The mechanical properties of S275JR are its defining characteristics, and they are explicitly thickness-dependent. As the thickness of the rolled product increases, achieving the same yield strength throughout the cross-section becomes more challenging due to differences in cooling rates between the surface and core. Consequently, the guaranteed minimum values decrease for thicker material. The key properties are: Yield Strength (ReH): This is the stress at which the material begins to deform plastically (permanently). It is the primary parameter for structural design under load. Tensile Strength (Rm): The maximum stress the material can withstand while being stretched before necking and fracture. Elongation at Fracture (A): A measure of ductility, expressed as the percentage of permanent elongation of a gauge length after fracture. Impact Toughness (KV): The energy absorbed during a fracture, measured in Joules via the Charpy V-notch test at +20°C for S275JR. The following table summarizes these properties according to EN 10025-2 for nominal product thickness (t):
| Nominal Thickness (t) in mm | Yield Strength (ReH) min. (MPa) | Tensile Strength (Rm) (MPa) | Min. Elongation (A) % (based on gauge length 5.65√So) | Impact Test Temperature | Min. Avg. Impact Energy (KV) |
|---|---|---|---|---|---|
| t ≤ 16 | 275 | 410 - 560 | 23 | +20 °C | 27 J |
| 16 < t ≤ 40 | 265 | 410 - 560 | 23 | +20 °C | 27 J |
| 40 < t ≤ 63 | 255 | 410 - 560 | 22 | +20 °C | 27 J |
| 63 < t ≤ 80 | 245 | 410 - 560 | 21 | +20 °C | 27 J |
| 80 < t ≤ 100 | 235 | 410 - 560 | 20 | +20 °C | 27 J |
Note: For angles, the thickness 't' refers to the leg thickness.
Important Nuances: 1) The tensile strength range (410-560 MPa) is relatively broad, allowing for normal production variations. 2) The impact energy of 27J is a minimum average from three specimens; a single value can be lower (but not less than 70% of the average, or 20J). 3) For design purposes, engineers use a characteristic yield strength (fy) and ultimate tensile strength (fu), which are typically the minimum specified values with partial safety factors applied as per Eurocode 3. This thickness-dependent property guarantee is why specifying the correct grade and understanding the design thickness is critical for structural integrity.