Terms and definitions
The terms and definitions defined in GB/T308.2 and the following are applicable to this document.
1.1 Crushing load ratio
The ratio of the crushing load value of silicon nitride balls to the standard crushing load value of GCr15 steel balls of the same specification.
1.2 Preprocessed ball
Untreated silicon nitride balls after sintering.
1.3 Fine ball
Silicon nitride balls with certain dimensional accuracy after processing.
1.4 Inclusion
Silicon nitride spheres exhibit locally uneven regions in their phase and microstructure.
Grade
2.1 Material grade
Silicon balls are classified into three levels based on their bending strength, hardness, fracture toughness, crushing load ratio, and microstructure: Level I, Level II, and Level III.
2.2 Accuracy level
Silicon nitride balls are classified into G3, G5, G10, G16, G20, G24, G28, G40, G60, and G100 levels based on appearance, specifications, ball diameter variation, batch diameter variation, spherical error, and surface roughness, with precision ranging from high to low.
Technical Requirements
3.1 Appearance quality
The appearance of the ball should be observed without defects under a 20x stereomicroscope. For appearance issues such as uneven surface color, snowflake marks, and cracks, they should be determined through negotiation between the supply and demand parties.
3.2 Performance
The performance indicators of silicon nitride balls should comply with the requirements of national GB/T 31703-2025.
The maximum allowable density standard deviation for batches of silicon nitride balls of different grades should meet the requirements of the bearing industry.
3.3 Shape error and surface roughness
The diameter variation, spherical error, and surface roughness of silicon nitride balls with different precision levels should comply with the requirements of GB/T 31703-2025.
GB/T 31703-2025 Ceramic Ball Bearings(Zro2) Silicon Nitride Ball Bearings(Si3N4)
