26NiCrMoV11-5 (1.6948) Forging Parts

Jiangsu Liangyi Co., Limited, established in 1997 and strategically located in Chengchang Industry Park, Jiangyin City, Jiangsu Province, is a professional ISO 9001:2015 certified manufacturer of premium 26NiCrMoV11-5 (1.6948) open die forging parts in China. We have over 25 years of experience of the forging industry and have supplied thousands of tons of high-quality 26NiCrMoV11-5 forged parts to satisfied customers in more than 50 countries across Asia, Europe, North America, South America, Africa and Oceania.

Material Advantages of 26NiCrMoV11-5 Steel

26NiCrMoV11-5, also designated by the European material number 1.6948, is a premium low-alloy Ni-Cr-Mo-V engineering steel with excellent performance for important high-temperature and high-stress service conditions. Compared with conventional alloy steels including AISI 4140 and AISI 4340, 26NiCrMoV11-5 presents distinct technical superiorities:

• Superior high-temperature strength: Maintains excellent tensile strength and yield strength at operating temperatures up to 550°C
• Outstanding low-temperature toughness: Excellent Charpy V-notch impact resistance even at sub-zero temperatures
• Exceptional hardenability: Through-hardening capability for large-section parts up to 30 tons
• Excellent fatigue resistance: Superior fatigue life for rotating machinery parts
• High creep resistance: Excellent creep properties for long-term high-temperature service
• Good machinability: Balanced composition for efficient machining while keeping properties

These unique metallurgical properties make 26NiCrMoV11-5 (1.6948) the premium material choice for mission-critical parts in power generation, oil & gas, marine, and heavy machinery industries where absolute reliability, durability and performance are non-negotiable requirements.

At our state-of-the-art 80,000 m² manufacturing site in Jiangyin, we are fully capable of producing 26NiCrMoV11-5 (1.6948)  forged parts in a wide range of shapes and dimensions, fully customized to your engineering specifications and technical drawings. Following are our full production scope covers all types of open die forgings and seamless rolled rings:

Specialized Turbine & Rotating Parts

Our main technical expertise and competitive advantage lies in manufacturing high-precision 26NiCrMoV11-5 turbine parts for demanding power generation applications:

• Gas turbine rotor shafts (monobloc and built-up construction)
• Steam turbine rotor shafts (HP, IP and LP sections)
• High pressure (HP) and intermediate pressure (IP) turbine rotors
• Generator shafts and turbine shaft ends
• Turbine blades, vanes and guide vanes
• Valve spindles, stems, rods and valve seats
• Packing seals, diaphragms and rotor end rings
• Double-headed studs, bolts and critical fasteners
• Couplings, flanges and connection parts

We have modern equipment in our factory, such as cutting-edge forging, machining and heat treatment equipment so that we can produce large-scale 26NiCrMoV11-5 (1.6948) forged parts with excellent precision, consistent quality and reliable performance:

• Maximum single-piece forging weight: Up to 30 tons per individual forging
• Maximum length capacity: Up to 15 meters for turbine rotor shafts
• Maximum diameter capacity: Up to 2 meters for shafts and 6 meters for seamless rolled rings
• Annual production capacity: 120,000 tons of premium forged steel products
• Facility size: 80,000 square meters of modern manufacturing space
• Fixed asset investment: Over 40 million USD in specialized equipment

Raw Material Production Process

We keep complete control over the entire production value chain from initial steel melting to final inspection and packaging, guaranteeing the highest quality standards for our 26NiCrMoV11-5 products. Our premium raw material is produced using state-of-the-art melting and refining processes:

• Basic Electric Arc Furnace (EAF) primary melting
• Ladle Furnace (LF) secondary refining
• Argon Oxygen Decarburization (AOD) for stainless grades
• Vacuum Oxygen Decarburization (VOD) for ultra-low carbon grades
• Vacuum Degassing (VD) for hydrogen removal
• Electroslag Remelting (ESR) - available upon client request for ultra-high purity critical applications

26NiCrMoV11-5 Heat Treatment Process — Full Engineering Detail

 Heat treatment serves as the decisive process in defining the final mechanical properties of 26NiCrMoV11-5 forged parts. Unlike conventional low-alloy steels, this grade needs highly precise thermal cycling owing to its elevated nickel content. The alloy’s high nickel composition alters the martensite start (Ms) temperature, necessitating controlled cooling rates to prevent retained austenite formation and mitigate temper embrittlement risks. Outlined below is the complete heat treatment sequence implemented at Jiangsu Liangyi, refined through over 25 years of practical production expertise with this specialized steel grade.

