What Is 1.7380 (10CrMo9-10) Steel?
A Complete Guide for Engineers

Grade Overview: 1.7380 (10CrMo9-10) Steel

1.7380 — universally recognized by its chemical designation 10CrMo9-10 and its global shorthand 2.25Cr-1Mo — is a low-alloy chromium-molybdenum pressure steel that has been a cornerstone of high-temperature industrial engineering for more than six decades. It belongs to the Cr-Mo steel family standardized under European pressure vessel and boiler codes, and finds its defining use in components that must retain structural integrity at continuous service temperatures between 450 °C and 600 °C.

The alloy achieves its elevated-temperature capability through two metallurgical mechanisms. Chromium, at approximately 2.0–2.5 %, builds a coherent oxide film that resists scaling in steam, flue gas, and hydrogen atmospheres. Molybdenum, at 0.90–1.10 %, strengthens the ferritic matrix by solid-solution hardening and stabilizes fine carbide precipitates that impede grain-boundary creep deformation at temperature. Together they deliver a material genuinely suited to long-term service in boilers, superheaters, pressure vessels, and process piping.

Unlike cast steel in the same alloy system, 1.7380 (10CrMo9-10) forged parts offer a refined directional grain structure, higher density, and improved resistance to hydrogen attack — qualities that matter in heavy-wall pressure vessels and critical valve bodies where integrity over a 100,000-hour design life is non-negotiable. This guide focuses on 1.7380 as it is produced in the forged condition.

International Designations & Equivalents

1.7380 carries multiple cross-referencing designations across national standards bodies. Using the wrong designation in a procurement document — for example, confusing 10CrMo9-10 with the adjacent 11CrMo9-10 (1.7383) — represents a real compositional shift that must be caught at the specification stage. The table below maps the most common designations engineers encounter.

Chemical Composition (EN 10028-2:2009)

The limits below are from EN 10028-2:2009, the governing European specification for this grade. Forging manufacturers working to EN 10222-2 or EN 10269 apply the same elemental limits with additional product-analysis tolerances for individual heats. The "Typical %" column reflects Jiangsu Liangyi production chemistry; actual heat chemistry appears on the EN 10204 mill test certificate (MTC).

Why Carbon Is Kept Below 0.14 %

Higher carbon in Cr-Mo alloys increases as-quenched hardness and raises the risk of cold cracking during welding. The 0.14 % C upper limit keeps the carbon equivalent (CE) at a level where preheating to 150–200 °C plus PWHT is sufficient for most fabrication scenarios. This weldability-conscious composition is a key practical advantage of 1.7380 over higher-strength grades such as P91, which require significantly more demanding preheat, inter-pass temperature control, and PWHT procedures.

The Role of Molybdenum in Long-Term Service

At 500–600 °C, carbides in Cr-Mo steels tend to coarsen over time — a process called spheroidization — progressively reducing creep resistance. Molybdenum at 0.90–1.10 % significantly retards this by forming stable M₂C and M₆C carbides that resist coarsening over 100,000-hour design lives. This microstructural stability is why 10CrMo9-10 has remained a trusted and code-supported material in power plant applications for decades without being replaced by more exotic alloys.

Mechanical Properties of 1.7380 Steel

The values below apply to forgings in the normalized and tempered (N+T) delivery condition, as required by EN 10028-2 and EN 10222-2 for pressure-bearing components. Section size measurably affects achievable mechanical properties in large forgings: the geometric center of a heavy drum nozzle or tube sheet will have lower cooling rates than a thin disc, leading to a coarser microstructure. Reputable forging manufacturers verify center properties with embedded thermocouples and test specimens taken from code-specified sampling positions.

Elevated-Temperature Yield Strength Reduction

One of the most critical datasets for pressure vessel and boiler designers is the yield strength (Rp0.2) reduction profile as service temperature rises. Unlike plain carbon steels that drop sharply above 300 °C, 10CrMo9-10 retains useful strength to 600 °C, which is why it is specified for the hottest zones of subcritical boiler systems.

Elevated-Temperature Performance & Creep Data

In most pressure vessel and boiler design codes, components operating above 370 °C are governed by creep-rupture strength rather than short-term yield strength. Creep is the time-dependent, irreversible deformation of a metal under sustained stress at elevated temperature. Design codes set allowable stresses based on whichever is more restrictive: the stress producing 1 % total creep strain in 100,000 hours, or the mean stress to rupture in 100,000 hours divided by a safety factor.

