Tubewell Steel & Engg. Co. is a leading manufacturer and stockist specializing in Alloy Steel Pipes, Tubes, Fittings and Flanges for critical industrial applications.
Modified 9% Chromium – 1% Molybdenum – Vanadium plates with high creep strength for supercritical power plants and severe high-temperature service.
Tubewell Steel & Engg. Co. is a stockist and supplier of ASTM A387 Gr 91 plates in Mumbai, India. Grade 91 is a modified 9Cr-1Mo steel with controlled additions of vanadium, niobium and nitrogen. It offers much higher creep strength than conventional chrome-moly grades, which allows thinner, lighter components in high-temperature service.
Why A387 Grade 91 leads in high-temperature creep strength
ASTM A387 Grade 91 is a creep-strength enhanced ferritic (CSEF) steel plate with nominally 9% chromium and 1% molybdenum, microalloyed with vanadium, niobium and nitrogen. These additions form fine, stable carbonitride precipitates in a tempered martensitic structure. The result is creep-rupture strength well above Grades 9 and 22, together with good oxidation resistance and lower thermal expansion. Grade 91 is used at temperatures up to about 650°C (1200°F), depending on the design code.
Grade 91 is supplied in Class 2 only and must be normalized at 1040–1080°C (1900–1975°F) and tempered at 730–800°C (1350–1470°F). Because its properties depend on correct heat treatment, we verify every plate's chemistry and tensile properties and supply full EN 10204 3.1 documentation. Hardness checks, simulated PWHT testing, ultrasonic testing to ASTM A435 / A578 and third-party inspection are available on request.
Standard supply range for ASTM A387 Gr 91 plates
| Parameter | Details |
|---|---|
| Standard | ASTM A387, ASME SA387 |
| General Requirements | ASTM A20 / ASME SA20 |
| Grade | Grade 91 (UNS K90901) |
| Class | Class 2 (only class specified for Grade 91) |
| Thickness | 3 mm to 150 mm (higher thickness on request) |
| Width | Up to 2500 mm (3000 mm on request) |
| Length | Up to 12000 mm |
| Forms | Sheet, Plate, Coil, Strip, Circle, Ring, Flat |
| Finish | Hot Rolled (HR), Cold Rolled (CR), Shot Blasted |
| Delivery Condition | Normalized (1040–1080°C) & Tempered (730–800°C) |
| Cutting Services | Plasma, Gas / Oxy-fuel, Waterjet, Shearing, Profile Cutting to Drawing |
| Testing | Tensile, Hardness, Impact, UT (ASTM A435 / A578), PMI, Simulated PWHT |
| Certificates | EN 10204 3.1 / 3.2, IBR (where applicable), TPI Reports |
International equivalents of A387 Grade 91
| Grade | ASTM / ASME | UNS | EN 10028-2 | W.Nr. | Matching Pipe / Tube | Nominal Composition |
|---|---|---|---|---|---|---|
| Gr 91 | A387 / SA387 Gr 91 | K90901 | X10CrMoVNb9-1 | 1.4903 | A335 P91 / A213 T91 | 9Cr-1Mo-V-Nb |
Equivalents are the closest comparable grades; chemistry and mechanical limits are not identical. Please confirm suitability against your design code.
Weight %, heat analysis as per ASTM A387
| Grade | C | Mn | P | S | Si | Cr | Mo | Ni | V | Nb | N | Al |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A387 Gr 91 | 0.08 – 0.12 | 0.30 – 0.60 | 0.020 max | 0.010 max | 0.20 – 0.50 | 8.00 – 9.50 | 0.85 – 1.05 | 0.40 max | 0.18 – 0.25 | 0.06 – 0.10 | 0.030 – 0.070 | 0.02 max |
Ti 0.01 max and Zr 0.01 max. Limits shown are for Grade 91 Type 1; Type 2 has tighter limits per the current edition of ASTM A387.
