EN 1993 Steel Grades — EN 10025 S235 to S460 Complete Reference

Complete European structural steel grades reference covering EN 10025-2 (hot-rolled non-alloy structural steels) and EN 10025-4 (thermomechanical-rolled), plus EN 10025-3 (normalised/normalised-rolled) and EN 10025-6 (quenched and tempered). S235, S275, S355, S420, and S460 nominal yield strength with subgrade toughness designations JR, J0, J2, K2, Charpy V-notch energy requirements at 27 J and 40 J thresholds, through-thickness Z-quality Z15/Z25/Z35 for welded connections, and National Annex steel grade selection guidance for EN 1993-1-1 design.

Quick access: EN 1993 Steel Design → | EN 1993 Column Buckling → | European Beam Sizes → | Section Properties →

EN 10025 Steel Grade Naming System

EN 10025 designates structural steel grades using a systematic naming convention that communicates yield strength, impact toughness, and delivery condition:

S 355 J2 +N
│  │   │  │
│  │   │  └── Delivery condition: +N (normalised), +M (TMCP), +AR (as-rolled)
│  │   └────── Toughness subgrade: J2 = 27 J at -20°C
│  └────────── Nominal yield strength (MPa) for t ≤ 16 mm
└────────────── S = Structural steel

The grade designation S identifies the material as a structural steel under EN 10025. The three-digit number is the minimum yield strength in MPa for the smallest thickness range (t ≤ 16 mm). The suffix indicates the impact toughness quality (JR, J0, J2, or K2), and the delivery condition is noted with a symbol after a plus sign.

EN 10025 Parts Overview

Complete Grade Properties Table — EN 10025-2

The following table presents yield strength, tensile strength, and elongation requirements for the most commonly specified EN 10025-2 grades across four thickness brackets used in EN 1993-1-1 design:

Important note for EN 1993-1-1 designers: BS EN 1993-1-1 UK National Annex (NA.2.4) recommends using S275 for general buildings and S355 for heavier structural frames. S235 is now rare in mainstream UK construction (legacy buildings only). S450 is less common but gaining traction for optimised trusses and long-span beams. Pre-1986 UK-origin table assumes Grade 43 = S275 and Grade 50 = S355 — always verify existing steel with tensile coupon testing before assessment.

EN 10025-3 and EN 10025-4 Fine-Grain Steels

For applications requiring improved toughness, through-thickness properties, or lower carbon equivalent values, the fine-grain steels under Parts 3 and 4 are preferred:

The L suffix (NL, ML) indicates low-temperature impact properties at -50°C, tested with 27 J minimum Charpy V-notch energy. Non-L grades are tested at -20°C (N) or -20°C (M).

Charpy Impact Toughness Requirements

The subgrade letters designate the Charpy V-notch impact energy (CVN) guarantee — the temperature at which the steel achieves the specified minimum impact energy. This is critical for fracture-critical design per EN 1993-1-10 (material toughness) and EN 1993-1-1 Cl. 3.2.3.

EN 10025-2 Charpy Requirements

The J in the designation stands for "Joule," the unit of absorbed impact energy. The number indicates the test temperature: J0 = 0°C, J2 = -20°C. K2 is a special toughness grade requiring 40 J at -20°C, used for structures in cold climates and for elements where fracture is a principal design concern.

Subgrade Selection Guide per EN 1993-1-10

EN 1993-1-10 provides a fracture-safe material selection approach based on:

• Minimum service temperature (Tmd)
• Steel grade and thickness
• Stress level in the element (σEd as a fraction of fy)

For the UK, Annex NA to EN 1993-1-10 recommends:

*For t > 50 mm in K2 applications, verify with Table 2.1 of EN 1993-1-10 and consider S355NL (Part 3) as an alternative.

Through-Thickness Properties — Z-Quality

EN 10164 specifies through-thickness (Z-direction) tensile properties for steel plates and sections subject to through-thickness loading in welded connections. This is particularly relevant for EN 1993-1-8 welded joint design where the connected plate experiences tensile stress through its thickness (e.g., column-beam moment connections with continuity plates, end plates with full-strength welds).

The designation is appended to the grade: e.g., S355J2+Z25 means S355 with J2 toughness and Z25 through-thickness quality. Specifying Z-quality adds cost and lead time; reserve it for connections where EN 1993-1-8 Cl. 4.2 requires lamellar tearing prevention.

Lamellar Tearing Risk Assessment (EN 1993-1-8 Cl. 4.2)

A joint is considered high-risk for lamellar tearing when:

1. The weld throat dimension exceeds 15 mm
2. Multiple welds intersect in the through-thickness direction
3. The plate is subject to high restraint against contraction after welding
4. The joint geometry creates a triaxial stress state

For high-risk joints, specify Z25 minimum. For moderately restrained joints, Z15 is typically sufficient.

EN 1993-1-1 Material Partial Factors

EN 1993-1-1 Table 2.1 (modified by National Annexes) provides the material partial factors applied to structural steel design:

The UK NA reduction of γM2 for cross-section tension fracture from 1.25 to 1.10 is a significant relaxation. Always check the relevant National Annex for the site jurisdiction.

