance |
| P | ≤0.025% | Strictly control the risk of cold brittleness |
| S | ≤0.025% | Suppresses thermal crack sensitivity |
SA335 P11 alloy pipe uses 1.25%Cr-0.5%Mo as the core alloy system. Through precise composition design, it achieves a balance of strength, oxidation resistance, and weldability under working conditions below 540°C. It is a key piping material for petrochemical and subcritical power plant boilers.
