ASTM A182-F91 Forged Parts | F91 Steel Forgings Manufacturer in China

What is ASTM A182-F91 Steel?

ASTM A182-F91 is a high-chromium (9% Cr) martensitic alloy steel with carefully balanced additions of molybdenum (Mo), vanadium (V) and niobium (Nb). This unique chemical composition gives F91 steel exceptional elevated-temperature mechanical properties, excellent creep resistance up to 640 °C, and superior resistance to hydrogen embrittlement under high pressure.

As the industry-standard material for supercritical and ultra-supercritical (USC) power generation equipment, F91 steel has replaced traditional carbon steels and low-alloy steels in modern power plants, so that it has higher operating temperatures and pressures, which significantly improve energy efficiency and reduce carbon emissions.

Complete Range of ASTM A182-F91 Forging Products from China

At our Jiangyin manufacturing facility, we can manufacture a comprehensive range of shapes and forms using F91 alloy steel to meet your most demanding industrial requirements. And we make parts with weights range from 30kg up to 30,000kg per single  piece with an annual output of 120,000 tons.

Available Shapes of F91 Forged Steel Products

• ASTM A182-F91 Forged Bars: Round bars, square bars, flat bars, rectangular bars and rods up to 2 meters in diameter
• ASME SA182 F91 Forged Rings: Seamless rolled rings up to 6 meters in diameter, swivel ring flanges and custom contoured rings
• ASME SA336 F91 Hollow Parts: Hubs, housings, shells, sleeves, bushes, cases and hollow bars up to 3000mm OD
• ASME SA336 P91 Plate Products: Discs, disks, blocks and plates up to 3 meters in diameter
• Piping and Tubing: Pipes, tubes, tubings, piping shells, casings, barrels and housings
• Custom Forged Parts: Machined parts according to your drawings and technical specifications

Comprehensive Industrial Applications of ASTM A182-F91 Forged Parts

Our Chinese-manufactured F91 forged parts are widely used in industries that require components to operate under extreme conditions of high temperature, high pressure and corrosive environments.

Power Generation Industry (Primary Application)

F91 steel is the most important material for modern supercritical and ultra-supercritical (USC) power plants operating at 550-640°C and 18-30 MPa steam conditions. Following  are main area our F91 forgings are extensively used in:

• Supercritical and ultra-supercritical boiler jackets, headers and connectors
• Steam superheater outlet chambers and superheated steam superheaters
• Reheater tubes, steam collectors and outlet collectors
• Gas and steam turbine MSV/GV/CV/CRV valve seats, cores and sleeves
• Main steam valve covers, bonnets and steam turbine rotor shafts
• Boiler installation fittings, sleeves and transition cones
• Combined-cycle power plant components and heat recovery steam generators

High-Pressure Valve Manufacturing

Our ASTM A182-F91 forged steel valve components are designed to withstand the most severe service conditions in power plants and industrial processes:

• High pressure gate valves, globe valves and swing check valves
• Steam turbine power valves and gas turbine bypass valves
• Line blind valves and preheater bypass valves
• Valve bodies, bonnets, closures, seat rings and stems
• Valve discs, disks and double studded adapter flanges
• Oil measurement valve spools and ultrasonic flow meter bodies
• Venturi cone meter bodies and pressure relief valve components

Oil, Gas and Petrochemical Industries

F91 alloy steel is ideal for high-temperature and high-pressure applications in the oil, gas and petrochemical sectors:

• High-temperature process piping and pressure vessels
• Boiler, heat exchanger and furnace components
• Tube sheets, nozzles, channel flanges and piping fittings
• Lateral tees, T-pieces, wyes and eccentric lateral tees
• Pump suction side sealing jackets, seal chambers and jacket casings
• Pump casings, covers, barrels, impellers, shafts and wear rings
• Swept branches, outlets, steel fittings and swept saddles

Nuclear Power Industry

Our high-quality F91 forged components meet the stringent quality and safety requirements of nuclear power plants:

