Q345B and Q355B are low-alloy, high-strength structural steels widely used for H-Beams in construction, bridges, heavy machinery, and industrial structures.
Q355B is a newer grade under GB/T1591-2018, equivalent to Q345B from GB/T1591-2008, and also comparable to S355JR in EN 10025-2:2004.
Chemical Composition Comparison (%)
| Material | C max | Si max | Mn max | P max | S max | Cr max | Ni max | Cu max | N max | Nb max | V max | Ti max | Mo max |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Q345B | 0.20 | 0.50 | 1.70 | 0.035 | 0.035 | 0.30 | 0.50 | 0.30 | 0.012 | 0.07 | 0.15 | 0.20 | 0.10 |
| Q355B | 0.20 | 0.55 | 1.60 | 0.030 | 0.030 | 0.30 | 0.30 | 0.40 | 0.012 | - | - | - | - |
Mechanical Properties Comparison
Yield Strength (MPa) by Thickness
| Thickness (mm) | Q345B | Q355B |
|---|---|---|
| ≤16 | ≥345 | ≥355 |
| 16–40 | ≥335 | ≥345 |
| 40–63 | ≥325 | ≥335 |
| 63–80 | ≥315 | ≥325 |
| 80–100 | ≥305 | ≥315 |
| 100–150 | ≥285 | ≥295 |
| 150–200 | ≥275 | ≥285 |
| 200–250 | ≥265 | ≥275 |
| 250–400 | - | - |
Tensile Strength (MPa) by Thickness
| Thickness (mm) | Q345B | Q355B |
|---|---|---|
| ≤40 | 470–630 | 470–630 |
| 40–63 | 470–630 | 470–630 |
| 63–80 | 470–630 | 470–630 |
| 80–100 | 470–630 | 470–630 |
| 100–150 | 450–600 | 450–600 |
| 150–250 | 450–600 | 450–600 |
| 250–400 | - | - |
Applications
Q345B and Q355B H-Beams are used in:
Industrial and commercial building structures
Bridges and highway construction
Heavy machinery and equipment frames
Steel structures requiring high strength and durability
Gnee Steel supplies both Q345B and Q355B H-Beams with custom sizes and further processing services. Inquiries for Q345B or Q355B H-Beam pricing are welcome.
