X2CrNiMoN25-7-4
1.4410
Nitrogen-alloyed super duplex (austenitic-ferritic) corrosion-resistant stainless steel · EN 10088-1:2023 — list and chemical definition of stainless steels · EN 10088-2:2024 — sheet, plate and strip for general purposes · EN 10088-3:2023 — semi-finished products, bars, rods, wire, sections and bright products for general purposes · EN 10028-7 — stainless flat products for pressure purposes · EN 10216-5 — seamless stainless steel tubes for pressure purposes · EN 10217-7 — welded stainless steel tubes for pressure purposes · EN 10222-5 — stainless steel forgings for pressure purposes
1.4410 is a high-alloy, nitrogen-strengthened super duplex stainless steel combining very high proof strength with strong resistance to chloride pitting, crevice corrosion and stress-corrosion cracking. Its performance depends on maintaining an appropriate ferrite–austenite balance and avoiding intermetallic precipitation during production, heat treatment and welding. The designation alone is insufficient for procurement: the applicable product standard, form, dimensions, delivery condition, testing and any project-specific PREN, ferrite, impact or corrosion-test requirements must also be stated.
- Approximately 25% Cr, 7% Ni, 4% Mo and 0.3% NAlloy concept · The chromium, molybdenum and nitrogen combination gives substantially greater localized-corrosion resistance than standard duplex 1.4462.
- Typically 530 MPa for solution-annealed plate, hot-rolled products and barMinimum proof strength · The exact requirement depends on product form, thickness, orientation and governing product standard; cold-rolled flat product may have a higher minimum.
- Cr 24.0–26.0%; Ni 6.0–8.0%; Mo 3.00–4.50%; N 0.24–0.35%EN cast-analysis ranges · These broad grade limits do not by themselves guarantee a project-specific minimum PREN.
- Duplex ferrite–austenite structureMicrostructure · Phase balance and freedom from sigma, chi and other harmful precipitates are central to toughness and corrosion performance.
- Chloride-bearing servicePrincipal strength · Especially useful where 316L or standard duplex grades do not provide sufficient resistance to localized corrosion or chloride stress-corrosion cracking.
- Control of thermal historyCritical fabrication issue · Excessive time in critical temperature ranges can precipitate intermetallic phases and sharply reduce toughness and corrosion resistance.
Overview
- Designation system
- EN steel name and EN material number
- Product forms
- Hot-rolled plate and sheet, Cold-rolled sheet and strip, Bar, rod, sections and bright products, Seamless and welded tube, Forgings and forged fittings, Semi-finished products
- Condition
- Solution annealed (+AT) and rapidly cooled, Cold-worked conditions where specifically ordered under the applicable product standard
- Density
- 7.8 g/cm³ (Representative room-temperature value; not a chemical or mechanical acceptance requirement of EN 10088.)
How the designation and standards work
X2CrNiMoN25-7-4 is the EN symbolic steel name. “X” identifies a high-alloy steel; “2” denotes a nominal carbon level near 0.02%; and the remaining symbols indicate a chromium–nickel–molybdenum–nitrogen alloy with nominal contents near 25%, 7% and 4% for Cr, Ni and Mo. The unique European material number is 1.4410.
| Product or application | Principal specification | Why it matters |
|---|---|---|
| Grade identity and composition | EN 10088-1 | Lists the stainless steel and establishes its general chemical definition; it is not, by itself, a complete purchasing specification. |
| General-purpose flat product | EN 10088-2 | Controls sheet, plate and strip delivery condition, mechanical properties, finishes, inspection and testing. |
| General-purpose long product | EN 10088-3 | Covers semi-finished products, bar, rod, wire, sections and bright products. |
| Pressure-purpose plate | EN 10028-7 with EN 10028-1 | Use instead of EN 10088-2 when pressure-equipment material requirements apply. |
| Seamless pressure tube | EN 10216-5 | Defines tube-specific dimensions, properties, tests and delivery requirements. |
| Welded pressure tube | EN 10217-7 | Defines requirements particular to welded stainless pressure tube. |
| Pressure forgings | EN 10222-5 | Applies to forgings rather than rolled bar or plate. |
Requirements from these specifications must not be combined into a single universal property set.
