Abstract: Through the analysis of the unreasonable use of four-row cylindrical roller bearings for rolling mills, the factors affecting the effective service life of four-row cylindrical roller bearings for rolling mills are discussed, and how to improve the four-row cylindrical roller bearings for rolling mills from practical use and management is explained. Effective service life of roller bearings.
The rolling mill is the key equipment for the production of copper sheets and strips. The four-row cylindrical roller bearing for the rolling mill is an important part of the rolling mill and an important guarantee element for the realization of high-speed and high-precision rolling. Since the 1980s, the rolling mill has used four-row cylindrical roller bearings.
Roller bearings have been widely used in non-ferrous metallurgical enterprises, and there are still many problems in the correct use and management in actual use. Mainly: how to improve the effective life of four-row cylindrical roller bearings for rolling mills, and how to reduce its influence on the accuracy of rolling materials.
This is especially true for newly-built copper plate and strip processing enterprises, small copper plate and strip processing enterprises, and enterprises whose copper plate and strip are rapidly expanding but cannot keep up with various management measures and technical strength.
Due to the relatively weak technical force of these enterprises, the understanding of the four-row cylindrical roller bearings for rolling mills is relatively superficial, and there are many problems in the installation, use and management of four-row cylindrical roller bearings for rolling mills; resulting in short bearing life and rolling products. It is often affected by bearing problems, which greatly affects the reliable operation rate of equipment, equipment maintenance costs, and labor intensity of maintenance personnel.
Therefore, it is more and more urgent to strengthen the correct understanding of the four-row cylindrical roller bearings for rolling mills, and to strengthen the rational use and management of four-row cylindrical roller bearings for rolling mills. According to the summary of actual work experience in copper processing enterprises, there are mainly the following problems in the use and management of four-row cylindrical roller bearings for rolling mills.
① The four-row cylindrical roller bearings for rolling mills are treated the same as ordinary bearings, and there are no special management measures.
2. Grind the outer circle of the inner ring of the bearing at will to destroy the bearing clearance.
③The bearing assembly is brutal and rude, pulls and smashes savagely.
④Irregular lubrication, especially for dry oil lubrication, over-lubrication is serious.
⑤It can be used in random pairing with rolls and bearing housings, and the clearance accuracy will decrease.
⑥ Bearing maintenance is not in place, and the use method is not appropriate.
⑦The newly installed bearing does not have the correct pairing planning and clearance regulations.
⑧The incoming inspection and acceptance of the bearing is unscientific.
⑨ The equipment is overloaded seriously, and the bearing life is reduced.
2 Correct understanding of four-row cylindrical roller bearings for rolling mills
The main types of four-row cylindrical roller bearings for rolling mills are FC type (one inner ring four-row cylindrical roller bearing), FCD type (double inner ring four-row cylindrical roller bearing), FCDP type (double inner ring with flat retaining ring) inner ring four-row cylindrical roller bearing).
The working characteristics of the roll bearing are that the working environment is harsh, the working load is large, the unit pressure is high, the heat generation is large, and the service life is short. Compared with ordinary bearings, it has many different characteristics.
From the application point of view, the roll bearing should have good lubrication and cooling conditions, and the radial dimension should be as small as possible.
The main application conditions for roller bearings to be considered are:
①Rotation speed: Not only the maximum rotation speed should be considered here, but sometimes the slow rotation speed is also a problem, and the slow rotation speed is not easy to form a lubricating oil film;
②The force is large: and the force of the rolling elements in multiple rows is uneven, and sometimes even some columns are not stressed;
③Eccentricity of the inner and outer rings: This is mainly reflected in the bearing clearance, which directly affects the accuracy of the rolled sheet and strip;
④Axial force: For the four-row cylindrical roller bearing for rolling mill, it should be considered separately because it cannot bear the axial force;
⑤ High temperature: This is a factor that may lead to poor lubrication.
From the perspective of bearing manufacturing, the material should have the properties of large bearing capacity, small friction coefficient, impact resistance, and ability to absorb hard particles entering the bearing; etc. will be different; for example, for some grades of fully hardened steel, if the size is too large, it is not so easy to harden.
For some special bearings, higher surface roughness is required, rollers need special shapes, special material formulas, etc. At present, there are still many problems in the manufacture of large bearings by domestic manufacturers, and the roller bearings of important equipment still need to be imported.
From the perspective of roll structure design, whether the bearing configuration is reasonable is the premise of whether the rolling mill can meet the requirements of the rolling material and the normal use of the rolling mill bearings. At present, copper plate and strip processing mills are increasingly developing in the direction of high speed, high load, high precision and high reliability. More and more four-row cylindrical roller bearings are used to match thrust bearings.
This configuration has the following advantages:
①In the case of the same section size, its radial bearing capacity is the largest, that is, for a certain roll body diameter, it can accommodate the largest roll neck diameter;
②The radial load and the axial load are borne by two kinds of bearings respectively, each of which exerts its characteristics and can adapt to higher rolling speed;
③The axial movement is controlled by the thrust bearing alone, which can obtain a smaller axial clearance than the double-row spherical roller bearing and the four-row tapered roller bearing, which is beneficial to the improvement of the accuracy of the plate and strip;
④The bearing accuracy is easy to improve and guarantee, making it more reliable and capable of rolling higher-precision products;
⑤The inner and outer rings of the bearing can be separated, which makes the installation and disassembly of the roller more convenient;
⑥The inner ring of the bearing is tightly matched with the roll neck to avoid the phenomenon of burning the bearing when the inner ring is running;
⑦Easy maintenance and inspection;
⑧The overall cost of bearing use is low.
From the above, due to the working characteristics of the rolling mill, the ordinary cylindrical roller bearing with the same inner diameter is compared with the special bearing for the rolling mill. Features.
According to the provisions of JB/T5389.1-2005, when the bearing parts of rolling mills are made of carburized steel G20Cr2Ni4 and G20Cr2Ni4A that comply with the provisions of GB/T3203-1982, the depth of the carburized layer and the quality of heat treatment shall comply with the provisions of JB/T8881-2001; rolling mill bearings When the parts are made of high carbon chromium steels GCr15 and GCr15SiMn in accordance with the provisions of GB/T18254-2002, the heat treatment quality shall conform to the provisions of JB/T1255-2001.
In addition, according to the working characteristics and environmental factors of the rolling mill, the service life of the rolling mill bearing is generally not specified.
In addition, for high-precision plate and strip rolling mills, in order to ensure the reliability of the accuracy of the roll system, generally when selecting four-row cylindrical roller bearings for rolling mills, there should be a certain allowance for the outer diameter of the inner ring of the bearing. After the inner ring of the bearing is assembled on the roll, it is ground together with the roll to the required size to ensure the correct radial clearance, and a relatively high coaxiality between the inner diameter and the outer circle of the bearing and the roll surface can be obtained, so as to ensure the machining accuracy. Sheet and strip accuracy.