Keywords: Bearings, roller bearings
The ability to prevent adhesion and form boundary lubrication when the shaft diameter is in direct contact with the bearing bush. The material factors affecting the friction compatibility of the friction pair are as follows:
(1) the degree of difficulty of forming an alloy on the metallurgy of a pair of materials.
(2) affinity between the material and the lubricant.
(3) friction coefficient of a pair of materials in the state of no lubrication.
(4) Microstructure of materials.
(5) thermal conductivity of the material.
(6) the size of the material surface energy and the characteristics of the oxide film.
The ability of a material to allow foreign hard particles in the lubricant to clamp in and prevent scratches and/or abrasive wear. For metallic materials, low hardness and low elastic modulus, clamping is good, and non-metallic materials are not necessarily, such as graphite carbon, elastic modulus is low, but clamping is not good. Plain bearings usually use softer materials and harder materials to form friction pairs, and generally use softer materials to do bearing bushing.
In the process of running in between the shaft diameter and the bearing bush, the ability to reduce the machining error, coaxiality error and surface roughness parameter value of the shaft diameter and the bearing bush, so as to make the contact uniform, thus reducing the friction force and wear rate.
The elastoplastic deformation of the surface compensates the poor initial fit of the sliding friction surface and the flexure of the shaft. The material with low elastic modulus has better compliance.
The resistance of a material to wear. Under specified wear conditions, wear resistance is expressed by the reciprocal of wear rate or wear degree and wear quantity.
The ability of a material to resist fatigue failure under cyclic loading. The strength, hardness, impact strength and microstructure uniformity of the bearing material against fatigue are very important at the operating temperature. Materials with good running-in and clamping-in properties usually have poor fatigue resistance.
The ability of a material to resist corrosion. Lubricating oil will gradually oxidize when used in the atmosphere, producing acidic substances, and most lubricating oil also contains extreme pressure additives, which will corrode bearing materials, therefore, bearing materials need to have corrosion resistance.
- Cavitation corrosion resistance
When the bubbles in the liquid break near the solid surface, the local impact high pressure or local high temperature will result in cavitation wear when the solid moves relative to the liquid. The ability of a material to resist cavitation wear is called cavitation resistance. In general, copper-lead alloys, tin-based bearing alloys, and aluminum-zinc-silicon alloys have good cavitation resistance.
The ability to withstand unidirectional loads without being crushed or size invariant.
- Good dimensional stability
Rolling bearings are precise mechanical parts, whose accuracy is measured in microns. In the long-term storage and use process, changes in the internal structure or stress changes will cause changes in the bearing size, resulting in the loss of accuracy of the bearing. Therefore, in order to ensure the dimensional accuracy of bearings, bearing steel should have good dimensional stability.
The production process of rolling bearings is various and the production cycle is long. Some semi-finished products or finished parts need to be stored for a long time before assembly. Therefore, bearing parts are easy to rust in the production process or in the preservation of finished products, especially in the humid air. Therefore, bearing steel is required to have good rust resistance.
In the production process of rolling bearing, its parts have to go through several cold and hot processing procedures. This requires that bearing steel should have good process performance, such as cold and hot forming performance, cutting, grinding processing performance and heat treatment performance, etc., in order to meet the needs of mass, high efficiency, low cost and high quality production of rolling bearings.
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