Always specify the dated product standard appropriate to the item being purchased. EN 10088 is a multi-part family; stating only “EN 10088” leaves product form, mechanical requirements and inspection provisions unresolved.
Chemical definition and corrosion-alloying strategy
| Element | Requirement, mass % | Metallurgical significance |
|---|---|---|
| C | ≤ 0.030 | Low carbon limits carbide-related chromium depletion and supports weldability. |
| Si | ≤ 1.00 | Deoxidizer; excessive content can encourage intermetallic formation. |
| Mn | ≤ 2.00 | Affects nitrogen solubility and phase balance. |
| P | ≤ 0.035 | Residual impurity controlled for toughness and fabrication quality. |
| S | ≤ 0.015 | Kept low for corrosion resistance, hot workability and weld quality. |
| Cr | 24.0–26.0 | Passivity and oxidation resistance; major contributor to pitting resistance and ferrite stability. |
| Ni | 6.0–8.0 | Promotes austenite and helps establish the duplex phase balance. |
| Mo | 3.00–4.50 | Strongly improves resistance to pitting and crevice corrosion but accelerates harmful intermetallic precipitation if thermal processing is poorly controlled. |
| N | 0.24–0.35 | Strengthens the alloy, improves pitting resistance and promotes austenite formation. |
Values are cast-analysis limits. Product-analysis tolerances are addressed separately by the applicable standard.
Mechanical properties are product-form dependent
The high strength is produced by nitrogen solid-solution strengthening and the duplex microstructure, not by quench-and-temper hardening. The values below illustrate solution-annealed general-purpose products. They must not be transferred automatically to tube, forging, pressure-purpose, cold-worked or unusually thick products.
| Product code and size range | Condition | Rp0.2 min, MPa | Rm, MPa | Elongation min | Important qualification |
|---|---|---|---|---|---|
| C — cold-rolled strip/sheet, t ≤ 8 mm | +AT | 550 | 750–1000 | 20% | Values and specimen orientation are governed by the standard; narrow strip provisions can modify proof-strength requirements. |
| H — hot-rolled strip/sheet, t ≤ 13.5 mm | +AT | 530 | 730–930 | 25% | Applicable to the stated product category and size range. |
| P — hot-rolled plate, t ≤ 75 mm | +AT | 530 | 730–930 | 25% | Properties for larger thicknesses require agreement at enquiry and order. |
These are specification minima or ranges, not representative design values.
| Applicable dimension | Rp0.2 min | Rm | Elongation min | KV2 min | Hardness |
|---|---|---|---|---|---|
| ≤ 160 mm | 530 MPa | 730–930 MPa | 25% | 100 J | 290 HBW maximum, informative in common tabulations |
Test direction, product condition and exact applicability must be checked against the ordered edition of EN 10088-3. Impact requirements from one product form should not be imposed on another without specification.
Duplex wrought products are anisotropic. Strength, elongation and impact toughness can vary with specimen orientation because rolling or forging elongates the two-phase microstructure. Orientation must therefore be retained when assessing test reports or establishing design allowables.
