Preparation Methods and Key Techniques of Oil-Impregnated Bearings

The preparation of oil-impregnated bearings is a systematic engineering project integrating materials science, powder metallurgy technology, and lubrication mechanisms. Its core lies in forming stable pores within a metal matrix through a controllable process path, enabling the long-term storage and release of lubricating oil. Currently, industrially, powder metallurgy is mainly used, supplemented by a series of key processes to ensure the finished product possesses suitable porosity, mechanical strength, and self-lubricating properties.

The first step in preparation is the selection and proportioning of raw material powders. Commonly used base materials include iron powder, copper powder, bronze powder, and various alloy powders. The proportions of main components and additives are determined based on the load-bearing capacity, corrosion resistance, and temperature resistance requirements of the target bearing. To improve formability and sintering density, a small amount of lubricant or binder can be added to the powder to improve the flow and bonding properties between particles.

Then comes the forming stage, where a rigid mold is typically used to press the powder into a blank of the desired shape under high pressure. The pressing pressure needs to be precisely set according to the type of powder and the size of the product to ensure that the blank has a certain initial density and sufficient strength, avoiding damage before handling and sintering. The density distribution at this stage directly affects the final pore structure and mechanical properties, thus requiring strict control of pressure uniformity and orientation.

The formed green body undergoes sintering, a crucial step determining the microstructure and pore structure. Sintering is carried out in a protective atmosphere or vacuum environment, heating to temperatures below the solidus line of the base metal to promote diffusion and metallurgical bonding between powder particles, forming a continuous matrix framework. The sintering temperature and time need to be optimized based on the material system to balance strength enhancement and porosity retention; excessively high temperatures can lead to pore closure, weakening oil storage capacity, while excessively low temperatures result in insufficient strength.

After sintering, pore connectivity and distribution need to be controlled, and dimensional accuracy may be improved through re-pressing or reshaping if necessary. The next step is an oil-impregnation process, using vacuum impregnation or pressure impregnation to infuse a selected grade of lubricating oil into the pore network. The impregnation process must ensure sufficient oil filling and the formation of a stable oil reservoir structure during subsequent cooling or settling stages to achieve continuous oil supply during operation and return to storage during rest.

To improve surface quality and dimensional accuracy, some oil-impregnated bearings require finishing processes, such as face cutting, deburring, or light grinding, to meet assembly requirements. For special applications, surface anti-corrosion treatment or resin sealing can be performed to prevent oil loss and corrosion in humid or contaminated environments.

Overall, the manufacturing method of oil-impregnated bearings involves the organic integration of material selection, high-pressure forming, controlled sintering, oil impregnation, and post-processing. Precise control of the parameters in each process determines the balance between porosity, mechanical strength, and lubrication performance, which is the technical foundation for achieving high-performance, long-life self-lubricating bearings and provides a reliable guarantee for their widespread application in various fields.