ASTM A268 TP405 Ferritic Stainless Steel Tube with Low Chromium and High Aluminum, Non-air-hardening

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ASTM A268 TP405 Ferritic Stainless Steel Tube with Low Chromium and High Aluminum, Non-air-hardening

ASTM A268 TP405 (UNS S40500) ferritic stainless steel tube is a low-chromium ferritic stainless steel tubing. This grade belongs to the low-chromium series (11.5%–14.5% Cr) under the ASTM A268 specification, with carbon content controlled at ≤0.08% and aluminum content of 0.10%–0.30%.

The most distinctive characteristic of this material is non-air-hardening — it does not undergo appreciable hardening upon air cooling from elevated temperatures, a property that effectively retards the formation of hardening cracks caused by welding. TP405 offers practically the same corrosion and oxidation resistance as TP410, combined with excellent formability — it can be machined, drawn, spun and formed without difficulty using conventional techniques.

TP405 tubing is widely used for general corrosion-resisting and high-temperature service applications. Typical applications include heat exchangers in crude oil atmospheric and vacuum distillation units in refineries, heat exchangers, heaters and condensers in the oil and gas industry, pressure vessel linings, and steam turbine components. The material exhibits no embrittlement at service temperatures of 400–500°C, and offers immunity to stress corrosion cracking, resistance to sulfide corrosion, high heat transfer efficiency, and low thermal expansion coefficient.

Chemical & Mechanical Properties

 Mechanical Properties

Physical Properties

Ferromagnetism: TP405, as a ferritic stainless steel, exhibits ferromagnetic properties.

Embrittlement Risk upon Slow Cooling: High-chromium ferritic alloys are susceptible to embrittlement during slow cooling, necessitating careful control of processing parameters and heat treatment procedures.

Thermal Stability: The material does not develop embrittlement at operating temperatures of 400–500°C and demonstrates excellent long-term thermal stability up to approximately 649°C (1200°F).

Low Thermal Expansion Coefficient: The low coefficient of thermal expansion contributes to excellent dimensional stability under thermal cycling conditions, which is particularly beneficial for applications such as heat exchangers.

Heat Treatment Requirements

According to ASTM A268, the final heat treatment for TP405 steel tubes shall be annealing at a temperature of ≥ 650°C (1200°F). The specific solution annealing temperature range is 800–850°C (1470–1560°F).

The delivery condition is typically the annealed state (annealed).

Key Applications

Core Application: Refinery atmospheric and vacuum distillation unit heat exchangers

(owing to its immunity to stress corrosion cracking, resistance to sulfide corrosion, and high heat transfer efficiency. )

Oil and gas industry: heat exchangers, heaters, and condensers.

Pressure vessel linings

Steam turbine blades

Clad steel plates

Bearing machined components

Automotive exhaust systems

*TP405 is primarily used in applications where TP410 and TP430 are unsuitable due to their air‑hardening characteristics.