X2CrNiN23-4
1.4362
Lean duplex (austenitic-ferritic) corrosion-resistant stainless steel · EN 10088-1:2023 — list, composition and physical-property guidance · 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
X2CrNiN23-4 (1.4362) is the EN lean-duplex grade commonly called 2304. Its approximately 23% chromium, modest nickel, nitrogen addition and low molybdenum produce a duplex microstructure with substantially higher proof strength and better chloride stress-corrosion-cracking resistance than common austenitic stainless steels. Its localized-corrosion resistance is often around the 316L class, but this is environment- and product-dependent; it is not a substitute for the more highly alloyed duplex grade 1.4462 in aggressive chloride service. Product form, thickness, delivery condition and governing product standard must accompany the grade designation when it is specified or purchased.
- Lean duplex: ferrite plus austeniteStructure · Phase balance is controlled by chemistry, solution treatment, cooling and welding thermal cycles.
- Rp0.2 ≥ 450 MPaEN flat-product proof strength · Solution-annealed flat products within the thickness limits listed in EN 10088-2:2024.
- Rp0.2 ≥ 400 MPaEN long-product proof strength · Solution-annealed hot-worked long products up to 160 mm under EN 10088-3; product-form qualifications apply.
- 22.0–24.5% Cr, 3.5–5.5% Ni, 0.05–0.20% NAlloy concept · EN 10088 cast-analysis limits; Mo and Cu are each 0.10–0.60%.
- Calculated PREN range 23.1–29.7Localized-corrosion index · Arithmetic range from EN limits using PREN = Cr + 3.3Mo + 16N; not a guaranteed product requirement.
- MagnetizableMagnetic response · Expected from the substantial ferritic phase; magnetic response is not a phase-balance acceptance test.
Overview
- Designation system
- EN steel name to EN 10027-1; steel number to EN 10027-2
- Product forms
- Hot-rolled plate and strip, Cold-rolled sheet and strip, Bars, rods, wire, sections and bright products, Semi-finished products, Tube, pipe and forgings when ordered to their applicable product standards
- Condition
- Solution annealed (+AT), Hot-worked or cold-processed surface conditions defined by the applicable EN 10088 product part, Cold-worked strength levels for applicable long products when specifically ordered
- Density
- 7.8 g/cm³ (Guidance value at approximately 20 °C from EN 10088-1.)
Designation and specification framework
The steel name identifies a highly alloyed stainless steel with nominally very low carbon (X2), approximately 23% chromium and 4% nickel, with an intentional nitrogen addition. The material number 1.4362 is the more reliable identifier for drawings, purchase orders and certificates because informal terms such as “2304” may be used for products made to different national specifications.
| Standard | Function for 1.4362 | Practical consequence |
|---|---|---|
| EN 10088-1:2023 | Lists the grade, cast-analysis composition and guidance physical properties | It identifies the steel but is not, by itself, a complete purchasing specification. |
| EN 10088-2:2024 | Technical delivery conditions for hot- or cold-rolled sheet, plate and strip for general purposes | Controls mechanical properties by product form and thickness, delivery condition, inspection and surface route. |
| EN 10088-3:2023 | Technical delivery conditions for semi-finished and long products for general purposes | Controls bars, rods, wire, sections and bright products; requirements differ from flat products. |
| EN 10088-4 / EN 10088-5 | Flat and long products for construction purposes | Use where the construction-product specification and its conformity provisions apply. |
| EN 10028-7 | Flat stainless products for pressure purposes | Use instead of general-purpose EN 10088-2 when pressure-equipment material requirements apply. |
| EN 10216-5 / EN 10217-7 | Seamless and welded stainless tubes for pressure purposes | Tube properties, testing and dimensions are governed by the tube standard, not imported from EN 10088-2. |
| EN 10250-4 | Open-die stainless steel forgings for general engineering purposes | Composition and mechanical requirements can differ from the EN 10088 flat- or long-product requirements. |
The current project specification, applicable national adoption and required code edition should always be stated.
