ASTM A335 P9 Seamless Alloy Steel Pipe Boiler Tube
Dec 03, 2025
ASTM A335 P9 Alloy Steel Seamless Pipes Description
A335 P9 Alloy Seamless Pipe is primarily made of chromium-molybdenum steel, renowned for its exceptional high-temperature strength and superior creep resistance. At elevated temperatures, conventional steels tend to soften and lose load-bearing capacity. However, A335 P9 alloy, with the addition of appropriate chromium and molybdenum elements, effectively enhances thermal stability and long-term strength, maintaining excellent mechanical properties even at temperatures up to 600°C or higher. Additionally, this alloy offers good oxidation and corrosion resistance, ensuring long-term durability in harsh operating conditions without easy damage.
Chrome Moly Alloy A335/SA335 Seamless P9 Piping specification
A335 P9 Chemical Composition (Typical wt %)
| Element | Content (wt %) |
|---|---|
| Carbon (C) | 0.15 max |
| Manganese (Mn) | 0.30 - 0.60 |
| Phosphorus (P) | 0.025 max |
| Sulfur (S) | 0.025 max |
| Silicon (Si) | 0.25 - 1.00 |
| Chromium (Cr) | 8.00 - 10.00 |
| Molybdenum (Mo) | 0.90 - 1.10 |
Mechanical Properties of ASTM A335 P9 Pipes
| Property | Value |
|---|---|
| Tensile Strength | 60,000 psi (415 MPa) minimum |
| Yield Strength (0.2% offset) | 30,000 psi (205 MPa) minimum |
| Elongation in 2″ (50mm) | 30% minimum (longitudinal) |
| Hardness | Max 250 HBW / 265 HV / 25 HRC |
Production Process of SA335P9 Seamless Pipes
SA335P9 seamless pipes are manufactured through either hot-rolling or cold-drawing processes, with the following core steps:
Smelting & Continuous Casting:
Melted in electric or converter furnaces, refined in LF furnaces to control impurity content.
Cast into billets with slow cooling to avoid center segregation.
Piercing & Rolling:
Billets heated to ~1200°C, pierced into hollow tubes via skew rolling.
Hot-rolled for efficiency (lower wall precision) or cold-drawn for ±0.1mm precision.
Heat Treatment:
Normalized (e.g., 930°C) and tempered (e.g., 730°C) to refine grain structure and relieve stress.
Technical Challenges:
Microstructure Uniformity: Improper heat treatment may cause banded structures, leading to anisotropic mechanical properties.
Carbide Agglomeration: Additives like V/Nb mitigate long-term high-temperature performance degradation.
Test and Inspection
packaging and shipping
