Heat treatment process and improvement measures of solid bearing steel ball

- May 18, 2019-

The solid bearing steel ball is analyzed from the heat treatment process. Since the residual bearing steel ball is not subjected to spheroidizing annealing treatment after the forging, the crystal grains are coarse and have a band structure, and the carbon content in the quenched martensite is high. The temperature of the water entering the quenching after forging is high, which increases the quenching stress of the steel ball.

The solid bearing steel ball is quenched by water, the temperature distribution is very uneven, and the high structural stress is formed. The surface is in the state of compressive stress, the internal is the tensile stress, and the internal tensile stress is the main cause of the fracture of the workpiece.

The solid bearing steel ball has strong water quenching 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. If the heating time or temperature of the forging is improperly controlled, the steel ball is overheated or over-fired, so the crystal grains are coarse and the toughness of the workpiece is lowered. On the other hand, the forging deformation of the central part of the west 120mm steel ball is small, and the cooling rate is also small. Therefore, the recrystallized grains in this part are coarse, and the cracking of the steel ball is most likely to occur first in the middle.

The technical improvement measures of the solid bearing steel ball are as follows

(1) Forging. Increase the forging ratio, strictly control the forging process, and prevent the core structure after forging from being coarse.

(2) 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.

(3) Add spheroidizing annealing before quenching, refine the structure, and make the workpiece quenched into fine needle-like (small sheet) 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.www.wxjnsteelball.com