S275JR and S355JR are the two most frequently specified EN 10025-2 non-alloy structural grades, and on many drawings they appear interchangeable because both are hot rolled, weldable and readily available as plate. The decisive difference is strength: 275 MPa against 355 MPa minimum yield for thickness up to 16 mm. This comparison sets out the chemistry behind that gap, the thickness-based mechanical property tables, typical applications and the practical factors that decide which grade a project should carry.
What S275JR and S355JR Have in Common
Both grades are specified in EN 10025-2, the European technical delivery standard for hot-rolled non-alloy structural steels. The designation decodes identically: S for structural steel, 275 or 355 for the minimum yield strength in MPa at 16 mm thickness, and JR for the quality class that guarantees a Charpy V-notch impact energy of at least 27 J at +20 C. Both are available as-rolled (+AR), normalized (+N) or thermomechanically rolled (+M), both weld with ordinary consumables, and neither is a quenched and tempered product, so their strength comes from grade selection rather than heat treatment.
Chemical Composition Compared
Both are low-carbon steels, and the difference between them is small. Maximum ladle analysis limits under EN 10025-2 for thickness up to 40 mm are shown below.
| Element, % max | S275JR | S355JR |
|---|---|---|
| C | 0.21 | 0.24 |
| Si | 0.55 | 0.55 |
| Mn | 1.50 | 1.60 |
| P | 0.035 | 0.035 |
| S | 0.035 | 0.035 |
| N | 0.012 | 0.012 |
| Cu | 0.55 | 0.55 |
S355JR is therefore permitted only marginally more carbon and manganese, and the strength increase is obtained mainly through controlled rolling and accelerated cooling. Because carbon is what drives both strength and hardness, the higher ceiling of S355JR also means a lower ductility margin and a greater sensitivity to welding heat input, so a qualified welding procedure becomes more important as plate thickness grows. The J0 and J2 subgrades of both families tighten phosphorus and sulfur further, to 0.030% and 0.025% respectively, which is why they are selected for cold or impact-loaded service.
Mechanical Properties Side by Side
Yield strength is quoted per thickness range because heavier plate cools more slowly and produces a coarser microstructure.
| Thickness range (mm) | S275JR min yield (MPa) | S355JR min yield (MPa) |
|---|---|---|
| up to 16 | 275 | 355 |
| over 16 to 40 | 265 | 345 |
| over 40 to 63 | 255 | 335 |
| over 63 to 80 | 245 | 325 |
| over 80 to 100 | 235 | 315 |
| over 100 to 150 | 225 | 295 |
| over 150 to 200 | 215 | 285 |
| over 200 to 250 | 205 | 275 |
Tensile strength: S275JR is supplied at 410-560 MPa, S355JR at 470-630 MPa, both depending on thickness.
Impact toughness: both grades are JR quality, tested at +20 C with a minimum absorbed energy of 27 J. Neither is suitable for guaranteed low-temperature service.
Ductility: both are highly ductile because of their low carbon content, but S275JR retains a slightly larger elongation margin, which helps in cold bending and severe forming.
Because S355JR delivers about 29% more yield strength at the same thickness, a designer can usually reduce plate thickness and still meet the load case, cutting steel weight, weld volume and transport cost. The trade-off is a higher price per tonne and, in thick sections, more demanding fabrication controls.
Typical Applications
S275JR: residential and commercial building frames, warehouse and workshop structures, small to medium bridges, columns, beams and trusses in low to medium load service, and general fabrication where cost is the leading concern.
S355JR: high-rise building frames, large and railway bridges, industrial plants, offshore and port structures, crane booms, heavy machinery frames, and other structural supports that must resist substantial static and dynamic loads.
How to Choose Between the Two Grades
Load level: high stress and heavy load cases point to S355JR; moderate loads are normally served economically by S275JR.
Cost: S275JR is generally the cheaper plate, so it wins when the strength surplus of S355JR would be wasted.
Thickness: check the yield table at the actual design thickness, since the permitted minimum falls with plate thickness in both grades.
Fabrication: both weld easily, but S275JR tolerates easier forming and bending because of its slightly higher ductility.
Service temperature: for cold climates or impact-loaded details, move to S275J0, S275J2, S355J0 or S355J2 rather than relying on a JR grade.
The correct choice is therefore a design decision driven by stress level, weight limits, fabrication route and temperature, not simply by price. Referring to the EN 10025-2 property tables for the finished thickness, and stating the subgrade explicitly on the purchase order, keeps the delivered plate aligned with the structural calculation.
Frequently Asked Questions
Q: Is S355JR stronger than S275JR?
Yes. Minimum yield strength is 355 MPa against 275 MPa for plate up to 16 mm, roughly 29% higher.
Q: What does the JR suffix mean in both grades?
JR is the quality class tested for at least 27 J Charpy V-notch impact energy at +20 C, the lowest toughness class in each family.
Q: Are S275JR and S355JR both weldable?
Yes, both are low-carbon non-alloy steels that weld with standard processes, although thick S355JR sections call for a qualified procedure.
Q: What is the equivalent of S275JR?
ASTM A36, GB/T 700 Q235B and JIS SS400 sit close to S275JR in strength, subject to project-specific impact requirements.
Q: Which grade should be used below freezing?
Neither JR grade. Specify J0 for 0 C service or J2 for -20 C service, which also carry tighter phosphorus and sulfur limits.
Q: Can the choice be reversed to save cost?
Only after rechecking the structural calculation, because substituting S275JR for S355JR reduces load capacity unless thickness is increased.