Chemical composition and alloy design
| Element | Mass fraction, % | Metallurgical significance |
|---|---|---|
| C | ≤ 0.030 | Low carbon limits carbide-related sensitization and supports weldability. |
| Si | ≤ 1.00 | Deoxidizer; excessive content would promote ferrite. |
| Mn | ≤ 2.00 | Contributes to deoxidation and nitrogen solubility. |
| P | ≤ 0.035 | Residual impurity controlled for toughness and processing quality. |
| S | ≤ 0.015 | Low sulfur supports corrosion resistance and weld quality. |
| Cr | 22.0–24.5 | Principal passivating element and a strong ferrite former. |
| Ni | 3.5–5.5 | Promotes austenite and contributes to phase balance and toughness. |
| Mo | 0.10–0.60 | Modest addition; contributes to localized-corrosion resistance but is far below the level in 1.4462. |
| N | 0.05–0.20 | Strengthens the steel, improves pitting resistance and promotes austenite reformation after welding. |
| Cu | 0.10–0.60 | Can improve behavior in certain reducing acidic environments and affects phase balance. |
| Fe | Balance | Base metal. |
Values are cast-analysis limits. Product-analysis tolerances are separately defined by the applicable product standard. Some other product standards, including pressure and forging specifications, use slightly different limits; the standard on the order therefore matters.
The grade is “lean” primarily because it achieves duplex behavior with much less nickel and molybdenum than conventional 1.4462 duplex steel. Chromium and nitrogen provide useful corrosion resistance and strength, while the relatively low molybdenum content reduces alloy cost but also limits performance in severe chloride pitting and crevice-corrosion conditions.
Delivery condition, microstructure and heat treatment
The normal corrosion-resistant condition is solution annealed, identified as +AT. EN guidance gives a solution-annealing range of 950–1050 °C followed by sufficiently rapid cooling in water or air. Solution treatment may be omitted after hot working only when the resulting product satisfies the required mechanical properties and intergranular-corrosion resistance. The objective is not conventional hardening: it is to dissolve harmful precipitates and establish a suitable ferrite-austenite balance.
| Operation | Guidance | Technical purpose or concern |
|---|---|---|
| Hot forming | Approximately 1150–950 °C | Form within the recommended range and avoid prolonged residence in intermediate-temperature precipitation ranges. |
| Solution annealing | +AT, 950–1050 °C | Restores phase balance and dissolves detrimental precipitates. |
| Cooling after solution treatment | Water or sufficiently rapid air cooling, depending on section size and process | Slow cooling can permit nitrides, carbides or intermetallic phases to form. |
| Post-weld heat treatment | Normally not required for qualified welding procedures | Local solution treatment is generally impractical; weld chemistry and thermal control are used to obtain acceptable phase balance. |
These temperatures are general guidance, not a substitute for a qualified manufacturing procedure. Section size and cooling rate materially affect the result.
A duplex grade should not be accepted solely because bulk chemistry is correct. Excessive ferrite, inadequate austenite reformation or precipitation caused by inappropriate heat treatment or welding can reduce toughness and localized-corrosion performance.
Mechanical properties are product-form dependent
| Product code | Product form | Maximum thickness | Rp0.2 min. | Rm | Elongation min. |
|---|---|---|---|---|---|
| C | Cold-rolled strip, sheet or plate | 8 mm | 450 MPa | 650–850 MPa | 20% |
| H | Continuously hot-rolled strip and sheet/plate cut from strip | 13.5 mm | 450 MPa | 650–850 MPa | 20% |
| P | Individually hot-rolled plate | 75 mm | 450 MPa | 630–800 MPa | 25% |
Room-temperature requirements in the +AT condition. Elongation gauge-length rules and specimen orientation are defined in the standard. These values must not be transferred to tube, forging or long-product orders.
| Applicable size | Rp0.2 min. | Rm | Longitudinal elongation min. | Hardness |
|---|---|---|---|---|
| Thickness or diameter ≤ 160 mm | 400 MPa | 600–830 MPa | 25% | 260 HBW maximum |
The standard includes product-specific qualifications; for rods, only tensile-strength requirements apply. Bright products and intentionally cold-worked strength levels require their own condition-specific requirements.
