Delivering High Quality Stainless Steel and Alloy Piping Products — Pipes, Tubes, Fittings, Flanges and more for Global Industries.
sales@savoypipinginc.com
Delivering High Quality Stainless Steel and Alloy Piping Products — Pipes, Tubes, Fittings, Flanges and more for Global Industries.
sales@savoypipinginc.com
Savoy Piping Inc. supplies ASTM A335 P91 / ASME SA335 Grade P91 seamless pipe — the 9Cr-1Mo-V-Nb creep-strength-enhanced ferritic (CSEF) grade (UNS K91560) specified for modern high-pressure, high-temperature steam systems.
P91 is not “just another chrome moly.” Vanadium, niobium and controlled nitrogen create a tempered martensitic microstructure with strong creep resistance, which is why supercritical and advanced boiler projects use it for main steam and hot reheat lines. That same metallurgy means welding, PWHT, and hardness control are non-negotiable — soft or over-hard HAZs are a known risk if procedures slip.
What serious buyers ask for: heat chemistry within P91 limits, normalised-and-tempered condition, hardness within specification (typically max 250 HBW / equivalent for P91), PMI, and complete EN 10204 documentation. For IBR-linked work, SA335 P91 with Form III-C may also be required.
We also supply companion grades P22, P92, P11, and tube grade ASTM A213 T91.
Also see: Alloy steel seamless hub · Chrome moly hub · Alloy buttweld.
| Choose | When | Watch-outs |
|---|---|---|
| P91 | CSEF high-temp creep-critical steam | Hardness, PWHT, welding procedure critical |
| P92 | When tungsten-bearing CSEF is specified | Not interchangeable with P91 without design review |
| P22 | Lower alloy chrome-moly duties | Different allowable stress regime |
ASTM A335 / ASME SA335 P91 seamless NPS: ____ Sch/wall: ____ Length: ____ Qty: ____ Hardness window / HT notes: ____ IBR: Y/N MTC: 3.1/3.2 Destination: ____
Email to sales@savoypipinginc.com with destination and any IBR / NACE / TPI notes.
| A335 P91 Alloy Steel Seamless Pipes Specification | ASTM A335 / ASME SA335 |
| A335 P91 Alloy Steel Seamless Pipes Grades | ASTM A335 / ASME SA335 Grade P91 (9Cr-1Mo-V, CSEF) |
| A335 P91 Alloy Steel Seamless Pipes Type | Seamless - Hot Rolled / Cold Drawn |
| A335 P91 Alloy Steel Seamless Pipes Outer Diameter Size | A335 - 3/8" NB to 30" NB (Nominal Bore Size) |
| A335 P91 Alloy Steel Seamless Pipes Wall Thickness | Schedule 20 to Schedule XXS (Heavier On Request) Up to 250 mm Thickness |
| A335 P91 Alloy Steel Seamless Pipes Length | 5 to 7 Meters, 09 to 13 Meters, Single Random Length, Double Random Length And Customize Size. |
| A335 P91 Alloy Steel Seamless Pipes Ends | Plain Ends / Beveled Ends / Coupling |
| A335 P91 Alloy Steel Seamless Pipes Delivery Conditions | As Rolled, Cold Drawn, Normalizing Rolled, Thermomechanical Rolled / Formed, Normalizing Formed, Normalized and Tempered / Quenched and Tempered - BR / N / Q /T |
| A335 P92 Alloy Steel Seamless Pipes Coating | Epoxy Coating / Colour Paint Coating / 3LPE Coating. |
| A335 P91 Alloy Steel Seamless Pipes Other Testing | Tensile Test, Transverse Tension Tests, Flattening Test, Metal Structure and Etching Tests, Photomicrographs, Hardness Tests, etc. |
| A335 P91 Alloy Steel Seamless Pipes Dimension | All Pipes Is Manufactured and Inspected / Tested to the Relevant standards including ASTM, ASME, API. |
| A335 P91 Alloy Steel Seamless Pipes Value Added Services | Draw / Expansion / Machining / Sand Blasting / Shot Blasting / Galavanizing / Heat Treatment |
| A335 P91 Alloy Steel Seamless Pipes Packaging | Loose / Bundle / Wooden Pallet / Wooden box-a / Plastic Cloth Wraps / Plastic End Caps / Beveled Protector |
| A335 P91 Alloy Steel Seamless Pipes Shipment & Transportation | By Road - Truck / Train, By Sea - Break-bulk Conventional Vessel / FCL (Full Container Load) / LCL (Less Container Load) / 20 Feet Container / 40 Feet Container / 4 Feet Container / High Cube Container / Open Top Container, By Air - Freighter Civil Passenger and Cargo Planes |
| A335 P91 Alloy Steel Seamless Pipes Material Test Certificate | Manufacturer Test Certificate As Per EN10204 3.1, 3.2 / Laboratory Test Certificate From NABL Approved Lab. / Under Third Party Inspection Agency Like SGS, TUV, DNV, LLOYDS, ABS ETC |
ASTM A335 / ASME SA335 Grade P91 is a seamless ferritic alloy-steel pipe designed for high-temperature service, often called modified 9Cr-1Mo. Typical chemistry includes 8.00–9.50% Cr, 0.85–1.05% Mo, plus vanadium, niobium (columbium), and nitrogen within specified ranges.
