EN 10277-5 (EU) and GB/T 8731 (China) regulate free-machining steel round bars, which contain sulfur or lead to improve machinability, with key differences:
Alloying elements: EN 10277-5 includes leaded grades (e.g., 11SMnPb30) and sulfur-only grades (11SMn30), while GB/T 8731 focuses on sulfur-manganese grades (e.g., Y15 with 0.10–0.18% S).
Machinability metrics: Both standards specify chip-breaking properties, but EN 10277-5 uses more stringent testing (e.g., tool wear rates at 100m cutting distance).
Mechanical properties: EN 10277-5 requires 420–560 MPa tensile strength for 11SMn30, while GB/T 8731 Y15 has 390–540 MPa-both lower than non-free-machining steels due to sulfur inclusions.
Applications: EN grades dominate EU automotive fastener production, while GB/T 8731 Y15 is widely used in Chinese electronics for precision screws and nuts.