Step 1 — Preliminary Soft Annealing (Optional, Pre-Machining)

 For large-section forgings scheduled for rough machining before final heat treatment, a soft annealing process is performed to lower hardness and improve machinability. The treatment is carried out at 650–710°C with a soaking hold of 4 to 6 hours, followed by slow furnace cooling at a maximum rate of 20°C/h until the temperature drops below 300°C. This preliminary step is unnecessary for parts supplied in the quenched and tempered (Q+T) delivery condition.

Step 2 — Preliminary Normalizing (Grain Refinement)

Large-section forgings with a diameter over 500 mm or a weight exceeding 5 tons undergo a normalizing process prior to final quenching and tempering (Q+T). This step eliminates banded microstructures induced by forging, establishing a uniform, fine-grained austenitic base structure.Process parameters: heating temperature 870–920°C (typical at 890°C), with a minimum soaking time of 1 hour per 100 mm of important section thickness, followed by air cooling to ambient temperature.

Step 3 — Austenitizing / Hardening

 This represents the most important stage of the process. The forging is heated to the austenitizing temperature to fully dissolve carbides and form a homogeneous austenite matrix. For 26NiCrMoV11-5, the optimal austenitizing range is 840–880°C, with 860°C adopted as our standard target temperature for turbine rotor shafts. Excessively high austenitizing temperatures will coarsen prior austenite grains and degrade impact toughness. This risk needs strict control, as the steel features a low maximum silicon content of 0.15%, which inherently restricts its resistance to high-temperature grain growth.

Holding time guideline: Minimum 1 hour per 25mm of effective cross-section thickness, with an absolute minimum of 3 hours for sections above 500mm. For a 1,000mm diameter rotor shaft this typically means 10–12 hours at temperature before quenching commences.

Step 4 — Quenching

Quenching medium is chosen based on section size to get adequate through-hardening while controlling the risk of quench cracking — a genuine concern for large Ni-Cr-Mo-V forgings:

• Sections ≤ 250mm diameter: Oil quenching (60–80°C bath temperature). Fastest cooling, maximum hardness gradient, suitable for smaller parts.
• Sections 250–600mm diameter: Accelerated oil quenching or water-polymer solution (5–8% polymer concentration). Balances hardening depth with thermal stress management.
• Sections > 600mm diameter (turbine rotors): Water-polymer spray quenching or controlled water immersion.The high Ni content (2.40–3.10%) of 26NiCrMoV11-5 makes it very hardenable, so it can be hardened all the way through even in sections that are 1,000mm or more thick.

Immediately after quenching, the forging surface temperature is monitored and the part must be transferred to the tempering furnace while still warm (above 80°C) to avoid cold cracking caused by high transformation stresses in the martensitic structure.

Step 5 — Double Tempering (Standard Practice for Turbine Rotors)

Single tempering is adopted as standard for general engineering parts. For turbine rotor shafts and other important-duty parts, however, Jiangsu Liangyi implements double tempering  as a mandatory standard procedure. The first tempering cycle tempers as-quenched martensite and relieves high residual transformation stresses. The second cycle further tempers any fresh martensite generated during cooling after the first tempering step, yielding a fully stabilized, uniformly tempered martensite microstructure across the full cross‑section of the forging.

• First Tempering: 580–650°C, hold 2h per 25mm of effective section (minimum 6 hours for rotors), furnace cool to below 300°C
• Second Tempering: Same temperature as first tempering ±10°C, same holding time, air or furnace cool

Tempering temperature serves as the main parameter governing the final balance of strength and toughness. Elevated tempering temperatures (630–650°C) marginally lower tensile strength while delivering substantial improvements in Charpy impact properties and minimizing the risk of temper embrittlement. This control is especially vital for 26NiCrMoV11-5, as the material is prone to reversible temper embrittlement (RTE) when slowly cooled through the important temperature range of 375–575°C after tempering.

Step 6 — Post-Machining Stress Relieving

 After rough machining, a stress‑relief annealing treatment at 550–600°C , held for 4–8 hours according to section thickness, is recommended to delete residual machining stresses prior to final precision machining. This effective measure prevents dimensional distortion during finishing operations and removes localized stress concentrations that may initiate fatigue cracking under service conditions. Crucially, the stress‑relief temperature must be maintained at least 30 °C below the final tempering temperature, so as to avoid unintended softening and degradation of the base material’s mechanical properties.

