ASTM has three core standards governing round bars matching GB/T 702 (GB's hot-rolled round bar standard), covering material, dimensions, and quality:
1. ASTM A36/A36M-22 (Material for Carbon Steel Round Bars)
Equivalent to GB Q235B, specifying:
Strength: 248 MPa yield, 400–545 MPa tensile-aligning with Q235B's properties.
Chemistry: Carbon (max 0.25%), Mn (0.80–1.35%), P/S (max 0.040%)-compatible with Q235B's composition.
Applications: Light structural parts (e.g., fence posts, bracket pins) where Q235B is commonly used.
2. ASTM A572/A572M-22 (Material for HSLA Round Bars)
Equivalent to GB Q355B, covering high-strength low-alloy bars:
Grade 50: 345 MPa yield, 448–586 MPa tensile-matching Q355B's 355 MPa (≤16 mm) and 470–630 MPa.
Chemistry: Carbon (max 0.23%), Mn (1.00–1.65%), P/S (max 0.035%)-nearly identical to Q355B.
3. ASTM A6/A6M-22 (Dimensional Tolerances for Hot-Rolled Bars)
Directly aligns with GB/T 702's size requirements:
| Diameter Range | ASTM A6 Tolerance | GB/T 702 Tolerance | Practical Impact |
|---|---|---|---|
| ≤20 mm | ±0.3 mm | ±0.3 mm | Identical-fits GB fastener holes (e.g., M16 bolts use 20 mm bars). |
| 20–50 mm | ±0.4 mm | ±0.4 mm | Same for shafts (e.g., 30 mm bar fits GB bearing housings). |
| 50–100 mm | ±0.5 mm | ±0.5 mm | No machining needed for structural pins (e.g., 80 mm bar for beam supports). |
ASTM A6 also matches GB/T 702's length tolerance (±50 mm for 6–12 m), ensuring bars fit assembly lines without extra cutting. Together, these standards ensure ASTM round bars integrate seamlessly into GB designs.