From the analysis of the heat treatment method for bearing steel balls, it is found that due to the implementation of waste heat recovery and quenching after forging, the FAG bearing steel balls have not undergone spheroidization annealing to solve the problem, resulting in thick crystals and coexisting strip like structures; In addition, the carbon content in quenched austenite is high, and the water inlet temperature during quenching after forging is too high, which increases the quenching stress of the steel ball.

Analysis shows that the West 120mm steel ball is quenched by water cooling and heat dissipation, with uneven temperature distribution, resulting in high mechanical stress. The surface layer exhibits compressive stress, while the interior is tensile stress. The internal tensile stress is the key reason for the fracture of the workpiece. In addition, the bearing steel ball has strong water quenching cooling ability, and the mylonite mechanism inside the workpiece is thick, with a slightly hard mechanism near the core, which makes the ductility of the workpiece core poor and poses a safety risk of cracking. If the workpiece is not quenched immediately after quenching in manufacturing, the stress after quenching is high and not cleared and released, which may cause the steel ball to crack and damage. Analysis shows that the quenching and cracking of bearing steel balls are closely related to the calcination and heat treatment methods. Improper heating time or temperature control during calcination can lead to overheating or overburning of steel balls, resulting in coarse particles and reduced ductility of the workpiece. On the other hand, the forging shape of the 120mm steel ball management center in the west has decreased, and the cooling rate is also lower. Therefore, the work hardening crystals at this location are thick, leading to cracks and fractures in the steel ball that are prone to occur first towards the central and southern regions.

Bearing steel ball

Based on the above analysis, it is clearly proposed that the following corrective measures should be taken to avoid cracking in the processing process of stainless steel balls:

(1) Increase the calcination ratio, strictly control the casting process, and avoid the bulky central mechanism after forging.

(2) Reducing the water inlet temperature of bearing steel ball quenching and increasing the water outlet temperature can significantly reduce and alleviate the quenching stress of the workpiece.

(3) Before quenching, enhance spheroidization annealing and optimize the mechanism to make the workpiece appear fine fiber like (fine block like) austenite after quenching, avoiding the formation of a thick structure after quenching.

(4) Quench immediately after quenching, remove quenching stress, stabilize the mechanism, and further eliminate safety hazards caused by cracking of the workpiece.

After selecting the improved processing technology, the ineffective quenching and cracking of the bearing steel ball were eliminated, and the quality of the workpiece was high-quality after quenching and tempering treatment, resulting in excellent manufacturing operation.