Defining 1.7383 Steel
1.7383 is the European EN numeric designation for a chromium-molybdenum alloy structural steel engineered for long-term service at elevated temperatures. Its chemical designation under EN standards is 11CrMo9-10, and it is globally known as 2.25Cr-1Mo steel. It is standardised principally under EN 10222-2 for steel forgings for pressure purposes.
The grade belongs to the ferritic Cr-Mo steel family — alloys in which the combination of chromium (Cr) and molybdenum (Mo) creates a microstructure that resists creep, oxidation, hydrogen attack, and temper embrittlement at temperatures where plain carbon steel would rapidly degrade. 1.7383 has been one of the most widely specified forging grades in global power generation, petrochemical refining, and pressure vessel construction for more than five decades. Jiangsu Liangyi manufactures custom 1.7383 open die forgings and seamless rolled rings to EN 10222-2, ASTM A387, and API 6A standards, from 30 kg to 30,000 kg per piece.
The chemical designation code 11CrMo9-10 directly encodes the alloy's composition: a chromium content of approximately 9/4 ≈ 2.25 wt% and a molybdenum content of 10/10 = 1.0 wt% (European Cr-Mo steels apply a factor-of-four convention to the Cr digits). Engineers familiar with this naming scheme can read the alloy balance at a glance without referencing a data sheet.
Chemical Composition of 1.7383 (11CrMo9-10) Steel
The precise compositional limits of 11CrMo9-10 / 1.7383 are defined under EN 10222-2:2017 for pressure purpose forgings. The full permitted range by mass percentage is shown below:
| Element | Symbol | Min wt% | Max wt% | Primary Role |
|---|---|---|---|---|
| Carbon | C | 0.08 | 0.15 | Base strength; limited to preserve weldability and toughness |
| Silicon | Si | — | 0.50 | Deoxidisation; minor solid-solution strengthening |
| Manganese | Mn | 0.40 | 0.80 | Hardenability and impact toughness control |
| Phosphorus | P | — | 0.025 | Impurity — limited to prevent temper embrittlement |
| Sulphur | S | — | 0.010 | Impurity — low limit preserves ductility |
| Chromium | Cr | 2.00 | 2.50 | Oxidation resistance; high-temperature strength; H₂ barrier |
| Molybdenum | Mo | 0.90 | 1.10 | Creep resistance; elevated-temperature solid-solution strengthening |
| Aluminium | Al | — | 0.020 | Grain-size control and deoxidation |
| Copper | Cu | — | 0.30 | Residual — limited to avoid hot shortness |
| Nickel | Ni | — | 0.30 | Residual element |
Why Chromium and Molybdenum Are the Key Elements
The joint action of Cr and Mo is the scientific foundation of this grade's performance. Chromium forms a protective Cr₂O₃ surface oxide that retards oxidation in steam and flue-gas environments, and provides a barrier to hydrogen corrosive attack at grain boundaries. At the microstructural level, Mo atoms substituted into the iron lattice impede dislocation climb — the primary mechanism of creep deformation — by raising the activation energy required for atomic diffusion. The combined result is a steel that retains strength and dimensional stability at loads that would rapidly deform plain carbon steel at the same temperature.
The tight phosphorus limit (≤ 0.025 wt%) in 1.7383 is not arbitrary. Phosphorus segregates to grain boundaries during slow cooling and dramatically accelerates temper embrittlement — a progressive loss of impact toughness during long-term service between 370–560 °C. Specifying low-P heats is therefore essential for equipment designed for 100,000-hour operational lifetimes in power or refinery service.
Mechanical Properties of 1.7383 at Room and Elevated Temperature
Minimum guaranteed mechanical properties for 1.7383 forgings in normalised-and-tempered (N+T) or quenched-and-tempered (Q+T) condition, per EN 10222-2:
| Property | Symbol | Condition | Min / Range | Unit |
|---|---|---|---|---|
| Tensile strength | Rm | N+T or Q+T | 520 – 670 | MPa |
| 0.2% Proof stress | Rp0.2 | N+T or Q+T | ≥ 310 | MPa |
| Elongation | A | Longitudinal | ≥ 18 | % |
| Reduction of area | Z | Longitudinal | ≥ 50 | % |
| Charpy impact (KV) | KV | +20 °C | ≥ 40 | J |
| Brinell hardness | HBW | Annealed | ≤ 220 | HBW |
High-Temperature Proof Stress (Rp0.2 vs Temperature)
For pressure equipment design, the proof stress at operating temperature is a critical parameter. The values below, per EN 10222-2 Annex, show that 1.7383 retains meaningful structural strength all the way to its 550 °C service ceiling:
At 550 °C, 1.7383 still delivers a minimum proof stress of 120 MPa. Plain carbon steel at the same temperature retains roughly 60–80 MPa and creeps rapidly under sustained load. That 50–100% structural advantage is precisely what makes 2.25Cr-1Mo the global standard material for boiler drums and high-pressure vessel walls in power plants and refineries.
