Steel grade designations serve as critical identifiers for differentiating material properties, chemical composition, and intended applications across various national/standard systems.
Chinese Standards (GB)
Q-Series (e.g., Q235): Example: Q235 = 235 MPa yield strength. Carbon content code, where "20" ≈ 0.20% carbon content, classified as high-quality carbon structural steel.
| Q195 | Q235B | Q345B | #20 | |
|---|---|---|---|---|
| C | ≤0.12 | 0.12~0.20 | ≤0.20 | 0.18~0.23 |
| Mn | 0.25~0.50 | 0.30~0.70 | 1.00~1.60 | 0.30~0.60 |
| Si | ≤0.30 | ≤0.35 | ≤0.55 | 0.15~0.35 |
| P/S | ≤0.045 | ≤0.045 | ≤0.040 | ≤0.035 |
American Standards (ASTM)
A36: General-purpose low-carbon structural steel, ≈ China's Q235.
#20: High-quality machining steel, ≈ China's 20 Steel (GB/T 699).
European Standards (EN)
S235JR: Non-alloy structural steel, ≈China's Q235.
S355J2: Low-alloy high-strength steel, ≈ China's Q345
Steel Grade Applications (GB/ASTM Standards)
Q195 Primary Uses: Wire manufacturing, light-duty supports
Q235 Primary Uses: Rebar, general steel structures
Q345 Primary Uses: Bridges, pressure vessels, heavy machinery
#20 Steel (ASTM)Primary Uses: Shafts, gears, precision mechanical components
