What Is S355JR Steel?
S355JR is a structural grade steel defined in EN 10025-2, the European standard for hot-rolled non-alloy structural steels. It is a higher-strength companion to grades such as S235JR and S275JR.
The designation works as follows: S means the steel is intended for structural applications; 355 indicates a minimum yield strength of 355 MPa; and JR requires a Charpy V-notch impact energy of at least 27 J at +20 °C. This combination makes S355JR suitable for load-bearing frameworks in buildings, bridges and offshore structures without excessively increasing material weight.
Chemical Composition (Ladle Analysis, EN 10025-2)
S355JR is a low-carbon, non-alloy steel. Manganese and silicon improve mechanical performance and ductility, while small residual amounts of nickel, chromium and copper give a limited degree of corrosion resistance. For harsher environments, protective coatings are advised to prevent rusting.
| Element (max, %) | Value |
|---|---|
| Carbon (C) | 0.24 |
| Silicon (Si) | 0.55 |
| Manganese (Mn) | 1.60 |
| Phosphorus (P) | 0.035 |
| Sulfur (S) | 0.035 |
| Nitrogen (N) | 0.012 |
| Copper (Cu) | 0.55 |
Mechanical Properties by Thickness
The yield and tensile values depend on the nominal thickness. Representative values are shown in the table below.
| Nominal thickness (mm) | Min. yield strength (MPa) | Tensile strength (MPa) |
|---|---|---|
| < 3 | 355 | 510 – 680 |
| ≥ 3 ≤ 16 | 355 | 470 – 630 |
| > 16 ≤ 40 | 345 | 470 – 630 |
| > 40 ≤ 63 | 335 | 470 – 630 |
| > 63 ≤ 80 | 325 | 470 – 630 |
| > 80 ≤ 100 | 315 | 470 – 630 |
| > 100 ≤ 150 | 295 | 450 – 600 |
| > 150 ≤ 200 | 285 | 450 – 600 |
| > 200 ≤ 250 | 275 | 450 – 600 |
| > 250 ≤ 400 | 265 | 450 – 600 |
Elongation is verified on the appropriate gauge length, and the JR impact requirement of 27 J at +20 °C applies to the specified thickness classes.
Weldability and Formability
One of the notable properties of S355JR is its good weldability. Because of its chemical composition it can usually be welded without preheating in ordinary sections, which is beneficial in construction where speed and safety matter. Welding procedures should still follow qualified practice for the thickness and joint type.
The steel also offers good forming behaviour: it can be bent, rolled and cold formed into beams, columns, trusses and other profiles, and its high tensile strength and shaping capability make it a versatile choice for general structural purposes, from simple beams in industrial facilities to complex parts in transport engineering and power production.
Typical Applications
Construction: beams, columns and trusses in buildings, with high load-bearing capacity
Bridges: highway bridges under heavy traffic and pedestrian bridges where impact resistance matters
Offshore structures: oil rigs and wind turbine platforms in harsh environments
Heavy and transport engineering: bulldozer and excavator blades, buckets and frames, cranes, dump trucks and railway wagons
Power engineering: support beams and frames in power plants and transmission towers
While S355JR suits many demanding applications, it is not recommended for environments that require excellent corrosion resistance unless specific protective measures, such as painting or galvanising, are taken.
Frequently Asked Questions
What is S355JR equivalent to? Commonly quoted equivalents with closely matching composition and mechanical properties include Q345B (GB), A572 Gr 50 (ASTM), ST52-3 (former DIN practice) and SM490B (JIS). Equivalence is approximate; acceptance is defined by the governing standard and the mill certificate.
What does JR mean in steel designations? J indicates a Charpy V-notch impact test with 27 J minimum energy. R means room temperature (+20 °C); J0 is 0 °C and J2 is −20 °C.
What is the difference between S355JR and S355J2? The impact test temperature differs: S355JR is tested at +20 °C and S355J2 at −20 °C. S355J2 adapts better to low-temperature service conditions.
Is S355 better than S275? Yes in strength terms. S355JR guarantees 355 MPa minimum yield strength versus 275 MPa for S275JR, allowing lighter sections in strength-limited designs.
What is the difference between S275JR and S355JR? Both are non-alloy structural steels under EN 10025-2. The main difference is strength: S355JR has a minimum yield strength of 355 MPa versus 275 MPa for S275JR.
What is S355 steel used for? Shipbuilding, railway vehicle construction, cranes and excavators, building and piping construction, ventilation systems and pumps.