• Nuclear reactor coolant pump casings, shells and bodies
• Nuclear reactor coolant pumps containment seal chambers
• Pressure vessel studding outlets and auxiliary system components

Global Project References for F91 Forged Parts

Standard Designations for F91 Forging Steel

F91 steel is recognized by various international standards and is known by the following designations:

• ASTM A182 F91, ASME SA182 F91
• ASTM A336 F91, ASME SA336 F91
• ASTM A335 P91, ASME SA335 P91
• ASTM A182 F911, ASME SA182 F911
• ASTM A335 P911, ASME SA335 P911
• ASTM A336 FP91, ASTM A387 Grade 91
• ASTM A200 T91, ASTM A691 Grade 91
• EN 10216-2 10CrMo9-10, DIN 17175 10CrMo910

Why F91 Steel Replaced Earlier Alloys — and How It Compares Today

The Engineering Problem That Created F91

The global push toward higher thermal efficiency in coal-fired power generation during the 1980s and 1990s created an engineering challenge that conventional pressure vessel steels could not solve. Moving from subcritical steam conditions (538 °C / 16 MPa) to supercritical (566 °C / 24 MPa) and then to ultra-supercritical (USC) conditions (600–620 °C / 27–30 MPa) demands dramatically higher creep strength in the pressure-retaining components — headers, valve bodies, turbine casings and piping — that carry superheated steam for 200,000+ hours of service life.

The dominant material of the previous generation, 2.25Cr-1Mo steel (Grade F22), becomes structurally inadequate above approximately 570 °C. Its creep rupture strength at 600 °C drops to roughly 35 MPa at 100,000 hours — far too low for the wall thicknesses that USC plant economics demand. Simply using thicker F22 walls is not a viable solution: heavier components increase the thermal mass, lengthen startup and shutdown times, and introduce unacceptable thermal fatigue risk during cycling operation.

The 9Cr-1Mo-V-Nb alloy system that became ASTM A182-F91 was originally developed at Oak Ridge National Laboratory (USA) in a collaborative programme with the Japanese National Institute for Materials Science and European power engineering institutes. The key metallurgical insight was that adding precisely balanced quantities of vanadium (V), niobium (Nb) and nitrogen (N) to a 9% chromium martensitic steel creates a dual precipitation-hardening mechanism: MX-type carbonitrides (primarily VN and NbC) pin sub-grain boundaries and dislocation networks at high temperatures, while M₂₃C₆ carbides on prior-austenite grain boundaries resist grain boundary sliding. Together, these mechanisms give F91 a 100,000-hour creep rupture strength at 600 °C of approximately 90 MPa — more than 2.5× higher than F22 — while retaining good weldability and similar coefficient of thermal expansion to ferritic steels.

This combination of properties made F91 the reference material for supercritical power plant construction from the mid-1990s onward, and it remains the most widely specified 9% Cr steel in both new-build USC plants and the repair/replacement market for existing supercritical units.

ASTM A182-F91 vs Competing High-Temperature Alloy Steels — Detailed Comparison

Selecting the correct alloy grade is one of the most consequential decisions in high-temperature plant design. The table below compares F91 against the most common alternative grades across key engineering parameters:

* Creep rupture values are average published data; actual design allowables per applicable code (ASME BPVC Section II Part D, EN 13480, etc.) should always be used for design calculations.

Disclaimer: Brand names in the filler metal table (Böhler, ESAB, Lincoln Electric, etc.) are listed for informational reference only. Jiangsu Liangyi has no commercial affiliation with these manufacturers. Always verify current product approvals and classifications with the filler metal manufacturer before use. Consult your welding engineer or procedure qualification records for final filler metal selection.