The high proof strength is one of the grade’s principal engineering advantages. It can permit thinner sections than an austenitic grade where strength governs, but any reduction must be demonstrated by the applicable design code. Stiffness is not doubled: the room-temperature elastic modulus remains about 200 GPa, so deflection, vibration and buckling may still control.
Physical characteristics relevant to design and fabrication
| Property | Value | Condition |
|---|---|---|
| Density | 7.8 g/cm³ | Approximately 20 °C |
| Elastic modulus | 200 GPa | 20 °C |
| Elastic modulus | 194 GPa | 100 °C |
| Elastic modulus | 186 GPa | 200 °C |
| Elastic modulus | 180 GPa | 300 °C |
| Mean thermal expansion coefficient | 13.0 × 10⁻⁶ K⁻¹ | 20–100 °C |
| Mean thermal expansion coefficient | 13.5 × 10⁻⁶ K⁻¹ | 20–200 °C |
| Mean thermal expansion coefficient | 14.0 × 10⁻⁶ K⁻¹ | 20–300 °C |
| Thermal conductivity | 15 W/(m·K) | 20 °C |
| Specific heat capacity | 500 J/(kg·K) | 20 °C |
| Electrical resistivity | 0.80 Ω·mm²/m | 20 °C |
| Magnetizability | Yes | Result of the ferritic phase |
These are guidance data rather than heat-specific certificate values. The lower thermal expansion relative to common austenitic stainless steels can reduce thermal movement and welding distortion.
Corrosion behavior and material selection
The grade combines good general corrosion resistance with much better resistance to chloride stress-corrosion cracking than conventional 304L and 316L-type austenitic steels. Its pitting and crevice-corrosion performance is commonly described as being around the 316L class in many neutral chloride environments, while its high chromium can be advantageous in oxidizing media. Such comparisons are selection guidance, not universal equivalence: temperature, chloride concentration, oxidizing potential, pH, deposits, crevices, surface condition and weld quality can reverse a simple grade ranking.
| Exposure or requirement | Assessment |
|---|---|
| Atmospheric, architectural and moderately corrosive process environments | Often an attractive combination of strength, corrosion resistance and alloy economy. |
| Neutral chloride environments where austenitic SCC is a concern | Duplex structure provides a major advantage over 304L and 316L, subject to temperature and environment. |
| Pitting or crevice corrosion | Generally stronger than 304L and often near 316L, but significantly below 1.4462 duplex in aggressive chloride service. |
| Seawater, warm brines or stagnant crevice conditions | Do not select from the “2304” name or PREN alone; service-specific testing, experience or a more highly alloyed grade may be required. |
| Reducing acids | Performance is chemistry-specific; low molybdenum can be limiting even where chromium content is high. |
| Erosion-corrosion | The combination of high strength and corrosion resistance can be useful, but particle loading, velocity and geometry still require evaluation. |
Published corrosion data for a branded 2304 product are useful screening information but are not automatically guaranteed for every EN 1.4362 product.
Fabrication and welding
The steel is weldable by the common arc-welding processes, but duplex welding is governed by phase balance rather than simply freedom from cracking. Excessively rapid cooling can leave a ferrite-rich heat-affected zone, while excessive heat input or repeated thermal cycling can promote harmful precipitation. Welding procedures should therefore control filler selection, heat input, interpass temperature, shielding and purge quality, joint geometry and cumulative reheating.
