Double- and four-row tapered roller bearings with double-sided seals used in hot plate rolling mills use sealing rings and double-lip structures to prevent foreign matter such as iron oxide scale and cooling water from entering the bearings and lubricating grease and leaking. The purpose is to improve the service life of bearings, protect the environment, save energy and reduce consumption.
Keywords: hot plate rolling mill; sealed bearings; energy saving and consumption reduction
Overview
The double- and four-row tapered roller bearings produced are used in rolling mills in various steel rolling mills. The bearings work under harsh working conditions such as impact, high temperature, high speed, heavy load, poor lubrication, and high-pressure water erosion. The end of the bearing box is designed with seals, mainly to prevent external foreign matter from entering the bearing, such as impurities, cooling water, iron oxide scale, etc. When a new seal is first used, the sealing effect is good, but after a period of use, the sealing effect becomes worse. At this time, if the seal is not replaced in time, the sealing effect will be very poor. In addition, frequent assembly and disassembly of bearings will affect the sealing. , foreign matter such as iron oxide scale and cooling water generated during the rolling process will enter the bearing, and the lubricating grease will also leak out. This will cause non-fatigue damage to the bearing, reduce the service life of the bearing, and increase the frequency of workers. The workload of adding grease, as well as the usage and emissions of grease, cause environmental pollution. For these reasons, there is an urgent need to develop a self-sealed bearing.
Sealing structure and characteristics
Taking into account the above reasons, double- and four-row tapered roller bearings with double-sided seals suitable for hot-rolled plate rolling mills have been designed, developed and produced, as shown in Figures 1 and 2.
Figure 1 Schematic diagram of a four-row tapered roller bearing with double-sided seals
Figure 2 Schematic diagram of double-row tapered roller bearings with double-sided seals
As can be seen from Figures 1 and 2, the double-sided sealed bearing adopts a sealing structure with sealing rings on both sides, a contact lip seal with a skeleton, and a built-in compression spring at the inner spacer ring. The lip seal has a double-lip structure, which is divided into main and auxiliary lips. The main lip (see A in the figure) is equipped with a coil spring, which acts on the surface where the outer diameter of the inner ring matches the lip seal with a certain adhesion force. The diameter of the lip and the diameter of the mating surface of the outer diameter of the inner ring adopt an interference fit. The interference amount takes different values according to the inner diameter d of the bearing. The general value range is 300mm＜d＜400mm, GYL (interference amount, the same below)=2.4~4.0mm; 400mm＜d＜600mm, GYL=2.8~ 4.4mm; 600mm＜d＜800mm, GYL=3.1~4.9mm. The outer diameter of the inner ring that matches the lip should be ground by the cutting method to prevent the tiny wear marks left by reciprocating grinding from damaging the sealing lip and affecting the sealing effect. The main lip is mainly to prevent iron oxide scale, cooling water, foreign matter, etc. generated during the rolling process from entering the bearing, causing wear to the bearing or making the rollers and raceways prone to indentation, causing abnormal fatigue damage, that is, Affects the fatigue life of bearings. The diameter of the auxiliary lip (see B in the figure) adopts a loose fit with the diameter of the inner ring mating surface. Generally, it is about 0.5 to 1.0mm based on the inner diameter d of the bearing. The auxiliary lip is mainly used to prevent the leakage of lubricating grease in the bearing. The outer diameter of the lip seal matches the inner diameter of the bearing seal ring, usually a transition fit, and the seal ring adopts H8 fit. A groove is opened on the outer diameter surface of the sealing ring and equipped with an O-ring sealing ring to prevent cooling water from entering the inside of the bearing from the gap between the bearing box aperture and the bearing outer diameter. On the end face of the sealing ring in the direction of the bearing box end cover, according to the size of the inner and outer diameter of the bearing, carve a wide × deep groove, generally about (1.5~3) mm~(3~5) mm. When the lip seal is installed After sealing the ring, chisel 6 to 8 points on the end face groove to press the lip seal end face to prevent the lip seal from falling off the seal ring due to internal pressure. The seal at the inner spacer ring uses a built-in compression spring. The lip is in contact with the mating surface of the inner ring and an interference fit is used. The interference amount is generally 0.5~1mm. For double- and four-row tapered roller bearings with double-sided seals, due to the sealing ring structure used on both sides, the effective height of the entire bearing is reduced while ensuring that the assembly height of the bearing remains unchanged, that is, when the wall thickness of the ring is not changed. In the case of change, the length of the roller is shortened. According to the radial basic dynamic load rating Cr formula and the basic rated life L10 formula of the rolling bearing:
In the formula: Cr – radial basic dynamic load rating (N) bm – rating coefficient of contemporary commonly used materials and processing quality, this value varies with different bearing types and designs; fc – related to the geometry and manufacturing of bearing parts Coefficients related to accuracy and material; i – number of roller rows in the bearing; Lwe – roller length used in rated load calculation (mm); α – nominal contact angle of the bearing (°); Z – each row Number of rollers in each row of multi-row bearings with the same number of rollers; Dwe – roller diameter used in rated load calculation (mm); L10 – basic rated life (×106r/min); Pr – radial equivalent Dynamic load (N); It can be seen from formula (1) that after the effective length Lwe of the roller is shortened, the Cr value decreases when other parameters remain unchanged. According to formula (2), the Cr value decreases, for the same radial equivalent dynamic load, the theoretically calculated L10 also decreases. Generally, the Cr value of four-row tapered roller bearings with double-sided seals is 6% to 13% lower than that of four-row tapered roller bearings without seals; double-row tapered roller bearings have only two rows of rollers, so after sealing on both sides , reflected in the greater reduction in the length and size of the roller, so the Cr value decreases significantly, generally 15% to 30%. Considering that when double-row bearings are paired with four-row bearings, they are only affected by axial load. Therefore, when designing sealed double-row bearings, the bearing contact angle can be appropriately increased according to the specific operating conditions of the rolling mill to improve the axial load. towards carrying capacity. During the actual use of the bearing, because the bearing adopts a double-sided sealing structure, the working environment of the bearing is greatly improved. Foreign matter such as iron oxide scale, cooling water, and impurities produced during the rolling process cannot enter the bearing, and lubricating grease does not leak. , so that the bearing parts are always in a good oil film lubrication state during operation, so the actual service life is longer than that of unsealed double and four-row tapered roller bearings.
Quality of seals
At present, most domestic manufacturers of seals cannot fully meet the design requirements due to reasons such as materials, processes, and processing equipment. For example, the appearance and size of the seals are unstable, sometimes large and sometimes small, and the seals produced in the same batch The size of the seals varies greatly, the hardness is relatively hard, and the service life is short. It cannot reach more than one year, and some can only be used for one month, etc. These problems still need to be further improved by the seal manufacturers.
Conclusion
Since the successful development of double- and four-row tapered roller bearings with double-sided seals, they have been successively used in hot-rolled plate rolling mills in other steel plants. After one or two years of operation, good results have been achieved, reaching The purpose of energy saving and consumption reduction. We are now ready to continue to promote the use of sealed bearings throughout the metallurgical industry, saving the country a lot of manpower, financial and material resources.