Grade Selection Guide: When to Choose F91

• Choose F91 over F22 when service temperatures exceed 570 °C, when creep is the life-limiting failure mode, or when wall-thickness reduction is required to control thermal fatigue during cycling operation.
• Choose F92 over F91 only when operating above 610 °C continuously and the premium cost (typically 30–50% higher per kg) can be justified. F92's tungsten additions provide superior creep strength in this temperature range, but the material is less widely available and requires the same strict welding protocols as F91.
• Stay with F11 or F22 for lower-temperature sections (below 550 °C) where cost reduction is a priority and the extra creep strength of F91 is not required by the design calculation.
• Avoid direct F91 substitution with austenitic stainless grades (304H, 316H) in cycling plant: the thermal expansion coefficient of austenitic steels (~18 × 10⁻⁶ K⁻¹) is nearly 50% higher than F91, which generates severe differential thermal stress at dissimilar metal welds and in mixed-material assemblies.

Technical Specifications of ASTM A182-F91 Forging Steel

Chemical Composition (Weight %)

All our F91 forged materials are melted using electric furnace process (EAF) followed by argon oxygen decarburization (AOD) or Vacuum Oxygen Decarburization (VOD) to ensure ultra-low impurity levels and superior steel quality.

Room Temperature Mechanical Properties

Elevated Temperature Properties

Creep and Stress Rupture Properties (Average Values)

* Extrapolated values

Thermal Properties

Heat Treatment Process

All our F91 forged parts undergo precise heat treatment to achieve the required mechanical properties and microstructure:

Comprehensive Quality Testing

Every F91 forging produced at our Jiangyin facility undergoes rigorous quality testing to ensure compliance with international standards:

• Chemical composition analysis using spectrometer
• Microstructure examination and grain size analysis
• Tensile testing at room temperature and elevated temperatures
• Charpy V-notch impact testing
• Hardness testing (Brinell, Rockwell)
• Ultrasonic testing (UT) per ASTM A388
• Magnetic particle testing (MT) and liquid penetrant testing (PT)
• Dimension inspection and surface finish measurement

F91 Forging Manufacturing Process at Jiangsu Liangyi

Every F91 forging that leaves our Jiangyin facility is the product of an eight-stage integrated manufacturing process — from raw steel melting through to final documentation. Unlike trading companies that buy forgings from third-party mills and re-sell them, Jiangsu Liangyi controls the entire production chain in-house, giving our customers direct traceability from heat number to finished component.

F91 Forging Dimensional Capabilities at Jiangsu Liangyi

Our press and ring rolling capacity allows us to produce F91 forgings across the widest size range available from a single-source manufacturer in China. The table below summarises the maximum dimensions achievable for each product form:

For enquiries outside these ranges or for multi-piece forging assemblies, please contact our engineering team directly. We are experienced in sourcing oversized ingot material through our established mill relationships.

F91 Steel Welding Guidelines, Filler Metals and PWHT Requirements

One of the most common causes of premature failure in F91 components in service is not the base material itself — it is incorrect welding practice. F91 is classified as a weldable alloy, but "weldable" does not mean "forgiving." Every parameter in the welding cycle, from preheat to final PWHT cooling rate, has a direct impact on the long-term creep performance and fracture resistance of the welded joint. The guidelines below reflect current best practice per ASME Code Case 2328, EPRI TR-115524 and the accumulated knowledge of our engineering team from 25+ years of supplying F91 forgings to power plant fabricators worldwide.

Critical Welding Parameters

Recommended Filler Metals for F91 Welding

Post-Weld Heat Treatment — Why It Is Non-Negotiable for F91

Unlike carbon steel or low-alloy steels where PWHT is "recommended," for F91 it is absolutely mandatory with no exceptions. The reason is fundamental to the alloy's metallurgy: immediately after welding, the weld metal and heat-affected zone contain a mixture of untempered martensite and retained austenite. Untempered F91 martensite is extremely brittle (hardness can reach 450+ HBW) and susceptible to hydrogen-assisted cracking at ambient temperature. PWHT at 740–770 °C transforms this microstructure into a properly tempered martensite with the precipitate distribution required for creep performance, reduces residual welding stresses, and brings hardness within the code-permitted range (≤ 250 HBW).