Microstructure and thermal processing
Correctly solution-annealed 1.4410 contains ferrite and austenite with no materially harmful level of intermetallic phases. Exact phase balance is not established by the grade name alone. Producers commonly target a near-balanced structure, while acceptable ferrite limits for base metal, heat-affected zones and weld metal are normally imposed by the relevant product, welding or project specification.
| Thermal exposure | Principal concern | Practical consequence |
|---|---|---|
| Solution annealing, commonly around 1050–1125°C followed by rapid cooling | Dissolution of intermetallic phases and restoration of phase balance | The precise cycle must suit product thickness and producer procedure; slow cooling is unacceptable. |
| Slow cooling or prolonged exposure below the solution-annealing range | Sigma/chi phases and secondary-phase precipitation | Can severely reduce impact toughness and localized-corrosion resistance even when room-temperature tensile strength appears satisfactory. |
| Intermediate-temperature stress relief | Potential precipitation and embrittlement | Conventional carbon-steel stress-relief treatments must not be applied without a specifically qualified metallurgy and procedure. |
| Hot forming | Narrower processing window than lower-alloy duplex grades | Hot-worked finished components normally require solution annealing and rapid cooling. |
| Cold work | Increased strength, springback and residual stress | Heavy cold deformation may require evaluation of corrosion, dimensional stability and subsequent heat-treatment needs. |
The quoted solution-annealing range is representative producer and industry guidance, not a universal replacement for the applicable product specification or approved manufacturing procedure.
Corrosion behaviour and material selection
The grade is selected primarily for resistance to chloride-induced pitting, crevice corrosion and stress-corrosion cracking, together with strength substantially above that of common austenitic stainless steels. Typical uses include seawater systems, desalination equipment, offshore and subsea components, chemical-process equipment, flue-gas cleaning systems, high-chloride brines, heat exchangers, pressure equipment and pulp-and-paper service.
| Mechanism or environment | Assessment |
|---|---|
| Pitting and crevice corrosion | Much stronger resistance than 316L and normally stronger than standard duplex 1.4462. Crevice geometry, temperature, deposits, chlorination and surface condition remain decisive. |
| Chloride stress-corrosion cracking | The duplex structure gives markedly better resistance than conventional austenitic grades, but immunity must not be assumed at every temperature, stress and chloride activity. |
| General corrosion | Good in many organic and inorganic media, but alloy selection must use actual concentration, temperature, aeration, contaminants and flow conditions. |
| Reducing acids | High chloride resistance does not automatically mean optimum performance in strongly reducing acids. Copper-bearing or nickel-base alloys can be more appropriate in some acid services. |
| Erosion-corrosion and corrosion fatigue | High strength and corrosion resistance can be advantageous in high-velocity service, provided cavitation, solids and local geometry are evaluated. |
| Welded structures | Corrosion performance depends on weld procedure, filler selection, root shielding, heat tint removal and restoration of a clean passive surface. |
There is no defensible universal maximum chloride concentration or seawater temperature for the grade. Such limits depend on the complete service environment and fabrication condition.
Fabrication and welding
1.4410 is weldable, but its processing window is narrower than that of standard duplex steels because its high chromium and molybdenum contents accelerate intermetallic precipitation. Procedures must balance two competing needs: sufficient cooling time for austenite reformation and sufficiently rapid passage through the temperature range in which harmful phases precipitate.
| Operation | Control point |
|---|---|
| Welding procedure | Qualify specifically for super duplex material, product thickness, restraint, process, consumable and service requirements. |
| Filler metal | Matching super-duplex consumables such as ISO 14343 S 25 9 4 N L or AWS ER2594 are commonly used; their elevated nickel promotes adequate weld-metal austenite. |
| Heat input | A representative producer window is approximately 0.2–1.5 kJ/mm, while broader industry guidance commonly cites about 0.3–1.5 kJ/mm. The qualified WPS, not a generic range, governs production. |
| Interpass temperature | Keep low; producer guidance may permit up to 150°C, while some general super-duplex guidance recommends 100°C. Use the limit established by the qualified procedure and applicable project specification. |
| Preheat and local PWHT | Preheat is normally avoided. Local stress relief is generally unsuitable because it can precipitate intermetallic phases. |
| Autogenous welding | May produce excessive weld-metal ferrite, especially in thicker sections. Acceptance requires procedure qualification demonstrating phase balance, toughness and corrosion performance. |
| Backing and shielding | Protect the root from oxidation and nitrogen loss. Gas composition and oxygen control should be established during qualification. |
| Post-weld cleaning | Remove heat tint, embedded iron and contamination by suitable mechanical and chemical cleaning; final surface condition materially affects localized-corrosion resistance. |
| Forming | Expect higher loads and springback than with 300-series austenitic stainless steel. Avoid carbon-steel contamination and damaged surfaces. |
| Machining | Use rigid equipment, sharp tooling, positive cutting action and effective coolant. High strength and work hardening produce higher cutting forces than conventional austenitic grades. |
Manufacturer welding ranges are useful starting guidance but are not grade-wide acceptance requirements.
