S235 vs S355 Steel: Which Structural Steel to Choose?

📋 S235JR Datasheet → · S355J2 Datasheet → — chemical composition, section-dependent mechanical properties and international equivalent tables.

What Are S235 and S355?

Both are non-alloy/micro-alloyed structural steels under EN 10025-2, and the number in the name states the minimum yield strength (MPa). That is exactly where the decisive difference lies:

• S235 (mat. no. 1.0038, formerly St37-2): min. yield 235 MPa at sections ≤16 mm
• S355 (mat. no. 1.0577, formerly St52-3): min. yield 355 MPa at sections ≤16 mm

In short: S355 offers about 50% higher yield strength than S235 — carrying the same load in a thinner section. S235, on the other hand, is more economical, easier to weld and more widely available.

Chemical Composition Comparison

Element	S235JR (%)	S355J2 (%)
Carbon (C)	≤ 0.17	≤ 0.20
Silicon (Si)	—	≤ 0.55
Manganese (Mn)	≤ 1.40	≤ 1.60
Phosphorus (P)	≤ 0.035	≤ 0.025
Sulfur (S)	≤ 0.035	≤ 0.025
Copper (Cu)	≤ 0.55	≤ 0.55
Carbon equivalent (CEV)	—	≤ 0.45

Use our Chemical Composition tool to compare analyses by grade.

Mechanical Properties (≤16 mm section, EN 10025-2)

Property	S235JR	S355J2
Yield strength (Rₑ)	min. 235 MPa	min. 355 MPa
Tensile strength (Rₘ)	360–510 MPa	470–630 MPa
Elongation (A)	min. 26%	min. 22%
Impact toughness	27 J @ +20 °C (JR)	27 J @ −20 °C (J2)
Density	7.85 g/cm³	7.85 g/cm³

Note: mechanical values decrease as section thickness increases (235 → 195 MPa for S235, 355 → 295 MPa for S355).

The Decisive Difference: Yield Strength → Section and Weight

Higher yield strength feeds straight into the design:

• S355 carries the same load in a thinner, lighter section. In bridges, cranes and heavy steelwork this means weight and cost savings. Its J2 class also guarantees toughness at −20 °C — critical for cold climates and dynamic loading.
• S235 offers lower strength but lower cost, easier welding and wide stock availability. It is the reference material for standard construction and general fabrication.

Both grades weld well thanks to a low carbon equivalent; light preheat is advisable for thick S355 sections. Use the Weight Calculator for mass estimates.

When to Choose Which?

Choose S235 — if:

• You have general construction and moderate loads (building frames, platforms, brackets)
• Cost and availability are your priority
• You produce simple welded structures

Choose S355 — if:

• Weight reduction or high load capacity is the target (bridges, cranes, chassis)
• The structure operates under low temperature / dynamic load (J2 toughness)
• You work in heavy sectors such as offshore, mining and energy

Applications

Sector	S235	S355
Construction	Building frames, platforms, stairs	Bridges, high-rise load-bearing
Machinery	General fabrication, welded chassis	Cranes, lifting equipment booms
Energy	Auxiliary structures	Wind towers, offshore platforms
Mining	Support structures	Machine chassis and booms

The naming conversion is a common question: St37 = S235JR, St52-3 = S355J2 (only the designation changed, the material is the same). The American equivalents are ≈ ASTM A36 and ≈ ASTM A572 Gr.50 respectively. See our Steel Grade Equivalent tool for all cross-standard equivalents.

Supply from Aktif Çelik

At Aktif Çelik we stock both S235JR and S355J2 as hot-rolled bar, carbon steel and cold-drawn (bright) bar in round, square, flat and section forms across a wide size range. With EN 10204 3.1 certificates and +AR/+N delivery conditions, we recommend the grade best suited to your project. Contact our team for technical advice and cut-to-length service.