EN 10025 Steel Grades — S235, S275, S355, S460 for Eurocode 3

Quick Reference: S235 (fy = 235 MPa), S275 (fy = 275 MPa), S355 (fy = 355 MPa), S460 (fy = 460 MPa). Nominal yield strength applies for t <= 16 mm; values reduce for thicker sections. All values are characteristic (nominal) values for design per EN 1993-1-1.

EN 10025 Grade Overview

EN 10025 is the European standard for hot-rolled structural steel products. It defines six parts covering different steel types. The four most common structural grades are:

S235 and S275 are common for secondary members and non-structural applications. S355 is the default choice for structural steel in the UK and Europe — roughly equivalent to A992/Grade 50. S460 is a higher-strength option for heavily loaded members where weight savings justify the cost premium.

Subgrade Notation (JR, J0, J2, K2)

EN 10025 grades include a subgrade letter that specifies Charpy impact toughness at a given temperature:

S355J2 is the standard specification for most UK building structures. S355JR is acceptable for internal members where low-temperature toughness is not required. For bridges, fatigue-loaded structures, and members exposed to temperatures below -10°C, J2 or K2 is typically required.

EN 1993-1-1 Design Values

Per EN 1993-1-1, the design yield strength is:

fyd = fy / gamma_M0

where gamma_M0 = 1.00 (recommended value; UK National Annex may differ). So for S355:

fyd = 355 / 1.00 = 355 MPa (for t <= 16 mm)

The design ultimate strength is:

fud = fu / gamma_M2

where gamma_M2 = 1.25 (recommended value). For net section rupture checks:

fud = 470 / 1.25 = 376 MPa (using minimum fu for S355)

Thickness Reduction

Steel yield strength decreases with increasing thickness due to the rolling and cooling process. EN 1993-1-1 Table 3.1 provides the full fy vs. thickness table:

Always verify the thickness bracket when specifying material. A 50 mm plate in S355 has fy = 335 MPa, not 355 MPa.

Comparison: EN vs Other Standards

These are only approximate comparisons. Direct substitution requires full re-check of all capacity equations against the governing design standard.

Using EN Steel Grades in SteelCalculator.app

When you select EN 1993 as the design code, the calculators automatically populate the correct nominal fy and fu from EN 1993-1-1 Table 3.1. Enter the nominal thickness and the tool applies the correct thickness reduction. Try the free steel grade comparison chart.

EN 10025 Parts — Complete Standard Structure

EN 10025 is split into six parts, each covering different steel product forms:

For standard building construction, Part 2 covers most needs. For bridges and fatigue-loaded structures, Part 3 (normalised) or Part 4 (TMCP) fine-grain steels may be specified for their improved toughness and through-thickness properties.

Chemical Composition Limits

The chemical composition of structural steel controls its weldability, toughness, and strength. Key elements and their typical maxima for S355J2 (EN 10025-2):

The Carbon Equivalent Value (CEV) is the key predictor of weldability:

CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

For S355J2, CEV typically ranges from 0.40 to 0.45. Low CEV (< 0.43) indicates good weldability without preheat for sections up to ~40 mm. Higher CEV requires preheat per EN 1011-2.

For S460N/NL (Part 3, fine-grain), the CEV is tightly controlled at <= 0.53 for improved weldability at higher strength levels.

Charpy Impact Requirements — Detailed

The subgrade letter defines the Charpy V-notch impact energy at the test temperature. This is critical for selecting steel for the minimum service temperature of the structure:

For UK construction, S355J2 is the default. S355J0 is acceptable for internal steelwork. The additional cost of J2 over JR is typically ~5-10%, which is modest compared to the risk of brittle fracture in cold weather.

EN 1993-1-10 provides the formal procedure for selecting steel grade and subgrade based on:

• Minimum service temperature (T_md)
• Element thickness (t)
• Stress level (sigma_Ed relative to fy)
• Consequence class (CC1, CC2, CC3)

Delivery Conditions

The delivery condition affects the mechanical properties and residual stress state:

For S355J2, the default delivery condition is +AR (as-rolled) for sections up to ~40 mm and +N (normalised) for thicker sections. S460 is typically supplied as +M (TMCP) or +N (normalised fine-grain per EN 10025-3).