A component that has been welded without PWHT, or with PWHT at an incorrect temperature, must be considered non-conforming and should be re-heat-treated (full normalise + temper) before entering service. Jiangsu Liangyi strongly recommends that all customer welding procedures and PWHT specifications be reviewed by a qualified metallurgical engineer before fabrication begins, and we are available to provide technical consultation at no charge to our F91 forging customers.

Type IV Cracking in F91 Welds — What Design Engineers Must Understand

Type IV cracking is the most technically important and operationally dangerous failure mode specific to 9% chromium martensitic steels including F91 and P91. Unlike weld metal cracking or fusion line defects — which are typically discovered during fabrication inspection — Type IV cracking develops slowly during high-temperature service, often becoming detectable only after 50,000–100,000 hours of operation, well into the design service life of the plant.

What Causes Type IV Cracking and Where It Occurs

The cracking occurs specifically in the fine-grained outer heat-affected zone (HAZ) — the narrow band of parent material that was heated to temperatures between the Ac1 transformation point (~820 °C) and approximately 1,000 °C during welding. In this zone, the prior-austenite grains are very fine (ASTM grain size 9–11) because only partial reaustenitisation occurred. During the subsequent PWHT, M₂₃C₆ carbides in this zone dissolve and reprecipitate in a coarser morphology that provides less effective creep strengthening than in the fully normalised parent metal. The result is a narrow band of reduced creep strength, bounded by stronger material on both sides, that concentrates creep strain until micro-voids nucleate on grain boundaries and eventually coalesce into a macro-crack parallel to the weld.

Risk Factors That Increase Type IV Susceptibility

• High welding heat input — wider HAZ means a larger volume of susceptible fine-grained material. Maintain heat input below 2.0 kJ/mm where possible.
• Operating temperature approaching the upper design limit — Type IV cracking accelerates significantly above 580 °C. Components operating at 600 °C continuously require careful inspection interval planning.
• Incorrect Al/N ratio in the parent metal — if aluminium content is too high (> 0.04%), it ties up nitrogen as AlN instead of allowing VN precipitation. This reduces the creep strength not only of the parent metal but also the HAZ.
• PWHT temperature drift — if PWHT is performed below 740 °C, the fine-grained HAZ is insufficiently recovered; above 800 °C, excessive grain growth occurs in other zones.
• Multi-pass repairs without full re-normalise — localized repair welding reintroduces a new HAZ adjacent to the repaired zone without changing the existing fine-grained HAZ, compounding the susceptibility.

How Jiangsu Liangyi Helps Mitigate Type IV Risk in the Base Material

While Type IV cracking is primarily a welding and fabrication issue, the quality of the F91 base material supplied to the fabricator plays a significant role in the ultimate susceptibility. At Jiangsu Liangyi we address this through:

• Strict aluminium control: We target Al < 0.030% in our F91 heats — below the ASTM maximum of 0.04% — to maximise the nitrogen available for VN precipitation in the HAZ.
• Verified grain size: Every heat is examined metallographically to confirm ASTM grain size ≥ 5 prior to supply. Coarse-grained starting material is more susceptible to HAZ embrittlement.
• Tight Nb/V/N balance verification: Spectrometer data for every heat is reviewed against ASTM A182 requirements and our internal alloy balance checklist before the heat is released for forging.
• Full heat treatment records: Documented normalise + temper records supplied with every MTC allow the fabricator to confirm the starting microstructure and calculate the correct PWHT parameters for their welding procedure.

F91 Forging Packaging, Export Documentation and Shipping from China

Proper packaging and logistics management are as important as manufacturing quality when it comes to receiving F91 forgings in good condition at your facility. Corrosion damage during ocean shipping, dimensional distortion from inadequate support, or documentation errors at customs can cause project delays that far exceed the value of the forging itself. At Jiangsu Liangyi, we treat packaging and export as an integral part of our manufacturing service, not an afterthought.