Temper Embrittlement in Long-Term Service

An elevated-temperature service phenomenon engineers must understand is temper embrittlement — a gradual reduction in notch toughness that occurs when the steel is held in or slowly cooled through the 370–560 °C range over long service periods. This does not affect short-term tensile or yield strength but can significantly reduce Charpy impact energy in material removed from service after extended operation, making post-service inspection and weld repair more hazardous. Modern 1.7380 produced to EN 10028-2 addresses this through tight Mn + P + Si + Sn chemistry controls (the X-bar value). For long-term elevated-temperature service, buyers should confirm heats carry X-bar data on the mill test certificate where required by the applicable design code.

Heat Treatment of 1.7380 (10CrMo9-10) Forgings

Correct heat treatment is inseparable from the mechanical properties that make 10CrMo9-10 fit for high-temperature pressure service. Unlike tool steels where hardness is the primary objective, Cr-Mo pressure steels are heat treated to achieve a precise balance of strength, toughness, and microstructural stability under long-term thermal loading.

Standards & Compliance Framework for 1.7380

10CrMo9-10 forgings for pressure equipment are governed by a layered framework of material specifications, product standards, and design codes. Understanding which standard covers which aspect of the supply chain prevents dangerous specification gaps between what is ordered, what is manufactured, and what a code requires.

Forging Considerations for 1.7380 Steel

The decision to specify forged rather than cast or wrought-and-cut 10CrMo9-10 components is driven by measurable structural integrity differences that are particularly significant in pressure-bearing and high-temperature service environments.

Why Forging Improves the Material

Cast Cr-Mo steel contains dendrite segregation, shrinkage porosity, and coarse columnar grains from solidification. Open-die forging at temperatures above the recrystallization range (hot-working range for 1.7380: 1050–1250 °C) mechanically breaks down this cast structure, closes porosity, refines grain size, and aligns grain flow with the stress-bearing geometry of the finished component. The result is a material with markedly superior through-thickness toughness, better fatigue resistance under cyclic loading, and — critically for high-temperature service — more uniform and reproducible creep behavior.

A minimum forging ratio of 3:1 (the ratio of ingot cross-sectional area to finished forging cross-section) is the industry-accepted threshold to confirm cast structure is fully broken down. At Jiangsu Liangyi, all 1.7380 forgings are produced with a forging ratio ≥ 3:1 as a standard process requirement, documented in the forging process record delivered with each order.

Available 1.7380 Forging Products

• Open-die forged round bars and step shafts — for valve spindles, pump shafts, turbine rotor sections; up to 12 m length
• Seamless rolled rings — for turbine guide rings, pressure vessel nozzle flanges, seal rings, gear rings; OD up to 5 m
• Forged discs and blanks — for tube sheets, pressure vessel end caps, boiler drum sections; weight up to 30,000 kg single piece
• Forged blocks and slabs — for large reactor body sections and heavy valve bodies
• Custom near-net-shape forgings — profile-forged to minimize machining stock on complex geometries, reducing both lead time and material waste

For full dimensions, weight range, available product forms, certifications, and lead times, see the custom 1.7380 forgings product page, where you can also submit a drawing for a quotation.

Weldability & Post-Weld Heat Treatment (PWHT)

10CrMo9-10 is considered weldable with appropriate precautions, but requires a more disciplined procedure than lower-alloy grades like 13CrMo4-5 (1.7335). The relatively low carbon content (max 0.14 %) keeps the carbon equivalent at a manageable level, but the 2.25 % Cr raises the hardenability of the heat-affected zone (HAZ) enough that uncontrolled cooling from the weld thermal cycle can produce hard, hydrogen-crack-susceptible microstructures.

Preheating Requirements

A minimum preheat of 150–200 °C is required for sections above 12 mm; heavier sections above 50 mm typically require 200–250 °C. Preheat maintains the inter-pass temperature above the martensite finish temperature of the HAZ, allowing slow, uniform cooling that avoids cold cracking. Maintaining the inter-pass temperature within 150–300 °C throughout multi-pass welding must be verified with temperature-indicating crayons or calibrated contact thermometers.

