The main causes of corrosion are as follows:
1. In the process of producing NTN bearings, some enterprises did not strictly follow the Of Corrosion requirements of cleaning and antirust procedures and oil seal antirust packaging to carry out antirust treatment on the parts of NTN bearings in the process and the finished products of NTN bearings after assembly.
For example, the turnover time of the ferrule in the turnover process is too long, and the outer circle of Of Corrosion the outer ring is in contact with corrosive liquid or gas.
2. The quality of antirust Of Corrosion lubricating oil, cleaning kerosene and other products used by some enterprises in production can not meet the requirements of process and technology regulations.
3. As the price of NTN bearing steel fell again and again, the material of NTN bearing steel gradually declined. For example, the content of non-metallic impurities in steel is high (the increase of sulfur content in steel reduces the corrosion resistance of the material itself), metallographic structure deviation, etc.
At present, the sources of NTN bearing steel used by production Of Corrosion enterprises are miscellaneous, and the steel quality is fish dragon mixed beads.
4. The environmental conditions of some enterprises are poor, the content of harmful substances in the air is high, and the turnover site is too small to carry out Of Corrosion effective antirust treatment. In addition, the hot weather and the violation of rust prevention regulations by production workers also exist.
5. Some enterprises’ anti rust paper, nylon paper (bag) and plastic cylinder and other NTN bearing packaging materials do not meet the requirements of anti rust packaging of rolling NTN Of Corrosion bearing oil seal, which is also one of the factors causing corrosion.
6. The turning allowance and grinding allowance of NTN bearing rings in some enterprises are too small, and the oxide scale and Of Corrosion decarburization layer on the outer circle cannot be completely removed is also one of the reasons.
The advantages of using lubricating oil for rolling fag bearings are:
1) Under certain operating Of Corrosion specifications, the starting torque and friction loss of lubricating oil are significantly smaller than that of grease lubrication.
2) As the lubricating oil takes away heat in the circulation and plays a cooling role, it can make the fag bearing reach a relatively high rotation speed.
3) It can ensure relatively high service temperature.
4) When changing grease, relevant connecting parts must be disassembled. When lubricating with oil, there is no such trouble.
5) When the fag bearing in the reduction gearbox is lubricated with lubricating oil, it is very suitable, because the oil can simultaneously lubricate the gear and fag bearing in a splash way.
6) In fag bearings, the lubricating grease is gradually contaminated by the products of product wear, abrasives, products penetrating through the sealing device from the outside and aging itself.
If it is not replaced in time, it will cause accelerated wear of fag bearings. When liquid lubricant is applied, it can be filtered to ensure its normal operation.
Advantages of grease lubrication for rolling fag bearings:
1) Individual fag bearing points must be refueled frequently by hand. If the grease is changed, it will not only save trouble, but also avoid accidents caused by lack of oil.
2) The grease itself has a sealing effect, which allows the mechanism with low sealing degree to be used to simplify the design.
3) Experience has proved that in a certain speed range (n < 20000 R / min or DN < 20000 mm. R / min), lubrication with lithium grease has lower temperature rise and longer service life of fag bearing than oil dropping method.
2. Theoretical basis of rolling fag bearing lubrication: the lubrication mechanism of rolling fag bearing belongs to the theory of elastic fluid hydrodynamic lubrication.
3. Relationship between failure types and lubrication of rolling fag bearings: most failure causes are damage caused by faulty assembly and poor sealing. A few failures are caused by wear, gluing, corrosion and overheating caused by lack or excess of lubricant or unqualified quality.
4. Basic characteristics of lubricating grease and general criteria for selecting lubricating grease:
When selecting lubricating grease, it is necessary to select the lubricating grease suitable for the service conditions (temperature, speed, load and environment, etc.), which are related to the basic characteristics of lubricating grease, and the basic characteristics of lubricating grease depend on the type of thickener and base oil.
Sliding friction is caused by the deviation of rolling fag bearing on the surface curve and the deformation of fag bearing under load. For example, between the rolling element and the ring, because the ball and the ring are not absolute rigid bodies, their contact area will always produce elastic deformation.
In theory, it is point contact or line contact, but in fact, it will always become surface contact under load working conditions. Therefore, the contact points with different diameters have different linear velocities, resulting in sliding friction.
Similarly, due to various reasons, sliding friction will also occur between the rolling element and the retainer, as well as between the retainer and the inner and outer rings. The sliding friction increases with the increase of speed and load.
In order to reduce friction, wear, reduce temperature and noise, prevent the parts of fag bearing from rusting, correctly select lubricants and adopt reasonable lubrication methods, and appropriately control the amount of lubricants are important topics to improve the service life of fag bearing.
The above is the comparison of the effect of grease lubrication and oil lubrication in rolling fag bearings. I hope you can have some experience after it appears.