Heat Treatment of 1.7383 (11CrMo9-10) Forgings
The final mechanical properties and long-term microstructural stability of 1.7383 forgings are established through a controlled heat treatment sequence applied after hot forging. The five-step production flow is:
All welded assemblies incorporating 1.7383 / 11CrMo9-10 require mandatory PWHT at 690–750 °C. Skipping PWHT leaves residual stresses and hard heat-affected zones that accelerate hydrogen-induced cracking in service. PWHT is not optional for pressure equipment regulated under PED 2014/68/EU or ASME Boiler and Pressure Vessel Codes.
1.7383 / 11CrMo9-10 International Equivalent Grades
1.7383 (11CrMo9-10) has near-equivalent designations in all major global standards systems. Understanding this cross-reference is essential for international procurement, domestic stock substitution, and interpreting specifications issued under different national codes:
11CrMo9-10
F22
SA-182 F22
Grade F22
While these designations share the 2.25Cr-1Mo nominal composition, specific limits for carbon, phosphorus, sulphur, and heat treatment conditions differ between standards. Always verify the exact compositional range and mechanical requirements from the applicable standard before approving a substitution, particularly for PED- or ASME-regulated pressure equipment.
Why 1.7383 Excels in High-Temperature, High-Pressure Service
Creep Resistance
Creep — the slow, time-dependent deformation of a material under sustained load at elevated temperature — is the dominant failure mode for pressure components above 400 °C. Molybdenum atoms in solid solution impede dislocation climb (the primary creep mechanism) by raising the activation energy for diffusion at grain boundaries. For 1.7383, the 100,000-hour creep rupture strength at 500 °C is approximately 90 MPa — enabling reliable design of components operating continuously for 30-year plant lifetimes.
High-Temperature Hydrogen Attack (HTHA) Resistance
In refinery hydrogen service, atomic hydrogen diffuses into steel at elevated temperature and reacts with carbon to form methane (CH₄). The methane gas cannot diffuse out, accumulates at grain boundaries, and ultimately causes brittle fracture — this is High Temperature Hydrogen Attack (HTHA). The API RP 941 Nelson Curves show 2.25Cr-1Mo steel operating safely at substantially higher temperature–H₂ partial pressure combinations than plain carbon steel, because chromium stabilises carbides against decarburisation and reduces the driving force for HTHA.
Steam Oxidation Resistance
In boiler and steam turbine environments, 1.7383 forms a stable, adherent Cr₂O₃-rich oxide scale rather than the porous, exfoliating Fe₃O₄ that forms on carbon steel. This scale reduces the rate of metal loss and prevents oxide particle exfoliation into turbine blades or heat exchanger tubes — a significant operational reliability benefit in supercritical and ultra-supercritical power plant design.
Temper Embrittlement Resistance
Long-term operation in the 370–560 °C range can cause temper embrittlement through grain boundary segregation of phosphorus. The tight P limit (≤ 0.025 wt%) mandated in 1.7383 specifications directly mitigates this risk. Components exposed to this temperature range for extended periods should be subjected to Step Cooling tests per ASTM A1038 during material qualification.
Weldability of 1.7383 Steel
With a carbon equivalent (CE) of approximately 0.62–0.75 using the IIW formula, 1.7383 is classified as conditionally weldable. Successful welding requires: preheat to minimum 200 °C, low-hydrogen welding processes, controlled interpass temperature, and mandatory PWHT. When these conditions are met, weld integrity matching base material specification is achievable with matching ER90S-B3 (GMAW/GTAW) or E9015-B3 (SMAW) consumables.
1.7383 / 11CrMo9-10 Industrial Applications
The unique combination of high-temperature strength, creep resistance, hydrogen resistance, steam oxidation resistance, and conditional weldability makes 1.7383 the material of choice — or a mandatory specification — across multiple critical industries:
Verified Project Case Study
Jiangsu Liangyi Co., Limited supplied 1.7383 forged tube sheets, channel flanges, and pressure vessel shells to a 600 MW thermal power plant in Southeast Asia. These forgings were qualified for continuous service at 550 °C under high steam pressure and have been in uninterrupted operation since commissioning — a real-world validation of the grade's long-term reliability under sustained maximum-service-temperature conditions.
