Description
What is ASTM A213 T91 Seamless Tube
ASTM A213 T91 is a ferritic-martensitic alloy steel tube primarily used in high-temperature applications such as power plants, heat exchangers, and boilers. The seamless tube is designed for superior strength, high oxidation resistance, and excellent mechanical properties at elevated temperatures. T91 is part of the ASTM A213 standard, which specifies seamless ferritic and austenitic alloy-steel boiler, superheater, and heat-exchanger tubes.
ASTM A213 T91 Chemical Composition
| Element | Composition (%) |
| 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 |
| Nitrogen (N) | 0.030 - 0.070 |
| Niobium (Nb) | 0.06 - 0.10 |
| Aluminum (Al) | 0.02 max |
ASTM A213 T91 Mechanical Properties
| Property | Value |
| Tensile Strength, min (MPa) | 585 |
| Yield Strength, min (MPa) | 415 |
| Elongation, min (%) | 20 |
| Hardness, max (HBW) | 250 |
UNS K91560 T91 Boiler Tube Weight Chart
| Nominal Pipe Size | Pipe Outer Diameter | Wall Thickness | Pipe Inner Diameter | Weight per Foot | Standard to XXHY | Schedule
Pipe # | Section Modulus | Gallon Capacity Per Linear Foot |
| 1/2 | 0.84 | 0.109 | 0.622 | 0.85 | STD | 40 | 0.0407 | 0.0158 |
| | 0.147 | 0.546 | 1.09 | XHY | 80 | 0.0478 | 0.0122 |
| | 0.188 | 0.464 | 1.31 | | 160 | 0.0528 | 0.0088 |
| | 0.294 | 0.252 | 1.72 | XXHY | | 0.0577 | 0.0026 |
| 3/4 | 1.05 | 0.113 | 0.824 | 1.13 | STD | 40 | 0.0705 | 0.0277 |
| | 0.154 | 0.742 | 1.48 | XHY | 80 | 0.0853 | 0.0225 |
| | 0.219 | 0.612 | 1.95 | | 160 | 0.1006 | 0.0153 |
| | 0.308 | 0.434 | 2.44 | XXHY | | 0.1103 | 0.0077 |
| 1 | 1.315 | 0.133 | 1.049 | 1.68 | STD | 40 | 0.1328 | 0.0449 |
| | 0.179 | 0.957 | 2.17 | XHY | 80 | 0.1606 | 0.0374 |
| | 0.25 | 0.815 | 2.85 | | 160 | 0.1904 | 0.0271 |
| | 0.358 | 0.599 | 3.66 | XXHY | | 0.2136 | 0.0146 |
| 1 1/4 | 1.66 | 0.14 | 1.38 | 2.27 | STD | 40 | 0.2346 | 0.0777 |
| | 0.191 | 1.278 | 3 | XHY | 80 | 0.2913 | 0.0666 |
| | 0.25 | 1.16 | 3.77 | | 160 | 0.3421 | 0.0549 |
| | 0.382 | 0.896 | 5.22 | | | 0.411 | 0.0328 |
| 1 1/2 | 1.9 | 0.145 | 1.61 | 2.72 | STD | 40 | 0.3262 | 0.1058 |
| | 0.2 | 1.5 | 3.63 | XHY | 80 | 0.4118 | 0.0918 |
| | 0.281 | 1.338 | 4.86 | | 160 | 0.5079 | 0.073 |
| | 0.4 | 1.1 | 6.41 | | | 0.5977 | 0.0494 |
| 2 | 2.375 | 0.109 | 2.157 | 2.64 | | 10 | 0.4205 | 0.1898 |
| | 0.154 | 2.067 | 3.66 | STD | 40 | 0.5606 | 0.1743 |
| | 0.218 | 1.939 | 5.03 | XHY | 80 | 0.7309 | 0.1534 |
| | 0.25 | 1.875 | 5.68 | | | 0.8045 | 0.1434 |
| | 0.281 | 1.813 | 6.29 | | | 0.8666 | 0.1344 |
| | 0.344 | 1.687 | 7.47 | | 160 | 0.9806 | 0.1161 |
| | 0.436 | 1.503 | 9.04 | XXHY | | 1.1043 | 0.0922 |
| 2 1/2 | 2.875 | 0.12 | 2.635 | 3.53 | | 10 | 0.687 | 0.2833 |
| | 0.203 | 2.469 | 5.8 | STD. | 40 | 1.064 | 0.2487 |
| | 0.216 | 2.443 | 6.14 | | | 1.1169 | 0.2435 |
| | 0.25 | 2.375 | 7.02 | | | 1.2468 | 0.2301 |
| | 0.276 | 2.323 | 7.67 | XHY | 80 | 1.3386 | 0.2202 |
| | 0.375 | 2.125 | 10.02 | | 160 | 1.6371 | 0.1842 |
| | 0.552 | 1.771 | 13.71 | XXXHY | | 1.9971 | 0.128 |