The following table specifies the standard chemical composition (weight percentage) of 26NiCrMoV11-5 forged gas turbine rotor shafts according to EN 10083-3 European standard. Our rigorous quality control makes sure every heat meets or exceeds these specifications:

 One of the most common inquiries from international procurement engineers concerns the cross-standard equivalent of 26NiCrMoV11-5 under local national specifications. This poses a genuine engineering challenge, as 26NiCrMoV11-5 (1.6948) is a European-grade steel defined in EN 10083-3 (formerly DIN 17200), with no direct, one-to-one equivalent in other global material standards. The table below lists the closest approximate alternatives, matched by comparable chemical composition and typical service applications, rather than precise identical specifications.

Main Engineering Reminder: When you use cross-standard material substitution, please check if the alternative grade meets the specific mechanical property thresholds, heat treatment compatibility, and needed inspection criteria. Even alloys that are nominally the same have different composition limits and minimum guaranteed performance values across different standards. These differences must be fully reviewed for important part applications.

Our recommendation for international procurement:  When sourcing26NiCrMoV11-5 (1.6948) forgings from Jiangsu Liangyi, please specify the material by its official EN designation — either 26NiCrMoV11-5 or 1.6948 — together with the required mechanical property class and applicable project standard. This practice eliminates cross‑standard ambiguity and makes sure all quality documentation fully aligns with your engineering specifications and inspection protocols.
All material test certificates are issued based on EN 10083-3 as the primary governing standard. Cross-references to regional or national standards can be additionally annotated on documentation upon customer request.

The following mechanical properties are obtained after proper quenching and tempering heat treatment for 26NiCrMoV11-5 forged steam turbine rotor shafts. All properties are verified through rigorous mechanical testing in our certified laboratory:

The mechanical property table alone cannot satisfy detailed engineering design needs. Structural analysts, FEA engineers and thermal engineers need a complete set of physical and thermal parameters to accurately simulate part performance under combined mechanical and thermal loads — the actual service working conditions of turbine rotors.
The following data are measured from our in-house laboratory testing, consistent with official technical data stipulated in EN 10083-3 for quenched and tempered delivery conditions. All parameters are temperature-dependent; linear interpolation is recommended for intermediate temperature working scenarios.

Physical Properties at Room Temperature (20°C)

Thermal Properties vs. Temperature

For turbine rotor design, the temperature-dependent characteristics of thermal conductivity and thermal expansion coefficient are especially critical. These parameters directly govern thermal gradient distribution and the resultant thermal stresses experienced during transient start‑up operations. The following property values are measured for the material in its quenched and tempered condition:

Design Note from our Engineering Team: A frequent oversight in turbine rotor design is assuming constant material properties throughout the full operating temperature range. For 26NiCrMoV11-5, Young’s modulus decreases by approximately 20% from ambient temperature to 550°C, falling from around 210 GPa to 168 GPa. This temperature-driven reduction directly impacts critical speed calculations. Engineers relying solely on room-temperature modulus values for high-temperature critical speed analysis tend to overestimate critical speed by about 10–11%. Such deviation creates substantial safety margin risks, especially for rotating equipment operating close to critical speed during transient start-up and load change cycles. For accurate rotor dynamic assessment and reliable long-term operational safety, temperature-dependent material property data must always be adopted.

 Choosing the right turbine rotor steel is one of the most important engineering decisions when designing a power plant. Picking the wrong material can cause early creep, fatigue failure, or not enough toughness at operating temperature — all of which have serious safety and operational results. This section gives an honest, technically thorough comparison of 26NiCrMoV11-5 (1.6948)  and the most commonly used alternative grades, based on our direct experience making all these materials.

Which Grade Should You Choose? — A Practical Decision Framework

Based on our experience manufacturing all of these grades, here is the honest decision framework we share with our customers' engineers:

Choose 26NiCrMoV11-5 (1.6948) when: If your turbine or rotating equipment runs at 450–550°C, needs strong full-depth hardening for large-size parts over 400mm in diameter, needs great low-temperature toughness for cold or cryogenic working conditions, or needs official EN standard paperwork, this grade is the best option. Its high nickel content from 2.40% to 3.10% is its main strength, delivering unmatched hardening ability and toughness that standard turbine rotor steel grades cannot equal, especially for extra large cross-section parts.

