((4) Tempering in time after quenching to eliminate the quenching stress, stabilize the structure, and further remove the hidden dangers of cracking of the workpiece. The workpiece is not tempered in time after quenching during the production of the workpiece, and the stress after quenching is very high and has not been eliminated and released, resulting in cracking and damage of the steel ball. The high water inlet temperature increases the quenching stress of the steel ball. On the other hand, the forging deformation at the center of the 120mm steel ball in the west is small, and the cooling rate is also low, so the recrystallized grains in this part are coarse, causing the steel ball to crack and break most easily in the middle. Increase the forging ratio and strictly control the forging process to prevent the heart from becoming coarse after forging.After the above process improvement, the failure of FAG bearing steel ball quenching and cracking is eliminated, the quality of the workpiece after heat treatment is excellent, and the production runs well. In addition, the bearing steel ball has a strong water quenching cooling capacity, and the internal layered structure of the workpiece is coarse, and there is a harder structure near the core, which makes the core of the workpiece poorly tough, and there is a hidden danger of cracking.Analysis believes that the quenching cracking of bearing steel balls is closely related to forging and heat treatment processes.From the analysis of the heat treatment process, due to the waste heat quenching after forging, the FAG bearing steel ball has not been spheroidized and annealed, so the grains are coarse and there is a banded structure; at the same time, the carbon content in the quenched martensite is very high. . (3) Reduce the quenching water temperature of the bearing steel ball and increase the water outlet temperature, which can significantly reduce and ease the quenching stress of the workpiece.. (2) Add spheroidizing annealing before quenching to refine the structure so that the workpiece becomes fine needle-like (flake-like.Improper forging heating time or temperature control will cause the steel ball to overheat or burn, so the crystal grains are coarse Bearing C35 and the toughness of the workpiece decreases. According to analysis, the west 120mm steel ball adopts water-cooling quenching, the temperature distribution is very uneven, forming high structural stress, and its surface is in a state of compressive stress. The internal tensile stress is the main reason for the fracture of the workpiece. Based on the above analysis, the improvement measures for preventing cracking of high carbon martensitic steel balls are proposed as follows: (1) Forging.) martensite after quenching to prevent coarse structure after quenching