| 3 | 3.5 | 0.12 | 3.26 | 4.34 | | | 1.0411 | 0.4336 |
| | 0.156 | 3.188 | 5.58 | | | 1.3122 | 0.4147 |
| | 0.172 | 3.156 | 6.12 | | | 1.4265 | 0.4064 |
| | 0.188 | 3.124 | 6.66 | | | 1.5342 | 0.3984 |
| | 0.216 | 3.068 | 7.58 | STD. | 40 | 1.7241 | 0.384 |
| | 0.25 | 3 | 8.69 | | | 1.9372 | 0.3672 |
| | 0.281 | 2.938 | 9.67 | | | 2.1207 | 0.3521 |
| | 0.3 | 2.9 | 10.26 | XHY | 80 | 2.2253 | 0.3431 |
| | 0.438 | 2.624 | 14.34 | | 160 | 2.8774 | 0.2811 |
| | 0.6 | 2.3 | 18.6 | XXHY | | 3.4243 | 0.2158 |
| 3 1/2 | 4 | 0.12 | 3.76 | 4.98 | | 10 | 1.3776 | 0.5768 |
| | 0.226 | 3.548 | 9.12 | STD. | 140 | 2.3939 | 0.5136 |
| | 0.25 | 3.5 | 10.02 | | | 2.6001 | 0.4998 |
| | 0.281 | 3.438 | 11.17 | | | 2.8562 | 0.4821 |
| | 0.318 | 3.364 | 12.52 | XHY | 80 | 3.14 | 0.4617 |
| | 0.636 | 2..728 | 22.87 | XXHY | | 4.8795 | 0.3085 |
| 4 | 4.5 | 0.12 | 4.26 | 5.62 | | 10 | 1.7612 | 0.7404 |
| | 0.156 | 4.188 | 7.24 | | | 2.2354 | 0.7156 |
| | 0.188 | 4.124 | 8.67 | | | 2.6296 | 0.6942 |
| | 0.203 | 4.094 | 9.32 | | | 2.8173 | 0.6838 |
| | 0.219 | 4.062 | 10.02 | | | 3.0184 | 0.6725 |
| | 0.237 | 4.026 | 10.8 | STD. | 40 | 3.2145 | 0.6613 |
| | 0.25 | 4 | 11.36 | | | 3.3611 | 0.6528 |
| | 0.281 | 3.938 | 12.67 | | 60 | 3.7021 | 0.6326 |
| | 0.312 | 3.876 | 13.97 | | | 4.0273 | 0.6126 |
| | 0.337 | 3.826 | 15 | XHY | 80 | 4.2713 | 0.5972 |
| | 0.438 | 3.624 | 19.02 | | 120 | 5.179 | 0.5361 |
| | 0.531 | 3.438 | 22.53 | | 160 | 5.8997 | 0.4822 |
| | 0.674 | 3.152 | 27.57 | XXHY | | 6.7927 | 0.4054 |
| 5 | 5.563 | 0.188 | 5.187 | 10.8 | | | 4.1161 | 1.0979 |
| | 0.219 | 5.125 | 12.51 | | | 4.7279 | 1.0716 |
| | 0.258 | 5.047 | 14.63 | STD. | 40 | 5.45 | 1.0391 |
| | 0.281 | 5.001 | 15.87 | | | 5.8644 | 1.0204 |
| | 0.312 | 4.939 | 17.51 | | | 6.4074 | 0.99647 |
| | 0.344 | 4.875 | 19.19 | | | 6.9358 | 0.9696 |
| | 0.375 | 4.813 | 20.8 | XHY | 80 | 7.43 | 0.9449 |
| | 0.5 | 4.563 | 27.06 | | 120 | 9.2534 | 0.8495 |
| | 0.625 | 4.313 | 32.99 | | 160 | 10.7976 | 0.759 |
| | 0.75 | 4.063 | 38.59 | XXHY | | 12.0954 | 0.6734 |
| 6 | 6.625 | 0.109 | 6.407 | 7.59 | | 5 | 3.5769 | 1.6748 |
| | 0.134 | 6.357 | 9.3 | | 10 | 4.3475 | 1.6488 |
| | 0.156 | 6.313 | 10.79 | | | 5.0107 | 1.626 |
| | 0.188 | 6.249 | 12.94 | | | 5.9351 | 1.5937 |
| | 0.203 | 6.219 | 13.94 | | | 6.3804 | 1.578 |
| | 0.219 | 6.187 | 15 | | | 6.8261 | 1.562 |
| | 0.25 | 6.125 | 17.04 | | | 7.6905 | 1.5306 |
| | 0.28 | 6.065 | 18.99 | STD. | 40 | 8.4958 | 1.5008 |
| | 0.312 | 6.001 | 21.06 | | | 9.3416 | 1.4688 |
| | 0.344 | 5.937 | 23.1 | | | 10.111 | 1.4391 |
| | 0.375 | 5.875 | 25.05 | | | 10.893 | 1.4082 |
| | 0.432 | 5.761 | 28.6 | XHY | 80 | 12.224 | 1.3541 |
| | 0.5 | 5.625 | 32.74 | | | 13.711 | 1.2909 |
| | 0.562 | 5.501 | 36.43 | | 120 | 14.9806 | 1.2346 |
| | 0.625 | 5.375 | 40.09 | | | 16.1821 | 1.1787 |
| | 0.719 | 5.187 | 45.39 | | 160 | 17.8243 | 1.0977 |
| | 0.864 | 4.897 | 53.21 | XXHY | | 20.025 | 0.9784 |
| | 1 | 4.625 | 60.13 | | | 21.7719 | 0.8727 |
| | 1.125 | 4.375 | 66.14 | | | 23.1237 | 0.7809 |