Through-Thickness Properties (Z-Quality)

When a connection details subjects the steel to through-thickness tension (e.g., welded moment connections, column base plates with full-strength welds), lamellar tearing can occur. EN 10164 defines three Z-quality classes based on reduction-of-area in through-thickness tensile tests:

Specify S355J2+Z25 for thick end plates in moment connections and for column base plates with high through-thickness demand.

Weathering Steels (EN 10025-5)

Weathering steels (S355J2W, S355K2W) form a protective rust-like patina that eliminates the need for paint in atmospheric exposure. Key properties:

Weathering steel requires alternating wet/dry cycles — it is not suitable for permanently wet, buried, or marine-immersed conditions. In the UK, S355J2W is specified for exposed bridge girders and architectural steelwork.

EN 1993-1-10 — Fracture Toughness Material Selection

EN 1993-1-10 provides the formal procedure for selecting steel to avoid brittle fracture:

1. Determine T_md (minimum design metal temperature) from the building location
2. Calculate the stress level sigma_Ed = max tensile stress / fy(t)
3. Select reference temperature T_Ed based on element thickness and detail category
4. Choose steel subgrade ensuring T_Ed >= T_md

As a practical rule for UK buildings (temperate climate, T_md ~ -5°C):

• Up to 20 mm thick: S355JR (consequence Class CC1) or S355J0 (CC2)
• 20-40 mm thick: S355J0 (CC2)
• 40-75 mm thick: S355J2 (CC2) or S355K2 (CC3)
• 75 mm+: S355K2 or S355NL (CC3) — fine-grain, normalised

Always follow EN 1993-1-10 when the minimum service temperature is below -5°C or when the element is thicker than 40 mm.

EN 10025 vs ASTM vs AS/NZS — Detailed Cross-Reference

The chemical and mechanical properties of European, US, and Australian grades are similar but not identical. Key differences:

Key practical difference: S355J2 has a higher fu/fy ratio (1.32) than A992 (1.20), which gives European steel better strain-hardening capacity and slightly better performance in tension-controlled connections (e.g., net section fracture). The Australian 350 Grade has similar fy to S355 but with a fu minimum of 480 MPa vs S355's 470 MPa — a small but real difference in tension applications.

Cannot directly substitute without re-check. The nominal fy values differ, the fu values differ, and the thickness reduction tables differ between codes. If you're designing an EN 1993 connection with S355 then need to use A992 steel, re-calculate all resistance checks with the actual fy and fu per ASTM A6.

S460 and S690 — High-Strength Steel in EN 1993

S460 is covered by EN 10025 Parts 3 (normalised), 4 (TMCP), and 6 (QT). The choice of delivery condition affects design:

S460 is cost-effective when:

• Weight savings reduce foundation costs
• Member depth is constrained (e.g., headroom in multi-storey)
• Transport and erection costs are high (remote sites)

S690 is typically reserved for:

• Long-span trusses where member weight controls
• Very heavy columns in high-rise construction
• Offshore structures where weight is a first-order cost driver

The buckling behaviour of S460 and S690 differs from S355 — the higher yield strength means sections are more slender (higher lambda_bar) for the same geometry, so buckling reduction factors (chi) are lower. The benefit of the higher fy may be partially offset by increased stability sensitivity.

EN 1993 Partial Factors for Steel Grade Selection

Unlike AISC (phi = 0.90 for flexure, 0.90 for compression, 0.75 for bolts) and AS 4100 (phi = 0.90 for most checks), EN 1993 does not differentiate partial factors by failure mode within the same limit state — gamma_M0 = gamma_M1 = 1.00 for all stability and cross-section checks. The conservatism is embedded in the buckling curves, not the partial factors.

Related Pages

• EN 1993-1-1 Beam Design Guide — Section classification, Mc,Rd, LTB with full worked example
• EN 1993 Column Buckling Guide — Curves a0-d, Perry-Robertson, Nb,Rd
• EN 1993-1-8 Connection Design Guide — Full fin plate worked example
• UK Steel Beam Sizes — UB, UC, PFC — Complete UK section tables
• Steel Grades — A36, A572, A992, 350 Grade Comparison — Cross-standard grade reference

This page is for educational reference. All steel grade values are nominal (characteristic) values per EN 10025 and EN 1993-1-1. Verify against the current edition of the standard and the applicable National Annex for your project. Material certification to EN 10204 Type 3.1 is standard for structural steel — request 3.2 for critical applications. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.