How the Three Classes Differ
S275JR, S275J0 and S275J2 all specify the same minimum yield strength of 275 MPa at the thinnest section, and the same tensile range, but they are not interchangeable. The quality class controls the Charpy impact test temperature and the permitted phosphorus and sulphur content, and those two factors decide where the steel can be used. JR is tested at +20 °C, J0 at 0 °C and J2 at -20 °C, all with a minimum absorbed energy of 27 J on longitudinal Charpy V-notch specimens to EN ISO 148-1.
| Class | Impact test | P max | S max | C max | Typical use |
|---|---|---|---|---|---|
| S275JR | +20 °C, 27 J | 0.035% | 0.035% | 0.21% | General building frames |
| S275J0 | 0 °C, 27 J | 0.030% | 0.030% | 0.18% | Unheated structures |
| S275J2 | -20 °C, 27 J | 0.025% | 0.025% | 0.18% | Cold climate and dynamic loads |
Manganese is limited to 1.50% maximum in all three classes. Because the tighter classes restrict carbon as well, they also reduce the risk of hard heat affected zones during welding, which is a practical benefit on heavily restrained joints.
Mechanical Properties
| Thickness (mm) | Min yield (MPa) | Tensile (MPa) |
|---|---|---|
| up to 16 | 275 | 410-560 |
| over 16 to 40 | 265 | 410-560 |
| over 40 to 63 | 255 | 410-560 |
| over 63 to 80 | 245 | 410-560 |
| over 80 to 100 | 235 | 400-540 |
| over 100 to 150 | 225 | 400-540 |
The thickness dependency means that a heavy flange can have a yield strength one class lower than the nominal value, and this must be taken into account when the section is selected from the design tables.
Section Designation and Geometry
The W prefix used for wide flange beams originates in the American section naming system, where W shapes are doubly symmetric I sections with parallel flange faces, and HP, S and M shapes cover other I section families. In European practice the same geometry is described as an H beam, and the HE and IPE families are listed in EN 10365. Domestic hot rolled H sections and split T sections are covered by GB/T 11263. In all three systems the flange carries most of the bending moment while the web carries most of the shear force, which is what makes the I section efficient in the web plane and comparatively weak in torsion, where a closed hollow section is preferable.
Beams are rolled in depths from about 100 mm to 900 mm for the heavier wide flange families, with the lightest sections starting around 17 kg/m and heavy sections exceeding 200 kg/m. Delivery lengths are normally 6 m to 12 m, with cut to length service available.
Tolerances, Marking and Certification
Hot rolled I and H sections are supplied to EN 10034 tolerances unless another standard is agreed in the order. The tolerances cover depth, flange width, flange and web thickness, out-of-square, straightness and length. Because the three quality classes carry different impact requirements, the heat number marked on each beam must be traceable to the certificate, which is issued to EN 10204 type 3.1 as standard. Where a design code requires it, an additional ultrasonic or visual examination of the rolled product can be specified.
Additional operations that can be carried out before dispatch include cutting to a fabrication plan, drilling or punching holes, coping and shot blasting to a specified surface preparation grade for painting.
Frequently Asked Questions
Q: Which S275 class should be specified for an outdoor structure in a cold region?
A: S275J2, because the Charpy test temperature is -20 °C with 27 J minimum. JR, tested at +20 °C, does not demonstrate toughness at low service temperature.
Q: Is S275JR stronger than S235JR?
A: Yes. S275JR specifies 275 MPa minimum yield strength against 235 MPa for S235JR, with a tensile range of 410-560 MPa against 360-510 MPa. Both are tested at +20 °C with 27 J minimum.
Q: What does the W prefix mean in a beam designation?
A: It denotes a wide flange beam with parallel flange faces in the American naming system. In European practice the same section is called an H beam and is listed in the HE and IPE families of EN 10365.
Q: Can these beams be used as columns as well as beams?
A: Yes. I and H sections are used both as beams and as columns, either on their own or acting compositely with concrete. Where the section is used as a column, buckling about the weak axis normally governs the size.
Q: How is traceability maintained after cutting to length?
A: The grade and heat number are marked on the section and transferred to each cut piece during fabrication, and the certificate issued to EN 10204 type 3.1 links the heat number to its chemical and mechanical results.