ASTM A335 P23seamless ferritic alloy-steel pipe designed for high-temperature service. The "P23" designation refers to its specific chemical composition, which is based on a modified 2.25% Chromium steel, optimized for improved weldability and strength.
It is the modern, superior successor to the older T22/P22 grade and is a key material for advanced ultra-supercritical (USC) power plants.
High-Temperature Strength: Designed to maintain excellent tensile and creep strength (resistance to deformation under long-term stress and heat) at temperatures typically up to about 1050℃F (565℃).
One of its primary advantages over older grades like P22. P23 has lower carbon content and added elements like Vanadium and Tungsten, which reduce or eliminate the need for pre-heat and post-weld heat treatment (PWHT) in many cases, simplifying construction and repair.
The alloying elements help stabilize the microstructure during long-term exposure to high temperatures, preventing the formation of brittle phases and maintaining ductility.
The chromium content provides adequate resistance to oxidation (scaling) and certain types of corrosion in high-temperature environments.
The chemical composition (in weight percentage) is a key factor in its performance. The following is a standard range per ASTM A335:
| 0.04 - 0.10 | |
| 0.10 - 0.60 | |
| 0.030 max | |
| 0.010 max | |
| 0.50 max | |
| 1.90 - 2.60 | |
| 0.05 - 0.30 | |
| 0.20 - 0.30 | |
| 1.45 - 1.75 | |
| 0.0005 - 0.0060 | |
| 0.015 max | |
| 0.030 max | |
| 0.02 - 0.08 |
The low carbon, specific amounts of V, W, and the addition of Boron are what differentiate P23 and give it its superior properties.
| 510 MPa (74 ksi) min | |
| 400 MPa (58 ksi) min | |
| 20% min (on a standard 2-inch gauge length) |
A335 P23 pipes are used in critical high-temperature and high-pressure sections of industrial plants:
coal-fired power stations, especially in advanced ultra-supercritical (USC) units.
Heater tubes, heat exchangers, and transfer lines in refineries and chemical plants where high-temperature resistance is required.
For both high-pressure and low-pressure boiler tubing.
| A335 P23 | A335 P22 | A335 P91 | |
|---|---|---|---|
| ~2.25% Cr, W, V, B | ~2.25% Cr, 1% Mo | 9% Cr, 1% Mo, V, Nb | |
| Low (0.04-0.10%) | Higher (0.05-0.15%) | Medium (0.08-0.12%) | |
| Requires strict pre/post-heat | Requires very strict pre/post-heat | ||
| Temp. Strength | Good (up to ~565℃) | Lower than P23 | (up to ~600℃) |
| Replacing P22, new USC plants | High-temperature sections of USC plants |
ASTM A335 / A335M - Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service.
P23 pipes are required to be supplied in the condition to achieve the desired microstructure and mechanical properties.
A335 P23 Seamless Steel Pipe is a high-performance, cost-effective alloy steel solution for demanding high-temperature applications. Its superior weldability and good strength make it a preferred choice for modern, efficient power generation systems, often serving as a direct upgrade from the older P22 grade.
When sourcing this material, it is crucial to ensure the mill provides the proper ASTM A335 certification and that the pipe is marked with the grade "P23" for traceability.
