GB/T 18254-2016 governs high-carbon chromium bearing steel round bars (e.g., GCr15, GCr15SiMn) with stringent specifications to ensure reliability in bearings:
Chemical composition: Precise limits for carbon (0.95–1.05% for GCr15) and chromium (1.30–1.65% for GCr15) to promote carbide formation, with strict controls on harmful elements (P ≤0.025%, S ≤0.025%).
Microstructure: Mandates fine, uniform carbide distribution (carbide size ≤3 μm) and pearlite lamella spacing to prevent premature wear.
Mechanical properties: Minimum hardness (61 HRC after heat treatment), tensile strength (≥1500 MPa), and impact toughness (≥20 J at 20°C).
Quality control: 100% ultrasonic testing for bars ≥20mm diameter to detect internal defects, plus inclusion rating (≤2.5 级 for oxides and sulfides) to ensure cleanliness.
The standard aligns with ISO 683-17 and ASTM A295, making GCr15 bars compatible with global bearing manufacturers. Made-in-China listings emphasize GB/T 18254 compliance for "High-Precision Bearing Steel Round Bar."