| Topic | Practical guidance |
|---|---|
| Filler metal | Over-alloyed duplex fillers such as ISO 14343 23 7 N L or 22 9 3 N L / AWS ER2209 are commonly used to promote adequate weld-metal austenite. Selection should follow the qualified procedure and service-corrosion requirement. |
| Autogenous welding | Can produce excessive ferrite, especially in thicker sections or highly diluted welds. Use only where procedure qualification demonstrates acceptable structure and properties. |
| Preheat | Normally avoided unless needed to remove moisture or meet a specifically qualified procedure. |
| Interpass temperature | Keep controlled and relatively low; producer guidance commonly limits it to about 150 °C. |
| Heat input | No single range applies to every process and joint. Published guidance for 2304 varies; the WPS/PQR should demonstrate acceptable toughness, corrosion performance and phase balance. |
| Shielding and backing gas | Prevent oxidation and nitrogen loss. Nitrogen additions may assist austenite formation when allowed by the qualified process. |
| Post-weld heat treatment | Normally unnecessary and potentially harmful if performed as an uncontrolled stress-relief treatment. |
| Cold forming | Higher strength and springback require greater forming force than austenitic stainless steel. Severe forming can require procedure-specific evaluation or restoration heat treatment. |
| Machining | Higher strength and work hardening demand rigid tooling, positive cutting conditions and adequate cooling. Austenitic machining parameters should not be adopted without adjustment. |
| Surface restoration | Remove heat tint, embedded iron and contamination by appropriate mechanical cleaning, pickling or passivation procedures suited to stainless steel. |
Welding-consumable and heat-input figures are fabrication guidance rather than requirements of the EN grade definition.
Temperature limitations
X2CrNiN23-4 is not normally chosen for prolonged high-temperature exposure. Producer guidance warns of microstructural change and reduced impact toughness after extended exposure above roughly 280–300 °C. EN 10088 mechanical values are material delivery requirements, not design allowable stresses or a universal service-temperature rating. Pressure-equipment use requires the relevant product standard, design code and approved elevated-temperature data.
Duplex steels also have a ductile-to-brittle transition, unlike fully austenitic stainless steels. Low-temperature service therefore requires impact data appropriate to product form, section size, weld condition and design temperature; 1.4362 should not be treated as an automatically suitable cryogenic grade.
Specifying and purchasing the material
| Item | Why it is required |
|---|---|
| Complete product standard and edition | Determines composition, mechanical properties, tests and delivery rules. |
| Steel name or number | State X2CrNiN23-4 or 1.4362; using both reduces ambiguity. |
| Product form and dimensions | Properties and permissible size ranges differ between plate, strip, bar, tube and forgings. |
| Delivery condition and process route | For example +AT and the required hot- or cold-rolled surface condition. |
| Dimensional and surface standard | Controls thickness, width, length, flatness, surface finish and permissible imperfections. |
| Inspection document | EN 10204 type 3.1 is commonly requested where heat-specific traceability and test results are required. |
| Required testing | Identify tensile, impact, intergranular-corrosion, ultrasonic, PMI, ferrite or additional corrosion testing where the application demands it. |
| Welding and service requirements | Provide the intended environment and fabrication route where corrosion performance or phase balance is critical. |
| PED or construction status | State whether pressure-equipment or construction-product requirements apply; general-purpose EN 10088 certification may not be sufficient. |
| Substitution approval | Require technical review of chemistry, product standard, condition, properties, testing, dimensions and code status before accepting S32304, 316L, 2205 or another associated grade. |
A certificate showing only “1.4362” and chemistry does not establish compliance with all mechanical, dimensional, surface, testing or code requirements of the intended component.
Sources
- EN 10088-1:2023 — Stainless steels, Part 1: List of stainless steelsEuropean Committee for Standardization / Slovenian Institute for Standardization
- EN 10088-2:2024 — Technical delivery conditions for sheet/plate and stripEuropean Committee for Standardization / Slovenian Institute for Standardization
- EN 10088-3:2023 — Technical delivery conditions for long productsEuropean Committee for Standardization / Slovenian Institute for Standardization
- Ambient-temperature mechanical properties of duplex flat products to BS EN 10088-2:2024British Stainless Steel Association
- Ambient-temperature mechanical properties of duplex long products to BS EN 10088-3British Stainless Steel Association
- SAF 2304 seamless tube and pipe datasheetAlleima
- Practical Guidelines for the Fabrication of Duplex Stainless SteelsInternational Molybdenum Association
- Stainless Steel Grade Sheets — Grade 2304worldstainless
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