Specification, purchasing and inspection
| Item | Why it matters |
|---|---|
| Product standard and edition | Determines whether the order is for general-purpose plate, pressure plate, tube, bar or forging and establishes the applicable tests. |
| Designation | State both X2CrNiMoN25-7-4 and 1.4410; add a UNS or ASTM designation only when the corresponding specification is also required. |
| Product form, dimensions and tolerances | Mechanical requirements and available conditions vary with thickness, diameter and manufacturing route. |
| Delivery condition | Normally +AT for corrosion-resistant wrought products; cold-worked conditions require separate property and dimensional requirements. |
| Inspection document | Specify the required EN 10204 document, commonly 3.1 or, where justified, 3.2. |
| Actual chemistry and PREN | Request reported Cr, Mo and N values and state a minimum PREN if the project requires one. |
| Impact testing | Define test temperature, specimen orientation, size and acceptance criteria rather than citing an unqualified energy value. |
| Phase balance | Where critical, state the permitted ferrite range, measurement method, examination locations and whether requirements apply to base metal, HAZ and weld metal. |
| Corrosion testing | If ASTM G48, ISO 17781 or another test is required, state method, temperature, duration, specimen preparation and acceptance criteria. |
| Surface condition | Specify finish, pickling/passivation, heat-tint acceptance and protection from iron contamination. |
| Supplementary examination | State PMI, ultrasonic testing, penetrant testing, weld NDE and any project-specific manufacturing qualification. |
| Service-code compliance | Pressure equipment, sour service, offshore and structural work may impose requirements additional to the base material grade. |
A certificate showing only “1.4410” and compliant tensile properties does not establish suitability for severe chloride service. Chemistry balance, thermal processing, microstructure, surface condition, welding and service-specific testing can all be controlling.
Substitution and cross-standard cautions
UNS S32750 is the closest widely used American designation and is routinely associated with 1.4410, but the two identifiers belong to different specification systems. A valid substitution must compare the actual product specifications, chemistry limits, mechanical requirements, heat treatment, dimensions, testing, certification and service-code requirements. “2507” is a common family description, while SAF 2507 is a proprietary trade designation; neither should replace the formal specification on a purchase order.
Sources
- EN 10088-1:2023 — Stainless steels — Part 1: List of stainless steelsEuropean Committee for Standardization / EVS
- EN 10088-2:2024 — Technical delivery conditions for sheet/plate and stripEuropean Committee for Standardization
- EN 10088-3:2023 — Technical delivery conditions for long productsEuropean Committee for Standardization / BSI
- EN 10216-5:2021 — Seamless stainless steel tubes for pressure purposesEuropean Committee for Standardization
- Duplex Stainless Steelsworldstainless
- Practical Guidelines for the Fabrication of Duplex Stainless SteelsInternational Molybdenum Association
- SAF 2507 — Bar and billet material dataAlleima
- SAF 2507 — Strip steelAlleima
- Calculation of pitting resistance equivalent numbersBritish Stainless Steel Association
- Chemical composition of stainless steel flat products to EN 10088-2British Stainless Steel Association
Ask MetalMate about X2CrNiMoN25-7-4
Discussing: X2CrNiMoN25-7-4 / 1.4410
AI assistant · Responses are generated and can contain errors; verify specifications before acting.