ASTM A213 T91 Alloy Steel Seamless Tubes Dimensional Tolerances
Hot Rolled
| Outside Diameter (OD) | Wall Thickness (WT) | OD Tolerance (mm) | WT Tolerance (%) |
| ≤101.6 mm | ≤2.4 mm | +0.4 / -0.8 | +40 / -0 |
| ≤101.6 mm | 2.4 mm < WT ≤ 3.8 mm | +0.4 / -0.8 | +35 / -0 |
| ≤101.6 mm | 3.8 mm < WT ≤ 4.6 mm | +0.4 / -0.8 | +33 / -0 |
| ≤101.6 mm | >4.6 mm | +0.4 / -0.8 | +28 / -0 |
| >101.6 mm | 2.4 mm < WT ≤ 3.8 mm | +0.4 / -1.2 | +35 / -0 |
| >101.6 mm | 3.8 mm < WT ≤ 4.6 mm | +0.4 / -1.2 | +33 / -0 |
| >101.6 mm | >4.6 mm | +0.4 / -1.2 | +28 / -0 |
Cold Rolled
| Outside Diameter (OD) | OD Tolerance (mm) |
| <25.4 mm | ±0.10 |
| 25.4 mm ≤ OD ≤ 38.1 mm | ±0.15 |
| 38.1 mm < OD < 50.8 mm | ±0.20 |
| 50.8 mm ≤ OD < 63.5 mm | ±0.25 |
| 63.5 mm ≤ OD < 76.2 mm | ±0.30 |
| 76.2 mm ≤ OD ≤ 101.6 mm | ±0.38 |
| 101.6 mm < OD ≤ 190.5 mm | +0.38 / -0.64 |
| 190.5 mm < OD ≤ 228.6 mm | +0.38 / -1.14 |
Manufacturing Process
- Melting and Casting: The raw materials are melted in an electric arc furnace and refined through vacuum degassing to remove impurities.
- Hot Rolling: The steel is hot-rolled into tube form using a mandrel mill, rotary piercing, or extrusion process.
- Heat Treatment: T91 tubes undergo a normalization process at 1040°C (1904°F) followed by air cooling, and then tempering at 760°C (1400°F) to enhance toughness and mechanical properties.
- Cold Drawing (if required): Some tubes are cold-drawn to achieve precise dimensions and improved surface finish.
- Testing and Inspection: Each tube undergoes rigorous non-destructive and destructive testing, including ultrasonic testing, eddy current testing, hydrostatic testing, and visual inspection.
- Surface Finishing: The tubes are pickled, passivated, or coated as per customer requirements.
Benefits
- High-Temperature Strength: T91 tubes exhibit exceptional creep strength and resistance to thermal fatigue, making them ideal for prolonged exposure to high temperatures.
- Corrosion and Oxidation Resistance: The chromium and molybdenum content enhances corrosion resistance, preventing oxidation and scaling in aggressive environments.
- Enhanced Toughness and Durability: With superior impact toughness and mechanical strength, these tubes can withstand extreme pressure and temperature variations without failure.
- Excellent Weldability: Despite their high alloy content, T91 seamless tubes can be welded using standard welding techniques, including TIG, MIG, and SMAW processes.
- Cost-Effectiveness: Due to their long service life and minimal maintenance requirements, ASTM A213 T91 seamless tubes offer a cost-effective solution for critical applications.
- Compliance with International Standards: T91 tubes meet stringent ASTM, ASME, and other international standards, ensuring quality, reliability, and safety.
Applications
- Power Plants
- Petrochemical and Refining Industry
- Aerospace Industry
- Marine and Shipbuilding
- Automotive and Heavy Machinery
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