Mechanical "guardians" in extreme environments
What are low-temperature bearings?
(I) Definition Analysis
Low-temperature bearings are not simply the same as high-temperature bearings and can operate stably in high-temperature environments. They refer to bearings that use special materials and structural designs to reduce the friction coefficient, thereby reducing frictional heat, so that the bearings can still maintain low temperatures during long-term operation. Generally speaking, bearings with operating temperatures below -60°C are defined as low-temperature bearings. Its operating temperature reflects the material process and processing level of the bearing processing, mainly based on the temperature difference between the outer ring of the bearing and the injected cooling oil during operation. Lower operating temperatures mean longer bearing life and higher performance.
(II) Working Principle
Cryogenic bearings can work normally in low temperature environments, mainly due to their special materials and structural design. From the perspective of materials, they are commonly made of stainless steel bearing steel 9Cr18 and 9Cr18Mo. Under extremely low temperature conditions (limit temperature - 253℃), 6Cr14Mo materials can be selected, but they must be used in a vacuum environment. Beryllium bronze, ceramics and other materials will also be selected. These materials can still maintain high hardness and toughness at low temperatures to avoid brittle fracture.
Characteristics of cryogenic bearings
(I) Excellent low temperature resistance
Ordinary bearings are prone to material embrittlement and lubrication failure in low temperature environments due to changes in the physical properties of the materials, which can cause the bearings to fail to work properly. However, cryogenic bearings can operate stably at -55℃ or even lower temperatures due to their special materials and designs. For example, in ultra-low temperature medium transportation equipment such as liquid nitrogen pumps and liquid hydrogen pumps, the operating temperature can often be as low as -196℃. Ordinary bearings cannot adapt to such extreme low temperatures at all, but cryogenic bearings can easily ensure the normal operation of the equipment and meet the special needs of the ultra-low temperature field.
2) Good wear resistance
Under low temperature conditions, the viscosity of the lubricating oil will increase significantly and the fluidity will deteriorate, which greatly reduces the lubrication effect of the bearing during operation and is prone to wear. In order to meet this challenge, low-temperature bearings use special wear-resistant materials, such as ceramics and beryllium bronze. These materials have high hardness and good wear resistance, and can effectively reduce the degree of wear and extend the service life of the bearing even under poor lubrication conditions. Take the low-temperature bearing made of ceramic material as an example. It has high hardness and strong wear resistance, and can maintain stable performance in low temperature environments, providing reliable guarantee for the long-term stable operation of the equipment.
3) Excellent corrosion resistance
In low-temperature environments, certain liquids may corrode bearing materials, thereby affecting the performance and life of the bearings. Therefore, low-temperature bearings pay great attention to corrosion resistance in material selection. For example, commonly used stainless steel bearing steels such as 9Cr18 and 9Cr18Mo have good corrosion resistance and can work normally in low-temperature environments containing corrosive media. In addition, some special coating technologies are also applied to low-temperature bearings to further improve their corrosion resistance. For example, by applying a layer of corrosion-resistant coating on the surface of the bearing, the contact between the bearing and the corrosive medium can be effectively isolated, protecting the bearing from corrosion and ensuring its reliability in harsh environments.
