S235, S275, and S355 Structural Steel Comparison and Properties

Introduction

Structural steel grades S235, S275, and S355 are defined under the EN 10025 standard and represent the most widely used materials in buildings, bridges, offshore structures, and heavy machinery.

This guide provides a practical comparison of S235 vs S275 vs S355, including yield strength, tensile strength, chemical composition, mechanical properties, and equivalents in ASTM, JIS, and GB standards. It focuses on technical performance rather than procurement or cost.

S235, S275, and S355 Structural Steels Grades Overview

Grade	Minimum Yield Strength (MPa)	Typical Suffix	Impact Test
S235	235	JR	Room temperature
S275	275	JR	Room temperature
S355	355	JR / J2 / NL	Room / Low temperature

The designation system in EN 10025 is straightforward:

• The letter “S” stands for structural steel.
• The number represents the minimum yield strength in N/mm².
• Suffixes like JR, J2, NL indicate impact toughness requirements.

👉 For more details on suffixes like JR, J2, and NL, see our guide: S355JR / S355J2 / S355NL – What’s the Difference?

Mechanical Properties of S235, S275 and S355 Steel

Mechanical performance varies among S235/S275/S355 primarily in yield strength (ReH) and tensile strength (Rm). Yield strength is the primary classification basis under EN 10025, while tensile strength provides an additional reference for overall mechanical performance.

1. Yield Strength of S235, S275 and S355 (EN 10025)

According to EN 10025-2, the minimum yield strength (fy) of structural steel grades S235, S275, and S355 is defined as 235 MPa, 275 MPa, and 355 MPa respectively for plate thickness up to 16 mm. These values represent standard-specified minimums rather than guaranteed test results for every heat. As thickness increases, the minimum required yield strength decreases in stepwise ranges as specified in the standard.

This stepwise increase in fy explains the fundamental structural difference between S235, S275, and S355, with S355 preferred for heavy load-bearing or dynamically loaded structures, while S235 and S275 are more commonly used for light and medium structural applications.

2. Mechanical Properties Comparison of S235, S275 and S355 Steel

The table below compares the key mechanical properties of S235, S275, and S355 structural steel, including yield strength (ReH), tensile strength (Rm), elongation, impact resistance, weldability, and formability.

Property	S235	S275	S355
Yield Strength (MPa)	235	275	355
Tensile Strength (MPa)	360–510	370–530	470–630
Elongation (%)	≥26	≥23	≥22
Impact Resistance	Basic	Improved	Excellent, suitable for low temperatures
Weldability	Excellent	Excellent	Good
Formability	High	Moderate	Lower

Chemical Composition of S235, S275 and S355 (C & Mn Comparison)

The difference in yield strength comes primarily from the carbon and manganese content.

Grade	Carbon (C %)	Manganese (Mn %)	Explanation
S235	≤0.17	≤1.40	Low carbon, excellent weldability, lower strength
S275	≤0.21	≤1.50	Slightly higher carbon & manganese, balanced properties
S355	≤0.24	≤1.60	Higher C & Mn levels, resulting in higher yield strength

Engineers should note that while increasing C and Mn enhances yield strength, it can slightly reduce weldability.

S235, S275 and S355 Material Equivalents

Below is a simplified equivalence chart for S235, S275, and S355 steel:

EN Standard	ASTM Equivalent	JIS Equivalent	GB Equivalent
S235JR	ASTM A36	SS400	Q235B
S275JR	ASTM A36 / ASTM A529	SM400A / B	Q275
S355JR	ASTM A572	SM490A / B	Q345B

S235 vs S275 vs S355: Key Technical Differences

1.Strength: S355 > S275 > S235 in both yield and tensile strength

2.Structural Load Capacity:

• S235 → light structures
• S275 → medium-load components
• S355 → heavy-duty structures (bridges, cranes, machinery)

3.Weldability: All grades offer good weldability

4.Toughness / Sub-Grades: JR → J0 → J2, increasing energy absorption (Charpy impact)

Applications of S235 / S275 / S355 Structural Steel

Choosing between S235, S275, and S355 depends on both structural requirements and project environment.

S235 – For Light Structures and General Fabrication

• Frames, fences, containers, small workshops
• High weldability and formability

👉 Related product:

• S235JR Carbon Steel Coil
• S235JR Carbon Steel Plate
• S235 Welded Steel Pipe

S275 – For Medium-Strength Structures

• Commercial buildings, bridges, industrial machinery bases
• Balanced strength, ductility, and price

S355 – For Heavy-Duty or Dynamic Loads

• Bridges, offshore platforms, wind towers, high-rise structures
• Superior yield strength and impact toughness, especially at low temperatures

👉 Related product:

• S355JR Carbon Steel Plate
• S355JR Carbon Steel Coil
• S355J2 / S355JR Wind Tower Steel Plate

How to Choose Between S235, S275, and S355 Steel Grades

Project Type	Recommended Grade	Reason
Light framing, warehouse structure	S235	Easy fabrication, lowest cost
Commercial or bridge structure	S275	Higher load capacity, moderate cost
Offshore or high-rise building	S355	High strength, excellent toughness

When comparing S275 vs S355, consider environmental factors like wind, vibration, and temperature; S355 performs better in offshore or cold regions.

Frequently Asked Questions

• Q: What is the yield strength of S235 steel according to EN 10025?
  A: According to EN 10025-2, the minimum yield strength of S235 structural steel is 235 MPa for plate thickness up to 16 mm. For thicker plates, the specified minimum yield strength decreases stepwise depending on thickness ranges defined in the standard.
• Q: What is the yield strength of S275 steel in MPa?
  A: The minimum yield strength of S275 steel is 275 MPa for thickness up to 16 mm, as specified in EN 10025-2. For greater thicknesses, the minimum yield strength is reduced according to the standard’s thickness-dependent limits.
• Q: What is the tensile strength of S275 steel?
  A: S275 typically offers 370–530 MPa tensile strength, depending on thickness.
• Q: What are the chemical composition limits for these grades?
  A: The main variations involve carbon and manganese: S235 (lowest), S355 (highest), reflecting their strength differences.
• Q: What are the ASTM, JIS, and GB equivalents for S355?
  A: ASTM A572 Grade 50, JIS SM490, and GB Q345B.
• Q: What are the differences between S275 and S355?
  A: S355 has higher yield/tensile strength, better impact resistance, and is suitable for heavy-duty or cold-environment applications.
• Q: Are S235, S275, and S355 weldable?
  A: Yes. All three grades are weldable; S235 is generally easiest to fabricate.

Conclusion

When choosing between S235 vs S275 vs S355, the best grade depends on your project’s strength requirement, budget, and delivery schedule.

• S235 – Economical, easy to fabricate.
• S275 – Balanced performance and cost.
• S355 – Premium grade for demanding structures.

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