ASTM A335 P22 Alloy Steel Seamless Pipe High-temperature Ferritic Alloy Steel Pipe Boiler

ASTM A335 P22 / UNS K21590 Alloy Steel Seamless Pipe 2.25Cr-1Mo Steel Pipe for High-temperature Service
 
 

YUHONG Group supplies ASTM A335 / ASME SA335 alloy steel pipes worldwide, with our product portfolio covering the most popular ASTM A335 materials, including P5, P9, P11, P22, P91, and P92 ... ASTM A335 P22 is a life-limited consumable item. It is a seamless ferritic pipe, heat-treated (Normalized + Tempered), engineered to deliver reliable creep-rupture strength up to 550°C, specifically for superheaters, reheaters, and high-pressure steam headers. It is a pipe that must be ordered with hardness limits, grain-size requirements, and impact-testing added to the PO. If you buy it without these 'Supplementary Requirements,' the official ASTM definition gives the mill permission to ship you a pipe that technically passes chemistry but may fail in 5 years instead of 20.

ASTM A335 P22 Pipe Specification

Chemical composition % of ASTM A335 P22 Alloy Steel Seamless Pipe High-temperature Ferritic Alloy Steel Pipe

Mechanical properties of ASTM A335 P22 Alloy Steel Seamless Pipe High-temperature Ferritic Alloy Steel Pipe

Hydrogen Service Limits (The Nelson Curve Nuance)

P22 is widely used in hydrogen reformer boilers. Websites mention "resistant to hydrogen attack," but they rarely spell out the Nelson Curve partial pressure limit.
The hidden fact: For P22, the safe operating limit is roughly 3.0 MPa (435 psi) hydrogen partial pressure at 540°C. However, if your feedwater carries chlorides that hydrolyze to HCl, the hydrogen permeation rate doubles. Even more obscure: The mill's deoxidation practice (Silicon vs. Aluminum killed) drastically affects this. Aluminum-killed P22 has finer, more stable AlN precipitates that pin grain boundaries, significantly improving the Nelson Curve threshold—yet standard P22 orders do not specify Al content unless you add a supplementary requirement (S2/S3) to the purchase order.

Applications

This grade is the workhorse of conventional thermal power plants and industrial boilers. Specific uses include:

• Superheaters & Reheaters: Pipes carrying superheated steam from the boiler drum to the turbine.

• Water Wall Tubes: Furnace walls where radiant heat is absorbed.

• Header Pipes: Main steam headers and feedwater headers operating in the creep range.

• Heat Exchangers: In petrochemical plants handling high-pressure, high-temperature hydrocarbons.

• Fossil Fuel Power Plants: Sub-critical and super-critical boiler piping systems.

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