Recommended Filler Metals

• AWS A5.5 E9015-B3 (SMAW / stick electrode) — the most widely used consumable for field welding of 2.25Cr-1Mo joints in all positions
• AWS A5.28 ER90S-B3 (GMAW/GTAW wire) — for root passes and automated welding in shop fabrication environments
• AWS A5.23 EB3 (SAW wire) — for heavy-deposit submerged arc welding of thick-section pressure vessel longitudinal and circumferential seams

Post-Weld Heat Treatment (PWHT) Procedure

• Temperature: 690–730 °C (per EN 13445 / ASME BPVC Section VIII Div. 1)
• Hold time: minimum 1 hour per 25 mm of weld throat thickness, 2 hours minimum total
• Heating and cooling rates: typically ≤ 50–100 °C/hour for sections above 50 mm to avoid thermal shock and cracking
• Documentation: time-temperature records from calibrated thermocouples welded directly to the component surface, reviewed and signed by the responsible welding engineer and included with the vessel documentation package

Industrial Applications of 1.7380 (10CrMo9-10) Forgings

The breadth of 1.7380 deployment in heavy industry reflects both its reliable high-temperature performance and its long track record in regulated pressure equipment applications across multiple sectors.

Power Generation — Boilers and Steam Systems

The largest single application domain for 1.7380 is subcritical and conventional supercritical power plant boilers, where it is used in superheater headers, reheater outlet headers, steam drum nozzle forgings, and main steam pipe flanges operating at 520–580 °C. In 600 MW and 1,000 MW generating units, the forged boiler drum connection nozzles alone may require dozens of individually machined 10CrMo9-10 forgings, each subjected to full ultrasonic testing and hydrostatic proof testing before installation. The combination of high creep strength, well-established PWHT procedures, and decades of design data makes this alloy the default specification in the global power generation sector.

Petrochemical — Hydrocracking and Hydrogen Service

In refinery hydroprocessing units — hydrocracking, hydrotreating, and catalytic reforming — reactor shells, closures, and nozzle forgings must simultaneously resist high-temperature hydrogen attack (HTHA) and maintain creep strength under cyclic thermal and pressure loading. 10CrMo9-10 sits on the safe side of the Nelson curve for hydrogen partial pressures up to approximately 35 bar at 450 °C. Forged 1.7380 reactor closures and man-way flanges are standard in European and Asian refineries for operating pressures up to 200 bar.

Oil & Gas — High-Pressure Valves and Wellhead Equipment

Forged 10CrMo9-10 valve bodies, bonnets, and outlet flanges are specified for high-pressure steam injection wells (HPHT geothermal and EOR applications) and high-pressure gas production systems where operating temperatures exceed the safe range of carbon steel. API 6A PSL-2 and PSL-3 applications require the full suite of Charpy impact testing, hardness surveys, and third-party certification that a competent ISO 9001:2015 certified forging manufacturer can supply.

Heat Exchangers and Pressure Vessels

Tube sheet forgings in shell-and-tube heat exchangers for the chemical processing industry are a high-volume application: a single large heat exchanger may use a 10CrMo9-10 tube sheet up to 2,800 mm in diameter and 300 mm thick. At these section sizes, through-thickness mechanical properties achieved by open-die forging are the only reliable way to ensure uniform performance across the entire tube-to-tubesheet joint interface.

Industrial Furnaces and Rotary Kilns

Forged 10CrMo9-10 rollers, tyre-rings, and retaining rings for industrial furnace conveyors and rotary kiln riding rings represent a growing application driven by the need for improved service life over cast alternatives. The refined grain structure and superior oxidation resistance of forged 1.7380 can extend component replacement intervals by 40–60 % compared with cast Cr-Mo equivalents in identical service conditions.

Grade Comparison: 1.7380 vs Adjacent Cr-Mo Grades

Selecting the right Cr-Mo grade for a pressure equipment application requires understanding where 10CrMo9-10 sits relative to its immediate family members. Over-specifying into P91 or under-specifying into a grade that loses strength at operating temperature affects both project economics and long-term plant reliability.

Frequently Asked Questions about 1.7380 (10CrMo9-10) Steel

The questions below represent the most commonly asked technical and commercial questions about 1.7380, drawn from engineering enquiries received by Jiangsu Liangyi. Each answer is written to be directly usable by engineers, procurement professionals, and quality inspectors.

Sourcing Checklist for Forged 1.7380 Components

The following checklist distils the most critical quality and documentation requirements experienced procurement engineers apply when evaluating 10CrMo9-10 forging suppliers, particularly when sourcing internationally.