Bearing ring precision cold heading technology

The precision cold heading technology is a cold forming method in which a ring-shaped rotary part is extruded and plastically deformed at a normal temperature to obtain a finished part. Precision cold heading allows the size and shape of the workpiece to be as close as possible to the theoretical value of the finished part. The advantages are:

1. Can significantly improve material utilization and processing efficiency. Compared with the traditional turning method, the precision cold heading process can increase the material saving rate by 10% to 15%, thereby achieving the machining of the bearing ring and reducing the processing cost.

2. Can improve the quality of finished products. Due to the rolling method, the metal flow lines inside the part are continuous and complete, the metal grains are relatively uniform and small, and the structure is dense, so the strength of the parts is improved. At the same time, due to the existence of residual surface stress of the finished part, the deformation of the part after heat treatment is small.

3. Can save energy and improve the working environment. Compared with the forging die, the equipment required for precision rolling has a small tonnage, which can significantly reduce the noise during processing, and the energy saving effect is obvious. Compared with turning blanks, it has less noise and dust. When the workpiece is pressed, the wheel rotates the workpiece, and the core roller presses the workpiece under the pushing of the support wheel fixed to the feeding device, thereby achieving the rolling of the workpiece. From the stress state of the workpiece, the conditions for forming are: the horizontal force of the workpiece needs to be balanced with the force applied by the feed direction, which is a necessary condition for stable deformation; the force in the vertical direction of the workpiece needs to be greater than or equal to The pushing force generated by the deformation of the workpiece is a condition for the rolling pressure to continue.

The above two forces are the component forces of the normal force in the horizontal and vertical directions of the circular normal force of the supporting wheel or the core roller and the workpiece. When the feed amount of the support wheel is sufficient to ensure plastic deformation throughout the entire wall thickness of the workpiece, the deformation is effective. Moreover, the feed amount depends on the driving power of the boring wheel, the thrust of the support wheel, the radius of curvature of the boring wheel and the core roller. The amount of feed determines the length of the arc of contact between the support wheel or the core roller and the workpiece, corresponding to the normal deformation force generated by the deformation of the workpiece. The longer the contact curvature, the greater the deformation force. Since the radius of curvature of the inner and outer circles of the boring wheel, the core roller and the workpiece are different, the deformation generated inside and outside the workpiece for each feed is unequal. The deformation of the outer circle of the workpiece is greater than the deformation of the inner circle. As the rolling process progresses, the difference between the inner and outer circular deformations will decrease.

The roundness stick is used to control the cylindricity of the workpiece. During the rolling process of the workpiece, the roundness stick always abuts against the outer circle of the workpiece, retreats as the outer diameter of the workpiece increases, and provides a constant full circle bending moment. The use of the roundness stick can also ensure the smoothness of the workpiece rolling process, effectively reduce the vibration in the expansion, thereby prolonging the life of the mold and the machine tool spindle bearing.