The grade was developed to deliver high creep rupture strength so designers can run higher steam temperatures/pressures — or reduce wall thickness versus older Cr-Mo grades. Pipe must still be suitable for forming and fusion welding, but fabrication must follow CSEF best practice: controlled heat input, correct consumables, and carefully executed PWHT.
P91 is widely used in supercritical power piping. When even higher creep performance or thinner walls are required for ultra-supercritical designs, projects often evaluate ASTM A335 P92 (tungsten-bearing 9Cr). For lower-temperature steam headers, P22 or P11 may still be the economical choice.
P91 is the established CSEF 9Cr grade for supercritical steam piping. P92 adds tungsten (with lower Mo) for further creep improvement in more demanding USC service. P22 remains the conventional 2.25Cr-1Mo choice for many subcritical hot steam systems and should not be casually upgraded/downgraded without design review. Matching tube: A213 T91.
Heat-analysis composition limits for seamless pipe ordered as Grade P91 shall conform to ASTM A335 / ASME SA-335, Table 1 (UNS K91560). Values below are mass percent.
| Element | Composition, % |
|---|---|
| Carbon | 0.08–0.12 |
| Manganese | 0.30–0.60 |
| Phosphorus, max | 0.020 |
| Sulfur, max | 0.010 |
| Silicon | 0.20–0.50 |
| Chromium | 8.00–9.50 |
| Molybdenum | 0.85–1.05 |
| Vanadium | 0.18–0.25 |
| Nitrogen | 0.030–0.070 |
| Nickel, max | 0.40 |
| Aluminum, max | 0.02 |
| Columbium (Niobium) | 0.06–0.10 |
| Titanium, max | 0.01 |
| Zirconium, max | 0.01 |
Room-temperature tensile requirements for Grade P91 seamless pipe shall conform to ASTM A335 / ASME SA-335, Table 3 (longitudinal orientation).
| Seamless, Grade P91 (UNS K91560) | ||
| P-91 | Grades P91, P92, P122, and P911 shall have a hardness not exceeding 250 HB / 265 HV [25 HRC] (see ASTM A335 / SA-335). | |
| Tensile Strength, min., psi | ||
| ksi | 85 | |
| MPa | 585 | |
| Yield Strength, min., psi | ||
| ksi | 60 | |
| MPa | 415 |
| Transverse or Longitudinal Tension Test and Flattening Test, Hardness Test, or Bend Test | |
| For material heat treated in a batch-type furnace, tests shall be made on 5% of the pipe from each treated lot. for small lots, at least one pipe shall be tested. | |
| For material heat treated by the continuous process, tests shall be made on a sufficient number of pipe to constitute 5% of the lot, but in no case less than 2 pipe. | |
| Notes for Hardness Test: | P91 shall not have a hardness not exceeding 250 HB/265 HV [25HRC]. |
| Notes for Bend Test: | For pipe whose diameter exceeds NPS 25 and whose diameter to wall thickness ratio is 7.0 or less shall be subjected to the bend test instead of the flattening test. |
| Other pipe whose diameter equals or exceeds NPS 10 may be given the bend test in place of the flattening test subject to the approval of the purchaser. | |
| The bend test specimens shall be bent at room temperature through 180 without cracking on the outside of the bent portion. | |
| The inside diameter of the bend shall be 1 inch [25 mm]. | |
| Hydrostatic test | Each length of pipe shall be Hydro tested, at option of manufacture, nondestructive electric testing can be used. |
| P5, P9, P11, and P22 | |||
| Grade | Heat Treatment Type | Normalizing Temperature Range F [C] | Subcritical Annealing or Tempering Temperature Range F [C] |
| P91 | Normalize and Temper | 1900-1975 [1040 – 1080] | 1350-1470 [730 – 800] |
| Quench and Temper | 1900-1975 [1040 – 1080] | 1350-1470 [730 – 800] |