Tensile requirements at room temperature as per ASTM A387
| Grade | Tensile Strength | Yield Strength (min) | Elongation in 50 mm (min) |
|---|---|---|---|
| Gr 91 Class 1 | Not specified – Grade 91 is supplied as Class 2 only | ||
| Gr 91 Class 2 | 585 – 760 MPa (85 – 110 ksi) | 415 MPa (60 ksi) | 18% |
Typical values (for reference)
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.77 g/cm³ | 0.281 lb/in³ |
| Melting Range | 1450 – 1510 °C | 2640 – 2750 °F |
| Modulus of Elasticity | 218 GPa | 31.6 × 10³ ksi |
| Thermal Conductivity (100°C) | 26 W/m·K | 15.0 BTU/h·ft·°F |
| Mean Thermal Expansion (20–300°C) | 11.4 µm/m·°C | 6.3 µin/in·°F |
| Specific Heat | 0.46 J/g·°C | 0.11 BTU/lb·°F |
| Max. Service Temperature | ≈ 650 °C | ≈ 1200 °F |
Plate thickness (mm) vs theoretical weight (kg/m²)
| Thickness (mm) | ≈ Inch | Weight (kg/m²) | 1500 × 6000 mm (kg) | 2000 × 6000 mm (kg) | 2500 × 12000 mm (kg) |
|---|---|---|---|---|---|
| 3 | 1/8" | 23.55 | 211.95 | 282.60 | 706.50 |
| 5 | 3/16" | 39.25 | 353.25 | 471.00 | 1177.50 |
| 6 | 1/4" | 47.10 | 423.90 | 565.20 | 1413.00 |
| 8 | 5/16" | 62.80 | 565.20 | 753.60 | 1884.00 |
| 10 | 3/8" | 78.50 | 706.50 | 942.00 | 2355.00 |
| 12 | 1/2" | 94.20 | 847.80 | 1130.40 | 2826.00 |
| 16 | 5/8" | 125.60 | 1130.40 | 1507.20 | 3768.00 |
| 20 | 3/4" | 157.00 | 1413.00 | 1884.00 | 4710.00 |
| 25 | 1" | 196.25 | 1766.25 | 2355.00 | 5887.50 |
| 30 | 1 3/16" | 235.50 | 2119.50 | 2826.00 | 7065.00 |
| 40 | 1 9/16" | 314.00 | 2826.00 | 3768.00 | 9420.00 |
| 50 | 2" | 392.50 | 3532.50 | 4710.00 | 11775.00 |
| 60 | 2 3/8" | 471.00 | 4239.00 | 5652.00 | 14130.00 |
| 80 | 3 1/8" | 628.00 | 5652.00 | 7536.00 | 18840.00 |
| 100 | 4" | 785.00 | 7065.00 | 9420.00 | 23550.00 |
| 150 | 6" | 1177.50 | 10597.50 | 14130.00 | 35325.00 |
Weight (kg/m²) = Thickness (mm) × 7.85. Values are theoretical; Grade 91 (density ≈ 7.77 g/cm³) weighs about 1% less. Standard plate sizes: 1250 × 2500, 1500 × 3000, 1500 × 6000, 2000 × 6000, 2500 × 6000 and 2500 × 12000 mm. Cut-to-size pieces supplied on request.
Where ASTM A387 Gr 91 plates are used
Headers, steam separators and boiler components at high steam temperatures.
Superheater and reheater headers and HRSG pressure parts.
Thin-wall, high-temperature vessels where creep strength governs design.
Tube sheets and shells for high-temperature exchangers.
Refinery and petrochemical reactors in severe thermal service.
Heater components and high-temperature process equipment.
Quality you can verify on every heat
Large inventory for fast dispatch
MTC EN 10204 3.1 / 3.2
Positive material identification
Pan-India & export shipping
Quick answers about A387 Grade 91 plates
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