Carbon SteelPipe/Tube
Overview
Q345 hollow square tube is a welded or seamless structural steel tube with a square cross-section, made from Q345 low-alloy high-strength structural steel. It is widely used in construction, infrastructure, machinery, and engineering applications due to its high strength, good toughness, excellent weldability, and cost-effectiveness. Under the updated GB/T 1591-2018 standard, Q345 has been officially replaced by Q355, though Q345 remains widely referenced and used in practice.
Size Range
- 20 × 20,thk1.2 – 2.0
- 25 × 25,thk1.5 – 2.5
- 30 × 30,thk1.5 – 3.0
- 40 × 40,thk1.5 – 4.0
- 50 × 50,thk1.5 – 5.0
- 60 × 60,thk2.0 – 6.0
- 70 × 70,thk2.0 – 6.0
- 80 × 80,thk2.5 – 8.0
- 100 × 100,thk3.0 – 10.0
- 120 × 120,thk4.0 – 12.0
- 150 × 150,thk4.0 – 14.0
- 180 × 180,thk5.0 – 16.0
- 200 × 200,thk5.0 – 16.0
- 250 × 250,thk6.0 – 20.0
- 300 × 300,thk6.0 – 22.0
- 350 × 350,thk8.0 – 25.0
- 400 × 400,thk8.0 – 25.0
Grade Specification
| System | Value |
|---|---|
| 🇨🇳 GB | Q355 (per GB/T 1591-2018) |
| 🇪🇺 EN | S355J2H / S355JOH |
| 🇺🇸 ASTM | A500 Gr. B / A500 Gr. C |
| 🇯🇵 JIS | STKR 400 / STKR 490 |
| 🇷🇺 GOST | 09G2S |
| 🇦🇺 AS | C350 / C450 |
Chemical Composition
| Element | Value |
|---|---|
| C | ≤ 0.20 |
| Si | ≤ 0.55 |
| Mn | 1.00–1.60 |
| P | ≤ 0.045 |
| S | ≤ 0.045 |
| V | 0.02–0.15 |
| Nb | 0.015–0.060 |
| Ti | 0.02–0.20 |
| Alt | — |
| Cr | ≤ 0.30 |
| Ni | ≤ 0.50 |
Mechanical Properties
| productCenter.property | Value |
|---|---|
| Yield Strength (MPa), t ≤ 16 mm | ≥ 345 |
| Yield Strength (MPa), 16 < t ≤ 35 mm | ≥ 325 |
| Yield Strength (MPa), 35 < t ≤ 50 mm | ≥ 295 |
| Tensile Strength (MPa) | 470–630 |
| Elongation (%) | ≥ 21 |
| Impact Energy (J) | — |
Physical Properties
| Property | Unit | Value |
|---|---|---|
| Density (g/cm³) | g/cm³ | 7.85 |
| Melting Point (°C) | °C | ~1490 |
| Modulus of Elasticity (GPa) | GPa | 206 |
| Modulus of Rigidity (GPa) | - | 79.3 |
| Poisson's Ratio | - | 0.30 |
| Coefficient of Thermal Expansion (µm/m·°C, 20–100°C) | ×10⁻⁶/K | 12.0 |
| Thermal Conductivity (W/m·K, 25°C) | W/m·K | 46.0 |
| Specific Heat (J/kg·K) | J/kg·K | 460 |
| Electrical Resistivity (nΩ·m, 25°C) | μΩ·cm | 156 |
Applications
- Construction & Infrastructure
- Industrial Engineering
- Oil & Gas & Energy
- Transportation
- Machinery
- Architectural