Grade Comparison — EN 10025 vs International Standards

Design caution: These are approximate mechanical property equivalents. Chemical composition, weldability, and delivery condition all differ between standards. Always confirm grade substitution with the project's responsible structural engineer and check the compatibility of the substituted material with the original design assumptions, particularly for fatigue, fracture, and seismic applications.

Grade Selection Workflow for EN 1993 Designers

Step 1: Determine Required Yield Strength

Calculate the minimum fy required to satisfy strength limit states (cross-section resistance, member buckling). Start with S275 as default for general buildings. Move to S355 if section weight becomes excessive or deflection governs. S460 is used when section depth is constrained (e.g., retrofit, architectural constraints).

Step 2: Select Subgrade (Toughness)

1. Determine minimum service temperature from EN 1991-1-5 (Thermal actions) or project-specific data
2. For the UK: BS EN 1993-1-10 UK NA provides a direct table lookup using minimum steel temperature, thickness, and stress level
3. Match the required Charpy energy (27 J or 40 J) at the test temperature to the appropriate subgrade (JR / J0 / J2 / K2)

Step 3: Check Weldability

Verify carbon equivalent value (CEV) against EN 1011-2 welding guidelines:

• CEV ≤ 0.40: No special measures required (S275JR, S355JR typical)
• CEV 0.40-0.45: Standard welding procedures (S355J2, S355M typical)
• CEV > 0.45: Preheat and controlled heat input required (S460M, S460N, S690QL)

Step 4: Assess Through-Thickness Requirements

Review welded connections per EN 1993-1-8 Cl. 4.2. For connections with high through-thickness restraint, specify Z15, Z25, or Z35 per EN 10164.

Step 5: Check National Annex

Every EU member state publishes a National Annex that may:

• Restrict certain grades or delivery conditions
• Modify γM factors
• Impose additional testing requirements
• Specify mandatory CEV limits

Always verify the building jurisdiction's National Annex before finalising the steel specification.

Frequently Asked Questions

What is the difference between S355J0 and S355J2 steel?

S355J0 and S355J2 have identical tensile properties (fy = 355 MPa for t ≤ 16 mm, fu = 470-630 MPa). The difference is Charpy impact toughness temperature: J0 guarantees 27 J at 0°C, while J2 guarantees 27 J at -20°C. For an outdoor unprotected steel frame in the UK, J2 is the standard recommendation. For interior heated buildings with secondary members only, J0 may be acceptable. The cost premium for J2 over J0 is typically 3-5%.

What is the most commonly specified steel grade for EN 1993 building design?

S355J2 is the single most common grade for primary structural steel in European multi-storey buildings. It offers the best balance of strength, weldability, and toughness. S275JR is still common for secondary members, purlins, and light industrial sheds. The UK market has largely standardised on S355J2 for UC/UB sections, with S355J2+Z25 for thick end plates and moment connections. S235 is rarely specified for new construction except for architectural non-structural elements.

Can I substitute S355J2 for S355J0 in an existing design?

Yes, S355J2 is a direct upgrade from S355J0: it meets all the mechanical property requirements of J0 plus provides improved low-temperature toughness (27 J at -20°C vs 27 J at 0°C). The CEV of J2 is typically slightly higher, so verify weldability with the fabricator. Substituting upward in toughness (JR → J0 → J2 → K2) is always permitted under EN 1993-1-1 provided the yield and tensile strength match.

When should I specify Z-quality steel for welded connections?

Specify Z-quality when welded details create through-thickness tensile stresses in the connected plate. The key indicators are: weld throat exceeding 15 mm, cruciform or T-joint configurations, highly restrained connections that prevent weld shrinkage, and cumulative weld metal volume exceeding 500 cm³ per metre of joint. Z25 is the minimum for fully restrained moment-resisting connections in multi-storey frames. Z35 is reserved for offshore, seismic, and very thick (t > 50 mm) plate assemblies.

What is the difference between EN 10025-2 S355, EN 10025-3 S355N, and EN 10025-4 S355M?

All three achieve fy = 355 MPa minimum, but the delivery conditions and application suitability differ. EN 10025-2 S355 is the base specification (as-rolled or normalised at the manufacturer's discretion). EN 10025-3 S355N is normalised, providing finer grain structure and better toughness for thicker sections — this is the go-to grade for bridges and heavy welded fabrications. EN 10025-4 S355M is thermomechanically rolled (TMCP), achieving the required strength through controlled rolling and cooling rather than alloying, which produces a lower CEV and therefore better weldability. S355M is increasingly favoured for heavy plates (>40 mm) due to reduced preheat requirements.

Related Pages

• EN 1993 Steel Design Overview →
• EN 1993 Column Buckling — Flexural Buckling per Cl. 6.3 →
• European Steel Beam Sizes — HEA/HEB/IPE →
• EN 1990 Load Combinations →
• European Wind Load per EN 1991-1-4 →
• Steel Grades Comparison — International Standards →
• EN 1993-1-8 Bolted Connections →
• EN 1993-1-8 Welded Connections →

Educational reference only. Verify all steel grade specifications against current EN 10025 standards and the relevant National Annex for the building jurisdiction. Material substitutions must be approved by the project's responsible structural engineer. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent verification by a qualified structural engineer.