The annealing of GCr15 bearing steel ball relies on the spontaneous spheroidization tendency and aggregation growth of the sheet cementite. When the flaky pearlite is heated to Ac1+ (20～30) °C, the cementite begins to dissolve locally. A piece of cementite is broken into a number of fine point cementites, dispersed on the austenite matrix, and the austenite composition is extremely uneven due to low heating temperature and incomplete dissolution of cementite.
In the subsequent slow cooling process, a new fine carbide core is formed with the original fine carbonized material point as the core or a carbon-rich region of the austenite to form a uniform and fine granular carbide. These carbides aggregate and grow during the slow cooling process or during the isothermal process, and are converted into spherical cementite in the state of the lowest energy. The hardness of the GCr15 bearing steel ball after annealing is 179-207HB.
GCr15 bearing steel ball is used to make various bearing rings and rolling elements. For example, making internal combustion engines, electric motors, automobiles, tractors, machine tools, rolling mills, drilling machines, mining machinery, general machinery, and high-speed rotating high-speed mechanical transmission Balls, rollers and ferrules for bearings. In addition to balls and bearing rings, they are sometimes used to make dies and gauges. It has high hardness, uniform structure, good wear resistance and high contact fatigue performance.