1. Overview of bearing development
The development of railway freight vehicle bearings in China is mainly divided into five aspects: the change of bearing structure, bearing material, cage form, lubricating grease and sealing device.
1.1 Bearing structure
In order to reduce the starting resistance and running resistance of the train, increase the traction tonnage of the train, improve the running speed, speed up the vehicle turnover and extend the maintenance period, the sliding bearing was initially installed on the railway freight vehicles in China; Since 1965, China has carried out the test and research work of rolling bearings, and the designed 97826 and 97726 double-row tapered roller bearings without axle box have been put into operation. In 1973, in order to speed up the process of rolling bearings, 197726 bearings were produced. In 2002, 197726 bearings were stopped.
In 1998, the first step of improved design was put forward for 197726 type bearing. The internal micro-geometric dimension, grease and seal of the bearing were improved. The plastic steel cage was adopted, and the bearing model was SKF197726.
In October 1999, China developed the 352226X2-2RZ bearing, which has 20 rollers in each row, one less than the 197726 bearing. The roller plain line adopts logarithmic curve full convexity, the inner ring raceway adopts arc full convexity design, the inner ring large retaining edge adopts inclined retaining edge, and the rubber labyrinth seal is used. In December 2002, the design drawing of 353130X2-2RZ bearing product passed the technical review.
In March 2005, based on the 353130X2-2RZ bearing, the 353130A bearing structure for 25t axle load railway freight vehicles was developed, and the seal seat and inner oil seal were canceled. By changing the structure of the front cover and the rear cover and the rubber parts to form a mixed labyrinth seal device, the existing maintenance system and equipment were adapted.
In order to establish a unified bearing standard on a higher technical platform, and facilitate the manufacturing, maintenance, application and management of bearings in the future, the CTBU150 compact bearing technology of SKF Bearing Company was introduced through many technical exchanges with foreign bearing companies. In 2006, the compact bearing 353130B was developed and became the main type bearing of railway freight vehicles in China. The 353130B bearing cancels the seal seat, and the function of the seal seat is realized by the large retaining edge of the inner ring; LL type sealing device (LL oil seal) is adopted to improve the service life of grease and bearing. Engineering plastic cage is adopted and a special pocket hole is added.
1.2 Bearing material
The bearing ring is always made of G20CrNi2MoA carburized bearing steel, and the roller is made of GCr15 high carbon chromium bearing steel. The smelting method is electroslag remelting or vacuum degassing. Due to the disunity of standards and differences in understanding, in July 2006, the technical requirements for carburized bearing steel and high carbon chromium bearing steel for railway freight vehicle bearings were unified and improved.
1.3 Grease
The bearing grease was originally made of type I lubricating grease for rolling bearings of domestic railway vehicles. Since September 1983, imported RB320 lubricating grease was used on 197726 rolling bearings; Since January 1991, type II grease for rolling bearings of railway vehicles has been used in all types; In March 2003, type IV grease for rolling bearings of railway vehicles was used.
1.4 Application of engineering plastic cage
The bearing cage was initially formed by stamping with 08AlT or B275TZ steel plate. Due to the influence of its structure, material, process and other factors, the steel cage has poor bearing rotation timing, which is easy to cause jamming, shaft cutting and difficult to prevent. The engineering plastic cage has good wear resistance, corrosion resistance, self-lubrication, impact resistance, small quality, low cost, and good emergency safety. Even in the oil-free state, because of the self-lubrication characteristics of the engineering plastic cage, it can maintain the normal operation of the rolling bearing for a period of time. Since January 1998, engineering plastic (commonly known as plastic steel) cages have been used in SKF197726 rolling bearings; Since September 2004, engineering plastic cages have been used for 352226X2-2RZ rolling bearings newly manufactured and overhauled; Since June 2005, engineering plastic cages have been used for 197726 type bearings overhauled; At present, engineering plastic cages are used on the bearings of newly designed railway freight vehicles in China.
1.5 Labyrinth seal replaces contact seal
The contact seal was originally used for bearing seal. Due to the interference fit between the contact seal lip and the seal seat, the bearing operating temperature was too high and the oil seal lip was aged due to friction during rotation. Because of the reduced elasticity, the wear of the oil seal lip is accelerated, and the sealing performance is poor. In January 1997, labyrinth sealing devices were all used on domestic newly built or overhauled railway bearings. Labyrinth seal increases flow resistance and energy consumption when grease or external foreign matter passes through small clearance, long process, multiple curved paths and multiple gas chambers. The sealing structure has small torque, low friction, low temperature rise and stable sealing performance, and has been widely used in railway freight vehicle bearings.
2. Bearing type
3. Rolling bearing model of railway freight vehicle
Double-row tapered roller bearing without axle box (15 types):
25t axle load (9 types): 353130B (C353130) (main type), CTBU150 (SKF ITALY V OR-7030A), 353130A, 353130X2-2RZ, SKF 353130-2RS (SKF TBU150), TBU150 (SKF ITALY V OR-7032), TAROL150/250TVP 808997, AP150, 197730 (old wheel gauge).
21t axle load (5 types): 352226X2-2RZ (TN) (main type), SKF197726 (main type), 197726TN, 197726 (old wheel gauge), AP130.
12t axle load (1 type): 197720 (old wheel gauge).
There are four types of axle box double-row tapered roller bearings: NJ3226X1 (main type), NJP3226X1 (main type), 42726QT (old wheel gauge), 152726QT (old wheel gauge).
4. Basic dimension of bearing
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2023-02-13