1.7383 forgings from Jiangsu Liangyi are produced to EN 10222-2, ASTM A387, and DIN international standards, with full material traceability and quality documentation. Our ISO 9001 quality management system governs the full production process. Independent third-party inspection can be arranged at the customer's request — buyers typically specify their preferred accredited inspection body at order stage.
1.7383 vs Adjacent Cr-Mo Steel Grades
| Grade | Cr % | Mo % | Max Temp (°C) | Creep at 500°C | Best Application |
|---|---|---|---|---|---|
| P265GH (Carbon Steel) | — | — | ~400 | Low | Low-temperature pressure vessels |
| 1CrMo (1.7335 / 13CrMo4-5) | ~1.0 | ~0.5 | ~530 | Moderate | Intermediate boiler steels |
| 1.7383 / 11CrMo9-10 ◀ This Grade | 2.25 | 1.0 | 550 | ~90 MPa | Boilers, pressure vessels, reactors, turbines |
| 1.4903 / X10CrMoVNb9-1 (P91) | ~9.0 | ~1.0 | ~620 | Very high | Ultra-supercritical power plant |
Indicative values for comparison only. Always consult the applicable standard for design-critical property values.
1.7383 occupies a well-defined performance niche: superior to plain carbon and low-alloy steels in all elevated-temperature properties, yet significantly more economical and weldable than higher-chromium grades such as P91 (1.4903). For most pressure equipment operating below 560 °C, 1.7383 represents the optimal balance of performance and cost.
For applications requiring operation above 560 °C or demanding higher creep rupture strength, our 1.4903 / X10CrMoVNb9-1 (P91) forging parts may be the appropriate next-grade selection.
Custom 1.7383 Forging Products from Jiangsu Liangyi
As an ISO 9001 certified forging manufacturer in Jiangyin, Jiangsu Province — China's core forging industry cluster — we manufacture the complete range of 1.7383 / 11CrMo9-10 forged components. Full product details, dimensional capabilities, and RFQ are available on our dedicated 1.7383 forging parts — bars, rings, shafts and hollow forgings.
| Product Category | Shapes & Forms | Max Dimension | Weight Range |
|---|---|---|---|
| Forged Bars & Shafts | Round bars, flat bars, step shafts, turbine shafts, pump shafts, valve spindles, gear shafts | Length ≤ 12 m | 30 kg – 15,000 kg |
| Seamless Rolled Rings | Turbine guide rings, gear rings, seal rings, labyrinth rings, swivel flanges, valve seat rings | OD ≤ 5 m | 30 kg – 20,000 kg |
| Hollow Forgings & PV Components | Tube sheets, channel flanges, shells, sleeves, barrel forgings | As specified | 30 kg – 30,000 kg |
| Blocks, Discs & Plates | Forged discs, blocks, plates, fluid end blocks, adapter blocks | Single piece | Up to 30,000 kg |
All forgings are produced with a minimum reduction ratio of 3:1, full-process traceability from ingot smelting through final machining, and comprehensive NDT inspection (UT, MT, RT, PT) with third-party certification available. Lead time is typically 25–35 working days from drawing confirmation, with a minimum order quantity of one piece.
1.7383 Steel — Frequently Asked Questions
1.7383 Steel — Key Facts at a Glance
1.7383 / 11CrMo9-10 / 2.25Cr-1Mo is a precisely engineered, high-performance alloy for high-temperature, high-pressure industrial applications.
| Parameter | Value / Description |
|---|---|
| Primary standard | EN 10222-2 (pressure forgings) |
| Alternate standard | ASTM A387 / ASME SA-387 |
| Max service temperature | 550 °C continuous |
| Chromium content | 2.00 – 2.50 wt% |
| Molybdenum content | 0.90 – 1.10 wt% |
| Tensile strength (RT) | 520 – 670 MPa |
| Proof stress (RT) | ≥ 310 MPa |
| Proof stress at 500°C | ≥ 155 MPa |
| ASTM equivalent | A387 Grade 22 / F22 |
| Weldability | Conditional — preheat ≥ 200°C + PWHT required |
| Max ring OD | 5 m |
| Max bar length | 12 m |
| Weight range | 30 kg – 30,000 kg per piece |