ASTM A335 P9 Alloy Steel Serrated Finned Tubes For High Temperature Boiler Superheaters

Chemical Composition (%)

Mechanical Properties

ASTM A335 P9 (12Cr9Mo) is a 9%Cr - 1%Mo ferroalloy designed for high-temperature (up to 650°C) and high-pressure (up to 16 MPa) service. It is a premium base tube material for serrated finned tubes in boiler superheaters, preheaters, HRSGs, and spark plug heaters where extreme high temperatures, corrosion resistance, and oxidation resistance are critical.

Why Serrated Fin Tubes Are Used In High Temperature Boiler Superheaters

Serrated capillary tubes are the preferred choice for high-temperature boiler superheaters (typically 450-550°C, 3.8-16MPa) because they promote heat transfer, resist fouling, withstand thermal stress, and save space/cost better than conventional or solid capillary tubes.

Significantly increasing the heat transfer area, this type of finned tube increases the surface area by 3-10 times compared to ordinary tubes, which is crucial for low convection coefficients of fluid gases.The serrated notches continuously disrupt the static thermal boundary layer on the fin surface, which would normally provide insulation.The serrated structure generates strong local mixing and lateral flow between fins, enhancing turbulence intensity.In superheaters, flue gas side resistance plays a dominant role, and serrated fins directly overcome this bottleneck problem.

Superior anti-fouling and anti-ash deposition, the gaps between the serrated sections allow for side-flow gas cleaning, preventing and reducing the thermal resistance of dirt, and providing a longer service life.

The base tube uses standard ASTM A213/A335/SA192, is stable at 450-550°C with minimal creep. High-frequency resistance welding (HFRW) creates a metallic bond (98%+ integrity) that resists thermal cycling and fine delamination.

Some Main Applications of ASTM A335 P9 Alloy Steel Serrated Finned Tubes

Boiler Superheaters/Reheaters:P9 resists creep and high‑temperature oxidation

Economizers & Air Preheaters: Recover flue‑gas heat; serrated fins boost convection and reduce fouling

Waste‑to‑Energy Plants: P9’s Cr–Mo alloy provides sulfidation resistance

HRSG (Heat Recovery Steam Generators)

Fired Heaters & Furnaces: direct flame impingement, high sulfur/hydrogen environments.

Condensers & Reboilers: High‑temperature distillation (e.g., catalytic reforming, hydrocracking)