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Products Description
ASTM A213 T91 Tubes represent a significant advancement in alloy steel technology, specifically classified as a Creep Strength Enhanced Ferritic (CSEF) steel.
Designated as UNS K90901 Tubes, this grade is a sophisticated 9% Chromium, 1% Molybdenum alloy, meticulously modified with additions of Vanadium, Niobium, and Nitrogen. Often referred to as Chrome-Moly T91 Tubes, its unique micro-alloying and controlled heat treatment result in a tempered martensitic microstructure, delivering exceptional high-temperature strength, creep resistance, and improved fatigue life compared to conventional Cr-Mo steels.
The primary advantage of ASTM A213 T91 Alloy Steel Seamless Tubes lies in their ability to operate reliably at higher temperatures and pressures, making them indispensable for enhancing the efficiency and performance of modern thermal power plants, particularly in ultra-supercritical (USC) boiler applications.
These tubes are manufactured in strict accordance with the ASTM A213 standard, with ASME SA213 T91 being the equivalent specification for boiler and pressure vessel code applications. The seamless construction ensures maximum integrity under extreme operating conditions.
Products Specification
| Specification | Details |
|---|---|
| Standard | ASTM A213, ASME SA213 |
| Grade | T91 (UNS K90901) |
| Product Description | Seamless CSEF 9Cr-1Mo-VNb Alloy Steel Tubes |
| Manufacturing Process | Hot finished or Cold drawn + Heat Treatment |
| Heat Treatment | Normalized ≥ 1040°C, Tempered ≥ 730°C |
| Outside Diameter (OD) | 1/2" (12.7mm) to 5" (127mm) |
| Wall Thickness (WT) | Sch 40, Sch 80, Sch 160, XXS & custom |
Chemical Composition
| Element | Content (wt %) |
|---|---|
| Carbon (C) | 0.08 - 0.12 |
| Manganese (Mn) | 0.30 - 0.60 |
| Phosphorus (P) | 0.020 max |
| Sulfur (S) | 0.010 max |
| Silicon (Si) | 0.20 - 0.50 |
| Chromium (Cr) | 8.00 - 9.50 |
| Molybdenum (Mo) | 0.85 - 1.05 |
| Vanadium (V) | 0.18 - 0.25 |
| Niobium (Nb) | 0.06 - 0.10 |
| Nitrogen (N) | 0.030 - 0.070 |
| Aluminum (Al) | 0.02 max (typically 0.04 for some specs) |
Mechanical Properties
| Property | Value (Minimum, unless stated) |
|---|---|
| Tensile Strength | 85,000 psi (585 MPa) |
| Yield Strength | 58,000 psi (400 MPa) |
| Elongation (in 2in/50mm) | 20% |
| Hardness | Rockwell B: 97 max / Brinell: 250 max (varies slightly with spec edition) |
Products Application
The exceptional high-temperature strength and creep resistance of ASTM A213 T91 Tubes make them the material of choice for the most demanding thermal applications:
Boiler Tubes: ASTM A213 T91 Boiler Tubes are used in critical components like waterwalls, superheaters, and reheaters in ultra-supercritical (USC) and advanced ultra-supercritical (A-USC) power boilers.
T91 Superheater & Reheater Tubes: For the highest temperature sections of modern power plants.
Main Steam Lines & Header Piping: Carrying high-pressure steam to turbines.
Heat Recovery Steam Generators (HRSGs): In combined cycle power plants.
Petrochemical & Refinery Heaters: For severe fired heater tube applications.
Advanced Power Generation: Critical for coal-fired USC plants and gas-fired combined cycles.
Chemical Processing: For equipment under high thermal and mechanical stress.
T91 Seamless Tubes allow for thinner wall designs, improving heat transfer and reducing fatigue in cyclic service.
