Stainless steel ball crack prevention process improveme […]
Stainless steel ball crack prevention process improvement measures include:
(1) Reducing the quenching water temperature of the bearing steel ball and increasing the water outlet temperature can significantly reduce and alleviate the quenching stress of the workpiece.
(2) Increase the forging ratio and strictly control the forging process to prevent the core structure from being coarse after forging.
(3) Add spheroidizing annealing before quenching, refine the structure, and make the workpiece quenched into fine needle-like (fine-like) martensite to prevent coarse structure after quenching.
(4) Temporing tempering after quenching, eliminating quenching stress, stabilizing the structure, and further removing the hidden danger of cracking of the workpiece.
Since the residual steel is quenched after forging, the bearing steel ball is not subjected to spheroidizing annealing treatment, so the crystal grains are coarse and there is a band structure; at the same time, the carbon content in the quenched martensite is high, and the water entering temperature in the quenching after forging is high, so that The quenching stress of the steel ball increases.
The bearing steel ball has strong water quenching and cooling ability, and the layered structure in the workpiece is coarse, and there is a hard structure near the core, which makes the core toughness of the workpiece poor, and there is a hidden danger of crack cracking.
After quenching, the workpiece is not tempered in time. After quenching, the stress is high and is not eliminated and released, which causes the steel ball to crack and damage. According to the analysis, the quenching and cracking of the bearing steel ball is closely related to the forging and heat treatment process.
Improper heating time or temperature control, causing the steel ball to overheat or overburn, so the grain is coarse and the toughness of the workpiece is reduced.