Whether the rolling bearing is good in grease or oil

Core Tip: Rolling bearings have both rolling and sliding friction. Sliding friction is caused by the deviation of the rolling bearing on the surface curve and the deformation of the bearing under load. Such as between the rolling body and the ring
Rolling bearings have both rolling and sliding friction. Sliding friction is caused by the deviation of the rolling bearing on the surface curve and the deformation of the bearing under load. For example, between the rolling element and the ring, since the ball and the ring are not absolutely rigid bodies, their contact areas always have elastic deformation, theoretically point contact or line contact, but in fact, the working conditions under load always become surface contact. Therefore, contact points having different diameters have different linear velocities to generate sliding friction. Sliding friction is also caused between the rolling bodies and the retainers as well as the retainer and the inner and outer rings for a variety of different reasons. The sliding friction increases with the increase of speed and load. In order to reduce friction, wear, reduce temperature and noise, prevent the rust of the bearing components, properly select the lubricant and use reasonable lubrication method, properly control the amount of lubricant. It is an important issue to improve bearing life.
    1. The basis of oil or grease for rolling bearings:
    The advantages of rolling bearings using lubricating oil lubrication are:
    1) Under certain operating specifications, the starting torque and friction loss of lubricating oil is significantly smaller than that of lubricating grease.
    2) Since the lubricating oil takes away heat in the circulation to cool, the bearing can be brought to a relatively high rotational speed.
    3) It can guarantee a relatively high operating temperature.
    4) When changing the grease, the relevant connecting parts must be disassembled, and when it is lubricated with oil, there is no such trouble.
    5) When the bearing in the reduction gearbox is lubricated with lubricating oil, it is suitable because the oil simultaneously achieves the purpose of lubricating the gear and the bearing at the same time in a splashing manner.
    6) In the bearing, the grease is gradually contaminated by the products worn by the product, the abrasive, the product penetrated from the outside through the sealing device and the product which is aging by itself. If not replaced in time, the bearing will accelerate the wear and tear, and when the liquid lubricant is applied, Filtered to keep it running.
    Advantages of grease lubrication for rolling bearings:
    1) Individual bearing points must be refueled by hand. If the grease is used, it will save trouble and avoid accidents caused by lack of oil.
    2) The grease itself has a sealing effect, which allows the use of a mechanism with a low degree of sealing to achieve a simplified design.
    3) Experience has shown that lithium grease lubrication has a lower temperature rise and longer bearing life than a drop method in a certain speed range (n<20000r/min or dn<20000mm.r/min).
    2. Theoretical basis of rolling bearing lubrication: The lubrication mechanism of rolling bearings belongs to the theory of dynamic fluid dynamic lubrication.
    3, rolling bearing failure type and lubrication relationship: most of the failure is due to assembly problems, poor sealing and damage. A small number of failures are caused by wear, gluing, corrosion and overheating due to lack or excess of lubricant or quality failure.

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Rolling mill bearing lubrication method

Core Tips: 1. Lubrication method The lubrication of the roller bearing is basically the same as that of other rolling bearings. However, the working conditions of the roller bearing are relatively bad, and the working performance can be effectively obtained.
First, the lubrication method
    The lubrication of the roller bearings is basically the same as that of other rolling bearings. However, the working conditions of the roller bearings are rather harsh, and whether the working performance can be effectively exerted depends largely on the lubrication of the bearings.
    The lubrication methods used for roll bearings are mainly grease lubrication and oil lubrication.
    The grease-lubricated grease has a sealing function, the sealing structure and the lubrication facility are simple, and the grease is convenient to be replenished, so the roller bearings are generally grease-lubricated as long as the working conditions permit.
    The oil lubrication has a strong cooling effect and can remove dirt and moisture from the bearing. Roller bearings use oil-lubricated lubrication methods such as pressure oil lubrication, fuel injection lubrication, oil mist lubrication and oil and gas lubrication.
    Pressure oil lubrication is the most effective lubrication method for roller bearings at normal speed.
    Injection lubrication is to lubricate the lubricating oil at a certain pressure through the injector mounted on one side of the bearing for lubrication. It is generally used in high-speed roller bearings, or where the pressure supply lubrication cannot meet the cooling requirements.
    Spray lubrication is to spray dry compressed air containing oil mist into the bearing for lubrication. The use of less oil, due to the action of air, the cooling effect is very strong, mainly used for large roll bearings with high rolling speed and high rolling precision. Or for roller bearings that are not often removed in the bearing housing.
    Pressure oil lubrication and fuel injection lubrication require the installation of inlet and outlet pipes, lubrication pumps, oil reservoirs, and sometimes oil coolers. Therefore, the cost is high, and general roller bearings are less used.
Second, the configuration type
    (1), spherical roller bearing
    The configuration of the early rolling mill bearings on the rolling mill was different from the current one. At that time, two sets of spherical roller bearings were mainly installed side by side on the same roll neck. This configuration basically meets the production conditions at that time, and the rolling speed can reach 600 rpm. However, with the increase of speed, its shortcomings become more and more prominent: short bearing life, large consumption, low precision of finished products, severe wear of the roll neck, and large axial turbulence of the rolls.
    (2), four-row cylindrical roller bearing + thrust bearing
     The inner diameter of the cylindrical roller bearing is tightly matched with the roll neck and can withstand radial force. It has the advantages of large load capacity, high limit speed, high precision, separable inner and outer rings, interchangeable, easy processing, low production cost, convenient installation and disassembly, etc. The thrust bearing is subjected to axial force, and the specific structure type can be selected according to the characteristics of the rolling mill.
    Heavy-duty low-speed, with thrust roller bearings, with a small axial clearance to withstand the thrust load. When the rolling speed is high, it is equipped with angular contact ball bearings, which not only has high speed limit, but also can control the axial play during operation. The rolls are tightly axially guided and can withstand typical axial load forces.
    This type of bearing configuration not only has long bearing life, high reliability, but also has many advantages such as high precision and easy control of rolling products. Therefore, it is currently widely used in wire rod mills, sheet mills, foil mills and double support rolls. Support rolls for rolling mill cold rolling mills and hot rolling mills.

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