What is a Powder Metallurgy Bearing?

Powder metallurgy bearings are made of metal powder and other anti-friction material powders pressed, sintered, shaped and impregnated with oil. They have a porous structure. After being soaked in hot oil, the pores are filled with lubricating oil. During operation, due to the suction effect of the rotation of the journal and the frictional heat, the metal and oil are heated and expanded, and the oil is squeezed out of the pores, and then the friction surface plays a lubricating role. After the bearing is cooled, the oil is sucked back into the pores.

Powder metallurgy bearings do not need to add lubricating oil for a long time.
The higher the porosity of powder metallurgy bearings, the more oil can be stored, but the more pores, the lower its strength.
This type of bearing is often in a mixed lubrication state, and sometimes it can also form a thin film lubrication. It is often used in situations where it is difficult to add lubricating oil and light loads and low speeds. According to different working conditions, powder metallurgy bearings with different oil contents are selected.

When the oil content is high, it can be used without supplementary lubricating oil and under low load; when the oil content is low, it can be used under heavy load and high speed; graphite-containing powder metallurgy bearings can improve the safety of bearings because graphite itself has lubricity, but its disadvantage is low strength; in the absence of corrosion, it is possible to consider the use of cheap and high-strength iron-based powder metallurgy bearings, but the hardness of the matching journal should be appropriately increased.

Features
Powder metallurgy oil-containing bearings (oil-containing bearings) are a type of porous alloy products with lubricating oil impregnated in the pores. When the shaft rotates, the friction between the shaft and the oil-containing bearing causes the temperature of the oil-containing bearing to rise and pumping action. The lubricating oil seeps out of the friction surface of the inner diameter or outer diameter of the oil-containing bearing, and when the shaft stops rotating. The lubricating oil flows back into the oil-containing bearing. Therefore, the consumption of lubricating oil is very small, and it can be used for a long time without supplying lubricating oil from the outside. It is very suitable for occasions where oil supply is difficult and lubricating oil pollution is avoided.

Oil-containing bearings are widely used in various mechanical equipment such as the motor industry, automobile and motorcycle industry, home appliance industry, digital products, office equipment, power tools, textile machinery, packaging machinery, etc.

Powder metallurgy oil-containing bearings are generally made of raw material powder through processes such as pressing, sintering, shaping, and oil impregnation. Most machines are highly automated. The daily output is relatively large, and most products can be formed in one go, so the larger the batch, the better the production. And if fewer molds are used, hundreds of thousands may be made, and if more are used, more than one million may be made. However, the mold cost is relatively high, so it is not easy to make a small batch, and the time to replace the mold is also long.

Powder metallurgy oil-containing bearings can generally be formed in one go, and basically no cutting is required. The cost is lighter than machining, and there is less material waste, so the price is relatively cheap. It also complies with the national policy of advocating energy conservation, so it is considered to be a technology that will not be outdated.

The matrix of the powder metallurgy oil-containing bearing has been filled with lubricating oil by vacuum impregnation, and due to temperature rise and pump suction during operation, the lubricating oil in it will seep out to the running surface, so it can be used in occasions where no additional lubricating oil is added.

In addition to iron, bronze, high alloy steel and even ceramics as the matrix, modern powder metallurgy bearing materials also use various metal compounds, graphite, plastic and other non-metals as lubricating components.

Standards for powder metallurgy bearings include:
(1) ISO 492-1:2006, which specifies the calculation methods for radial and axial loads and rotation speeds of bearings, and puts forward requirements for radial and axial tolerances, rotation accuracy, roughness, appearance defects, materials and hardness of bearings.
(2) ISO 492-2:2006, which specifies the test methods and performance requirements for bearing components, including radial and axial tests, rotation accuracy tests, rotation torque tests, starting friction performance tests, starting and rotating vibration and noise tests, corrosion resistance tests, etc.
(3) ISO 492-3:2006, which specifies the inspection methods and inspection requirements for bearing components, including appearance inspection, dimensional inspection, rotation inspection, performance inspection and special inspection, etc.
(4) ISO 492-4:2006 specifies the marking and packaging requirements for bearing assemblies, including bearing marking, packaging material requirements, pre- and post-packaging inspections, and packaging methods. These standards cover aspects such as the size, precision, materials, and manufacturing methods of powder metallurgy bearings. These standards help ensure that the quality and performance of powder metallurgy bearings meet industry requirements.

Powder metallurgy bearings are a type of bearing with high precision, high load capacity, and long life, which are very suitable for many industrial fields. However, this type of bearing also has some disadvantages, such as high cost and sensitivity to lubricants. When using powder metallurgy bearings, it is necessary to select and adopt appropriate methods for installation and maintenance.