Bearing material is to determine the bearing life and related performance (such as impact resistance, high temperature resistance, etc.) of the key factors. For finished bearings, the main indicators of the material to control the hardness and metallurgical organisation of the two.

Hardness: bearing steel are generally high-carbon, high-chromium materials (such as GCr15), its processing to the finished bearing hardness can reach 60HRC or so, if the hardness is too low, the bearings are easy to wear when in use, while the hardness is too high because of the material brittleness will be increased and easy to fracture in use, so the hardness of the finished bearings is the finished product is one of the key indicators of quality control at the time of leaving the factory.

Metallographic microstructure: bearing in the whole manufacturing process will involve forging and heat treatment processing (and raw materials itself has acceptance requirements), these thermal process if not properly controlled will have serious consequences for the final finished bearings (such as bearing collar fracture, ball cracking, etc.), so at this time the metallographic organisation of the control that has become an important means and methods, through the metallographic organisation of the observation and with the standard diagrams Comparison of the rating method can be achieved on the material organisation of the judgement and control.

Bearing hardness and metallographic microstructure of the measurement method and limit requirements (indicators of compliance) in the relevant national standards have clear provisions, inspection can be based on the relevant requirements for qualified assessment.