Choose 30CrMoNiV5-11 (1.6946) when: operating temperatures stay above 550°C or near 580°C, and the working scene needs better high-temperature creep strength. More chromium and vanadium help keep the part stable at high heat, but cut down nickel content, which weakens its toughness in low-temperature environments.

Choose 34CrNiMo6 (1.6582) when: the application is a general engineering shaft, gear or structural parts operating below 450°C, and the cost differential of 26NiCrMoV11-5's high nickel content is not justified by the application requirements. This is a common and economical choice for industrial gearbox shafts, crane parts and heavy machinery.

Choose 9–12% Cr steels (such as X12CrMoWVNbN10-1-1) when: operating temperatures go above 580°C in ultra-supercritical (USC) steam turbines, where high-chromium ferritic steels are needed for better oxidation resistance. The downside is much lower strength and hardening performance, which calls for careful design work to guarantee solid material properties at the inner bore of large rotor parts.

 26NiCrMoV11-5 steel is widely used for extreme industries globally because it has excellent high strength, toughness, heat resistance and fatigue properties. Following are some of our successful application case studies from satisfied customers around the world:

At Jiangsu Liangyi, uncompromising quality is embedded in every single stage of our production process. All our 26NiCrMoV11-5 (1.6948) forged parts are given rigorous and full quality control procedures from initial raw material inspection through to final testing, protective coating and secure packaging.

Comprehensive Quality Control Process

• Raw material chemical composition analysis using spectrometry
• 100% ultrasonic testing (UT) per ASTM A388 and EN 10228 standards
• Magnetic particle testing (MT) and liquid penetrant testing (PT)
• Full mechanical property testing (tensile, impact, hardness)
• Metallographic examination and grain size analysis
• High-temperature mechanical testing (when specified by client)
• Dimension test and precision machining verification
• Final visual inspection and surface quality assessment

Our Certification

Jiangsu Liangyi holds the following quality management certification:

• ISO 9001:2015 — Quality Management System certification, covering design, manufacturing, inspection and delivery of open die forgings and seamless rolled rings

Material Test Certificate Types We Issue

For every shipment of 26NiCrMoV11-5 forged parts, we issue material test certificates documenting full traceability of chemical composition, heat treatment records and mechanical test results:

• EN 10204-3.1 — Manufacturer's Inspection Certificate (standard): Issued and signed by our own authorized quality representative. Included as standard with all orders. Covers chemical analysis, mechanical properties, heat treatment records and dimensional data.
• EN 10204-3.2 — Third-Party Witnessed Inspection Certificate (on request): Outside third-party inspectors watch all testing work at our factory and sign material papers together with our in-house quality staff. We fully support third-party checks and make the whole process easy for buyers. Customers can choose their own inspection company, and we will fully arrange site access, testing times and on-site witness work.

Third-Party Inspection — How It Works

We regularly cooperate with independent inspection groups chosen by our customers. These teams visit our factory to watch all material tests and issue their own inspection reports. Well‑known groups that have completed on-site checks at our Jiangyin site include TÜV, Bureau Veritas (BV), DNV, ABS, Lloyd's Register (LR) and RINA. It should be noted that we offer third-party inspection support as a customer service, and we do not hold standalone certification from these organizations. If your contract or project rules need a certain inspection provider, please tell us when you send your inquiry, and we will check and confirm available scheduling.

Important note for procurement teams: If your project specification needs a named classification society or inspection body (such as DNV, BV, ABS or LR), please specify this clearly in your purchase order. We will confirm availability and coordinate the inspection visit. Any costs associated with third-party inspection agency fees are typically for the buyer's account unless otherwise agreed in the commercial terms.

 As a top maker of 26NiCrMoV11-5 forged parts based in Jiangyin, China, we have built fast and stable global shipping routes. This lets us deliver our high-quality forged goods to customers around the world on time and with full reliability.

• Standard production lead time: 4-8 weeks for standard products, 8-12 weeks for custom engineered parts
• Expedited delivery service: Available upon request for urgent customer orders
• Professional export packaging: Standard seaworthy export packaging with full rust prevention and shock protection
• Convenient shipping ports: Shanghai, Ningbo, Qingdao and other major Chinese international ports
• Flexible shipping methods: Sea freight, air freight and land transportation options
• Door-to-door delivery service: Available to most countries worldwide
• Export documentation: Complete set of export documents including commercial invoice, packing list, bill of lading, certificate of origin, etc.

We partner exclusively with leading international logistics companies to make sure that your valuable 26NiCrMoV11-5 forged parts arrive safely, securely and on schedule, no matter where you are located globally.