Seamless Ferritic and Austenitic Tubes

Seamless ferritic and austenitic alloy steel tubes are critical pressure-bearing components widely used in boilers, superheaters, heat exchangers, and high-temperature power systems. Manufactured in accordance with ASTM A213 / ASME SA-213 standards, these seamless tubes are engineered to deliver outstanding performance under high temperature, high pressure, and corrosive operating environments.

Thanks to their optimized alloy design and strict dimensional control, ferritic and austenitic seamless tubes ensure long service life, thermal stability, and reliable mechanical strength in demanding industrial applications.

1. Applicable Standards

All tubes are produced in compliance with:

• ASTM A213 / A213M

• ASME SA-213 / SA-213M

These standards define chemical composition, mechanical properties, dimensional tolerances, and inspection requirements for seamless alloy steel tubes used in elevated-temperature services.

2. Chemical Composition Overview

Different grades are designed to meet specific temperature and pressure requirements:

• T2 / T5: Low-alloy Cr-Mo steels offering balanced strength and weldability

• T11 / T12: Chromium-molybdenum alloy steels with improved oxidation resistance

• T36: High-strength microalloy steel with Ti, Zr, and controlled nitrogen

• T91: Advanced 9Cr-1Mo-V alloy for ultra-high temperature and creep resistance

The addition of chromium (Cr) improves oxidation and corrosion resistance, while molybdenum (Mo) enhances high-temperature strength and creep performance. Elements such as vanadium, titanium, and nitrogen further refine grain structure and mechanical stability in advanced grades like T91 and T36.

3. Mechanical Properties

Seamless alloy steel tubes exhibit excellent mechanical performance suitable for long-term high-temperature operation:

• Yield Strength: 205–460 MPa (depending on grade)

• Tensile Strength: 415–660 MPa

• Elongation: Up to 30% for improved toughness

• Hardness Control: Strict limits to ensure machinability and fatigue resistance

Grades such as T91 and T36 are specifically designed for supercritical and ultra-supercritical boilers, where creep resistance and structural stability are essential.

4. Dimensional Accuracy & Tolerances

Precision dimensional control is essential for heat transfer efficiency and pressure integrity.

Outer Diameter Tolerances:

• OD 10.6–101.6 mm: +0.4 / −0.8 mm

• OD 101.6–190.5 mm: +0.4 / −1.2 mm

• OD 190.5–228.6 mm: +0.4 / −1.6 mm

Wall Thickness Tolerances:

• 2.4–3.8 mm: 0 to +35%

• 3.8–4.6 mm: 0 to +33%

• ≥ 4.6 mm: 0 to +28%

These tolerances ensure optimal fit, reliable pressure containment, and consistent heat transfer performance.

5. Typical Applications

Seamless ferritic and austenitic alloy steel tubes are widely used in:

• Power plant boilers and superheaters

• Heat exchangers and condensers

• High-pressure steam pipelines

• Petrochemical and refinery equipment

• Energy and thermal processing systems

Their combination of high-temperature resistance, mechanical strength, and corrosion resistance makes them indispensable in critical thermal systems.

Conclusion

Seamless ferritic and austenitic alloy steel tubes manufactured to ASTM A213 / ASME SA-213 standards provide a proven solution for high-pressure, high-temperature applications. With a wide range of grades—from T2 to advanced T91—these tubes meet the evolving demands of modern power generation and industrial heat exchange systems.