25# round steel (GB/T 699) is a low-carbon steel with a balanced composition: 0.22–0.30% carbon (C), 0.17–0.37% silicon (Si), 0.50–0.80% manganese (Mn), ≤0.035% phosphorus (P), ≤0.035% sulfur (S). This moderate carbon content provides a good balance of machinability and strength, making it ideal for general machining parts like bolts, nuts, and shafts that don't require high load-bearing capacity.
Its international equivalents include AISI 1025 (USA), DIN C25 (Germany), and JIS S25C (Japan), all of which share similar machining properties. 25# has a tensile strength of 450–600 MPa and elongation of ≥23%, allowing for easy cutting, drilling, and threading. Made-in-China listings often feature it as "25# Carbon Steel Round Bar for General Machining," valued for its cost-effectiveness in non-critical mechanical components.