When selecting carbon structural steel, Q195, Q235, and Q345 are three common options. Below is a detailed comparison covering chemical composition, mechanical properties, and application scenarios, along with selection guidelines.
1. Key Differences Summary
| Parameter | Q195 | Q235 | Q345 |
|---|---|---|---|
| Standard | GB/T 700-2006 | GB/T 700-2006 | GB/T 1591-2018 |
| Yield Strength | ≥195 MPa | ≥235 MPa | ≥345 MPa |
| Carbon (C) | ≤0.12% | ≤0.22% | ≤0.20% |
| Manganese (Mn) | ≤0.50% | ≤1.40% | ≤1.70% |
| Key Applications | Furniture, wires, light frames | Buildings, bolts, towers | Bridges, ships, pressure vessels |
2. Chemical Composition & Mechanical Properties
Q195
Low carbon (≤0.12%), minimal alloying.
High ductility but low strength (315-430 MPa tensile).
No impact toughness requirement-avoid in cold climates.
Q235
Moderate carbon (≤0.22%), better strength than Q195.
Good weldability but requires parameter control.
Room-temperature impact toughness (suitable for static loads).
Q345
Low-alloy steel (with Nb/V), high strength (470-630 MPa tensile).
Subzero performance: Q345D (-20°C) and Q345E (-40°C) for Arctic use.
Preheating needed for welding (150–200°C to prevent cracks).
3. Application-Based Selection Guide
When to Choose Q195
Best for: Non-load-bearing parts (e.g., decorative panels, nails).
Advantage: Cheapest option (~15% lower cost than Q235).
Avoid: Dynamic loads or temperatures below 0°C.
When to Choose Q235
Best for: General construction (beams, columns), machinery parts.
When to Choose Q345
Best for: Heavy-duty structures (bridges, cranes), extreme environments.
Cost Note: 20–30% pricier than Q235 but allows weight reduction.
4. International Equivalents & Procurement Tips
Q235 ≈ ASTM A36 (U.S.) / EN S235JR (EU)
Q345 ≈ ASTM A572 Gr.50 (U.S.) / EN S355JR (EU)