Surface Protection and Corrosion Prevention

Immediately after final dimensional inspection and before packaging, all F91 forged surfaces are cleaned by shot blasting or mechanical wire brushing to Sa 2 or St 3 standard, then coated with heavy-duty rust-preventive oil (a rust-preventive oil meeting DIN 51502 / ISO 6743-7 requirements (e.g., Castrol Rustilo DWX 30 or equivalent product)) applied by brush or dipping. Precision-machined surfaces receive an additional layer of VCI (Volatile Corrosion Inhibitor) film wrapping to prevent electrochemical corrosion in the moisture-laden ocean shipping environment. For components requiring long-term storage (> 6 months), wax-based compound coating is applied in addition to the VCI film.

Packaging Standards by Component Size

• Small parts (< 500 kg): Fully enclosed wooden boxes constructed from HT-certified timber (ISPM 15 compliant) are used for these parts, with foam cushioning, desiccant silica gel packs and moisture indicator cards. Maximum stack height is marked on the exterior of each box.
• Medium parts (500 kg – 5,000 kg): Open wooden crates with structural blocking and bracing are used for these parts to prevent movement during transit. Parts are individually wrapped in VCI film before placement in the crate. Lifting points are clearly marked and centre-of-gravity is indicated on the crate exterior.
• Large parts (> 5,000 kg): Heavy wooden skids with through-bolt blocking, steel banding and turnbuckle lashing are used for these parts. For parts that exceed 10 tonnes, we provide a lifting and rigging plan with centre-of-gravity calculations for safe handling at the destination port.

Port of Loading and Shipping Options

 Our Jiangyin factory is about 80 km away from Shanghai Yangshan Deep-Water Port, which is the biggest container port in the world. It is also about 60 km from Nanjing Port, which handles breakbulk and project cargo for big forgings. Because of this geographic advantage, our customers can choose the cheapest shipping method for the size of their order:

• FCL (Full Container Load): For orders filling one or more 20' or 40' containers. Most economical rate for volume orders.
• LCL (Less than Container Load): For smaller or sample orders. Consolidated with other cargo at the Shanghai consolidation hub.
• Breakbulk / Project Cargo: For forgings exceeding container limitations (e.g., rings over 3 m diameter or items over 25 tonnes). We work with specialised project cargo forwarders and have experience shipping to all major industrial ports worldwide.

Incoterms and Export Documents

We support all major Incoterms 2020: EXW (ex-works Jiangyin), FOB Shanghai or Nanjing, CFR, CIF (any destination port), and DAP (buyer's named destination). Every F91 shipment is accompanied by a complete documentation set including: Commercial Invoice, Packing List, Bill of Lading, EN 10204 3.1 Mill Test Certificate (3.2 available with customer-nominated independent inspector), Certificate of Origin (Form A GSP, RCEP or regular CO), Heat Treatment Records, NDE Reports (UT, MT, PT), and Dimensional Inspection Report. For nuclear power applications, additional documentation including Certified Design Documentation (CDD) and QA-level traceability records can be provided upon request.

Related High-Temperature Alloy Steel Forgings from Jiangsu Liangyi

If ASTM A182-F91 does not precisely match your temperature range, budget or application requirements, our manufacturing facility in Jiangyin produces the following complementary alloy steel grades to the same high standard of quality. All grades are available in the same product forms (bars, rings, hollow components, discs, machined parts) and are supplied with EN 10204 3.1 mill test certificates (3.2 available with customer-nominated inspector).

Not sure which grade is right for your application? Send us your service conditions (temperature, pressure, media, design code and required design life) and our engineering team will provide a material selection recommendation — at no cost and with no obligation to purchase.

Why Choose Jiangsu Liangyi as Your China F91 Forging Supplier?

Frequently Asked Questions about ASTM A182-F91 Forgings