S355G2+N and S355G3+N are normalized fine-grain structural steel plates conforming to the European standard EN 10025-4. The designation specifies a minimum yield strength of 355 MPa, with "+N" indicating the Normalized delivery condition. The crucial "G" component identifies them as grades for Low Temperature service, with the suffix number (2 or 3) defining the guaranteed minimum Charpy V-notch impact energy at a specific test temperature. These steels are specified for welded structures operating in cold environments, such as bridges, offshore structures, and storage tanks in temperate to cold climates.
Key Differences:
The primary distinction lies in their low-temperature toughness requirements. S355G2+N is impact tested at -20°C and must guarantee a minimum energy of 27 Joules. S355G3+N is also tested at -20°C but must guarantee a higher minimum energy of 40 Joules. This makes S355G3+N the tougher material at this temperature, providing a greater safety margin against brittle fracture for more critical applications.
To achieve this higher guaranteed toughness at the same test temperature, S355G3+N requires stricter control during steel production. This typically involves a more refined chemical composition with lower levels of impurities (sulfur and phosphorus) and precise micro-alloying to ensure a finer and more uniform grain structure after normalizing. Consequently, the fabrication and welding of S355G3+N may demand slightly more stringent procedures compared to S355G2+N to preserve its superior toughness in the weld heat-affected zone, often necessitating the use of qualified welding consumables and controlled heat input.
Mechnical property for S355G2+N steel plate:
| Thickness (mm) | |||||||
| S355G2+N | ≤ 16 | > 16 ≤ 25 | > 25 ≤ 40 | > 40 ≤ 63 | > 63 ≤ 100 | > 100 | |
| Yield strength (≥Mpa) | 355 | 345 | 345 | 345 | 345 | 345 | |
| ≤ 100 | > 100 | ||||||
| Tensile strength (Mpa) | 470-630 | 470-630 | |||||
Mechnical property for S355G3+N steel plate:
| S355G3+N | Yield Strength mm Min(Mpa) | Tensile Strength mm Min(Mpa) | Elongation Min,% | ||||||
| ≤ 100 | ＞100 | ≤16 | ＞ 16 ≤ 25 | ＞ 25 ≤ 40 | ＞ 40≤ 63 | ＞ 63 ≤ 100 | ＞ 100 ≤ 150 | 22 | |
| 470-630 | – | 355 | 345 | 345 | – | – | – | ||
Chemical composition for S355G2+N steel plate
| Main chemical elements composition of S355G2+N steel plate | ||||||
| C | Si | Mn | P | S | Cr | Mo |
| 0.20 | 0.50 | 0.90-1.65 | 0.035 | 0.030 | 0.30 | 0.10 |
| Ni | Alt min. | Cu | N | Nb | Ti | V |
| 0.50 | 0.020 | 0.35 | 0.015 | 0.060 | 0.030 | 0.12 |
Chemical composition for S355G3+N steel plate
| S355G3+N | The Element Max (%) | |||||||||||||
| C | Si | Mn | P | S | Nb | V | Ti | Al | Cr | Ni | Mo | Cu | N | |
| 0.18 | 0.50 | 0.90-1.65 | 0.030 | 0.025 | 0.060 | 0.12 | 0.030 | 0.020 | 0.30 | 0.50 | 0.10 | 0.35 | 0.015 | |
