Prevention and control measures of bearing material heat treatment deformation

The heat treatment process of steel in bearing manufacturing is extremely important, especially, whether the control measures of material deformation after heat treatment are proper or not, it plays a key role in the post-processing and the product forming. 

1. Reasonable use of cooling methods

The cooling process after quenching is an important factor in affecting material deformation. The cooling capacity of the oil is critical to material deformation. Hot oil quenching has less deformation than cold oil quenching. Generally, the oil temperature is controlled at 100±20℃. The stirring method and speed of the quenching oil affect the material deformation. The faster the cooling rate of metal heat treatment, the more uneven the cooling effect, the greater the stress generated, and the greater the deformation of the die . Therefore, on the premise of ensuring the hardness requirements of the die, the pre-cooling method is used as far as possible, the use of stage cooling quenching can significantly reduce the thermal stress and microstructure stress generated during metal quenching, which is an effective method to reduce the deformation of some complicated workpieces; for some workpieces with complex structures or requirements of high precision, isothermal quenching can greatly reduce deformation.

2. Use of right medium

The oil media is used as far as possible under the premise of ensuring the same hardness requirements. Experiments and practices have proved that the cooling rate of oil media is slower as requirements of no difference in other conditions, while the cooling rate of aqueous media is relatively faster. Compared with oily media, water temperature changes have a greater effect on the cooling characteristics of aqueous media. Compared to aqueous media, the deformation of oily media after quenching is relatively small under the same heat treatment conditions.

3. The reasonable structure of parts 

In the cooling process, the thin part always cools faster and the thick part cools slowly after metal heat treatment. On the premise of meeting actual production needs, the disparity between the thickness of the workpiece should be minimized, and the cross-section of the part should be uniform to reduce the distortion and cracking due to stress concentration in the transition zone; the symmetry between the workpiece structure and the material composition and structure should be maintained as much as possible to reduce distortion caused by uneven cooling; try to avoid workpieces with sharp edges, corners and grooves etc., and fillet transitions at the junctions and steps of workpieces; minimize the structural asymmetry of ribs on the workpiece holes and grooves; For parts with uneven thickness, the reserved processing amount is adopted.