In order to make the FAG bearing parts quenched and tempered, the surface has a large compressive stress, and a carburizing or nitriding atmosphere may be introduced during quenching heating to perform surface carburizing or nitriding for a short time. Since the actual austenite carbon content is not high when the steel is quenched and heated, it is much lower than the equilibrium concentration shown on the phase diagram, so carbon (or nitrogen) can be absorbed. When austenite contains higher carbon or nitrogen, its Ms decreases, and the martensite transformation occurs in the surface layer after quenching than in the inner layer and the core, resulting in a large residual compressive stress. After the GCrl5 steel was heated and quenched by carburizing atmosphere and non-carburizing atmosphere (both low temperature tempering), the contact fatigue test showed that the surface carburizing life was 1.5 times higher than that of non-carburizing. The reason is that the surface of the carburized part has a large residual compressive stress.
The main material factors and control factors affecting the service life of high carbon chromium steel needle roller bearing parts are:
The carbides in the original structure of the steel before quenching are required to be fine and diffuse. High temperature austenitizing at 630 ° C, or 420 ° C high temperature, can also be achieved by wrought waste heat rapid annealing process.
After quenching the GCr15 steel, it is required to obtain a microstructure of cryptocrystalline martensite having an average carbon content of about 0.55%, about 9% of Ar, and about 7% of undissolved carbide in a round state. The quenching heating temperature and time can be utilized to control the microstructure.
After the parts are quenched at low temperature and tempered, a large compressive stress remains on the surface, which contributes to the improvement of fatigue resistance. A treatment process of surface carburizing or nitriding for a short time during quenching heating may be employed, so that a large compressive stress remains on the surface.
Steel for the manufacture of needle bearing parts requires high purity, mainly to reduce the content of O2, N2, P, oxides and phosphides. Electroslag remelting, vacuum smelting and other technical measures can be used to make the material oxygen content ≤ 15PPM.
1. Immersion method: FAG bearings are immersed in anti-rust grease, so that the surface is adhered with a layer of anti-rust grease. The oil film thickness can be achieved by controlling the temperature or viscosity of the rust preventive grease.
2. Brushing method: It is used for needle roller bearings or special-shaped bearings that are not suitable for soaking or spraying. When brushing, it is necessary to pay attention not to produce anti-rust oil accumulation, but also to prevent leakage coating.
3, spray method: some large bearings can not be immersed oil, generally with a pressure of about 0.7Mpa filtered compressed air in the air cleaning place for spraying. The spray method is suitable for solvent-diluted anti-rust oil or thin-layer anti-rust oil, but it must adopt perfect fire and labor protection measures.
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