| NPS [DN] Designator | Tolerance, % from Specified | |
| Over | Under | |
| 1/8 to 2 1/2 [6 to 65] incl., all t/D ratios | 20.0% | 12.5% |
| Above 2 1/2 [65], t/D < or = 5% | 22.5% | 12.5% |
| Above 2 1/2 [65], t/D > 5% | 15.0% | 12.5% |
| (t = Specified Wall Thickness; D = Specified Outside Diameter) | ||
| Calculated Minimum Elongation Values | ||||
| Elongation in 2 in. or 50 mm, min % | ||||
| Wall Thickness | P5, P9, P11, P22 | P91 | ||
| in. | mm | Longitudinal | Transverse | Longitudinal |
| 5/16 (0.312) | 8 | 30 | 20 | 20 |
| 9/32 (0.281) | 7.2 | 28 | 19 | 19 |
| 1/4 (0.250) | 6.4 | 27 | 18 | 18 |
| 7/32 (0.219) | 5.6 | 26 | 17 | |
| 3/16 (0.188) | 4.8 | 24 | 16 | |
| 5/32 (0.156) | 4 | 22 | 15 | |
| 7/8 (0.125) | 3.2 | 21 | 14 | |
| 3/32 (0.094) | 2.4 | 20 | 13 | |
| 1/18 (0.062) | 1.6 | 18 | 12 | |
Outside Diameter at any point shall not vary from standard specified more than:
| NPS [DN] Designator | Over | Under | ||
| in. | mm | in. | mm | |
| 1/8 to 1 1/2 [6 to 40], incl. | 1/64 (0.015) | 0.40 | 1/64 (0.015) | 0.40 |
| Over 1 1/2 to 4 [40 to 100], incl. | 1/32 (0.031) | 0.79 | 1/32 (0.031) | 0.79 |
| Over 4 to 8 [100 to 200], incl. | 1/16 (0.062) | 1.59 | 1/32 (0.031) | 0.79 |
| Over 8 to 12 [200 to 300], incl. | 3/32 (0.093) | 2.38 | 1/32 (0.031) | 0.79 |
| Over 12 [300] | +/- 1% of the specified outside diameter | |||
(On Tags attached to each Bundle in case of Bundled Pipe) Markings will adhere to prescribed specifications in A 999/A999M and be: Rolled, Stamped, or Stenciled (Mfrs. Option)
| In addition, markings will include: | |||
| Length of pipe |
|
||
| Marking to indicante the test method(s) | |||
| Hydrostatic | Nondestructive | Marking | |
| YES | NO | Test Pressure | |
| NO | YES | NDE | |
| NO | NO | NH | |
| YES | YES | Test Pressure/NDE | |
Orders for material under this specification should include the following, as required, to describe the desired material adequately:
| Quantity | Feet, meters, or number of lengths |
| Name of material | Seamless Alloy Steel Pipe |
| Grade | P5, P9, P11, P22, P91 |
| Manufacturer | Hot-finished or cold-drawn |
| Size using one of the following: | |
| NPS and Schedule Number | |
| Outside Diameter and Nominal Wall Thickness | |
| Outside Diameter and Minimum Wall Thickness | |
| Inside Diameter and Nominal Wall Thickness | |
| Inside Diameter and Minimum Wall Thickness | |
| Length | Specific or Random |
| End Finish | |
ASTM A335 P91 is used for high-temperature, high-pressure steam piping — especially main steam and hot reheat systems in supercritical power plants — where creep strength of modified 9Cr-1Mo is required.
Both are 9Cr CSEF steels. P91 is 9Cr-1Mo-V-Nb; P92 reduces molybdenum and adds tungsten (about 1.5–2%) plus boron control for improved creep strength. P92 is typically considered for more demanding ultra-supercritical applications.
Incorrect welding or PWHT can leave soft or overly hard zones that hurt creep life or toughness. Specifications limit hardness for P91, and projects usually require documented hardness surveys after heat treatment.
Yes. We supply ASTM A335 / ASME SA335 P91 seamless pipe with EN 10204 3.1 or 3.2 MTCs, and can support third-party inspection and IBR documentation when required by the purchase order.
We supply this product for domestic and export projects with mill test certificates (EN 10204 3.1 standard; 3.2 / TPI on request). Include destination, preferred Incoterms and any inspection body on the RFQ.