What is the main Chinese delivery standard for round steel?

The primary Chinese standard for hot-rolled round steel is GB/T 702-2016 "Hot-rolled round steel and square steel". It specifies technical requirements for dimensions (diameter tolerance: ±0.3mm for Φ6-Φ10, ±0.4mm for Φ10-Φ30), shape (straightness ≤3mm/m), weight tolerance (±3% for single pieces), chemical composition (e.g., C≤0.22% for Q235B, P/S≤0.035% max), and mechanical properties (tensile strength 375-500MPa for Q235B, elongation ≥26%). For cold-drawn round steel (used for precision parts), the standard is GB/T 905-2015, which enforces stricter tolerances (e.g., ±0.01mm for Φ10 h7 grade) and surface finish (Ra ≤1.6μm). Delivery conditions include "hot-rolled, as-delivered" (for general use) or "normalized/quenched-tempered" (for high-strength grades like 40Cr) to optimize mechanical performance.